US3847696A

US3847696A - Process for making light conducting plates

Info

Publication number: US3847696A
Application number: US00162918A
Authority: US
Inventors: L Ortner; K Heinzelmann; B Conrad; J Dierker
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1970-08-27
Filing date: 1971-07-15
Publication date: 1974-11-12
Anticipated expiration: 1991-11-12
Also published as: NL7107560A; DE2042408A1; GB1369052A

Abstract

A process for producing light-conducting plates which are particularly capable of use at the inlet of gamma cameras, is characterized by the use of transparent rods which are placed one next to the other, while means constituting distance holders which are thicker than the length of the light wave to be transmitted, are placed between the rods. At least one end of the rods is fixed by a casing mass, then it is ground and polished, and then the casting mass as well as the grinding and polishing means are removed.

Description

KR 3a8479696 V Emit e61 States 017mm at al.

{54} PROCESS FOR MAKXNG LIGHT [56] References Cited CONDUCTING WATES UNITED EI'ATES PATENTS [75] Inventors: Lorenz". Ortner, Fraucnaurach; 3,344.276 9/1967 Balding 150/80 Kari-Gem? n i l g 2,328,302 8/]943 :Simison 51/2123 Conrad, b th fE ;J hi;- 3,193.363 7/]965 241C115 et al l56/29t'1 Dierker, Buckenhof n of Germany 3,567,549 3/1971 liofirncister et 71L 65/4 1 Asilgmcl Siemens Aktlengfisfiusihafi, Primary Examiner-Alfred L. Lcavitt f Y Assistant Examinew-E-mnk F risendzl 14/101716), Agfll, 0r Fl Fi"?l'RlChLll'dS Geier [2]] Appl. No.: 162318 {57] ARS'ERACT A process for producing light-conducting plates which Foreign Appli giign Priorit D t are particularly capable of use at the inlet of gen-mm Aug 27 1970 Germany 2042408 cameras, is characterized by the use 01' transparent i f rods which are placed one next to the other, while 52 US C! U 156 I54, 52 283 4, means consmuting distance holders which are tl'ncKer I 156/182) l56/2g6 than the length of the light wave to be transzmtied. are [51] km Ci {2453 1/00 placed between the reds. At least one end of the rods 1581 M of 55111111:111113715571513 15' 292 is fixed by casing 11 1s l5(1,/293;5l/283; 350/96 B; 250/80, 227.

213 VT; 65/4, DIG. 7', 29/423, 424

ished, and then the casting mass as \l'ell as the grinding and polishing means are removed.

I 5 Claims, 4 Drawing Figures PATENTEDHUY 12 19m Fig.4

A THRI E PROCESS FOR MAKING LIGHT CONDUCTING PLATES a photocathode, wherein electrons are released by the light. The electrons are then transmitted as a visible image upon a second light screen at the outlet of the image changer after they have been subjected to acceleration, multiplying, etc.

Known light-conducting plates include as a rule rods or fibers consisting of a transparent core carrying a cover having a low refraction index which provides the total reflection at the walls of the core. These devices are quite suitable for the transmission of optical images which are greatly enhanced. However, when gamma ray images are being transmitted fine imaging is less important than the transmission of the greatest possible amount of light.

During the manufacture of light conducting plates consisting of transparent rods, particularly glass rods, placed freely one next to the other it is difficult, to produce optically perfect surfaces without it being neces sary to grind and polish the rods after the construction of the plate. However, when the completed devices are ground and polished, grinding and polishing means penetrate between the rods and produce deposits which are very difficult to remove. Means remaining at the rods produce a loss of light which is particularly detrimental when the light plates are used in gamma cameras.

An object of the present invention is the provision of a process for making light-conducting plates which would avoid the drawbacks of existingplates and of their manufacture.

Other objects will become apparent in the course of the following specification.

In the attainment of the objectives of the present invention it was found desirable to place transparent rods in parallel one next to the other, while means constituting distance holders which are thicker than the length of the light wave to be transmitted, are placed between the rods. At least one end of the rods is fixed by a castmg mass and is also ground and polished. Then the casting mass, as well as the grinding and polishing means are removed.

The casting mass, which can be a wax, protects the side surfaces of the rods against the effects of water and P events dirtying by polishing means. Furthermore, the casting means make the plate mechanically stable ga nst vibrations caused by the grinding and polishing f e s etc. ln addition, edge cuts etc, at the front surcs of the rods are prevented. To remove the casting i lf fll alter the grinding and polishing procedure, the lfj l used wax is melted out again and the system is "-h'i or example, in an ultra sound bath. The free between the rods permit free flow of cleaning "8 means. As means for the removal of wax W a c arttcularly suitable org solvents Such as enome or mixtures.

