| 摘要 |
PURPOSE:To reduce the influences due to the variation of electric power to television pictures by generating ultrasonic waves during the blank time of vertical synchronizing signals of a video camera. CONSTITUTION:When a vertical synchronizing signal generated always from a video camera is inputted as a clock of a divider 1, the signal is divided and divided signals are outputted to respective terminals Q0-Qn. These outputs determine transmitting periods and each output is selected in accordance with a required distance measuring limit. If Q1, 1/4 output, is used, a delay pulse in accordance with the transmission time is generated by the rise of an output from the terminal Q1 and the resetting status of the divider 4 is released during the time. Thus, a divider 4 divides an output from an oscillator and sends ultrasonic signals to a driving circuit by the delay pulses. The period from the start of the transmission of the ultrasonic signals to the end is included within the blank time of the vertical synchronizing signal, preventing pictures from the direct influences of electric power variation. |
