Object detecting system of reflection type

An object detecting system of reflection type comprising:

• a ultrasonic wave generating means adapted to generate ultrasonic waves;
• a driving means adapted to drive said ultrasonic wave generating means;
• a ultrasonic wave receiving means adapted to receive ultrasonic waves and disposed a predetermined space from said ultrasonic wave generating means;
• an amplifying means adapted to amplify a signal from said ultrasonic wave receiving means;
• an object discriminating means adapted to discriminate the presence or absence of objects in accordance with a level of the signal obtained from said amplifying means;
• and
• an electronic control unit which energizes said driving means for a certain period of time and then reads a first signal from said object discriminating means at a predetermined timing in accordance with the distance between said ultrasonic wave receiving means, which judges the system to be abnormal when ultrasonic waves are not detected and again energizes said driving means when ultrasonic waves are detected, to change at least one of an energized level of said driving means, a gain of said amplifying means and a discrimination level of said object discriminating means, when said object discriminating means Judges that there exists no object, and which calculates the distance in accordance with a time period from the energization of said driving means to judgement by said object discriminating means to indicate the presence of objects, when said object discriminating means generates a second signal indicating that there exists some object.