Thermal Infrared Sensors - Theory, Optimisation And Practice

The problems involved in designing optimal infrared (IR) measuring systems under given conditions are commensurately complex. The optical set-up and radiation conditions, the interaction between sensor and irradiation and the sensor itself, determine the operation of the sensor system. Simple calculations for solving these problems without any understanding of the causal relationships are not possible.

Thermal Infrared Sensors offers a concise explanation of the basic physical and photometric fundamentals needed for the consideration of these interactions. It depicts the basics of thermal IR sensor systems and explains the manifold causal relationships between the most important effects and influences, describing the relationships between sensor parameters such as thermal and special resolution, and application conditions.

This book covers:

• various types of thermal sensors, like thermoelectric sensor, pyroelectric sensors, microbolometers, micro-Golay cells and bimorphous sensors;
• basic applications for thermal sensors;
• noise - a limiting factor for thermal resolution and detectivity - including an outline of the mathematics and noise sources in thermal infrared sensors;
• the properties of IR sensor systems in conjunction with the measurement environment and application conditions;
• 60 examples showing calculations of real problems with real numbers, as they occur in many practical applications.

This is an essential reference for practicing design and optical engineers and users of infrared sensors and infrared cameras. With this book they will be able to transform the demonstrated solutions to their own problems, find ways to match their commercial IR sensors and cameras to their measurement conditions, and to tailor and optimise sensors and set-ups to particular IR measurement problems. The basic knowledge outlined in this book will give advanced undergraduate and graduate students a thorough grounding in this technology.

Preface.

List of Examples.

List of Symbols.

Indices.

Abbreviations.

1 Introduction.

1.1 Infrared Radiation.

1.1.1 Technical Applications.

1.1.2 Classification of Infrared Radiation.

1.2 Historical Development.

1.3 Advantages of Infrared Measuring Technology.

1.4 Comparison of Thermal and Photonic Infrared Sensors.

1.5 Temperature and Spatial Resolution of Infrared Sensors.

1.6 Single-Element Sensors Versus Array Sensors.

References.

2 Radiometric Basics.

2.1 Effect of Electromagnetic Radiation on Solid-State Bodies.

2.1.1 Propagation of Radiation.

2.1.2 Propagation in Lossy Media.

2.1.3 Fields at Interfaces.

2.1.4 Transmission Through Thin Dielectric Layers.

2.2 Radiation Variables.-

2.2.1 Radiation-Field-Related Variables.

2.2.2 Emitter-Side Variables.

2.2.3 Receiver-Related Variables.

2.2.4 Spectral Variables.

2.2.5 Absorption, Reflection and Transmission.

2.2.6 Emissivity.

2.3 Radiation Laws.

References.

3 Photometric Basics.

3.1 Solid Angle.

3.1.1 Definition.

3.1.2 Solid Angle Calculations.

3.2 Basic Law of Photometry.

3.2.1 Definition.

3.2.2 Calculation Methods and Examples.

3.2.3 Numerical Solution of the Projected Solid Angle.

References.

4 Noise.

4.1 Mathematical Basics.

4.1.1 Introduction.

4.1.2 Time Functions.

4.1.3 Probability Functions.

4.1.4 Correlation Functions.

4.1.5 Spectral Functions.

4.1.6 Noise Analysis of Electronic Circuits.

4.2 Noise Source in Thermal Infrared Sensors.

4.2.1 Thermal Noise and tan δ.

4.2.2 Current Noise.

4.2.3 1/f Noise.

4.2.4 Radiation Noise.

4.2.5 Temperature Fluctuation Noise.

References.

5 Sensor Parameters.

5.1 Responsivity.

5.1.1 Introduction.

5.1.2 Black Responsivity.

5.1.3 Spectral Responsivity.

5.1.4 Signal Transfer Function.

5.1.5 Uniformity.

5.2 Noise-Equivalent Power NEP.

5.3 Detectivity.

5.4 Noise-Equivalent Temperature Difference.

5.5 Optical Parameters.

5.6 Modulation Transfer Function.

5.6.1 Definition.

5.6.2 Contrast.

5.6.3 Modulation Transfer Function of a Sensor.

5.6.4 Measuring the Modulation Transfer Function.

References.

6 Thermal Infrared Sensors.

6.1 Operating Principles.

6.2 Thermal Models.

6.2.1 Simple Thermal Model.

6.2.2 Thermal Layer Model.

6.3 Network Models for Thermal Sensors.

6.4 Thermoelectric Radiation Sensors.

6.4.1 Principle.

6.4.2 Thermal Resolution.

6.4.3 Design of Thermoelectric Sensors.

6.5 Pyroelectric Sensors.

6.5.1 Principle.

6.5.2 Thermal Resolution.

6.5.3 Design of Pyroelectric Sensors.

6.6 Microbolometers.

6.6.1 Principle.

6.6.2 Thermal Resolution.

6.6.3 Design of a Microbolometer Array.

6.6.4 Read-Out Electronics of Microbolometers.

6.7 Other Thermal Infrared Sensors.

6.7.1 Bimorphous Infrared Sensors.

6.7.2 Micro-GOLAY Cells.

6.8 Comparison of Thermal Sensors.

References.

7 Applications of Thermal Infrared Sensors.

7.1 General Considerations.

7.2 Pyrometry.

7.2.1 Design.

7.2.2 Emissivity of Real Emitters.

7.3 Thermal Imaging Cameras.

7.3.1 Design.

7.3.2 Calibration of Thermal Imaging Cameras.

7.4 Passive Infrared Motion Detector.

7.4.1 Design.

7.4.2 Infrared Optics.

7.4.3 Signal Processing.

7.5 Infrared Spectrometry.

7.5.1 Radiation Absorption of Gases.

7.5.2 Design of an Infrared Spectrometer.

7.6 Gas Analysis.

References.

Appendix A: Constants.

Appendix B: PLANCK s Law of Radiation and Derived Laws.

Appendix C: Calculation of the Solid Angle of a Rectangular Area.

Further Reading and Sources.

Index.