Patent GB-911651-A (GB)
Title: Direct access photomemory for storage and retrieval of information
IPC: G11C13/04
Filed: 1960-04-22
Abstract: 911,651. Photographic data selecting devices. AVCO CORPORATION. April 22, 1960 [April 29, 1959], No. 14307/60. Class 97 (1). [Also in Group XL (b)] A system for storing a combination of a multiplicity of recorded information units comprises read out means, means for registering the units with the read out means by different permutations of three orthogonal translatory movements and digital servo means for controlling such movements by corresponding permutations of digital addresses, each permutation characterizing one of said units. As shown in Fig. 3 a panel 12 is divided up into a plurality of areas 14, 15 each of which constitutes an information unit and is characterized by two coordinates. As shown in Fig. 2, a main support member 48, capable of vertical translation along the Y-axis by servomotor 54, supports a framework and rails for the translational movement along the Z-axis, by a predetermined amount, of a carrier 10 containing a plurality of panels such as 12, and transfer means 16 for carrying a selected panel in translation along the X-axis by means of servomotor 45, until a pre-selected information unit is registered with the objective 57 which forms a magnified image of a micro-photograph constituting the information unit on a read out means 67 which may comprise an electronic scanning device including closed circuit television, or may be an optical viewing system. A digital address system selects the X, Y and Z co-ordinates and the corresponding orders are fed to a digital differencing unit 70 (Fig. 4) which receives = information from an analogue-to-digital converter associated with each axis of the Cartesian framework as to the present co-ordinate value. The difference between the latter and the commanded value is fed to the digital-to-analogue converter 71 as an error output signal and thence to the servomotor amplifiers via a gating circuit (details of which are given in the Specification) associated with each amplifier. A control system, generally indicated in Fig. 4 as a " sampling unit "102, comprises an oscillator which transmits sample pulses through a gate 92. (Fig. 7) The latter, together with a flip-flop, acts as a master switch for the sample pulses, after which they are directed along two routes each of which are divided into a further two subroutes. The two sub-routes of one main branch are coupled respectively with the Z-axis and Y- axis servo amplifier and address-system circuits; The two sub-routes of the other branch are coupled one to the servo amplifier and to the address-system for the Y axis and the other to the servo amplifier and to the address system for the X-axis. The coupling to the servo amplifiers is via the aforementioned gating circuits which are opened for the passage to the amplifiers of the error-signal from the differencing unit 70 when the sample pulse is applied. To begin with, Z and Y sample pulses are alternately fed along the respective sub-routes by means of a flip-flop coupled to a pair of " and " gates to allow the servomotors 38 and 54 to perform the commanded Z-movement of the carriage and Y-movement of the support 48. When the commanded Z-movement has been completed, the zero Z-error-signal produces a pulse which is applied to the flip-flop of the sampling oscillator gate whereby the Z-Y route is closed to the sample pulses and Y-X route is opened and servomotors 38 and 45 complete the registration of the selected information unit by alternate operation in the manner described. The zero error-signals for the Y and X operations are combined, with the aid of a delay circuit, to produce a single pulse on the flip-flop of the sampling oscillator gate which blocks the Y-X route and re-opens the Z-Y route for a further cycle of operations. The sample pulses in the various sub-routes are applied also to the corresponding elements of the digital address system and when a particular servo-amplifier gating circuit is blocked, the corresponding digital order is also uncoupled, by means of an " or " gate (shown at 111 in Fig. 7), from the digital differencing unit 70.