Showing papers on "Image processing published in 1968"

Restoration, Resolution, and Noise

Abstract: This paper treats the problem of restoring the detail to an optical image which has been degraded by diffraction and noise. The particular contribution of the paper is a more complete analysis of the effects of various types of noise on system performance than has been given previously. Background noise, measurement noise, and computer roundoff error are considered, and the errors in the reconstructed image caused by these noise processes are evaluated. Numerical results for the special case of a perfect one-dimensional slit aperture are obtained. A general conclusion is that the reconstruction technique described here is most useful when the smoothing is severe and when a modest improvement of resolution may be worthwhile.

Single-Sideband Holography*

Abstract: In making in-line holograms of amplitude objects with a strong background, the single-sideband technique can be used to improve the quality of the reconstruction. The main advantage of this method is the suppression of the twin image. Modifications of the same technique are also presented for making holograms of complex objects and objects with a weak background.

Computer generated spatial filters for coherent optical data processiing.

Abstract: The setup used in many optical data processing schemes is a coherent optical image forming system. The most important lement in this setup is the complex spatial filter. It can perform a large variety of linear operations upon the object or input. In general, it is difficult to produce complex filters, since both amplitude transmission and phase delay may vary across the filter plane in a complicated manner. Our own filters which are very similar to binary holograms, consist of many little transparent rectangles on opaque background. They can easily be drawn on a large scale by a computer-guided plotter, and then photographically reduced in size. We show that our filters, despite containing only amplitude values zero and one, can perform any data processing operation which could be performed by any complex filter. After explaining the principle, we present three groups of applications. First, we describe new versions of some classical methods: schlieren observation and phase contrast. Next, we report on spatial which perform differential operations upon the object in order to enhance gradients or corners. Finally, we use our binary filters for signal detection.

Image processing and pattern recognition.

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Multiple imaging by means of point holograms.

Abstract: Multiple imaging devices are capable of producing simultaneously a number of images of one object. Several methods have been suggested to realize such an optical system. They make use of the imaging properties of a fly's-eye lens or of an array of pinholes, or they utilize birefringence. More recently, multiple image generation has been achieved by forming the convolution of the object with an array of δ functions in an ordinary spatial filtering arrangement. The complex filter is realized by the Fourier transform hologram of the cor­ responding array of point sources. The second Fourier trans­ form lens, however, has to transmit more than twice the full information of the multiplied image array. Since the most im­ portant application of multiple imaging is semiconductor device fabrication as has been discussed earlier, the resolving power has to be very high, so that up to now no lenses are available that are capable of imaging the multiple array of images of a usual etching mask. I t is for this reason that to date, images of etching masks are transferred to the semiconductor wafer by contact printing. In this communication, we propose to use an arrangement dif­ ferent from that in Ref. 4, such that the multiplied images do not have to be transmitted by any additional optical component. Par t of this communication has already been mentioned in a paper presented at a holography meeting organized by the Battelle Institute at Frankfurt /M, Germany, on 2 December 1967. The principle of operation is illustrated by Fig. 1. The hologram of the array of point sources is produced in the usual way by recording the interference pattern caused by coherent superposition of the spherical waves emanating from the ref­ erence point and the signal points the spatial positions of which correspond to the desired positions of the images to be formed. Multiple imaging is then performed in the reconstruction process by replacing the reference point source by the real image to be multiplied. This can be achieved in the well-known way by means of a lens that images the object through the hologram into the surrounding of the reference point. In this case, an additional real image of the object is formed in the surrounding of each signal point. The behavior of the hologram can be easily understood by thinking of a point hologram as of a generalized Fresnel zone plate with its well-known lenslike properties. Indeed, this hologram of the distribution of point sources may be considered as some special kind of a fly's-eye lens, in which the lenses are replaced by Fresnel zone plates. But there is a rather important difference. Contrary to lenses, the single point holograms may overlap completely without disturbing each other. For this reason, the aperture of each point hologram determining the diffraction limited size of the image point can be made equal to the aperture of the hologram of the whole point distribution provided that suitable spherical waves are used in the recording process. There is no relationship between the diameter of this aperture and the distances of the images to be formed. Limitations to the resolution of this multiple imaging device are mainly introduced by aberrations. In the special case of small plane objects, which are of dominant interest in semicon-

3-D computer-generated movies using a varifocal mirror.

