Analysis of misalignment-induced measurement error for goniophotometry of light-emitting diode arrays

Cai, Wentao; Liu, Xianming; Li, Xiaohua; Chen, Weimin

doi:10.1364/ao.52.008381

Cited by 3 publications

(4 citation statements)

References 14 publications

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“…Similar misalignment effects have been studied experimentally in [34]. A Lambertian emitter with a circular ground plane and a radius of 5.625 mm was used as a light source within our investigations.…”

Section: Applicationmentioning

confidence: 63%

Virtual experiment for near-field goniophotometric measurements

et al. 2014

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Near-field goniometric measurements are employed to determine the photometric characteristics of light sources, i.e., the spatial and angular distribution of the emitted light. To this end, a complex measurement system consisting of a goniometer and a CCD-based imaging photometer is employed. In order to gain insight into the measurement system and to enable characterization of the whole measurement setup, we propose to apply a computer model to conduct virtual experiments. Within the computer model, the current state of all parts of the virtual experiment can be easily controlled. The reliability of the computer model is demonstrated by a comparison to actual measurement results. As an example for the application of the virtual experiment, we present an analysis of the impact of axial malpositions of the goniometer and camera.

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Section: Applicationmentioning

confidence: 63%

Virtual experiment for near-field goniophotometric measurements

et al. 2014

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“…In this section, we will validate the luminous intensity correction method through numerical simulations. To prove the feasibility and robustness of the presented algorithm, like previous researchers, 9,14 we choose three different types of LEDs, whose LIDs produce circular, elliptical and circular ring shapes ( Figure 5). In addition, several high packaging density 4 Â 4 rectangular LED arrays are used in the virtual experiments, whose LED-to-LED spacing is 6.45 mm along the x-axis and 5.45 mm along the y-axis ( Table 1).…”

Section: Simulationmentioning

confidence: 92%

“…The far-field goniophotometer we used to do the validation experiments uses a system of Ameasurement plane. According to the photometric inverse-square law, 9,14 the luminous intensity of a LED array in a certain direction (A, ) and at a certain distance r is given by…”

Section: Theorymentioning

confidence: 99%

“…As for the far-field method, according to the steepness of the gradients in the luminous intensity distribution (LID), the test distance between the detector and the light source should be larger than the critical far-field distance recommended by the global LED measurement standard CIE S 025/E: 2015. 13 Furthermore, some recent related literature 14,15 has shown that the measurement errors are still significantly impacted by misalignment effects even when meeting the far-field condition. Indeed, for some common unconventional light sources based on LEDs, such as shaped light sources with varying configurations in respect of geometry and/or mounting base, light sources with multiple light-emitting areas, and large-sized light sources incorporating electrical, optical, mechanical, and thermal components and interfaces, etc., it is sometimes difficult to position them at the goniometer's reference point even when an alignment laser is used, due to the lack of a specially customised fixture, the mechanical limitations of the sophisticated adjustment stage, 16 or the size of measurement setup.…”

Section: Introductionmentioning

confidence: 99%

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Luminous intensity correction method for misalignment-induced measurement error of light-emitting diode arrays

Cheng

Feng

et al. 2018

Lighting Research & Technology

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To eliminate axial misalignment-induced measurement errors of discrete light-emitting diode arrays in the far-field condition, a robust and effective method for correcting the measured luminous intensity distribution is proposed. The precision of the correction can be determined beforehand by setting a criterion which can also be used to determine the required test distance. To validate the feasibility and practicability of the proposed approach, numerical simulations of light-emitting diode arrays with three kinds of typical luminous intensity distributions were performed. In addition, the test distances as a function of the light-emitting diode luminous intensity distribution, packing density and dimensions under translational misalignment were analysed. Some beneficial operating methods and rules for practical application are summarised. Finally, physical measurements of several experimental examples were collected. The correction results agreed with the desired data and again proved the utility of the presented method.

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Off-axis limiting photometric distance of Lambertians and narrow beams

Dotreppe,

Audenaert,

Scheir

et al. 2023

Lighting Research & Technology

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The near-field - far-field disparity of light sources leads to discussion within the lighting community. In the far-field, light sources are approximated by a point source with a luminous intensity distribution from which other photometric quantities can be computed. In the near-field, light sources must be considered as extended sources and no closed-loop analytical solutions can be found for the illuminance in off-axis directions. The illuminance allows to compute the apparent intensity used for the assessment of the limiting photometric distance (LPD), that is, the threshold between near- and far-field regions. Numerically, the illuminance can be determined through a discretisation of the luminous surface. This approach is verified for on- and off-axis directions through direct comparison with ray tracing simulations based on near-field goniophotometric measurements. A good match is observed for Lambertian and narrow beam light sources. Using the numerical approach, the LPD in all directions is assessed. For light sources of which the luminous intensity strictly decreases while moving away from the optical axis, the LPD decreases as well until a minimal value is reached. After this, the LPD increases again, in certain scenarios up to values resulting in the invalidity of the inverse square law.

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Analysis of misalignment-induced measurement error for goniophotometry of light-emitting diode arrays

Cited by 3 publications

References 14 publications

Virtual experiment for near-field goniophotometric measurements

Virtual experiment for near-field goniophotometric measurements

Luminous intensity correction method for misalignment-induced measurement error of light-emitting diode arrays

Off-axis limiting photometric distance of Lambertians and narrow beams

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