CA1171398A - Task lighting system - Google Patents
Task lighting systemInfo
- Publication number
- CA1171398A CA1171398A CA000396855A CA396855A CA1171398A CA 1171398 A CA1171398 A CA 1171398A CA 000396855 A CA000396855 A CA 000396855A CA 396855 A CA396855 A CA 396855A CA 1171398 A CA1171398 A CA 1171398A
- Authority
- CA
- Canada
- Prior art keywords
- light
- light source
- pattern
- task
- light transmission
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
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- 238000005286 illumination Methods 0.000 claims description 18
- 239000000463 material Substances 0.000 claims description 9
- 206010056740 Genital discharge Diseases 0.000 abstract 1
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- 240000003380 Passiflora rubra Species 0.000 description 5
- 210000000007 bat wing Anatomy 0.000 description 5
- 230000000694 effects Effects 0.000 description 3
- 230000004907 flux Effects 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- YUBJPYNSGLJZPQ-UHFFFAOYSA-N Dithiopyr Chemical compound CSC(=O)C1=C(C(F)F)N=C(C(F)(F)F)C(C(=O)SC)=C1CC(C)C YUBJPYNSGLJZPQ-UHFFFAOYSA-N 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 229940020445 flector Drugs 0.000 description 1
- 230000004313 glare Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21V14/00—Controlling the distribution of the light emitted by adjustment of elements
- F21V14/08—Controlling the distribution of the light emitted by adjustment of elements by movement of the screens or filters
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
- F21S8/00—Lighting devices intended for fixed installation
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21V9/00—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters
- F21V9/08—Elements for modifying spectral properties, polarisation or intensity of the light emitted, e.g. filters for producing coloured light, e.g. monochromatic; for reducing intensity of light
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2103/00—Elongate light sources, e.g. fluorescent tubes
Abstract
TASK LIGHTING SYSTEM
ABSTRACT OF THE DISCLOSURE
A task lighting system is disclosed including a reflector which supports a light source such as a fluores-cent light tube. An at least translucent, member covers the light source and extends along its entire length. A
variable light transmission pattern is carried by the elongated tube. The light transmission pattern has a density which is directly proportional to the brightness levels of the light source, both longitudinally and circumferentially thereof. The variable light transmission pattern is defined by a plurality of opaque markings and is positionable within the reflector so that the light source has an apparent uniform brightness. The variable light transmission pattern controls veiling reflections which can occur when an observer views a task having a given specularity. The member is movable with respect to the light source to vary the bright-ness of the luminaire.
ABSTRACT OF THE DISCLOSURE
A task lighting system is disclosed including a reflector which supports a light source such as a fluores-cent light tube. An at least translucent, member covers the light source and extends along its entire length. A
variable light transmission pattern is carried by the elongated tube. The light transmission pattern has a density which is directly proportional to the brightness levels of the light source, both longitudinally and circumferentially thereof. The variable light transmission pattern is defined by a plurality of opaque markings and is positionable within the reflector so that the light source has an apparent uniform brightness. The variable light transmission pattern controls veiling reflections which can occur when an observer views a task having a given specularity. The member is movable with respect to the light source to vary the bright-ness of the luminaire.
Description
~17~39~
1 TASK LIGHTING SYSTE~I
B~CKGROUND OF THE INVENTION
The present invention relates to lighting systems and more particularly to a luminaire for illuminating a task 5` supported on a horizontal work surface.
Ileretofore, a wide variety of lighting systems have been proposed for general office and home use~ Certain of these systems have been ~esigned to illuminate tasks which are positioned on a horizontal work surface such as a desk. Such task lighting systems may be mounted over the work area and/or suspended from shelves, bookcases and the like. Depending upon the particular type of task being viewed, the light source may be reflected off the task and seen by the observer. ReElection of the light source is directly related to the specularity of the task. For exam-ple, when the observer is reading or viewing a shiny magazine page, the light source may be seen and glare or "veiling reflections" occur. Task lighting systems or luminaires, while being designed to provide a predetermined or required illumination at the area of the task, should also be de-signed to control the specular brightness of the task to avoid such veiling reflections.
Veiling reflections may be a problem only with cer-tain types of tasks. FOT example, if a light, diffuse paper, such as bond paper, is the task and the user is employing a black felt tip pen, veiling reflections are not a problem.
Various proposals have been made to eliminate or control veiling reflections. Typical prior approaches have reduced the brightness of the light source at the central area thereof. These approaches in effect "place"
the light source out of a defined zone within l~hich the ~7139~3 1 task is expected to be positioned. An example o one such system employs a lens which has a so-called "bat-wing" light distribution pattern. The lens system in effect redirects light to the sides of the work surface and reduces the energy or brightness levels in defined directions in which any task specularly will reflect it to the viewer.
Another approach which has heretofore been employed is to place a baffle such as an opaque plate at the central area of the light source. The baffle prevents transmission of light from an area of the light source to the task. The task is illuminated by side lighting. Veiling reflections are eliminated as long as the task is positioned in a defined zone. ~hould the user move the task to tlle sides of the work surface, veiling reflections will again become a problem with either the "bat-wing" lens or the baffle approach.
The aforementioned prior approaches to eliminating veiling reflections have merely "blocked" the central area of the source and permitted side light to illuminate the task sufficiently for viewing and/or reading purposes.
An example of one prior system may be found in U. S. Patent No. 4,054,793, entitled LIGHTING SYSTE~ and issued on October 18, 1977, to Shemitz. This patent dis-closes a lighti,ng fixture including an elongated housing, a light source and a refractor element which distributes luminous flux from the light source in a bat-wing configur-ation. Another example of a refractor plate which distri-butes luminous flux from the light source in a bat-wing configuration may be found in U. S. Patent No. 3,258,5'30, entitled PLAIES FOR LIGIIT CONTROL and issued on J~me 28, ~7~398 1 1966, to Goodbar.
Other task lighting systems have attempted to control veiling reflections by polarizing the light emanat-ing -from the light source before it strikes the task. r,~hen a polarizing filter material is placed in front of the light source so that it is intercepted by light emanating towards the task~ the light is polarized before it strikes the surface. This polarization~ of course, eliminates one of the components of the light. Upon reflection, the remaining component is also eliminated. This polarizing concept does not block light emanating from the light source. An example of a polarizing system may be found in U. S. Patent No.
3,239,659, entitled GLARF.-REDUCING LAMP and issued on March 8, 1966, to Makas.
In situations where veiling reflections are not a problem because of the task characteristics, the brightness level of the luminaire could desirably be increased. This would increase the illumination which may be wanted by the user. Prior systems have not provided for ready adjust-ability of illumination levels.
A need exists for a luminaire or task lighting system which will control veiling reflections across the entire work surface yet which permits adjustment of illum-ination levels to the particular task being viewed and which accommodates differences in geometric orientation, task position, observer eye position and the height of the luminaire above the task so that the user can maximize the effectiveness of the luminaire.
~UMMARY OF THE INVENTION
In accordance with the present invention, the afore-mentioned needs are substantially fulfilled. Essentially J
~17~3~3 1 the present invention encompasses a task light control mask.
The control mask includes an at least translucent, member adapted to be supported at the light source. A variable light transmission means is carried by the member. The light transmission means controls the apparent brightness of the light source to reduce the brightness contrast across the luminaire and control veiling reflections. Provision is made for adjusting the position of the variable light trans-mission means with respect to the light source so that illumination levels can he controlled and the luminare may be adjusted for the particular task being viewed.
In narrower aspects of the invention, the light source and light mask member are supported within a large area, diffuse reflector. The reflector increases the apparent area of the light source thereby reducing the brightness of the system per square unit of area. As a result, the light which is reflected by the specularity of the task into the eye of the user is less bright. A reduc-tion in the specular brightness of the task is achieved which improves the apparent quality of the viewing situa-tion~
In an existing embodiment, the variable light transmission means is defined by a blocking medium. The medium has a pattern which is essentially configured to match the brightness of the reflector near the lamp and to create an apparently, uniform brightness level for the portion of the luminaire which might be reflected. The pattern reduces high areas of illumination at the work surface by a reduction in light transmission through ~he mask. ~niformity of illumination at the task area is achieved, and veiling reflections are controlled.
1 It is preferred that the member be rotatably adjustable within the reflector with respect to the light source. As a result, the mask pattern may be moved into and out of the area from which light emanates from the light source to the task. This permits adjustment by the user ofthe brightness levels achieved by the luminaire. As a result, adjustment for geometric differences~ eye position differences and height of the unit above the task are readily achieved.
