• PHOTOGRAPHIC GRAIN NOISE SUPPRESSION BY DENSITY QUANTIZATION: ITS INFLUENCE ON IMAGE QUALITY

      Hoffman, Robert Stocking, 1944- (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1975-12)
      A technique is described for suppressing unwanted grain noise in scanned and digitized photographic images. The technique employs the rms granularity statistics of the film to divide, or quantize, the density range of the digital image into distinguishable ranges of density. For Eastman Kodak type 3414 film, the rms granularity statistics determined indicate constant Selwyn granularity for the range of scanning spot diameters from approximately 16 to 4 micrometers, and this result agrees with Kodak data for a 48 micrometer diameter spot. For spots from 16 to 4 micrometers diameter, the rms granularity is also determined to be a function of the square root of diffuse density. The number of distinguishable density levels, required to sup- press the grain noise of the digitally processed image, is found to be directly related to the scanning spot diameter. Finally, evaluation of the resulting digitally processed images indicates that subjective image quality is directly related to the spatial resolution of the image. That is, with the grain noise suppressed, subjective quality is improved by scanning the original image with a smaller diameter spot.
    • ELECTROENCEPHALOGRAPHIC CORRELATES OF VISUAL STIMULUS CHARACTERISTICS AND DECISION CERTAINTY

      Seeley, G. W.; Yee, B.; Wheeler, L. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1975-10)
      The problem: to what extent do cortical evoked potentials correlate with differences in complex visual stimuli and with differences in observer confidence that a correct judgment has been made? Electroencephalographic records obtained in response to complex visual stimuli were examined in two studies involving thousands of stimulus presentations and a variety of stimulus characteristics. Six observers made responses to subsets of the stimuli. A signal detection paradigm governed the experimental procedures and analyses. Even when stimulus differences were extremely small, it was often possible to make accurate assignments of sets of averaged EEG's to the appropriate stimulus conditions and to an observer's degree of confidence in the correctness of his judgment.
    • DIFFRACTION OF LIGHT BY SOUND WAVES

      Mahajan, Virendra N. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1974-06)
      Diffraction of light by a sinusoidal sound wave is discussed in detail. Assuming that the sound column modulates only the phase of the incident light in both time and space, the frequencies, wavevectors, and intensities of the diffracted waves are obtained for normal incidence. A transition length (width of sound beam) is defined, above which all diffraction effects disappear due to destructive interference. Constructive interference is obtained, however, provided the light is incident at the Bragg angle, in which case the diffracted beam appears to be reflected from the acoustic wavefronts. The transition length thus separates the region of multiple -order (Raman -Nath) diffraction from the region of single -order (Bragg) diffraction. It is found to be directly proportional to the square of the acoustic wavelength and inversely proportional to the optical wavelength. In the case of Bragg diffraction, the energy is exchanged sinusoidally between the diffracted and undiffracted beams. Owing to the finite width of the sound beam, the Bragg condition is relaxed, and the effect can be used to control the direction and phase of the diffracted beam or to determine the angular distribution of the acoustic power. Next, a particle picture of diffraction in terms of photons and phonons is given. The diffraction process is described as a single as well as a multiple three -particle interaction. The effects of finite optical and acoustic beamwidths and variation of acoustic frequency are considered in terms of momentum conservation. Finally, an analysis based on Maxwell's equations for an arbitrarily polarized light beam propagating in an arbitrary direction is given using the partial -wave approach. A set of coupled difference- differential equations for the diffracted amplitudes is derived from the optical wave equation and analytic solutions are obtained in the Raman-Nath and Bragg regions of diffraction. The results for normal and Bragg incidence are obtained as special cases. Limits of the two regions are defined, thus giving a transition region in which numerical solutions can be obtained.
    • POLARIZATION DISCRIMINATION TECHNIQUES FOR OPTICAL PROCESSING

