US 1751984 A
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March 25, 1930. 5 A, ESKI|LSON 1,751,984
REFLECTOR Filed Dec. 50, 1926 "l Y o /r @25W/ 3 @M M Patented Mar. 25, 1930 UNITED STATES PATENT OFFICE SVEN AUGUST ESKILSON, OF STOCKHOLM, SWEDEN, ASSIGNOR TO AMERICAN GAB- ACGUMULATOR COMPANY, OF ELIZABETH, NEW JERSEY, A CORPORATION OF NEW JERSEY REFLECTOR Application led December 30, 1928. Serial No. 157,964.
My invention relates to reflectors which, within a certain pre-determined angle of effectivity, reflect light which impings thereupon back in the direction of incidence; that is, in the direction from which the rays come. Such reflectors are well adapted for. use in signalling, display and other purposes.
The general object of the invention-is to provide a reflector of simple construction and of a character such that it may be manufactured at relatively small cost. y
It also is an object of the invention to provide a reflector consisting of a mass of transparent material, such as glass, the opposing surfaces of which are of convex spherical shape, the centers of the respective spherical surfaces being co-incident.
A further object of the invention is to provide a reflector unit consisting of a solid mass of transparent material, such as glass, the front and rear surfaces of which are of convex spherical shape and the centers of which are co-incidental, but the radii of which may be of dierent lengths, the rear surface of Isaid unit being provided with light reflecting means.
A still further object of the invention is to provide a reflector unit consisting of a mass of transparent material having front and rear convex surfaces of spherical shape, which surfaces have a common center, the radius of curvature of the front surface upon which the rays of light impingebeing less than the radius of curvature of the rear surface, and a reflector provided upon the rear spherical surface, the reflecting surface of the said reflector being concave.
Another and further object of the invention is to provide a reflector comprising a plurality of reflecting. units integrally or otherwise secured together in contiguous relation to each other, the opposing surfaces of the said units being convexly spherical and the rear surface of each unit being provided with a covering having a concave spherical reflecting surface.
Other objects and advantages of the invention will be pointed out inthe description thereof which follows, or will be apparent from such description. In order that the inf vention may be readily understood and its many practical advantages fully appreciated, reference may be had to the accompanying drawing in which I have illustrated one form of mechanical embodiment thereof. However, it will be understood that the invention is susceptible of embodiment in other forms of construction than that shown, and that various changes inthe details of construction may be made within the scope of the claims without departing from the principle of the invention.
Fig. 1 is a View in central longitudinal section of a reflector unit which ma be either circular or polygonal in cross section and the opposing ends of which are of convex, spherical shape, the rear end of said unit including a reflector element having a concave spherical surface, the said view also showing a number of rays proceeding from different directions and impinging upon the front surface of the reflector unit, passing therethrough znd being reflected from the reflecting surace;
Fig. 2 is a similar view having a number of incident rays of light in parallel relation to each other and to the axial line which impinge upon the front surface of the reflector unit and after passing through the transparent mass thereof impinge upon the reectin surface of the reflector and are returned through the said mass and emerge from the front face thereof;
Fig. 3 is a view of similar character in which the reflector unit is shown in full line position and also is indicated by dash and dot lines in two other positions angularly related to each other and to the full line position, the saidview being shown for the purpose of demonstrating the maximum range of effectivity of a reflector embodying the invention;
Fig. 4 isa face or plan view of a reflector comprising a plurality of reflectors united together, preferably integrally;
Fig. 5 is a sectional view taken on the line 5 5 of Fig. 4; and
Fig. 6 is a similar view taken on the line 6-6 df Fig. 4 at right angles to the plane in which Fig. 5 is taken. c
In Figs. 1, 2 and 3 inclusive, I have illustrated a sin le reflector unit which will be referredA to 1n order that the principle of o eration or action may be set forth and exained. Such a unit as is illustrated in these gures is operative as a reflector and may be employed as such for practical purposes, but because of its small size the light beam whlch will bereflected thereby would be of such diminutive area as not to fulfill with complete satisfaction the necessities of Ia'practical structure for commercial purposes. A structure for commercial purposes preferably should include a pluralit of such units arranged in co-operative re ation to each other. It would be possible to construct and 'emiloy a single transparent mass or lens` bo y of a' size to give satisfaction commercially, but such a structure would be impractical from a commercial standpoint because` of its weight and because of the great expense lincident to the large mass of material em ployed-therein 'and to its manufacture.
