Stroke to raster converter system

• US 6,496,160 B1
• Filed: 04/29/1999
• Issued: 12/17/2002
• Est. Priority Date: 04/29/1999
• Status: Expired due to Fees

• Current Assignee: Evans & Sutherland Computer Corp. (Elevate Entertainment, Inc.)
• Original Assignee: Evans & Sutherland Computer Corp. (Elevate Entertainment, Inc.)
• Inventors: Simmons, Calvin L., Tanner, Allen H.
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Tran, Henry N.
• Application Number:
  US09/301,947
• Time in Patent Office: 1,328 Days
• Field of Search: 345/3.1, 345/3.2, 345/10-14, 345/16, 345/17, 345/20, 345/27-29, 345/539, 345/545, 345/530, 348/382, 348/399, 348/413, 348/414, 348/428, 348/440, 348/571, 348/572, 348/805, 348/806
• US Class Current: 345/3.1
• CPC Class Codes: G09G 1/07 with combined raster scan and calligraphic display
• CPC Class Codes: G09G 5/393 Arrangements for updating the contents of the bit-mapped memory
• CPC Class Codes: G09G 5/395 Arrangements specially adapted for transferring the contents of the bit-mapped memory to the screen G09G5/399 takes precedence
• CPC Class Codes: G09G 5/399 using two or more bit-mapped memories, the operations of which are switched in time, e.g. ping-pong buffers

Abstract

An apparatus for converting analog stroke display signals representing electron beam generated stroke traces into raster display information for producing a raster-scan image display. The apparatus includes a sampling circuit for sampling the analog stroke display signals to produce pixel data representing sub-pixel locations covered by the stroke traces. A frame buffer is coupled to the sampling circuit to temporarily store pixel data. A filter is coupled to the frame buffer for calculating brightness of pixels based upon the amount of coverage of the pixels by a stroke trace. In addition, a raster-scan display device is coupled to the filter for receiving the pixel data from the filter to produce a raster-scan image.

Claims

1. Apparatus for converting analog stroke display signals representing electron beam generated stroke traces, into raster display information for producing a raster-scan image display, including:

a sampling circuit for sampling the analog stroke display signals to produce pixel data representing sub-pixel locations covered by the stroke traces;

a frame buffer coupled to the sampling circuit for temporarily storing pixel data;

a filter coupled to the frame buffer for calculating brightness of pixels based upon the amount of coverage of the pixels by a stroke trace; and

a raster-scan display device coupled to the filter for receiving the pixel data from the filter to produce a raster-scan image;

wherein the stroke display signals include an analog X major deflection signal and an analog Y major deflection signal defining respectively the X axis and Y axis end point coordinates of a stroke trace, and wherein said sampling circuit includes an analog-to-digital converter for producing digitized representations of the X and Y major deflection signals, representing sub-pixel locations covered by the stroke trace;

wherein the stroke display signals further include signals further include an analog x character deflection signal and an analog y character deflection signal defining respectively the x axis and y axis coordinates of a character stroke trace as a character is being drawn, and wherein the analog-to-digital converter produces digitized samples (digital representations) of x and y character deflection signals, representing sub-pixels locations covered by the character stroke trace;

wherein the stroke display signals further include a three-level video signal in which a level 0 indicates that the electron beam is to be moved while off, a level 1 indicates that a stroke trace is to be drawn by the electron beam (at a first brightness level), and a level 2 indicates that a character is to be drawn by the electron beam (at a second brightness level), said sampling circuit further including a sample combiner for adding the digitized samples of the X major and x character deflection signals and adding the digitized samples of Y major and y character deflection signals when the video signal is a level 2, and supplying the sums to the frame buffer, for supplying the digitized samples of the X major and Y major deflection signal to the frame buffer when the video signal is a level 1, and for supplying no digitized samples to the frame buffer when the video signal is a level 0.

2. Apparatus as in claim 1 wherein said sampling circuit is adapted to sample each of the X major, Y major, x character, and y character deflection signals at a rate corresponding to at least four samples per pixel in each axis of the pixel data, to thereby produce digital representations of pixels divided into at least four by four arrays of sub-pixels indicating sub-pixel locations covered by the stroke trace.

3. Apparatus as in claim 2 further including a cache memory for receiving and temporarily storing each pixel for supply to the frame buffer.

