Optical Lens Design - Safety & Regulations

OPTICAL LENS DESIGN

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Types of LensesSLROptical system


SLRSingle lens reflexNormal, Wide angle, tele-photo, zoom


OPTICAL SYSTEMCombination of lens elementsMirrorsPrismsRotating polygon scanners,FiltersDiffraction gratings


HOW TO DESIGN A LENSProblem definitionPre-designStarting point selectionInitial analysisOptimizationFinal AnalysisPrepare for Fabrication© www.asia-masters.com

Problem DefinitionOther engineers or disciplines may define the requirements and boundaries of the design problem, but it is up to the lens designer to translate these into detailed optical specifications such as field of view and focal length. Your performance spec should be here also -- a detailed description of how good an image the lens must form (there are various types of optical evaluation used for this purpose) . There may be many requirements to meet, some of them contradictory in terms of how you approach the design (e.g., large aperture and light weight are usually opposing requirements that lead to tradeoffs and compromises).


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PRE-DESIGNOnce the basic factors are set, there are decisions to be made, such as reflecting vs. refracting? Number of elements? Overall size? Pre-design often involves paper and pencil sketching, including rough graphical ray tracing, with thin lenses standing in for real lenses. There are some graphical software tools that can really help in this stage, especially when pre-design trade-offs ("what-ifs") are needed, as they often are.


Starting Point SelectionConcept moves toward reality here, often with the help of an existing solution for a similar situation (books, patents, and your own company's previous work are rich sources here). Software comes into play here, since access to a database of existing designs can really speed up the selection process. Graphical and approximate methods can also be used to create a starting point "from scratch," if necessary.


Initial AnalysisIt helps to have a baseline analysis of the starting point so you can gauge improvement versus the spec. Aberration analysis may not be part of the spec, but it will probably be useful in the design process, especially in selecting variables for optimization.


OptimizationOnce you define a set of variables (parameters such as curvature, thickness, index of refraction, etc. that the program can change to try to improve performance), an error function (measure of optical quality, zero typically implying "perfection"), and constraints (boundary values that restrict possible configurations), you are ready to optimize the lens. Numerical methods are used to alter the variables in systematic ways that attempt to minimize the error function while honouring all constraints. Sometimes it goes smoothly, more often it doesn't, so changes are necessary, injecting designer guidance to resolve conflicts (though some software is pretty smart about many types of optimization problems, no program is yet fully automatic, if only because some requirements and aesthetic judgments may remain in the designer's head and not in the error function).


Final AnalysisAfter optimizing the lens, you need to see if it is actually doing what the original spec says it should do (optimization error functions may not correlate perfectly with specifications such as MTF or encircled energy). If it's not quite there, you may have to go back for some more optimization (perhaps adding variables or changing constraints). You may even have to find a different starting point in some cases.


Prepare for Fabrication

If the lens design meets its requirements, you will still have more work to do to prepare for fabrication.


Optical Lens Design - Safety & Regulations

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Transcript of Optical Lens Design - Safety & Regulations