A method for the simultaneous correction of bandpass and stray-light effects in array spectroradiometer data is presented. The method is based on the inversion of the instrument matrix of a device determined with the help of tuneable lasers. By applying the Tikhonov regularization technique, a straightforward correction of the measurement results is possible.

Based on extensive investigations of almost 100 high-power quartz-halogen lamps covering thirteen different types, seven different manufacturers and different batches with a total operating time of about 27000 h, a new type of lamp (1000 W T6 modified FEL-type lamp, Osram Sylvania Inc.) has been selected and its operating conditions have been optimized. This lamp, which after seasoning is about ten times more stable than the best lamps used before, is recommended as a reference and transfer standard of spectral irradiance in the whole range between 250 nm and 3 µm. While excellent short-term and long-term stability over operating times of several hundreds of hours can be achieved, the disadvantages of the new standard lamp lie in a long seasoning time (80 h to 100 h) and a noticeable sensitivity of the seasoned lamps to shock and vibrations. Typical results of the characterization, calibration and reproducibility of the new standard lamp are presented and discussed in order to illustrate its performance and to demonstrate how to use it under optimal operation conditions.

This paper describes the analysis of laser-based responsivity measurements using the Tunable Lasers in Photometry setup at the Physikalisch-Technische Bundesanstalt. An approach based on digital signal analysis is proposed to remove interference-caused oscillations in highly resolved spectral data from laser-based measurements, yielding an improved reproducibility and comparability of results. Digital filters are used to selectively suppress the frequency components of interference fringes visible in the measurement data. We describe the algorithm used and discuss the associated uncertainty components of laser-based measurements. Finally, we give examples of the calibration of different detectors with and without interference effects.

Compact and cost-effective array spectroradiometers are increasingly used in photometric and radiometric measurements. In this report, results of the colorimetric characterisation of LEDs using both low-end and high-end array spectroradiometers are compared to those obtained with the help of a conventional scanning double-monochromator spectroradiometer. Problems related to the utilisation of the array spectroradiometers for such applications are discussed. Effects of the most important instrumental parameters, such as the stray light suppression and the bandpass irregularities, are also assessed. The comparison showed an agreement among the results provided by the different spectroradiometers within the typical uncertainty levels, even for the low-end devices.

In this paper, we present the near-field goniophotometer setup recently installed at PTB for the photometric characterization of solid-state light sources, e.g. LEDs, under near-field conditions. Moreover, as a validation of the near-field goniophotometric measurements, the luminous intensity distribution of two LEDs determined by near-field measurements is also presented and compared with those carried out separately under far-field conditions using a photometer.

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High-power quartz-halogen lamps have been in use as transfer standards for a long time. However, even the best lamps available are not stable enough to match the increasing requirements stemming from the progress of measuring techniques. In particular, long-term stability in the ultraviolet-B region has to be improved. In order to achieve higher stability, it is necessary to change the operating conditions from constant-current to a detector-controlled system. The new OMTec transfer-standard system, consisting of a control unit including power supply and a lamp detector unit, is described. Its main features are: long-term stability with a deviation of the spectral radiant flux from the calibration values of less than 3 × 10-5 h-1 during nearly 400 hours of operating time throughout the spectral range from the ultraviolet-B to the near-infrared; continuous check on stability by monitoring and viewing the measured detector photocurrents; reduction of the required seasoning time by a factor of three thus enhancing the lifetime of the lamp; storage of lamp and calibration data in the lamp detector unit for external use.

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