| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical system, restraining variation due to a change in environmental temperature even in the case of a configuration having a light source having such a characteristic that wavelength changes with a temperature change and a diffraction element. SOLUTION: This optical system includes: a light source 1 having such a characteristic that the wavelength changes with a temperature changes; and the diffraction element for changing the traveling direction of a light beam from the light source 1, wherein when the working temperature range of the optical system is 2T[°C], the diffraction order of a light beam is m, the designed outgoing light beam angle of the diffraction element 3 isθm [rad], the allowable change value of outgoing angle of the diffraction element 3 is±Δθm [rad], the designed wavelength of the light source 1 isλ[nm], the wavelength change amount per 1°C isΔλ[nm], the structure period of the diffraction element 3 is P [nm], and the coefficient of linear expansion of the diffraction element 3 isα[/°C], the following expression (1) is satisfied. The expression (1) is -(1+αT)≤mT(Δλ-αλ)/[PΔθmcosθm]≤1+αT. COPYRIGHT: (C)2009,JPO&INPIT |