Abstract: An application of varifocal mirror autostereoscopic imaging to 3-D computer-generated movies is described. A high speed movie projector and oscillating varifocal mirror project moving autostereoscopic images at 15 volumetric images per second. In order to distribute evenly the component images along the depth axis, linear time scans of the image volume are required. However, the image position is a nonlinear function of the mirror displacement, which, in turn, has a nonlinear frequency response to the mirror driving voltage. Analytical and experimental investigations are reported in which approximately linear scans for duty cycles approaching 90% were attained.

Superimposed dynamic television display system

Abstract: A visual display system for superimposing linear visual images upon a dynamic television image. System covers the use of at least two television cameras or one camera and a source of electronic background video images such as a video tape recorder, or one scene camera used in conjunction with a double-ended scan converter. One camera or the converter picks up the image from a storage device which in turn is actuated by a signal generator, said image being superimposed on the background video image.

Evaluation of a Television Image Processing System

Abstract: An image processing device using television and a scanning contrast enhancer has been evaluated by study of error rates of 13 observers viewing a standard series of chest x-rays A technique for creating artificial lesions which simulate parenchymal masses was developed, allowing known densities to be put in known locations in otherwise normal chest x-rays Detection was chosen as the criterion of performance An image processor can be considered useful if percentage error is decreased Observers were shown a series of 54 chest x-rays on a conventional viewbox and on the television monitors of the image processor A statistical comparison of error rates was used to evaluate the system The results show that the unprocessed television display degraded performance considerably The addition of contrast enhancement improved error rates but direct viewing was still superior to image processing A detailed study of error distribution showed that, using image processing, observers made considerably poorer judgments on lesions in the lower chest areas than in the upper In the upper areas there was a trend toward lower error rates with image processing than with direct viewing although a statistically significant difference could not be demonstrated The possible reasons for the error rate variations are discussed

Optimum, non-linear processing of noisy images

Abstract: It has been traditional to constrain image processing to linear operations upon the image. This is a realistic limitation of analog processing. In this paper, we find the optimum restoration of a noisy image by the criterion that expectation 〈 ∣Oj-O¯j∣K〉 be a minimum. Subscript j denotes the spatial frequency ωj at which the unknown object spectrum O¯ is to be restored, O¯ denotes the optimum restoration by this criterion, and K is any positive number at the user’s discretion. In general, such processing is nonlinear and requires the use of an electronic computer. Processor O¯ uses the presence of known, Markov-image statistics to enhance the restoration quality and permits the image-forming phenomenon to obey an arbitrary law Ij = ℒ(τj, Oj, Nj). Here, τj denotes the intrinsic system characteristic (usually the optical transfer function), and Nj represents a noise function. When restored values O¯ j, j=1, 2, ⋯, are used as inputs to the band-unlimited restoration procedure (derived in a previous paper), the latter is optimized for the presence of noise. The optimum O¯ j is found to be the root of a finite polynomial. When the particular value K=2 is used, the root O¯ j is known analytically. Particular restorations O¯ j are found for the case of additive, independent, gaussian detection noise and a white object region. These restorations are graphically compared with that due to conventional, linear processing.

Image processing by digital systems.

Abstract: TV picture storing, processing and displaying technique by digital computer to aid photointerpreter in diagnosing image

A Visual Image Processor

Abstract: —A computer, the Visual Image Processor, is described which is designed to process visual images. Images are read by a vidicon camera and stored in any of three identical cathode-ray electrostatic storage tubes. Two storage systems are read simultaneously, with the reading beams spatially displaced from each other, and a signal which is a function of the reading signals is written into the third storage system. The spatial displacement of the reading beams and the function are variable and under control of the computer operator.

