The optical industry is defined as companies having the capability to make precision lenses, mirrors, and prisms. The industry in U.S.A. is capable, but diffuse and investment poor. The industry will be an essential part of future commercial electro optical development, but it will require new imaginative management policies and capital investment.
A new compact optical scanner concept which is based on the optical fabrication capability of single point diamond turning is described. The unit relies on unusual reflective optical components which are impractical or impossible to manufacture by conventional means. A rotating disc which embodies a circular array of concave reflectors performs the horizontal scan in conjunction with a strip-like conical mirror located at the image plane. A unidirectional, 100% efficient scan results. The scan principle is explained and compared to polygon scanners. Mathematical relationships between the optical parameters are presented and system aberrations are briefly discussed.
The optical characteristics of a thermal imager employing a new compact optical scanner (CVROS) are described. The optical scanner employs mostly micromachined reflective components, some of an extreme asymmetric nature. The imaging properties of the scanner system are described in some detail and the paper concludes with a description of the current hardware.
In general the Gaussian intensity distribution of a laser beam is truncated at the pupil of the image forming system. The more the truncation effect is pronounced the less is the energy portion used and it deteriorates towards zero for a very pronounced beam expansion with an almost homogeneous illumination. For an image forming system the Gaussian intensity distribution of the incident beam may be interpreted as an apodization with a Gaussian amplitude in the pupil. Point image, encircled energy, MTF and depth of focus can be calculated from the pupil function that is defined in this way. For diffraction limited lenses it is shown how different pronounced truncations of the incident Gaussian beam will affect these image quality criteria. Applications of this effect occur e.g. in the optical data storage technology and in infrared laser applications. The smallest point image is obtained for homogeneous illumination of the pupil but the needed beam expansion utilizes only a small portion of the total incident energy. The central core is becoming wider the more the apodization effect is pronounced in the truncated Gaussian beam. The encircled energy functionsfor less pronounced apodi-zations are similar in the central region to those without apodization. Off a diameter corresponding to the first dark Airy ring an increase of the apodization effect that means a less pronounced truncation is reducing the fraction of the total energy contained in the outer region of the point image. For a 3x Airy disk diameter almost the total energy is encircled for a Gaussian distribution whereas only some 90% are encircled for homogeneous illumination. A non truncated Gaussian beam results with a reduction up to some 0.25 in the MTF values in the higher spatial frequency range. With a non-truncated Gaussian beam some 50% larger depth of focus is obtained compared with that for a homogeneous illumination.
Baird Corporation of Bedford, Massachusetts, has designed and developed two similar night vision goggles. These goggles are binocular viewing to the wearer's eyes, but use a single objective lens and a single image intensifier tube. Binocular viewing is achieved by dividing a single image and sharing it between the'viewer's eyes. The goggles are self-sufficient, independent instruments which can be simply and easily interfaced with a face mask that the viewer wears. This paper covers the main design considerations that are associated with achieving the goals of these goggle configurations and their performance. Baird's first goggle design is designated the GP/NVG; the second is designated the AN/PVS-7. The GP/NVG night vision goggle is a high-performance, single intensifier tube, passive night vision device that provides the user with a 40-degree field of view at unity magnification. The fixed aperture, f/1.0 objective lens collects the available light and images it on the fiber optic faceplate of the second generation image intensifier tube. The image intensifier tube converts the real image at the fiber optic faceplate into electrons across the image, amplifies them, and then reconverts the electrons into a real, visible image at the fiber optic output of the tube. This image is then collimated to appear as if it is coming from infinity, split in two, and reimaged by the relay lenses. The eyelenses provide a magnified image to the user. The user can adjust each eyelens to clearly view the output faceplate of the image intensifier tube. This adjustment is made only once for each user. The objective focus can be manually set for distances from 25 centimeters to infinity. The general configuration of this night vision goggle is similar to that of a pair of single objective binocular field glasses. It is extremely lightweight (with most of the main construction molded from plastic) and compact for easy handling. All adjustments and on/off switching have been "human" engineered for ease of operation. To meet the requirements of the U.S. Army, Baird is now developing the AN/PVS-7 goggle. The most significant difference from the GP/NVG goggle is the use of a third generation image intensifier tube in the AN/PVS-7 goggle. Other changes have also been made, but the general design is the same for both.
