GB1265731A - - Google Patents

Abstract

1,265,731. Cathode - ray tube displays. HARRIS-INTERTYPE CORP. 14 Jan., 1969 [4 March, 1968], No. 2252/69. Heading H4T. Alpha-Numeric characters are produced on a cathode-ray display tube by forming a lightspot on the screen and deflecting this spot in step-by-step fashion from one to another of a plurality of locations on the screen which, in the aggregate, form a desired character, the quantities required to produce such deflections being produced under the control of data which specifies each location with reference to the preceding location. The invention is described in the framework of the display system described in Specification 1,255,841, shown generally in Fig. 1, which discloses an Alpha-Numeric character display in which digital data representative of the various characters to be produced together with timing data and other control data are derived from a rotating optical record 10. To enhance the rate of access the data appertaining to each character is repeated a plurality of times in a circular track on the record and further improvement in the access rate is achieved by dividing the data for each character in each repetition into a plurality of sections, the start and end of each of which is identified by control data so that a character may be reproduced by utilizing the data from the various sections in any sequence (Figs. 2 and 3, not shown). Thus, the character " a " (Fig. 5), which is specified by data in three sections I, II and III having " start " coordinates X 1 , Y 1 , X 2 , Y 2 and X 3 , Y 3 respectively, may be formed by positioning the beam at any of the latter " start " co-ordinates and after forming that particular portion of the character, by forming the remaining portions in any order. In the present invention the beam 45 (Fig. 4) may be deflected only in the seven directions 0 to 6 shown. Initially, the beam is positioned of one of the " start " co-ordinate position, e.g. X 2 , Y 2 (Fig. 5) and thereafter instructions in serial form and supplied such as 2, 2, 2, 2, 4, 5, 5, 5, 5, 4, 2 ... &c. which, in this example would move the spot up the first and down the second line of elements immediately to the left of the vertical line dividing section II from section I. Each deflection comprises a unit step having a direction specified by the numerical value of the instruction (supplied in digital form) in accordance with the directions shown in Fig. 4 and Fig. 6 shows in enlarged form the sequence of deflection required to produce the portion of the character shown in the " box " 46 of Fig. 5. The overall system is described and details of the operation of the character generator 20 (Fig. 1) are given together with a table showing the sequence of operations in producing a character. The characters produced on the tube screen may be recorded by moving photographic film, the motion of which is controlled by the system.