Tran Quoc Khanh is University Professor and Head of the Laboratory of Adaptive Lighting Systems and Visual Processing at TU Darmstadt in Darmstadt, Germany. He received his PhD in Lighting Engineering from the TU Ilmenau, Germany. He received his Degree of Lecture Qualification (Habilitation) from the same university for his in colorimetry and color image processing. He gained industrial experience as a project manager at ARRI CineTechnik in München (Germany). Tran Quoc Khanh has authored and co-authored numerous scientific publications and invented several patents in various fields of lighting technology.Peter Bodrogi was a Senior Research Fellow at the Laboratory of Adaptive Lighting Systems and Visual Processing at the TU Darmstadt in Darmstadt, Germany. He now works for the ERCO GmbH in Lüschenscheid, Germany, in the field of lighting engineering. He received his PhD in Information Technology. He obtained his postdoctoral qualification at the TU Darmstadt for his thesis on the optimization of modern visual technologies. He is co-author of numerous scientific publications and holds patents in the field of self-luminous display technology and lighting technology.Trinh Quang Vinh is a Senior Research Fellow at the Laboratory of Adaptive Lighting Systems and Visual Processing at TU Darmstadt in Darmstadt, Germany. He received his M.Sc. degree in control engineering. He obtained his Dr.-Ing. degree from TU Darmstadt in 2013. His research topic is the complex mathematical modeling of high-power (phosphor-converted) LEDs, including their electrical, thermal, and optical behavior, as well as their light and color quality. He is co-author of several scientific publications and holds patents in the field of LED lighting technology.

• Preface xvAcknowledgements xvii1 Introduction and Motivations 11.1 Introduction: A Historical Review. Current Issues 1References 52 Fundamentals of Lighting Technology – Basic Visual and Non-visual Aspects 72.1 The Human Visual System. Visual and Non-visual Signal Processing 72.2 Photometric and Colorimetric Quantities 122.2.1 Lighting Technology and Colorimetry 122.2.2 Colorimetry: CIE Tristimulus Values and CIE Chromaticity Diagram 132.2.3 Colour Appearance, Colour Matching, Colour Spaces, and Colour Difference Formulas 162.2.4 The CIECAM02 Colour Appearance Model 182.2.5 CAM02-UCS Colour Space 212.3 Basics of the Non-visual Aspects 212.3.1 Melatonin Suppression at Night 212.3.2 Modelling Melatonin Suppression at Night with the Circadian Stimulus (CS) and the Melanopic Action Factor 232.3.3 Spectral Sensitivity Functions According to the CIE 252.3.4 Correlations Among Circadian Stimulus CS, Melanopic Illuminance, and D65-Equivalent Illuminance 272.3.5 Recommendations of Necessary Melanopic EDI (mEDI) Levels for Optimum Sleep and Daytime Environments and Summary of this Chapter 28References 293 Basic Principles of Human-Centric Lighting and Integrative Lighting 333.1 Basic Questions, General Aspects 333.2 Input Variables – A Systematic Approach 353.3 Brain Processing for the Formation of Subjective and Objective Behavioural Variables 383.3.1 Visual Processing Systems 383.3.1.1 Horizontal Cells of Bipolar Cell Layer 393.3.1.2 Ganglion Layer 403.3.1.3 The Visual Pathway 413.3.1.4 Overall Network Structure of the Visual System: An Overview 423.3.2 Processing Centres and Transmission Pathways for Non-visual Light Effects 433.3.2.1 Light Effects on Mood and Learning 463.3.2.2 General Light Effects on Cognition, Emotion, and Alertness 473.3.2.3 Wavelength Dependence of Brain Activities on Light Exposure 483.4 ‘Timing System’, Circadian Rhythm, and Sleep Behaviour 483.4.1 Questions 483.4.2 Timing System: Entrainment, Timing Role 493.4.3 PRC – Function, Phase Shift 503.4.4 Chronotypes, Sleep Behaviour 513.5 Output Variables of the Visual and Non-visual Brain Processing Apparatus: A Systematics 523.6 Basic Aspects of Human-Centric Lighting/Integrative Lighting 543.7 Tools and Methods for Determining the Subjectively and Objectively Measurable Lighting Effects 573.7.1 Questionnaires for Comprehensive Subjective Determination of Indoor Lighting Quality 573.7.2 Questionnaires on Sleep Behaviour, Sleepiness, and Alertness: The Subjective Basis 583.7.3 Objective