GB650455A - Improvements in photographic recording - Google Patents

Abstract

650,455. Infra-red photography. URBACH, F. March 25, 1947, No. 8157. Convention date, March 26, 1946. [Class 98 (ii)] [Also in Group XL (a)] A method of infra-red photography comprises exciting uniformly with short wavelength radiation a layer' of a phosphor which stores the excitation energy and releases it trigger fashion when stimulated with infrared light between 0.8 Á and 2.0 Á as light of wavelengths intermediate the exciting and stimulating wavelengths, placing the uniformly excited phosphor in printing relation to a photographic layer sensitive to said intermediate wavelengths, stimulating imagewise the phosphor with the infra-red light and processing the photographic layer to yield a visible record. Numerous examples of suitable phosphors are given in the Specification. As shown, the phosphor 10 on a transparent support 11 is excited uniformly by ultra-violet light and after the spontaneous emission has ceased is stimulated image-wise by projecting on to it by means of a lens 22 the image of an object 21 illuminated by infra-red light from lamps 20, the infra-red light causing the phosphor to emit visible or near ultra-violet light which is recorded on an orthochromatic emulsion by projection through the support 11 or directly from the phosphor. In the latter case the emitted light may be focused by the lens 22 after reflection by a dichroic mirror 30 transmitting infra-red either directly or with an additional lens 33 on to an emulsion at 31, or reflected by a similar mirror arranged instead at 35 to a camera, or directly recorded by a camera arranged with its axis at a small angle to that of the infra-red system. Alternatively the infra-red image may be formed on the phosphor after passing through the support 11 and the light emitted recorded on a photographic material with its emulsion in contact with the phosphor. Such a method may be employed for obtaining infra-red spectrograms. The phosphor may be in the form of an endless band 74 moved intermittently past an ultra-violet source 75 and an infra-red image of an object 21 projected on to it at 72 by way of a dichroic mirror 70 and a lens 71, the infra-red and ultra-violet being prevented from reaching the same part of the phosphor simultaneously by a shield 77. The light emitted by the phosphor is transmitted by the mirror 70 and recorded at 81 in a camera. This arrangement may be employed when phosphors are used which operate at low temperatures, e.g. of liquid air, when the whole chamber 76 is brought to the required temperature. Specifications 650,458 and 650,459, [both in Group XL (a)], are referred to.