The structure which is illustrated in Figs. 4 to 6 inclusive, and which consists of a multiplicity of reflector units like those illusf trated 1n Figs. 1 to 3 inclusive united in contiguous relation to each other, is commercial- :ly ractical, and, because of the cheapness wit which -it may be manufactured and its eiiiciency in operation, has been found to be very desirable.
.In Figs. 1 to 3 inclusive of the drawings, I have shown a reflector unit comprising a lens consisting of a mass or body 1 of transparent material, such as glass, which may be of any desired or preferred shape in cross section.
If a single unit should be employed for any purpose it preferably should be vcircular in cross section on account of its greater range of efl'ectivity, but when a plurality or multiplicity of such units are combined or united into a single unitary structure the respective units preferably should be polygonal in shape in cross section, for instance, hexagonal, as illustrated in Fig. 4 of the drawings, in order that they may be placed in close or contiguous relation with respect to each other.
Each lens mass or body 1 is provided with o posing convex spherical surfaces 2 and 3, t e former being the front, incident surface, that is, the surface upon which the light rays to be reflected impinge. These opposing spherical surfaces, 2 and 3, have a common center 4.
The rear surface 3 is provided with a coating 5, the concave surface of vwhich is light reflecting and is in effect coincidental with the surface 3 although it may be spaced slightly therefrom. Preferably this coating should be formed by causing it to adhere by any suitable means and in any suitable manner to the said surface 3. The said coating may be applied in the same manner as reflecting coatings are applied to ordinary mirrors.
The light rays impinge upon the front uncoated surface 2 ofthe lens body l of the reflector unit, and upon entering the said body are refracted and when they impinge upon the reflecting surface of the coating 5 upon the rear surface 3 are returned by reflection through the lens body and are again refracted as they emerge from said body into the at mosphere. Such refraction takes place in both instances in accordance with Wellvknown optical laws.
Because of the fact that the front or incident surface 2 of the lens body 1 of the rey yare convergent to a point or focus a pre-determined distance from said surface. This is independent of the angle of incidence as is indicated in Fig. l.
In Fig. 1 I have indicated three iight rays, 6, 7 and 8 impinging upon the surface 2 from different directions, that is, at different angles of incidence. These rays are parallel respectively with the axial lines 9,10 and l1 and are located at such distance therefrom that they intersect the lines 9, 10 and 11 at the point Where those lines inipinge upon the reflecting surface of the reflector 5, in consequence of which the reflected rays indicated at 12, 13 and 14 after emerging from the lens body 1 into the atmosphere are parallel With the respective incident rays 6, 7 and 8.
The radii of the two spherical surfaces 2 and 3 are designated by the reference letters 3,.
r1 and r2 respectively.
In describing Fig. 1 I have chosen or referred to single rays, but in Fig. 2 of the drawings I have indicated by means of a plurality of parallel incident rays, 15, 16 and 17 which are parallel to the axial line 10, avvide beam of incident light. The day 15 impinges upon the surface 2 at a point near its outer edge. It will be noted that it is refracted so that it cuts the axial line 10 at a point 20, a considerable distance inside the reflecting surface.l Upon reference to the parallel incident ray 16, it will be noted that after entering the body 1 it is so refracted that it is caused to intersect the axial line 10 at the point 21 upon the reliecting surface of the reflectors 5 which, as already indicated, is substantially co-incident with the surface 3.
