To provide an efficient, economical and high precision pulse time difference encoding circuit as compared with a conventional one in which the circuitry can be simplified, complexy in production of hardware is solved and time difference between two pulse signals can be measured accurately.

The pulse time difference encoding circuit comprises a pulse circulation circuit having a series connection of 2n-1 NOT gates and one NOR gate where 2n-2 NOT gates excepting the final stage and the NOR gate are connected in ring, delay time is equalized in all NOT gates and delay time of the NOR gate is set two times as long as that of the NOT gate. When a second pulse signal is inputted and a measurement is outputted from a counter/encoder circuit, it is outputted from the counter/encoder circuit while being delayed by a predetermined time from input of the second pulse signal.

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