Incremental encoder for measuring positions of objects such as rotating

Abstract

A circuit for determining each level transition of first and second two logic level input signals and their leading or lagging phase relationship at each level transition and comprising first and second signal level storage means each having first input means responsive to the first and second input signals, respectively, first output means, and clock input means and responsive to a clock signal supplied to the clock input means to cause the logic level on its output means to become equal to the logic level on its first input means. First and second Exclusive OR gates each have a first input means connected respectively to said first input means of said first and second signal level storage means, and a second input means connected respectively to said first output means of said first and second signal level storage means. A third Exclusive OR gate responds to equal or non-equal logic levels on said first output terminal of said first Exclusive OR gate and said second input signal to produce first and second logic level, respectively. Additional means respond to the outputs of said first, second, and third Exclusive OR gates to determine the relationship of said first and second input signals at each level transition thereof and to supply a clock signal to the clock input means of said first and second signal level storage means after said additional means determines the phase relationship between said first and second input signals.