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A SIMPLE STRAY-LIGHT CORRECTION METHOD FOR ARRAY SPECTROMETERS

IP.com Disclosure Number: IPCOM000128610D
Original Publication Date: 2005-Sep-16
Included in the Prior Art Database: 2005-Sep-16
Document File: 32 page(s) / 1M

Publishing Venue

National Institute of Standards and Technology

Related People

YUQIN ZONG: INVENTOR [+4]

Abstract

In many applications, the measurement accuracy of spectrometers, particularly single grating instruments such as spectrographs, is limited by the presence of stray radiation within the instrument. A simple, practical method has been developed to correct a spectrometer's output signals for stray-light errors. By characterizing the instrument's response to a set of monochromatic lasers that cover the instrument's spectral range, a stray-light signal distribution matrix is obtained that quantifies the magnitude of stray-light signal within the instrument. Stray light in measured spectral signals is corrected by a stray-light correction matrix with a simple matrix multiplication.

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A Simple Stray-light Correction Method for Array Spectrometers

  Yuqin Zong, Steven W. Brown, Keith R. Lykke, and Yoshi Ohno National Institute of Standards and Technology, Gaithersburg, l\ 20899

Abstract

   In many applications, the measurement accuracy of spectrometers, paricularly single grating instruments such as spectrographs, is limited by the presence of stray radiation within the instrument. A simple, practical method has been developed to correct a spectrometer's output signals for stray-light errors. By characterizing the instrument's response to a set of monochromatic lasers that cover the instrument's spectral range, a stray-light signal distribution matrix is obtained that quantifies the magnitude of stray-light signal within the instrument. Stray light in measured spectral signals is corrected by a stray-light correction matrix with a simple matrix multiplication. The method has been implemented and validated using a commercial CCD-aray spectrograph. The measurement results demonstrated that the stray-light errors after the correction using this method were reduced by one to two orders of magnitude, to a level

equivalent to less than one count of the I5-bit resolution instrument, to a level below 10-5.

Further reduction of the corrected stray light to a level of 10-6 is possible with a spectrograph that has lower stray light. This method can be easily implemented into an instrument's software to perform real-time corrections. Using instruments that have been corrected for stray light, significant reductions of overall measurement uncertainties are expected in many applications including colorimetry, radiometry, photometry, biotechnology, and other areas where spectrographs are commonly used.

Draft. Please do not distribute.

FOR OFFICIAL USE ONLY
I)ROPRIETARY INFORMA TION

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Keywords: aray detector; CCD aray; calibration; colorimetry; correction; laser; LED; photodiode aray; photometry; radiometry; spectrograph; stray light; spectrometer; spectroradiometer; spectrophotometer.

FOR OFFICIAL USE ONLY PROPRIETARY INFORMATION 2

Y. Zong, et aL.

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1. Introduction Spectrometers are used in wide applications including spectroradiometry, spectrophotometry, colorimetry, photometry, and optical spectroscopy. Many of the

instruments used in industry are multi-channel spectrometers, commonly called spectrographs or aray spectrometers, employing array detectors that can simultaneously

acquire an entire spectral image over a finite spectral region. Spectrographs commonly consist of an entrance slit, a dispersing element (such as a grating), an array detector, and optics to image the entrance slit onto the aray detector (Fig. I). Because of the dispersing element, the spatial image of the entrance slit falls on different regions of the detector aray, depending on its wavelengt...