Modern Classical Optical System Design

Foreword Preface Acknowledgements Author biography Abbreviations Symbols 1 Imaging 1.1 An introduction to the real world 1.1.1 Real lens systems take in all the light until rays hit a ‘STOP’ 1.1.2 Shoot for the ‘minimum viable product’ (make it ‘perfect’ in steps) 1.1.3 But even ‘perfect’ cannot be perfect: limitations due to physical laws 1.1.4 Realistic product development operates between these two limits 1.1.5 What to do about ambiguous requirements 1.1.6 Your list of ‘things I still need to understand’ will only grow (which is fine) 1.1.7 Everything you really want to do will likely take place only after office hours 1.1.8 Why books are still necessary for your knowledge 1.1.9 You become good at something by doing it over and over for a very long time 1.1.10 How to bug people for help 1.1.11 Truth = the best estimate ± uncertainty 1.1.12 Are you ready for this? 1.2 Optical system design using Ansys Zemax OpticStudio® 1.2.1 Set the aperture 1.2.2 Set the fields 1.2.3 Set the wavelengths (I will tell you how many you need) 1.2.4 Create a paraxial thin-lens equivalent system 1.2.5 Use ‘solves’ 1.2.6 Check the MTF and defocus sensitivity and create defocus invariance 1.2.7 Creating a real lens model of the thin-lens model 1.2.8 Lens MTF, spatial frequency, field curvature, distortion, and relative illumination 1.2.9 Why it is not always about MTF in real life (it depends on your application) 1.2.10 Amazing OpticStudio features you may not know about(which we will use) 1.2.11 Tilted and decentered components and assemblies 1.2.12 Optimizing a lens 1.2.13 Tolerancing analysis for a lens 1.2.14 Create and use a ‘black box file’ 1.2.15 Nonsequential modeling and analysis 1.2.16 Dealing with ‘ray trace noise’ in nonsequential modeling 1.2.17 Deciding between nonsequential and sequential approaches 1.2.18 OpticStudio’s hybrid nonsequential mode (this is a powerful tool) 1.2.19 A wrap-up; get set to use OpticStudio for the rest of this book 1.3 Practical concepts for optical system layout and analysis 1.3.1 First-order: all you really need is 1/f = 1/s + 1/s′ 1.3.2 Example: a microscope tube lens using commercial off-the-shelf lenses 1.3.3 Example: a xenon arc lamp with an elliptical reflector 1.3.4 Notes on designing with commercial off-the-shelf components 1.3.5 If you master the concept of conjugate planes, you can go very far 1.3.6 Example: collimation at an intermediate plane and its application 1.3.7 Example: conjugate planes in modern microscope condensers 1.3.8 Example: a simple modern digital microscope using commercial off-the-shelf lenses 1.3.9 Example: locating and modeling dust artifacts in imaging systems 1.3.10 Conjugate planes in a classical projector 1.3.11 Object and image conjugates at the same location 1.3.12 If you master the concept of pupils, you will understand what detectors ‘see’ 1.3.13 Example: relay lenses (you will often need them) 1.3.14 Example: pupil and scene visibility in a terrestrial telescope 1.3.15 More on pupils: Max Berek’s ‘forgotten’ formula 1.3.16 The optical center of a lens (you have probably never heard of this) 1.3.17 Locating and optimizing the optical center of a lens system 1.3.18 The application of the optical center and pupils to depth sensing 1.3.19 Approximate analogies: eyepieces, tube lenses, and scan lenses 1.3.20 Approximate analogies: condensers as eyepieces in reverse 1.4 Practical lens design and aberration management 1.4.1 In rapid product development, just ‘manage’ the aberrations (we show you how) 1.4.2 Heuristic lens design theory 1.4.3 Why are mobile phone lenses not used as high-aperture laser scan lenses? 1.4.4 Do not be afraid of ‘aplanatism’ (it is just a term for an optimized lens, except…) 1.4.5 The optical sine theorem is not the same as the Abbe sine condition 1.4.6 Analogous imaging systems: aspheric aplanatic singlets and Ritchey–Chrétien mirrors 1.4.7 Heuristic color correction theory 1.4.8 Conrady’s D-d method for achromatizing 1.4.9 Do commercial off-the-shelf achromats satisfy D-d? 1.4.10 Example: achromatizing a monochromatic four-element lens 1.4.11 Example: an apochromatic microscope tube lens design 1.4.12 Example: secondary color in a high-aperture double-Gauss lens 1.5 Preparing drawings for optical fabrication 1.5.1 What an optical design drawing for production looks like 1.5.2 The relation between ISO 10110 specifications and tolerance operands 1.5.3 Modeling the centering process of cemented elements 1.5.4 Alternatives to design drawings: communicating with suppliers References and further reading 2 Illumination 2.1 The illumination problem 2.2 Essential radiometry for illumination problems 2.2.1 What type of source is being modeled in sequential ray tracing? 2.2.2 What is different about sources in nonsequential ray tracing? 2.2.3 Flux, radiance, and étendue in illumination design 2.2.4 From radiance to radiant intensity: modeling sources 2.2.5 The concept of source spread functions and the irradiance of images 2.2.6 If a source radiates and nobody is there to see it, does it shine? 