Patent GB-1114162-A (GB)
Title: An arrangement for reinforcement of the intensity of optically produced images
IPC: G02B27/00
Filed: 1965-09-10
Abstract: 1,114,162. Light modulators. GESELLSCHAFT ZUR FORDERUNG DER FORSCHUNG AN DER EIDGENOSSISCHEN TECHNISCHEN HOCHSCHULE. 10 Sept., 1965 [24 June, 1965], No. 38774/63. Heading H4F. [Also in Division H1] Relates to an improvement in a device for increasing the intensity of an image such as that disclosed in Specifications 741,154 and 987,867, where the image is employed to cause deformation of a control layer bearing a reflecting surface which is located in a Schlieren optical system for modulating the light from a separate light source. The control layer, which is elastically deformable under the effect of an electrostatic field, is subjected to an electrostatic field provided by a potential source connected between a pair of electrodes and the deformation is effected by including a photoelectric layer which is illuminated by the image via an opaque line grating or raster and produces variations in the electrostatic field in correspondence with the resistance variations imparted by the image. In accordance with the invention the control device 6, Fig. 1, not shown, comprises a first transparent carrier plate 11, Fig. 6, provided with an opaque line grating 12, a transparent electrically conductive electrode sheet 13, a photo-electric control layer 14 which consists for example of selenium, two electrically insulating, elastically deformable layers 16a and 18 separated by a liquid reflecting layer 17a which consists preferably of a metal or a metallic alloy, and a second transparent carrier plate 20. An alternating voltage source 21 is connected across the electrode plate 13 and the electrically conductive reflecting layer 17a in order to establish a time-varying electrostatic field transversely to the photo-electric control layer 14 and the deformable layer 16a. This electrostatic field is modulated by the variable resistance of the photo-electric layer 14 as a result of its illumination by the image, and this modulated alternating electrostatic field causes a pulsating field at the surface I. The point for point distribution of this pulsating field is transmitted transversely across the reflecting layer 17a on to the surface II which is thus deformed into a diffraction grating by the resultant pressure distribution which reflects the light from the light source 3 which has been reflected by the bars 4 of the Schlieren optical system, so that it passes between the bars 4 and an image is formed on a projection screen P, Fig. 1, not shown. Layers 16a and 18 may comprise a silicon polymeride base with an added plasticizer. Deformable layer 16a is preferably opaque to the light which provides the image to be intensified on the photo-electric control layer 14, in order to prevent disturbing illumination of the photo-electric control layer 14 by reflection of this light at the surface I of the reflecting layer 17a. In a second embodiment, Fig. 7, not shown, the photo-electric control layer 14 and the adjacent elastically deformable layer 16a are replaced by a single layer (14b) which has combined the photo-electric control properties of the layer 14 and the mechanical properties of the layer 16a. The improvements described in the present Specification may be applied to the device shown in Fig. 5 of Specification 987,867 with only one of the two voltages U 1  and U 2  made an alternating voltage to make the electrostatic field acting on the surface I of the liquid reflecting layer vary with respect to time.