All chapters have been completely revised and expanded and a new chapter has been added to reflect recent developments in the field and report on the progress made within the last decade.
In addition there is now an even stronger focus on real-life examples, with 20% more case studies taken from science and industry. For ease of comprehension the text is backed by more than 590 images which include graphic visualizations and more than 300 infrared thermography figures. The latter include many new ones depicting, for example, spectacular views of phenomena in nature, sports, and daily life.
Table of Contents
Preface to Second Edition XVII
Preface to First Edition XIX
List of Acronyms XXIII
1 Fundamentals of Infrared Thermal Imaging 1
1.1 Introduction 1
1.2 Infrared Radiation 6
1.2.1 ElectromagneticWaves and the Electromagnetic Spectrum 6
1.2.2 Basics of Geometrical Optics for Infrared Radiation 10
1.2.2.1 Geometric Properties of Reflection and Refraction 10
1.2.2.2 Specular and Diffuse Reflection 12
1.2.2.3 Portion of Reflected and Transmitted Radiation: Fresnel Equations 12
1.3 Radiometry and Thermal Radiation 14
1.3.1 Basic Radiometry 15
1.3.1.1 Radiant Power, Excitance, and Irradiance 15
1.3.1.2 Spectral Densities of Radiometric Quantities 15
1.3.1.3 Solid Angles 16
1.3.1.4 Radiant Intensity, Radiance, and Lambertian Emitters 17
1.3.1.5 Radiation Transfer between Surfaces: Fundamental Law of Radiometry and View Factor 20
1.3.2 Blackbody Radiation 21
1.3.2.1 Definition 21
1.3.2.2 Planck Distribution Function for Blackbody Radiation 22
1.3.2.3 Different Representations of Planck’s Law 24
1.3.2.4 Stefan–Boltzmann Law 26
1.3.2.5 Band Emission 26
1.3.2.6 Order-of-Magnitude Estimate of Detector Sensitivities of IR Cameras 29
1.4 Emissivity 31
1.4.1 Definition 31
1.4.2 Classification of Objects according to Emissivity 32
1.4.3 Emissivity and Kirchhoff’s Law 32
1.4.4 Parameters Affecting Emissivity Values 34
1.4.4.1 Material 34
1.4.4.2 Irregular Surface Structure 34
1.4.4.3 Viewing Angle 35
1.4.4.4 Regular Geometry Effects 39
1.4.4.5 Wavelength 41
1.4.4.6 Temperature 42
1.4.4.7 Conclusion 43
1.4.5 Techniques toMeasure/Guess Emissivities for PracticalWork 44
1.4.6 Blackbody Radiators: Emissivity Standards for Calibration Purposes 45
1.5 Optical Material Properties in IR 49
1.5.1 Attenuation of IR Radiation while Passing throughMatter 50
1.5.2 Transmission of Radiation through the Atmosphere 51
1.5.3 Transmission of Radiation through Slablike SolidMaterials 54
1.5.3.1 Nonabsorbing Slabs 54
1.5.3.2 Absorbing Slabs 55
1.5.4 Examples of Transmission Spectra of Optical Materials for IR Thermal Imaging 56
1.5.4.1 Gray Materials in Used IR Spectral Ranges 56
1.5.4.2 Some Selective Absorbers 61
1.6 Thin Film Coatings: IR Components with Tailored Optical Properties 62
1.6.1 Interference ofWaves 63
1.6.2 Interference and Optical Thin Films 64
1.6.3 Examples of AR Coatings 65
1.6.4 Other Optical Components 66
1.7 Some Notes on the History of Infrared Science and Technology 69
1.7.1 Infrared Science 69
1.7.1.1 Discovery of Heat Rays and Atmospheric Absorption 69
1.7.1.2 Blackbodies and Blackbody Radiation 72
1.7.1.3 Radiation Laws 73