Hard optics (lenses, prisms, mirrors), fiber optics, or electro optics (television) may be used to relay an image from the focal plane of an objective lens to a location convenient for viewing. This paper compares performance for these three relay systems as applied to ground combat vehicle sighting systems. The conclusions show that, based on resolution, hard optics and fiber optics are preferred above television. Also, hard optics generally have better image quality than either fiber optics or television. Fiber optic and television systems may best satisfy particular applications with difficult integration requirements.
This paper deals with the design and fabrication of high performance doublets and triplets for relay lens applications. A Relay. Lens by definition is simply a lens or lens system used to transfer a real image from one section of an optical system to another. This same lens form can of course be used as an objective lens. The design guidelines for these lenses are as follows: A. λ/5 on axis for the completed lens assembly. B. Lens mounting to be as simple as possible e.g., lens mounted. directly into a lens barrel C. Overall cost important - lens must be assembled in somewhat of a production atmos phere.
A restricted and folded space envelope and the requirement to operate in focus without adjustment over a wide temperature range often leads to an optical system whose design departs significantly from the classical constructions. The design of a folded, passively athermalised 250mm F/2.5 vidicon lens is described, highlighting how the space and environmental constraints strongly governed the form of lens design. Two methods of built in test equipment injection are described.
The paper is intended to familiarize optical designers and systems engineers with the versatility of zoom lenses which operate in the thermal infrared waveband and especially the 8-13 micrometer band. Important system considerations and their effect on the mechanical, electronic, and in particular, the optical aspects of zoom lens design are highlighted. An example of a general purpose, modular zoom lens is described and a brief performance assessment is given.
Although mechanically compensated zoom systems for visible radiation working at a very low percentage of diffraction cut off are common place, infra-red zoom lenses are rare because they require a high state of correction (in order to work near to the diffraction limit at high spatial frequencies) and because of the problems associated with materials at this wavelength. Consequently, the diffraction limited 4:1 thermal imaging zoom system developed by PPE represented a significant optical design achievement. The continuation of this work has been to develop a 3:1 ultra compact thermal imaging zoom telescope to be built in production quantities to a severe environmental specification. The first prototypes have now been built and development work is being carried out in a number of areas. The opto-mechanical tolerancing is discussed with particular reference to the problem of volume production.
The optical materials available for the construction of a universal thermal imaging lens effective over the complete passband of germanium from 2 to 13 microns are considered. Suitable material combinations are suggested for the design of simultaneously achromatic and athermal objective lenses. The performance of some examples is compared with that available from narrow band germanium optics.
Historically, nonlinear response and errors introduced by variations in target reflectivity and surface finish have limited the use of fiber optic proximity probes. Recent experimentation with signal processing techniques as applied to these probes has resulted in linearized response over finite displacement ranges and minimization of the effects of variation in target surface. Implementation of these techniques in both analog and digital systems is discussed, and comparisons of the design tradeoffs in each approach are summarized. Experimental data gathered with compensated instruments are contrasted with the performance data from noncompensated devices. Secondary effects introduced by the compensation schemes are defined.
A well known optical scheme of an Infrared Linescan equipment has been considered. All the optical elements of the scanner are defined with reference to a rectangular coordinate system by a set of points. Expressions are derived to represent each of these points as a set of coordinates in terms of important scanner parameters. By computing and displaying these points including the raypaths, for any set of scanner parameters, the configuration can be quickly studied and optimized. A set of graphs indicating the optimum position of the rotating prism of the scanner for a few typical values of prism size and focal length of the parabolic mirrors are given.
A new CAD technique based on the direct method of calculus of variations is developed for the design of (narrow band) inhomogeneous thin films. The control of the index of refraction n(.) is incorporated into the optimization method and in addition n(.) satisfies inequality constraints nmin ≤ n(.) ≤ nmax imposed by technical and physical requirements.
We report here on the extension of earlier work to incorporate additional tolerances and requirements that have an impact on the cost of optical components. We include information reported by other authors which correlates well with our own findings. An example case is shown where the data base developed was used in a simple computer program to quickly calculate the cost impact of extensive tolerance changes on a large number of components. The possibility of an automated Lens Estimating System is discussed.