The task lighting system in accordance with the present invention permits the user to control veiling re-flections and obtain an apparent uniform brightness without the use of lenses and/or opaque plates or baffles. This reduces significantly the overall size of the luminaire that would otherwise be necessary to achieve the same results.
This is a sigllificant advantage to the furniture designer since the lighting system is more readily accommodated to specific furniture design/size constraints. Aesthetics are more readily achieved at a reduced cost of manufacture. The luminaire may be integrated or built directly into a cabinet structure. Such integration of lighting systems with sur-rounding furniture has not heretofore been as readily or as easily achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic, side elevation of a lighting system in accordance with the present invention;
Fig. 2 is a perspective, bottom elevational view of the lighting system;
Fig. 3 is a cross-sectional view taken generally along line III-III o-f Fig. 2;
Fig. 4 is a front, elevational view of an elongated 3~3 1 light source and light control mask in accordance with the present invention;
Fig. 5 is a cross-sectional view taken generally along line V-V of Fig. 4;
~ig. 6 is a plan view of a portion of the variable light transmission means incorporated in the present inven-tion;
Fig. 7 is a schematic view showing the dimensions of a quadrant of one embodiment of the variable light trans-mission means of Fig. 6, Fig. 8 is a graph showing the approximate light transmission values across radial sections of the control mask dimensioned on the circumference; and Figo 9 is a graph illustrating the variation in I5 the light transmission values across longitudinal sections of the control mask.
DETAILED DESCRIPTION OF THE PREFERRED EMBODI~ENT
With reference to the drawings, Fig. 1 schem-atically ill~strates a light control system in accordance with the present invention which is primarily adapted for illuminating a task. The system includes a luminaire gen-erally designated 10 which is supported above a generally horizontal work surface 12. Luminaire 10 includes a re-flector generally designated 14, an elongated, linear light source 16 including a control mask 17. In the embodiment shown, source 16 is a fluorescent tube. Luminaire 10 may be suspended from the undersurface of a cabinet, shelf or the like and which is generally designated 18. In the alterna-tive, luminaire 10 could be supported from separate bracket structure in a position above the work surface 12.
Luminaire 10 is primarily adapted to illumina~e a 9~3 1 task 20 which is illustrated in a position on the work surface 12. As shown in Fig. 1, an observer may view the task from a position generally designated 22. The task has leading and trailing edges 24, 26. From the light rays 28, it should be apparent that the task defines a critical brightness zone 30 which is subject to the aforementioned veiling reflections. Light in the zone 30, that is, within the boundaries of the leading and trailing edges 24, 26 of the task, could be reflected to the eye of the observer 22.
It should be understood that as the task is moved both longitudinally and from the front to back of the work surface 12, the critical brightness zone would necessarily shift.
As seen in Figs. 2 and 3, reflector 14 of lumin-aire 10 includes first and second lateral edges 32, 34 and ends 36, 38. In the embodiment illustrated, the light source 16 and light control mask 17 extend between and are supported by ends 36, 38. It is presently preferred that the light source 16 and control mask 17 be supported imme-diately adjacent lateral edge 32. When mounted from a support structure lB, lateral edge 32 would be facing the viewing position generally designated 22. This positioning of the light source is preferred since the elongated tube will be essentially "hidden" from the eye of the observer.
Reflector 14 includes a support OT body 42 to which is secured a diffuse reflector 44 (Fig. 3). Reflector 44 includes a first, angled portion 46 immediately adjacent the elongated linear light source 16. Reflector 44 slopes generally away from the light source 16 along a portion designated 48 As should be apparen~ from the drawings, the reflector is a "large area" reflector which increases the ~7~398 1 apparent area source of the light emanating from the light source 16. This reduces the brightness of the luminaire or system per square unit of area.
In the structure of Figs. 4 and 5, light source 16 is a fluorescent light tube or elongated, linear light source 52. Supported around and substantially encircling the tube 52 is light control mask 17. ~ask 17 includes a generally tubular shaped member 54. ~lember 54 is at least translucent and pre~erably transparent. Tubular member 54 extends throughout the entire length or longitudinal dimen-sion of the fluorescent tube 52. Tube 52 is supported within tubular member 54 by end caps 56. The tubular member 54 is of a conventional configuration which has heretofore been marketed to protect the lamp from accidental breakage.
An example of such a tube may be found in U. S. Patent No.
3,676,401, entitled FLUORESCENT LAMP PROT~CTION APPARATUS
and issued on June 27, 1972, to DuPont. It is presently preferred that the tube be extruded from a clear polycar-bonate material.
As seen in Flgs. 2 and 4, tube or member 54 carries and/or supports a ~ariable light transmission means which is generally designated 64. The variable light transmission means extends throughout the longitudinal dimension of tube 54 and hence the fluorescent tube 52.
Further, -variable light transmission means 64 extends cir-cumferentially of the tube 54. The variable light trans-mission means 64 is defined by a plurality of regularly spaced lines. These lines define a pattern of opaque markings which is symmetrical about a longitudinal axis 66 and about a vertical centerline 68 (Fig. 4).
A fluorescent tube does not produce a uniform 139~3 1 brightness level throughout its length. Typically, such tubes are brighter along their longitudinal centerlines and in a central area intermediate the encls. The brightness levels of SUC]l tubes taper off from their vertical center-lines to their ends. Brightness varies along longitudinal and circumferential dimensions of the tube. This causes nonuniform illumination levels at the work surface. The entire work surface is not fully usable for positioning the task.
The primary purpose of the variable light trans-mission means 64 is to reduce the apparent brightness of the light source in a direction in which it would be reflected by the task. The objective is to match the brightness of the reflector near the lamp to create a uniform or apparent uniform brightness. The variable light transmission means 64 also reduces high areas of illumination, i.e., along the central area of the tube, so that uniformity of lighting at the task area is achieved~
Each end cap 56 has a circular flange portion 72 which is joined to a generally cylindrical hub portion 74.
Hub portion 74 defines a central throughbore which receives the ends of the fluorescent light tube 52. The end caps are pressed into the open ends of elongated tubular member 54.
As a result, tubular member 54 may be rotated relative to the fluorescent tube 52. As explained in detail below, this permits positioning of the variable light transmission means 64 to adjust for illumination levels and geometric dif-ferences encountered in mounting the luminaire with respect to a task. As explained in detail below, the adjustability feature allows the user to maximize the effectiYe illumin-ation of the system and to match such illumination levels to ~71398 1 the particular task which is being viewed.
A portion of the variable light transmission means 64 is illustrated in Fig. 6. As should be readily apparent from Figs. 4 and 6, variable light transmission means 64 is symmetrical about longitudinal axis 66 and about the vertical axis 68. As a result, only one-half of the pattern has been illustrated in detail.
I`~eans 64 includes a plurality of regularly spaced, opaque lines or markings which de-fine a pattern 82 having a varying density or open area. The opaque markings are in effect "overlayed" and define a plurality of zones which have been dimensioned in Fig. 7. The pattern having the dimensions of Fig. 7 was developed for use with an F-40, T-12 fluorescent light tube. ~uch a tube has an overall length of 4 feet, a 12/8 inch diameter and is rated at 40 watts.
The opaque lines, as should be readily apparent, define varying open areas or densities. The open areas or densities vary from the vertical centerline 68 towards the outer ends of the pattern along ~he longitudinal centerline 66. The pattern has more "open area" or is less dense as it approaches the ends than it has adjacent the central area about the vertical centerline 68.
A fluorescent light tube has a greater apparent brightness immediately about and along longitudinal center--line 66. Further, the brightness of the tube is greater about the vertical centerline 68 and hence within a central area of the tube. As discussed above, prior approaches to eliminating veiling reflections have modified the illumin-ation pattern of the fluorescent tube by eliminating light from the central area and redirecting it to the side areas.
~ i 3~ 8 1 Such systems are exemplified by the so-called bat-wing lenses and by the approaches which have positioned an opaque plate or a plurality of ba:Efles immediately adjacent and about the vertical centerline of the tube. These plates, baffles and lenses have eliminated direct light from the central area of the tube to the horizontal surface 12 where task 20 would be positioned. Typically, the task would be supported on the work surface at the central area of the light source. By eliminating the high brightness from the center of the light source, veiling reflections can be reduced since the task is essentially illuminated by side light. Veiling reflections will, however, remain a problem should the user r.love the task towards either end of the light source and away from the area from which direct vertical light transmissian is blocked.
