Showing papers on "Point spread function published in 1972"
TL;DR: A communication-theory model for the process of image formation is used and it is found that the most likely object has a maximum entropy and is represented by a restoring formula that is positive and not band limited.
Abstract: Given M sampled image values of an incoherent object, what can be deduced as the most likely object? Using a communication-theory model for the process of image formation, we find that the most likely object has a maximum entropy and is represented by a restoring formula that is positive and not band limited. The derivation is an adaptation to optics of a formulation by Jaynes for unbiased estimates of positive probability functions. The restoring formula is tested, via computer simulation, upon noisy images of objects consisting of random impulses. These are found to be well restored, with resolution often exceeding the Rayleigh limit and with a complete absence of spurious detail. The proviso is that the noise in each image input must not exceed about 40% of the signal image. The restoring method is applied to experimental data consisting of line spectra. Results are consistent with those of the computer simulations.
673 citations
TL;DR: In this article, the authors describe a technique by which a large variation phase object may be visualized in an image having an irradiance which is directly proportional to the object phase, where an image of the phase object derivative is formed in a coherent optical system and recorded on photographic film.
Abstract: This paper describes a technique by which a large variation phase object may be visualized in an image having an irradiance which is directly proportional to the object phase. An image of the phase object derivative is formed in a coherent optical system and recorded on photographic film. This photograph is used as the input to a second coherent optical system, in which the image is an integral of the input. No limitations are imposed on the maximum object phase, only on its maximum slope. Experimental techniques for implementation of this system are discussed and results shown.
60 citations
TL;DR: In this paper, it was shown that double and triple slits with separations equal to fractions (0.33, 0.50, or 0.65) of Rayleigh's resolution distance can be resolved subject to a hierarchy of confidence: most accurately restored is the number of object impulses, next are their positions, and least accurate is information on their amplitudes.
Abstract: Can photographic images, e.g., corresponding to star clusters, be superresolved? Or alternatively, can already good (diffraction-limited) images be improved by restoring methods? To test this hypothesis, objects have been prepared that can be resolved only if the bandwidth in the restoration exceeds that of the image data. The objects are double and triple slits with separations equal to fractions (0.33, 0.50, or 0.65) of Rayleigh’s resolution distance. These are incoherently imaged in quasimonochromatic light by a slit-aperture optical system, and developed as photographs. The amount of diffraction blur is made comparable with the grain-limited resolution distance, since this is the usual situation for an efficient optics–film design. The photos are scanned across the slit directions, digitized, and computer restored by the method of maximum entropy. Results indicate that two object slits can be well resolved when separated by one-half of Rayleigh’s resolution distance, and that three object slits are resolvable subject to a definite hierarchy of confidence: Most accurately restored is the number of object impulses, next are their positions, and least accurate is information on their amplitudes.
41 citations
TL;DR: In this paper, a class of filters is developed for minimizing the first term in the moment expansion of the error, and the resulting spread functions have high attenuation rate, negligible side lobes, and are optimum for imaging smooth objects.
Abstract: The distortion of the image of an object, produced by diffraction, can be reduced by filtering. A class of filters is developed for minimizing the first term in the moment expansion of the error. The resulting spread functions have high attenuation rate, negligible side lobes, and are optimum for imaging smooth objects. One- and two-dimensional systems are considered; the analysis includes coherent and incoherent illumination.
30 citations
TL;DR: The image restoration problem in a linear imaging system is formulated as the problem of minimizing the effective radius of the system point spread function subject to a constraint on relative noise gain by reducing the imaging system under consideration to an equivalent sampled system and subsequently optimizing the sampled system by algebraic techniques.
16 citations
TL;DR: In this paper, the angular subtense of the feature at the eye by increase of eyepiece magnification, while decreasing the field of view and luminance, can serve to make visual detection more secure by ensuring that the spatial characteristics of the target match those for which visual contrast sensitivity is highest.
Abstract: The performance of a given microscope arrangement is usually specified in terms of its resolution limit, in practice the radius of the Airy disk. Merely ensuring that the angular subtense of the objective’s Airy disk is brought by the eyepiece near the resolution limit of the eye does not mean that the performance of the eye–microscope system has been optimized. Targets near the resolution limit of the objective will produce luminance distributions in the image that are of the order of size of the Airy disk but of low contrast. Such targets, as well as larger targets of low contrast, will be detectable with the eye only if the visual contrast threshold is exceeded. The latter is highly dependent on the visual angle and increases sharply in the vicinity of the resolution threshold of the eye. Increasing the angular subtense of the feature at the eye by increase of eyepiece magnification, while decreasing the field of view and luminance, can serve to make visual detection more secure by ensuring that the spatial characteristics of the target match those for which visual contrast sensitivity is highest. Numerical aspects of this phenomenon are considered.
11 citations
01 Jan 1972
TL;DR: The system is designed as a flexible research tool to evaluate several techniques of obtaining and reconstructing acoustic holograms, and to determine the fundamental limitations to the performance of holographic acoustic imaging systems.
Abstract: An experimental holographic acoustic imaging System for Evaluation and Simulation (SES) has been designed and constructed. The system sensor is a 400 element hydrophone array. Holographic amplitude and phase data are recorded digitally and photographically. The system is designed as a flexible research tool used to evaluate several techniques of obtaining and reconstructing acoustic holograms, and to determine the fundamental limitations to the performance of holographic acoustic imaging systems. The predicted performance capabilities are given and the signal processing techniques and performance parameters to be investigated are described.
5 citations
01 Jun 1972
TL;DR: In this article, a coded point spread function was proposed to obtain increased resolution and reduced ex-prime time for medical X-ray and gamma ray images, but it requires a post-detection processing step in order to decode the data and obtain the desired image.
Abstract: Recent work has stimulated considerable interest in using radar pulse compression concepts to improve the quality of medical X-ray and gamma ray photographs. (Refs. 1 and 2) These techniques involve using a coded point spread function to obtain increased resolution and reduced ex posure time. The coded point spread function allows use of a larger aperture in the X-ray camera, but requires a post-detection processing step in order to decode the data and obtain the desired image. The point spread function must be coded in such a anner that its two-dimensional autocorrelation function is very sharply peaked. In the post-detection pro cessing; the coded data are cross-correlated with the chosen point spread function to obtain the desired image.
4 citations
TL;DR: In this article, a defocused optical system with a circular diaphragm and illuminated by partially coherent light is studied in context of the theory developed by Wolf, and it is shown that images with aberrations are improved with the help of aberration-compensating amplitude filters.
Abstract: The far-field irradiance distribution of a defocused optical system with a circular diaphragm and illuminated by partially coherent light is studied in context of the theory developed by Wolf. It is shown that images with aberrations are improved with the help of aberration-compensating amplitude filters. The values of the coefficient of defocusing that satisfy the Strehl criterion are given for various values of correlation intervals contained in the aperture.
3 citations