Photoconductive detectors, such as lead sulfide, can be incorporated in near infra-red instrumentation if their temperature related instabilities can be overcome. The changes in detectivity and spectral responsivity of lead sulfide due to ambient temperature fluctuations often exceed the "measurement signal" making accurate and repeatable measurements almost impossible. Additional inaccuracies can be introduced by opto-mechanical movement, electronic gain and offset changes, source fluctuations and detector noise. These are the common problems that the typical dual-beamed, dark-corrected laboratory spectrophotometers are designed to overcome. For certain applications sample temperature variation also introduces inaccuracies. This paper describes the design of a sensor that incorporates dual beaming and dark correction such as one would commonly find in a laboratory spectrophotometer. However, this sensor is used in a production environment in an on-line situation for the measurement of the spectral transmission properties of plastic film. Under these conditions, there is no "sample compartment" to contain a reference path. The method for achieving this path and experimental results will be presented.
The lens, for example a zoom lens for SLR cameras, is used as a projection lens and projects on a wall the image of a bar pattern. The AMMD sensors are 5 CCD linear arrays (1024 pixels each)checking simultaneously MTF at center of field and at four positions at 3/4 of field on the diagonals of the image. The AMMD electronics allow very quick focussing of the image and fast measurement of the squarewave MTF of the lens. Typical response time is 50 ms when one CCD is used and 250 ms when 5 CCD are used. The AMMD includes automatic gain control, calibration of each pixel for whole gain range, smoothing of datas before computation of MTF. Main components of the device are Reticon CCD (EGG), preamplifiers, analog multiplexing, A/D conversion, 68 000 micro-processor for computation. Controls include selection of 1 to 5 CCD, recalibration and 5 two digits displays. An example of optical adjustment and measurement of a zoom lens will be given, showing the advantage of the AMMD when they are used in workshop for series production.
Surface quality imperfections on the conductor screen in high-voltage cable can lower performance and cause premature cable service failure. The manufacturing of such cable involves extrusion of the conductor screen onto the bare wire, followed a few feet later by a second extruder which covers the conductor screen with an insulation jacket. Consequently, inspection of the conductor screen surface quality must be made on-line in real-time with the system remaining insensitive to sources of surface noise, which are inconsequential to cable performance. A cable surface monitor has been designed, fabricated and successfully tested at the Essex Power Conductor Division of United Technologies Corporation. The system, which senses light scattered from the flawed areas, is capable of noncontact inspection of the entire 360° circumference of a moving cable. Key features include: incandescent illumination; two-dimensional solid state array detection; electronic processing of the output to "flag" flaws; and no moving parts. A chart recorder is used to provide a permanent record of the inspection; and a video monitor may be used for on-line observation of the cable surface cross-section. In addition, the optical detection head does not close around the cable, but is slotted to facilitate installation and alignment on an operating extruder line.
The star simulator test stand simulates the Hubble Space Telescope focal plane interface for the fine guidance sensor and the wave front sensor instruments. It serves as the alignment reference for those instruments relative to the kinematic mounting points geometry in the Space Telescope. This simulator is also used to perform ground calibration of the wave front sensor instruments; it permits measurement of the fine guidance sensor transfer function and allows demonstration of fine guidance sensor fine lock. The following subjects are covered: Space Telescope terms and coordinates, image quality, image positions and tolerances, image characteristics, mirror specifications, aperture stop requirements, visual magnitude and color temperature requirements, light source assembly description, simulated aberrations used for each wave front sensor, test capabilities, verification tests, and image stability requirements for the star simulator test stand.
Advances in the computer utilization of finite element models of real structures have allowed more rapid design and analysis proceedures. The use of relevant computer codes by engineers is presently routine. In this regard the finite element method should be viewed as one of many analysis tools that can be utilized by designers. As in all such tools its strengths, weaknesses and proper use must be carefully considered. This paper gives some discussion and examples which indicate the judicious use of the method and how it usually forms a part of broader design and analysis considerations which make use of engineering judgement in a given situation.
Many aspects of geometric optics and wave optics are compatible with the finite element method of analysis. This fact provides a new and powerful tool in the fields of optomechanical design and optical systems engineering. Using special features available in some commercially available finite element codes, it is possible to include optical system parameters as a portion of the finite element model. The simultaneous solution of the optical and mechanical problems provides higher accuracy and consistency of the results, efficient calculation of many different load cases, and solutions to optics design problems which are difficult or impossible to handle in traditional lense design codes. This paper shows results possible in commercially available finite elements codes used to calculate optical system parameters, including surface figure changes, generalized optical ray tracing and wavefront error computation. The paper is illustrated with examples drawn from recent practice.