In accordance with the present invention, this problem is eliminated. The variable light transmission means 64 extends throughout the length of the linear light source and creates an apparent uniform brightness from the luminaire. As a result, the user can move the task towards either end of the work surface and veiling reflections will not be a problem. The mask may be adjusted for the particu-lar eye position and geometric arrangement of the luminaire with respect to the work surface.
As mentioned above and as shown in Figs. 6 and 7, means 64 is defined by a plurality of overlayed patterns of opaque lines. Since means 64 is symmetrical about longi-tudinal 66 and vertical 68, only a single quadrant of the pattern for the existing embodiment will be described in detail. The quadrant (Figs. 6 and 7) includes a rectangular pattern bounded by lines a, b and c. Within the boundary ~7i3~8 1 lines a~ b and c are a plurality of vertically extending lines 88. Lines 88 have a height dimension of 1.250 inches (Fig. 7). Lines 88 are equally spaced along the boundary b which has a dimension of 23 inches. Lines 88 are spaced at 0.10 inch intervals along longitudinal 66.
Another pattern of lines is overlayed on lines 88.
This pattern is triangular and is bounded by a side d, a base e and a hypotenuse f. The pattern includes a plurality of equally spaced7 parallel lines 90 which extend -from base e at an angle g of 45 (Fig. 6). Side d has a dimension of 3.125 inches and base e has a dimension of 23 inches. Lines 90 are spaced at 0.10 inch intervals within boundaries d, e and f, Another pattern of parallel lines 92 is formed within boundaries h7 i and j ~Figs. 6 and 7). Lines 92 extend perpendicular to centerline 66 and are spaced from each other at 0.20 inch intervals. Boundaries h and j have a vertical height of 2.50 inches, and line i has a length of 6.00 inches.
Another triangular pattern bounded by a side k, a base 1 and a hypotenuse m is overlayed on the other pat-terns. Boundary k has a dimension of 1.875 inches, and base 1 has a dimension of 18.00 inches. ~ithin boundaries k, 1 and m are a plurality of lines 94. Lines 94 are angled with respect to base 1 at an angle n of 45 and spaced at 0.05 inch intervals (Fig. 6).
A final triangular pattern is bounded by a side a base p and a hypotenuse q. Boundary or side o has a dimension of 0.750 inches, and base p has a dimension of 12 inches. Parallel lines 96 are spaced within boundaries o, p and q. Lines 96 are spaced at 0.05 inch intervals and are 39~3 1 angled with respect to base p at an angle r of 45 (Fig. 6).
~leans 64 includes a final rectangular pattern o~
perpendicularly related lines 98, 100 bounded by sides s, t and e. Boundaries s and t have a dimension of 0.375 inches, and boundary e has a dimension of 23 inches. Lines 98 extend parallel to each other and parallel to longitudinal 66. Lines 100 extend parallel to each other and perpendicu-lar to longitudinal 66. Lines 98 are spaced from each other at 0.050 inch intervals. Lines 100 are spaced from each other at 0.50 inch interwals. The width dimension of each of the lines of all the patterns is approximately 0.050 to 0.055 inches.
The presently existing embodiment of the variable light transmission means 64 described above and illustrated in Fig~ 6 is photo offset printed on a sheet designated 120 in Fig. 6 of clear plastic material. The presently pre-ferred material is polyester. The sheet of clear plastic material having the patterns imprinted thereon is rolled and inserted into the light control mask tube 5~. This is illustrated in Fig. 5. As a result, the sheet of material 120 is carried and supported within tube 54 which therefore carries or supports the opaque markings. In the alterna-tive, the pattern could be imprinted directly on the clear or translucent tube 54. At present, howeverJ the tubes are obtained as seamless extrusions. If imprinted directly on the tubes, the tube could initially be formed as a flat sheet with the pattern imprinted thereon. The sheet would then be rolled to the desired configuration. The pattern might also be silk screened directly on the tube.
The specific pattern of lines illustrated in Fig.
6 for the presently existing embodiment produces light ~7~398 1 transmission values approximated in the graphs of Figs. 8 and 9 when surrounding an F-40, T-12 fluorescent tube. Fig.
8 is a graph showing the llght transmission values (Y ordin-ate) for the mask at radial sections tx ordinate) dimen-sioned on the circum-ference of the mask tube and pattern.
For example, the line designated "3 inch section" shows the variance in the transmission values from the centerline 66 circumferentially or perpendicular thereto along a vertical or circumferential line three inches from vertical 68. This is illustrated in Fig. 4. As shown therein, a line 128 has three data points marked thereon and designated 130, 132 and 134. Line 128 extends perpendicular to longitudinal 66 at a point spaced 3 inches from vertical centerline 68 along the longit-~dinal. Hence it is a three inch section. At the centerline and hence at point 130, the light transmission value is approximately 20%. At point 132, one inch from the centerline along line 28, the light transmission value is approximately 35%. At point 134, two inches ~from the center-line along the circumference, the light transmission value is approximately 60%. ~imilar measurements were made for vertical or circumferential lines spaced from the centerline ~- 68 along longitudinal 66 at 9, 15 and 21 inches. The values obtained were marked on the graph and the lines defining the ; graph were smoothed through the several data points. As a result, the light transmission values obtained from Fig. 8, except at the specific data points, are approximations of the actual values which would be achieved by the mask illus-trated in Fig. 6.
Fig. 9 illustrates the light transmission values along longitudinal sections of the mask taken along a line coincident with the centerline, a line one inch from the ~ 39 ~
1 centerline and extending parallel thereto and a line two inches from ~he centerline and extending parallel thereto.
The line designated "centerline" in Fig. 9 represents the light transmission values for points designated 130, 136, 13~ and 140 in Fig. 4. The data points are respectively at points along or parallel to the longitudinal at 3, 9, 15 and 21 inches from the vertical centerline 68. As shown, the light transmission values along the centerline towards the ends vary from approximately 20% to approximately 25%. The curves illustrated in Fig. 10 are also approximations. For example, the values given for the "2 inch section" represent a "smoothed curve'l for values measured three inches from the centerline, nine inches and fifteen inches from the center-line. The measured values at three and nine inches are plotted on the graph. The value at fifteen inches is 100%
since this point is out of the area of the pattern. The two inch line was then smoothly drawn inbetween these data points.
Dif-ferent line patterns or other transmission control mediums having open areas and/or densities which vary longitudinally and circumferentially of the control mask and which approximate the transmission values given in Figs. 8 and 9 would be in accordance with the present inven-tion. Sucn a light control mask and/or variable transmission means would be able to eliminate veiling reflections by approximating a uniform brightness le~el throughout the length of the fluorescent tube.
OPERATION
The luminaire in açcordance ~ith the preferred embodiment is assembled by inserting the fluorescent tube within the control mask defined by tube 5~ and variable -15~
~:1 7139~3 1 light transmission means 64. End caps 56 rotatably support tube 54 with respect to the light source. The assembly is mounted within reflector ~. The reflector is supported above the horizontal work surface. The narrow vertical height of the luminaire permits the furniture designer to readily integrate the lighting system into the furniture or office system. For example, the luminaire may be secured directly to or in the undersurface of a cabinet suspended from a panel and above a desk or other work area.
The user can rotate tube 54 to position the variable light transmission means. This adjusts the illum-ination levels to the particular task being viewed. Essen-tially uniform illumination can be obtained when the pattern is positioned to block light along the entire length of the fluorescent tube. When so positioned, a task havlng high specularity may be moved around on the work surface without encountering veiling reflections. If a higher illumination level is desired, tube 54 can be rotated to move some of the pattern out of line with rays from the light to the task.
The invention, therefore, provides a full range of adjust-ability. Size and cost restraints heretofore experienced are substantially reduced. Adustment can be made for geo-metric differences in the mounting of the luminaire with respect to t'ne work surface and for eye position differences.
In view of the foregoing description, those of ordinary skill in the art will undoubtedly envision various modifications which would not depart from the inventive concepts disclosed herein. The variable light transmission concept to control brightness could be employed with light sources other than the fluorescent tube shown. Also, the concept might be employed in systems other than task lighting ~713~8 1 systems The specific configuration of the reflector of theluminaire shown could be varied while still obtaining the desired results. A diffuse, large area reflector is pre-ferred, however, in order to increase the apparent area source of light emanating Erom the luminaire. Further, the luminaire including the light control mask and variable transmission means in accordance with the invention would function if the light source were supported adjacent the opposite latera] edge of the reflector from that illus-trated. It is preferred, however, that it be mounted in theposition shown so that it is essentially hidden from the observer when suspended beneath a shelf, cabinet or sup-ported by other bracket structure. Further, as set forth above, the precise pattern of opaque markings employed or the manner of defining the pattern having varying light transmission values could differ from that illustrated.