Methods and Tools 59References 603.a Appendix A 634 Visual Performance–Work Performance 674.1 Status of Standardisation for Interior Lighting Using the Example of Din En 12464 674.2 Visual Performance 714.2.1 Definition and Influencing Factors 714.2.2 Rea’s RVP Model, 1991 744.2.2.1 Experiments and Results from 1986 744.2.2.2 Experiments and Results from 1988 and Modelling from 1991 764.2.3 The Model of Kokoschka on the Data Basis of Weston 774.3 Work Performance 804.3.1 Assignment of Work Performance Aspects 804.3.2 Model for Stress Regulation Under Poor Lighting 824.3.3 Influence of Lighting Level on Mental Work 834.3.3.1 The Experiments of Boyce 844.3.3.2 The Experiments of Lindner 864.3.4 Influence of Lighting Levels on Work Performance in Industrial Workplaces 884.3.4.1 Literature Review Until 1971 884.3.4.2 Lindner’s Experiments in 1976 904.3.5 Summary of the Significance of the Visual Performance and Work Performance Results – Preliminary Consequences for Indoor Lighting 91References 925 Modern Aspects of Brightness and Visual Clarity in the Context of Light Quality and Visual Performance 955.1 Introduction 955.2 Experimental Method of the Subjective Study 1005.3 Modelling Brightness and Visual Clarity 1025.4 Summary 107References 1086 Colour Quality and Psychophysical–Emotional Aspects, Laboratory Experiments 1116.1 Introduction 1116.2 Preferred Horizontal Illuminance Levels 1126.3 Preferred Luminance Levels on the Wall for a Computer Monitor 1146.3.1 Introduction 1146.3.2 Experimental Method 1156.3.2.1 Test Series 1: Determining the Most Comfortable Display Brightness at a Constant, Typical Wall Luminance 1166.3.2.2 Test Series 2: Determining the Most Pleasant Luminance and Colour Temperature on the Wall with Constant Display Luminance 1186.3.3 Evaluation of the Results 1196.3.4 Summary 1216.4 Preferred Colour Temperatures 1226.4.1 Introduction 1226.4.2 Experimental Method 1236.4.3 Results and Discussion 1276.5 Preferred Ranges of Colour Temperatures and Illuminances 1296.5.1 The Nature of Illuminance and Colour Temperature 1296.5.2 Illuminance and Colour Temperature in the Literature 1306.5.3 Visual Experiments on the Combined Effect of Colour Temperature and Illuminance 1326.5.4 Results: Combined Effect of Colour Temperature and Illuminance 1346.5.5 Dependence of Preferred Colour Temperature and Illuminance on Age and Gender for Activation and Relaxation 1356.6 Preferred White Chromaticities 1376.6.1 Introduction 1376.6.2 Experimental Method 1396.6.3 Results 1396.7 Colour Quality 1406.7.1 Perceptual Aspects of Colour Quality 1416.7.1.1 Naturalness, Colour Fidelity (Colour Rendering) 1416.7.1.2 Vividness 1436.7.1.3 Chromatic Lightness (Brilliance) 1436.7.1.4 Colour Preference 1446.7.1.5 Memory Colours 1446.7.2 Modelling Colour Preference, Naturalness, and Vividness 1466.7.2.1 Modelling of Colour Preference, Naturalness, and Vividness at 750 lx 1466.7.2.2 Modelling Colour Preference at 2000 lx. Comparison of Colour Preference Between 750 and 2000 lx 1496.7.3 Consideration of Red Object Colours in the Colour Preference Model 1506.8 Colour Preference for Skin Tone Lighting 1536.8.1 Introduction 1536.8.2 Method of the Colour Preference Experiment for Skin Tone Illumination 1546.8.2.1 Spectral Measurement of Skin Tones 1546.8.2.2 Characterisation of the Light Sources Used 1566.8.3 Results of Subjective Scaling of Colour Preference for Skin Tone. Optimal Saturation Levels 1596.9 Colour-Rendering Indices and Their Semantic Interpretation 1626.9.1 Introduction 1626.9.2 Methodology of the Experiment on the Semantic Interpretation of the Colour-Rendering Indices 1626.9.3 Results of the Experiment on the Semantic Interpretation of the Colour-Rendering Indices 1646.10 Summary: Preliminary Consequences for Indoor Lighting 166References 1667 New Light-Quality Models from Laboratory Experiments and their Validation in Field Trials 1717.1 Introduction 1717.2 Input and Output Parameters of the Light-Quality Models 1737.2.1 Input Parameters 1737.2.2 Output Parameters 1737.3 Experimental Set-Ups for the Light-Quality Models 1747.4 Equations of the Light-Quality Models 1787.4.1 Brightness 1787.4.2 Visual Clarity (VC) 1797.4.3 Colour Preference (CP) 1807.4.4 Scene Preference (SP) 1837.5 