| 摘要 |
PURPOSE:To increase an allowance degree from a structural planning aspect and to specify an arbitrary absolute origin, by providing separate optical lattices different in a pitch and making it possible to generate a reference pulse signal on the basis of the phase difference between sets from the relation of both optical lattices. CONSTITUTION:A main scale 10 having a measuring optical lattice 13 and an origin detecting optical lattice 15 different from said lattice 13 in a pitch provided thereto and an index scale 20 provided with measuring and origin detecting reference optical lattices 23(23A, 23B), 25(25A, 25B) opposed to each other are moved relatively. Whereupon, by the irradiation of the non-parallel beam from a non-parallel illumination system 40, electric signals having phase differences theta1, theta2 are respectively outputted to the optical lattices 23, 25 from the corresponding photoelectric converter 30. A reference signal generating circuit 70 inputs the electric signals having the phase differences theta1, theta2 and generates a reference signal when the phase difference (theta1-theta2) between sets becomes a specific value. Therefore, by utilizing this signal, the absolute origins of both scales 10, 20 can be arbitrarily specified. The relative moving displacement quantity of both scales 10, 20 is detected by the processing of the signal from the converter 30.
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