Other means such as variable density shading or a variable translucency on a sheet of material could be employed to obtain similar results.
Therefore, it is expressly intended that the above description should be considered as only that of the pre-ferred embodiment. The true spirit and scope of the present invention may be determined by reference to the appended claims.
1 TASK LIGHTING SYSTE~I
B~CKGROUND OF THE INVENTION
The present invention relates to lighting systems and more particularly to a luminaire for illuminating a task 5` supported on a horizontal work surface.
Ileretofore, a wide variety of lighting systems have been proposed for general office and home use~ Certain of these systems have been ~esigned to illuminate tasks which are positioned on a horizontal work surface such as a desk. Such task lighting systems may be mounted over the work area and/or suspended from shelves, bookcases and the like. Depending upon the particular type of task being viewed, the light source may be reflected off the task and seen by the observer. ReElection of the light source is directly related to the specularity of the task. For exam-ple, when the observer is reading or viewing a shiny magazine page, the light source may be seen and glare or "veiling reflections" occur. Task lighting systems or luminaires, while being designed to provide a predetermined or required illumination at the area of the task, should also be de-signed to control the specular brightness of the task to avoid such veiling reflections.
Veiling reflections may be a problem only with cer-tain types of tasks. FOT example, if a light, diffuse paper, such as bond paper, is the task and the user is employing a black felt tip pen, veiling reflections are not a problem.
Various proposals have been made to eliminate or control veiling reflections. Typical prior approaches have reduced the brightness of the light source at the central area thereof. These approaches in effect "place"
the light source out of a defined zone within l~hich the ~7139~3 1 task is expected to be positioned. An example o one such system employs a lens which has a so-called "bat-wing" light distribution pattern. The lens system in effect redirects light to the sides of the work surface and reduces the energy or brightness levels in defined directions in which any task specularly will reflect it to the viewer.
Another approach which has heretofore been employed is to place a baffle such as an opaque plate at the central area of the light source. The baffle prevents transmission of light from an area of the light source to the task. The task is illuminated by side lighting. Veiling reflections are eliminated as long as the task is positioned in a defined zone. ~hould the user move the task to tlle sides of the work surface, veiling reflections will again become a problem with either the "bat-wing" lens or the baffle approach.
The aforementioned prior approaches to eliminating veiling reflections have merely "blocked" the central area of the source and permitted side light to illuminate the task sufficiently for viewing and/or reading purposes.
An example of one prior system may be found in U. S. Patent No. 4,054,793, entitled LIGHTING SYSTE~ and issued on October 18, 1977, to Shemitz. This patent dis-closes a lighti,ng fixture including an elongated housing, a light source and a refractor element which distributes luminous flux from the light source in a bat-wing configur-ation. Another example of a refractor plate which distri-butes luminous flux from the light source in a bat-wing configuration may be found in U. S. Patent No. 3,258,5'30, entitled PLAIES FOR LIGIIT CONTROL and issued on J~me 28, ~7~398 1 1966, to Goodbar.
Other task lighting systems have attempted to control veiling reflections by polarizing the light emanat-ing -from the light source before it strikes the task. r,~hen a polarizing filter material is placed in front of the light source so that it is intercepted by light emanating towards the task~ the light is polarized before it strikes the surface. This polarization~ of course, eliminates one of the components of the light. Upon reflection, the remaining component is also eliminated. This polarizing concept does not block light emanating from the light source. An example of a polarizing system may be found in U. S. Patent No.
3,239,659, entitled GLARF.-REDUCING LAMP and issued on March 8, 1966, to Makas.
In situations where veiling reflections are not a problem because of the task characteristics, the brightness level of the luminaire could desirably be increased. This would increase the illumination which may be wanted by the user. Prior systems have not provided for ready adjust-ability of illumination levels.
A need exists for a luminaire or task lighting system which will control veiling reflections across the entire work surface yet which permits adjustment of illum-ination levels to the particular task being viewed and which accommodates differences in geometric orientation, task position, observer eye position and the height of the luminaire above the task so that the user can maximize the effectiveness of the luminaire.
~UMMARY OF THE INVENTION
In accordance with the present invention, the afore-mentioned needs are substantially fulfilled. Essentially J
~17~3~3 1 the present invention encompasses a task light control mask.
The control mask includes an at least translucent, member adapted to be supported at the light source. A variable light transmission means is carried by the member. The light transmission means controls the apparent brightness of the light source to reduce the brightness contrast across the luminaire and control veiling reflections. Provision is made for adjusting the position of the variable light trans-mission means with respect to the light source so that illumination levels can he controlled and the luminare may be adjusted for the particular task being viewed.
In narrower aspects of the invention, the light source and light mask member are supported within a large area, diffuse reflector. The reflector increases the apparent area of the light source thereby reducing the brightness of the system per square unit of area. As a result, the light which is reflected by the specularity of the task into the eye of the user is less bright. A reduc-tion in the specular brightness of the task is achieved which improves the apparent quality of the viewing situa-tion~
In an existing embodiment, the variable light transmission means is defined by a blocking medium. The medium has a pattern which is essentially configured to match the brightness of the reflector near the lamp and to create an apparently, uniform brightness level for the portion of the luminaire which might be reflected. The pattern reduces high areas of illumination at the work surface by a reduction in light transmission through ~he mask. ~niformity of illumination at the task area is achieved, and veiling reflections are controlled.
1 It is preferred that the member be rotatably adjustable within the reflector with respect to the light source. As a result, the mask pattern may be moved into and out of the area from which light emanates from the light source to the task. This permits adjustment by the user ofthe brightness levels achieved by the luminaire. As a result, adjustment for geometric differences~ eye position differences and height of the unit above the task are readily achieved.
The task lighting system in accordance with the present invention permits the user to control veiling re-flections and obtain an apparent uniform brightness without the use of lenses and/or opaque plates or baffles. This reduces significantly the overall size of the luminaire that would otherwise be necessary to achieve the same results.
This is a sigllificant advantage to the furniture designer since the lighting system is more readily accommodated to specific furniture design/size constraints. Aesthetics are more readily achieved at a reduced cost of manufacture. The luminaire may be integrated or built directly into a cabinet structure. Such integration of lighting systems with sur-rounding furniture has not heretofore been as readily or as easily achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic, side elevation of a lighting system in accordance with the present invention;
Fig. 2 is a perspective, bottom elevational view of the lighting system;
Fig. 3 is a cross-sectional view taken generally along line III-III o-f Fig. 2;
Fig. 4 is a front, elevational view of an elongated 3~3 1 light source and light control mask in accordance with the present invention;
Fig. 5 is a cross-sectional view taken generally along line V-V of Fig. 4;
~ig. 6 is a plan view of a portion of the variable light transmission means incorporated in the present inven-tion;
Fig. 7 is a schematic view showing the dimensions of a quadrant of one embodiment of the variable light trans-mission means of Fig. 6, Fig. 8 is a graph showing the approximate light transmission values across radial sections of the control mask dimensioned on the circumference; and Figo 9 is a graph illustrating the variation in I5 the light transmission values across longitudinal sections of the control mask.
DETAILED DESCRIPTION OF THE PREFERRED EMBODI~ENT
With reference to the drawings, Fig. 1 schem-atically ill~strates a light control system in accordance with the present invention which is primarily adapted for illuminating a task. The system includes a luminaire gen-erally designated 10 which is supported above a generally horizontal work surface 12. Luminaire 10 includes a re-flector generally designated 14, an elongated, linear light source 16 including a control mask 17. In the embodiment shown, source 16 is a fluorescent tube. Luminaire 10 may be suspended from the undersurface of a cabinet, shelf or the like and which is generally designated 18. In the alterna-tive, luminaire 10 could be supported from separate bracket structure in a position above the work surface 12.
