| 摘要 |
PURPOSE: To enlarge the measurable wavelength range while the desired wavelength resolution is maintained by dividing the measurable wavelength range into a plurality of wavelength ranges, and furnishing light incident holes for different wavelength areas. CONSTITUTION: The measurable wavelength range is divided into a plurality of wavelength areas, for example wavelengthsλ10±Δλ,λ20±Δλ, and light incident holes 6, 7 are furnished for different wavelength areas. That is, the light of the wavelength areaλ10±Δλis intruded from the incident hole 6, while the light of wave length areaλ20±Δλis intruded from the incident hole 7. The incident light is turned into parallel beams of light by a collimating mirror 2 and put into a diffraction grating 3. The light beam emitted from the diffraction grating 3 is condensed by a focusing mirror 4 and cast on an array element 5. The diffraction angle varies according to the wavelength of the incident light, and the position of the light spot running againt the array element 5 varies. Therefore, it is practicable to know the wavelength of the incident light from the position of the light spot. Therein the measurable wavelength range can be enlarged twice while the wavelength resolution is well maintained.
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