Laser print apparatus that generates pulse width value and justification value based on pixels in a multi-bit image

• US 7,280,246 B2
• Filed: 02/12/2003
• Issued: 10/09/2007
• Est. Priority Date: 02/12/2003
• Status: Expired due to Fees

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Technology, Ltd. (Marvell Technology Group Limited)
• Inventors: Keithley, Douglas G., Marshall, John D.
• Primary Examiner(s): Garcia; Gabriel I.
• Application Number:
  US10/365,563
• Publication Number:
  US 20040156079A1
• Time in Patent Office: 1,700 Days
• Field of Search: 358/1.1, 358/1.8, 358/1.9, 358/1.12, 358/1.13, 358/1.15, 358/1.16, 358/1.18, 358/2.99, 358/3.01, 358/3.09, 358/3.2, 358/3.21
• US Class Current: 358/1.16
• CPC Class Codes: B41J 2/47 using the combination of scanning and modulation of light
• CPC Class Codes: H04N 1/4056 the pattern varying in one dimension only, e.g. dash length, pulse width modulation [PWM]

Abstract

A laser print apparatus includes a memory for storing a multi-bit image including a plurality of pixels. Each pixel is represented by an N-bit value, wherein N is greater than one. A modulation code generator analyzes three adjacent pixels. The three adjacent pixels include a left pixel, a center pixel, and a right pixel. The modulation code generator is configured to generate a pulse width value based on the value of the center pixel, and a justification value based on the values of the left pixel and the right pixel. A laser print engine forms an output pixel on media based on the pulse width value and the justification value.

Claims

1. A laser print apparatus comprising:

a memory to store a multi-bit image including a plurality of pixels, each pixel represented by an N-bit value, wherein N is greater than one;

a modulation code generator to analyze three adjacent pixels, the three adjacent pixels including a left pixel, a center pixel, and a right pixel, the modulation code generator configured to generate a pulse width value based on concatenating at least one most significant bit of the center pixel to the least significant end of the value for the center pixel, and a justification value based on the values of the left pixel and the right pixel; and

a laser print engine to form an output pixel on media based on the pulse width value and the justification value.

2. The laser print apparatus of claim 1, wherein the laser print engine comprises:

a laser configured to be modulated for the output pixel so as to be turned on and off at times corresponding to the justification value for the pixel, and remain on for a time period corresponding to the pulse width value for the pixel.

3. The laser print apparatus of claim 1, wherein the justification value is a 2-bit value representing one of left justify, right justify, split justify, and center justify.

4. The laser print apparatus of claim 1, wherein N=4.

5. The laser print apparatus of claim 1, wherein the pulse width value is a 6-bit value.

6. The laser print apparatus of claim 1, and further comprising:

a first-in first-out (FIFO) device for outputting the three adjacent pixels to the modulation code generator.

7. The laser print apparatus of claim 1, wherein the modulation code generator comprises:

a first subtracter for subtracting the value of the right pixel from the value of the left pixel, thereby generating a first difference;

a second subtracter for subtracting the value of the left pixel from the value of the right pixel, thereby generating a second difference; and

an adder for adding the value of the left pixel and the value of the right pixel, thereby generating a sum.

8. The laser print apparatus of claim 7, wherein the modulation code generator further comprises:

at least one comparator for comparing the first difference to a first threshold value, to compare the second difference to a second threshold value, and to compare the sum to a third threshold value; and

a justification code generator for generating the justification value based on results of the comparisons made by the at least one comparator.

9. The laser print apparatus of claim 8, wherein the justification code generator generates a justification value indicating left justify if the first difference is greater than the first threshold, generates a justification value indicating right justify if the second difference is greater than the second threshold, generates a justification value indicating split justify if the sum is greater than the third threshold, and generates a justification value indicating center justify if the none of the first, second, or third thresholds are exceeded.

10. The laser print apparatus of claim 1, wherein the modulation code generator comprises:

a look up table for receiving the values of the left, center, and right pixels as an input address, and outputting a corresponding modulation code, the modulation code including the pulse width value and the justification value.

11. The laser print apparatus of claim 1, wherein the modulation code generator comprises:

a look up table for receiving the value of the center pixel and at least one most significant bit of the values for the left and right pixels as an input address, and to output a corresponding modulation code, the modulation code including the pulse width value and the justification value.

12. The laser print apparatus of claim 1, wherein the modulation code generator comprises:

a first look up table for receiving the values of the left and right pixels as an input address, and to output a corresponding justification value; and

a second look up table for receiving the value of the center pixel as an input address, and to output a corresponding pulse width value.