      Richard, Stephen P. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1973-08)
      The object of this study was to determine the utility of polarization -discrimination techniques for active optical processing. A baseline of static performance must be established before these techniques can be applied to real -time processing. The theoretical foundation for an alternative to the Vander Lugt technique of re- cording complex spatial filters had been laid by Marathay in 1969. On the basis of his theory, a photosensitive Vectograph TM technique was investigated, in which the image is produced as a polarization pattern rather than as the silver grain image of conventional photography. (1) Photographic characteristics of sensitized Vectographs were determined. The resolution ( >700 1p /mm) and the gray scale achieved indicate that the Vectograph material can also be used for recording Vander Lugt filters. (2) Theoretical analysis showed that the technique can be used to image and process objects in the same system without removal of the filter. It can also be used to generate halfwave plates for the pupil functions described by Toraldo di Francia for superresolution. (3) The Vectograph can perform addition and subtraction of functions recorded on it; it also is suitable for recording real -bipolar filter functions. (4) Variable- contrast images can be recorded. A variable-contrast Vectograph tar- get (VCVT), developed for optical testing, can not only vary the contrast of the recorded image but also reverse its contrast. In a similar fashion, a spatially variable birefringent filter (SVBF) was developed that permits spatial control of the wave- length of the transmitted light. Static and dynamic electro-optical properties of liquid crystal mixtures of cholesteryl-chloride, cholesteryl-nonanoate, and cholesteryl-oleyl-carbonate were studied to determine their feasibility as the modulator in a proposed photoconductor-liquid crystal sandwich, which would be used as a reversible recording medium. (1) Previous research had indicated that cholesteric liquid crystals are circularly dichroic in a narrow wavelength band. The present work showed that light transmitted within this band is actually elliptically polarized. The degree of ellipticity depends on the relationship between the probing wavelength and the wavelength at which the sample becomes circularly dichroic. Outside this narrow wavelength band, the crystals exhibited pure optical activity. (2) The dynamic electro-optical properties of the cholesteric trimixture were measured. An alternating electric field applied parallel to the helical axis of the liquid crystals resulted in a hysteresis in the electro-optical rotatory power of the crystals. The magnitude of the hysteresis would limit cycling of these liquid crystals to a maximum frequency of ^0.10 Hz. (3) A bias voltage applied to the crystals in an attempt to improve the frequency response resulted in a field- induced memory. When the bias voltage was maintained, the optical rotatory power failed to stabilize. Prolonged exposure to the bias voltage severely diminished the electro-optical rotatory power of the crystals.
    • Laboratory Evaluation of Eleven Image Intensifiers

      Cromwell, Richard H.; Dyvig, Ronald R. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1973-08)
      A number of laboratory tests have been carried out at the image tube laboratory of the Optical Sciences Center on 11 selected image intensifiers in order to compare and evaluate their performance. The electrostatically focused tubes tested are as follows: ITT F-4708 (1 stage), two samples of a Varo 8605 (1 stage), Varo 8605DC (1 stage), ITT F -4724 (3 stages), RCA 8606 (3 stages), and Varo 8606 (3 stages). The magnetically focused tubes are EEV P829D (5 dynodes), ITT F-4089 (1 stage), RCA C33011 (2 stages), and RCA C70021AEP2 (3 stages). The tests included measurements of limiting resolution (of the intensifiers directly and of photographs obtained with the intensifiers), square -wave response, geometrical distortion, shear characteristics in fiber-optic faceplates, photographic speed gain, uniformity of response, light- induced background, dark emission, and detective quantum efficiency (DQE) of intensifier -photographic emulsion combinations. The most significant result of the tests is that a comparison among tubes with a similar number of stages (or gain) showed that the magnetically focused intensifiers were generally superior to the electrostatically focused intensifiers in resolving power, geometrical distortion, and uniformity of response. However, the electrostatically focused tubes exhibited only about one fifth the light- induced background of the magnetic tubes. Also, a mean relationship was found between the limiting resolution of the intensifier output image and the limiting resolution that is recorded on a photograph of the intensifier. Other particularly notable results include (1) the causes and characteristics of several different types of response nonuniformities, (2) the identification of sources of light -induced background, (3) the photographic speed gain required of an intensifier to obtain the highest peak DQE possible and also that required to make the system behave as a "single- photon event" detector, (4) the identification of some especially undesirable characteristics of a potassium chloride transmission secondary emission (TSE) dynode intensifier (EEV P829D), and (5) the performance of three relay lenses for intensifiers.
    • Chirped Pulses in Laser Amplifiers

