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Abstract

An optical type displacement detecting device including a main scale and an index scale, wherein a pitch of a first optical grating formed on the main scale is set at P and a pitch of a second optical grating formed on the index scale is set at P/n, thereby producing divided detection signal having pitch P/n. Furthermore, the pitch of the second optical grating is set at (u+v) P/u or (u+v) P/(2u) (u is a gap between a diffusive light source and the first optical grating and v is a gap between the first and second optical gratings), so that a collimator lens can be dispensed with. Further, higher harmonic components of the first optical grating are utilized, whereby the pitch of the second optical grating is set at substantially (u+v) Q/u or (u+v) Q/(2u) (Q=P/m, and m is a whole number of 2 or more), thereby preventing the pitch of the second optical grating from being divided into small ones.

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First Claim