GB1526091A - Display apparatus - Google Patents

Abstract

1526091 Control of displays DATA RECORDING INSTRUMENT CO Ltd 19 Feb 1976 [21 Feb 1975 (2)] 7290/75 and 7298/75 Heading G4H An interactive display comprises an array of discrete display elements 300 each producing an optical output in response to a drive input, labelling giving each element an independent significance, means 101 for storing a plurality of bits each associated with a different element 300, means 140, &c. responsive to the values of the stored bits for generating and supplying to each element as its drive input either a first or a second time-varying waveform, depending on the value of the stored bit, to cause the element to be in first or second visually distinct display states, both waveforms containing a signal identifying that element by its timing, sensing means 70 movable by an operator over the array to sense light from a selected element, and means 202 responsive to means 70 and capable of inverting the value of the associated bit. Elements 300 are LEDs (they may be liquid crystals) and means 70 is a phototransistor in a light pen 60. Means 101 is a recirculating shift register storing a 1(0) if the corresponding element is to be on (off), e.g. b, Fig. 3. The bits in register 101 are normally recirculated via gating circuit 202, Fig. 5, under the control of an oscillator 150 whose pulses a also control row and column addressing circuitry 170-280 and a pulse generator 160 whose output c is combined with the shift register output b in OR gate 140 to give an enabling pulse train 250 (e.g. d) containing long and short pulses for elements which are to be on and off respectively. To change the state of an element, a bistable 100 is set in the appropriate state and light pen 60 is placed on the diode. The light pen output blocks gate 450 at the appropriate moment so that a pulse is added to or removed from the circulated pulse train 30 via gate 430. In a second embodiment (Fig. 6, not shown) the arrangement of Fig. 2 is modified to cope with displays having large numbers of diodes by introducing extra energizing pulses in the waveform applied to each bit diode. The labelling of the diodes is effected by means of an interchangeable partially transparent cardboard overlay (Figs. 8 and 9, not shown) which enables the display to be used with a mini-computer for information retrieval from microfilm or a disc file.