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Spie Press Book

Infrared Optics and Zoom Lenses, Second Edition
Author(s): Allen Mann
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Book Description

Ten years after the publication of Infrared Optics and Zoom Lenses, this text is still the only current publication devoted exclusively to infrared zoom lenses. This updated second edition includes 18 new refractive and reflective infrared zoom systems, bringing the total number of infrared zoom optical systems to 41 systems. Other additions include a section on focal plane arrays and a new closing chapter specifically devoted to applications of infrared zoom lenses. Coverage of wavelength region has been expanded to include the near infrared. Additional topics include an examination of the importance of principal planes, methods for athermalization by means of computer glass substitution, and global optimization techniques for zoom lens design.

Book Details

Date Published: 27 March 2009
Pages: 182
ISBN: 9780819476678
Volume: TT83
Errata

Table of Contents
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Preface
1. System Considerations
1.1 Radiometry
1.1.1 Blackbody radiation
1.1.2 Planck's equation
1.1.3 Stefan-Boltzmann law
1.1.4 Wien displacement law
1.2 Atmospheric Transmission
1.2.1 Scattering
1.2.2 Absorption
1.2.3 Infrared windows
1.2.4 Computer calculation
1.3 Lens Transmission
1.3.1 Transmittance
1.3.2 Reflectance
1.4 Coatings
1.4.1 Single-layer coatings
1.4.2 Multilayer coatings
1.5 Infrared Detectors
1.5.1 Basic relations
1.5.2 Types
1.5.3 Arrays
1.5.4 Matching the detector with the optics
1.6 References
2. Optics Fundamentals
2.1 Lens Equation
2.2 Stops and Pupils
2.3 Optical Formulas
2.4 Optical Performance Criteria
2.5 Telescopes
2.6 Primary Aberrations
2.6.1 Definition of the Seidel aberrations
2.6.2 Variation of primary aberrations with aperture and field height
2.6.3 Stop shift equations
2.7 Achromatism
2.7.1 Primary achromatism
2.7.2 Secondary spectrum
2.8 Principal Planes
2.9 Problems
2.10 References
3. Unique Features of the Infrared Region
3.1 Optical Materials
3.1.1 Materials for the infrared
3.1.2 Calculation of index of refraction
3.2 Thermal Compensation
3.2.1 Focus shift with temperature
3.2.2 Athermalization
3.2.3 Athermalization methods
3.3 Cold Stop and Cold Shield
3.4 Narcissus
3.4.1 Types of retroreflections
3.4.2 Reduction techniques
3.5 Glass Substitution
3.6 References
4. Optical Design Techniques
4.1 Optical Design Starting Point
4.2 Scaling
4.3 Optical Materials Selection
4.4 Techniques for Compactness
4.5 Symmetry Principle
4.6 Bending
4.7 Aplanatic Condition
4.8 Adding an Element
4.9 Field Lens Utilization
4.10 Conics and Aspheres
4.11 Diffractive Surfaces
4.12 Aperture Stop Location
4.13 Computer Optimization
4.14 Global Search
4.15 Tolerances
4.16 References
5. Zoom Lenses
5.1 Types of Zoom Lenses
5.1.1 Optically compensated zoom lens
5.1.2 Mechanically compensated zoom lens
5.2 Infrared Zoom Lens Specifications
5.2.1 Spectral region
5.2.2 Optical system performance
5.2.3 Aperture
5.2.4 Effective focal length
5.2.5 Magnification range
5.2.6 Size constraints
5.2.7 Operating environment
5.2.8 Distortion
5.2.9 Transmission
5.2.10 Narcissus
5.2.11 Vignetting
5.3 Extenders
5.4 References
6. Refractive Infrared Zoom Lenses
6.1 Target Simulators
6.1.1 CI Systems
6.1.2 Hughes Aircraft Company
6.1.3 Lockheed Martin
6.1.4 Optics 1
6.2 Scanning Systems
6.2.1 Barr & Stroud
6.2.2 Pilkington P.E.
6.2.3 Optics 1
6.2.4 Precision-Optical Engineering
6.2.5 Zhejiang University, Department of Optical Engineering
6.2.6 Electrooptical Industries, Ltd.
6.2.7 Scotoptix
6.2.7.1 Boresighted zoom lens
6.2.7.2 Athermalized zoom lens
6.2.7.3 Optically compensated zoom lens
6.2.8 Optimum Optical Systems
6.2.9 Royal Institute of Technology
6.2.10 Fuji Photo Optical Company
6.2.11 Carl Zeiss
6.3 Charge-Coupled Device Imaging Systems
6.3.1 Angenieux 84
6.3.2 University of Alabama, Huntsville
6.3.3 National First University of Science and Technology
6.3.4 Industrial Technology Research Institute
6.4 Laser Beam Expanders
6.4.1 Carl Zeiss
6.4.2 University of Twente
6.5 Diffractive Optics
6.5.1 Optics 1
6.5.2 Optical E.T.C., Inc. and Teledyne Brown
6.5.3 Wescam
6.5.4 Texas Instruments
6.5.5 Raytheon
6.5.6 Raytheon
6.6 Focal Plane Arrays
6.6.1 Agency for Defence Development
6.6.2 Royal Institute of Technology
6.6.3 Royal Institute of Technology
6.7 References
7. Reflective Infrared Zoom Systems
7.1 Obscured Systems
7.1.1 Korea Advanced Institute of Science and Technology
7.1.2 Center for Applied Optics, University of Alabama, Huntsville
7.2 Unobscured Systems
7.2.1 Hughes Aircraft Company
7.2.2 Optical E.T.C., Inc.
7.2.3 Beijing Institute of Technology
7.2.4 Contraves Brashear
7.3 Special Systems
7.3.1 Lockheed Martin
7.3.2 Industrial Research, Ltd.
7.3.3 Optical Research Associates
7.4 References
8. Future Trends
8.1 Athermalization
8.2 Diffractive Optical Elements
8.3 Conics and Aspherics
8.4 Materials
8.5 Detector Technology
8.6 Simulators
8.7 Mirror Systems
8.8 Wavelength Region
8.9 Optomechanical Considerations
8.10 Computer Optimization
8.11 References
9. Summary of Applications
9.1 Scene Projection and Simulation
9.2 Wide and Narrow Field of View Scanning Telescopes for Target Search and Recognition
9.3 WFOV and NFOV FPA or CCD Surveillance, Tracking, and Target Recognition
9.4 Battlefield Detection of Enemy Soldiers and Armaments
9.5 Search and Rescue Operations
9.6 Mineral Resource Surveys and Forest Fire Detection
9.7 Laser Scanning Systems
9.8 Cutting Sheet Metal with High-Power Lasers
9.9 Observation of Solar Regions
9.10 Camera Cell Phones
Appendix A. Miscellaneous Patents
Appendix B. Computer Analysis of Selected Patents
Appendix C. Answers to Problems from Chapter 2
Index

