Abstract: The advantage of sustained wavelength accuracy and mechanical simplicity of a spectrophotometer using a photodiode array as photometric detector and a fixed diffraction grating as dispersion means may be limited to a relatively short wavelength range by problems of stray light, second order errors and overloading of the detector at portions of the wavelength range. By utilizing repeat scanning of the array, each scan being modified by using a different source lamp and correction filters, freedom from the cited problems over part of each scanned wavelength range can be effected. A computer controls the scan sequence and combines the usable portion of each scan to produce error free operation over an extended range.

Abstract: This invention is directed to a digital wavelength calibration system for a spectrophotometer, which includes a photodiode array that forms an output detector for the spectrophotometer, a light source for generating at least one reference emission line of known peak wavelength, a computer controlled mechanism for causing the peak of said reference line to fall in close proximity to the center of a preselected pixel of said photodiode array, peak location computing apparatus for computing the exact position data of the peak relative to the pixel center in terms of the pixel spacing and the ordinal number of the preselected pixel and for retaining this position data for subsequent wavelength computation, wavelength identification computing apparatus for computing the numerical relationship data of the ordinate number of each pixel to the wavelength falling on that pixel and for retaining this relationship data for subsequent correlation with data generated by the pixel, and apparatus for computational processin