Method and apparatus for digital scan conversion

• US 3,893,075 A
• Filed: 12/29/1972
• Issued: 07/01/1975
• Est. Priority Date: 12/29/1972
• Status: Expired due to Term

• Current Assignee: Horace J. Enea, Richard Orban, Stephen C. Terry
• Original Assignee: Horace J. Enea, Richard Orban, Stephen C. Terry
• Inventors: Orban, Richard, Terry, Stephen C., Enea, Horace J.
• Primary Examiner(s): Zache, Raulfe B.
• Assistant Examiner(s): Rhoads, Jan E.
• Application Number:
  US05/319,217
• Time in Patent Office: 914 Days
• Field of Search: 340/172.5,324AD
• US Class Current: 345/443
• CPC Class Codes: G09G 5/42 characterised by the display of patterns using a display memory without fixed position correspondence between the display memory contents and the display position on the screen

Abstract

A hardware system for converting digital graphical line information into a form suitable for display on a raster-scan output device is provided. Each graphical line is encoded and stored in a memory device. Each encoded graphical line is read prior to each scan of the raster-scan output device. The intersections of each graphical line with each scan line are determined on a line-by-line basis and the raster-scan output device is activated and de-activated accordingly in order to reconstruct all of the vectors.

Claims

1. A digital scan conversion system for displaying on a raster scan output device an arbitrary graphical pattern, wherein said pattern comprises one or more vectors and wherein each vector is defined by graphical line data, comprising:

a. means for receiving digitally-coded graphical line information for each vector forming said arbitrary graphical pattern;

b. processing means responsive to said receiving means for determining at least graphical line boundary data for each vector and determining a vector storage word which uniquely defines each vector of said arbitrary graphical pattern, said processing means additionally including c. means for storing said vector storage word for each vector;

d. means for accessing said vector storage words from said storing means so that the vector storage word for each vector is accessed at least once during each scan of said raster-scan output device;

e. first means responsive to said accessing means for determining for each vector forming the pattern, the intersection scan-line segments for each scan of said output device intersected by each of said vectors required to synthesize each vector of the pattern;

f. second means responsive to said vector storage words provided by said accessing means and to said intersection scan-line segments provided by said first means for determining for each scan of the raster scan output device the composite of all of the intersection scan-line segments which must be displayed during that scan and storing said composite; and

g. means responsive to said second determining means for activating and de-activating said raster-scan output device according to the stored composite of all of the intersection scan lines during each scan thereof.

2. A digital scan conversion system as in claim 1 wherein said digitally-coded graphical line information is sent from a computer.

3. A digital scan conversion system as in claim 1 wherein said digitally-coded graphical line information is received over a high band-width data transmission line.

4. A digital scan conversion system as in claim 1 wherein said raster-scan output device is a conventionally scanned television monitor.

5. A digital scan conversion system as in claim 1 wherein said raster-scan output device is an electro-static printer.

6. A digital scan conversion system as in claim 1 wherein said storage and accessing means comprising a recirculating storage device.

7. A digital scan conversion system as in claim 1 wherein said vectors are all straight line vectors arbitrary as to both length, position and orientation, and said intersection scan-line segments are the same for each straight-line vector for each intersected scan of said raster-scan output device.

8. A digital scan conversion system as in claim 7 wherein for each straight-line vector said intersection scan-line segment data is stored with the vecta storage word in said storage means.

9. A digital scan conversion system as in claim 8 wherein said vector storage word for each straight-line vector is stored in an order from the straight-line vector having the longest intersection scan-line segment to the straight-line vector having the shortest intersection scan-line segment.

10. A digital scan conversion system as in claim 9 wherein said second means comprises at least a pair of random access memory devices;

and wherein each of said random access memory devices receives and stores intersection scan-line data for all straight-line vectors intersecting one scan line of said output device, the order of said scan-line data being arranged to coincide with the scan sequence, and wherein each one of said pair alternately and sequentially stores said intersection scan-line data.

11. A digital scan conversion system as in claim 10 wherein each of said random access memory devices comprises first and second display registers, said first display register storing the begiNning points of each intersection scan-line segment for a scan-line and said second display register storing the end points for each intersection scan-line segment for a scan line.

12. A digital scan conversion system as in claim 11 wherein said activating and deactivating means comprises means responsive to said first display register for activating said output device and means responsive to said second register for deactivating said output device.

13. A digital scan conversion system as in claim 10 wherein said activating and deactivating means comprises means for alternately reading each of said random access memory devices and activating and deactivating said output device in accordance with the intersection scan-line data stored in each.

14. A digital scan conversion system as in claim 1 wherein said first means is operable to determine said intersection scan-line segments while the preceding scan-line composite is being provided as input to said raster-scan output device.

