Abstract
Monochromators are a common utility for the spectral calibration of spectrometers. To guarantee traceability of characterization measurements to SI-standards, monochromators used as secondary standards must be properly calibrated. Common calibration procedures are based on the measurement of spectral lines emitted by gas-discharge lamps or lasers. Due to the nature of these light sources, the sampling of calibration points cannot be freely chosen. In this paper we present an approach where an echelle grating wavelength meter (WM) is used to traceably calibrate the emitted center wavelength of a monochromator at almost any sampling interval. In addition, it is possible to calibrate the monochromator outside the sensitive spectral range of the WM used. It is demonstrated how a WM is calibrated and then how it is used to calibrate the monochromator of DLR's Calibration Home Base (CHB) for imaging spectrometers at DLR Oberpfaffenhofen, Germany. The same approach is also used for the monochromator, which is intended for the laboratory calibration of the German hyperspectral satellite mission EnMAP.
Highlights
Monochromators are a widely used tool for the spectral calibration of spectrometers
Common monochromator calibration procedures involve replacing the light source with a gas-discharge lamp emitting known spectral lines as the standard [1, 2]
In this paper we presented a method to calibrate grating monochromators with almost arbitrary sampling interval, traceable to gas-discharge lamps by using an echelle grating wavelength meter
Summary
Monochromators are a widely used tool for the spectral calibration of spectrometers. Traceable monochromator calibration is essential for this application. By tuning a monochromator’s wavelength setting and simultaneously measuring the emitted power with a radiometer, the relation between grating angle and output wavelength is determined The disadvantage of this approach is that a statement about the actual output wavelength can only be made at the positions of the spectral emission lines. This problem can be solved by an additional calibration of the electromechanical drive of a monochromator [3]. We discuss a method to use higher diffraction orders of a monochromator to calibrate its wavelength setting outside the sensitive spectral range of the WM. The traceable calibration of the LambdaScan-usb WM and how we use it to calibrate the CHB monochromator is presented
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