A light flux passing through an incident slit 1 is dispersed into light having a short wavelength to light having a long wavelength by a concave diffractiongrating 2, and an optical filter 4 formed by bonding a plurality of optical filters having different properties and having bonding surfaces in the oblique direction is arranged just before a photodiode array type detector 3 for detecting the light intensity of the dispersed light. 入射スリット1を通した光束を凹面回折格子2で短波長から長波長の光に分散し、この分散光の光強度を検出するホトダイオードアレイ型の検出器3の直前に、斜め方向の接合面を有する複数の異なった性質の光学フィルタを接合してなる光学フィルタ4を配置する。 - 特許庁