1.7.2 Development of Infrared Technology 76
1.7.2.1 Prerequisites for IR Imaging 77
1.7.2.2 Quantitative Measurements 84
1.7.2.3 Applications and Imaging Techniques 88
References 97
2 Basic Properties of IR Imaging Systems 107
2.1 Introduction 107
2.2 Detectors and Detector Systems 107
2.2.1 Parameters That Characterize Detector Performance 108
2.2.2 Noise Equivalent Temperature Difference 110
2.2.3 Thermal Detectors 111
2.2.3.1 Temperature Change of Detector 111
2.2.3.2 Temperature-Dependent Resistance of Bolometer 112
2.2.3.3 NEP and D* forMicrobolometer 113
2.2.4 Photon Detectors 117
2.2.4.1 Principle of Operation and Responsivity 117
2.2.4.2 D* for Signal-Noise-Limited Detection 119
2.2.4.3 D* for Background Noise Limited Detection 120
2.2.4.4 Necessity to Cool Photon Detectors 123
2.2.5 Types of Photon Detectors 125
2.2.5.1 Photoconductors 125
2.2.5.2 Photodiodes 126
2.2.5.3 Schottky Barrier Detectors 128
2.2.5.4 Quantum Well IR Photodetectors 128
2.2.5.5 Recent Developments in IR Detector Technology 132
2.3 Basic Measurement Process in IR Imaging 142
2.3.1 Radiometric Chain 142
2.3.2 Wavebands for Thermal Imaging 146
2.3.3 Selecting the AppropriateWaveband for Thermal Imaging 147
2.3.3.1 Total Detected Amount of Radiation 148
2.3.3.2 Temperature Contrast–Radiation Changes upon Temperature Changes 151
2.3.3.3 Influence of Background Reflections 155
2.3.3.4 Influence of Emissivity and Emissivity Uncertainties 158
2.3.3.5 Potential use of Bolometers in MWor SWband 168
2.4 Complete Camera Systems 173
2.4.1 Camera Design – Image Formation 173
2.4.1.1 Scanning Systems 174
2.4.1.2 Staring Systems–Focal-Plane Arrays 176
2.4.1.3 Nonuniformity Correction 180
2.4.1.4 Bad Pixel Correction 186
2.4.2 Photon Detector versus Bolometer Cameras 186
2.4.3 Detector Temperature Stabilization and Detector Cooling 188
2.4.4 Optics and Filters 191
2.4.4.1 Spectral Response 191
2.4.4.2 Chromatic Aberrations 191
2.4.4.3 Field of View 192
2.4.4.4 Extender Rings 195
2.4.4.5 Narcissus Effect 196
2.4.4.6 Spectral Filters 199
2.4.5 Calibration 200
2.4.6 Camera Operation 204
2.4.6.1 Switch-On Behavior of Cameras 205
2.4.6.2 Thermal Shock Behavior 206
2.4.7 Camera Software – Software Tools 208
2.5 Camera Performance Characterization 209
2.5.1 Temperature Accuracy 209
2.5.2 Temperature Resolution – Noise Equivalent Temperature Difference (NETD) 210
2.5.3 Spatial Resolution – IFOV and Slit Response Function 213
2.5.4 Image Quality: MTF, MRTD, and MDTD 216
2.5.5 Time Resolution – Frame Rate and Integration Time 221
References 226
3 AdvancedMethods in IR Imaging 229
3.1 Introduction 229
3.2 Spectrally Resolved Infrared Thermal Imaging 229
3.2.1 Using Filters 230
3.2.1.1 Glass Filters 231
3.2.1.2 Plastic Filters 233
3.2.1.3 Influence of Filters on Object Signal and NETD 234
3.2.2 Two-Color or Ratio Thermography 236
3.2.2.1 Neglecting Background Reflections 237
3.2.2.2 Approximations of Planck’s Radiation Law 240
3.2.2.3 Tobj Error for True Gray Bodies withinWien Approximation 242
3.2.2.4 Additional Tobj Errors Owing to Nongray Objects 246
3.2.2.5 Ratio Versus Single-Band-Radiation Thermometry 247
3.2.2.6 Exemplary Application of Two-Color Thermography 248
