Construction of Two-Axis Goniophotometer for Measurement of Spatial Distribution of a Light Source and Calculation of Luminous Flux

“…If an LED lamp is used as the external source, the PQED method can be used to measure its illuminance. Goniophotometers, on the other hand, determine the total luminous flux by measuring the illuminance of the light source at various solid angles [5,6]. The illuminance responsivity of the detector used in the goniophotometer can be calibrated against the PQED.…”

Section: Led Photometrymentioning

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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“…Для зменшення фонового освітлення фотометра перевідбитим від стін «чорної кімнати» світлом можна використовувати діафрагму, яка монтується на фотометр [4]. розкрив діафрагми обирається в залежності від співвідношення максимального розміру ОВ та відстані між центром обертання гоніометра та фотометром.…”

Section: рис 3 використані ов з відповідними кссunclassified