| 摘要 |
PURPOSE:To set a laser distance measuring device to optimum sensitivity automatically according to the level of background light by measuring the amount of noise in a receiver output in a time zone except a distance measurement period, and adjusting the reception sensitivity automatically. CONSTITUTION:A gate circuit 9 is opened in a laser distance measurement interruption period which extends from the laser emission of a laser oscillator 1, etc., by the specific reception time lapse of a receiving optical system 4. Then, the noise in the output of a variable gain video amplifier 12 is supplied to a detecting circuit 10 and the amplifier 12 is brought under feedback control through a holding circuit 11 to adjust the reception sensitivity automatically so that the amount of receive noise is nearly constant. Therefore, the reception sensitivity of the laser distance measuring device is set to the best value automatically; even when the receiving optical system has a large diameter, the sensitivity is displayed sufficiently with the small quantity of background light and there is no malfunction due to noise at the time of an increase in the quantity of background light. |