3.2.2.7 Extension of Ratio Method and Applications 254
3.2.3 Multi- and Hyperspectral Infrared Imaging 256
3.2.3.1 Principal Idea 256
3.2.3.2 Basics of FTIR Spectrometry 258
3.2.3.3 Advantages of FTIR Spectrometers 262
3.2.3.4 Example of a Hyperspectral Imaging Instrument 263
3.3 Superframing 265
3.3.1 Method 266
3.3.2 Example of High-Speed Imaging and Selected Integration Times 268
3.3.3 Cameras with Fixed Integration Time 270
3.4 Polarization in Infrared Thermal Imaging 271
3.4.1 Polarization and Thermal Reflections 272
3.4.1.1 Transition from Directed to Diffuse Reflections from Surfaces 272
3.4.1.2 Reflectivities for SelectedMaterials in the Thermal Infrared Range 276
3.4.1.3 Measuring Reflectivity Spectra: Laboratory Experiments 278
3.4.1.4 Identification and Suppression of Thermal Reflections: Practical Examples 281
3.4.2 Polarization-Sensitive Thermal Imaging 284
3.5 Processing of IR Images 285
3.5.1 Basic Methods of Image Processing 287
3.5.1.1 Image Fusion 287
3.5.1.2 Image Building 289
3.5.1.3 Image Subtraction 290
3.5.1.4 Consecutive Image Subtraction: Time Derivatives 293
3.5.1.5 Consecutive Image Subtraction: High-Sensitivity Mode 296
3.5.1.6 Image Derivative in Spatial Domain 296
3.5.1.7 Infrared Image Contrast and Digital Detail Enhancement 300
3.5.2 Advanced Methods of Image Processing 309
3.5.2.1 Preprocessing 311
3.5.2.2 Geometrical Transformations 313
3.5.2.3 Segmentation 314
3.5.2.4 Feature Extraction and Reduction 316
3.5.2.5 Pattern Recognition 319
3.5.2.6 Deblurring of Infrared Images 321
3.6 Active Thermal Imaging 327
3.6.1 Transient Heat Transfer – ThermalWave Description 330
3.6.2 Pulse Thermography 333
3.6.3 Lock-in Thermography 337
3.6.3.1 Nondestructive Testing of Metals and Composite Structures 340
3.6.3.2 Solar Cell Inspection 343
3.6.4 Pulsed Phase Thermography 345
References 346
4 Some Basic Concepts in Heat Transfer 351
4.1 Introduction 351
4.2 The Basic Heat TransferModes: Conduction, Convection, and Radiation 352
4.2.1 Conduction 352
4.2.2 Convection 355
4.2.3 Radiation 356
4.2.4 Convection Including Latent Heats 357
4.3 Selected Examples of Heat Transfer Problems 359
4.3.1 Overview 359
4.3.2 Conduction within Solids: The Biot Number 361
4.3.3 Steady-State Heat Transfer through One-DimensionalWalls and U-Value 364
4.3.4 Heat Transfer ThroughWindows 369
4.3.5 Steady-State Heat Transfer in Two- and Three-Dimensional Problems: Thermal Bridges 370
4.3.6 Dew Point Temperatures 372
4.4 Transient Effects: Heating and Cooling of Objects 373
4.4.1 Heat Capacity and Thermal Diffusivity 374
4.4.2 Short Survey of Quantitative Treatments of Time-Dependent Problems 375
4.4.3 Demonstration of Transient Heat Diffusion 377
4.4.4 Typical Time Constants for Transient Thermal Phenomena 377
4.4.4.1 Cooling Cube Experiment 379
4.4.4.2 Theoretical Modeling of Cooling of Solid Cubes 379
4.4.4.3 Time Constants for Different Objects 382
4.5 Some Thoughts on the Validity of Newton’s Law 383
4.5.1 Theoretical Cooling Curves 383
4.5.2 Relative Contributions of Radiation and Convection 385
4.5.3 Experiments: Heating and Cooling of Light Bulbs 389
References 392
5 Basic Applications for Teaching: Direct Visualization of Physics Phenomena 393
