Distance measuring device

A distance measuring device comprising:

• transmission means for intermittently transmitting measuring waves of constant frequency toward and object;
• a pair of reception means spaced from each other in a direction of the object by a predetermined distance which is an odd integral multiple of half the wave length of the measuring waves, each reception means of said pair of reception means receiving reflected waves of the measuring waves from the object and outputting a reception signal responsive to an amplitude of the received reflected waves;
• a pair of peak detection means, each detection means of said pair detecting a peak of the reception signal outputted by each of said pair of reception means and transmitting a reflected waves reach signal at the time of peak detection;
• a pair of return time operation means, each calculating a measuring wave propagation return time taken from the time when the measuring waves are transmitted by said transmission means to the time when the reflected waves reach signal is outputted;
• addition means for adding the return times calculated by each of said pair of return time operation means to each other;
• and
• distance operation means for calculating the distance to the object based on the added return times.