High sensitive multi-wavelength spectral analyzer

A high sensitive multi-wavelength spectral analyzer for spectral detection of Raman scattered light or fluorescence caused by excitation light, comprising:

• a spectroscope including an optical system that limits coincident light, a collimator lens disposed such that a focal point of said collimator lens is coincident with an end of said optical system, to convert light emerging from said end into parallel rays, a reflection diffraction grating that diffracts the parallel rays from said collimator lens to produce spectra, and an imaging lens that focuses the parallel rays diffracted by said reflection diffraction grating on an image plane thereof to form a spectral image;
• and
• a high sensitivity photodetector selected from the group consisting of a one-dimensional photodetector and a two-dimensional photodetector, the high sensitivity photodetector disposed on the image plane of said imaging lens such that an observation wavelength region is within a detecting surface thereof, wherein said imaging lens and said high sensitivity photodetector are disposed such that the optical axis of said imaging lens is coincident with a bisecting angle of a short wavelength-side diffraction angle and a long wavelength-side diffraction angle of the observation wavelength region and said optical axis is substantially coincident with a center of the detecting surface of said photodetector;
• and
• said reflection diffraction grating is a blazed diffraction grating, and said collimator lens has a larger diameter than that of said collimator lens,
• means for taking out as a spectral image -first-order diffracted light for minimizing stray light to a larger extent than to which the loss of incident light is minimized, said taking out means comprising said collimator lens, said blazed diffraction grating and said imaging lens.