| 摘要 |
PURPOSE:To suppress unnecessary reflected light and scattered light and to prevent deterioration in S/N ratio by making reflecting surfaces other than a mirror rocking part low in reflection factor than the mirror rocking part. CONSTITUTION:The mirror rocking part 13 is a reflecting part which contributes to signal light and has a 87-95% reflection factor. The reflection factor of this part is preferably high so as to increase the intensity of the signal light, but a mirror surface part 15 is preferably low in reflection factor because it is the place where unnecessary reflected light, scattered light, and diffracted light are generated. For the purpose, the mirror surface part 15 and part of an end part (a) are coated with a light absorptive material or low reflective material to decrease their surface reflection factor. Consequently, unnecessary light and scattered light are reduced and the S/N ratio of the signal is increased.
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