In a signal processing circuit, a height arithmetic circuit obtains a measured value of a height of an object by using the principle of triangulation from a second light receiving signal which is transmitted from a second photodetector of position detecting type thereto. An error arithmetic circuit acquires...http://www.google.de/patents/US5392110?utm_source=gb-gplus-sharePatent US5392110 - Method and device for measuring height of object whose surface has irregular reflectance
