US 3930149 A
A lighting appliance for use in dentistry or the like provides for varying the intensity of the light output while maintaining a substantially constant color temperature thereof. In the lighting appliance a light source, which includes a high intensity lamp located at the inner focus of an ellipsoidal reflector and a heat absorbing filter, is movably positioned with respect to a light gate and aspheric lens. At maximum light intensity output from the lighting appliance the light source is positioned such that the gate is approximately in the plane of the external focus of the ellipsoidal reflector, and by moving the source from the gate, light is blocked by the latter dimming the effective output light.
Description (OCR text may contain errors)
United States Patent 1 French Dec. 30, 1975  VARIABLE INTENSITY DENTAL LIGHT  Inventor: Park French, Aurora, Ohio  Assignee: Sterndent Corporation, Mount Vernon, N.Y.
22 Filed: May 28,1974
 US. Cl. 240/4l.l5; 240/1.4; 240/41.3; 240/46.01  Int. Cl. A61B 1/06  Field of Search 240/41 R, 41.15, 1.4, l LP,
 References Cited UNITED STATES PATENTS 3,382,353 5/1968 3,596,083 7/1971 3,598,989 8/1971 3,689,761 9/1972 3,704,928 12/1972 3,775,606 11/1973 Bazell etal. 240/1 LP 3,806,236 4/1974 Downing 353/97 Primary Examiner-Richard L. Moses Attorney, Agent, or Firm-Donnelly, Maky, Renner & Otto  ABSTRACT A lighting appliance for use in dentistry or the like provides for varying the intensity of the light output while maintaining a substantially constant color temperature thereof. In the lighting appliance a light source, which includes a high intensity lamp located at the inner focus of'an ellipsoidal reflector and a heat absorbing filter, is movably positioned with respect to a light gate and aspheric lens. At maximum light intensity output from the lighting appliance the light source is positioned such that the gate is approximately in the plane of the external focus of the ellipsoidal reflector,
. and by moving the source from the gate, light is blocked by the latter dimming the effective output light.
14 Claims, 4 Drawing Figures US. Patent Dec. 30, 1975 3,930,149
l2 ll MW l/ VARIABLE INTENSITY DENTAL LIGHT BACKGROUND OF THE INVENTION This invention relates to a lighting appliance in which the light intensity output may be varied, and more particularly relates to such a lighting appliance for use in dentistry wherein the intensity of the light output may be varied without changing the effective color temperature of the light.
If the field of dentistry and other areas of medicine high levels of illumination over limited areas are often needed during examination and treatment of patients. In dental procedures, for example, examination of teeth and gums and all treatments and restorative processes require high illumination levels over limited areas so as not to cause discomfort to the patient. Thus, the area under treatment often can be adequately lighted by projected beams having diameters on the order of 6 to 8 inches. In various medical fields, including dentistry, podiatry and the like, it is desirable to provide illumination for the area under treatment wherein the light intensity is adjustable, for example from five hundred to three thousand foot candles at the normal operating distance, illumination is substantially uniform over the projected field, heat radiation is low, color temperature is high for good color rendition and the light field is conveniently shaped. Moreover, it is important in dentistry that the light field be on the order of 8 inches wide and three to four inches high with a relatively sharp cut-off to permit good illumination of all portions of the mouth without subjecting the patient s eyes to uncomfortable glare.
Various high temperature incandescent light sources of the halogen-quartz type are conventionally used in dental lamps. In such prior art lamps dichroic reflectors, heat filters and color filters are used in various combinations to reduce heat radiation and to increase the effective color temperature of the projected light. However, none of the prior art dental lights provide for constant high color temperature in the dimmed condition since dimming usually is effected by reducing lamp power which results in a decreased color temperature at a decreased intensity.
SUMMARY OF THE INVENTION In the instant invention a lighting appliance provides not only adjustable intensity, uniformity of illumination, low heat radiation, high color temperature and conveniently shaped light fields, but also provides for intensity adjustment while maintaining a constant high color temperature. In dentistry color matching of caps, replacement teeth and the like to be made effectively require the apparent light of the illuminated area not be affected by illuminating light; therefore, it is important that the latter remain at a high color temperature. By maintaining the light output at a high color temperature, the intensity of that illuminating light may be reduced to prevent eye strain to the dentist or surgeon without sacrificing color effectiveness.
The light projecting system of the invention utilizes a high intensity incandescent bulb, an ellipsoidal reflector, a heat filter, a field-shaping gate, and a projection lens. The lens and gate are positionally fixed, and the bulb, reflector and filter are movable with respect thereto. Moreover, the bulb filament is positioned approximately at the inner focus of the ellipsoidal reflector, and at maximum light intensity output the gate is at the outside focus of the ellipsoidal reflector. By moving the bulb, reflector and filter away from the latter position, an increased amount of light is blocked by the gate with a corresponding reduction in output light intensity from the lighting appliance, and since the power to the bulb filament remains constant the color temperature of the light emitted by the appliance also remains constant.
