The best glasses for use in the positive elements of an anastigmat lens are commonly understood to lie along the upper-left boundary of the glass map. That is, the best glasses have a high refractive index and/or a high v-value (low dispersion). These characteristics reduce the aberration contributions of the positive elements, and make possible lens designs which have smaller residual aberrations than designs which use glasses below the upper-left boundary. However this diagonal boundary line represents a trade-off between high index at one end and high v-value at the other. Thus the question becomes: "Which end of the boundary is best? Should one choose a glass with a high index at the expense of a low v-value, or vice-versa?" We discuss a controlled study of five triplet anastigmat configurations (of f-number and field angle), each using five glasses from along the boundary. The merit function (rms spot size), the MTF, and glass cost are presented as a function of the glass position along the boundary line.
A new imaging system format is presented which permits near-zero values for all the classical Seidel aberrations at relative apertures faster than f/1, with field angles of up to 7°arc, ~106 resolved pixels, a 600nm bandwidth in the visible/NIR, and zero vignetting. Performance is limited only by high-order aberrations. The only full- aperture component is a spherical mirror; all other surfaces are spherical except for an optional small weak zonal corrector. The new design approach is suited to aperture diameters of 100mm to >2m when used with appropriate electronic detectors. Thermal infrared variants are possible. In general, at least one order improvement in data acquisition rate is possible compared to that of existing designs.
A conceptual design has been developed for a Low-light Cloud Imager (LCI) to be used on a combination NOAA/DoD weather satellite. This lens was specified to have a ground resolution of 2.4 km over a 1 10 °x7 1 ° field of view. In order to accomplish this resolution on the night-side ofthe earth in the visible/near-infrared waveband (400-1000 nm), a very fast (f/1.72) lens was required. This paper describes the requirements on the lens, the effort to design a lens to meet the requirements, and the resulting performance of the conceptual design. Special attention is given to the following areas: understanding the performance requirements, simultaneously accomplishing a wide field of view and a low f-number, color correction, and distortion correction.
For many years optical designers have been intuitively aware of the value and potential that an inhomogeneous refractive index distribution can bring to the manufacture of precision optical instruments. Even so, designers have been cautious when considering lens designs with inhomogeneous glass, partly because of design difficulties, but mostly because of the need for controlled and reliable materials. In this paper we demonstrate the feasibility of graded index lenses by addressing the index control requirements that are needed for a diffraction limited lens. We chose for our analysis a rather stressing case: an F/1.5 plano-convex singlet. A general analytic expression for the index of refraction is developed for a perfect axial gradient lens (single color, on axis). Index errors were then added to the perfect index and the lens evaluated for wavefront quality. We found that index errors on the order of 1.6x10-3 rms produced aberrations of 0.04 waves rms, which is within the bounds of a diffraction limited lens. LightPath now routinely fabricates glass with much less index variation, making feasible the fabrication of repeatable diffraction limited lenses with inhomogeneous glass.
LightPath has been actively commercializing a family of axial-gradient glasses called the GSF glasses. These glasses have the same dispersion and refractive indices found in the conventional SF glasses. Therefore, in polychromatic design, it has only been possible to apply the extra degrees of freedom offered by GRADIUM® to negative elements by replacing a flint glass. This has shown that GRADIUM can significantly and positively affect polychromatic designs. For example, a seven element double Gauss lens was redesigned with GRADIUM, resulting in a six element design and a 27% improvement in rms spot size.1 Similarly, the Kodak Ektapro varifocal projection lens was redesigned reducing the element count from seven to five. Despite these impressive results, since most of the work done by any polychromatic system is done by positive elements— typically crowns, it is clear that the real potential of GRADIUM to polychromatic design could not be unleashed until GRADIUM crown materials were available. The GRADIUM GK glass family is one of several GRADIUM crown families under development. A number of examples will be presented to illustrate the advantages realized in optical design when GK glasses are used. Simple doublets as well as more complex multi-element systems will be discussed, some of which use both GK and GSF glasses and others which use only GK or GSF glasses.
Precise optical design requires detailed knowledge of the refractive index. GRADIUM® glasses further complicate these calculations because the refractive index is a function of axial position within the lens blank. LightPath has used a 16-coefficient Buchdahl dispersion model to allow the computation of the appropriate profile as a function of wavelength. The initial coefficients published for the GSF glass family relied on published data for base glasses and were restricted to the visible regime.1 There are many opportunities for use of GRADIUM materials in the NIR. Because there was no experimental data available to confirm the dispersion of these materials in this regime, experiments were conducted to measure the refractive index profiles of various GRADIUM glasses in the visible through the NIR. With the availability of this information, GRADIUM glasses can be applied to NIR imaging, communications, or other applications requiring information about the refractive index profile at these wavelengths. From these experiments of refractive index versus axial position as a function of wavelength, a revised dispersion model is presented for the GSF glass family. In addition, a new crown GRADIUM glass, which is under development, were also tested.