4. Apparatus as in claim 3 wherein said frame buffer includes two frame buffer memories, one for loading with pixel data while the other is supplying pixel data to the display device, and vice-versa.

5. Apparatus for converting analog stroke display signals representing electron beam generated stroke traces, into raster display information for producing a raster-scan image display, including:

a sampling circuit for sampling the analog stroke display signals to produce pixel data representing sub-pixel locations covered by the stroke traces;

a frame buffer coupled to the sampling circuit for temporarily storing pixel data;

a filter coupled to the frame buffer for calculating brightness of pixels based upon the amount of coverage of the pixels by a stroke trace; and

a raster-scan display device coupled to the filter for receiving the pixel data from the filter to produce a raster-scan image;

wherein the stroke display signals include an analog X major deflection signal and an analog Y major deflection signal defining respectively the X axis and Y axis end point coordinates of a stroke trace, and wherein said sampling circuit includes an analog-to-digital converter for producing digitized representations of the X and Y major deflection signals, representing sub-pixel locations covered by the stroke trace;

wherein the stroke display signals further include a two-level signal in which a level 0 indicates that the electron beam is to be moved while off, and a level 1 indicates that a stroke trace is to be drawn by the electron beam, wherein video signal levels of the digitized samples of the X major and Y major deflection signals are supplied to the frame buffer when the video signal is a level 1, and wherein no video signal level for the digitized samples is supplied to the frame buffer when the video signal is a level 0.

6. Apparatus as in claim 5 wherein said sampling. circuit is adapted to sample the X major, and Y major, deflection signals at a rate corresponding to four samples per pixel in each axis of the pixel data, to thereby produce digital representations of pixels divided into four-by-four arrays of sub-pixels indicating sub-pixel locations covered by the stroke trace.

7. Apparatus as in claim 6 further including a cache memory for receiving and temporarily storing each pixel for supply to the frame buffer.

8. Apparatus as in claim 6 wherein said frame buffer includes two frame buffer memories, one for loading with pixel data while the other is supplying pixel data to the display device, and vice-versa.

9. A method for converting analog stroke display signals representing electron beam generated stroke traces, into raster display information for producing a raster-scan image display, including the steps of:

sampling the analog stroke display signals using a sampling circuit to produce pixel data representing sub-pixel locations covered by the stroke traces,

storing pixel data received from the sampling circuit in a frame buffer,

filtering pixel data received from the frame buffer to calculate brightness of pixels based upon the amount of coverage of the pixels by a stroke trace;

receiving the pixel data from the filter into a raster-scan display device to produce a raster-scan image;

producing digitized samples (digital representations) of analog X and analog Y major deflection signals of strokes display signals, representing pixel locations covered by the stroke trace, wherein the analog X major deflection signal and the analog Y major deflection signal define respectively, the X axis and Y axis end point coordinates of a stroke trace, and wherein said sampling circuit includes an analog-to-digital converter to produce the digitized samples;

producing digitized samples (digital representations) of analog x and analog y character deflection signals of stroke display signals, representing pixel locations covered by a character stroke trace wherein the x and y character deflection signals further define respectively the x axis and y axis coordinates of a character stroke trace as a character is being drawn, and wherein the sampling circuit further includes analog-to-digital converter circuitry to produce the digitized samples;

supplying a three-level video signal along with the stroke display signals in which a level 0 indicates that the electron beam is to be moved while off, a level 1 indicates that a stroke trace is to be drawn by the electron beam (at a first brightness level), and a level 2 indicates that a character is to be drawn by the electron beam (at a second brightness level);

adding the digitized samples of the X major and x character deflection signals is and adding the digitized samples of the Y major and y character deflection signals when the video signal is a level 2, using a sample combiner contained in said sampling circuit; and

supplying the sums to the frame buffer, for supplying the digitized samples of the X major and Y major deflection signals to the frame buffer when the video signal is a level 1, and supplying no digitized samples to the frame buffer when the video signal is a level 0.

10. The method as in claim 9 wherein said sampling circuit is adapted to sample each of the X major, Y major, x character, and y character deflection signals at a rate corresponding to at least four samples per pixel of the pixel data on each axis, to thereby produce digital representations of pixels divided into four-by-four arrays of sub-pixels indicating sub-pixel locations covered by the stroke trace.