WAVELENGTH SELECTION SWITCH, SPECTROSCOPE, SPECTROMETER AND WAVELENGTH SELECTION SWITCH USING SAME

摘要

Provided are a spectrometer, etc. which show sufficiently small change in dispersion characteristics even when temperature variation is produced. The spectrometer comprises, in sequence in the forward direction of incidence of a light ray, a first group of dispersion elements and a second group of dispersion elements. Δθ₄ and Δθ₅ are substantially equal when the exit angle of a light ray in the forward direction from the first group of dispersion elements at a first temperature (T₁) is θ_4, the exit angle_{of a light ray in the forward direction from the first group of dispersion elements at a second temperature (T2) different from the first temperature (T1) is θ'4, the difference between the exit angles (θ'4－θ4) is Δθ4, the light ray in the forward direction at the first temperature (T1) being a light ray following an optical path that exits from the second group of dispersion elements, the exit angle of a light ray in the reverse direction from the second group of dispersion elements at the second temperature (T2) is θ"5, the angle of incidence of a light ray in the forward direction to the second group of dispersion elements at the first temperature (T1) is θ5, and the difference (θ"5－θ5) between the exit angle and the incidence angle is Δθ5.}