15. A digital scan line conversion system as in claim 10 wherein one of said pair of said random access memory devices stores said intersection scan-line segments while the other of said pair is being read by said activating and deactivating means.

16. A digital scan conversion system as in claim 1 including means for adding to and deleting from said storage means the vector storage words for selected individual vectors concurrent with the operation of the digital scan conversion system.

17. A system for displaying graphical information in the form of patterns of straight line vectors on a conventional raster-scan cathode ray tube television monitor, said graphical information being provided from a computer to said display system in the form of binary-coded Cartesian coordinates identifying each vector comprising:

a. first means for determining for each vector comprising the pattern the incremental length that the beam of said cathode ray tube must be provided during those horizontal sweeps of said cathode ray tube beam necessary to reconstruct the vector;

b. first storage means responsive to said first means for storing vector identification information for each vector comprising the pattern;

said information comprising at least said incremental lengths;

c. said first storage means including accessing means being capable of referencing each vector identification information at least once during each horizontal scan period;

d. second means responsive to said vector identification information provided by said accessing means for determining for each horizontal scan of said cathode ray tube horizontal scan information comprising the location of said incremental lengths for all vectors which intersect that horizontal scan line and including second storage means for storing said horizontal scan information; and

e. means for accessing said second storage means for activating and de-activating said cathode ray tube beam according to said stored horizontal scan information during each horizontal sweep thereof

18. A system as in claim 17 wherein said storing means comprises a rotating storage device.

19. A system as in claim 17 wherein said storing means comprises a shift register.

20. A system as in claim 19 wherein said shift register has at least M by N storage capacity;

where M corresponds to the maximum number of vectors which can be displayed, and N corresponds to minimum number of bits necessary to store said vector identification information.

21. A system as in claim 19 wherein the cycle rate of said shift register is at least as great as the horizontal scan rate of said cathode ray tube.

22. A system as in claim 17 wherein said second storage means includes first and second storage devices, said storage devices first storing horizontal scan information for the next succeeding horizontal scan and secondly providing horizontal scan information to said activating and deactivating means for the current horizontal scan being displaYed on said cathode ray tube, and wherein said first storage device is storing said horizontal scan information while said second provides said information, and at the completion thereof, said first storage device provides said information while said second storage device is storing said scan information.

23. A system as in claim 22 wherein the access speed of said first and second storage devices is sufficiently great to enable all of said horizontal scan information to be stored and read during one horizontal scan period.

24. A system as in claim 22 wherein each of said first and second storage devices comprises a turn-on and turn-off storage device, said turn-on storage device storing information corresponding to the beginning points of said incremental lengths in a horizontal scan line and said turn-off storage device storing information corresponding to the endpoints of said incremental lengths, said activating and deactivating means being responsive to the information stored in said turn-on storage device to activate said cathode ray tube beam and being responsive to the information in said turn-off storage device to deactivate said cathode ray tube beam.

25. A system as in claim 24 wherein said turn-on and turn-off storage devices each comprise a random access memory device.

26. A system as in claim 17 wherein said second means is operable to determine said horizontal scan information for a scan line while the preceding scan-line is being outputed on said television monitor.

27. A system as in claim 17 including means for insuring registration of vectors displayed on said television monitor at the beginning of each new video field.

28. A system as in claim 1 wherein said activating and de-activating means includes an up-down counter, said counter being counted up by bits located in said turn-on storage device and counted down by bits located in said turn-off storage device;

and wherein said cathode ray tube beam is provided whenever the output of said counter is greater than zero.

29. A system as in claim 28 wherein said beginning and said end points of said incremental lengths are stored in said turn-on and turn-off storage devices, respectively, only if no bits have previously been stored in either of those locations in said turn-on and turn-off storage devices.

30. A system as in claim 17 wherein said vector identification information is stored in an order from the vector having the largest incremental length to the vector having the smallest incremental length.

31. A system as in claim 29 wherein said activating and de-activating means includes a single pulse-providing circuit, and wherein said circuit is activated to provide a single point display on said television monitor whenever said turn-on and turn-off storage devices have bits stored at the same relative locations.

32. A system as in claim 17 including means for adding to and deleting from said first storage means vector identification information for selected individual vectors concurrent with the display of graphical information.

33. A scan conversion system for displaying graphical information in the form of patterns of straight line vectors on a raster-scan output device, said graphical information being provided from a computer to said scan conversion system in the form of binary coded Cartesian coordinates identifying each vector comprising:

a. first means for determining for each vector comprising the pattern the incremental length for each scan of said output device for those scans necessary to synthesize the vector;

b. first storage means responsive to said first means for storing vector identification information for each vector comprising the pattern, said information comprising at least said incremental length;

c. said first storage means including accessing means for referencing each vector identification information at least once during each scan of said output device;

d. second means responsive to said vector identification information pRovided by said accessing means for determining for each scan of said output device scan information comprising the location of said incremental lengths for all vectors which intersect that scan line and including second storage means for storing said information; and

e. means for accessing said second storage means for altering the intensity of the output device scan according to said stored scan information.

