GB1431280A - X-ray image converter - Google Patents

Abstract

1431280 Cathode-ray tubes PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 30 July 1973 [2 Aug 1972] 36139/73 Heading H1D [Also in Divisions H3-H5] A device for converting an X-ray image incident at a window 19 to a visible image viewed via a window 18, comprises a transparent electrode 3, a variable birefringent electrooptic plate 1, an electrically insulating layer 4 reflective to the viewing light, e.g. a multilayer dichroic mirror, a photoconductive layer 5 and an electrode 6 transparent to a radiation image which is derived from, or provided by, the X-ray image, and to which layer 5 is sensitive. In use a potential difference is applied between electrodes 3 and 6. In Fig. 2 an X-ray responsive phosphor layer 7 is provided. In variant embodiment, layer 7 may be disposed closely adjacent to electrode 6 but supported separately, Fig. 3 (not shown), a special support or the window 19 may be used or it may be disposed on a fibre optic plate for optical coupling to layers 5 and 6, Fig. 4 (not shown). In Fig. 1 (not shown), layer 5 is itself responsive to X-rays and layer 7 is omitted. In Fig. 6 electrons from a photo-cathode responsive to radiation emitted from an X-ray sensitive phosphor 12 are focused 13 on to a cathodeluminescent phosphor 10. The image therefrom is coupled to layer 5 via a fibre optic plate 9. A metallic layer 14, e.g. of aluminium is deposited on phosphor 10 and may be at the same potential as electrode 6. In both Figs. 2 and 6 the enclosure 21 is evacuated. In Fig. 6 it is separated from the enclosure A by a wall 22 and may be at a somewhat higher pressure relative to enclosure A. In Fig. 5 (not shown), wall 22 and plate 9 are omitted, the phosphor 10 being deposited on electrode 6. In Fig. 7 (not shown), enclosures 21 and A are physically separate, the plate 9 being replaced by two abutting fibre optic plates sealing the ends of the respective enclosures. The birefringent image produced in plate 1 is read out by a polarized light beam which may be coherent. The image is erased by uniformly illuminating photoconductive layer 5 with suitable radiation via either of windows 18 and 19 or by a source within enclosure 21, simultaneously reducing the potential difference between electrodes 3, 6 to zero. Plate 1, e.g. of KDP or KD*P, is at a temperature near its Curie point.