Patent ID: 6711352
Filing Date: 2004-03-23
Classification: G02B

Abstract:
An optical range finder having a projection unit including a light emitting element for projecting optical flux to an object, a light quantity adjusting unit for provisionally adjusting a light quantity of the projected optical flux, a photoreceiving unit for receiving the optical flux returned from the object and outputting a detection signal in accordance with a light quantity of the received optical flux, and circuitry unit for conducting a measurement of a distance to the object based on the detection signal, wherein the circuitry unit comprises:a light quantity determination circuit for comparing a signal level of the detection signal with a reference level to carry out binary determination of the light quantity of the returned optical flux; a reference level setting circuit for switchably supplying a plurality of reference levels to the light quantity determination circuit, the reference levels being preset in correspondence to multiple stages of the distance; and a control circuit for controlling the reference level setting circuit to supply the reference levels while switching the reference levels so as to enable the light quantity determination circuit to execute a plurality of the binary determination with the supplied reference levels for one measurement, thereby specifying the distance to one of the multiple stages based on the thus obtained plurality of the binary determination, and wherein the light quantity adjustment unit comprises: a group of parallel resistive elements which are selectively connected in parallel to the light emitting element for forming bypasses of electric currents flowing through the light emitting element to thereby execute a primary adjustment of the light quantity; and another group of serial resistive elements which are selectively connected in series to the light emitting element for regulating the electric current flowing through the light emitting element to thereby execute a secondary adjustment of the light quantity.