PURPOSE: To enlarge the dynamic range, while enhancing the sensitivity by filtering a part of a light beam dispersed spatially through a diffraction grating and then recombining the dispersed light beam through a diffraction grating.
CONSTITUTION: An input optical fiber 10 introduces an input light beam 12 through a lens 14 to a diffraction grating 16 which diffracts the light beam 12, to produce a spatially dispersed light beam 20. Since the rotating diffraction grating 16 diffracts different wavelengths at different angles, component wavelength of the light beam 12 can be obtained. A slit 24 passes a part of the light beam 20 and serves as a spatial filter to generate a filtered light beam 30. The light beam 30 is recombined through the diffraction grating 16, to generate an output light beam 36. The light beam 36 is reflected at a mirror 30 toward the input end of an output optical fiber 42, which further filters the light beam 36 as an output aperture. The light beam 36 is directed to a photodetector and converted into an electric signal which is then amplified through an amplifier 48.
JIEIMUZU ROI SUCHINPURU
JIYON DAGURASU NAITO
JIYOZEFU ENU UESUTO
BARII JII BURUUMU