34. A system as in claim 33 wherein said first storage means comprises a rotating storage device.

35. A system as claim 33 wherein said first storage means comprises a shift register.

36. A system as in claim 35 wherein said shift register has at least M by N storage capacity;

where M corresponds to the maximum number of vectors which can be displayed, and N corresponds to the minimum number of bits necessary to store said vector identification information.

37. A system as in claim 35 wherein the cycle rate of said shift register is at least as great as the scan rate of said raster-scan output device.

38. A system as in claim 33 wherein said second storage means includes first and second storage devices, said storage devices first storing scan information for the next succeeding scan and secondly providing scan information to said activating and deactivating means for the current scan being displayed on said raster-scan output device and wherein said first storage device is storing said scan information while said second provides said information, and at the completion thereof, said first storage device provides said information while said second storage device is storing said scan information.

39. A system as in claim 38 wherein each of said first and second storage devices comprises a turn-on and a turn-off storage device, said turn-on storage device storing information corresponding to the beginning points of said incremental lengths in a scan line and said turn-off storage device storing information corresponding to the endpoints of said incremental lengths, said activating and de-activating means being responsive to the information stored in said turn-on storage device to activate said raster-scan output device and being responsive to the information in said turn-off storage device to de-activate said raster-Scan output device.

40. A system as in claim 39 wherein said turn-on and turn-off storage devices each comprise a random access memory device.

41. A system as in claim 33 wherein said second means is operable to determine said scan information for a scan line while the preceding scan line is being displayed by said raster-scan output device.

42. A system as in claim 41 wherein said vector identification information is stored in an order from the vector having the largest incremental length to the vector having the smallest incremental length.

43. A system as in claim 42 wherein said activating and de-activating means includes an up-down counter, said counter being counted up by bits located in said turn-on storage device and counted down by bits located in said turn-off storage device;

and wherein intensity input to said raster-scan output device is provided whenever the output of said counter is greater than zero.

44. A system as in claim 43 wherein said beginning and said endpoints of said incremental lengths are stored in said turn-on and turn-off storage devices, respectively, only if no bits have previously been stored at either of those locations in said turn-on and turn-off storage devices.

45. A system as in claim 44 wherein said activating and de-activating means includes a single pulse-providing circuit, and wherein said circuit is activated to provide a single point display on said raster-Scan output device whenever said turn-on and turn-off storage devices have bits stored at the same relative locations.

46. A system as in claim 33 including means for adding to and deleting from said first storage means vector identification information for selected individual vectors concUrrently with the display of graphical information.

47. A conversion system for converting digitally encoded graphical data comprising a plurality of arbitrary graphical lines for display on a raster-Scan output device, comprising:

a. means for storing information for each graphical line forming the graphical display;

b. means for accessing said information at least once during each scan period;

c. means for determining from said information for each graphical line, the incremental length of each intersection of the graphical line with each scan which it intersects;

d. means for determining for each scan line of said raster-Scan output device, on a scan line to scan-line basis, the location of the intersection lengths of all of the graphical lines which cross the scan line;

e. means, responsive to said accessing means, for generating activating and deactivating signals for said output device for each scan line according the location and incremental length of each graphical line determined by said determining means.

48. A method of digitally converting graphical information comprising a plurality of arbitrary graphical lines into a form suitable for displaying on a raster-scan output device, comprising the steps of:

a. receiving digitally encoded information for each graphical line to be displayed;

b. determining from said information for each graphical line, the length of each intersection of the graphical line with each scan line which it intersects;

c. determining for each scan line of said raster-scan output device, on a scan-line to scan-line basis, the location of the intersection lengths of all of the graphical lines which cross the scan-line; and

d. providing to said raster-scan output device, activating and deactivating signals in accordance with said determinations.

49. A method of digitally converting digitally encoded straight line vectors for display on a raster-scan output device comprising the steps of:

a. determining for each vector the incremental line segments of each scan of said output device for each of those scans intersected by the vector;

b. storing vector identification information for each vector, said information comprising at least said incremental line segments;

c. accessing each vector identification information for each vector at least once during each scan of said output device;

d. determining for each scan of said output device, scan information comprising the location of said incremental line segments for all vectors which intersect that scan line; and

e. providing to said raster-scan output device, activating and deactivating signals in accordance with said determinations.