Patent ID: 8440956
Filing Date: 2013-05-14
Classification: G01V,H03K

Abstract:
1. A light receiving detection circuit comprising: a light receiving element configured to receive light emitted from a corresponding projection element; a current/voltage conversion circuit that converts a current signal passing through the light receiving element into a voltage signal; and a filter portion that has a plurality of stages, wherein the filter portion comprises a high-pass filter and an amplifying circuit, and wherein the high-pass filter is able to be switched such that a time constant of the high-pass filter increases when the light receiving element receives light emitted by the corresponding projection element and such that the time constant decreases when other projection elements, except for the corresponding projection element, emit the light, wherein, in the high-pass filter, a plurality of resistors connected in parallel are connected in series to a capacitor, and an analog switch is connected in series to at least one of the resistors, the analog switch is turned off such that the time constant of the high-pass filter increases, and the analog switch is turned on such that the time constant of the high-pass filter decreases.