GB664362A - Improvements in radiation-detecting devices - Google Patents

Abstract

664,362. Infra-red detectors. OFFICE NATIONAL D'ETUDES ET DE RECHERCHES AERONAUTIQUES. July 1, 1948 [July 4, 1947], No. 17740/48. Class 40 (iii). [Also in Group XX] A device for detecting infra-red radiation comprises reflecting or refracting elements for concentrating the radiation into a portion of space occupied by a medium of given refractive index so as to modify this index, and a phase contrast optical apparatus is disposed so that said portion of space.is located across the path of a light beam passing through said apparatus whereby the latter indicates the presence of infra-red rays. As shown in Fig. 1, light from a source 1 is collimated by a lens 2 and is focused by a lens 3 on to an opaque screen 4, adjacent which is a lens 5. A parallel beam of infrared rays is refracted into the focal plane P-P of lens 2 so that the refractive index in a zone 7a thereof is modified and diffraction of the rays from source 1 passing through this zone occurs. These diffracted rays pass through lenses 3 and 5 so that an image 0 of source 1 is focused on a screen P<SP>1</SP>-P<SP>1</SP>, this image indicating that infra-red radiation is concentrated on zone 7a. The screen P<SP>1</SP>-P<SP>1</SP> may be of the usual kind or may be replaced by a photographic plate, a photo-electric cell or a bolometer. The air layer in plane P-P may be replaced by a transparent plate or by a fluid held between two transparent plates. In another form, the beam of infra-red rays is concentrated by a concave mirror on to an air pocket and causes diffraction of part of the beam from a light source placed near the centre of curvature of the mirror. The air pocket may be formed by a sleeve attached to a transparent plate. Alternatively, air pockets may be arranged in the form of a honeycomb structure and the radiation concentrated thereon. In the form shown in Fig. 3, light from source 1 is collimated by lens 2 and passes into an internally reflecting prism 81 separated by a small air space from a second internally reflecting prism 8 whereby the light is directed through a lens 3 and is focused on an opaque screen 4. A mask 9 is disposed between prisms 8 and 81 and a beam of infrared rays is directed through an aperture 9‹ in the mask to cause diffraction of part of the light beam, which part is focused by lenses 3 and 5 on a photo-electric cell 10. In another arrangement, the diffracted light is focused by lens 5 on an iconoscope, the output of which is amplified and transmitted to a cathode-ray tube. The Specification as open to inspection under Sect. 91 refers also to the detection of ultraviolet rays, sound and X-rays and to the detection of stresses and electronic bombardments. This subject-matter does not appear in the Specification as accepted.