Photodiode configurations for simultaneous background correction and specific wavelength detection
AssigneeVarian Associates, Inc.
InventorsGregory J. Wells, Barbara A. Bolton
Life of this patent
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Abstract
In a spectrophotometer having photodetectors positioned at fixed wavelengths, the photodetector is divided into three subdetectors, a main subdetector on the wavelength of interest and two background subdetectors located on each side of the main subdetector, the background subdetectors together having area equal to that of the main subdetector, the background subdetectors being connected in polarity reverse that of the main subdetector to correct for changes in background radiation.
Claims4
In a gas chromatography apparatus having an optical spectrometer with photodetectors at fixed wavelengths, a photodetector comprising:
- a first means for detecting radiation at the fixed wavelength and for providing a first electrical signal as a function of radiation intensity;
- a second means for detecting radiation at a wavelength slightly greater than the fixed wavelength and for providing a second electrical signal as a function of radiation intensity;
- a third means for detecting radiation at a wavelength slightly less than the fixed wavelength and for providing a third electrical signal as a function of radiation intensity;
- said second and third means being connected in the same polarity so that said second and third electrical signals add to provide a summed electrical signal and said first means being connected in reverse polarity to said second means so that said summed electrical signal is subtracted from said first electrical signal, the efficiency of said first, second and third means being such that said first means provides twice as much electrical signal as said second means or said third means for the same amount of radiation.
Dependencies are inferred from the claim text.