      Gieszelmann, Edward L. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1973-06)
      This dissertation presents a theoretical investigation into the production, evolution, and asymptotic form of chirped pulses in homogeneously and inhomogeneously broadened laser amplifiers. Amplifier equations of motion are obtained in a form appropriate for dealing with such frequency-modulated pulses. The transient response of laser amplifiers to variously chirped Gaussian input pulses is studied parametrically using numerical solutions of the amplifier equations. The chirping mechanisms of the intensity dependence (Kerr effect) and the quadratic frequency dependence of the index of refraction are discussed briefly, as are the chirps produced by them and the amplification of Gaussian pulses in their presence. The amplifier whose host exhibits these dispersive effects is treated as a sequence of pairs of slices. One of each pair amplifies and exhibits the Kerr effect; the other has an index with a quadratic frequency dependence. This slice model is used to obtain steadystate pulses in both homogeneously and inhomogeneously broadened amplifiers whose host indexes have a quadratic frequency dependence. The steady-state pulse characteristics are determined as functions of amplifier parameters and the index curvature. The principal results are as follows: The homogeneously broadened amplifier responds predominately to the temporal character of a chirped input pulse whereas the inhomogeneously broadened amplifier response depends primarily upon the pulse spectrum. Of three important concepts (area theorem, echoes, and optical nutation) used to describe unchirped pulse amplification in inhomogeneously broadened media, only photon echo is useful when pulses are more than slightly chirped. The presence of the Kerr effect can produce significant chirps on large pulses. Amplification in the presence of the Kerr effect produces pulses strikingly similar to experimental results. Quadratic frequency dependence in the index has very little influence on most pulses in short amplifiers but has a cumulative effect in long amplifiers and laser oscillators. Chirped steady-state pulses exist in both homogeneously and inhomogeneously broadened amplifiers when the host index has such frequency dependence. In the homogeneously broadened case, they exist at relative gain levels dramatically below other theoretical predictions. They occur in the inhomogeneously broadened case only for the smaller index curvatures.
    • FURTHER STUDIES OF THE DETECTABILITY OF DEGRADED VISUAL SIGNALS

      Wheeler, Lawrence (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1973-06)
      Observers responded to abstract forms (quadrigons) in six experiments, under a signal detection paradigm. Duration of stimulus exposure was shown to have strong effects upon detection accuracy (two studies); immediate feedback of accuracy information to observers affected performance chiefly by influencing guessing bias, not sensitivity (two studies); images that had been blurred and then deblurred by means of an analog device were compared with unblurred originals, and the effects of the retrieval process (deblurring) were characterized quantitatively by a signal detection index (one study); and electroencephalographic correlates of signal detection responses were found to vary with performance accuracy and observer confidence (one study). Discussions of the theory of signal detectability and of electroencephalography, as tools in the study of image quality and of observer sensitivity, are included in the report.
    • The Design, Construction, and Testing of the Optics for a 147-cm-Aperture Telescope

      Buchroeder. R. A.; Elmore, L. H.; Shack, R. V.; Slater, P. N. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1972-12)
      In this report we describe the work carried out under contract F19628-72-C-0047 entitled "Geodetic Optics Research" for the Air Force Cambridge Research Laboratories (AFCRL). The work consisted mainly of the fabrication of the optical components for a telescope with a 152 cm-diam (60-in.) primary mirror masked down to 147-cm diam for use by the AFCRL for a lunar ranging experiment. Among the noteworthy achievements of this contract were the following: (a) Completion of the primary and secondary mirrors for a high -quality 147 -cm- diam telescope system in eight months from the start of edging the primary. (b) Manufacture and testing of a unique center mount for the primary according to an AFCRL design that allowed for a thin-edged and therefore less-massive mirror. (c) Development of a quantitative analysis of the wire test for calculating the departure of the mirror figure from the design figure quickly and accurately after each polishing step. This analysis method in conjunction with a knowledge of polishing rates for given weights and diameters of tools, mirror, and polishing materials should considerably reduce the polishing time required for future large mirrors. The emphasis in this report is on these three items; however, considerable work was also undertaken in telescope design; null lens design and mounting; tracking optics design, fabrication, and mounting; and special thin -film coatings for the laser send and receive optics.
    • INVESTIGATION OF TECHNIQUES FOR FABRICATING PLASTIC OPTICAL COMPONENTS

