| 摘要 |
PURPOSE:To contrive improvement in detecting accuracy, by controlling light quantity of a light emitting element by a drive circuit in such a way that light receiving quantity of a position detecting element becomes constant, basing upon No.1 and No.2 signals obtained by the one-dimension type semiconductor position detecting element and providing a subtracting means feeding out the difference of No.1 and No.2 signals as a detecting distance signal. CONSTITUTION:A light emitting element 1 irradiating a beam of light to a specimen 2 and an one-dimension type semiconductor detecting element 3 which receives the beam in a light receiving point corresponding to the distance to the specimen 2 of above mentioned reflected beam by the specimen 2 and feeds out No.1 current signal I1, and No.2 current signal I2 corresponding to the position of the light receiving point are installed. Further, amplifying means 4, 5 feeding out as No.1, No.2 signals I1', I2' respectively amplified No.1, No.2 current signals, drive circuit 10 controlling light emitting quantity of the light emitting element 1 in such a way that the quantity of a position detecting element 3 becomes constant basing on both signals I1', I2' and a subtracting means 11 which culculates K=I1'-I2' basing on No.1, No.2 signals I1', I2' and feeds out the result of the calculation K as a detecting distance signal.
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