| 摘要 |
1,104,163. Optical information storage system. INTERNATIONAL BUSINESS MACHINES CORPORATION. 11 Oct., 1966 [14 Jan., 1966], No. 45364/66. Heading G4A. An optical information storage system includes scanning means responsive to binary address signals for illuminating a selected area of an optical information record by deflecting a light beam appropriately over the record, and monitoring means responsive to the parity of each address applied to the scanning means for subtracting the emanation from the selected area of the record from that from another similar area of the record to provide an information indicating output. High intensity light from a monochromatic light source 10 is passed through a collimating lens 12, through a linear polarizer and through an aperture in a plate to a first unit 14 of a light deflection unit 14 including a plurality of deflection stages. Each stage comprises a birefringent means (22, Fig. 2, not shown) preceded by an electro optic element which provides an output beam polarized either in a first direction or a second direction at 90 degrees to the first, the birefringent means allowing one beam to pass through normally but causing the second beam to be diffracted and to leave the means at a position spatially separated from the first beam. Deflection stages are arranged in increasing order of deflection by a factor of two, the unit 14 causing deflections in the x position being followed by a unit 16 causing deflections in the y direction. An optical memory is then read by the light beam. The light beam is directed to the appropriate spot in the optical memory by X position address and Y position address signals which are converted into X and Y switch addresses by exclusive OR circuits 24, 28, an address of 111 requiring a diffraction of 7 positions thus requiring a switch address of 001 since the operation of the first electro-optic element will leave the beam polarized such that all succeeding birefringent means will cause diffraction of the beam. Examination of the switch addresses shows that the parity of the signal indicates from which quadrant of the memory the light beam will emerge, e.g. if the y parity is odd the light beam emerges from quadrant 1 or 2, if even from 3 or 4. Parity check circuits 30, 32 emit signals X1, X2, Y1, Y2 (X1, Y1 for even parity) which are applied to AND gates 50, 52, 54, 56 which indicate which quadrant the light beam is in. The four quadrants are examined by photo-cells 36, 38, 40, 42, one to each quadrant with the outputs of 38, 40, examining quadrants 2, 3 being applied to one difference amplifier 44 and the outputs of the other photo-cells being applied to a difference amplifier 46. It is assumed that the quadrants 1, 4 have the same noise signal produced by extraneous light, and similarly for quadrants 2, 3 so that the difference amplifier acts to subtract the signal due to noise from the data output signal. The resulting signal is then applied via inverters I, if necessary, AND gates 58, 60, 62, 64 and OR gates to the output. |