Modelling with the Circadian Stimulus (CS) 1847.5.1 Calculation Method 1867.5.2 Brightness 1867.5.3 Visual Clarity (VC) 1877.5.4 Colour Preference (CP) 1877.5.5 Scene Preference (SP) 1887.5.6 Visualisation of the VC, CP, and SP Models in Contour Diagrams 1887.6 Validation of the Light-Quality Models (in Section 7.4) in Three Museums in Japan 1917.7 Summary 192References 1948 Correlation Analysis of HCL Parameters and Consequences for the Measurement Methods of Non-visual Effects 1978.1 General Consideration of the Correlation of the Parameters for Visual Performance, Colour Quality, and Non-visual Effects 1978.1.1 Introduction 1978.1.2 Evaluation of the Colour-Rendering Indices 2028.1.3 Assessments of the Brightness Parameters 2038.1.4 Melanopic Effect and Colour Rendering 2058.1.5 Correlation Between Further Parameters of Visual Performance, Colour Quality, and Non-visual Effects 2068.2 Structure and Categories of the Input Parameters of the HCL System 210References 2149 Psychophysical–Emotional Aspects – Visual Comfort and Non-visual Effects 2179.1 Psychological–Emotional Aspects of the Effect of Light 2179.1.1 Introduction 2179.1.2 Psychological Effect of the Variable Lighting Situations, Spatial Effects 2209.1.2.1 Field Trial 2219.1.2.2 Laboratory Experiment 2239.2 Space Impression, Space Brightness, and Visual Field Luminance 2279.3 Visual Comfort: Flicker and Stroboscopic Effects 2299.3.1 Pulse Width Modulation and Constant Current Control 2299.3.1.1 Pulse Width Modulation (PWM) 2299.3.1.2 Constant Current Regulation (CCR) 2309.3.2 Flicker and Stroboscopic Effects 2309.3.3 State of Research 2319.3.4 Investigation 2339.3.4.1 Settings 2339.3.4.2 Parameters Investigated 2349.3.4.3 Experimental Procedure 2359.3.5 Results 2369.3.5.1 Mean Subjective Values 2379.3.6 Conclusion 2409.4 Non-visual Light Effects During the Night Hours 2409.4.1 Introduction 2419.4.2 Light Effects in Night Hours with Polychromatic White Light 2429.4.2.1 Results 2439.4.3 Light Effects in Nocturnal Hours with Quasi-monochromatic Light 2469.4.4 Formation of a Metric to Characterise Time-Dependent Melatonin Suppression 2499.4.5 Determining the Potential Causes of Melatonin Suppression in Nocturnal Hours 2539.4.6 Lighting Aspects for Shift Work 2549.5 Psychological and Health Aspects of Daylight 2619.5.1 Psychological Aspects 2619.5.2 Health Aspects of Daylight 2639.5.3 Quantitative Characteristics of Daylight and Electric Light – A Comparison 2659.6 Influences of Light Intensity and Timing of Light Exposure on Sleep Behaviour 2719.7 Light Effects on Alertness – Literature Analysis of Various Publications 2759.7.1 Alertness in the Evening and Night Hours 2759.7.2 Alertness in the Daytime 2769.8 Results of the Effect of Light on Alertness and Sleepiness During the Early Shift in an Industrial Company 2819.8.1 Results of the Data Evaluation 2839.8.2 Summary and Discussion 284References 28410 Practical HCL Light Measurement Technology Indoors and Outdoors 29110.1 Introduction 29110.2 Hypotheses and Questions for HCL Light Measurement Technology 29310.3 Light Measurement Aspects 29610.3.1 Size of the Viewing Field 29610.3.2 Current Definitions of Circadian-Effective Irradiance 29710.3.2.1 DIN Evaluation Procedure 29810.3.2.2 Procedure according to M. Rea and Figuiero 30010.3.2.3 Use of the Definitions for the Metrics MDER and MEDI according to CIE, Which Have Been Described in Chapter 2 (Section 2.2.3) of this Book 30210.3.3 Calculation of the Circadian Stimulus CS from Vertical Illuminance and Chromaticity Coordinate z 30210.3.4 Computation of the Circadian Stimulus CS from Vertical Illuminance and Correlated Colour Temperature CCT 30510.4 Circadian-Effective Irradiation Outdoors and Indoors by Integral Field Measurements 30710.4.1 Field Measurements in Winter 30910.4.2 Field Measurements on a Summer Day 31010.4.3 Field Measurements on the Evening of an Autumn Day 31210.5 Daylight Measurement–Spectral Measurement and Practical Approaches 31410.5.1 Spectral Measurement of Daylight Spectra 31410.6 HCL – Light Measurements at Office Workplaces 32010.6.1 Measured Variables and Measurement Technology 32010.6.2 Measurement Set-Up 32110.6.3 The Rooms in which the Measurement Took Place 32210.6.4 Measurement Results