| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a position detector having an improved detection accuracy obtained by suppressing the occurrence of the second-order or higher diffraction light and stray light, and improving the S/N ratio of a position detection signal. <P>SOLUTION: When a pitch of a diffraction grating 11 in which a lattice plane 11a is covered with a protection layer 12 having a refractive index n is d, a wavelength of coherent light radiated in vacuum is λ<SB POS="POST">0</SB>, d<2λ<SB POS="POST">0</SB>/n. An incidence angle θ<SB POS="POST">0</SB>of the coherent light into the diffraction grating 11 is then set to an angle that satisfies the expression ¾sinθ<SB POS="POST">0</SB>¾<(2λ<SB POS="POST">0</SB>/dn)-1, and the first-order diffraction light is used for position detection. <P>COPYRIGHT: (C)2012,JPO&INPIT |
