Many different applications require the precise acquisition of the spatial intensity distribution of a light source. Examples are measurements of M2 (beam quality parameter), numerical aperture (of an optical fiber), or light source characterization. The presented work shows the development and validation of a photonic instrument for spatially resolved precise light power measurement at different distances. The instrument consists of a XY-stage with a calibrated detector. It is located in a dark room with an additional black carpet to reduce stray light even from the surrounding. We designed and built a fully automated measurement device including data processing. Different sources can be measured at a freely selectable distance (Z direction) between source and detector. The detector is a photodiode with a transimpedance amplifier (calibrated). In front of the detector, an aperture ensures a precise XY resolution. The scan area is 52 mm in X and Y direction with the smallest step size of 0.2 μm and a repeatability error of less than 0.5 μm. The aperture is currently limited to ≥ 0.4 mm (diameter) due to mechanic reasons at our lab. From repeatability testing, we calculated the accuracy of the current instrumentation: a 2s experimental standard deviation of less than 0.8 %. Such a photonic instrument is the base for precise optical beam profile measurements.
Future cars enable more use of interior lighting with special visual effects. In order to optimize visual effects, the light scattering behavior of these materials must be precisely characterized. We present the development of a photonic instrument for light scattering measurements in terms of BSDF (bi-directional scattering distribution function). The instrument is principally a goniophotometer. We designed and built a fully automated BSDF measurement device including data processing optimized for low light signals including evaluations and justifications. Due to these optimizations, the photonic device has currently an accuracy of less than 0.08 % (2 sigma standard deviation). In addition, the dynamic range is currently about 10 decades. We will implement further optimization steps soon.
KEYWORDS: Light scattering, Visualization, Signal to noise ratio, Light sources and illumination, Goniophotometry, 3D acquisition, Visual optics, Scattering, Scatter measurement
Autonomous driving enable more use of in-vehicle interior lighting effects using advanced interior materials for illumination. Targeting premium visual ergonomics requires additional know how of today’s and future materials regarding light scattering. Within the presented work, we improved a goniophotometer towards a 2 standard deviation of < 0.08 %. This is in the range of a suitable limit so we successfully measured light scattering in terms of BSDF and/or BTDF of wood, transparent plastic (including 3D printed), and leather. These materials scatter light differently, so the results enable the base for optical simulation tools to design special visual effects.
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