US3242328A - Illumination device - Google Patents

Description

March 22, 1966 N. s. KAPANY ET AL 3,242,323

ILLUMINATION DEVICE Filed March 12, 1962 5 Sheets-Sheet 1 INVENTORS Norinder S. Kopony David F. Copelloro Ralph Gostensen ATTORNEY-5' March 22, 1966 ILLUMINATION DEVICE Filed March 173, 1962 N. S. KAPANY ETAL 5 Sheets-Sheet z INVENTORS Norinder S. Kclpony David F. Copelloro Ralph G. Osfensen Mfil? w ATTORNEYS March 22, 1966 N. s. KAPANY ETAL 3,242,328

ILLUMINATION DEVI GE Filed March 12, 1962 5 Sheets-Sheet 5 INVENTORS n Mm w Wmm E e et W Kp 00 0 mm w m m, A wwm NDR United States Patent 3,242,328 ILLUMINATION DEVICE Narinder S. Kapany, Woodside, and David F. Capellaro,

Belmont, Calif., and Ralph G. Ostensen, Morton Grove,

Ill., assignors, by direct and mesne assignments, to

SCM Corporation Filed Mar. 12, 1962, Ser. No. 179,025 1 Claim. (Cl. 2401) This invention relates to illumination devices and, in particular, to illumination devices for use in making photographic exposures of image bearing sheets, such as typed or printed pages, on photosensitive paper. Specifically, this invention relates to illumination devices of the type described above incorporating edge-lighted illuminated panels composed of a plurality of light transmitting laminae.

Many types of photocopying exposure devices can be found on the market today but most are too cumbersome to be ,easily moved from one place to another and many include liquid developing baths which make moving the device a rather hazardous operation. A great number of these machines are equipped with inferior light distributing elements and, as a result, faded out areas and hot spots frequently appear on the copies, making good reproduction diflicul-t. The large size of their light distributing elements makes it awkward and, occasionally, entirely impossible, to obtain an exposure of a page of a book without permanent injury to the [backing of the book.

Edge-lighted prisms have heretofore been employed in photocopying devices in attempts to overcome the problems appurtenant to conventional photo'copiers. One type of edge-lighted prism was formed [from a single rectangular block of Lucite or optically similar material. One face of the block was roughened, and was oriented in a horizontal plane and constituted a light emitting and diffusing surface. A light source was positioned adjacent a highly polished end face of the block which acted as a light receiving surface. To insure .a more uniform distribution of light, a number of horizontal, vertically spaced apart slots were provided in the block parallel to the light emitting surface, the block, therefore, consisting of a number of relatively thin, vertically spaced apart elements connected to each other adjacent the light receiving edge. The upper surfaces of these elements adjacent the light receiving face were high-1y polished to act as reflectors and the remainder of these surfaces were roughened to act as diffusers. The length of the reflecting portion of the lowermost surface was relatively short with this distance being increased for each successive element.

In theory, light rays emitted from the source would enter the light receiving edge of the block and be distributed among and travel through the several elements until the roughened surface portion was reached. As they impinged on the roughened surfaces, the light rays would be broken up and directed upwardly to the light emitting surface where they would be further broken up and emittedin a uniformly dispersed pattern. A typical edge-lighted prism of this type is illustrated in FIGUR'ES 12-l4 of United States Patent 2,347,665 issued May 2, 1944, to G. B. Christensen et al. for Internal Reflection Lighting Means.-

The number of defects inhering in this type of prism rendered it impracticable. The comparatively iihin, cantilevered, light transmitting elements were structurally weak, thus necessitating a complicated support structure. The prism was difficult and expensive to fabricate, especially the polishing and roughening of the surfaces of the light transmitting elements. It was impossible to obtain an exposure close to the binding of a heavily bound volume without injuring its backing. The uniformity of light distribution across the light emitting face was not satisfactory. Light rays entering the prism at an angle to the normal less than the critical angle were emitted directly from the light emitting face, and, as the number of such rays was large, hot spots (areas of high intensity) were produced on the emitting face adjacent the light receiving edge. This type of prism was inefficient, since a significant portion of each of the light rays broken up on the roughened surface of the elements would be directed downwardly rather than upwardly and would be lost.

