Monochromator

A monochromator, comprising:

• a housing with an entrance and an exit;
• a diffraction grating placed within the housing so as to receive incident light from the entrance and disperse the incident light into a spectrum of light from which a component of light having a set wavelength is to be extracted through the exit;
• an optical filter configured to be removably inserted into an optical path extending from the diffraction grating to the exit, and remove light within a specific wavelength band which is out of the set wavelength;
• a rotary drive mechanism configured to rotate the diffraction grating, using a stepping motor as a drive source;
• a wavelength-movement information setter configured to set wavelength-movement information which is a kind of information to be used for rotating the diffraction grating from a predetermined original position to a rotational position corresponding to the set wavelength;
• and
• a wavelength-movement controller configured to control the rotary drive mechanism so as to perform a wavelength-movement operation which includes rotating the diffraction grating to the original position and subsequently rotating the diffraction grating to the aforementioned rotational position based on the wavelength-movement information.