Abstract:
An optical device for viewing a sample contained within a holder (e.g., pair of glass slides), featuring an array of lenses and a collimating plate for illuminating spaced-apart narrow areas of the sample, and another lenticular array and collimating plate for viewing the illuminated areas.

Description:
This application is a continuation-in-part of my U.S. patent application Ser. No. 859,278 filed Dec. 12, 1977 now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to optical devices for viewing a thin sample layer contained between two semitransparent layers. 
     BACKGROUND OF THE INVENTION 
     It is often desirable to make a wide area photograph of a frail specimen (e.g., a very thin slice), which must be supported inside a holder of some kind, such as between two microscope slides. Such frail specimens include extremely thin slices (e.g., 0.5 microns), in which the holder is needed for mechanical support, or materials prone to corrosion, in which the holder provides an environmental seal. Because such a specimen cannot be placed in direct contact with film or with a fiber-optic plate, contact prints cannot be made. Instead, photographs are made using a camera held at a suitable distance (for focusing) from the specimen and holder. 
     SUMMARY OF THE INVENTION 
     I have discovered a means for making contact prints of specimens while they are contained within semitransparent holders, thus allowing prints to be made with much more compact apparatus than heretofore possible. My invention has application whenever it is desired to view a selected thin layer surrounded on two sides by semitransparent layers. The invention features an array of elongated lenses and a collimating plate for illuminating spaced-apart narrow areas of the selected layer, another lenticular array and collimating plate for viewing light differentially transmitted through the narrow areas, and means for forming images of the narrow areas from the light emerging from the second collimating plate. 
     In preferred embodiments, the elongated lenses are plano-convex, with the planar surfaces facing the semitransparent layer; a third array of elongated lenses focuses light emerging form the second plate onto a plurality of image areas corresponding to the narrow areas of the selected layer; means are provided for moving (e.g., reciprocally) the viewing and illuminating elements relative to the selected layer by a distance greater than the spacing between the narrow areas, to provide sequential images of all the narrow areas making up the entire selected layer; the collimating plates consist of microchannel plates with a light-absorptive coating on the interior walls of many fine-diameter channels; the microchannel plate is about 100 times as thick as one channel diameter; and the lenses are about as thick and wide as the microchannel plate is thick (e.g., about 2 to 3 mm). 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     I turn now to the description of the structure, manufacture and operation of a preferred embodiment of the invention. 
     FIG. 1 is a cross-sectional, partial view of said preferred embodiment. 
     FIG. 2 is a diagrammatic view of said embodiment with the addition of a light source and a means for moving the device relative to the specimen. 
    
    
     STRUCTURE 
     In FIG. 1 there is shown a small portion of optical device 10 adjusted to view planar specimen 12 through glass slides 14, 15. Slides 14, 15 are each 1 mm thick, measured between their parallel, planar outer surfaces 16, 18 and 17, 19, respectively. Specimen 12 is on the order of 0.5 microns thick. 
     Lenticular arrays 20, 22 abut outer surfaces 16, 17 of slides 14, 15. Microchannel collimating plates 24, 26, each having parallel, 25 micron diameter, collimating channels normal to their exterior surfaces 27, are adhesively bonded to the outside of arrays 20, 22 along tangent lines 28. Third lenticular array 30 is similarly bonded to the other side of plate 26. Each lenticular array is composed of a multiplicity of elongated lenses 32, 33, each lens being of uniform cross-section along its length and having a surface 36, a portion of a cylinder (2 mm radius) and three planar portions (two a portion 34 and one a portion 38), and being adhesively bonded to adjoining lenses at surfaces 34. The lenses of each array 20, 22, 30 are registered with the lenses of the other arrays; i.e., corresponding tangent lines 28 on the arrays are aligned so as to define single planes that are perpendicular to specimen 12. Arrays 20, 22 have a thickness measured between tangent lines 28 and planar surfaces 38, of 1.88 mm. Array 30 is thicker, its width being chosen, as explained further on, to focus light at output surface 42. The individual lenses of all arrays are 3 mm wide, measured between opposing surfaces 34. Plates 24, 26 are 100 channel diameters thick, which is 2.5 mm. All arrays are made from standard fiber-optic glass having a 1.8 index of refractivity. 
     MANUFACTURE 
     Manufacturing techniques known in the art are used. Individual lenses 32 (or groups of lenses) are drawn from core bars having shapes similar to the lenses. The drawn lenses are then assembled and bonded together, using techniques known in the art for assembling fiber-optic ribbons. 
     The microchannel plates are prepared as described at page 592 of Wiza, J. L., &#34;Microchannel Plate Detectors,&#34; Nuclear Instruments and Methods, vol. 162, pp. 587-601, North-Holland Publishing Co., which is hereby incorporated by reference. One step of the manufacturing process is to reduce the plates in a hydrogen furnace. This has the effect of blackening the interior walls of the microchannels and thereby giving the walls a light-absorptive coating. 
     OPERATION 
     Collimated light produced by passing light through collimating plate 24 is focused by lenticular array 20, which is designed taking into account the refractivity of air slides 14, 15, onto a spaced plurality of narrow areas or lines 40 on specimen 12. These narrow areas are no wider than about 50 microns, which is the smallest dimension that is ordinarily resolvable by the unaided human eye. Further reductions in the widths of these areas could be made if the image produced is to be magnified when viewed. Light paths 44, 46 diagrammatically illustrate the device&#39;s operation for one viewed line. The spacing between lines 40 is the 3 mm lens width. Light passes through the lines 40 by differential transmission, and external images 60 of the lines are provided on output surface 42 by the combination of lenticular arrays 22, 30 and collimating plate 26. Light paths 45, 47 illustrate the operation. Principally, only the differentially-transmitted light emanating from lines 40 is passed by collimating plate 26; other light is absorbed by the non-reflecting walls of the microchannel plate because it does not impinge on the plate parallel to the collimating channels. 
     At any one time the view of specimen 12 is confined to a single set of lines 40. Further sets of lines making up the full image of the specimen can be viewed by moving the device sideways relative to the specimen while constantly viewing, as shown diagrammatically in FIG. 2 (in which there is shown means for moving elements 24, 20, 22, 26, and 30 relative to the specimen). Movement greater than the 3 mm line spacing will produce a sequential view of all sets of lines on the planar portion. 
     OTHER EMBODIMENTS 
     Other embodiments are within the scope of the description and claims. For example, other holders than glass slides could be used, e.g., any semitransparent material not exhibiting an excesssive amount of light scattering. Similarly, low-scattering, semitransparent materials, such as oil, could be used in contact with the specimen between the slides. Also, the movement of the device relative to the object could be done rapidly (e.g., 50 Hz oscillation of 6 mm amplitude) to make the shifting line images appear to the human eye as a steady image of the entire specimen.