Anti-aliasing raster scan display system

• US 4,843,380 A
• Filed: 07/13/1987
• Issued: 06/27/1989
• Est. Priority Date: 07/13/1987
• Status: Expired due to Fees

• Current Assignee: Nihon Unisys Limited
• Original Assignee: Megatek Corp (HP Inc.)
• Inventors: Parsons, Donald I., Oakley, David
• Primary Examiner(s): Brigance, Gerald L.
• Assistant Examiner(s): Hjerpe, Richard
• Application Number:
  US07/072,757
• Time in Patent Office: 715 Days
• Field of Search: 340/703, 340/723, 340/724, 340/728, 340/727, 340/731, 340/747, 382/49
• US Class Current: 345/615
• CPC Class Codes: G09G 1/285 Interfacing with colour displays, e.g. TV receiver
• CPC Class Codes: G09G 5/20 Function-generator circuits, e.g. circle generators line or curve smoothing circuits
• CPC Class Codes: G09G 5/391 Resolution modifying circuits, e.g. variable screen formats

Abstract

A raster scan display system for eliminating jagged edges from vectors or polygon boundaries inclined within ±45 degrees to horizontal comprising a digital vector generator, a frame buffer memory, a color look-up table, digital-to-analog converters and convolvers placed in front of each digital-to-analog converter for each video output stage of the color look-up table. Fractional address data are appended to each pixel written into the frame-buffer memory to specify the true location of the pixel more accurately. Intensity data for each of the colors assigned thereto by the color look-up table are convolved with a kernel that is selected by the Y fractional address. The convolvers also process the X fractional address which controls the boundaries between pixels on a scan line. Fractional address data read out of the frame-buffer controls the kernels in the convolvers to render the positioning of pixels at four times the addressability of the frame-buffer. Each pixel is micropositioned to an accuracy that is approximately one quarter of the CRT spot diameter. The convolvers double the number of displayed lines, allow for a very rapid rendition of the displayed image, and operate at the troughput of the graphics display system. Memory size is also reduced and image quality greatly enhanced.

Claims

1. In combination with a raster-scan display system in which the path of a writing beam over an array of a displayed image forming pixels is controlled by means of a analog cartesian deflection signals, a video signal processor for smoothing oblique and circular lines, which comprises:

a digital vector generator for generating digital data corresponding to vector locations defined by a display list, including intensity data and fractional address data respectively comprising a set of additional bits of precision corresponding to a first axis of displacement and a set of additional bits of precision corresponding to a second axis of displacement for each pixel;

a frame buffer memory for storing said digital data, including said intensity data and fractional address data;

means for assigning a plurality of fundamental colors to said intensity data;

means for convolving said intensity data with at least one kernel comprising weights function of a state controlled by the fractional addresses corresponding to said second axis of displacement, designed to transform said intensity data from one resolution in said frame-buffer memory to a different resolution in the displayed image, said means for convolving said intensity data further convolving said fractional address data corresponding to said first axis of displacement with said kernel in said state, said means for convolving said intensity data being also designed to determine boundaries between said pixels as a function of said fractional addresses corresponding to said first axis of displacement, on either side of said boundaries, said means for convolving said intensity data being related to the outputs of said means for assigning fundamental colors, wherein each of said means for convolving said intensity data for each of said axes of displacement further includes;

first means for delaying by one line period said digital data;

means for weighting said digital data delayed by said first means for delaying; and

means for summing said digital data after said data have been weighted by said means for weighting; and

wherein said means for convolving said intensity data for said first axis of displacement further comprises second means for delaying by one line period digital data corresponding to said first axis of displacement and for separating said data in left output data associated with the left boundary between said pixels and right output data associated with the right boundary between said pixels;

means for gamma correcting the outputs of each of said means for convolving said intensity data, said means for gamma correcting being related to the output of each of said means for convolving said intensity data;

a plurality of digital-to-analog converting means, each of which is placed at the output of each of said means for gamma correcting, for generating said analog deflection signals corresponding to each fundamental color signal in frame of said raster scan display system; and

means for synchronizing and timing, said means being connected to the input of said digital-to-analog converting means.

2. The video signal processor of claim 1, wherein said means for convolving said intensity data for said axis of displacement further comprises decoding means for calculating the boundary location between said pixels using said right and left output data.

3. The video signal processor of claim 2, wherein said decoding means comprise a collision ROM.