      Blecher, Stephen (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1972-08)
      Because of their light weight and low cost, transparent plastics would seem to be good materials for optical components. This thesis deals primarily with the feasibility of producing large ( >4 -in. -diam) plastic components of moderate precision (surface accuracies 1 fringe per inch of diameter). The structure and the physical and optical properties of plastics are discussed, with emphasis on their advantages and limitations for optical use. A series of experiments on grinding and polishing of plastics was conducted. Data are presented on grinding rates. Several polishing processes were evaluated, and a polishing technique for plastics was developed. Polishing rate data and surface roughness data are presented for several polishing processes. With proper techniques, we estimate that accuracies of about one fringe per inch are obtainable. A series of experiments was conducted on a process called compression forming, in which heat and pressure are applied to machined preforms in an attempt to obtain precision optical surfaces. The process is described in detail, and experimental results are discussed. Based on experimental results, improved processing conditions are suggested. Further experiments would be required to determine the ultimate process capability.
    • Evaluation of Image Intensifier Tubes Using Detective Quantum Efficiency

      Smith, Gregory H. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1972-07)
      In recent years, many new image detectors have been developed that are sensitive to extremely low light levels. These devices have given new importance to a performance criterion called detective quantum efficiency, or DQE. The subject of this investigation is to develop the basic experimental technology necessary to measure DQE of image detectors, and to apply these techniques specifically to photographically recorded image intensifiers and to unaided photographic emulsions. DQE is defined as the square of the ratio of output S/N to input S /N. Input S/N is determined by the input photon statistics. Output S/N is determined by measuring the recorded image. Two ways of measuring DQE are the single-level gradient method and the two-level AD method. The AD method gives a more appropriate measure of the performance of image intensifiers that have light- induced background. A special two -channel projector was built to measure DQE by the AD method. Its function is to superimpose the image of a signal target upon a uniform background irradiance. The same instrument can be used to obtain DQE measurements using the gradient method. DQE was measured for two image intensifiers (a high -gain TSE tube, model P829D, made by EEV, and a two -stage cascade intensifier, model C3301 1, a Carnegie tube made by RCA) and two unaided photographic emulsions (Kodak IIa -O and Kodak Medium Contrast Projector Slide). The results show that different image detectors may have considerably different DQE performance. For example, at 425 nm, DQE values for the Carnegie tube were more than 20% (the quantum efficiency of the input photocathode is 28 %) whereas both of the unaided photo- graphic emulsions gave peak DQE values no greater than 0.8 %. In addition, the peak DQE of the Carnegie tube occurred at roughly 10' photons /cm2 whereas the peak DQE of unaided IIa-O occurred at 109 photons /cm2 (both at 425 nm). Furthermore, single photon event detectors (such as high -gain image intensifiers) have a peak DQE near zero exposure with DQE decreasing as exposure increases whereas multiple photon event detectors (such as unaided photographic emulsions) have zero DQE near zero exposure, a peak DQE at an exposure which yields a corresponding output density of about 0.2 above fog, and a decreasing DQE for further exposure increases. Also measured were granularity, light- induced background, system modulation transfer functions, and relative system speeds.
    • PROPERTIES OF OPTICAL DESIGN MODULES