5.1 Introduction 393
5.2 Mechanics: Transformation of Mechanical Energy into Heat 394
5.2.1 Sliding Friction andWeight 394
5.2.2 Sliding Friction during Braking of Bicycles and Motorcycles 395
5.2.3 Sliding Friction: the Finger or Hammer Pencil 398
5.2.4 Inelastic Collisions: Tennis 398
5.2.5 Inelastic Collisions: The Human Balance 401
5.2.6 Temperature Rise of Floor and Feet whileWalking 402
5.2.7 Temperature Rise of Tires during Normal Driving of a Vehicle 403
5.2.8 Generating Heat by Periodic Stretching of Rubber 404
5.3 Thermal Physics Phenomena 406
5.3.1 Conventional Hot-Water-Filled Heaters 407
5.3.2 Thermal Conductivities 407
5.3.3 Conduction of Heat in Stack of Paper 410
5.3.4 Convection in Liquids 410
5.3.5 Convection Effects Due to Gases 414
5.3.6 Evaporative Cooling 414
5.3.7 Adiabatic Heating and Cooling 417
5.3.8 Heating of Cheese Cubes 418
5.3.9 Cooling of Bottles and Cans 422
5.4 Electromagnetism 424
5.4.1 Energy and Power in Simple Electric Circuits 424
5.4.2 Eddy Currents 426
5.4.3 Thermoelectric Effects 427
5.4.4 Experiments with Microwave Ovens 429
5.4.4.1 Setup 429
5.4.4.2 Visualization of Horizontal Modes 430
5.4.4.3 Visualization of Vertical Modes 431
5.4.4.4 Aluminum Foil in Microwave Ovens 431
5.5 Optics and Radiation Physics 432
5.5.1 Transmission ofWindow Glass, NaCl, and SiliconWafers 433
5.5.2 From Specular to Diffuse Reflection 435
5.5.3 Some Light Sources 437
5.5.4 Blackbody Cavities 437
5.5.5 Emissivities and Leslie Cube 439
Contents XI
5.5.6 From Absorption to Emission of Cavity Radiation 441
5.5.7 Selective Absorption and Emission of Gases 443
References 444
6 Shortwave Infrared Thermal Imaging 447
6.1 Introduction 447
6.2 The Why and How of SWInfrared Imaging 447
6.3 Some Applications of SWInfrared Imaging 450
6.3.1 Water OpticalMaterial Properties 452
6.3.2 Cameras Used in the Experiments 452
6.3.3 Selected Examples of SWImaging 454
6.3.3.1 High-Temperature Measurements 454
6.3.3.2 Vegetation Studies 456
6.3.3.3 Sky-to-Cloud Contrast Enhancement 458
6.3.3.4 Sorting Plastics and Detecting Liquid Levels in Plastic Containers 460
6.3.3.5 Looking Beneath the Surface 461
6.3.3.6 Undamaged Fresh Fruit/Vegetable Test 466
6.3.3.7 Material Properties of Liquids 467
6.3.3.8 Moisture onWalls 470
6.3.3.9 Other Applications of SW Imaging 470
6.4 Survey of Commercial Systems 472
References 472
7 IR Imaging of Buildings and Infrastructure 477
7.1 Introduction 477
7.1.1 Publicity of IR Images of Buildings 478
7.1.2 Just Colorful Images? 479
7.1.2.1 Level and Span 480
7.1.2.2 Choice of Color Palette 480
7.1.2.3 More on Palette, Level, and Span 480
7.1.3 General Problems Associated with Interpretation of IR Images 485
7.1.4 Energy Standard Regulations for Buildings 488
7.2 Some Standard Examples for Building Thermography 490
7.2.1 Half-Timbered Houses behind Plaster 490
7.2.2 Other Examples with OutsideWalls 493
7.2.3 Determining whether a Defect Is Energetically Relevant 494
7.2.4 The Role of Inside Thermal Insulation 497
7.2.5 Floor Heating Systems 498
7.3 Geometrical Thermal Bridges versus Structural Problems 500
7.3.1 Geometrical Thermal Bridges 500
7.3.2 Structural Defects 504