Luminaire 10 is primarily adapted to illumina~e a 9~3 1 task 20 which is illustrated in a position on the work surface 12. As shown in Fig. 1, an observer may view the task from a position generally designated 22. The task has leading and trailing edges 24, 26. From the light rays 28, it should be apparent that the task defines a critical brightness zone 30 which is subject to the aforementioned veiling reflections. Light in the zone 30, that is, within the boundaries of the leading and trailing edges 24, 26 of the task, could be reflected to the eye of the observer 22.
It should be understood that as the task is moved both longitudinally and from the front to back of the work surface 12, the critical brightness zone would necessarily shift.
As seen in Figs. 2 and 3, reflector 14 of lumin-aire 10 includes first and second lateral edges 32, 34 and ends 36, 38. In the embodiment illustrated, the light source 16 and light control mask 17 extend between and are supported by ends 36, 38. It is presently preferred that the light source 16 and control mask 17 be supported imme-diately adjacent lateral edge 32. When mounted from a support structure lB, lateral edge 32 would be facing the viewing position generally designated 22. This positioning of the light source is preferred since the elongated tube will be essentially "hidden" from the eye of the observer.
Reflector 14 includes a support OT body 42 to which is secured a diffuse reflector 44 (Fig. 3). Reflector 44 includes a first, angled portion 46 immediately adjacent the elongated linear light source 16. Reflector 44 slopes generally away from the light source 16 along a portion designated 48 As should be apparen~ from the drawings, the reflector is a "large area" reflector which increases the ~7~398 1 apparent area source of the light emanating from the light source 16. This reduces the brightness of the luminaire or system per square unit of area.
In the structure of Figs. 4 and 5, light source 16 is a fluorescent light tube or elongated, linear light source 52. Supported around and substantially encircling the tube 52 is light control mask 17. ~ask 17 includes a generally tubular shaped member 54. ~lember 54 is at least translucent and pre~erably transparent. Tubular member 54 extends throughout the entire length or longitudinal dimen-sion of the fluorescent tube 52. Tube 52 is supported within tubular member 54 by end caps 56. The tubular member 54 is of a conventional configuration which has heretofore been marketed to protect the lamp from accidental breakage.
An example of such a tube may be found in U. S. Patent No.
3,676,401, entitled FLUORESCENT LAMP PROT~CTION APPARATUS
and issued on June 27, 1972, to DuPont. It is presently preferred that the tube be extruded from a clear polycar-bonate material.
As seen in Flgs. 2 and 4, tube or member 54 carries and/or supports a ~ariable light transmission means which is generally designated 64. The variable light transmission means extends throughout the longitudinal dimension of tube 54 and hence the fluorescent tube 52.
Further, -variable light transmission means 64 extends cir-cumferentially of the tube 54. The variable light trans-mission means 64 is defined by a plurality of regularly spaced lines. These lines define a pattern of opaque markings which is symmetrical about a longitudinal axis 66 and about a vertical centerline 68 (Fig. 4).
A fluorescent tube does not produce a uniform 139~3 1 brightness level throughout its length. Typically, such tubes are brighter along their longitudinal centerlines and in a central area intermediate the encls. The brightness levels of SUC]l tubes taper off from their vertical center-lines to their ends. Brightness varies along longitudinal and circumferential dimensions of the tube. This causes nonuniform illumination levels at the work surface. The entire work surface is not fully usable for positioning the task.
The primary purpose of the variable light trans-mission means 64 is to reduce the apparent brightness of the light source in a direction in which it would be reflected by the task. The objective is to match the brightness of the reflector near the lamp to create a uniform or apparent uniform brightness. The variable light transmission means 64 also reduces high areas of illumination, i.e., along the central area of the tube, so that uniformity of lighting at the task area is achieved~
Each end cap 56 has a circular flange portion 72 which is joined to a generally cylindrical hub portion 74.
Hub portion 74 defines a central throughbore which receives the ends of the fluorescent light tube 52. The end caps are pressed into the open ends of elongated tubular member 54.
As a result, tubular member 54 may be rotated relative to the fluorescent tube 52. As explained in detail below, this permits positioning of the variable light transmission means 64 to adjust for illumination levels and geometric dif-ferences encountered in mounting the luminaire with respect to a task. As explained in detail below, the adjustability feature allows the user to maximize the effectiYe illumin-ation of the system and to match such illumination levels to ~71398 1 the particular task which is being viewed.
A portion of the variable light transmission means 64 is illustrated in Fig. 6. As should be readily apparent from Figs. 4 and 6, variable light transmission means 64 is symmetrical about longitudinal axis 66 and about the vertical axis 68. As a result, only one-half of the pattern has been illustrated in detail.
I`~eans 64 includes a plurality of regularly spaced, opaque lines or markings which de-fine a pattern 82 having a varying density or open area. The opaque markings are in effect "overlayed" and define a plurality of zones which have been dimensioned in Fig. 7. The pattern having the dimensions of Fig. 7 was developed for use with an F-40, T-12 fluorescent light tube. ~uch a tube has an overall length of 4 feet, a 12/8 inch diameter and is rated at 40 watts.
The opaque lines, as should be readily apparent, define varying open areas or densities. The open areas or densities vary from the vertical centerline 68 towards the outer ends of the pattern along ~he longitudinal centerline 66. The pattern has more "open area" or is less dense as it approaches the ends than it has adjacent the central area about the vertical centerline 68.
A fluorescent light tube has a greater apparent brightness immediately about and along longitudinal center--line 66. Further, the brightness of the tube is greater about the vertical centerline 68 and hence within a central area of the tube. As discussed above, prior approaches to eliminating veiling reflections have modified the illumin-ation pattern of the fluorescent tube by eliminating light from the central area and redirecting it to the side areas.
~ i 3~ 8 1 Such systems are exemplified by the so-called bat-wing lenses and by the approaches which have positioned an opaque plate or a plurality of ba:Efles immediately adjacent and about the vertical centerline of the tube. These plates, baffles and lenses have eliminated direct light from the central area of the tube to the horizontal surface 12 where task 20 would be positioned. Typically, the task would be supported on the work surface at the central area of the light source. By eliminating the high brightness from the center of the light source, veiling reflections can be reduced since the task is essentially illuminated by side light. Veiling reflections will, however, remain a problem should the user r.love the task towards either end of the light source and away from the area from which direct vertical light transmissian is blocked.
In accordance with the present invention, this problem is eliminated. The variable light transmission means 64 extends throughout the length of the linear light source and creates an apparent uniform brightness from the luminaire. As a result, the user can move the task towards either end of the work surface and veiling reflections will not be a problem. The mask may be adjusted for the particu-lar eye position and geometric arrangement of the luminaire with respect to the work surface.
As mentioned above and as shown in Figs. 6 and 7, means 64 is defined by a plurality of overlayed patterns of opaque lines. Since means 64 is symmetrical about longi-tudinal 66 and vertical 68, only a single quadrant of the pattern for the existing embodiment will be described in detail. The quadrant (Figs. 6 and 7) includes a rectangular pattern bounded by lines a, b and c. Within the boundary ~7i3~8 1 lines a~ b and c are a plurality of vertically extending lines 88. Lines 88 have a height dimension of 1.250 inches (Fig. 7). Lines 88 are equally spaced along the boundary b which has a dimension of 23 inches. Lines 88 are spaced at 0.10 inch intervals along longitudinal 66.
Another pattern of lines is overlayed on lines 88.
This pattern is triangular and is bounded by a side d, a base e and a hypotenuse f. The pattern includes a plurality of equally spaced7 parallel lines 90 which extend -from base e at an angle g of 45 (Fig. 6). Side d has a dimension of 3.125 inches and base e has a dimension of 23 inches. Lines 90 are spaced at 0.10 inch intervals within boundaries d, e and f, Another pattern of parallel lines 92 is formed within boundaries h7 i and j ~Figs. 6 and 7). Lines 92 extend perpendicular to centerline 66 and are spaced from each other at 0.20 inch intervals. Boundaries h and j have a vertical height of 2.50 inches, and line i has a length of 6.00 inches.
Another triangular pattern bounded by a side k, a base 1 and a hypotenuse m is overlayed on the other pat-terns. Boundary k has a dimension of 1.875 inches, and base 1 has a dimension of 18.00 inches. ~ithin boundaries k, 1 and m are a plurality of lines 94. Lines 94 are angled with respect to base 1 at an angle n of 45 and spaced at 0.05 inch intervals (Fig. 6).
A final triangular pattern is bounded by a side a base p and a hypotenuse q. Boundary or side o has a dimension of 0.750 inches, and base p has a dimension of 12 inches. Parallel lines 96 are spaced within boundaries o, p and q. Lines 96 are spaced at 0.05 inch intervals and are 39~3 1 angled with respect to base p at an angle r of 45 (Fig. 6).