Referring now to the incident ray 17, it will be seen that it is refracted in a direction such that it cuts or intersects an extension of the axial line 10 at a point 22 beyond the surface 3. and beyond the reflecting surface of the reflector 5. The rays 15, 16 and 17, after refraction, iinpnge upon the reflecting surface ofthe reflector 5 and are returned through the body l and emerge therefrom in the directions indicated by the lines 23, 24 and 25.
The first reflected ray designated by 23 is convergent with respect to the axial line 10. The next reflected ray designated by the line 24 is parallel to the said axial line, while the next reflected ray, 25, is divergent with respect to the said axial line. The angle between an incident or reflected ray and the axial line or a line arallel with said line is known as the ang e of divergence and is indicated in Fig. 2 at c1 and c2.
rIhe reflector surface in a reflector unit of the character disclosed herein should be placed at such distance from the front surface of the lens body as to insure the reflec-` tion of the greatest possible amount of light at the lowest or least possible angle of divergence. The distance at which the result is accomplished is dependent on the index of refraction of the transparent material emloyed in the construction of the lens body.
t is necessary that the reflecting surface be placed at such position that it intersects or cuts the axial line 10 at some point between the points 20 and 22, to which previous reference has been made.
It has been established by mathematical calculation and by design that the. best resulting reflection will be obtained when the relation between the radii r1 and r2 of the respective surfaces 2 and 3 (the latter representing in effect the reflecting surface of the refletctor 5 as well as the rear surface of the body l) is determined by the following for- In this formula n represents the index of refraction of the transparent lens body. If it be assumed that the transparent lens body l, preferably of glass, has an index of refraction of 1.53 it will be found that the ratio of r1 torg is as4to 6.
Even if the incident light rays impinge upon the incident surface of the lens at angles to the axis of symmetry or axial line of the lens indicated by the line l0 in the drawings, the said light rays will be reflected at the .same angle of divergence as heretofore indicated; thatV is, the light rays in the reflected light beam will be distributed in the same manner irrespective of the angle of incidence of the beam. This. of course. has reference to the case in which the light beam strikes the incident surface within the angle of effectivity indicated in Fig. 3 of the drawings as the angle a. In said Fig. 3 it will be noted that the dash and dot lines 26 and 27 which are drawn through the point 4 which is the center of the two surfaces 2 and 3, cut the surface 3' at points adjacent the side surface of the lcns body. It will be seen that rays of light drawn through the center 4 and making with each other a greater angle than the angle a shown in Fig. 3, would not cut or intersect the rear surface 3 but on the contrary would cut or intersect the side surface of the lens body and therefore would not be reflected. It is apparent therefore that the angle a constitutes the angle of effectvity of the unit.
The effectiveness of the unit for reflecting rays back and in the direction whence they came within the angular limit stated is indicated by the different indicated positions of the lens with respect to the incident rays as shown in Fig. 3 of the drawings. One position of the unit is shown in full line while the two other positions are indicated by the dash and dot lines 28 and 29.
As already indicated these units may be united and combined into a single unitary structure. Such a structure is shown in Figs. 4 to 6 inclusive of the drawings, wherein it will be seen that a plate 30 of transparent material is provided with a plurality or multiplicity of the said units united either integrally or otherwise so that they are contigucusly related to each other as is clearl indicated in Fig. 4 of the drawings. l hen so related the spherical surfaces of all of the units are hexagonal in shape except those at the outer edges of the group. The said plate consists of a plurality of such units so that the front surface thereof comprises a plurality of convex spherical surfaces 2 upon which the light rays from any source located in proper relation thereto impinge, While the rear surface thereof comprises a plurality or multiplicity of convex spherical surfaces 3. The entire rear surface of the plate 30 is provided with coating material of which the portions thereof upon the convex surfaces 3 cons'titute reflectors having concave reflecting surfaces. As already indicated with respect to the units, this coating may be applied or deposited in any suitable known manner.
