Showing papers on "Point spread function published in 1970"
TL;DR: Modifications to the system are proposed to give a system that acts as an adaptive filtering system that is less sensitive to the position of the element that must be changed to perform a search for the scale or orientation of the signal, and may reduce the aberrations that are sometimes caused by spatial carrier-frequency functions.
Abstract: Optical data-processing systems that use spatial filters for detecting two-dimensional signals are usually arranged so that the data are placed in a space domain and the signals to be detected are placed in a frequency domain as holographically recorded Fourier transforms. We propose to interchange the roles of the data and the signal by introducing the data into the system as a Fourier transform hologram and by placing the signal in the space plane. Furthermore, the nonlinear behavior of the film used to record the Fourier transform hologram can be used to good advantage. These modifications combine to give a system that (1) acts as an adaptive filtering system because the noise suppression part of the matched filter is based on a specific noise sample rather than on averages of many noise samples, (2) is less sensitive to the position of the element that must be changed to perform a search for the scale or orientation of the signal, and (3) may reduce the aberrations that are sometimes caused by spatial carrier-frequency functions. Experimental results support the theoretical conclusions.
56 citations
TL;DR: The description of a machine that performs a variety of image processing operations is given, together with a theoretical discussion of its operation.
Abstract: The description of a machine that performs a variety of image processing operations is given, together with a theoretical discussion of its operation. Spatial processing is performed by corrective convolution techniques. Density processing is achieved by means of an electrical transfer function generator included in the video circuit. Examples of images processed for removal of image motion blur, defocus, and atmospheric seeing blur are shown.
46 citations
TL;DR: Photographic film imagery, degraded by long-term artificial atmospheric turbulence, has been restored by spatial filters placed in the Fourier transform plane by using the simple inverse filter and the optimum least-mean-square filters.
Abstract: The results of optimum filtering from communications theory have been applied to an image restoration problem. Photographic film imagery, degraded by long-term artificial atmospheric turbulence, has been restored by spatial filters placed in the Fourier transform plane. The time-averaged point spread function was measured and used in designing the filters. Both the simple inverse filter and the optimum least-mean-square filters were used in the restoration experiments. The superiority of the latter is conclusively demonstrated. An optical analog processor was used for the restoration.
37 citations
TL;DR: In this paper, a lower bound for the mean-square error of an unbiased estimate of a parameter of an incoherently radiating object observed in the presence of thermal background light by an optical system collecting light through a finite aperture was derived.
Abstract: By means of the quantum-mechanical form of the Cramer-Rao inequality, a lower bound is set to the mean-square error in an unbiased estimate of a parameter of an incoherently radiating object observed in the presence of thermal background light by an optical system collecting light through a finite aperture. Estimates of absolute radiance, frequency, and position of the object are specifically analyzed. The bounds reduce in the classical limit to those previously obtained, but are valid in the quantum limit as well. When the background vanishes, the bounds depend only weakly on the effective number of independent spatial and temporal degrees of freedom of the object light at the aperture.
22 citations
TL;DR: The quantity C out / σC out, as a measure of the signal-to-noise ratio of the system, takes into account all the basic nonsubjective parameters that govern contrast perception and the term Contrast Perceptibility Function is proposed for its variation with spatial frequency.
6 citations
TL;DR: In this paper, the mutual information between the radiance of an incoherently radiating object plane and the field at the aperture of an observing system is calculated on a classical basis.
Abstract: The mutual information between the radiance of an incoherently radiating object plane and the field at the aperture of an observing system is calculated on a classical basis. A formula of the Shannon type is obtained when the time–bandwidth product of the object light is large, the average radiance from the object plane is small enough to permit the threshold approximation, and the radiance of the object plane is modeled as a spatial gaussian process. It includes the dependence on the bandwidth of the object light and the effective temperature of the background, assumed spatially and temporally white. A set of sufficient statistics for the aperture field, based on Fourier sampling of the object plane, is introduced, and its bearing on the resolution of fine details of the object is brought out.
1 citations