~leans 64 includes a final rectangular pattern o~
perpendicularly related lines 98, 100 bounded by sides s, t and e. Boundaries s and t have a dimension of 0.375 inches, and boundary e has a dimension of 23 inches. Lines 98 extend parallel to each other and parallel to longitudinal 66. Lines 100 extend parallel to each other and perpendicu-lar to longitudinal 66. Lines 98 are spaced from each other at 0.050 inch intervals. Lines 100 are spaced from each other at 0.50 inch interwals. The width dimension of each of the lines of all the patterns is approximately 0.050 to 0.055 inches.
The presently existing embodiment of the variable light transmission means 64 described above and illustrated in Fig~ 6 is photo offset printed on a sheet designated 120 in Fig. 6 of clear plastic material. The presently pre-ferred material is polyester. The sheet of clear plastic material having the patterns imprinted thereon is rolled and inserted into the light control mask tube 5~. This is illustrated in Fig. 5. As a result, the sheet of material 120 is carried and supported within tube 54 which therefore carries or supports the opaque markings. In the alterna-tive, the pattern could be imprinted directly on the clear or translucent tube 54. At present, howeverJ the tubes are obtained as seamless extrusions. If imprinted directly on the tubes, the tube could initially be formed as a flat sheet with the pattern imprinted thereon. The sheet would then be rolled to the desired configuration. The pattern might also be silk screened directly on the tube.
The specific pattern of lines illustrated in Fig.
6 for the presently existing embodiment produces light ~7~398 1 transmission values approximated in the graphs of Figs. 8 and 9 when surrounding an F-40, T-12 fluorescent tube. Fig.
8 is a graph showing the llght transmission values (Y ordin-ate) for the mask at radial sections tx ordinate) dimen-sioned on the circum-ference of the mask tube and pattern.
For example, the line designated "3 inch section" shows the variance in the transmission values from the centerline 66 circumferentially or perpendicular thereto along a vertical or circumferential line three inches from vertical 68. This is illustrated in Fig. 4. As shown therein, a line 128 has three data points marked thereon and designated 130, 132 and 134. Line 128 extends perpendicular to longitudinal 66 at a point spaced 3 inches from vertical centerline 68 along the longit-~dinal. Hence it is a three inch section. At the centerline and hence at point 130, the light transmission value is approximately 20%. At point 132, one inch from the centerline along line 28, the light transmission value is approximately 35%. At point 134, two inches ~from the center-line along the circumference, the light transmission value is approximately 60%. ~imilar measurements were made for vertical or circumferential lines spaced from the centerline ~- 68 along longitudinal 66 at 9, 15 and 21 inches. The values obtained were marked on the graph and the lines defining the ; graph were smoothed through the several data points. As a result, the light transmission values obtained from Fig. 8, except at the specific data points, are approximations of the actual values which would be achieved by the mask illus-trated in Fig. 6.
Fig. 9 illustrates the light transmission values along longitudinal sections of the mask taken along a line coincident with the centerline, a line one inch from the ~ 39 ~
1 centerline and extending parallel thereto and a line two inches from ~he centerline and extending parallel thereto.
The line designated "centerline" in Fig. 9 represents the light transmission values for points designated 130, 136, 13~ and 140 in Fig. 4. The data points are respectively at points along or parallel to the longitudinal at 3, 9, 15 and 21 inches from the vertical centerline 68. As shown, the light transmission values along the centerline towards the ends vary from approximately 20% to approximately 25%. The curves illustrated in Fig. 10 are also approximations. For example, the values given for the "2 inch section" represent a "smoothed curve'l for values measured three inches from the centerline, nine inches and fifteen inches from the center-line. The measured values at three and nine inches are plotted on the graph. The value at fifteen inches is 100%
since this point is out of the area of the pattern. The two inch line was then smoothly drawn inbetween these data points.
Dif-ferent line patterns or other transmission control mediums having open areas and/or densities which vary longitudinally and circumferentially of the control mask and which approximate the transmission values given in Figs. 8 and 9 would be in accordance with the present inven-tion. Sucn a light control mask and/or variable transmission means would be able to eliminate veiling reflections by approximating a uniform brightness le~el throughout the length of the fluorescent tube.
OPERATION
The luminaire in açcordance ~ith the preferred embodiment is assembled by inserting the fluorescent tube within the control mask defined by tube 5~ and variable -15~
~:1 7139~3 1 light transmission means 64. End caps 56 rotatably support tube 54 with respect to the light source. The assembly is mounted within reflector ~. The reflector is supported above the horizontal work surface. The narrow vertical height of the luminaire permits the furniture designer to readily integrate the lighting system into the furniture or office system. For example, the luminaire may be secured directly to or in the undersurface of a cabinet suspended from a panel and above a desk or other work area.
The user can rotate tube 54 to position the variable light transmission means. This adjusts the illum-ination levels to the particular task being viewed. Essen-tially uniform illumination can be obtained when the pattern is positioned to block light along the entire length of the fluorescent tube. When so positioned, a task havlng high specularity may be moved around on the work surface without encountering veiling reflections. If a higher illumination level is desired, tube 54 can be rotated to move some of the pattern out of line with rays from the light to the task.
The invention, therefore, provides a full range of adjust-ability. Size and cost restraints heretofore experienced are substantially reduced. Adustment can be made for geo-metric differences in the mounting of the luminaire with respect to t'ne work surface and for eye position differences.
In view of the foregoing description, those of ordinary skill in the art will undoubtedly envision various modifications which would not depart from the inventive concepts disclosed herein. The variable light transmission concept to control brightness could be employed with light sources other than the fluorescent tube shown. Also, the concept might be employed in systems other than task lighting ~713~8 1 systems The specific configuration of the reflector of theluminaire shown could be varied while still obtaining the desired results. A diffuse, large area reflector is pre-ferred, however, in order to increase the apparent area source of light emanating Erom the luminaire. Further, the luminaire including the light control mask and variable transmission means in accordance with the invention would function if the light source were supported adjacent the opposite latera] edge of the reflector from that illus-trated. It is preferred, however, that it be mounted in theposition shown so that it is essentially hidden from the observer when suspended beneath a shelf, cabinet or sup-ported by other bracket structure. Further, as set forth above, the precise pattern of opaque markings employed or the manner of defining the pattern having varying light transmission values could differ from that illustrated.
Other means such as variable density shading or a variable translucency on a sheet of material could be employed to obtain similar results.
Therefore, it is expressly intended that the above description should be considered as only that of the pre-ferred embodiment. The true spirit and scope of the present invention may be determined by reference to the appended claims.
Claims
The embodiments of the invention in which an exclusive property of privilege is claimed are defined as follows.
A light control mask for use with a generally linear light source to control light distribution, said mask comprising:
an elongated, generally tubular member having dimensions substantially equal to that of the light source and defining a longitudinal dimension;
means for rotatably supporting said tubular member around the light source; and variable light transmission means extending substantially along the entire longitudinal dimension of said member for controlling the amount of light trans-mitted through said member to thereby reduce areas of illumination longitudinally of said member and in a central area of said member so that said member can transmit less light in an area than at other areas and a more uniform brightness can be achieved, said variable light transmission means comprising a plurality of opaque markings which define a pattern having a longitudinal centerline and a vertical centerline along dimensions of said member, said pattern being relatively dense along a longitudinal centerline of the member to reduce high illumination levels which would emanate from a linear light source disposed within said member, said pattern being denser in said central area of said tubular member than adjacent the ends of the member, said pattern varying in density circumferentially of said member, and said light transmission means having a light transmission value along its longitudinal centerline which varies from approximately 20% at the vertical centerline of the member to approximately 25% at the ends of the member, said pattern being a mirror image of itself about the vertical centerline of the member.
A light control mask as defined by claim 1 wherein said member is an elongated, cylindrical tube, said pattern extending circumferentially of said member.
A light control mask as defined by claim 2 wherein said pattern is imprinted directly on said member.
A light control mask as defined by claim 2 wherein said pattern is imprinted on a transparent sheet of material which is carried by said member.
A light control mask as defined by claim 2 wherein said pattern is defined by a plurality of overlayed, spaced opaque lines.
A light control mask as defined by claim 5 wherein the pattern has a light transmission value along a longitudinal section which is one inch from the longitudinal centerline which varies from approximately 30% at the vertical centerline of the member to approximately 60% at the end of said member.