7.4 External Influences 507
7.4.1 Wind 507
7.4.2 Effect of Moisture in Thermal Images 509
7.4.3 Solar Load and Shadows 513
7.4.3.1 Modeling Transient Effects Due to Solar Load 513
7.4.3.2 Experimental Time Constants 516
7.4.3.3 Shadows 518
7.4.3.4 Solar Load of Structures withinWalls 519
7.4.3.5 Direct Solar Reflections 520
7.4.4 General View Factor Effects in Building Thermography 525
7.4.5 Night Sky Radiant Cooling and the View Factor 528
7.4.5.1 Cars Parked Outside or Below a Carport 529
7.4.5.2 Walls of Houses Facing a Clear Sky 531
7.4.5.3 View Factor Effects: Partial Shielding ofWalls by Carport 531
7.4.5.4 View Factor Effects: The Influence of Neighboring Buildings and Roof Overhang 533
7.5 Windows 534
7.5.1 General Features 534
7.5.2 Optically Induced Thermal Effects 539
7.6 Thermography and Blower-Door Tests 541
7.6.1 Close-Up Studies 543
7.6.2 Overview Studies 547
7.7 Quantitative IR Imaging: Total Heat Transfer through Building Envelope 549
7.8 New Developments and Conclusions 552
References 556
8 Industrial Application: Detection of Gases 561
8.1 Introduction 561
8.2 Spectra of Molecular Gases 561
8.3 Influences of Gases on IR Imaging: Absorption, Scattering, and Emission of Radiation 567
8.3.1 Introduction 567
8.3.2 Interaction of Gases with IR Radiation 567
8.3.3 Influence of Gases on IR Signals from Objects 569
8.4 Absorption by Cold Gases: Quantitative Aspects 572
8.4.1 Attenuation of Radiation by a Cold Gas 572
8.4.2 From Transmission Spectra to Absorption Constants 574
8.4.3 Transmission Spectra for Arbitrary Gas Conditions and IR Camera Signal Changes 574
8.4.4 Calibration Curves for Gas Detection 577
8.4.5 Problem: the Enormous Variety ofMeasurement Conditions 578
8.5 Thermal Emission from Hot Gases 580
8.6 New Developments 582
8.7 Practical Examples: Gas Detection with Commercial IR Cameras 588
8.7.1 Organic Compounds 588
8.7.2 Some Inorganic Compounds 591
8.7.3 CO2: Gas of the Century 594
8.7.3.1 Comparison of Broadband and Narrowband Detection 596
8.7.3.2 Detecting Volume Concentration of CO2 in Exhaled Air 597
8.7.3.3 Absorption, Scattering, and Thermal Emission of IR Radiation 597
8.7.3.4 Quantitative Result: Detecting Minute Amounts of CO2 in Air 599
8.7.3.5 Quantitative Result: Detection ofWell-Defined CO2 Gas Flows from a Tube 599
8.A Appendix: Survey of Transmission Spectra of Various Gases 602
8.A.1 Inorganic Compounds 1 604
8.A.2 Inorganic Compounds 2 605
8.A.3 Simple Hydrocarbons 1 606
8.A.4 Simple Hydrocarbons 2 607
8.A.5 Simple Multiple Bond Compounds and Some Alcohols 608
8.A.6 Some Ketones/Ethers 609
8.A.7 Some Benzene Compounds 610
8.A.8 Some HydrocarbonsWith Halogens 611
References 612
9 Microsystems 615
9.1 Introduction 615
9.2 Special Requirements for Thermal Imaging 616
9.2.1 Mechanical Stability of Setup 616
9.2.2 Microscope Objectives, Close-up Lenses, Extender Rings 616
9.2.3 High-Speed Recording 618
9.2.4 Temperature Measurement 618
9.3 Microfluidic Systems 619
9.3.1 Microreactors 619
9.3.1.1 Stainless Steel Falling Film Microreactor 619
9.3.1.2 Glass Microreactor 623
9.3.1.3 Silicon Microreactor 625
9.3.2 Micro Heat Exchangers 626
9.4 Microsensors 628
9.4.1 Thermal IR Sensors 628