      Mercado, R. I. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1972-06)
      In the first part of this report the class of two-surface optical systems designated as modules, which have zero third-order spherical aberration relative to a pair of conjugate planes one of which is at infinity, has been further analyzed using the parameters of the Delano y,ÿ diagram. For a given set of three indices of refraction n1, n2, and n3, functional relationships among the y,j7 diagram parameters that eliminate simultaneously other Seidel aberrations are derived. Expressions for zero coma, astigmatism, and Petzval curvature are also given. Criteria for selecting the non - optical parameter k, which defines the desired properties of modules, are described. A one -to-one correspondence between the canonical optical parameters defined in previous studies of modules and certain quantities derivable from the y,ÿ diagram representation is shown. Critical values of the free parameters of modules for both the real and the imaginary cases are derived and defined relative to the y,,y diagram parameters. In the second part of this report an analysis is made of a class of modules referred to as the imaginary -case family depending on the new parameter 0. The critical values 00, 0_, and 0 *, which correspond to those obtained for real-case modules, are defined, and the conditions for their existence in the domain of are derived. These critical values, whose counterparts in the real case exist for both refracting and reflecting systems, do not exist for refracting imaginary-case modules when the indices of refraction are restricted to commonly available optical glasses. The critical values of 0 exist and have fixed values for all reflecting module systems. A method is proposed for classifying imaginary-case modules, which would permit comparison for coupling purposes.
    • Measurement of Small-Angle Scatter from Smooth Surfaces

      Orme, Gordon R. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1972-02)
      Measurements of the scattering of reflected light as a function of angular separation from the specular direction were made on aluminum-coated flat glass samples with surface roughnesses ranging from 1.0 nm to 70 nm rms deviation from the mean surface. Small -angle scatter (measured between 0.33° and 1° away from the specular direction) was investigated using light that had passed through a narrow slit; a measure of the scattering magnitude was provided by comparison of the far -field diffraction patterns produced by the slit, reflected from the samples and without the samples in place. The slit used to produce the diffraction patterns was optically processed to be smooth enough so that without the sample in place the minima of the diffraction pattern would be well defined and of lower magnitude than the scattered flux produced when the samples were in place. By considering the effects of the scanning aperture, it was determined that the measured magnitude of the minima agreed with those predicted by the use of Kirchhoff theory to within a factor of three. Comparison of small-and large-angle scatter measurements made on the same set of samples indicated that a transition region between the two types of scatter may exist in the region of 1° to 5° away from the specular direction. Because separate instruments were used for the small-and large-angle measurements, the results are expressed in terms independent of the measuring instrument's geometry. The measured results were compared to a theory in which the choice of the scatter function, and by implication the autocorrelation function, could be arbitrary. This comparison revealed that the choice of the hyperbolic secant function, rather than a Gaussian function, provided a good fit to the small-angle data. By fitting a curve to the small -angle data, it was possible to estimate the autocorrelation length of the surface roughness as well as the peak value of the scattering profile. The scatter measurements for the smoothest sample ranged from approximately 3 X 10' per µsr near the specular direction to 10 -13 per µsr at wide angles. For the roughest sample, the range was from 3 X 10-4 per µsr to 10-10 per µsr.
    • DETECTABILITY OF DEGRADED VISUAL SIGNALS: A BASIS FOR EVALUATING IMAGE-RETRIEVAL PROGRAMS

      Wheeler, L.; Daniel, T.; Seeley, G.; Swindell, W. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1971-12)
      We report here the first experiments in a long-range program for investigating the effectiveness of image-retrieval or image-enhancement procedures. We employed a signal-detection mode of observer response, and our stimuli were computer-generated, pointed, abstract forms that we call quadrigons. Four values of signal-to-noise ratio were provided by varying the amount of roundedness of the interior and exterior angles of these forms. Linear blur, grain magnification, and figure-surround contrast ratio were the other independent variables in our factorial design. For each quadrigon, observers gave scaled expressions of confidence that the photographed object was originally pointed (the "signal present" condition). Scores from 12 observers, who were each exposed twice to a set of 500 quadrigons, yielded receiver operating characteristics (ROC functions) that are sensitive, quantitative indicators of the discriminabilities of the stimuli. By this method, also, an observer's criterion state (his degree of willingness to guess that a signal was present) was evaluated and removed as a contaminating factor. Signal-to-noise ratio had a strong and systematic effect upon signal detection accuracy when the effects of all other variables were combined. Linear blur, grain size, and contrast ratio each affected observer performance greatly. All two-way, three-way, and four-way interactions among the independent variables were highly significant; each source of image degradation had differential effects upon every other variable, and combinations of the variables had additional effects. The results are complex, but they provide useful implications for image processing that is designed to enhance information retrieval. We can, for instance, define the effects upon signal detectability when linear blur is reduced by specified amounts, or grain size is reduced, or contrast conditions are improved. We can, moreover, specify certain optimum combinations of values for these variables.
    • UNIFIED APPROACH TO RESTORING DEGRADED IMAGES IN THE PRESENCE OF NOISE