A light assembly for use in illuminating a task supported on a horizontal surface below and in front of the light assembly, said assembly including:
an elongated, linear light source having a central area, a longitudinal centerline and ends;
an elongated, light transmitting member at least partially encircling said light source, said member defining at least a portion of a cylinder;
support means for rotatably supporting said member around said light source so that said member may be rotated about the longitudinal centerline of said light source; and variable light transmission means carried by said member for varying the light transmitted through said member by said light source about a longitudinal centerline of said member so that a generally uniform brightness level may be achieved along the entire length of said member, said variable light transmission means defining a pattern of opaque markings having an open area inversely proportional to the brightness levels of the light source at longitudinal points thereof, said open area of said pattern varying both circumferentially and longitudinally of said tube, said support means permitting the positioning of the light transmission means to be varied to adjust apparent brightness levels at the task and to adjust for geometric differences, eye position and height of the light assembly above the task.
A light assembly as defined by claim 7 wherein said pattern is symmetrical about a longitudinal centerline and about a vertical centerline thereof and said transmitting member is a cylindrical tube encircling said light source.
A light assembly as defined by claim 8 wherein said pattern is defined by an overlay of a plurality of regularly spaced lines.
A light assembly as defined by claim 8 wherein said pattern is imprinted directly on said member.
-11- .
A light assembly as defined by claim 8 wherein said pattern is imprinted on a transparent sheet of material which is carried by said member.
A light assembly as defined by claim 10 wherein said pattern is defined by an overlay of a plurality of regularly spaced lines.
A light assembly as defined by claim 11 wherein said pattern is defined by an overlay of a plurality of regularly spaced lines.
A luminaire for illuminating a task and which controls veiling reflections caused by reflection of a light source off of the task, said luminaire comprising:
an elongated, diffuse reflector having first and second lateral edges joined by a transverse surface;
an elongated linear light source supported within said reflector adjacent one of said edges, said light source having a brightness level which is greater at its center than at its ends, and said reflector increasing the apparent area from which light emanates to reduce the apparent brightness per unit area of the light emanating from said luminaire;
variable light transmission means at least partially surrounding said linear light source for modifying the brightness of said light source to achieve a generally uniform level of brightness along said reflector to control veiling reflections, said light transmission means providing varying light transmissiveness circumferentially of said linear light source; and adjustment means supported by said reflector for rotatably supporting said light transmission means about said linear light source whereby said light transmission means can be rotated to adjust the apparent brightness levels at the task and to adjust for geometric differences, eye position and height of the luminaire above the task.
A luminaire as defined by claim 14 wherein said light transmission means comprises an elongated, at least translucent, cylindrical tube encircling said light source.
A luminaire as defined by claim 15 wherein said variable light transmission means comprises an opaque pattern carried by said elongated tube.
A luminaire as defined by claim 16 wherein said opaque pattern extends longitudinally of said tube, said pattern having a density proportional to the variation in the brightness level of said light source along the length of the light source.
A luminaire as defined by claim 17 wherein the density of said pattern varies longitudinally and circumferentially of said tube.
A light control mask for use with a generally linear light source to control light distribution, said mask comprising:
an elongated, generally tubular member having dimensions substantially equal to that of the light source and defining a longitudinal dimension;
means for rotatably supporting said tubular member around the light source; and variable light transmission means extending substantially along the entire longitudinal dimension of said member for controlling the amount of light trans-mitted through said member to thereby reduce areas of illumination longitudinally of said member and in a central area of said member so that said member can transmit less light in an area than at other areas and a more uniform brightness can be achieved, said variable light transmission means comprising a plurality of opaque markings which define a pattern having a longitudinal centerline and a vertical centerline along dimensions of said member, said pattern being relatively dense along a longitudinal centerline of the member to reduce high illumination levels which would emanate from a linear light source disposed within said member, said pattern being denser in said central area of said tubular member than adjacent the ends of the member, said pattern varying in density circumferentially of said member, and said light transmission means having a light transmission value along its longitudinal centerline which varies from approximately 20% at the vertical centerline of the member to approximately 25% at the ends of the member, said pattern being a mirror image of itself about the vertical centerline of the member.
A light control mask as defined by claim 1 wherein said member is an elongated, cylindrical tube, said pattern extending circumferentially of said member.
A light control mask as defined by claim 2 wherein said pattern is imprinted directly on said member.
A light control mask as defined by claim 2 wherein said pattern is imprinted on a transparent sheet of material which is carried by said member.
A light control mask as defined by claim 2 wherein said pattern is defined by a plurality of overlayed, spaced opaque lines.
A light control mask as defined by claim 5 wherein the pattern has a light transmission value along a longitudinal section which is one inch from the longitudinal centerline which varies from approximately 30% at the vertical centerline of the member to approximately 60% at the end of said member.
A light assembly for use in illuminating a task supported on a horizontal surface below and in front of the light assembly, said assembly including:
an elongated, linear light source having a central area, a longitudinal centerline and ends;
an elongated, light transmitting member at least partially encircling said light source, said member defining at least a portion of a cylinder;
support means for rotatably supporting said member around said light source so that said member may be rotated about the longitudinal centerline of said light source; and variable light transmission means carried by said member for varying the light transmitted through said member by said light source about a longitudinal centerline of said member so that a generally uniform brightness level may be achieved along the entire length of said member, said variable light transmission means defining a pattern of opaque markings having an open area inversely proportional to the brightness levels of the light source at longitudinal points thereof, said open area of said pattern varying both circumferentially and longitudinally of said tube, said support means permitting the positioning of the light transmission means to be varied to adjust apparent brightness levels at the task and to adjust for geometric differences, eye position and height of the light assembly above the task.
A light assembly as defined by claim 7 wherein said pattern is symmetrical about a longitudinal centerline and about a vertical centerline thereof and said transmitting member is a cylindrical tube encircling said light source.
A light assembly as defined by claim 8 wherein said pattern is defined by an overlay of a plurality of regularly spaced lines.
A light assembly as defined by claim 8 wherein said pattern is imprinted directly on said member.
-11- .
A light assembly as defined by claim 8 wherein said pattern is imprinted on a transparent sheet of material which is carried by said member.
A light assembly as defined by claim 10 wherein said pattern is defined by an overlay of a plurality of regularly spaced lines.
A light assembly as defined by claim 11 wherein said pattern is defined by an overlay of a plurality of regularly spaced lines.
A luminaire for illuminating a task and which controls veiling reflections caused by reflection of a light source off of the task, said luminaire comprising:
an elongated, diffuse reflector having first and second lateral edges joined by a transverse surface;
an elongated linear light source supported within said reflector adjacent one of said edges, said light source having a brightness level which is greater at its center than at its ends, and said reflector increasing the apparent area from which light emanates to reduce the apparent brightness per unit area of the light emanating from said luminaire;
variable light transmission means at least partially surrounding said linear light source for modifying the brightness of said light source to achieve a generally uniform level of brightness along said reflector to control veiling reflections, said light transmission means providing varying light transmissiveness circumferentially of said linear light source; and adjustment means supported by said reflector for rotatably supporting said light transmission means about said linear light source whereby said light transmission means can be rotated to adjust the apparent brightness levels at the task and to adjust for geometric differences, eye position and height of the luminaire above the task.
A luminaire as defined by claim 14 wherein said light transmission means comprises an elongated, at least translucent, cylindrical tube encircling said light source.
A luminaire as defined by claim 15 wherein said variable light transmission means comprises an opaque pattern carried by said elongated tube.
A luminaire as defined by claim 16 wherein said opaque pattern extends longitudinally of said tube, said pattern having a density proportional to the variation in the brightness level of said light source along the length of the light source.
