Realization of the unit of luminous flux at the HUT using the absolute integrating-sphere method

Hovila, Jari; Toivanen, P.; Ikonen, Erkki

doi:10.1088/0026-1394/41/6/008

Cited by 18 publications

(23 citation statements)

References 12 publications

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“…At the same time, the PQED method radically simplifies the traceability chain of the photometric unit realization. The increased accuracy of the realization of photometric units would directly translate into a reduced uncertainty in, e.g., luminous flux 29,30,31 and consequently luminous efficacy 32 measurements, which could potentially have significant economic impact.…”

Section: Discussionmentioning

confidence: 99%

Advantages of white LED lamps and new detector technology in photometry

et al. 2015

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Light emitting diode (LED) lighting is becoming more and more popular, as incandescent lamps are being phased out globally. LEDs have several advantages over incandescent lamps, including energy efficiency, robustness, long lifetime, and good temporal stability. The three latter features make LEDs attractive candidates as new photometric standards. Because the spectra of white LEDs are limited to the visible wavelength range, a novel method for the realization of photometric units based on the predictable quantum efficient detector (PQED) can be utilized. The method eliminates the need of photometric filters that are traditionally used in photometry, and instead relies on carrying out the photometric weighting numerically based on the measured relative spectrum of the source. The PQED-based realization simplifies the traceability chain of photometric measurements significantly as compared with the traditional filter-based method. The measured illuminance values of a white LED deviate by only 0.03% when determined by the new and the traditional methods. The new PQED method has significantly lower expanded uncertainty of 0.26% (k 5 2) as compared with that of the traditional filter-based method of 0.42% (k 5 2). Furthermore, when filtered photometers that measure LED lighting are calibrated using LED lamps as calibration sources instead of incandescent lamps, a significant decrease in the uncertainty related to the spectral mismatch correction can be obtained. The maximum spectral mismatch errors of LED measurements decreased on average by a factor of 3 when switching from an incandescent lamp to an LED calibration source.

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Section: Discussionmentioning

confidence: 99%

Advantages of white LED lamps and new detector technology in photometry

et al. 2015

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“…Determining the luminous flux over 4p solid angle around the lamp requires the illuminance measurement over a small solid angle as a calibration procedure. In the absolute integrating sphere method, the luminous flux of the lamp to be measured is compared with an external luminous flux which is produced using a precision aperture and known illuminance [7,8]. If an LED lamp is used as the external source, the PQED method can be used to measure its illuminance.…”

Section: Led Photometrymentioning

confidence: 99%

“…In addition, the spot size of the beam can be simultaneously adjusted to meet criteria given in Eqs. (8) and (9) [28,32]. For analysis of the scanning method and numerical simulations, perfectly Gaussian beam was assumed.…”

Section: Rayleigh-sommerfeld Diffraction Integralmentioning

confidence: 99%

“…The selected beam size and step size in the scanning are selected based on Eqs. (8,9). However, the laser spot size at beam waist w 0 and the waist-to-aperture distance d w are not exactly known in practice.…”

Section: Simulation Geometry and Parametersmentioning

confidence: 99%

“…It can be performed with either a goniometric [5,6] or an absolute integrating sphere method [3,7,8]. Both methods require absolute illuminance measurement as a calibration procedure.…”

Section: Introductionmentioning

confidence: 99%

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Optical aperture area determination for accurate illuminance and luminous efficacy measurements of LED lamps

Dönsberg

Mäntynen

Ikonen

2016

Opt Rev

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The measurement uncertainty of illuminance and, consequently, luminous flux and luminous efficacy of LED lamps can be reduced with a recently introduced method based on the predictable quantum efficient detector (PQED). One of the most critical factors affecting the measurement uncertainty with the PQED method is the determination of the aperture area. This paper describes an upgrade to an optical method for direct determination of aperture area where superposition of equally spaced Gaussian laser beams is used to form a uniform irradiance distribution. In practice, this is accomplished by scanning the aperture in front of an intensity-stabilized laser beam. In the upgraded method, the aperture is attached to the PQED and the whole package is transversely scanned relative to the laser beam. This has the benefit of having identical geometry in the laser scanning of the aperture area and in the actual photometric measurement. Further, the aperture and detector assembly does not have to be dismantled for the aperture calibration. However, due to small acceptance angle of the PQED, differences between the diffraction effects of an overfilling plane wave and of a combination of Gaussian laser beams at the circular aperture need to be taken into account. A numerical calculation method for studying these effects is discussed in this paper. The calculation utilizes the Rayleigh-Sommerfeld diffraction integral, which is applied to the geometry of the PQED and the aperture. Calculation results for various aperture diameters and two different aperture-to-detector distances are presented.

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