Commercially available GRADIUM® glasses present lens designers with new freedoms to increase performance or reduce the lens count, weight, and cost of optical systems. These glasses possess an axial gradient through the entire glass thickness with large changes in refractive index (?n), dispersion (?v), or other properties. GRADIUM glass lenses containing large refractive index gradients are especially powerful for reducing aberrations in both monochromatic and chromatic lens systems. The purpose of this paper is to explain the general properties of GRADIUM glasses, how these glasses and lenses are manufactured, and the specifications and tolerances of the glasses and lenses. Using GRADIUM glass lenses is very straightforward; the lenses are fabricated with spherical surfaces and used like homogenous (single index) lenses. Comparisons between the theoretical design and actual lens performance for several commercial lenses are presented.
Using refractive-diffractive hybrid system in multispectral camera to compensate thermal defocus effect is considered. The paper gives the design principle, the specification and layout, calculates the system MTF of a soaking environmental temperature and pressure variation compared to the conventional design.
The design of a hybrid diffractive-refractive singlet to replace a conventional doublet objective lens is studied. The method for designing the initial configuration is presented based on the correction of the spherochromatism and spherical aberration. The examples given in this paper show that by using the modified formula one can get a better initial configuration without the significant spherochromatic aberration introduced by the aspheric term of DOE's polynomial. Finally a hybrid singlet in visible wave band ( ? from 656.3nm to 486.1 mn) is successfully designed. In comparison with traditional doublet, this hybrid singlet has smaller aberration, simplified configuration and only one material BK7 used. Experimental results show that the diffraction efficiency of DOE is the bottleneck for the hybrid optical system to be actually used in the image field.
The design of optical mounts and adjustable mechanisms is a complex process, which requires collaboration of experts from various disciplines. Many small organizations can not afford to have in-house experts to perform complex optomechanical design tasks. A user-friendly knowledge-based expert system has been developed to guide a novice optical engineer in selecting optimum mirror and lens mounts, and adjustment mechanisms for a particular application. The system consists of pictures and design database of several optical mounts and adjustment mechanisms. Based on the user defined specifications, this expert system searches the database, and presents a list of suitable devices for the application through an inference process. This expert system can also be used as training tool for entry-level optical and mechanical engineers.
Lithographic lenses often exhibit shifts in focal position and magnification due to the influence of the heating transient initiated when the illuminator is turned on. Evaluation of these effects requires simultaneous solution of the equations of heat transfer, elasticity and optical images. "Unified” analysis techniques were used, including the Optical Analogtm, which provide accurate analysis of the influence of all the design variables on the optical image. This paper describes the modeling process in detail as well as the checkout techniques used to assure that the physics of the problem had been adequately captured in the model. The paper closes with a discussion of some of the valuable insights that were gained during the analysis.
Temperature changes in optical elements, alone and in combination with material inhomogenieties, will cause shape and refractive index changes that add wavefront errors (WFEs) to high performance optical systems. After a brief discussion relating system performance to system WFE, we show how WFEs combine to give system WFE estimates, and derive some simple algebraic formulas for use in estimating WFEs for selected thermo-optical effects.
Optical design software integrated with AutoCAD provides optical designers with the power and tools mechanical designers have enjoyed for some time. Spreadsheet entry is replaced by simple CAD commands such as Move, Rotate, Point and Drag. Packaging is enhanced when optical components and actual ray traces are present in the mechanical design. Implementing optical components as single surface objects enables the creation of uncommon multi-surface components and waveguides. A rendering feature converts surfaces and ray traces to objects ready to be rendered providing a photorealistic presentation.
A computer program, TracePro™, has been written to simulate the propagation of optical flux through optomechanical systems. The program is based on an industry-standard solid modeling kernel, ACIS®, thereby obtaining consistency and reliability in modeling three-dimensional geometiy, as well as the capability to share data with other ACIS-based applications. The program uses the Monte Carlo ray-trace method including variance reduction techniques to simulate optical effects. Ray splitting is used to simulate partial reflection and scattering, and importance sampling is used to enhance sampling for difficult radiometric analyses such as stray light analysis. A graphical user interface makes the software accessible to engineers who are not optical specialists, while a macro language provides access to more complicated operations. Extra software modules convert lens design data from commercial lens design programs into solid models.