      Hershel, Ronald S. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1971-12)
      The problem of inferring some unknown distribution (object) from measurements of physical quantities (image data) occurs frequently in scientific investigation. This study is concerned with the numerical estimation of a continuous object distribution from a finite set of noisy image data, where the transformation (degradation) between the object and the noiseless portion of the data is assumed known. So defined, the restoration problem is inherently a statistical one, requiring a priori information to define the "most probable" object and noise associated with a given set of data. With a random particle model, the problem of implementing complex statistical and analytical foreknowledge (positive and bounded objects, signal - dependent noise, multiple -stage imaging, spatial correlation, etc.) is reduced to a few simple restoring formulas. For linear problems, noise impedes the ability to restore those object modes (statistically orthogonal components) that have a low power transmission through the imaging process. Linear applications of Fourier transform techniques are dis- cussed, where modifications to the standard Wiener filter are required for under - sampling a bandlimited image. The use of nonlinear object formulas tends to reduce the effects of noise and may extend restored resolution to well beyond the Rayleigh limit. This enhancement occurs in relatively isolated regions in an extended object, where the average restored information can never exceed that in the image. Particular attention is given to developing numerical algorithms for efficient use in digital computers. A positive or bounded object estimate is found through a series of linear matrix solutions, with an example of "superresolving" two impulses separated by half the Rayleigh limit. For 2 -D problems with stationary imaging, a purely iterative algorithm is developed, based on a series of Fourier transform operations. For restoring a 64 X 64 data array with nonlinear constraints, computation time may require only seconds (CDC 6600) as compared with hours using direct matrix methods. The iterative transform method is then applied to experimental absorption spectra, resulting in considerable resolution enhancement. Included are brief discussions of restoring photon -limited images, multiple -stage imaging problems, estimation of the imaging response, use of a finite object extent, the problem of systematic errors, and possible applications of the restoring techniques.
    • PROPERTIES AND APPLICATIONS OF GENERALIZED RAY TRACING

      Parker, Steven C. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1971-11)
      Generalized ray tracing is a method of calculating the principal curvatures and directions of the wavefront associated with a ray as it is traced through an optical system. The results of such a ray trace provide important information about the structure of the image and have immediate application to lens design and image analysis. The caustic surface formed by an optical system can be easily determined from the results of a generalized ray trace. An examination of several caustic surfaces formed by different optical systems provides valuable information about the relative quality of the images and indicates some of the advantages of the generalized ray tracing method.
    • A NEW RETINAL MODEL AND ITS APPLICATION TO THE COMPUTER ANALYSIS OF AERIAL PHOTOGRAPHS

      Sadowski, Alexander M. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1971-10)
      In order to find a new and more economical method for the computer detection of object outlines in aerial photographs, the human visual system is considered. This leads to the concept of the human retina as a matrix of light receptors and permits the development of a three-stage retinal process. The first stage consists of the registering of the intensity distribution of the image. The second and third stages consist of operations that are analogous to the mathematical calculations of the first and second derivatives. This process is applied to the retinal matrix in a line-by-line method in two orthogonal directions. This retinal model is tested experimentally and applied successfully to two photo- graphs. The computer program that generates and performs the retinal three-stage process does so with a minimum of computer decisions, resulting in a highly efficient use of computer time. The successful application of this retinal model and its inherent economy of operation demonstrate its potential usefulness in the computer analysis of aerial photographs.
    • APPLICATION OF ASPHERICS FOR WEIGHT REDUCTION IN SELECTED CATADIOPTRIC LENSES

