A Flip-Flop Sensor Array with On-Spot A/D Conversion

A two dimensional optical flip-flop sensor array is presented. It consists of 64 flip-flop sensors, each of which contains two phototransistors with different light sensitivity. Each flip-flop sensor senses the light intensity and converts it to a series of "one" s and "zero"s. It is operated by turning on and off the supply current with a high frequency. During absence of light the flip-flop is totally symmetrical and as a result the number of "one"s and "zero"s is equal. Light causes an asymmetry in the flip-flop that changes the ratio of "one"s and "zero"s. A fully digital output is obtained by counting the number of "one"s. A triangle wave voltage is applied to the flip-flop in order to vary the threshold of the flip-flop. The device showed that a large array of sensors with on-spot A/D conversion can be realized using the flip-flop sensor technique.