The traditional approach to opto-mechanical design is a top-down process where the optical designer communicates to the mechanical designer, “these are the tolerance requirements I need” to meet my system performance requirements. The optical designers typically communicate these tolerance requirements as tilts, decenters, and locations of optical elements (lenses, mirrors, prisms, lens cells, etc). The mechanical designer uses these optical tolerance requirements as inputs to his/her mechanical design process. The output of the mechanical design process is a set of piecepart dimensions and tolerances. These dimensions and tolerances communicate to the manufacturing shops “this is what I need” to meet the optical performance requirements. A significant drawback to this top-down process is that we have no way of knowing how well the manufacturing process can build parts that meet these tolerances. This paper proposes a different approach, where we the mechanical designers use the knowledge of the manufacturing processes as inputs to the mechanical design. With this new knowledge, we can predict the mechanical performance of the system. The mechanical performance, in turn, becomes an input to the optical design. This paper also shows how we have automated this new approach and applied it to the design of an optical system design.
In the present work we have demonstrated a family of laser focusing doublets. All members of this family are diffraction limited and their optimal performance at He-Ne laser wavelength has been investigated. Laser focusing lenses are widely used for video and optical disk systems. They are usually small with high numerical aperture operating at single wavelength. They cover a small field of view, are diffraction limited, and nearly aplanatic. The present diffraction limited family consists of six air-spaced doublets for which the F-numbers are 2, 2.5, 3, 4, 5.6 and 8. An automatic design of optical systems has been used to optimize the monochromatic spherical aberration for the axial point. The effective focal length (EFL) of the family is 100 mm and the field of view tolerance is 0.00001 rad. The performance of the doublet is shown through the Modulation Transfer Function (MTF) curve, which indicates that the optical system is diffraction limited. This is also presented from wavefront point of view by calculating the Strehl ratio of the system. The Petzval curvature is small so the system can be considered as aplanatic on axis. The overall length (OAL) of the system is small which makes it easy to handle. The most interesting member of the family is the F/2 lens due to significant improvement over a previously reported design. The F/2 system in our design has less higher order spherical aberrations compared to the existing design.
High - resolution spectrometer was designed to resolve the fine structure of discharge emitted radiation near hydrogenous line 4648.8 Å. To achieve high resolution with relatively big aperture and only spherical optics the new method of the optical mounting calculation was applied. As it was mentioned1, some aberrations of the first part of the double monochromator can be compensated by its second part. For present device we chose the Rowland circle geometry for one wavelength. This geometry has no defocusing and meridional coma aberrations. The sagittal coma and the first order astigmatism were compensated using double monochromator mounting. To reduce aberrations for other wavelength of the spectral region the slight nonequidistancy of the grooves of two concave diffraction gratings was introduced. The device consists of two concave diffraction gratings with 2700 grooves per mm and the radius of curvature 500 mm. The theoretical limit of resolution for this case is 0.015 Å. The aberration limit of resolution, calculated using the mathematical model of spectrometer is 0.006 - 0.03 Å for the spectral region 4641.8 - 4661.6 Å. Because of property of the double monochromator mounting to compensate the second order astigmatism aberration1, the entrance slit of spectrometer can be high, more than 10-20 mm. Then, it is possible to analyse a number of emitting points simultaneously.
Generalized ray-tracing computer programs, which simulate the propagation of light through three-dimensional models of optical systems, have their origin in the 1960s. Progress in generalized ray-tracing software has proceeded on three fronts since then, in the fields of optical design and analysis, the radiation transfer part of the thermal analysis problem, and in photorealistic computer graphics rendering. These three fields have evolved largely independently, though they have much in common: computer representation of three-dimensional geometry, computation of ray-surface intersections, propagation of optical flux, and modeling of the interaction of light with matter including the use of BRDF and BTDF to model surface scattering. The size of the computer graphics industry dwarfs the others, as measured by the number of workers in each field and the volume of published literature. Only recently have ideas from the computer graphics industry been utilized in the optical analysis field.
Precision plastic optical systems frequently depart from traditional design geometries and often include integrated optical and mechanical features. Light can often propagate through the plastic "mechanical" features as easily as through the optical surfaces. This paper discusses modeling and analysis techniques that have been used successfully to quantitatively evaluate energy collection and stray radiation performance in several unusual plastic optical systems. Examples will include a fluid flow sensor and an injection molded plastic triplet imaging system.
With the development of faster computers, the ability to design and optimize complex optical systems has been dramatically improved. This directly translates into faster product development cycles with less need to build costly prototypes. Systems using light pipes, faceted Fresnel lenses, and nonimaging optics demand non-sequential raytracing, generalized surface modeling, and scattering and/or ray-splitting off of surfaces. Addressing these issues slows computation, resulting in time constraints that, in the past, prevented the use of software codes to do much more than analyze complex systems. Now, a system’s radiometric performance can be evaluated in minutes instead of hours, allowing more exotic computer aided design and optimization techniques to be used. We present rules-of-thumb on how to design, optimize, and tolerance illumination systems. Examples of systems include faceted light pipes and Tailored Edge-Ray Concentrators that create uniform illuminance. Applications for such systems are broad and include automotive, appliance, and room lighting.