Laminated edge-lighted prisms in accordance with the present invention, in contradistinction to devices of the type described above, are extremely strong structurally, being formed of a plurality of bonded together light transmitting laminae. They are easily and inexpensively manufactured as the necessary polishing and roughening operation-s may be performed before the laminae are assembled and the forming steps are comparatively simple. The novel wedge-like configuration makes it a simple operation to obtain an exposure of the page of a book without injuring its backing. An improved arrangement of light absorbing and reflecting elements together with the superior light conducting properties of the novel laminated structure eliminates hot spots and otherwise vastly increases the uniformity of light distribution. Novel reflection means may be employed to recapture downwardly directed rays, which would otherwise he lost, to increase the efliciency of the prism.

The primary object of this invention is, therefore, the provision of an improved light distributing element which will eliminate all faded out areas and hot spots on photosensitive copy paper when employed in a photocopying exposure device.

Another object of this invention is the provision of a relatively simple photocopying exposure device which is light in weight and comparatively inexpensive to manufacture.

Still :another object of this invention is the provision of a photocopying exposure device which may be used to copy the pages of a bound volume without injury to the backing of the volume.

These and other objects of the present invention will become more fully apparent from the appended claim and .the descriptive text that follows.

Basically, the apparatus consists of a rectangular, wedgesh-aped, prismatic element composed of a plurality of superposed, preferably uniformly thick, internally reflective, light transmitting laminae together with a support cover, a light box, and a timer. The material tobe copied or exposed is inserted between a lateral light emitting face of the prismatic element and the cover with a sheet of photosensitive paper. The cover is then closed and a timer control turned on. After a predetermined exposure time interval, the timer automatically turns the exposure device off and the original and copy may he removed and the copy developed in any convenient manner.

The same procedure is used when copying the pages of a book except that the cover of the device is removed and the book is held down upon the light emitting face of the light conductive element with the photosensitive paper between the page of the hook and the element.

The invention will be more easily understood by referring to the following drawings wherein:

FIGURE 1 is a perspective view of a photocopy device embodying the principles of the present invention, showing it in the condition in which it is used to copy a single sheet;

FIGURE 2 is a sectional view of the photocopy device taken substantially alongline 22 in FIGURE 1;

FIGURE 3 is a perspective view of a modified photocopy device embodying the principles of the present invention, showing it in the condition in which it is used to copy a page from a book;

FIGURE 4 is a sectional view of the modified photocopy device taken substantially along line 4-4 inFIG URE 3;

FIGURE 5 is a perspective view of the light conductive element as seen from above and in the orientation in which it is employed in the photocopy device illustrated in FIGURE 1;

FIGURE 6 is a sectional view of the light conductive element, taken substantially along line 6- 6 of FIG- URE 5;

FIGURE 7 is a perspective view of the light conductive element as seen from above and in the orientation in which it is employed in the modified photocopying device illustrated in FIGURE 3; and,

FIGURE 8 is a sectional view of the light conductive element taken substantially along line 88 of FIG- URE 7.

FIRST EMBODIMENT FIGURES l and 2 show a first complete physical embodiment of the invention. An original 10 to be copied and a sheet ofphotosensitive copy paper 12 are inserted as a two-ply laminar assembly between a pivotedcover 14 and an upwardly facinglight emitting surface 13 of a laminated'lightconductive element 16.Element 16 is a wedge-like prismatic body composed of a plurality of superposed, preferably but not necessarily uniformly thick laminae of light transmitting material which, in the specific illustrated and preferred embodiment, is methyl methacrylate (or as it is commercially known, Lucite).Element 16 will hereinafter be referred to as a laminated Wedge for simplicity. The invention is not restricted to Lucite. Any similar rigid light conductive material, such as glass, fused quartz or any of the transparent plastic compositions which in themselves or which when coated with a material whose index of refraction is significantly different than that of the light conductive material exhibits the phenomenon of total internal reflection, may be used.

Lucite is particularly advantageous to use because its index of refraction is significantly different from the index of refraction of air to produce the phenomenon of total internal reflection. However, if other light transmitting material is used for the laminae of the wedge, the binder material used to bond the laminae together must be of a significantly different refractive index than that of the light transmitting material.

With the original 10 and thephotosensitive paper 12 in place, thetop cover 14 is lowered until a compression pad 18 (see also FIGURE 2) of plastic foam or sponge rubber compressessheets 10 and 12 against light emittingplanar surface 13 ofwedge 16.Top cover 14 is then locked in place bylatch 20 and atimer 22, located inlight box 24, is turned on.

