Contents Preface xiii Acknowledgements xiv 1 Introduction 1 1.1 History of light sources 1 2 Fundamentals 2.1 The electromagnetic spectrum 2.2 Optical radiation 2.3 Ultraviolet and infrared radiation 2.4 Continuous and discontinuous radiation 2.4.1 Spectral power distribution (SPD) 2.5 Black body radiation 2.6 Wavelength, frequency and the velocity of propagation of light 8 2.7 Radiant flux and radiant efficiency 8 2.8 Luminous flux, luminous efficacy and luminous efficiency 8 2.9 Luminous intensity 8 2.10 Illuminance and luminance 9 2.11 Luminosity 10 3 Laws of illumination 11 3.1 Inverse square law 11 3.2 Cosine law 12 3.3 Combination law 14 3.4 Relationship between luminous intensity and luminous flux 15 3.5 Relationship between illuminance and luminance 16 3.6 Specular reflection 17 3.7 Refraction 18 3.8 Dispersion 18 vi Contents 3.9 Absorption and scattering 19 3.10 Diffuse reflection and diffuse transmission 20 4 Physiology and characteristics of vision 21 4.1 Introduction 21 4.2 Structure of the human eye 21 4.3 Photoreceptors - rods and cones 23 4.4 Neurophysiology 25 4.5 Formation of images on the retina 25 4.6 Blind spot 27 4.7 Excitation of rods 27 4.8 Excitation of cones 28 4.9 Visual pathway 29 4.10 Spectral sensitivity of the eye 30 4.11 Radiation and the eye 32 4.12 Visual threshold 32 4.13 Photopic and scotopic vision 33 4.14 Mesopic vision 34 4.15 Visual discrimination 35 4.16 Accommodation, convergence and stereopsis 35 4.17 Field of vision 38 4.18 Adaptation 38 4.18.1 Dark adaptation 38 4.18.2 Light adaptation 40 4.18.3 Problems associated with twilight 40 4.18.4 Colour adaptation 41 4.19 Visual acuity 41 4.19.1 Photopic acuity 43 4.19.2 Relationship between cones and visual acuity 43 4.19.3 Scotopic acuity 44 4.19.4 Static and dynamic visual acuity 45 4.20 Visual perception 45 4.20.1 Perception by sight 46 5 Defects and anomalies of vision 47 5.1 Introduction 47 5.2 Glare 47 5.2.1 Induction and disability glare 47 5.2.2 Phototropism and discomfort glare 48 5.3 Persistence of vision 49 5.4 After-images 49 5.5 Flicker 49 5.6 Hypermetropia 50 5.7 Myopia 50 5.8 Presbyopia 51 5.9 Astigmatism 52 5.10 Diplopia 52 5.11 Colour blindness 53 5.11.1 Monochromats 53 5.11.2 Dichromats 53 Contents vii 5.11.3 Trichromats 53 5.12 Colour vision tests 53 5.13 Night blindness 54 5.14 Effects of age 55 5.15 Glaucoma 55 6 Colour 56 6.1 Colour definitions and terminology 56 6.1.1 Hue, lightness and saturation 56 6.1.2 Munsell colour solid 56 6.2 CIE chromaticity diagram 57 6.3 Planckian radiator 57 6.4 Dominant wavelength 59 6.5 Chromaticity of the visible spectrum 60 6.6 Lamp colour appearance 61 6.7 Colour temperature and correlated colour temperature 61 6.8 Colour rendering and colour rendering index (CRI) 63 6.9 Colour contrast 65 6.10 Colour perception and production 66 6.11 Colour mixing and complementary colours 67 6.12 Colour coding 68 6.12.1 Colours used for transport signals 70 6.13 Metamerism 70 6.14 Photochromism 71 6.15 Achromatic interval 71 6.16 Effects of environmental colour on individuals 72 7 Natural and artificial light sources 73 - 7.1 Daylight 73 7.2 Availability of daylight 73 7.3 Daylight factor 74 7.4 Emission of light from heated bodies 75 7.5 Types of spectra 76 7.6 Emission of light from gas discharges 77 7.7 Tungsten lamps 78 7.7.1 Tungsten filament lamps 78 7.7.2 Tungsten halogen lamps 79 7.7.3 Dichroic reflector lamps 81 7.8 Discharge lamps 82 7.8.1 Introduction 82 7.8.2 Low pressure mercury or fluorescent lamps 84 7.8.3 High pressure mercury vapour lamps 86 7.8.4 Metal halide lamps 87 7.8.5 Low pressure sodium lamps 88 7.8.6 High pressure sodium lamps 91 7.8.7 Induction lamps 92 7.9 Lasers 93 7.9.1 Display laser lighting installations 94 7.10 Optical