New NIST method improves accuracy of spectrometers
June 20, 2005, Gaithersburg, MD--Measurements of the intensity of light at different wavelengths can be made more accurately now, thanks to a new, simple method for correcting common instrument errors developed by researchers at the National Institute of Standards and Technology (NIST). NIST recently began offering a special calibration service to characterize spectrometers for stray light using the new method.
The NIST method improves the measurement accuracy of spectrometers by correcting errors arising from the presence of stray light, unwanted scattered radiation within an instrument. Stray light is often the major source of measurement uncertainty for commonly used spectrometers. It can cause unexpectedly large systematic errors, even as much as 100% depending upon the application. The new method nearly eliminates stray light errors to a level less than 0.001%. This allows very accurate measurement of low-power components of radiation and accurate measurements across a large dynamic range of intensities.
NIST researchers implemented and validated the method using a commercial CCD-array spectrograph, which measures light in the visible region instantly. They characterized the response to monochromatic emissions from tunable lasers that covered the instrument's full spectral range. Calculations were made using the measured data to produce a matrix that quantified the magnitude of the stray-light signal for every element (or pixel) of the detector array for every wavelength of light. The matrix then was used to correct the instrument's output signals for stray light. The method is simple and fast enough to be incorporated into an instrument's software to perform real-time stray-light corrections without much reduction in the instrument's speed.
Plans are being made to transfer the technique to industry, and a technical paper is in preparation. For further information about the calibration service, contact Yuqin Zong at [email protected], or (301) 975-2332.