| 摘要 |
PURPOSE:To reduce the variance of an output and to prevent the influence by a reflection factor of an object by cutting a bias current of a logarithmic compressing part, when a variation portion of a photocurrent exceeds a prescribed value, and keeping a current of the logarithmic compressing part constant, when said variation portion is below the prescribed value. CONSTITUTION:A pulse light is projected to an object, a reflected light is photodetected by a photodetecting part 50 which has been placed so as to be separated by prescribed base line length from a projecting optical axis, and first and second signals from the photodetecting part 50 are inputted to amplifying parts 51A, 51B and logarithmic compressing parts 52A, 52B, respectively. In this case, bias supplying parts 55A, 55B supply a current to the logarithmic compressing part so that a bias current of the logarithmic compressing parts 52A, 52B is kept constant, and cut the supply current, when the amplified signal component exceeds a prescribed value. Also, stationary light storage parts 53A, 53B are brought to feedback by the supply current, absorb a stational light component in the photocurrent of the photodetecting part 50, and store the stationary light component before the light projection simultaneously with the light projection. In such a way, the variance caused by the noise when the object exists in a distant place is small, and a result of distance measurement being free from the influence by a reflection factor of the object can be obtained. |