13. A method for generating modulation data for modulating a laser in a laser print apparatus, the method comprising:

rendering data to be printed into a multi-bit image including a plurality of pixels, each pixel represented by a multi-bit value;

examining the values of first, second, and third pixels that are correspondingly positioned at three sequential positions in the multi-bit image;

generating a first pulse width value based on concatenating at least one most significant bit of the center pixel to the least significant end of the value for the center pixel; and

generating a first justification value based on the values of the first pixel and the third pixel.

14. The method of claim 13, wherein the laser is turned on and off at times corresponding to the first justification value, and remains on for a time period corresponding to the first pulse width value.

15. The method of claim 13, wherein the first justification value is a 2-bit value representing one of left justify, right justify, split justify, and center justify.

16. The method of claim 13, and further comprising:

providing at least one look up table that associates pixel values with pulse width values and justification values, and wherein the first pulse width value and the first justification value are generated by providing the values of the first, second, and third pixels as an input address to the at least one look up table.

17. The method of claim 16, wherein the at least one look up table provides a linear mapping between pixel values and pulse width values.

18. The method of claim 16, wherein the at least one look up table provides a non-linear mapping between pixel values and pulse width values.

19. A laser print apparatus comprising:

a memory for storing an image including a plurality of pixels, each pixel represented by a multi-bit value;

a first modulation code generator to generate a pulse width value for each pixel in the image by concatenating at least on most significant bit of the each pixel to the least significant end of the value for the each pixel;

a second modulation code generator to generate a justification value for each pixel in the image based on the multi-bit values of adjacent pixels; and

a laser print engine for forming an image on media based on the pulse width values and the justification values.

20. A laser print apparatus comprising:

means for storing a multi-bit image including a plurality of pixels, each pixel represented by an N-bit value, wherein N is greater than one;

means for analyzing three adjacent pixels, the three adjacent pixels including a left pixel, a center pixel, and a right pixel, and generating a pulse width value based on concatenating at least one most significant bit of the center pixel to the least significant end of the value for the center pixel, and a justification value based on the values of the left pixel and the right pixel; and

means for forming an output pixel on media based on the pulse width value and the justification value.

21. The laser print apparatus of claim 20, wherein the means for forming comprises:

a laser configured to be modulated for the output pixel so as to be turned on and off at times corresponding to the justification value for the pixel, and remain on for a time period corresponding to the pulse width value for the pixel.

22. The laser print apparatus of claim 20, wherein the justification value is a 2-bit value representing one of left justify, right justify, split justify, and center justify.

23. The laser print apparatus of claim 20, wherein N=4.

24. The laser print apparatus of claim 20, wherein the pulse width value is a 6-bit value.

25. The laser print apparatus of claim 20, and further comprising:

a first-in first-out (FIFO) device to output the three adjacent pixels to the means for analyzing.

26. The laser print apparatus of claim 20, wherein the means for analyzing comprises:

a first subtracter to subtract the value of the right pixel from the value of the left pixel, thereby generating a first difference;

a second subtracter to subtract the value of the left pixel from the value of the right pixel, thereby generating a second difference; and

an adder to add the value of the left pixel and the value of the right pixel, thereby generating a sum.

27. The laser print apparatus of claim 26, wherein the means for analyzing further comprises:

at least one comparator to compare the first difference to a first threshold value, to compare the second difference to a second threshold value, and to compare the sum to a third threshold value; and

a justification code generator to generate the justification value based on results of the comparisons made by the at least one comparator.

28. The laser print apparatus of claim 27, wherein the justification code generator generates a justification value indicating left justify if the first difference is greater than the first threshold, generates a justification value indicating right justify if the second difference is greater than the second threshold, generates a justification value indicating split justify if the sum is greater than the third threshold, and generates a justification value indicating center justify if the none of the first, second, or third thresholds are exceeded.

29. The laser print apparatus of claim 20, wherein the means for analyzing comprises:

a look up table to receive the values of the left, center, and right pixels as an input address, and to output a corresponding modulation code, the modulation code including the pulse width value and the justification value.

30. The laser print apparatus of claim 20, wherein the means for analyzing comprises:

a look up table to receive the value of the center pixel and at least one most significant bit of the values for the left and right pixels as an input address, and to output a corresponding modulation code, the modulation code including the pulse width value and the justification value.

31. The laser print apparatus of claim 20, wherein the means for analyzing comprises:

a first look up table to receive the values of the left and right pixels as an input address, to output a corresponding justification value; and

a second look up table to receive the value of the center pixel as an input address, and to output a corresponding pulse width value.

32. A laser printing method comprising:

storing a multi-bit image including a plurality of pixels, each pixel represented by an N-bit value, wherein N is greater than one;

analyzing three adjacent pixels, the three adjacent pixels including a left pixel, a center pixel, and a right pixel, and generating a pulse width value based on concatenating at least one most significant bit of the center pixel to the least significant end of the value for the center pixel, and a justification value based on the values of the left pixel and the right pixel; and

forming an output pixel on media based on the pulse width value and the justification value.

