LASER PRINT APPARATUS THAT GENERATES PULSE WIDTH VALUE AND JUSTIFICATION VALUE BASED ON PIXELS IN A MULTI-BIT IMAGE

• US 20080030783A1
• Filed: 10/08/2007
• Published: 02/07/2008
• Est. Priority Date: 02/12/2003
• Status: Active Grant

• Current Assignee: Douglas Keithley, John Marshall
• Original Assignee: Douglas Keithley, John Marshall
• Inventors: Marshall, John, Keithley, Douglas
• Granted Patent: US 7,609,409 B2
• Time in Patent Office: Days
• 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;

a modulation code generator to generate a pulse width value, the pulse width value represented by an M-bit value where M>

N, the modulation code generator linearly mapping the N bit value to the M-bit value; and

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

2. The laser print apparatus of claim 1 wherein the modulation code generator is operative to concatenate a portion of a current pixel to a justification value of the current pixel to form the M-bit value for the pulse width value for the current pixel.

3. The laser print apparatus of claim 1 wherein the modulation code generator is operative to concatenate at least one most significant bit of the current pixel to the least significant end of a justification value for the current pixel.

4. The laser print apparatus of claim 1 wherein the modulation code generator is operative to generate a justification value for the output pixel based on values of pixels adjacent to a current pixel.

5. 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 output pixel, and remain on for a time period corresponding to the pulse width value for the output pixel.

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

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

8. 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 pixel value;

for each pixel, linearly mapping the multi-bit pixel value for the each pixel to the pulse width value to generate a pulse width value.

9. The method of claim 8 further comprising:

generating a justification value for each pixel based on the values of the each pixel and an adjacent pixel; and

providing the pulse width value and the justification value for the each pixel to a laser print engine to form a pixel.

10. The method of claim 9 further comprising:

turning on and turning off a laser at times defined by the justification value and turning the laser on for a period defined by the pulse width value.

11. The method of claim 8 wherein generating the pulse width value comprises scaling the multi-bit pixel value by combining the multi-bit pixel value with a portion of the multi-bit pixel value.

12. The method of claim 8 wherein generating the pulse width value comprises concatenating for the each pixel one or more most significant bits of the multi-bit pixel value to the least significant end of the multi-bit pixel value.

13. The method of claim 8 wherein generating the pulse width value comprises generating a 6-bit value from a 4-bit pixel value.

14. A laser print apparatus comprising:

a memory to store data defining an image including a plurality of pixels, each pixel of the image being represented by a multi-bit value;

a first modulation code generator in communication with the memory to generate a pulse width value for each pixel in the image by appending a first portion of the multi-bit value for the each pixel to a second portion of the multi-bit value for the each pixel;

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

a laser print engine in communication with the first modulation code generator and the second modulation code generator to form an image on media based on the pulse width value and the justification value.

15. The laser print apparatus of claim 14 wherein the modulation code generator is operative to scale an N-bit value for the each pixel to an M-bit value for the generated pulse width value.

16. The laser print apparatus of claim 15 wherein N=4 and M=6.

17. The laser print apparatus of claim 14 wherein the justification value comprises a 2-bit value representing one of left justify, right justify, split justify, and center justify.

18. A laser print apparatus comprising:

means for storing data defining 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 generating a pulse width value for each pixel in the multi-bit image by appending a first portion of the N-bit value for the each pixel to a second portion of the N-bit value for the each pixel;

means for generating a justification value based on the values of pixels adjacent to the each pixel; and

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

19. The laser print apparatus of claim 18 wherein the justification value comprises a 2-bit value representing one of left justify, right justify, split justify, and center justify.

20. The laser print apparatus of claim 18, wherein N=4 and wherein the pulse width value is a 6-bit value.

21. A laser print apparatus comprising:

means for storing data defining 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 generating a pulse width value for each pixel in the multi-bit image by appending a first portion of the N-bit value for the each pixel to a second portion of the N-bit value for the each pixel; and

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

22. The laser print apparatus of claim 21 further comprising:

means for generating a justification value based on the values of the each pixel, a left pixel to the left of the each pixel, and a right pixel to the right of the each pixel.

23. The laser print apparatus of claim 22 wherein the means for generating comprises:

first subtracting means for subtracting the value of the right pixel from the value of the left pixel to generate a first difference;

second subtracting means for subtracting the value of the left pixel from the value of the right pixel to generate a second difference; and

add means for adding the value of the left pixel and the value of the right pixel to generate a sum.

24. The laser print apparatus of claim 23, wherein the means for generating further comprises:

comparator means for comparing the first difference to a first threshold value, for comparing the second difference to a second threshold value, and for comparing the sum to a third threshold value; and

justification code generating means for generating the justification value based on results of the comparisons made by the comparator means.

25. The laser print apparatus of claim 23 wherein the means for generating a pulse width value 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 is exceeded.