Located inside of light box 24 (FIGURE 2) is atubular fluorescent lamp 26 which is covered by avinyl sleeve 28, circumferentially lined with numerous graduated fine black circles (not shown) at predetermined, axially spaced intervals.Sleeve 28 is of a conventional construction which is frequently used on tubular fluorescent lamps to insure that even light distribution is attained the full length of the tube. Any type light source may be used in place of the fluorescent lamp.

Whentimer 22 is turned on, thefluorescent lamp 26 is instantly lighted. After the proper length of time necessary to expose thephotosensitive paper 12 has elapsed,timer 22 automatically shuts off the machine and the exposed copy paper may be removed.

Generally, the structure of the apparatus is simple. Light [box 24 may be constructed of sheet or die cast metal or of wood, metal being preferred for a more sturdy construction.Top cover 14 and support 42 forlaminated wedge 16 may be constructed of similar materials. The

wiring of the apparatus is very simple and follows standard methods. Electric power is supplied from an AC. outlet through aplug 45, a switch (not shown) controlled bytimer 22, and atransformer 46 to the input terminals oflamp 26.

Fluorescent lamp 26,vinyl sleeve 28,transformer 46, andtimer 22 are all standard items and can be of any commercially available construction.

An important item to note at this point in relation tofluorescent lamp 26 is that the length of the light emitting portion should be longer than light receivingedge 47 oflaminated wedge 16 and its diameter should be greater than the width of this edge to assure uniformity of light concentration over the entire surface ofedge 47 and thereby prevent faded out areas on the copy paper overlying thelight emitting surface 14 ofwedge 16 adjacent its lateraloutside edges 48.

The most important part of this invention is the novel formation of the laminated wedge 16 (see FIGURE 5) which embodies a very special geometry and arrangement of light absorbing, reflecting, and diffusing surfaces which, it has been discovered, gives a more uniform lighting over the entire copyingsurface 13 than any other design known to applicant. Referring to FIGURES 5 and 6,laminated wedge 16 is constructed of a plurality of superposed laminae of substantially uniform thickness bonded together by a suitable binding material. In FIG- URES 5 and 6 four such laminae 46a-d are shown though it is to be understood that this particular number was selected for purposes of illustration and the particular number employed is not critical but will depend upon the particular application of the invention.Lami nated wedge 16 has four lateral planar faces 13, 47, 50 and 52. Faces 1 3 and 50 are parallel and are normal to the light receivingedge face 47 which they intersect at lines E and A respectively.Surface 13 is the light emitting face oflaminated wedge 16.Surface 52 intersects surface Stl at line D at a large obtuse angle and intersectssurface 13 at line C a small acute angle. The acute angle is sufliciently small to permit insertion of thelaminated wedge 16 between the pages of a book with line C closely adjacent its binding without injury to the backing and sufficiently large for stnuctural strength and rigidity. Lines A, C, D and E are all parallel. Faces 13, 47, 48 and 50, and the internally disposed surfaces of laminae 46a-d are all polished.Face 52 is uniformly roughened, as by sand blasting, and functions as a light diffuser.Equal width portions 58 and 60 (bounded by lines E and F and by lines A and B, respectively) ofpolished surfaces 13 and 50 are covered with a light absorbing material such as black paint.

FIGURE 6 illustrates the progress of four typical light rays a, b, c, and d throughlaminated wedge 16. Ray a impinges on wedge edge face 47 intermediate the upper and lower surfaces of lamina 46a which it enters. It next impinges upon the lower surface of lamina 46a at an angle to the normal greater than the critical angle and is reflected upwardly to the upper surface of lamina 46a. Ray a proceeds, in this manner, through lamina 46a until it reachesedge face 52 intermediate the upper and lower surfaces of lamina 46a. Sincesurface 52 is roughened, ray a is broken up, half being emitted from roughened face 5'2 and half being reflected through lamina 46a and impinging onsurface 13 at an angle to the normal less than the critical angle thus leaving thelaminated wedge 16. Ray b impinges onedge face 47 intermediate the upper and lower surfaces oflamina 46b at such an angle that it travels directly to edge 52 where it is broken up in the same manner as ray a. Ray c exhibits the same characteristics as ray a except that it entersedge face 47 intermediate the upper and lower surfaces oflamina 46c and is reflected between its upper and lower faces until it reachesedge 52. Upon reachingedge 52, it is broken up, half of it being reflected through;laminated wedge 16 and impinging onsurface 13 at. an

angle to the normal less than the critical angle and thus leaving thewedge 16. Rays a, b, and c are typical of the rays necessary for light to emerge fromsurface 56 in a uniform pattern.

