Patent ID: 7561266

Claim:
A spectroscopy instrument comprising: a diffraction grating monochromator for selecting a desired wavelength; a drive mechanism for rotating the diffraction grating of the monochromator, the drive mechanism comprising a pinion spur gear and a main spur gear; and programmable computing apparatus for operating the instrument, which is programmed to operate the drive mechanism to rotate the diffraction grating of the monochromator to an actual angle W a to select a desired wavelength λ in accordance with a calibration equation: W a =W n +a *sin( W n *N )+ b *cos( W n *N )+ c *sin( W n )+ d *cos( W n ) where W n equals the nominal diffraction grating angle corresponding to the desired wavelength λ, N equals the gear ratio between the pinion gear and the main spur gear, and a, b, c and d are correction coefficients.