Preface

This tutorial is an outgrowth of my SPIE short course entitled "Infrared Optics and Zoom Lenses." The title was selected to reflect the scope of the subject matter, and this has been carried over to the tutorial. The first three chapters present an introduction to the principles of optics and the unique aspects of the infrared region of the wavelength spectrum. This foundation makes it possible for those readers who are not optical engineers to acquire the background information needed for a treatise on infrared zoom lenses.

Chapter 1 presents overall system considerations involved in establishing the requirements for an application that includes an optical system as one of its elements. Chapter 2 sets forth the basic fundamentals of optics involved in the design and analysis of optical systems. Chapter 3 presents the optics features that are unique to the infrared region of the spectrum. Chapter 4 discusses some of the optical design techniques that may be utilized in the optical design of infrared systems. These four chapters could serve as an introduction to any treatise on infrared optical systems. Further discussion of these topics may be found in the tutorial text on this subject by Max J. Riedl.1

Chapters 5 through 8 present the subject matter that is unique to the subject of zoom lenses in the infrared. Chapter 5 sets forth the basic types of zoom lenses and the establishing of specifications to meet the requirements of a particular application. Chapters 6 and 7 present numerous examples of refractive and reflective infrared zoom systems; the optical design techniques from Chapter 4 are employed in designing these representative infrared (IR) zoom lenses to illustrate the utilization of these techniques. Companies identified in Chapters 6 and 7 are the names in existence at the time the reference papers were published; some of them have since merged with other companies and lost their separate identity. Chapter 8 presents a brief discussion of future trends in this subject area. Chapter 9 presents a summary of infrared zoom lens applications.

