Colorimetry of LEDs with array spectroradiometers

Nevas, Saulius; Lindemann, Matthias; Sperling, Armin; Teuber, Annette; Maaß, R.

doi:10.1007/s12647-009-0019-5

Cited by 16 publications

(21 citation statements)

References 2 publications

(2 reference statements)

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“…The response of the spectroradiometer to a monochromatic excitation by the laser radiation at any wavelength within the working spectral range of the instrument characterizes the stray light properties of the instrument and is normally unique to the specific instruments or a group of instruments. At PTB, Pulsed Laser for Advanced Characterisation of Spectroradiometers (PLACOS) setup is routinely used for this purpose [2,3]. Figure 1 shows an example of stray light characteristics of two array spectroradiometers of different type determined at PLACOS setup.…”

Section: Stray Light Characterization and Correction Using Tuneable Lmentioning

confidence: 99%

“…the spectral response of the instrument to a monochromatic excitation, are known for any wavelength within the spectral range of the array spectroradiometer, a numerical improvement of the stray light suppression by one to two orders of magnitude is possible. The determination of the correction matrix, however, requires comprehensive characterizations by using wavelengthtunable lasers as discussed, e.g., in [1,2]. Yet, the efforts and costs for the stray light characterization could be minimized provided that the stray light correction matrix determined for an instrument is stable and also transferable to other instruments of the same type, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Transferability of stray light corrections among array spectroradiometers

Nevas

Sperling²,

Oderkerk³

2013

AIP Conference Proceedings

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Abstract. One of the most important properties of array spectroradiometers limiting their applications, especially in the UV spectral range, is a high level of spectral stray light. The suppression of the stray light can be improved numerically by using a correction matrix derived by comprehensive characterizations using wavelength-tunable lasers. For economic reasons, it is highly desirable that the same stray light correction matrix were effective on a number of array spectroradiometers of the same type and model. Here we address the properties of the instruments defining the transferability of the stray light corrections from one instrument to another and show examples based on the stray light characterization, hardware optimization and test measurements with a number of array spectroradiometers.

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Section: Stray Light Characterization and Correction Using Tuneable Lmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Transferability of stray light corrections among array spectroradiometers

Nevas

Sperling²,

Oderkerk³

2013

AIP Conference Proceedings

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“…For the characterization of the bandpass functions of the Brewer instrument, an upgraded PLACOS setup (Nevas et al, 2009) featuring a tunable pulsed laser system based on an optical parametric oscillator (OPO) was used at Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig (Fig. 3).…”

Section: Instrumental Setupmentioning

confidence: 99%

Wavelength calibration of Brewer spectrophotometer using a tunable pulsed laser and implications to the Brewer ozone retrieval

et al. 2018

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Abstract. In this contribution we present the wavelength calibration of the travelling reference Brewer spectrometer of the Regional Brewer Calibration Center for Europe (RBCC-E) at PTB in Braunschweig, Germany. The wavelength calibration is needed for the calculation of the ozone absorption coefficients used by the Brewer ozone algorithm. In order to validate the standard procedure for determining Brewer's wavelength scale, a calibration has been performed by using a tunable laser source at PTB in the framework of the EMRP project ENV59 ATMOZ "Traceability for the total column ozone". Here we compare these results to those of the standard procedure for the wavelength calibration of the Brewer instrument. Such a comparison allows validating the standard methodology used for measuring the ozone absorption coefficient with respect to several assumptions. The results of the laser-based calibrations reproduces those obtained by the standard operational methodology and shows that there is an underestimation of 0.8 % of the ozone absorption coefficients due to the use of the parametrized slit functions. BackgroundNowadays the primary ground-based instruments used to report total ozone column (TOC) are Dobson and Brewer spectrophotometers. Based on the irradiances measured by these instruments in the ultraviolet (UV) spectral range and on well-defined retrieval procedures, TOC values are derived. The Brewer spectrometer (Brewer, 1973;Kerr et al., 1981;Kerr, 2010) was introduced in the 1980s as an automatic device measuring direct solar UV radiation and global UV irradiance. Both the Brewer and the Dobson instruments were considered by the World Meteorological Organization (WMO) in the framework of the Global Atmosphere Watch program (GAW) as the standard instruments for TOC monitoring. The wavelength calibration is needed for calculation of the ozone absorption coefficient used by the Brewer ozone retrieval algorithm. The Brewer spectrophotometer has two operating modes. In the ozone mode, used for the total ozone column and aerosol measurements, the diffraction grating stays at a fixed position while the six operational wavelengths are selected by a rotating slit mask (Table 1). The scanning mode is used to perform spectral irradiance measurements in the UV spectral range. In this mode, the slits are fixed and the spectral scan is carried out by turning the diffraction grating. The usual wavelength calibration procedure is performed in the scanning mode by analyzing recorded emission lines of the spectral discharge lamps, which are usually mercury (Hg), cadmium (Cd), and zinc (Zn). The use of the spectral lines provided in Table 2 allow us to determine the central wavelengths and the corresponding full-widthat-half-maximum (FWHM) of the slit functions as well as the relation between the positions of the grating and the corresponding instrument wavelengths (dispersion relation) required to determine the operational wavelengths used for the ozone determination. To obtain the ozone absorption coefficients, the instrument...

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“…Array-spectroradiometers are sensitive to stray light and also to spectral distortions. 35 Both effects may depend on wavelength, which means that the band pass function and the nonzero response in out-of-band regions (stray light) may vary with wavelength. Stray light and bandpass effects arise concurrently and should be corrected simultaneously, if possible, which can be achieved by a deconvolution.…”

Section: Stray Light and Band Pass Correctionmentioning

confidence: 99%

“…Array‐spectroradiometers are sensitive to stray light and also to spectral distortions . Both effects may depend on wavelength, which means that the band pass function and the nonzero response in out‐of‐band regions (stray light) may vary with wavelength.…”

Section: Evaluating Spectral Measurementsmentioning

confidence: 99%

Uncertainty evaluation and propagation for spectral measurements

Schmähling

Wübbeler

Ruggaber

et al. 2017

Color Research & Application

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The measurement of the spectral power distribution (SPD) of a radiation source by array spectroradiometers is a technique that is widely used. In many applications, quantities that are derived from the SPD by a weighted integral over a wavelength interval are of interest. These integral quantities ought to be accompanied by a reliable uncertainty statement, for example, to assess conformity with prescribed limits or in order to judge the consistency of results obtained at different laboratories. We have developed a generally applicable Monte Carlo procedure for evaluating the uncertainty of spectral measurements. The procedure naturally accounts for correlations in the SPD which turn out to be crucial. Means are provided to handle and transfer these large-scale correlation matrices easily. The proposed approach is illustrated by the determination of the SPD of colored LEDs from array spectroradiometer measurements, together with the derived CIE 1931 color coordinates. MATLAB TM software implementing the proposed analysis procedure is made available. K E Y W O R D Scolor coordinates, photometry, radiometry, spectral measurements, uncertainty 6 |

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Colorimetry of LEDs with array spectroradiometers

Cited by 16 publications

References 2 publications

Transferability of stray light corrections among array spectroradiometers

Transferability of stray light corrections among array spectroradiometers

Wavelength calibration of Brewer spectrophotometer using a tunable pulsed laser and implications to the Brewer ozone retrieval

Uncertainty evaluation and propagation for spectral measurements

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