An Electro-Optical Search And Visibility Enhancement Technique

Abstract: A technique for performing image processing in real time on normally illuminated scenes--and its potential applications to underwater search and visibility improvement--are described. The Cybercon, a system embodying this technique, is currently undergoing terrestrial tests for the U. S. Army. The system consists of an electro-optical sensor under programmed electronic control. Image processing is performed in a special camera tube. Results are visible to the operator at the phosphor viewing screen of the unit, or may be transmitted to a remote display. Tests on simulated backscatter penetration have been performed, and are illustrated in the paper. This is accomplished by high-pass filtering of the visual image. A 2:1 increase in visibility range is estimated. For underwater search applications, the Cybercon sensor may be programmed to detect the particular shape or spectral characteristic desired. An example of this type of shape detection performed on underwater photography is presented. Automatic monitoring for motion or changes within the scene, together with visibility improvement, can be performed by this sensor used as a processor. Terrestrial examples of this type of application are presented.© (1968) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Graphical data processing

Abstract: There is a need for faster and more efficient production of high quality graphic images. Since the information in graphic images can be coded into data bits, we should be able to adapt the techniques of high speed electronic data processing to graphic image processing. Accordingly, we have constructed an experimental graphic data processor. Its design is based on the same logical design principles as an electronic data processor, but we have modified the system to accommodate the special features needed for processing graphical data. We will describe here our approach to the design, present some details of the system, and show some of the processed images. We will begin with a short discussion of how graphic data is reproduced today, outline some of the advantages of automating the process, and then talk about our own experience.

Image Processing With Multiaperture Image Dissector

Abstract: The multi-aperture image dissector has the ability to give simultaneous information on the brightness of spatially separated points of an optical image, due to the multiplicity of dissecting apertures. Several applications for this multiple readout concept have been proposed and demonstrated. Details of systems for edge detection, tracking and use in photogrammetry, incorporating the multi-aperture image dissector, will be given. Possible motion detection and shape recognition schemes will be outlined. A low light level development of the multi-aperture image dissector will be discussed.

An on-line image processing system

Abstract: The high-speed digital computer has contributed to significant progress in the field of optics. One particular area of optics benefiting from this progress is image processing. The purpose of image processing is to aid the human observer in extracting from an image information which has been obscured by some type of degradation The numerous factors which can degrade the quality of an image in an optical system include lens aberrations, poor focus, image motion, turbulence, and diffraction. In general, the problem of obtaining good images in an optical system should be approached by minimizing these factors by careful design and by control of conditions during recording of the image, usually on photographic film. However, there are times when all factors cannot be controlled sufficiently so that the recorded image lacks the required detail for a given application. In the past little could be done in the way of improving the image once it had been recorded. Now, recently developed processing techniques allow the image to be improved after it is recorded. Although there are several different methods by which these improvements can be made, one of the most powerful and flexible utilizes the digital computer. The purpose of this paper is to describe the basic method of processing, the difficulties facing the image processor working on practical problems, and a unique image processing system devised to overcome these difficulties.

Development of an on-line image processing system for the linc

Abstract: : The development of an on-line image processing system for the LINC computer is described with both hardware and software details being considered. The purpose of the system is to operate on various types of optical images endeavoring to process them so that a maximum amount of useful information is retrieved for final interpretation by the observer. Besides other processing techniques, contrast enhancement and subtraction have been implemented into the system to achieve this purpose. A mathematical model of the system is investigated and equations describing its capabilities are derived. Results showing several pictures before and after processing as well as data verifying the mathematical model are also presented.

The role of optics in information processing.

Abstract: The variety of ways in which optical techniques are now being applied to information processing problems will be reviewed and compared. Information to be processed is sometimes in optical or image form, i.e., image processing; in this case, optics is essential, at least for the input/output phase. Emphasis is placed on the problems of information storage by optical and photographic means. Also, optics has been used to good advantage for certain analog processing problems.