Appendix A contains three landmark IR zoom lens patents in their entirety as published. This appendix is included not only for the insights contained therein, but also to provide lens prescription data to serve as potential starting points for future design activity. Appendix B presents computer analysis that I have performed on these patents and on one additional patent described in Sec. 7.2.1. A definition of the analysis categories is to be found in Chapter 2. Appendix C gives the answers to self-test problems presented in Sec. 2.9.

The infrared zoom lens literature consists primarily of patents and of papers presented at conferences or published in journals and proceedings. In 1993 SPIE published in its Milestone Series of Selected Reprints a volume on zoom lenses which included a number of infrared papers and patents.2 To my knowledge, this tutorial is the first publication to be devoted exclusively to IR zoom lenses. It should serve as an introduction to the subject for the uninitiated and as an aid to the engineer who has an infrared zoom lens application to pursue. It is not intended to be a step-by-step instruction manual for this complex optical design activity.

Additions to Infrared Optics and Zoom Lenses are included in the second edition of this tutorial. The additions are based on an expanded short course which I presented to BAE Systems in Lexington, Massachusetts, on June 20, 2008. There are substantive additions to the topics in the table of contents. They are discussed below. Also, 19 new refractive and reflective systems have been added to the 23 zoom systems in the first edition, bringing the total to 42 optical systems. The 19 new systems were published in the reference literature since publication of the first edition, in the time interval from the year 2000 to 2007. These additional systems are in part the result of adding a new category—focal plane arrays—to the chapter on refractive infrared zoom lenses. In part these additions are a result of including dual field-of-view infrared optical systems in this tutorial. The 19 new zoom systems are intended to bring the technology and the list of refractive and reflective zoom infrared systems up to date. There are 24 additional references.

One of the themes that will be presented is the gradual shift in recent years from the 8- to 12-micrometer (µm) region to the 3- to 5-µm region of the wavelength spectrum. This shift is discussed in Secs. 2.8, 3.1, 3.2, 6.5, and 6.6.

The rationale for the substantive additions is presented below:

2.3 Principal planes: The location of the principal planes is important in order to calculate accurately the separation between lens elements when going from a thin-lens solution to a thick-lens solution. The location also affects the overall length of the zoom system.

2.9 Self-test problems: A problem set is included in order to ensure a clear understanding of optics fundamentals before discussing the infrared spectrum and infrared zoom systems.

3.2.4 Glass substitution: Glass substitution is a powerful technique for performing computer optimization and athermalization simultaneously by passive substitution of infrared optical materials. I have done this glass substitution successfully, and I present a detailed example with a reference to the paper I wrote on this subject.

4.14 Global search: Global search has been demonstrated in recent years to be a viable computer optimization tool. An example is presented of designing zoom lenses by means of global search without designer intervention. The computer program flowchart of the decision-making process is included in this discussion.

5.3 Extenders: Extenders are a practical means of extending the focal length range of zoom lens systems. It is important to understand the optical limitations of extenders.

6.6 Focal plane arrays:The use of focal plane arrays (FPA) to eliminate scanning is an important development in infrared optical systems. Techniques for overcoming the limitations of resolution of FPAs at higher spatial frequencies are discussed in this section.

7.3 Special reflective systems: Due to the increase in the number of reflective infrared zoom systems, it is important to understand techniques for dual-channel detector arrays and for designing compact reflective systems through the use of folding mirrors and the Mangin mirror.

Chapter 9 Summary of applications: It is useful to summarize the scope and variety of infrared zoom lens applications. The discussion includes a reference to each of the zoom systems presented in this tutorial. This overview makes this chapter a fitting conclusion.

Acknowledgement is due to Gayle Lemieux and Zandra Grissom of SPIE for their support of the BAE short course, and to Gwen Weerts of SPIE for her editorial assistance in the publication of this second edition of Infrared Optics and Zoom Lenses.

Allen Mann
January 2009

  1. Riedl, M. J. Optical Design Fundamentals for Infrared Systems, Second Edition, SPIE Press, Bellingham, WA (2001).
  2. Mann, A., Ed., Selected Papers on Zoom Lenses, SPIE Press, Bellingham, WA (1993).

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