GB799767A - A test pattern attachment for a television camera - Google Patents

Abstract

799,767. Photo-electric measurement of light intensity; television. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Sept. 26, 1956 [Sept. 29, 1955], No. 29391/56. Class 40 (3). Relates to an accessory for use with a television camera, comprising a tubular body 1 adapted to fit in a lens mount 2 in the camera and containing an electric lamp 8 to illuminate a picture, such as a test pattern, in the form of a transparency which may be inserted in an aperture 4. In accordance with the invention, the current through the lamp is controlled by a potentiometer 6 and there is provided a milliammeter 9 connected with a photo-electric cell 11 which may be inserted in the light path to the camera to furnish a measure of the light intensity. The potentiometer may thus be adjusted to compensate for variations in the light due to supply voltage variations, ageing of the lamp, and cleanliness of the bulb, and possibly also cleanliness of the transparency, if this is included when the measurement is made. Reference is also made to an arrangement in which the photo-electric cell may be positioned beyond the projection lens 12 so that soiling of this may also be compensated for by the lamp adjustment. The photo-electric cell is pivoted about a shaft 15, to which a lever 16 is also secured, and is normally held out of the light path, if necessary by means of a spring, but may be inserted in the light path by displacing the lever through 90 degrees. Power for the lamp may be obtained from the camera supplies by means of spring contacts, such as 17, arranged to engage contacts on the camera case.