fibres 95 7.11 Luminescence 95 viii Contents 7.12 Lamp characteristics 96 7.12.1 Lamp designations 96 7.12.2 Lamp efficacy 96 7.12.3 Lamp life 98 7.12.4 Lamp applications 98 7.12.5 Lamp run-up efficiency 98 7.13 Blue light hazard 100 7.14 Lamps used for other than normal lighting applications 100 7.15 Standard illuminants 102 7.16 Beta lamps 103 7.17 Tyndall beam lamp 104 7.18 Handling of new lamps and the disposal of spent lamps 105 7.19 Ultraviolet radiation from tungsten halogen lamps 106 7.20 Ultraviolet radiation from high intensity discharge lamps 107 7.21 Effects of operating broken mercury vapour and metal halide lamps 107 8 Luminaires 109 8.1 Introduction 109 8.2 Optical control of light output from luminaires 110 8.3 Distribution of light from luminaires 112 8.3.1 Polar diagram 113 8.3.2 Isocandela diagram 113 8.3.3 Isolux diagram 113 8.4 Luminaires for hazardous and hostile environments 113 8.5 Classification of luminaires according to relevant British Standards 115 8.5.1 BS 4533 115 8.5.2 BS 5345 115 8.5.3 BS 6467 116 8.6 Downlighter luminaires 116 8.7 Air handling luminaires 117 8.8 Uplighter luminaires 117 8.9 Luminaire materials 118 8.10 Mechanical strength of luminaires 119 8.11 Control gear 119 8.12 Electromagnetic interference (EMU and radio frequency interference (RFI) 120 8.13 Polychlorinated biphenyls (PCBs) 120 9 Lighting for interior applications 121 9.1 Introduction 121 9.2 Office lighting 121 9.3 Techniques and practice of interior lighting 122 9.4 Lumen method of lighting design 123 9.5 Preferred illuminance and luminance ratios for interiors 124 Contents ix 9.6 Lighting for areas containing display screen equipment 125 9.7 Uplighter installations 125 9.8 Lamp types for use in interiors 128 9.9 Methods of reducing glare from windows 129 9.9.1 Temporary methods 129 9.9.2 Permanent methods 129 9.10 Room index 130 9.11 Automatic control of lighting within offices 130 9.12 Emergency lighting 132 9.12.1 Emergency escape lighting 132 9.12.2 Stand-by lighting 132 9.12.3 Escape route lighting 132 9.12.4 Open area (anti-panic area) lighting 133 9.12.5 High risk area task lighting 133 9.12.6 Luminaires for use in emergency lighting installations 133 9.13 Sick building syndrome and building related illness 133 10 Lighting for external applications 135 10.1 Introduction 135 10.2 Factories 135 10.2.1 General factory external layout lighting 135 10.2.2 Lighting for loading bays 136 10.2.3 Lighting for storage areas 136 10.3 Security lighting 137 10.3.1 Security lighting for shops and small premises 138 10.3.2 Security lighting for offices 138 10.3.3 Security lighting for factories 139 10.4 Floodlighting 140 10.4.1 Building floodlighting 140 10.4.2 Industrial floodlighting 141 10.4.3 Sports floodlighting 143 10.5 Public lighting 143 10.5.1 Road lighting 144 10.5.2 Tunnel lighting 145 10.6 Lighting for externally located advertising signs 146 10.7 Lighting for use with closed circuit television (CCTV) systems 146 10.8 Light pollution 148 10.8.1 Causes 148 10.8.2 Remedies 149 11 Visual task lighting 150 11.1 Introduction 150 11.2 Importance of lighting in the workplace 150 11.3 Analysis of the working visual task 151 11.4 Visibility of an object 153 11.5 Factors influencing the ability to see detail 153 11.6 Quality of illumination 154 x Contents 11.7 Visual comfort 154 11.8 Glare in the working environment 156 11.8.1 Control of discomfort glare 156 11.8.2 Direct and reflected glare 157 11.9 Veiling reflections 159 11.10 Use of daylight for task lighting 161 11.11 Luminance contrast and contrast rendering factor (CRF) 162 11.12 Uniformity ratio and diversity ratio 164 11.13 Spacing-to-height ratio (SHR) 164 11.14 Influence of illuminance on human visual characteristics 