| 摘要 |
PURPOSE:To contrive improvement of detecting accuracy, by installing a drive circuit which controls, basing on No.1, No.2 signals obtained by an one- dimension type semiconductor position detecting element, light receiving quantity in such a way that the light receiving quantity of the position detecting element becomes constant and obtaining the difference of both signals. CONSTITUTION:A light emitting element 1 emitting light to a specimen 2, an one-dimension type semiconductor position detecting element 3 which is installed to receive the reflected light from the specimen 2 in a light receiving point corresponding to the distance to the specimen and issues No.1, No.2 current signals I1, I2 corresponding to the light receiving position and a drive circuit 10 which amplifies these signals I1, I2 to feed out the No.1, No.2 signals I1', I2' by amplifying means 4, 5 respectively and controls light emitting quantity of the light emitting element in the manner that the light receiving quantity of a position detecting element 3 basing on the both signals and a subtracting means 11 which calculates K=I1'-I2' basing on the both signals I1', I2' and issuing the calculation result K as a detection distance signals and a level judg ing means 12 which issues an action confirmation signal when the output level of the drive circuit 10 remains within the specified value are installed.
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