To correct for hot spots (which are caused by greater levels of light intensity usually found adjacent the light source in the prior designs of edge lighted panels), means for intercepting the undesirable rays and means for increasing the probability of internal reflection Within laminae 46a-d before a ray impinges onlight scattering surface 52 are provided.

Ray d strikessurface 50 between lines A and D at an angle to the normal greater than the critical angle, is reflected to the upper surface of 46d and is then reflected downward to a light scattering point onsurface 52 at a distance further alonglaminated wedge 16 than would have been found the case if this ray had hitsurface 52 immediately after entering the wedge. Because there are many rays that will follow similar paths, the present invention purposely provides the reflective area between lines B and D onlamina 46d and on the contacting surfaces of laminae 46a-d so as to causemany of those rays to be reflected further down thelaminated wedge 16 before impinging onface 52 and thereby eliminates the hot spots close to edge 47.

Ray 2 entersedge 47 oflaminated wedge 16 intermediate the upper'and lower surfaces of lamina 46a and is immediately absorbed by black paintedarea 58. This degree of downgrading is necessary to prevent the large number of random rays entering edge from also causing greater levels of light intensity or hot spots along this edge. Black paintedarea 60 serves the same purpose.

As noted in FIGURE 6, light emanating fromsurface 52 would normally be lost because it it is not coated with a bonding. To recapture this lost light, a sheet of white paper 62 may, in accordance with the teachings of copending application No. 103,355 filed April 17, 1961, now Patent No. 3,132,810, and assigned to the same assignee as this invention, be provided adjacent, but not in full surface-to-surface optical contact with, roughenedsurface 52. The actual relation betweensurface 52 and sheet 62 is shown in FIGURE 6. The lost light is reflected and caused to re-enterlaminated wedge 16, augmenting the light emanating from printingsurface 13. Thus, it will be seen that maximum use has been made oflight source 26. It is, of course, to be understood that instead of using white paper 62 as a reflector, the same effect can be achieved by painting the inside surface 42 of wedge support 44 (FIGURE 2) white.

With respect tolaminated wedge 16, it is important to note that the bonded superposed laminae are optically independent. Thus,light entering edge 47 is trapped in the individual lamina and is transported without material loss to thelight emitting face 52 of the wedge. As may be seen from FIGURE 6, the light is, because it does not leak from one lamina to another, distributed to and emitted fromface 13 in a highly uniform pattern. The uniformity of distribution achieved by a laminated Lucite wedge in accordance with the principles of the present invention is, in fact, of an order heretofore unapproachable in edge-lighted illuminating panels.

The specific dimensions of one practical embodiment oflaminated wedge 16 when made of Lucite are given in FIGURE 6. The relative proportions of these dimensions should preferably be kept substantially the same for optimum results.

SECOND EMBODIMENT FIGURES 3 and 4 show a somewhat modified embodiment of photocopying device in accordance with the present invention set up to copy a page of a book. As in the first embodiment, the apparatus includes a rectangular, wedge-shaped, light conductive, laminated, bond- 6 edprismatic element 16 together with asupport 44, alight box 24, atimer 22, and a cover 14 (which has, in this instance, been removed for a purpose which will be explained presently). All of these components are identical to the corresponding components in the first embodiment with the exception oflight box 24 and wedge support. 44 which have been slightly modified to supportlaminated wedge 16 with face 52 (which in this embodiment is employed as the light emitting face) oriented in an upwardly facing horizontal position. I

FIGURE 4 shows the machine set up to copy a page of abook 32. The top cover (see FIGURE 1) is removed by lifting hinge pins 34 and 36 (FIGURES 2 and' development of the photosensitive paper will result in aperfect copy. It may be helpful to press down firmly on i the book by hand to insure that the photosensitivepaper is absolutely flat, which it must be to avoid blurred edges and distortion in reproduction of the printed matter closest to the page edge nearest the binding of the book.Thelaminated wedge 16, due to its relatively sharp edge, fits easily between the pages of thebook 32 closely adjacent the binding without injury to its backing. I

In conjunction with the foregoing description, it will, of course, be understood that the second embodiment of the photocopying device may be employed in the same manner as the first embodiment to copy a single sheet of material and that the first embodiment may be utilized to copy the pages of a bound volume by proceeding in the manner described in conjunction with the second embodiment.

