GB805281A - A new or improved device for distinguishing visual patterns - Google Patents

Abstract

805,281. Photo-electric record sensing apparatus. SMITH, A. B. March 11, 1955 [Jan. 12, 1954], No. 829/54. Class 40 (3). Symbols on a proof sheet 16 (Fig. 1) are recognized by means of a continuous rotating disc 19 which bears on it a circumferential row of characters corresponding to those to be found on the proof sheet. These characters are dark on a light background but the reverse arrangement is possible. Light from a source 10 projects the image of a character on to the proof sheet and light received by a photo-electric cell 18 is a maximum when the two characters are the same. When this occurs a gas-filled relay 30 (Fig. 3) is triggered to print a code 38 corresponding to the character recognized on a photographic strip 35. In order that the same amount of light may be passed by each character on the disc a second translucent portion 24 (Fig. 2) is provided whose area is an inverse function of that associated with the symbol 22. A reflecting baffle 26 is provided to mask areas of the proof sheet adjacent the character being recognised and the baffle may be partly masked by an adjustable reflecting shutter 27 which may cut off the image 29 of " make weight " 24 to take account of different paper. When thyratron 30 fires to print the code 38 on the photographic tape it operates relay 31 to cut off the anode supply to the thyratron to terminate the firing and to energize magnetic clutch 39 which is held energized by a second winding of relay 31 until the circuit of this winding is opened once per rotation of a circuit breaker 42 connected to the proof carriage. The amount of movement given to the proof carriage is varied according to the period for which the clutch is energized by rotating switch 32 which connects a number of resistors 40 successively in series with the clutch according to the size of the character printed to step the proof carriage on an appropriate amount. If the proof carriage moves continuously it may be geared to advance during each revolution of the forme carriage, the formes being spaced progressively farther apart. The photo-cell may be connected to the gas-filled tubes through amplifier stages which may operate as the critical stage to detect the amplitude of the signal from the photo-cell instead of the gas-filled tube. To avoid integration of the signal, the photo-cell should be directly coupled to the first stage. A separate flash tube may be used for the photographic printing instead of tube 30. A system using both positive and negative forme symbols may be used having two photo-cells arranged in a bridge or with an output arranged to cut off two triode valves having a common anode resistance across which is a relay stage.