As computation speeds have increased dramatically over the last decade, we can now trace enough rays in a short enough time to use ray tracing to predict the performance of an illumination system. The biggest obstacle, however, to accurately model, and thus design, illumination optics is in developing an accurate source model3. In the past, sources were simplistically modeled as very basic geometrical shapes such as points, spheres, or cylinders. Some illumination design software now allows an engineer to create a more complex theoretical model of the source that could include multiple geometrical shapes to more closely approach real source properties. These models, however, are time consuming to create and still fall short of the goal to accurately model the system. Rather than to build up a source model based on a (combination of) geometric shape(s) with some assigned output distribution based on either measured or theoretical data, the authors will demonstrate a new technique for developing and applying source models based on careful, consistent and general measurements. The measurement system consists of a CCD camera mounted on a 2-axis goniometer that allows images of the source to be captured over variable polar and azimuth increments. These source models produce accurate results even when optical surfaces are placed near the source.
As illumination systems geometries become more complex, and specifications on them more stringent, physical prototyping is becoming more costly. Having the ability to accurately model illumination systems using software can significantly reduce the number of prototypes. Software also allows the user to quickly experiment with different designs which couldn't otherwise be modeled using prototypes. This paper discusses how one would use LightTools, a new 3-D interactive CAD modeling software package which can solve many illumination problems. Examples of illumination systems will be presented showing quantitative illuminance and intensity output.
Aerodynamic headlamp lenses have presented several challenges and opportunities to the Automotive lighting community in terms of Computer Aided Optical Design, Raytrace simulation, Visualization of end parts and communication of optics information to tool shops. This paper will examine existing practices of headlamp lens design and describe a new optics automation tool (FALCON) which effectively integrates design, simulation, visualization and optics manufacturing using IGES.1 It will conclude with the benefits of automating optical lens design.
Laser alignment systems frequently use position sensitive detectors such as CCD arrays and lateral or segmented photodiodes. Nonlinear properties of the detector elements and optical aberrations are usually important design considerations, but the effect of small amounts of vignetting is often neglected. This can be an important factor in achieving highly accurate beam position measurement, especially for systems which work at long ranges or use expanded beams. In cases where the size of the optical aperture must be minimized due to cost considerations, it can be difficult to choose the optimum clear aperture diameter without lengthy analysis. Sometimes, simple rules of thumb based upon “X times the 1/e2 diameter will work fine, but the designer still needs to know how “X” relates to precise instrument performance in order to rationally choose a value for it. The objective of this paper is to provide a thorough description of the tools needed by the electro-optical engineer in order to solve these kinds of problems. Analytical and numerical methods are outlined which simulate truncation and its effect on both the point spread function and the center of energy. Algorithms are described for computing simple vignetting geometries and results are presented for a variety of sample cases showing the magnitude of the effects. Limitations of the theory are also listed in order to determine its applicability to other kinds of systems. Application as both a design simulation tool and a real-time software compensation system is suggested.
Based on Fermat’s Principle, a set of formulae for ray tracing through diffractive optical elements is derived in this paper. These formulae do not involve the calculation of local fringe spacing and direction, and take a simple, Snell’s-Law-like form. Yet they are completely general, and can be applied to diffractive optical elements with arbitrary continuous phase function formed on substrates of arbitrary shape. Then the concept of the extended Snell’s law, which is applicable to any kind of surfaces, is presented, and so make it easy to improve the traditional optical program into a hybrid one with the ability to design and analyze diffractive and hybrid elements. Some testing experiments have been made by using a diffractive optical lens with large astigmatism. The computational results are compared with experimental data, and the correctness of the formulae is verified.
This is an improved version of the prism fingerprint sensor described in an earlier paper by Bahuguna et. al.1. The new design uses a modified holographic grating glued to a right-angled truncated prism and is more compact than the previous one.
At the moment the majority of the programs of automated account has an opportunity of display of a drawing of optical system with a course of beams as 2-D of sections, and also as 3-D carcass or solid state of model. A following level is reception stereo image of optical system, it is rather important at configuration of complex optical systems (HUD of displays, extraxis telescopes, scanning termovision and etc.) Besides stereo image is the important part of technology virtual prototyping of optical systems, application of which will allow essentially to reduce a way from the project up to realization of real optical system.
Technique of modeling diffraction of microstructure of the image and image of extended objects in limits of izoplanatc zone in view of the image both distribution of intensity, and color is considered. For optical systems, forming the image in UV and IR areas of a spectrum, generalized concept pseudo - natural colors is entered. The developed technique is entered into a mode of diffraction analysis of structure of the image in a software WinDEMOS v.1.0.