: n il. out

puts are produced particularly when apparently this is caused by the i ats a:

fact that light rays are also received which fall in only very flatly. These rays are caught along the side walls in the manner of a screw winder. As compared to rods having a square cross-section, this improves light output by 30 percent. Thus despite a loss at the light catching surface covering of at least 10 percent in case of the thickest possible packing, there is still a gain in ray transmission of 20 percent.

The material of the transparent rods can be a plastic as well as glass. when selecting the material care must be specially taken that it has the following properties:

ll Good pure transmission in the spectral range of the detector at the greatest possible refraction index.

2. Very well reflecting outer surface in case of drawn round rods.

3. Glass should be free from potash to avoid a K-40 ray base.

For this reason flint glass can be used which at the sodium-D-line has a refraction index of 1.62.

By the use of deformable parts, it is possible, for example, in case of fiber optics of totally reflectingglass rods with gas covering, particularly air covering, to use rods of the usual manufacture, without having to treat them subsequently. Tolerances in thickness which are unavoidable, are balanced by the deformations of the distance holders. The distance holders which can have the shape ofa wire, can consist of metals, such as silver, lead, copper, etc. However, other materials can be also used which can be shaped by deformation, without going back to deformation zero. A deformation which goes back completely to zero, should be avoided, since then there is the danger of breakage of the glass rods. The thickness of the wire-like distance holders should be about 0.2 to 0.5 mrn, in order to be adapted to the usual deviations in the thickness of glass rods having a diameter of about 7 mm.

A light-conducting plate'having the features of the present invention can be manufactured by pushing the rods into the meshes of a wire screen and then compressing them. By way of example, for image changers used for reproducing gamma ray images, glass rods of optical glass can be used consisting of drawn round rods with naturally blank surfaces, which are about 15 to mm. long with a 7 mm. diameter and having a tolerance of plus-minus 0.2 mm. They can be also provided with two copper wire rings. The use of an about 0.35 mm. thick cooper wire suffices to balance the expected tolerances. To produce the light-conducting plate the glass rods are set together so that the wire rings provide on the one hand the joining of the rods and, on the other hand, guarantee the maintenance of an air gap between them which is greater than the length of the light wave. As above stated, the thickness of the used wire rings depends upon the diarnctric toierance of the glass rods and the deformation capacity of the wire, with reference to use of limited pressure corresponding to the strength of used materials particularly glass.

To be able to use with success the light-conducting plate of the present invention for image transmitting devices as well, it is important that other optical elements could be optically coupled to the plate. For that purpose generally a medium is used such as, for exnrnplc, an immersion oil, which provided the optical coupling. Oils can. be used only if they cannot penetrate into the light-conducting plate (between 'the glass rods). To avoid the penetration of the coupling medium consisting of an immersion layer of silica oil" vide good attachment of the foils upon the ends of the light-conducting plate and to create good optical contact, a transparent-glue is used which can belong to one of several optical products and can be prepared upon the epoxide urea base. Prior to the gluing of the second foil the air gap between the glass rods is preferably filled with loose layered particles of an artificial material, having a diameter of about 0.2 mm. The diameter of the particles of the filled in powder or granules is not important, however, it must under all circumstances be large in comparison with the penetrating length ofthe light waves. Particles of the filling then absorb the light bundle which has not been caught by the light-conducting rods and thus prevent its spreading which can lead to a disturbance in the reproduced images (stray light suppression). It is possible to additionally prevent the penetration of not absorbed light rays by blackening the space between the rods upon the light inlet side. This will also prevent the widening of the uncaught light which could lead to the appearance of disturbing stray light base. The blackening can be produced, for example, by coating the foil with a photo-emulsion and by the use of a reverse caustic bleaching process. On the other hand, the creation of an optical mask is also possible by the usual so-c alled photo-resisting lacquer technics, for example, with a colored lacquer.

The invention will appearmore clearly from the following detailed description whentaken in connection with the accompanying drawing showing by wayof example only, preferred embodiments of the inventive idea.

In the drawing:

FIG. I is a section through an image magnifier provided with a light-conducting plate made in accordance with the present invention.

FIG. 2 is a front view ofa rectangular grid of deformable wire with glass rods inserted into its meshes.

FIG. 3 is a front view of a hexagonal grid with glass rods inserted into its meshes.

FIG. 4 shows in perspective a cut-out portion of-a light-conducting plate made by pressing together glass rods provided with wire rings, the plate being glued upon each of the two optically effective ends by a thin plastic foil and wherein the effects of the light entering between the rods is eliminated.

FIG. I shows a glass casing l of an image magnifier.

