Simulating Luminance Distributions of Luminaires from Ray Files (Simulatie van luminantieverdelingen van verlichtingstoestellen op basis van experimentele optische data)

For luminaires having a non-uniform luminance distribution, glare evaluation should be based on luminance maps. However, if the light source within the luminaire is modeled as a ray file, which is essential if the optics surrounding the light source are in close proximity, such luminance maps cannot be simulated directly in ray tracing software. A method that makes use of a brute force ray tracing approach to enable the simulation of luminance maps is presented. While this method yields valid results, it does however require huge amounts of computing power and time. An alternative technique based on ray file sampling in combination with geometrical modeling is presented and discussed. This method does not have the drawbacks of the brute force approach and results in highly accurate luminance distributions. In addition, the impact of the Bidirectional Scattering Distribution Function (BSDF) of a material on the quality of the ray file of a luminaire is investigated. The reflecting properties of a highly diffuse material and a more specular material are modeled in various ways and the impact on the ray file and the corresponding luminance distributions is analyzed. Finally, keeping in mind that the BSDF plays an important role in shaping the near-field, a study is performed to gain insight into how a measured BSDF is influenced by the characteristics of the BSDF measurement setup itself such as beam diameter and detector aperture. In literature, BSDF variations as large as an order of magnitude have been reported in round-robin tests where several labs measured the same sample. Much of these variations can be attributed to the specific design of the measurement device. To minimize this influence, a deconvolution method is presented to reconstruct the true BSDF from experimental data. The subsequent effects of this procedure on the luminance maps is illustrated.Table of contents SIMULATING LUMINANCE DISTRIBUTIONS OF LUMINAIRES FROM RAY FILES Preface ...i Abstract ...iii Samenvatting ...iv List of abbreviations ...vi Table of contents ...vii Chapter 1...1 Introduction 1.1 Optical design of luminaires ...1 1.2 Ray tracing software for imaging/non-imaging optical design ...3 1.3 Measurement equipment ...4 1.3.1 Near-field goniophotometer ...4 1.3.2 Bidirectional Scattering Distribution Function measurement device ... 6 1.4 Research questions ...8 1.5 Overview ...9 Chapter 2...11 Simulating luminance distributions from ray files through brute-force ray tracing 2.1 Introduction ...11 2.2 Brute force methodology ...13 2.2.1 Preparing the model ...13 2.2.2 Data acquisition/selection and luminance map properties ...14 2.2.3 Digital enhancement techniques ...15 2.3 Experimental validation ...17 2.3.1 Experiment setup ...17 2.3.2 Data processing ...19 2.3.3 Applying digital enhancement techniques ...21 2.4 Conclusions ...23 Chapter 3...25 Simulating luminance distributions from ray files through sampling and geometric modeling 3.1 Introduction ...25 3.2 Planar light sources ...26 3.2.1 Introduction ...26 3.2.2 Methodology ...26 3.2.3 Experimental validation ...29 3.2.3.1 Example 1: symmetric planar light source ...30 3.2.3.2 Example 2: asymmetric planar light source ...33 3.2.4 Predefined threshold ...37 3.3 Hemispherical light sources ...39 3.3.1 Introduction ...39 3.3.2 Methodology ...40 3.3.3 Experimental validation ...43 3.4 Conclusions ...50 Chapter 4...53 Impact of the bidirectional scattering distribution function on intensity and luminance distributions of luminaires 4.1 Diffuse materials ...53 4.1.1 Introduction ...53 4.1.2 Experimental set-up...54 4.1.3 MCPET BRDF measurement and modeling ...55 4.1.3.1 Diffuse BRDF model ...55 4.1.3.2 Diffuse/Specular BRDF model ...56 4.1.3.3 Tabular BRDF model ...57 4.1.4 Experimental validation ...58 4.2 Specular materials ...63 4.2.1 Introduction ...63 4.2.2 Experiment set-up ...63 4.2.3 High gloss painted aluminium MCPET BRDF measurement and modeling...64 4.2.3.1 Diffuse/Specular BRDF model ...64 4.2.3.2 Tabular BRDF model ...65 4.2.4 Experimental validation ...66 4.2.5 Final remark ...69 4.3 Conclusions ...70 Chapter 5...73 Bayesian deconvolution method applied to theoretical and experimental Bidirectional Transmittance Distribution Functions 5.1 Introduction ...73 5.2 Bidirectional Scatter Distribution Function ...75 5.3 Bayesian deconvolution ...75 5.4 Bayesian deconvolution applied to simulated BTDF data ...76 5.4.1 Modeling a BSDF measurement device ...76 5.4.2 Defining virtual BTDFs ...78 5.4.3 Deconvolving the simulated BTDFs ...79 5.4.4 Early stopping rule ...81 5.5 Bayesian deconvolution applied to experimental BTDF data ...82 5.5.1 Holographic diffuser 0.5° ...83 5.5.2 Holographic diffuser 5° ...85 5.6 Impact on luminance distributions ...86 5.7 Conclusions ...87 Chapter 6...89 Conclusions 6.1 General conclusions ...89 6.2 Future research ...91 Appendix A...95 Appendix B ...105 Bibliography ...113 Brief biography ...123 List of publications ...125nrpages: 138status: publishe