| 摘要 |
PROBLEM TO BE SOLVED: To properly control the attitude of a grating by causing the angles of the reflecting surfaces of the grating to change only in the vertical plane. SOLUTION: The rotary shaft of the echelle grating is made to coincide with or to be parallel to a straight line which is formed orthogonal to a plurality of diffractive grooves and in parallel with reflecting surfaces respectively formed in the grooves. When the rotary shaft is set in this way, the angles of the reflecting surfaces will not change in the horizontal plane, but will change only in the vertical plane. COPYRIGHT: (C)2006,JPO&NCIPI
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