Patent GB-1054818-A (GB)
IPC: G02F1/31
Abstract: 1,054,818. Deflecting light. INTERNATIONAL BUSINESS MACHINES CORPORATION. Oct. 14, 1965 [March 1, 1965], No. 43568/65. Heading H4F. Light from laser 53<SP>1</SP>, Fig. 1, which is plane polarized by polarizer 56 is deflected by means of electro-optic light deflection stages 4, 6, 8, X which are operable to deflect light vertically distances increasing by a factor of two, the output position of the light being representative of the sum of the deflection values for the stages which are made effective by closing the switches 30, 32, 34, 36X. The deflection stages include birefringent crystals 10, 12, 14 and 16X and electro-optic devices 18, 20, 22 and 24X each comprising an electro-optic crystal between a pair of transparent electrodes which effectively rotates the plane of polarization of the plane polarized input light by 90 degrees when the potential from source 38 is applied thereto by closure of a switch. To provide deflection stages increasing by a factor of two, the thickness of the birefringent crystals must increase by the same factor. " Exclusive-or " circuits 40, 42 and 44X are connected as shown, and with switch 30 closed, as shown, electrooptic device 18 is energized, causing the light beam to be deflected in crystal 10, and a voltage is applied to " exclusive-or " circuit 40 which "with switch 32 open, energizes electro-optic device 20 causing it to effectively rotate the plane of polarization 90 degrees back to its original plane so that it is not deflected in crystal 12. If switch 32 had been closed there would be no voltage applied from the " exclusive-or " circuit 40 to the electro-optic device 20 and the polarization of the light would have remained in the plane to which it was effectively rotated by device 18 and the light beam would be deflected in crystal 12 as it was in crystal 10. The total value of the light deflection is equal to the total of the values assigned to the switches which are closed and thus with switches 30 and 34 closed, as shown, the total light deflection is five units since crystal 10 produces a deflection of one unit while crystal 14 produces a deflection of four units. In a second embodiment, Fig. 2, not shown, the three vertical deflection stages as shown in Fig. 1 are followed by three horizontal deflection stages which have their birefringent crystals turned 90 degrees relative to the birefringent crystals of the vertical deflection stages. It is necessary to locate a half-wave plate between these vertical and horizontal deflection stages. In a third embodiment, Fig. 3, not shown, each of the birefringent crystals in the system of Fig. 1 are the same thickness and with this arrangement the output point of the light beam from the last deflection stage is representative of the number of ones in a binary number assuming that the switches at positions corresponding to the binary ones are closed while those at positions corresponding to binary zeros are left open. In a fourth embodiment, Fig. 4, not shown, the output position of the light at the last stage is representative of the sum of two binary numbers, the arrangement comprising two sets of deflection stages, each set including birefringent crystals increasing in thickness by a factor of two. The two sets of stages may be interspersed or arranged with one set following the other.