165 11.15 Flicker and the stroboscopic effect 165 11.16 Light modulation 166 11.17 Loss of perception 168 11.18 Poor task lighting - effects on worker posture 168 11.19 Effects of age of individual on task vision 169 11.20 Preferred task lighting strategies 171 11.21 Typical recommended illuminance values 173 12 Lighting for specific industries and occupations 175 12.1 Introduction 175 12.2 Lighting for inspection 175 12.2.1 General inspection lighting techniques 175 12.2.2 Detection of form defects 175 12.2.3 Detection of detail defects 177 12.2.4 Detection of colour defects 177 12.2.5 Special techniques for inspection lighting 177 12.3 Lighting for engineering workshops 178 12.4 Lighting for textile and clothing manufacturing industries 179 12.5 Lighting for building and construction sites 179 12.6 Lighting for electrical and electronic equipment manufacture and assembly 181 12.7 Lighting for food and drink industries 181 12.8 Lighting for metal working industries 182 12.9 Lighting for furniture and timber industries 182 12.10 Lighting for glass industries 182 12.11 Lighting for premises used for health care 182 12.12 Lighting for paper and printing industries 183 12.13 Lighting for mining 183 12.14 Lighting for hazardous and hostile environments 184 12.15 Lighting for dockyards and shipbuilding 184 12.16 Lighting for horticulture 185 12.17 Workers exposed to ultraviolet radiation 185 13 Lighting and display screen equipment 187 13.1 Introduction 187 13.2 Radiation associated with the use of display screen equipment 187 Contents xi 13.3 Screen image 188 13.3.1 Resolution 190 13.3.2 Flicker and refresh rate 190 13.3.3 Jitter 191 13.3.4 Screen contrast 191 13.3.5 Active and passive displays 191 13.3.6 Cathode ray tubes (CRTs) 191 13.3.7 Liquid crystal displays (LCDs) 191 13.4 Glare control on VDU screens 191 13.5 Lighting for VDU areas 192 13.6 Optimum conditions for visual comfort in display screen equipment operators 194 14 Lighting surveys 197 14.1 Introduction 197 14.2 Instrumentation 197 14.2.1 Illuminance measuring equipment 198 14.2.2 Luminance measuring equipment 198 14.2.3 Daylight factor meters 198 14.3 Survey methods 198 14.3.1 Determination of the minimum number of measuring points 199 14.3.2 Presentation of information 199 14.3.3 Method of separating illuminance contributions due to daylight and artificial lighting 202 14.4 Interpretation of the data obtained 203 14.5 Recommendations 204 15 Legislation 206 15.1 Overview 206 Appendix A: Legislation in the United Kingdom 207 A.l Introduction 207 A.2 Acts, regulations and approved codes of practice 208 A.3 The law relating to lighting 208 A.3.1 Management of Health and Safety at Work Regulations 1992 208 A.3.2 Wgrkplace (Health, Safety and Welfare) Regulations 1992 209 A.3.3 Health and Safety (Display Screen Equipment) Regulations 1992 210 A.3.4 Health and Safety (Safety Signs and Signals) Regulations 1996 210 A.3.5 Provision and Use of Work Equipment Regulations 1998 210 A.3.6 Electricity at Work Regulations 1989 211 A.3.7 Electromagnetic Compatibility Regulations 1992 211 A.3.8 Docks Regulations 1988 212 xii Contents A.3.9 Electrical Equipment (Safety) Regulations 1994 212 A.3.10 Supply of Machinery (Safety) Regulations 1992 212 A.3.11 Control of Substances Hazardous to Health Regulations 1994 212 A.3.12 Special Waste Regulations 1996 (as amended) 213 A.4 Compliance with health and safety law 213 References 215 Suggested further reading 217 Index 219 Chapter I2 Lighting for specific industries and occupations 12. I Introduction It is not possible to include lighting applications which are applicable to all industries and occupations, but a selection is included which is considered to be representative. 