2.2.7 Why is the full width at half maximum often the width of a distribution? 2.2.8 Is the image of a Lambertian source a Lambertian source? 2.2.9 Is chromatic aberration important in illumination? 2.2.10 The radiometry of LEDs and the use of source files in nonsequential ray tracing 2.2.11 There is no free étendue 2.3 The concept of ray density in illumination design 2.4 The concepts of global and local uniformity 2.5 The concepts of étendue division and superposition 2.6 ‘First-order’ illumination design 2.6.1 Illumination using paraxial thin lens models 2.6.2 How to correct the radiance problem (because paraxialthin lenses are fake lenses) 2.6.3 Relative illumination is called critical illumination in illumination design 2.7 How to design for uniform relative illumination 2.8 Relative illumination in direction cosine space 2.9 The phase space viewpoint of relative illumination 2.10 Aplanatism and the relative illumination in the pupil 2.11 Regions of uniformity in collimated light: the searchlight optical layout 2.12 The specification of flashlights and searchlights based on the ANSI FL1 Standard 2.13 Searchlights, critical illumination, and Köhler illumination: a comparison at equal flux and track length 2.14 How to lay out light pipes for uniform illumination 2.15 How to lay out fly’s eye arrays for uniform illumination 2.16 Fly’s eye arrays that have negative-focal-length lenslets 2.17 Uniform oblique illumination 2.18 Point spread function illumination 2.18.1 The coherent case: Gaussian to top-hat laser beam shaping 2.18.2 The incoherent case: LED Lambertian to top-hat beam shaping 2.19 A summary of the approaches used in illumination 2.20 Tips on optimization and tolerancing in nonsequential ray tracing References 3 Optical system product development 3.1 Lights at the ends of tunnels (not light pipes, but a personal story) 3.1.1 Gratification and enlightenment 3.1.2 Challenges in academic life 3.1.3 Transition to the real world and product development 3.1.4 The light at the end 3.1.5 The systems perspective on optical system product development 3.2 An example of a complex optical system: virus detection using real-time quantitative PCR instruments 3.2.1 What is the minimum viable product for such a device? 3.2.2 Why you cannot be ‘just’ a lens designer when designing real-time qPCR instruments 3.3 Statistical principles for optical system product development 3.3.1 The ‘expectation value’ is not the value you should expect to get 3.3.2 The difference between the standard deviation of a function and the standard deviation of random values 3.3.3 Statistical principles related to error analysis, error bars, sensitivity analysis, and optical tolerancing analysis 3.3.4 In optical tolerancing analysis, a merit function is a function of random variables 3.3.5 The std dev of a merit function has a std dev 3.3.6 The different ways in which engineers and statisticians solve problems 3.4 The concept of the signal-to-noise ratio 3.4.1 What exactly is the signal, and what do you mean by ‘noise’? 3.4.2 How does the signal-to-noise ratio scale with the size of a region of interest? 3.4.3 How does the signal-to-noise ratio scale with integration time? 3.4.4 Does camera ‘gain’ increase the signal-to-noise ratio? 3.4.5 What is ‘charge conversion efficiency’? 3.5 The concept of the limit of detection 3.5.1 The noise in the background after subtracting the background 3.5.2 The limit of detection is like an ‘apparent nuisance signal’ 3.5.3 The relationship between the limit of detection and the signal-to-noise ratio 3.6 Remarks concerning the tolerancing of complex optical systems in product development 3.7 Monte Carlo tolerancing as a means to justify an alignment philosophy 3.8 Some nuances of optical systems in product development 3.8.1 When a lens images an intermediate transmissive or reflective surface 3.8.2 The eternal challenge of stray light analysis and control 3.8.3 Ghosts and ‘narcissists’ (I mean narcissus) effects 3.8.4 The spectral ‘blueshifts’ of thin-film filters and beam splitters 3.8.5 Optical density and the transmittance of stacked filters 3.8.6 Optical fibers versus free-space components for illumination 3.8.7 Fundamental limitations to illumination in microscopy 3.8.8 Drift: an enemy of statistics and the reason for calibration 3.8.9 Should manufacturing processes be easy or hard? 3.8.10 Optical design for robustness 3.8.11 Innovation tip—ask the question: ‘How bad is it?’ 3.9 Simple conceptual case studies 3.9.1 A compact optical system for virus detection 3.9.2 The Texas Instruments DLP® chip (DMD) projection optical system 3.10 Wrap up, README, and I wish you all the best! References and further reading Appendix A: Further notes on imaging Appendix B: Further notes on illumination Appendix C: Further notes on optical system product development Appendix D: Notes on some advanced topics