33. The laser printing method of claim 32, wherein the justification value is a 2-bit value representing one of left justify, right justify, split justify, and center justify.

34. The laser printing method of claim 32, wherein N=4.

35. The laser printing method of claim 32, wherein the pulse width value is a 6-bit value.

36. The laser printing method of claim 32, wherein analyzing the three adjacent pixels comprises:

subtracting the value of the right Pixel from the value of the left pixel, thereby generating a first difference;

subtracting the value of the left pixel from the value of the right pixel, thereby generating a second difference; and

adding the value of the left pixel and the value of the right pixel, thereby generating a sum.

37. The laser printing method of claim 36, wherein analyzing the three adjacent pixels further comprises:

comparing the first difference to a first threshold value;

comparing the second difference to a second threshold value, and

comparing the sum to a third threshold value; and

generating the justification value based on results of the comparisons made by the at least one comparator.

38. The laser printing method of claim 37, wherein generating the justification value comprises generating a justification value indicating left justify if the first difference is greater than the first threshold, generating a justification value indicating right justify if the second difference is greater than the second threshold, generating a justification value indicating split justify if the sum is greater than the third threshold, and generating a justification value indicating center justify if the none of the first, second, or third thresholds are exceeded.

39. The laser printing method of claim 32, wherein analyzing three adjacent pixels comprises:

receiving the values of the left, center, and right pixels as an input address, and

outputting a corresponding modulation code, the modulation code including the pulse width value and the justification value.

40. The laser printing method of claim 32, wherein the analyzing three adjacent pixels comprises:

receiving the value of the center pixel and at least one most significant bit of the values for the left and right pixels as an input address, and

outputting a corresponding modulation code, the modulation code including the pulse width value and the justification value.

41. The laser printing method of claim 32, wherein the analyzing three adjacent pixels comprises:

receiving the values of the left and right pixels as an input address, and outputting a corresponding justification value; and

receiving the value of the center pixel as an input address, and outputting a corresponding pulse width value.

42. A computer-readable medium having computer-readable content to cause a computer to perform acts of:

storing a multi-bit image including a plurality of pixels, each pixel represented by an N-bit value, wherein N is greater than one;

analyzing three adjacent pixels, the three adjacent pixels including a left pixel, a center pixel, and a right pixel, and generating a pulse width value based on concatenating at least one most significant bit of a value for the center pixel to the least significant end of the value for the center pixel operating on the value of the center pixel, and a justification value based on the values of the left pixel and the right pixel; and

forming an output pixel on media based on the pulse width value and the justification value.

43. The computer-readable medium of claim 42 wherein the justification value is a 2-bit value representing one of left justify, right justify, split justify, and center justify.

44. The computer-readable medium of claim 42, wherein N=4.

45. The computer-readable medium of claim 42, wherein the pulse width value is a 6-bit value.

46. The computer-readable medium of claim 42, wherein analyzing the three adjacent pixels comprises:

subtracting the value of the right pixel from the value of the left pixel, thereby generating a first difference;

subtracting the value of the left pixel from the value of the right pixel, thereby generating a second difference; and

adding the value of the left pixel and the value of the right pixel, thereby generating a sum.

47. The computer-readable medium of claim 46, wherein analyzing the three adjacent pixels further comprises:

comparing the first difference to a first threshold value;

comparing the second difference to a second threshold value, and

comparing the sum to a third threshold value; and

generating the justification value based on results of the comparisons made by the at least one comparator.

48. The computer-readable medium of claim 47, wherein generating the justification value comprise generating a justification value indicating left justify if the first difference is greater than the first threshold, generating a justification value indicating right justify if the second difference is greater than the second threshold, generating a justification value indicating split justify if the sum is greater than the third threshold, and generating a justification value indicating center justify if the none of the first, second, or third thresholds are exceeded.

49. The computer-readable medium of claim 42, wherein analyzing three adjacent pixels comprises:

receiving the values of the left, center, and right pixels as an input address, and

outputting a corresponding modulation code, the modulation code including the pulse width value and the justification value.

50. The computer-readable medium of claim 42, wherein the analyzing three adjacent pixels comprises:

receiving the value of the center pixel and at least one most significant bit of the values for the left and right pixels as an input address, and

outputting a corresponding modulation code, the modulation code including the pulse width value and the justification value.

51. The computer-readable medium of claim 42, wherein the analyzing three adjacent pixels comprises:

receiving the values of the left and right pixels as an input address, and outputting a corresponding justification value; and

receiving the value of the center pixel as an input address, and outputting a corresponding pulse width value.