at Different Office Workplaces 32410.7 Calculation of the Metrics MDER and MEDI from Vertical Illuminance and Chromaticity Coordinate z 32610.7.1 Definition of MDER and MEDI According to CIE-Publication 32610.7.2 Mathematical Transformation for Calculation of MEDI and MDER 328References 33111 Technological Aspects of Human Centric Lighting in Buildings 33511.1 Introduction to the Topic ‘Smart Lighting’ 33511.2 Technical Principles of Smart Lighting 34011.3 Cloud Software Structure and Use Cases 34911.4 Light Control and Spectral Optimisation for High-Quality and Healthy Light 35311.4.1 Stages of the Realisation Possibilities of the Luminaires for HCL Lighting Technology 35311.4.2 Levels 1 and 2 with Constant Colour Temperature 35311.4.2.1 Basic Data of Circadian Effectiveness 35311.4.2.2 Previous Technologies for Generating White LED Light 35511.4.2.3 Newer Technologies for the Generation of White LED Light with Only One Colour Temperature 35611.4.3 Levels 3 and 4 (Figure 11.17) with Variable Colour Temperature and Variable Illuminance 36111.4.4 Level 5 (Figure 11.17) with Variable Colour Temperature, Variable Illuminance, and High Colour Quality 36411.4.5 Level 6 with Variable Colour Temperature, Variable Illuminance, and Daylight Consideration 36511.4.5.1 Introduction 36511.4.5.2 Variation of Daylight and Consequences for Indoor Lighting – Result of a Measurement 36611.4.5.3 Approaches to Considering Daylight Components in Interior Space 36811.5 Measurement of Melanopic-Equivalent Daylight Illuminance (MEDI) with RGB Colour Sensors 37211.5.1 Introduction Into the Context 37211.5.2 RGB Colour Sensors: Characterisation and Signal Transformation 37211.5.2.1 Characterisation of RGB Colour Sensors 37211.5.3 Method of Signal Transformation from RGB to XYZ 37611.5.4 Matrix Transformation in Practice, Verification with an Actual RGB Colour Sensor 37711.5.5 Measurement of the Non-visual Quantities MEDI and MDER 37811.5.6 Summary 382References 38412 HCL-Oriented Lighting Design: Basic Aspects and Implementation 38712.1 Classification of HCL-Oriented Lighting Quality Concepts 38712.1.1 Conceptions and Thought Processes on Lighting Quality Until 2002 38712.1.1.1 Flynn et al. 38812.1.1.2 Rowlands and Loe 38912.1.1.3 Veitch and Newsham 38912.1.2 Literature Analysis and New Thoughts on Lighting Quality 39312.1.3 Summary of the Concepts on HCL and Lighting Quality – A Draft Overall Concept 39612.2 Lighting Design: The Process and the Influencing Factors to Achieve Lighting Quality 39712.2.1 Goals and Classification of HCL-Oriented Lighting Design 39712.2.2 Process Steps of HCL-Oriented Lighting Design 39912.3 Daylight and Daylight Planning 40412.3.1 Introduction 40412.3.2 Daylight from a Lighting Design Perspective – Daylight Design in the Context of Standardisation 40512.3.3 Daylight Planning for Non-visual Effects 40712.3.4 Some Data on Daylighting Effects 40812.4 Specification of HCL Lighting Systems for Daytime – Draft Recommendation 40912.4.1 Introduction 40912.4.2 Illumination Level, Circadian-Effective Illuminance Levels 41012.5 Dynamic Lighting, Control Curves 41812.6 Lighting for Users with Higher Lighting Requirements 42512.6.1 Vision in Old Age – Some Aspects 42612.6.2 Lighting for Elderly People’s Homes and People Suffering from Dementia 43112.6.3 Proposal for Lighting Design for Elderly People’s Homes and Nursing Homes 433References 43613 Numerical Relationship Between Non-visual Metrics and Brightness Metrics – Consequences for the Evaluation of HCL Systems and Facilities 44313.1 Introduction 44313.2 Brightness Perception and Modelling 44513.3 Circadian Stimulus Models CS 2018 and CS 2021 44613.3.1 The Circadian Stimulus (CS) Models 2005 and 2018 44713.3.2 The Circadian Stimulus Model 2021 44813.4 The Formula of Giménez et al. for Nocturnal Melatonin Suppression 45013.5 Numerical Analysis of the Relationship Between Brightness and Non-visual Metrics 45113.5.1 Introduction 45113.5.2 Method of Correlation Analysis 45213.5.3 Relation Between the Linear Brightness Metrics and the Non-visual-Effect Parameters 45213.5.4 Relation Between Non-linear Brightness Metrics and Non-visual-Effect Parameters 455References 45714 Summary and Outlook 45914.1 Summary 45914.2 Outlook 463Index 465