GB1338557A - Apparatus for use in viewing- x-ray images - Google Patents

Abstract

1338557 Viewing apparatus AGFA-GEVAERT 1 Jan 1971 [12 Jan 1970] 1470/70 Heading G2A and G2C An apparatus for viewing coloured X-ray images has a diffusing viewing screen illuminated by light which passes through a variable filter, the filter being movable so as to vary the spectral composition of the light falling on the screen. In the embodiment shown in Fig. 1, a housing 1 contains a number of tubular discharge lamps 2 emitting white light which passes through a diffusing screen 3 to illuminate an X-ray film 4 held against the screen. Supported within the housing is a fixed mask plate 6 and a filter plate 5 which can be displaced vertically by means such as an electric motor. Plate 5 has a series of obliquely disposed coloured filter bands as shown in Fig. 2, the bands being separated by grey filter bands having the same density as the coloured bands. The mask plate 6 has a similar pattern of silver reflecting strips separated by clear areas. In the position of Fig. 1, the coloured areas of the filter plate are in register with the clear areas of the mask plate, so that all the light passing through to irradiate the film 4 is coloured. The colour of the filter is chosen so as to be in a part of the spectrum complementary to that of the colour of the film 4. E.g. if the colour of the film is blue-cyan, the colour of the filter is orange-red. This increases the contrast of the image on the film, the image details represented by different colour densities showing up more clearly. As the filter moves downwards, an increasing proportion of the light reaching the film is unfiltered, i.e. white, until the filter areas are completely in register with the masking areas of plate 6, so that all the light reaching the film is white. Thus the film can be inspected by white light, or orange-red, or any proportion of the two together. Instead of the strip arrangement shown, the filter and mask areas may be in checkerboard pattern. Figs. (not shown) 3-6 are of alternative arrangements for varying the amount of illuminating light between entirely filtered and entirely unfiltered.