A pliotocathode 3 is located behind its front plate 2 and and a'light layer 11. The screen 9 is coupled to the image magnifying inlet 2 by a light-conducting plate 12 which consists of individual tight-conducting rods 13 as well as wire grids l4 and i5 located at a distance of 15 mm. from each other, the rods 13 being inserted into the meshes of the wire grids. I

FIG. 2 is an eniarged separate view of the wire grid 14. It is apparent that when it is compressed by the steel band 16, the wires 17 and 18 which consist of copper and are 0.35 mm. thick, are slightly pressed into the bearing locations of the rods 13 and thus provide a balance for thickness variations of the rods, as well as a firm hold. The light-conductors consist of glass rods which are 7 mm. thick and 15 mm. long. On one side they are adapted to the shape of the inlet window 2 and they have common concave outer surfaces on that side. The end surfaces of the plate 12 are connected with polyvinylchloride foils which are 60a thick, the foil 19 being located at the side close to the light screen and the foil 20 being located at the side of the image changer. Furthermore, an immersion layer 2Iconsisting of silica oil and having a thickness of 0.8 mm. is located between the foil 20 and the inlet surface of the image magnifier. A similar immersion layer is also provided between the layers 11 and 19 to improve light transmission.

Instead of a layer of oil the layers 11 and 19 can be joined by a putty of artificial resin.

FIG. 3 shows rods 22 of a different light-conducting plate which are cioser packed in the hexagonal holes of the honeycomb grid 23 in order to increase the light receiving surfaces. In other respects the construction is the same as that shown in FIG. 1.

FIG. 4 shows a plate 24 consisting of glass rods 25 which are provided at a distance of about 15 mm. with wire rings 26 and 27 of silver. The rods 25 are tightly packed, as in the arrangement shown in FIG. 3, so that the

wires

26 and 27 engage each other between the glass rods and so that a space remains consisting of the thickness of only one wire, amounting to 0.35 mm. Furthermore, foils 28 and 29 which are a thick and consist of polyethylenterephthalate are glued to the optical end surfaces of the rods by means of

layers

30 and 31 with an opoxide resin glue. Granules 32 of a plastic granulate fill in the spaces between the rods 25. Furthermore, at the ray inlet side a part upon the foil 28 is blackened by means of a layer 33 which covers parts located outside of the end surfaces of the rods 25. Due to this arrangement light coming from a light layer corresponding to that indicated as 11 in FIG. I, or from another source, can penetrate only at the ends of the rods 25'and can be further transmitted without disturbance.

It is apparent that the present invention covers not only the described plates and methods of making them, but also variations thereof within the scope of the appended claims. For example, the ground and polished ends of the rods can be glued upon a solid transparent plate, such as a supporting glass plate, and'then the wires can be removed.

We ciaim:

1. A process for making light-conducting plates particularly suitable for use in inlets of gamma cameras, said process comprising placing next to each other a plurality of transparent rods and locating between said rods distance holders consisting of wires of deformable material having a thickness greater than the length of the light wave to be transmitted, pressing together said rods and said wires, fixing by a casting mass at least one end of each of said rods, grinding and polishing said ends, removing said casting mass and the grinding and polishing means, then applying a foil to at least one front surface of the produced light-conducting plate, said foil having a thickness of 20 to 100p and filling spaces remaining between said rods with particles of a granulate, said particles having a large diameter relatively to the length of said light wave. r

2. A process in accordance with claim 1, wherein saidrods consist of glass, have a round cross-section and a thickness ranging from 1 to mm., preferably 7 mm., 4

and wherein said wires consisting of a deformable 6 metal, such as copper, and having'a diameter ranging between 0.2 to 0.5 mm.

3. A process in accordance with claim I, wherein said foil is applied at the light entry side of the lightconducting plate, the process comprising the further step of blackening said foil at parts located opposite the spaces between said rodsv 4. A process in accordance with claim 1, further comprising gluing said ground and polished ends of the rods to a solid transparent plate and then removing said distance holders.

5. A light-conducting plate made in accordance with the process described in claim 1.

Claims

1. A process for making light-conducting plates particularly suitable for use in inlets of gamma cameras, said process comprising placing next to each other a plurality of transparent rods and locating between said rods distance holders consisting of wires of deformable material having a thickness greater than the length of the light wave to be transmitted, pressing together said rods and said wires, fixing by a casting mass at least one end of each of said rods, grinding and polishing said ends, removing said casting mass and the grinding and polishing means, then applying a foil to at least one front surface of the produced light-conducting plate, said foil having a thickness of 20 to 100 Mu and filling spaces remaining between said rods with particles of a granulate, said particles having a large diameter relatively to the length of said light wave.

2. A process in accordance with claim 1, wherein said rods consist of glass, have a round cross-section and a thickness ranging from 1 to 15 mm., preferably 7 mm., and wherein said wires consisting of a deformable metal, such as copper, and having a diameter ranging between 0.2 to 0.5 mm.

3. A process in accordance with claim 1, wherein said foil iS applied at the light entry side of the light-conducting plate, the process comprising the further step of blackening said foil at parts located opposite the spaces between said rods.

4. A process in accordance with claim 1, further comprising gluing said ground and polished ends of the rods to a solid transparent plate and then removing said distance holders.