| 摘要 |
A photoelectric displacement detector measures a distance from a number of repetitions of dark and light portions which are formed by the repetition of overlapping of slits in slit trains formed in a main scale and an index scale when they are moved relative to each other. The photoelectric displacement detector comprises reference marks disposed on the main scale at appropriate spacing, mark-detecting means provided on the index scale, identification marks positioned in the spaces between adjacent reference marks so as to identify the spaces, identification mark reading means actuated by the mark-detecting means, identification mark verification means which compares an identification mark read by the identification mark reading means with an identification mark previously set by a mark selection setting device to verify whether or not the two identification marks coincide, and origin setting means which sets as an origin for the measurement of a distance the detected reference mark position, under the conditions that there is a coincidence signal from the identification mark verification means and a mark detection signal output from the mark-detecting means immediately after the input of the coincidence signal. |