Optical systems including those applied in the areas of optical communication and optically assisted chemistry can involve energies of the order of 0.1 to 3 watts deposited in system optical elements. These energy levels are sufficient to induce significant bending of elements due to thermal gradients and to raise average elements temperature substantially. We have considered several forms of fused silica and ULE mirrors that control both the gradient induced bending and reduce the overall temperature rise. These mirror forms make use of high thermal conductivity materials bonded to the basic mirror and applications of conductively coupled heat sinks to reduce the effects of the thermal loads. We have found that a typical 2.5 cm diameter beam will result in surface deformations of less than 0.004 microns (peak) per deposited watt for steady-state conditions. For symmetric loading the majority of this deformation is found to be power. Finite element models of several mirror forms have been utilized to predict the detailed deflection distribution of the thermally loaded mirrors. Nastran predicted deflections were then decomposed into Zernike polynomial representations of the surface. By utilizing material choice as a degree of freedom in multi-element system design, we have found it possible to define beam handling systems that have very little thermally induced defocus for symmetric thermal loading. Heat rejection from the system utilizes controlled conduction to minimize structural deflections of the supporting structure. For asymmetric loading, higher order aberrations begin to appear and the control of thermally induced system wavefront error becomes more difficult. The major aberration, however, continues to be power for a significant range of beam decenter. Mounting geometry, thermal conductor configuration and bonding effects were included in the analysis. Good agreement between closed form and finite element analysis results was found for simplified check cases.
This paper presents a closed form solution of the biharmonic differential equation for the bending of a thin circular plate, which is kinematically supported and subjected to a generalized non-uniform thermal moment distribution. From this solution, normalized performance curves are developed for nonuniform thermal bowing and the ensuing RMS figure errors in flat circular mirrors. Several test cases of the closed form solutions were compared with independent Nastran based finite element solutions, and practically exact correlation between the two was obtained in all the cases. However, an analytical approach based on the closed form solution is significantly more efficient and cost-effective. The methodology of the closed form solution is not limited to flat circular mirrors. Some illustrative examples are included here from a similar, but somewhat more complex, closed form solution for curved circular mirrors.
The problems have long been recognized in supporting a conventional, disc-shaped optical element in the presence of gravity, so as to minimize the gravity-induced deflections. With the increasing size and quality of optics that are being used in space come correspondingly difficult problems in simulating a zero-gravity situation while supporting the optic on Earth. These problems are made worse by the fact that no additional stresses and strains should be introduced into the optic as it slowly changes shape because of, for instance, temperature drifts. In other words, a zero-gravity support should be kinematic. In this paper, we present a scheme for a zero-gravity support for a cylindrical optic. The type of optic being considered is used in grazing incidence X-ray telescopes, and consists of a cylindrical shell with a reflecting surface on the inside of the cylinder. The zero-gravity support presented permits extremely small gravity-induced deflections, yet contacts the mirror in only four places, and is therefore rather easily made kinematic. Moreover, no counterbalances or calibrated forces are needed - the distribution of the weight of the mirror itself guarantees that the off-loading will be calibrated correctly. We discuss the application of this concept for the alignment of an X-ray telescope. Using some thin-member approximations, we give some analytical approximations of the deflections. Also, some results of a finite element method analysis of the support are given. These results are interpreted in terms of a previously published set of functions that are orthonormal over the surface of a cylinder.
The boundary element method has evolved rapidly within the past decade and is now recognized as a reliable and efficient alternative to finite element and finite difference procedures, especially for problems encountered in Potential Theory and Elasto-statics. The technique consists in transforming the partial differential equations which govern the behavior in the domain over to a set of integral equations relating quantities associated with the boundary, and applying numerical procedures to generate approximate solutions for the boundary variables. This paper describes a general procedure, based on the weighted residual approach, for transforming the differential equations to integral expressions that form the basis for the Direct Boundary Element Method, and shows that boundary element and finite element methods can be interpreted as variants of the fundamental weak formulation for the problem.