BACKGROUND

1. Technical Field

The disclosure relates to an ultrasonic object detector.

2. Related Art

A transmission/reception ultrasonic object detector has been known. In such a type of object detector, an oscillator having transmitted a transmission wave, which is an ultrasonic wave, receives a reflected wave. In driving the oscillator for transmission of the transmission wave, reverberation occurs in the oscillator after termination of driving. The energy of the reverberation is considerably larger than the energy of the reflected wave. Accordingly, a device for detecting an object at a distance short enough for the reflected wave and the reverberation to overlap is required.

SUMMARY

The present disclosure provides an object detector. One mode of the present disclosure is an object detector provided with an acquiring unit, a fall identifying unit, a rise estimating unit and a distance determining unit. The acquiring unit acquires an oscillation signal corresponding to an oscillation of a microphone, the microphone transmitting a transmission wave, which is an ultrasonic wave, on a basis of a driving signal, and being caused to oscillate by a reflected wave generated as a result of the transmission wave being reflected from an object. The fall identifying unit identifies a fall time point of a first drop from a value more than a threshold to the threshold or less after termination of the driving signal. The rise estimating unit estimates a rise-in-reverberation time point of the reflected wave, the rise-in-reverberation time point being before the fall time point and after a time point of start of the driving signal. The distance determining unit determines a distance to the object on a basis of the rise-in-reverberation time point.