BRIEF DESCRIPTION OF THE DRAWING In the annexed drawing:
FIG. 1 is a side elevation view of the dental lamp of the invention with the side housing cover removed;
FIG. 1A is a plan view of a light gate;
FIG. 2 is an illustration of the main components of the dental lamp of FIG. 1 positioned for maximum light intensity output; and
FIG. 3 is an illustration of the main components of the dental lamp of FIG. 1 positioned for reduced light intensity output.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to the drawing wherein like reference numerals refer to like elements in the several figures, the lighting appliance, which may be used as a dental lamp, surgical lamp or the like, is generally indicated at l. The lamp includes an outer housing 2 of plastic, metal or the like presenting a pleasing outer appearance and as viewed in FIG. 1 the side cover of such housing has been removed to present the interior mechanism thereof. A conventional electrical power cord 3 exits the rear end of the housing 2 through a conventional strain relief fitting, and when power is supplied to the lamp a beam of light will be developed and exit from the housing front end 4. If desired, a switch, not shown, may be used to control power to the lamp 1.
A main support bracket 5 and a pair of slide support brackets 6, 7 provide support functions for various elements of the lamp 1 in the housing 2. A further support member 8 connected to the supports 5-7 supports a lens holder 9 in which an aspheric lens 10 is retained. The aspheric lens 10 has an external focal distance relative to the housing 2 to the right, as illustrated in FIG. 1, of approximately 20 to 30 inches, and an interior focal distance to the left interiorly of the housing of approximately 1 to 2 inches.
Also positioned on the main support bracket 5 is a light gate 11, which comprises an opaque non-reflecting metal plate having an open aperture 12 at a central portion thereof, as clearly illustrated in FIG. 1A. The gate 11 is preferably positioned in the interior or left hand focal plane of the lens 10, and the aperture 12 is aligned with the central longitudinal axis 13 of the lens, whereby an image of the aperture 12 is projected by the lens 10 in the exterior or right hand focal plane of the lens.
A light source 14 located within an inner movable housing 15 is positioned on the slide support brackets 6, 7 by conventional friction guides 16, which may be in the form of plastic bushings or the like, and a conventional rack and pinion mechanism 17 operated by an external wheel 18 provides for movement of the movable housing and the light source 14 back and forth along the slide support brackets 6, 7. The movable housing 15 includes an exit port 19, which is aligned with the aperture 12 and the axis 13 of the aspheric lens 3 so that light generated by the source 14 exiting the portion 19 and illuminating the aperture 12 is focused at the right hand focal plane of the lens to create a sharp image of the aperture. A power connection 20 from the electrical cord 3 provides electric energy to the light source 14 and to a blower or the like which also may be included in the movable housing for cooling the same. 1
Turning now more particularly to FIGS. 2 and 3, the optical parts of the lamp 1 are illustrated relatively schematically. The light source 14 includes a conventional high intensity incandescent bulb.21, an ellipsoidal reflector 22 and a conventional .heat absorbing filter 23 which may also modify the color of the transmitted light, such light source 14 being movably positioned with respect to the light gate lland aspheric lens 10 along an axis which coincides with the longitudinal or. central axisl3 of the lens. in FIG. 2 the light source 14 has been moved to a position relative to the gate 11 and lens 12 for maximum light intensity output as will be described below.
The bulb 21 is fastened in an electrical socket 24 and includes a filament-25 which receives electric power fromthe electric cord 3. Moreover, the filament 25 is positioned on the axis 13 at the inner focus 26 of the ellipsoidal reflector 22 and the reflecting surface of the reflector is stippled at 27 to diffuse the light reflected thereby eliminating bright spots which could be caused by a focused image of the filament at the external focus 28-of the ellipsoidal reflector. When the bulb 21 is energized asubstantially conical envelope 29.of relatively diffuse light is directed to the outer focus 28 of the ellipsoidal reflector 22, which illuminates the aperture 12 in the light gate 11. a v
. The configuration of the open area of the aperture 12 is representative of "the field of illumination projected by the aspheric. lens 10 since the former is in the focal plane of the latter; and for maximum efficiencybf the lamp 1 the size of the. incident portions 30 of thelight envelope 29,in the plane of the aperture 12 should be as close as ,possible to the actual size of the aperture at maximumlightjntensity output of the lamp 1. Thus, when the light source 14 is positioned so that the aperture 12 is at the outer focus 28 of the ellipsoidal reflector 22, a maximum amount of light in the. tapered incident portion 30 of the light envelope'29 will be transmitted through the aperture 12 into the transmitted portion 31 of the light envelope for projection by the aspheric lens 10. A sharp light pattern image of the aperture 12 will be projected by the lens 10 approximately 20 to 30 inches into the right hand focal plane of the lens, and the light pattern will become larger and less intense as the distance beyond such focal plane is increased and the light beam spreads; however, since the size of the aperture'12 is fixed, the size of the projected light pattern or field is constant, at respective.
