A method is described of providing a document to a client coupled to a server. The numerical aperture of the spectrometer’s collimating mirror is intentionally mismatched to the numerical aperture of the spectrometer’s light-input device in order to exploit, by means of the exceedingly narrow width of the spectrometer’s entrance slit, the high degree of coherence of the central region of the Airy disk formed by the light-input device. A rear end portion of the hood is fitted to a front end portion of the cover and a rear end of the hood is located in front of a front end of the cabin frame, in a state where the hood is in a closed position.