Determination of the diffuser reference plane for accurate illuminance responsivity calibrations

Hovila, Jari; Mustonen, M.; Kärhä, Petri; Ikonen, Erkki

doi:10.1364/ao.44.005894

Cited by 16 publications

(12 citation statements)

References 3 publications

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“…The UV9 is equipped with a dome‐shaped diffuser of 4.5 mm height. By adapting calculations performed for similar diffusers [ Bernhard and Seckmeyer , 1997; Hovila et al , 2005], we estimated that the reference plane for irradiance calibrations could be about 2 mm behind the diffuser's top. Recent experimental evidence conflicts with theoretical calculations, indicating that the offset for shaped diffusers may exceed the height of the diffuser [ Manninen et al , 2006; Gröbner and Blumthaler , 2007].…”

Section: Discussionmentioning

confidence: 99%

Comparison of ultraviolet spectroradiometers in Antarctica

et al. 2008

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[1] Solar ultraviolet irradiance has been monitored in Antarctica for almost two decades by a network of spectroradiometers established by the National Science Foundation. Data have been used for investigating increases in ultraviolet radiation in response to ozone depletion, validation of satellite observations, and the establishment of ultraviolet radiation climatologies and trends. To assess the quality of data collected, measurements of the monitoring spectroradiometer installed at Arrival Heights (78°S, 167°E) were compared with an independently calibrated, state-of-the art instrument, which was installed next to the monitoring system for a three-month campaign. Measurements of the two instruments differed by 5-7% on average. The discrepancy is quantitatively explained by the different irradiance scales used by the two systems, a bias in determining the reference plane of fore-optics, drifts of calibration standards, some temperature-dependence in the transmission of the entrance optics, and nonlinearity of one of the systems. The wavelength accuracy of data from both instruments was also tested with two commonly used correlation methods. Wavelength shifts determined with the two methods agreed to within 0.003-0.006 nm. Results of the campaign suggest that data collected by the monitoring instrument are of adequate quality for submission to the Network for the Detection of Atmospheric Composition Change.

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Section: Discussionmentioning

confidence: 99%

Comparison of ultraviolet spectroradiometers in Antarctica

et al. 2008

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“…The reference plane of the Schreder J1002-01 diffuser is located unexpectedly deep inside the measuring head even in the UVA region. The dome shape would only explain 2.0 mm of the offset when using equations in [6]. In the visible and the NIR regions the offset increases apparently due to the translucency of Teflon.…”

Section: Reference Plane Positionsmentioning

confidence: 95%

“…For diffusers with dome geometry, it is clear that the reference planes are located inside the diffuser. In a recent paper, we have studied the distance offset effect with various photometer heads [6]. For domeshaped photometer diffusers, the effective measurement planes were located 5.0 mm to 8.5 mm behind the outermost points of the diffusers.…”

Section: Introductionmentioning

confidence: 99%

Determination of distance offsets of diffusers for accurate radiometric measurements

Manninen¹,

Hovila²,

Seppälä³

et al. 2006

Metrologia

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A method for the determination of the effective measurement plane of spectroradiometer diffusers at various wavelength regions is described. The method is based on the inverse-square law of the distance dependence of the measured signal. The scheme is tested with three planar and one dome-shaped spectroradiometer diffuser at four wavelength bands. The distance offsets of the diffusers determined in the UVA region are from 0 mm to 2.1 mm for the planar diffusers and 6.4 mm for the dome diffuser, whereas the corresponding values in the NIR region are from 0 mm to 7.7 mm and 8.2 mm. The uncertainties of the measured reference plane positions of the diffusers are estimated to be 0.3 mm. If the reference plane position is not properly taken into account in calibration measurements with lamps, large systematic errors may appear when measuring radiation from distant sources. We also investigate the wavelength dependence of the angular responsivity of the diffusers. A clear correlation appears between the wavelength dependences of the distance offsets and the angular responsivity curves.

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“…Previous publications have shown that the traditional assumption of determining the reference plane of shaped diffusers by geometrical calculations systematically underestimates the actual reference plane obtained from careful laboratory measurements. 4,5 Indeed, Manninen et al 4 calculated the reference plane of the J1002 diffuser to be 2 mm inside of the dome when measured from the top of the dome by use of a simple geometrical model and showed that this result is in contrast with their laboratory measurements, which locate the reference plane 5.3 mm behind the top of the dome, a difference of more than 3 mm relative to the theoretical calculation.…”

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confidence: 93%

Experimental determination of the reference plane of shaped diffusers by solar ultraviolet measurements

Gröbner¹,

Blumthaler

2006

Opt. Lett.

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The optical reference plane of a J1002 shaped dome diffuser from CMS-Schreder was determined using direct normal spectral solar UV irradiance measurements relative to a flat Teflon diffuser. The spectroradiometers were calibrated relative to the same irradiance standard. The optical reference plane of the shaped J1002 diffuser is 5.3 mm behind the top of the dome with an uncertainty of 1.0 mm. Solar UV irradiance measurements based on a lamp calibration using the top of the dome as the reference will overestimate the global solar irradiance by 2.1% for the usual calibration distance of 500 mm.

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Determination of the diffuser reference plane for accurate illuminance responsivity calibrations

Cited by 16 publications

References 3 publications

Comparison of ultraviolet spectroradiometers in Antarctica

Comparison of ultraviolet spectroradiometers in Antarctica

Determination of distance offsets of diffusers for accurate radiometric measurements

Experimental determination of the reference plane of shaped diffusers by solar ultraviolet measurements

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