Hughes Aircraft Company

Michael D Pruznick

Eugene W Opittek

David J Ketcham

James L Heard

Bruce W Keller

Roger W Lowe

Gerald Wolfson

Thomas A Bosseler

James R Phelps

A symbol smoothing system for synthetically increasing the effective resolution of an in-raster symbol generator memory by a factor of four. The system stores a special three bit code in selected memory elements representative of the existing and past two memory lines with the code actually being a video brightness distribution and positioning offset code. A code number in a single memory cell defines positional and intensity information for the display elements corresponding to that memory cell and to selected surrounding eight memory cells, all of the memory cells having time or positional correspondence to display element positions. The stored codes in the surrounding memory cells, as well as the instantaneous memory cell being decoded, provide intensity levels which are combined at selected display element positions. The video data input for each memory cell consists of the fractional X and Y position bit and symbol type bit and from each memory element, eight additional display elements are developed having selected brightness levels. By decoding this code bit information, the in-raster symbology provides a smooth transition from one display line to the next so as to eliminate the staircase effect in rotated or non-orthogonal lines. For each memory cell in a first field, such as the odd field, every other display resolution element is generated principally from the code in the memory cell and the alternate resolution element is generated principally from the same code. For the other field, such as the even field, the two elements on the display are generated principally from same information code in the memory cell. Further, each resolution element defined by a memory cell can have its intensity increased by codes stored in surrounding memory cells. The three bit memory codes define the location of the imaginary display elements and the video distribution patterns, which patterns simulate a gaussian brightness distribution to temper the edge sharpness of the digitally derived symbology. Thus by storing a single code for each selected memory cell, the system by proper decoding of the codes stored in that memory cell and the surrounding memory cells, develops both positional and intensity display information for the display elements while increasing the effective resolution of the in-raster symbol generator refresh memory by a factor of four. Another feature in accordance with the invention is the use of a common decoding structure by altering the stored codes with a bit rotator so as to be compatible with the common decoding structure, with the altered code representing the correct condition to be decoded.

In-raster symbol smoothing system

A digital scan converter which comprises modular video processing units and modular memory and output units is adapted for processing applied sensor data of various formats so as to provide output data suitable for display on a common indicator. Parameters for processing operations, such as analog-to-digital converting, integrating and detecting, are implemented by the video processing modules in response to digital 'set-up' and address words applied from a programmed microprocessor controller. The storage and readout format of the memory and output modules is also controlled by 'set-up' and address words applied from the programmed controller.

Modular programmable digital scan converter

A raster display system is disclosed which utilizes a 'sliding window' effect for enhancing the contrast of an image by adjusting the video gain and brightness within the window. The television display may have a raster having 512 lines and 512 elements per line. The display system utilizing digital circuitry calculates the average brightness of a 'window' having a predetermined number of elements per display line and several parallel display lines, such as, for example, eight lines and eight elements per line. Thus, an eight-by-eight window is presented. The average brightness of the window is subtracted from the brightness of a centrally located element which results in the relative brightness of the element. This relative brightness signal is multiplied by a gain factor and the product is applied to an output circuit for controlling the bias of a central element of the window. The window is moved one element over and a second computation is made which in turn results in a new bias being set for a second element centrally located within the second window. The window is slid one element at a time and a bias adjustment is made for each centrally located element until all of the elements in the first eight lines have been entered into the computation. The window is then deflected one line down and back to the first eight elements of the second through ninth display lines. The process of sliding the window to the right continues again until all the elements within this second set of sliding windows is completed. Thus, the window slides across the display one element at a time and down one line at a time at the end of each set of lines until all of the elements in the display have entered into the computation.

Television display utilizing local area brightness control

Real time histogram equalization systems for a television type display that performs equalization with one or two dimensional processing on a local area or sliding window basis. For the two dimensional system, the intensity for any particular point in the image is adjusted according to a histogram of the area contained within a window immediately surrounding the point to be equalized. The histogram forming window provided by the system moves across the image in two dimensions both horizontally along each of a plurality of overlapping segments arranged parallel in the vertical dimension, and at each window position reassigned center picture elements are equalized. The processing of the histograms area or the sliding process is continued over the entire surface of the raster with the process being then repeated in a continuous fashion. The area being equalized for each window position may be selected equal horizontally and vertically to the respective amount of shifting along each segment between window positions and of the shifting of the window between adjacent segments. In order to process the histograms at the video rate and resolution the system computes mini or subhistograms from an area formed of a selected number of elements of the histogram in the horizontal dimension by the number of histogram lines in the vertical dimension of the window and sums the statistics of a selected number of the mini histograms to generate one histogram for equalizing the central area. In the continuous process the mini histograms are read out in parallel to form a plurality of histograms and multiple truncation maps which are stored in a selected number of RAM memories. Digital video is then processed through these transformed memories and stored in output buffers which may be required because of the multiplexing. In the system utilizing one dimensional processing, histograms are formed for the data of a selected number of lines in order to equalize the data of a selected line or lines and the histogram window area is moved vertically over the entire raster area.

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Huntington Beach, CA, United States of America

Michael D Pruznick