# Optical lens design > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Optical_lens_design > Markdown URL: https://mediated.wiki/source/Optical_lens_design.md > Source: https://en.wikipedia.org/wiki/Optical_lens_design > Source revision: 1347256689 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|none}} {{More citations needed|date=August 2008}} '''Optical lens design''' is the process of [designing](/source/Engineering_design_process) a [lens](/source/lens_(optics)) to meet a set of performance requirements and constraints, including cost and manufacturing limitations. Parameters include surface profile types ([spherical](/source/spherical), [aspheric](/source/asphere), [holographic](/source/holographic), [diffractive](/source/diffraction), etc.), as well as [radius of curvature](/source/Radius_of_curvature_(optics)), distance to the next surface, material type and optionally tilt and decenter. The process is computationally intensive, using [ray tracing](/source/Ray_tracing_(physics)) or other techniques to model how the lens affects light that passes through it. ==Design requirements== Performance requirements can include: #[Optical](/source/optics) performance (image quality): This is quantified by various metrics, including [encircled energy](/source/encircled_energy), [modulation transfer function](/source/modulation_transfer_function), [Strehl ratio](/source/Strehl_ratio), ghost reflection control, and pupil performance (size, location and aberration control); the choice of the image quality metric is application specific.{{cite book |title=Optical System Design |edition=2nd |first1=Robert E. |last1=Fischer |first2=Biljana |last2=Tadic-Galeb |first3=Paul R. |last3=Yoder |location=New York |publisher=McGraw-Hill |year=2008 |pages=8, 179–198 |isbn=978-0-07-147248-7}}{{cite web |url=http://www.edmundoptics.com/technical-resources-center/optics/modulation-transfer-function/ |title=Modulation Transfer Function}}{{citation needed|date=July 2013}} #Physical requirements such as [weight](/source/weight), static [volume](/source/volume), dynamic volume, [center of gravity](/source/center_of_gravity) and overall configuration requirements. #Environmental requirements: ranges for [temperature](/source/temperature), [pressure](/source/pressure), [vibration](/source/oscillation) and [electromagnetic shielding](/source/electromagnetic_shielding). Design constraints can include realistic lens element center and edge thicknesses, minimum and maximum air-spaces between lenses, maximum constraints on entrance and exit angles, physically realizable glass [index of refraction](/source/index_of_refraction) and [dispersion](/source/Dispersion_(optics)) properties. Manufacturing costs and delivery schedules are also a major part of optical design. The price of an optical glass blank of given dimensions can vary by a factor of fifty or more, depending on the size, glass type, index [homogeneity](/source/Refractive_index) quality, and availability, with [BK7](/source/BK7) usually being the cheapest. Costs for larger and/or thicker optical blanks of a given material, above 100–150 mm, usually increase faster than the physical volume due to increased blank [annealing](/source/Annealing_(glass)) time required to achieve acceptable index homogeneity and internal [stress birefringence](/source/Birefringence) levels throughout the blank volume. Availability of glass blanks is driven by how frequently a particular glass type is made by a given manufacturer, and can seriously affect manufacturing cost and schedule. ==Process== Lenses can first be designed using [paraxial theory](/source/Paraxial_approximation) to position [image](/source/image)s and [pupils](/source/Entrance_pupil), then real surfaces inserted and optimized. Paraxial theory can be skipped in simpler cases and the lens directly optimized using real surfaces. Lenses are first designed using average [index of refraction](/source/index_of_refraction) and [dispersion](/source/Dispersion_(optics)) (see [Abbe number](/source/Abbe_number)) properties published in the glass manufacturer's catalog and through [glass model](/source/glass_model) calculations. However, the properties of the real glass blanks will vary from this ideal; index of refraction values can vary by as much as 0.0003 or more from catalog values, and dispersion can vary slightly. These changes in index and dispersion can sometimes be enough to affect the lens focus location and imaging performance in highly corrected systems. The lens blank manufacturing process is as follows: #The [glass batch](/source/glass_batch) ingredients for a desired glass type are mixed in a powder state, #the powder mixture is melted in a furnace, #the fluid is further mixed while molten to maximize batch homogeneity, #poured into lens blanks and #[annealed](/source/Annealing_(glass)) according to empirically determined time-temperature schedules. The glass blank pedigree, or "melt data", can be determined for a given glass batch by making small precision [prisms](/source/Prism_(optics)) from various locations in the batch and measuring their index of refraction on a [spectrometer](/source/spectrometer), typically at five or more [wavelengths](/source/wavelengths). Lens design programs have [curve fitting](/source/curve_fitting) routines that can fit the melt data to a selected [dispersion curve](/source/Sellmeier_equation), from which the index of refraction at any wavelength within the fitted wavelength range can be calculated. A re-optimization, or "melt re-comp", can then be performed on the lens design using measured index of refraction data where available. When manufactured, the resulting lens performance will more closely match the desired requirements than if average glass catalog values for index of refraction were assumed. Delivery schedules are impacted by glass and mirror blank availability and lead times to acquire, the amount of tooling a shop must fabricate prior to starting on a project, the manufacturing tolerances on the parts (tighter tolerances mean longer fab times), the complexity of any [optical coatings](/source/optical_coatings) that must be applied to the finished parts, further complexities in mounting or bonding lens elements into cells and in the overall lens system assembly, and any post-assembly alignment and quality control testing and tooling required. Tooling costs and delivery schedules can be reduced by using existing tooling at any given shop wherever possible, and by maximizing manufacturing tolerances to the extent possible. ==Lens optimization== A simple two-element air-spaced lens has nine variables (four radii of curvature, two thicknesses, one airspace thickness, and two glass types). A multi-configuration lens corrected over a wide spectral band and field of view over a range of [focal length](/source/focal_length)s and over a realistic temperature range can have a complex design volume having over one hundred dimensions. Lens optimization techniques that can navigate this multi-dimensional space and proceed to local [minima](/source/Maxima_and_minima) have been studied since the 1940s, beginning with early work by [James G. Baker](/source/James_G._Baker), and later by Feder,D.P. Feder, "Automatic Optical Design," Appl. Opt. 2, 1209–1226 (1963). Wynne,C. G. Wynne and P. Wormell, "Lens Design by Computer," Appl. Opt. 2:1223–1238 (1963). Glatzel,{{cite web |url=http://www.zeisshistorica.org/Glatzel.html |title=Dr. Erhardt Glatzel (Biography) |access-date=July 21, 2013 |publisher=The Zeiss Historica Society |url-status=dead |archive-url=https://web.archive.org/web/20130127182506/http://www.zeisshistorica.org/Glatzel.html |archive-date=January 27, 2013 }} GreyGrey, D.S., "The Inclusion of Tolerance Sensitivities in the Merit Function for Lens Optimization", SPIE Vol. 147, pp. 63–65, 1978. and others. Prior to the development of [digital computer](/source/digital_computer)s, lens optimization was a hand-calculation task using [trigonometric](/source/trigonometric) and [logarithm](/source/logarithm)ic tables to plot 2-D cuts through the multi-dimensional space. Computerized ray tracing allows the performance of a lens to be modelled quickly, so that the design space can be searched rapidly. This allows design concepts to be rapidly refined. Popular optical design software includes [Zemax](/source/Zemax)'s OpticStudio, [Synopsys](/source/Synopsys)'s Code V, and Lambda Research's [OSLO](/source/Optics_Software_for_Layout_and_Optimization). In most cases the designer must first choose a viable design for the optical system, and then numerical modelling is used to refine it.Fischer (2008), pp. 171–5. The designer ensures that designs optimized by the computer meet all requirements, and makes adjustments or restarts the process when they do not. ==See also== *[Optical engineering](/source/Optical_engineering) *[Fabrication and testing (optical components)](/source/Fabrication_and_testing_(optical_components)) *[Ray transfer matrix analysis](/source/Ray_transfer_matrix_analysis) *[Photographic lens design](/source/Photographic_lens_design) *[Surface imperfections (optics)](/source/Surface_imperfections_(optics)) *[Stray light](/source/Stray_light) ==References== ===Notes=== {{reflist}} ===Bibliography=== *Smith, Warren J., ''Modern Lens Design'', McGraw-Hill, Inc., 1992, {{ISBN|0-07-059178-4}} *Kingslake, Rudolph, ''Lens Design Fundamentals'', Academic Press, 1978 *Shannon, Robert R., ''The Art and Science of Optical Design'', Cambridge University Press, 1997. == External links == * [https://www.gnu.org/software/goptical/ The GNU Optical design and simulation library] {{Glass science}} {{Design}} Category:Geometrical optics Category:Glass chemistry Category:Glass engineering and science Category:Lenses Category:Physical optics --- Adapted from the Wikipedia article [Optical lens design](https://en.wikipedia.org/wiki/Optical_lens_design) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Optical_lens_design?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.