Patent GB-1356596-A (GB)
Title: Optical relays
IPC: H01J31/50
Filed: 1971-07-14
Abstract: 1356596 Electro-optic storage arrangements; modulating light PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 14 July 1971 [17 July 1970] 33059/71 Headings H3B and H4F [Also in Division H1] An optical relay comprises an evacuated tube with at least one window 11 transparent to luminous radiation, a ferroelectric plate 1 exhibiting an electro-optic effect maintained near its Curie-point temperature and having a double refraction variable with the voltage difference between its faces, transparent conductive layer 3, on the first major face of the plate, an insulating mirror against the second major face and a photosensitive layer 7 and a second electrode whereby information may be read out or displayed by reflection of a polarized light beam, and information stored by a scanning light beam to the photosensitive layer together with application of a writing voltage between layer 3 and the second electrode. Superposition of several images from different relays as for colour TV and uses of a relay as a memory, information being read by an optic scanning device, e.g. flying spot or a laser beam associated with a digital deflection system are exemplified. The laser may be Xe or Ar or a Hg lamp may be used. Target 1 with conductor 3 is glued to fluorite support 2 and coated with insulating mirror 4 and secondary emission layer 5. Anode grid 6 is a few tens of microns from target 1 to collect secondary electrons and photoemissive layer 7 may be deposited on second transparent window 8, distances being a mm. or fraction thereof to ensure proximity focusing, while filter element 9 effects cooling. From 200 to 2000 volts for instance, between layers 6 and 7 ensures focusing and in case of saturation the secondary emission of surface 5 is >1. Writing signal voltages and between grid 6 and layer 3, and the grid units must be smaller than or equal to the distance between two picture elements (#50 Á in the initial relay). In Fig. 2 (not shown), second grid (12) ameliorates the collection of secondary electrons, its potential being #50 volts higher than anode 6. To avoid moirÚ effects, grids with square meshes may be mutually orientated at 45 degrees and similarly, one square mesh and one bar grid, or two bar grid may be 90 degrees orientated. The above may include an image intensifier with luminescent layer and optical fibre window 8. The image intensifier included in Fig. 3 (not shown) comprises a thin glass sheet or disc of optical fibres (13), luminescent layer (14) on transparent conductive layer or covered by thin A1 layer, with photoemissive layer (15), layer 7 to 14 distance being a few mms. Further grid (12) may be included (Fig. 4, not shown). Alternatively, wafer (13) may be replaced by a wafer of electron multipliers, operating potential being disclosed. Fig. 5 (not shown) includes photoconductive layer (16) and in conductor (17) and despite absence of electron beam is operated in vacuum and reduces cooling problems may include an image intensifier (Fig. 6, not shown) with luminescent layer (14) and photoemissive layer following use of layer (16) sensitive to u.v. Separation of reading and writing beams may be achieved may be by using multipliers with microchannels at angle to the axis, by a sufficiently opaque mirror 4, e.g. a multi-dielectric and additionally a luminous radiation absorber on one side, or by different spectral bands for writing and reading. The writing band may be u.v. or near violet with a filter between dielectric mirror 4 and layer 5 (Figs. 1 to 4) or layer 16 (Fig. 15) or inside or outside the tube on the reading side, or a detector which is not sensitive to the writing band may be used. Insulating mirror 4 may be reflective and transparent to reading and writing beams respectively and may be multidielectric. Window 8 may then be omitted, reading and writing beams entering the same face via window 11. The same optic scanner may be used for writing and reading and may be a light deflection system, a laser emitting two wavelengths or two laser commutation reading-writing being by electrooptic Kerr or Pockels cells. Layer 17 (Fig. 5) need not be transparent, and support 2 may be replaced by opaque plate 18 (Fig. 7, not shown). Target 1 may be KD 2 PO 4 , described also in Specification 1,160,923 having a dielectric constant of 700 in the optic axis direction at - 55‹ C. The optic relay may be a high capacity memory used with a laser source controlled by a digital deflection system. Two identical light deflectors, or one deflector with polarization commutator and separator, allow beam switching.