Wavelength-scanning mechanism and method for spectrometer

Abstract

A wavelength-scanning mechanism for a spectrometer utilizes an eccentric disc cam driven by a pulse motor to pivot a diffraction grating with a contact bar fixed thereto. A light source supplies light to the mechanism with a first concave spherical mirror reflecting light to the diffraction grating and reflecting light reflected by the diffraction grating to a zero-order light detector. A second concave spherical mirror reflects light diffracted by the diffraction grating to a diffracted light detector. A controller receives information from the light detectors and controls the pulse motor. At least one cam follower is mounted on the cam at a position eccentric from the rotational axis thereof and slidably contacts the contact bar. Alternatively, the diffraction grating has two contact bars fixed thereto, and the cam follower is pivoted between the contact bars. A method of utilizing the mechanism first determines a center value of zero-order light reflected by the diffraction grating by pivoting the diffraction grating in steps between the time zero-order light is detected until it is no longer detected. The number of steps is divided by two, which yields the center value. Diffracted light is detected at the center value, and the spectral intensity of the detected diffracted light is calculated.