FIGURE 8 illustrates the progress of five typical light rays 1, g, h, j, and k throughlaminated wedge 16. Ray f, after impinging onedge 47 intermediate the upper and lower surfaces oflamina 46d, strikes the light scattering, roughened surface oflight emitting face 52 where it is broken up, emerging from the face in a scattered pattern as shown in FIGURE 8.

Ray g, after enteringedge 47 intermediate the upper and lower surfaces oflamina 46c, strikes the lower surface oflamina 460 at an angle to the normal greater than the critical angle and is reflected upwardly to surface 52 where it is broken up in the same manner as ray 7. Ray h entersedge 47 intermediate the upper and lower surfaces oflamina 46b and is reflected alternately between these surfaces until it strikes, breaks up on, and emerges fromsurface 52. Ray 1' follows a path through lamina 46a similar to that which ray g follows throughlamina 46c. Rays 1, g, h, and j are typical of the rays necessary for light to emerge fromsurface 52 in a uniform pattern.

Finally, ray k entersedge 47 intermediate the upper and lower surfaces of lamina 46a at an angle to the normal less than the critical angle and is immediately absorbed by the light-absorbingmaterial 58. As we explained above in conjunction with the description oflaminated wedge 16, provision of absorbing areas such as 58 and 60 (see FIGURES 5 and 7) is necessary to prevent therays entering edge 47 from causing high levels of light intensity (hot spots) onsurfaces 13 and 50 adjacent this edge.

Thelaminated wedge 16 employed in this embodiment is, as was pointed out above, identical with the wedge employed in the first embodiment, the distinction in the two embodiments being in the orientation of the wedge. In both embodiments then, light rays are entrapped in the laminae 46a-d atedge face 47 and transported without loss by internal reflection from the surfaces of the respective laminae to endface 52. As they impinge on roughenedend face 52 the rays are, in both embodiments, broken up and emitted from the face in a uniformly dis-Tirner 22 is turned on and, as in the single persed pattern. In the first embodiment the rays, after being emitted fromface 52, are, of course, reflected from an external reflector 62 throughwedge 16 to surface 13 which is employed as the copying surface. In this embodiment,surface 52 itself is used as the copying surface. Highly uniform distribution of light across the copying surface is, it will be apparent, achieved in both embodiments since, in both, a uniform pattern of dispersement is established by light emittingface 52.

Sincelower surface 13 of lamina 46a is highly polished, thus constituting it a reflector, it is not necessary to employ an external reflector in this embodiment of the invention.

, The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claim are therefore intended to be embracedtherein.

' What is claimed and desired to be secured by United States Letters Patent is:

In combination with an elongated light source, a wedgelike prism formed of a plurality of individual, superposed, light transmitting laminae of substantially uniform thickness bonded together to form a unitary structure,

each lamina having internal reflective surfaces and a light receiving first lateral surface, parallel second and third lateral faces intersecting and normal to said first lateral surface and fourth lateral face intersecting said third lateral face at an obtuse angle and intersecting said second lateral face at an acute angle, the said fourth lateral face of each lamina being aligned to lie in a single plane whereby the apex provided on the longest lamina is an acute angle which can be inserted into the binding of a book without damage thereto with the second and fourth lateral faces having complete area contact with the entire surface area of pages in said book, said prism being formed to transmit light from said source through one of said lateral faces selected from the second and fourth to substantially uniformly illuminate a facing book page.

References Cited by the Examiner UNITED STATES PATENTS 2,347,665 5/1944 Christensen et al.

2,480,178 8/ 1949 Zinberg 2401 2,511,102 6/1950 Clouser 88--1 X 2,646,637 7/1953 Nierenberg et al. 240-1 X 2,995,970 8/1961 Hicks et al. 88-1 3,040,168 6/1962 Stearns 2401 X 3,132,810 5/1964 Ostensen 240-1 NORTON ANSHER, Primary Examiner.

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