12.2 Lighting for inspection The inspection of products in a production process is a necessary element in monitoring the final quality of the finished article. The inspec- tion may occur at various stages during the manufacture of a compo- nent, but will invariably include an inspection of the final article. The purpose of inspection, including visual inspection, is to identify any individual feature of the component which, if left undetected, would render it unsuitable for the purpose for which it is intended. It will be evident that suitable and sufficient lighting contributes significantly to the overall process of visual inspection. 12.2. I General inspection lighting techniques The role of lighting for inspection is to improve the visibility of any features of a product which would subsequently lead to its rejection as a serviceable item. There is a multitude of manufactured products and each one of them will have a different combination of features which may prove defective in some way. It follows therefore that the optimum inspection lighting required will vary from product to product. It will be necessary to perform a visual task analysis in an attempt to achieve optimum task lighting conditions. Those factors which are to be consid- ered in such an analysis include: 176 Lighting for Health and Safety The characteristics of the whole product which contains individual features which are required to be inspected, i.e. general shape of the product (two or three-dimensional), constitution of the product, e.g. transparent, translucent or opaque and surface finish qualities of the product, e.g. matt or specular. The individual features within the whole product which require inspection include form, detail and colour. Features of form are not generally restricted to small size features and often tend to be seen as part of the whole product, an example being inconsistencies in the bodywork finish of a motor vehicle which become more apparent when the whole vehicle body is viewed. Conversely features of detail are small and can normally be detected when only part of the product is being inspected, an example being a crack in the surface of some solid material. It will be evident that the size of a product will not usually influence colour features which require inspection. Each individual inspection process has to be considered on its own merits and it follows that each process will require careful consideration in respect of the most appropriate lighting. However, as a general guide, features of form are usually best illuminated by luminaires with strong and clearly defined directional qualities of light output. Inspection of features of detail are normally revealed more easily when the illumi- nance levels are increased. The inspection of the surface colour features of a product is a process which is heavily dependent upon the spectral characteristics of the light sources used. Section 6.8 shows how the spectral power distribution of light reflected from the surface of an object is influenced by the combination of the spectral power distribution of the light source used and the spectral reflectance characteristics of the object being illuminated. 12.2.2 Detection of form defects In general the form which a product appears to exhibit is strongly influ- enced by: the structural arrangement of the product; the manner in which it is lit; and the reflection characteristics of the material from which the product is constructed. In combination these will lead to the development of three characteris- tic patterns: illuminance; highlight; and shadow. The complexity of products and of manufacturing processes necessitate that lighting for discrimination of form be considered on its individual