Patent ID: 7126684

Claim:
A spectroscope comprising: an entrance aperture member for passing light; a first optical system for collimating diverging light having passed through the entrance aperture member; a rotative spectroscopic element for separating the collimated light into a plurality of light fluxes; a second optical system having a plurality of lenses for condensing the light fluxes near a focal plane, at least one of the lenses having a positive focal length and at least one of the lens having a negative focal length; a variable-width slit disposed near the focal plane; and an optical detector for detecting the light fluxes having passed through the variable-width slit, the light fluxes having different wavelengths corresponding to variation of the slit-width of the variable-width slit and/or the rotation angle of the rotative spectroscopic element, wherein: aberrations with respect to the wavelengths of off-axial light fluxes are compensated in the second optical system; and a relationship of ν + −ν − >25 is effective under the condition that: ν 30 indicates an Abbe number for the lens having the positive focal length; and ν − indicates an Abbe number for the lens having the negative focal length.