| 摘要 |
1,254,624. Cathode-ray tube displays. ALPHANUMERIC Inc. 8 Aug., 1969 [8 Aug., 1968], No. 39822/69. Heading H4T. [Also in Division G1] In an arrangement in which patterns (e.g- Alpha-Numeric symbols, Fig. 2) determined by control signals operative on the vertical and horizontal beam deflection means are " painted " on the screen of a cathode-ray tube CRT (Fig. 1) and optically directed on to a record medium RM, the directions and magnitudes of the deflections required for (each limb of) the symbols are derived from a Data Source DS and set up in registers in the vertical and horizontal deflection control circuits VDC, HDC in terms of co-ordinate positions in an arbitrary grid (16,384 horizontal positions and 255 vertical positions, as seen on the CRT screen), the registers feeding comparators which also receive inputs from further registers in which the actual grid-point movements of the beam as determined by vertical and horizontal position transducers VIT, HIT responsive to beam movement are set up in similar terms the comparators operating whilst inequality exists between the two inputs to to supply output signals (the control signals) to cause the vertical and horizontal deflection generators to produce the deflections required to " paint " the symbol. The beam is thus precisely positioned during each deflection movement and if, e.g., due to pin-cushion distortions, a deflection movement of the beam occurs which is not set up in the register by the Data Source DS the detection of this movement by the appropriate transducers VIT, HIT causes a correction deflection movement to be imparted to the beam. The transducers VIT HIT each comprise, as shown in Figs. 1 and 3, in respect of transducer VIT a pair of photo-sensitive elements PE1, PE2 screened from each other by means of a baffle 18 and each receiving through a grating 12 a respective one of beams B8, B9 with the relationship shown in Fig. 3 so that a known signal processing circuit 20 is enabled to produce a pulse signal V1 indicative of each incremental movement of the beam (equivalent to one grid position) and a signal VS indicative of the sign (direction of the beam movement). The image light is directed to the recording medium RM via a polarizer PZ and a pair of Kerr cell type shutters KS1, KS2 which may be operated selectively and allow a greater width (vertical dimension of the RM as seen in Fig. 1) of the recording medium to be utilized. |
