Browse Prior Art Database

Spectrophotometric Noise Cancellation

IP.com Disclosure Number: IPCOM000086924D
Original Publication Date: 1976-Nov-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Pillus, CA: AUTHOR [+2]

Abstract

A xenon light source is commonly used in spectrophotometry. This source has a favorable energy content throughout the spectrum, but is disadvantageous in that it also has a high noise content. The drawing shows a system for eliminating the noise content and providing a spectrophotometer capable of accurately measuring samples presenting low signal levels where noise would otherwise be a problem.

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Spectrophotometric Noise Cancellation

A xenon light source is commonly used in spectrophotometry. This source has a favorable energy content throughout the spectrum, but is disadvantageous in that it also has a high noise content. The drawing shows a system for eliminating the noise content and providing a spectrophotometer capable of accurately measuring samples presenting low signal levels where noise would otherwise be a problem.

As shown in the figure, a wide band light source 1 having a high noise content, such as would be presented by a xenon light source, radiates light through a condensing lens 2 onto the input end of a fiber-optic bundle 3. The bundle is split to provide a reference path 4 and a sample path 5. Light from the sample path 5 illuminates a test sample 6 and light reflected from the test sample is picked up by a fiber-optic bundle 7 that forms part of the sample path. Light from both paths is directed onto a filter wheel assembly 8 and light passing through the assembly activates detectors 9 and 10, which may be photomultiplier (PMT) tubes. For the noise cancellation technique to work, it is necessary, first, that both the signal and reference beams be of equal path lengths (i.e., the optical path difference is zero). Second, the filter wheel must be designed to illuminate both the sample and reference beams simultaneously, preferably with the same wavelength. It is contemplated that this be done by providing a circular variable filter wherei...