Spectrometer and method for correcting wavelength displacement of spectrometer

A method for correcting a displacement of a dispersed light image with use of a spectrometer, comprising the steps of:

• outputting a monochromatic ray from a light source;
• allowing the monochromatic ray from the light source to pass through at least one incident slit;
• imaging a dispersed light image of the monochromatic ray through the incident slit on an imaging plane;
• allowing a sensor array including a number of photoelectric conversion elements to receive the dispersed light image according to wavelengths, the photoelectric conversion elements being arrayed on the imaging plane of the sensor array to output an electric signal in correspondence to an intensity of the received light with respect to each wavelength component;
• calculating a variation in an imaging position of a primary dispersed light image of the monochromatic ray through the incident slit on the sensor array from an initial position thereof as a first image displacement amount when the monochromatic ray from the light source is passed through the incident slit;
• calculating a variation in an imaging position of a secondary dispersed light image of the monochromatic ray through the incident slit on the sensor array from an initial position thereof as a second image displacement amount when the monochromatic ray from the light source is passed through the incident slit;
• and
• calculating a third image displacement amount which is free of an influence due to a wavelength fluctuation of the monochromatic ray based on the first image displacement amount and the second image displacement amount.