A flip-flop sensor array with on-spot A/D conversion

A two-dimensional optical flip-flop sensor array, consisting of an 8×8 matrix of flip-flop sensors integrated in one chip together with sense amplifiers and access selection circuitry, is discussed. A flip-flop sensor contains two phototransistors, one of which is covered over the aluminum while the other is exposed to light. Each flip-flop senses the light intensity and converts it to a series of ones and zeros. It is operated by turning the supply current on and off with a high frequency. During the absence of light the flip-flop is totally symmetrical and the number of ones and zeros is equal. Light causes an asymmetry in the flip-flop that changes the ratio of ones and zeros. A fully digital output is obtained by counting the number of ones. A triangle-wave voltage is applied to the flip-flop to vary its threshold. The device showed that a large array of sensors with on-spot A/D (analog-to-digital) conversion can be realized using the flip-flop sensor technique