      Buchroeder, Richard A. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1971-07)
      The history of modern wide -field, high-speed catadioptric lenses is reviewed. One system comprising only spherical curves and representative of the current art for low-light-level systems is evaluated and used as a baseline design in a weight-reduction study. Five aspheric designs are computed and evaluated. It is found that the use of aspherics will permit weight reduction only in certain instances, i.e., if one element of an all-spherical design can be eliminated or if a fundamentally different configuration that is possible only with aspherics is substituted for the all-spherical configuration. Of these possibilities, the elimination of an element is the best replacement for the baseline design. The case of a highly constrained, purely refractive triplet is studied in some detail. Four designs are computed -from the all-spherical case to the most complex polynomial aspheric. It is found that, if only conic aspherics are employed, significant improvement can be obtained and the problems involved are sensibly the same as those in all-spherical designs. When complex aspherics are applied, the problem becomes surprisingly difficult, and there is some indication that a computer can deal with it better than can a human lens designer.
    • Design Examples of Tilted-Component Telescopes (TCT's) (A Class of Unobscured Reflectors)

      Buchroeder, Richard A. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1971-05)
      A tilted component telescope (TCT) is one that features no obstructions in the light path yet is appreciably simpler to build than conventional off -axis instruments. The principles of TCT design are applicable to scanning and image-stabilized optics and should allow improvements in that field. The author has collected and computer-evaluated designs representative of existing art: Schiefspiegler, Yolo, catadioptric Herschelian, and Schupmann. It is expected that these evaluations will enable optical scientists to appraise the merits of the TCT approach and will stimulate the development of second -generation designs.
    • The Physics of Quantum Electronics 1970 A Series of Lecture Notes

      Jacobs, Stephen F. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1971-04)
      This volume is intended to be used as a text for two courses at the Optical Sciences Center. A major part of the volume consists of lecture notes on the theory of laser operation, written by M. O. Scully and M. Sargent III. These notes, developed under NSF sponsorship for a new quantum optics curriculum at the University of Arizona, were the basis of a new course "Quantum Optics," which was first offered during the 1969-70 academic year. After considerable editing they were again used during "The Physics of Quantum Electronics" summer course in Prescott, June 22 - July 3, 1970. The remainder of the volume consists of unpublished work presented at Prescott, most of which will be utilized in a new course on nonlinear optics. References are given to material presented that has already appeared in print.
    • SIGNAL PROCESSING IN THE PRESENCE OF SIGNAL-DEPENDENT NOISE

      Thunen, John G. (Optical Sciences Center, University of Arizona (Tucson, Arizona), 1971-03-15)
      The significance of signal-dependent noise is discussed. Particular emphasis is placed on the type of multiplicative noise present in the density variations in a photographic emulsion. A theoretical treatment of the effect of multiplicative noise on signal detection and signal discrimination problems is presented. Optimum test statistics are derived for processing a sampled message to detect the presence of a known signal. Multiplicative noise described by Poisson and Gaussian statistics is considered. The expressions are extended to include the two-signal discrimination problem. Two-dimensional signal fields in the presence of multiplicative noise are simulated in a computer and processed for optimum signal detection according to the two derived methods. These results are compared to the results of processing based on the assumption of stationary noise statistics. This comparison reveals that modest improvements (20% to 30% reduction in false alarm rate) are obtained when the signal-dependent nature of the noise statistics is considered. The effects of signal-to-noise ratio, signal structure, and changing background level are also investigated. An example of optimum signal discrimination using circles and squares as signals in multiplicative noise is reported. An improvement in the percentage of correctly identified signals is again observed when the proper test statistic is used. Two examples of signal filtering in the presence of signal-dependent noise are included. The first concerns the processing of a real star field to determine the location of weak stars. The second is an illustration of the signal information contained in the noise spectrum of a message recorded on a common photographic film.