| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect the distance to an object by judging whether transmitted sound waves are reflected from an object and are received by a sound wave reception part or not by transmitting the sound waves from a sound wave transmission part to the object for a fixed amount of time. SOLUTION: A sound wave transmitter 11 transmits sound waves into room space only for a time T1 due to the control of a central processing device 10. It is judged whether transmission sound waves are reflected from an object and sound waves at least with a fixed strength are received by a sound wave receiver 13 or not. When no sound waves are received, a judgment regarding whether sound waves at least with a fixed strength are received by the sound wave receiver 13 or not is repeated until T1 passes. On the other hand, when no sound waves are received and the fixed amount of time T1 passes, sound waves are transmitted from the sound wave transmitter 11 again. After the time T1 passes, sound waves after sound waves with a long duration being transmitted are reflected and returned are received by the sound wave receiver 13, thus judging whether the sound waves at least with a fixed strength are received or not. When sound waves at least with a fixed strength are received, distance is calculated from the transmission/reception time and a distance detection routine is completed. |