The reflecting coating 5 upon the plate 30 may be protected by means of a covering which may consist of a thin sheet or coating of copper 3l (applied electrolytically or otherwise) or by means of paint, pitch, cement or any other suitable substance which may be placed thereover. The coating 5 upon single reflecting units should likewise be protected by means of a coating or sheet of copper or by other overlying protecting means.
The plate 30 is provided with a rim 32 which facilitates the mounting of the reflector shown in Figs. 4 to 6 in or upon a support therefor.
In the manufacture of a reflector such as is shown in Figs. 4 to 6 inclusive the sheet 30 may be of a thickness to provide lens elements or units in which the convex surface 2 will which the radius of the convex surface 3 will have a radius of 6 mm.
In the use of reflectors embodying the invention single reiector elements such as are shown in Figs. 1 to 3 inclusive may be arranged so as to form letters, signs and the like for giving signals, warnings, etc.\ If desired, coloring of. the reflected light may be effected by placing over the reflectors a sheet of colored transparent material, the color being of the character desired.
It may be noted alsol .that letters or other symbols which may consist of opaque lines upon a transparent sheetor of translucent or transparent portions u n an opaque back-ground or of slots or openings in an opaque sheet may be rendered visible by placY ing the same over a reflector comprislng a plurality or multiplicity of reflecting units of the character illustrated in Figs.` 4 to 6 of the drawings. A
It will be seen that by my inventionI have provided a structure in which the incident and reflecting surfaces are of a character such that reflecting devices may be manufactured With a minimum of expense. For -instance, the glass sheet with the convex spherical .surfaces 2 and 3 upon opposite sides thereof may be manufactured by pressing, rolling or lin any other manner which may be found to be practical.
Having thus described my invention, what I claim and desire to secure by Letters Patent is:
1. A light reflector structure comprising a sheet of transparent material having the capacity of refracting light, the said sheet having a plurality of contiguously related proj ecting spherical surfaces of hexagonal shape upon its opposite sides, one of the said sides v constituting the front surface 4of the sheet upon which the light rays impinge and the other of said sides constituting the rear sur.- face from which the said rays are reflected, the said spherical surfaces being arranged in pairs in oppositely disposed relation to each other, the surfaces of the respective pairs having a common center, and means for rendering the rear spherical surfaces light refleeting, and said sheet of transparent matethe rear side of said sheet of glass light re-l `of which rojects beyond the plane of the last name means.
3. A light reflector structure comprising a sheet of glass having upon its front side upon l- Which light' is adapted to impinge a plurality of contiguously related projecting spherical surfacesl of hexagonal shape and also having upon its rear side a plurality of contiguously related projecting spherical surfaces of like shape, each spherical surface upon the front side of the said sheet of glass being opposed to a spherical surface upon the rear side thereof, the said two opposing surfaces having a common center, a coating upon the rear side of the said sheet of glass to render the said spherical surfaces light reflecting and a protecting coating or sheet of metal or other suitable material mounted upon and overlying the first named coating to protect the same, and the said sheet of glass having a rim the rear edge of which projects beyond the ing.
my invention, I have hereunto signed my name this 17 th day of December, 1926.
SVEN AUGUST ESKILSON.
- rial having a rim, the rear edge of which v projects beyond a plane tangent to the said rear spherical surfaces.
2. A light reflector structure consisting of a sheet of glass having spherical projections upon its front side and spherical projections upon its rear side, the spherical surfaces ofA said projections being hexagonal in shape, the said projections on both sides being contiguously related to each other and each spherica'l surface upon the front side of said sheet of glass being opposed by a spherical surface upon the oplposite rear side thereof, the said opposed sp erical surfaces having the same center, means for rendering the surface upon In testimony uthat I claim the foregoing as plane of the said protecting coaty