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Display apparatus

  • US 3,894,292 A
  • Filed: 03/07/1973
  • Issued: 07/08/1975
  • Est. Priority Date: 03/10/1972
  • Status: Expired due to Term
First Claim
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1. Display apparatus in which the display comprises a raster of parallel lines and a symbol is displayed by changing a visual parameter of one or more selected portions of the raster lines comprising:

  • a. cyclic digital counter means operating in synchronism with the raster line scan so that successive counts of the counter correspond to successive sections of each raster line, thereby notionally dividing each raster line into sections respectively corresponding to different counts of the counter;

    b. means for producing digital outputs defining the position of each raster line portion required to be selected to display a required symbol, in accordance with the notional numbering of sections of the raster lines effected by the counter means;

    c. an output circuit comprising means for comparing said digital output with the output of the counter means to produce an output signal for changing said visual parameter when there is correspondence between said digital outputs and the output of the counter means; and

    d. delay means connectable to delay the output of said output circuit by a fraction of the period between successive counts of the counter means when a said digital output fractionally exceeds the corresponding count of the digital counter by a predetermined amount, thereby to effectively increase the number of sections into which each raster line is notionally divided.

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