9.4.1.1 IR Thermopile Sensors 629
9.4.1.2 IR Bolometer Sensors 632
9.4.2 Semiconductor Gas Sensors 635
9.5 Microsystems with Electric to Thermal Energy Conversion 637
9.5.1 Miniaturized IR Emitters 637
9.5.2 Micro Peltier Elements 639
9.5.3 Cryogenic Actuators 640
References 642
10 Selected Topics in Industry 645
10.1 Introduction 645
10.2 Miscellaneous Industrial Applications 645
10.2.1 Predictive Maintenance and Quality Control 645
10.2.2 Pipes and Valves in a Power Plant 647
10.2.3 Levels of Liquids in Tanks in Petrochemical Industry 648
10.2.4 Polymer Molding 651
10.2.5 Rack-Storage Fire Testing 652
10.3 Low-Voltage Electrical Applications 653
10.3.1 Early Microelectronic Boards 654
10.3.2 Macroscopic Electric Boards 655
10.3.3 ModernMicroelectronic Boards 656
10.4 High-Voltage Electrical Applications 656
10.4.1 Substation Transformers 657
10.4.2 Overheated High-Voltage Line 659
10.4.3 Electric Fan Defects 660
10.4.4 Oil Levels in High-Voltage Bushings 660
10.5 Metal Industry and High Temperatures 662
10.5.1 Direct Imaging of HotMetal Molds 662
10.5.2 Manufacturing Hot SolidMetal Strips: Thermal Reflections 663
10.5.3 Determination of Metal Temperatures if Emissivity Is Known 665
10.5.4 Determining Metal Temperatures for Unknown Emissivity: Gold Cup Method 666
10.5.5 Determining Metal Temperatures for Unknown Emissivity:Wedge and Black Emitter Method 667
10.5.6 Other Applications of IR Imaging in Metal Industry or at High Temperatures 669
10.6 Automobile Industry 670
10.6.1 Quality Control of Heating Systems 671
10.6.2 Active and Passive IR Night Vision Systems 672
10.6.3 IR Imaging of Race Cars 675
10.6.4 Motorcycles 676
10.7 Airplane and Spacecraft Industry 676
10.7.1 Imaging of Aircraft 676
10.7.2 Imaging of Spacecraft 678
10.8 Plastic Foils 683
10.8.1 Spectra: Selective Emitters 683
10.8.2 Images: Looking through Plastics 685
10.9 Surveillance and Security: Range of IR Cameras 687
10.9.1 Applications in Surveillance 687
10.9.2 Range of IR Cameras 688
10.10 Line Scanning Thermometry ofMoving Objects 694
10.11 Remote Sensing Using IR Imaging 695
10.11.1 Survey ofMethods 695
10.11.2 Some IR Imaging Applications Using Drones 699
References 702
11 Selected Applications in Other Fields 709
11.1 Medical Applications 709
11.1.1 Introduction 709
11.1.2 Diagnosis andMonitoring of Pain 712
11.1.3 Acupuncture 716
11.1.4 Breast Thermography and Detection of Breast Cancer 718
11.1.5 Other Medical Applications 719
11.1.5.1 Raynaud’s Phenomenon 719
11.1.5.2 Pressure Ulcers 720
11.2 Animals and Veterinary Applications 721
11.2.1 Pets 722
11.2.2 Zoo Animals 723
11.2.3 Equine Thermography 725
11.2.4 Wildlife 726
11.3 Sports 729
11.3.1 High-Speed Recording of Tennis Serve 729
11.3.2 Squash and Volleyball 732
11.3.3 Other Applications in Sports 734
11.4 Arts: Music, Contemporary Dancing, and Paintings 735
11.4.1 Musical Instruments 735
11.4.2 Contemporary Dance 737
11.4.3 Paintings 740
11.5 Nature 742
11.5.1 Sky and Clouds 742
11.5.2 Wildfires 746
11.5.3 Sun and Moon 749
11.5.4 InfraredMirages 752
11.5.5 Geothermal Phenomena 754
11.5.5.1 Geysers and Hot Springs 754
11.5.5.2 IR Thermal Imaging in Volcanology 756
References 760
Index 765
