Laser-based radiometry for large-area detectors, luminance standards and spectroradiometers

Project Description

For the calibration of large-area filter detectors in photometry, colorimetry, UV dosimetry and spectroradiometry and for the characterization of luminance standards and spectroradiometers, large-area, high-irradiance monochromatic radiation fields are required with narrow bandwidth tuneable over wide spectral ranges without gaps. Tuneable lasers are adequate sources if coherence effects (interferences and speckles) of the laser radiation are properly minimized and taken into account, respectively, depending on the type of the radiometric / photometric detector used. Activities in this field have been started in several NMIs.

In addition, it is intended to include a comparison of different detector calibration methods based on tuneable lasers and also based on the use of conventional incoherent quasi-monochromatic radiation.

Part of the project at the PTB is one of the Pilot Special Facilities (iMERA):
“TULIP (TUneable Lasers In Photometry)”
with a set of continuous wave and pulsed tuneable lasers and a special spectroradiometer used to produce wavelength-scanning high-irradiance monochromatic and uniform coherent and non-coherent radiation fields, where polarization and speckle effects are suppressedthat can be used for the calibration of large-area filter detectors in photometry, colorimetry, UV dosimetry and spectroradiometry against trap detectors and a broad-band cryogenic radiometer. The tuneable pulsed laser setup is also used for rapid stray-light characterisation/reduction of array spectrometers.
See also: http://www.ptb.de/en/org/4/TULIP.htm

Final Report 2012-02-14

Many of the intensions of this project are presently realised within the framework of the EMRP project ENV03. Therefore, it seems to be wise to finalise project 896 now and to potentially start up a new project after completion of ENV03.

Progress Report 2010-02-23

For the calibration of large-area detectors in photometry, colorimetry, UV dosimetry and spectroradiometry and for the characterization of luminance standards and spectroradiometers, large-area, high-irradiance monochromatic radiation fields are required with narrow bandwidth tuneable over wide spectral ranges without gaps. Tuneable lasers are adequate sources if coherence effects (interferences and speckles) of the laser radiation are properly minimized and taken into account, respectively, depending on the type of the radiometric or photometric detector used. Activities in this field have been started in several NMIs (e.g. NIST, NPL, PTB, METAS).

In addition, it is intended to include a comparison of different detector calibration methods based on tuneable lasers and also based on the use of conventional incoherent quasi-monochromatic radiation.

Part of the project at the PTB is the TULIP-setup (TUneable Lasers In Photometry) with a set of continuous wave tuneable lasers in the range from 358 nm to 950 nm.

The comparison is laser based and monochromator based calibrations show strong advantages for cw-laser based setup because of its much lower wavelength uncertainty and much higher dynamic range compared to monochromator based setups. It turns out that this is in particular prominent for the calibration of filtered radiometers like pyrometers.

The TULIP facility is actually extended by an femtosecond quasi-CW laser system covering the range from 230 nm up to 3000 nm. A similar picosecond quasi-CW laser system installed at METAS is also in preparation.

Progress Report 2009-02-25

For the calibration of large-area filter detectors in photometry, colorimetry, UV dosimetry and spectroradiometry and for the characterization of luminance standards and spectroradiometers, large-area, high-irradiance monochromatic radiation fields are required with narrow bandwidth tuneable over wide spectral ranges without gaps. Tuneable lasers are adequate sources if co-herence effects (interferences and speckles) of the laser radiation are properly minimized and taken into account, respectively, depending on the type of the radiometric / photometric detec-tor used. Activities in this field have been started in several NMIs (e.g. NIST, NPL, PTB, METAS).

In addition, it is intended to include a comparison of different detector calibration methods ba-sed on tuneable lasers and also based on the use of conventional incoherent quasi-monochromatic radiation.
Part of the project at the PTB is the TULIP-setup (TUneable Lasers In Photometry)
with a set of continuous wave tuneable lasers in the range from 358nm to 950 nm.

A cooperation of the participating countries was agreed.

As a first step, joint investigation regarding the precise determination of the f1’ values of different types of photometers has be carried out in the first half of 2008, where measurements using the laser based setup were compared to classical, monochromator based measurements. The results were published during the meeting of the CIE Division 2 in Turin, Italy.
At PTB, the measurement capabilities have be extended by the tunabel pulsed laser setup PLACOS (Pulsed Laser System for Stray-Light Correction of Spectroradiometers). The wavelength range covered by PLACOS lies between 240 nm and 2400 nml.

Further Information

[Mar 06] It is expected that NPL (GB) and MIKES (FI) are also interested to cooperate