distances from the lens 10. In dental'applica'tions of the lamp 1 the pattern of the projected light beam should point of the outer focus 28 the taper of the light envelope reverses and the incident light beam portion 300 begins to spread. The portion of the light gate 11 surrounding the aperture 12 blocks or absorbs a quantity of light 33 determined by the distance of the light source 14 and outer focus 28 from the gate, and the quantity of light in the transmitted portion 31a of the light envelope becomes correspondingly diminished, while the color temperature and pattern size of the light output from the lamp 1 remains constantonly the light intensity isdiminished. Thus, the light intensity output from the lamp 1- is controlled by movement of the light source 14 relative to the light gate 11 and lens 10 as indicated by the arrow 32a.
It is to be understood that equivalent means may be substituted for the ellipsoidal reflector 22 to concentrate the light from the bulb 21 in a substantially tapered envelope for attenuation by the gate 11, such as lenses or other reflectors. Moreover, although the light gate 11 is preferably in the form of a light transmitting aperture, a reflective aperture gate in the form of a central reflector on a non-reflective or transmissive background plate or support may conveniently be substituted therefor, whereby the light passed by the latter gate would be that reflected from the central reflector to the lens 10. I
It has been found that by using an aspheric lens 10 which has a focal distance external of the housing 2 of approximately 30 inches a convenient size light pattern is projected for illuminating a dental patients mouth, and the boundary of such light pattern remains relatively sharp since the light gate 11 remains positionally and geometrically fixed in the housing 2. at the inner focal plane of the aspheric lens 10. Moreover, simply by'rotating the wheel 18 the movable housing 15 is moved along'the slide support brackets 6, 7 and the intensity of the light in the illuminating light pattern is correspondingly adjusted while maintaining a uniform illumination pattern, low heat radiation, constant high color temperature and a same size conveniently shaped light field.
The embodiments of the invention in which anexclusive property or privilege is claimed are defined as follows: a
1. A constant color temperature variable intensity lamp, comprising light source means for generating a generally tapered uniform beam of light; gate means for passing at least a portion of such light and capable of precluding passage of a different portionof such light; and focusing means for projecting light passed by said gate means; said gate means being positioned at least proximate one focal plane of said focusing means for substantially focusing an image of the latter at the other focal plane thereof; means for providing relative generally axial movement between said light source means and said gate means, whereby movement of one with -respect to the other determines the quantity of light l 2. A lamp as set forth in claim 1, said light source "means comprising a bulb and a reflector, the latter 4. A lamp as set forth in claim 3, said filter altering the color and effective color temperature of the light.
5. A lamp as set forth in claim 2, wherein said reflector includes a stippled reflector surface that effects a uniform dispersion of light at said gate means.
6. A lamp as set forth in claim 2, said reflector comprising an ellipsoidal reflector having inner and exterior foci, said bulb being positioned at least proximate said inner focus, whereby light emitted by said bulb is concentrated in an envelope tapering toward said exterior focus.
7. A lamp as set forth in claim 6, said gate means comprising an opaque plate and an aperture generally centrally located therein, said reflector and aperture being so related that when said exterior focus lies in the plane of said aperture a maximum amount of light is passed therethrough, and movement of said light source means to a further distance from said gate means effects a reduction in the quantity of light passing through said aperture.
8. A lamp as set forth in claim 7, said focusing means comprising an aspheric lens, said lens having a longitudinal axis, and said light source and gate means being aligned relative to said axis.
9. A lamp as set forth in claim 1, said gate means comprising an opaque plate having a substantially centrally located aperture.
10. A lamp as set forth in claim 1, said focusing means comprising a lens.
1 l. A lamp as set forth in claim 10, said lens comprising an aspheric lens.
12. A constant color temperature variable intensity lamp, comprising a housing; light source means for generating a generally tapered beam of light, said light source means being movably positioned in said housing; means for moving said light source means within said housing; gate means for passing at least a portion of such light and capable of precluding passage of a different portion of such light; and focusing means for projecting light passed by said gate means; said gate means and focusing means being fixedly positioned relative to said housing, and said gate means being positioned at least proximate one focal plane of said focusing means for substantially focusing an image of the latter at the other focal plane thereof; said means for moving effecting relative movement between said light source means and said gate means, whereby movement of one with respect to the other determines the quantity of light passed by said gate means and hence the intensity of the projected light without varying the color temperature thereof.
13. A lamp as set forth in claim 12, said means for moving comprising a rack and pinion mechanism, said light source means, gate means and focusing means being optically aligned within said housing.
14. A lamp as set forth in claim 12, further comprising means for coupling said light source means to a