A luminaire as defined by claim 17 wherein the density of said pattern varies longitudinally and circumferentially of said tube.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US247,848 | 1981-03-26 | ||
| US06/247,848 US4432044A (en) | 1981-03-26 | 1981-03-26 | Task lighting system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1171398A true CA1171398A (en) | 1984-07-24 |
Family
ID=22936628
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000396855A Expired CA1171398A (en) | 1981-03-26 | 1982-02-23 | Task lighting system |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US4432044A (en) |
| EP (1) | EP0061905B1 (en) |
| JP (1) | JPS57172603A (en) |
| AU (1) | AU550710B2 (en) |
| CA (1) | CA1171398A (en) |
| DE (1) | DE3263642D1 (en) |
| MX (1) | MX151159A (en) |
Families Citing this family (45)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4547813A (en) * | 1984-01-27 | 1985-10-15 | Burroughs Corporation | Apparatus for controlling light distribution in line scan optical imaging systems |
| US4573111A (en) * | 1984-04-04 | 1986-02-25 | Herst Douglas J | Linear light passing media having certain striped characteristics |
| US4536833A (en) * | 1984-04-16 | 1985-08-20 | Knoll International, Inc. | Lighting fixture utilizing a multi-layered hologram as a lens element |
| US4562515A (en) * | 1984-05-23 | 1985-12-31 | Emerson Electric Co. | Calibrated area source task light |
| US4536830A (en) * | 1984-07-26 | 1985-08-20 | Wisniewski Gregory G | Reflector assembly for lamp fixtures |
| US4617612A (en) * | 1985-01-22 | 1986-10-14 | Pritchett John C | High efficiency task lighting fixture |
| US5020252A (en) * | 1985-05-31 | 1991-06-04 | Boef J A G De | Illuminated sign system |
| JPH0687361B2 (en) * | 1985-08-09 | 1994-11-02 | 株式会社日立製作所 | Fluorescent lamp lighting device |
| JPS6240151A (en) * | 1985-08-14 | 1987-02-21 | Hitachi Ltd | Fluorescent lamp |
| US4626965A (en) * | 1985-11-21 | 1986-12-02 | Gupta Vijai P | Illumination system for a visual display terminal |
| US4722037A (en) * | 1986-08-15 | 1988-01-26 | Davis Charles S | Holographic device for generating multiple beams of light |
| US4704666A (en) * | 1986-08-15 | 1987-11-03 | Davis Charles S | Artificial light source utilizing a holographic optical element to control radiant light |
| US4713738A (en) * | 1986-08-15 | 1987-12-15 | Davis Charles S | Light fixture using a holographic optical reflector |
| US5144539A (en) * | 1987-07-09 | 1992-09-01 | Dai-Ichi Seiko Co., Ltd. | Illumination device |
| DE3853024T2 (en) * | 1987-07-09 | 1995-06-08 | Dai Ichi Seiko Co Ltd | Lighting device. |
| FR2631686B1 (en) * | 1988-05-19 | 1993-09-10 | Tapero Danielle | PROCESS FOR THE MANUFACTURE OF A LUMINOUS SUBSTRATE WITH HOMOGENEOUS ILLUMINATION AND LUMINOUS SUBSTANCE OBTAINED BY THIS METHOD |
| US4941071A (en) * | 1989-02-07 | 1990-07-10 | Steelcase, Inc. | Quick mounting arrangement for light fixtures in overhead cabinets and the like |
| JPH02284343A (en) * | 1989-03-22 | 1990-11-21 | Toshiba Lighting & Technol Corp | Low pressure mercury vapor discharge lamp |
| JPH05503226A (en) * | 1989-06-09 | 1993-06-03 | アーブ ヘッカー | natural light false window unit |
| US4991070A (en) * | 1989-07-12 | 1991-02-05 | Herman Miller, Inc. | Sleeve for a light element |
| DE59007118D1 (en) * | 1989-08-17 | 1994-10-20 | Siemens Ag | Workplace lamp. |
| US5040104A (en) * | 1990-03-19 | 1991-08-13 | Herman Miller, Inc. | Task light panel |
| US5036436A (en) * | 1990-06-14 | 1991-07-30 | Paul M. Rattigan | Task light |
| US5313724A (en) * | 1991-07-12 | 1994-05-24 | Warner Sheila J | Picture frame illumination apparatus |
| US5148356A (en) * | 1991-08-30 | 1992-09-15 | Gerry Baby Products Company | Crib light |
| DE4204325A1 (en) * | 1992-02-14 | 1993-08-19 | Karl Gerhard | LIGHTING DESK, LIGHTING PLATE OR THE LIKE FOR TRANSLUCTIVE TEMPLATES WITH ADJUSTABLE COLOR TEMPERATURE |
| US5902034A (en) * | 1992-04-08 | 1999-05-11 | Anthony's Manufacturing Company, Inc. | Display case with lens lighting system |
| US5895111A (en) * | 1992-04-08 | 1999-04-20 | Anthony's Manufacturing Company, Inc. | Display case with lens lighting system |
| EP0637925B1 (en) * | 1992-04-08 | 1998-06-03 | Anthony's Manufacturing Company, Inc. | Display case with lens lighting system |
| US5226719A (en) * | 1992-06-08 | 1993-07-13 | Steelcase Inc. | Quick mounting arrangement for light fixtures in overhead cabinets and the like |
| US5530628A (en) * | 1993-04-05 | 1996-06-25 | Peerless Lighting Corporation | Task light |
| US5471372A (en) * | 1993-12-06 | 1995-11-28 | Ardco, Inc. | Lighting system for commercial refrigerator doors |
| US5440467A (en) * | 1994-04-22 | 1995-08-08 | Steelcase Inc. | Task light |
| US5510965A (en) * | 1994-09-15 | 1996-04-23 | Plast-D-Fusers, Inc. | Adjustable reflector/director for fluorescent light fixture |
| US5570525A (en) * | 1995-01-06 | 1996-11-05 | Signstrut, Ltd. | Flexible face sign with uniform luminosity |
| US5879070A (en) * | 1995-06-07 | 1999-03-09 | Anthony's Manufacturing Company, Inc. | Louvered lighting system |
| US6386723B1 (en) | 1999-02-25 | 2002-05-14 | Steelcase Development Corporation | Tasklight for workspaces and the like |
| US6511204B2 (en) | 1999-12-16 | 2003-01-28 | 3M Innovative Properties Company | Light tube |
| US20040165391A1 (en) * | 2003-02-20 | 2004-08-26 | Aetek Uv Systems, Inc. | Method and apparatus for linear lamp irradiance correction |
| JP2005011634A (en) * | 2003-06-18 | 2005-01-13 | Nec Mitsubishi Denki Visual Systems Kk | Backlight system |
| US7828456B2 (en) | 2007-10-17 | 2010-11-09 | Lsi Industries, Inc. | Roadway luminaire and methods of use |
| US7950833B1 (en) | 2008-06-17 | 2011-05-31 | Genlyte Thomas Group Llc | Splay frame luminaire |
| US8794787B2 (en) | 2009-11-10 | 2014-08-05 | Lsi Industries, Inc. | Modular light reflectors and assemblies for luminaire |
| US8042968B2 (en) * | 2009-11-10 | 2011-10-25 | Lsi Industries, Inc. | Modular light reflectors and assemblies for luminaire |
| JP2017006890A (en) * | 2015-06-26 | 2017-01-12 | リンテック株式会社 | Light radiation device and light radiation method |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2374161A (en) * | 1943-11-10 | 1945-04-24 | Kemper Thomas Company | Lamp shading device |
| FR2217635B3 (en) * | 1973-02-14 | 1976-02-13 | Cauvi Ets Michel Fr | |
| US4186431A (en) * | 1978-04-28 | 1980-01-29 | Westinghouse Electric Corp. | Linear light source |
| US4254449A (en) * | 1978-10-10 | 1981-03-03 | Conwed Corporation | Task lighting system |
-
1981
- 1981-03-26 US US06/247,848 patent/US4432044A/en not_active Expired - Lifetime
-
1982
- 1982-02-23 CA CA000396855A patent/CA1171398A/en not_active Expired
- 1982-03-01 AU AU80977/82A patent/AU550710B2/en not_active Ceased
- 1982-03-17 MX MX191858A patent/MX151159A/en unknown
- 1982-03-25 JP JP57046460A patent/JPS57172603A/en active Granted
- 1982-03-25 EP EP82301585A patent/EP0061905B1/en not_active Expired
- 1982-03-25 DE DE8282301585T patent/DE3263642D1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3263642D1 (en) | 1985-06-13 |
| US4432044A (en) | 1984-02-14 |
| MX151159A (en) | 1984-10-04 |
| JPS57172603A (en) | 1982-10-23 |
| AU550710B2 (en) | 1986-04-10 |
| EP0061905B1 (en) | 1985-05-08 |
| AU8097782A (en) | 1982-09-30 |
| JPH0142441B2 (en) | 1989-09-12 |
| EP0061905A1 (en) | 1982-10-06 |
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| Date | Code | Title | Description |
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| MKEC | Expiry (correction) | ||
| MKEX | Expiry |