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

• US 8,045,212 B2
• Filed: 09/22/2009
• Issued: 10/25/2011
• Est. Priority Date: 02/12/2003
• Status: Active Grant

• 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:
  US12/564,646
• Publication Number:
  US 20100165404A1
• Time in Patent Office: 763 Days
• Field of Search: 358/1.1, 358/1.8, 358/1.9, 358/1.12, 358/1.13, 358/1.15, 358/1.18, 358/2.99, 358/3.01, 358/3.09, 358/3.2, 358/3.21, 358/3.27, 399/4, 700/166
• 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 an M-bit pulse width value from the N-bit value; and

a laser print engine to form an output pixel on media based on the M-bit pulse width value, wherein the modulation code generator is operative to concatenate at least one most significant bit of a current pixel to a least significant end of the current pixel.

2. The laser print apparatus of claim 1, wherein a window is moved across the multi-bit image to read the plurality of pixels and the plurality of pixels includes at least a center pixel, a left pixel, and a right pixel.

3. The laser print apparatus of claim 2, further comprising:

a justification generator to generate a justification value by comparing an N-bit value of the center pixel to either an N-bit value of the left pixel or an N-bit value of the right pixel.

4. The laser print apparatus of claim 1, wherein generating the M-bit value from the N-bit value is nonlinear.

5. A laser print apparatus comprising:

a memory to store a multi-bit image, wherein a window is moved across the multi-bit image to read a plurality of pixels at a time, the plurality of pixels including at least a center pixel, a left pixel, and a right pixel, each pixel represented by an N-bit value;

a pulse width generator to generate an M-bit pulse width value from an N-bit value of the center pixel; and

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

6. The laser print apparatus of claim 5, wherein the pulse width generator generates the M-bit pulse width value by multiplying the N-bit value by a multi-bit scaling factor.

7. The laser print apparatus of claim 5, wherein the pulse width generator generates the M-bit pulse width value by accessing a look up table indexed by the N-bit value of the center pixel.

8. The laser print apparatus of claim 5, wherein the pulse width generator generates the M-bit pulse width value by accessing a look up table indexed by a combination of the N-bit value of the center pixel and a portion of at least one of an N-bit value of the left pixel and an N-bit value of the right pixel.

9. The laser print apparatus of claim 5, further comprising:

a justification generator to generate a justification value based on the N-bit value of the center pixel and either an N-bit value of the left pixel or an N-bit value of the right pixel.

10. The laser print apparatus of claim 9, further comprising:

a comparator configured to determine whether the N-bit value of the right pixel subtracted from the N-bit value of the left pixel exceeds a predetermined number, wherein the justification value is set to a left justification when the N-bit value of the right pixel subtracted from the N-bit value of the left pixel exceeds the predetermined number.

11. The laser print apparatus of claim 9, further comprising:

a comparator configured to determine whether the N-bit value of the left pixel subtracted from the N-bit value of the right pixel exceeds a predetermined number, wherein the justification value is set to a right justification when the N-bit value of the left pixel subtracted from the N-bit value of the right pixel exceeds the predetermined number.

12. The laser print apparatus of claim 9, further comprising:

a comparator configured to determine whether the N-bit value of the left pixel added to the N-bit value of the right pixel exceeds a predetermined number, wherein the justification value is set to a split justification when the N-bit value of the left pixel added to the N-bit value of the right pixel exceeds the predetermined number.

13. The laser print apparatus of claim 5, wherein generating the M-bit pulse width value from the N-bit value is nonlinear.

14. A method for calculating modulation data for modulating a laser, the method comprising:

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

generating an M-bit pulse width value from the N-bit value by concatenating at least one more significant bit of a current pixel to a least significant end of the current pixel; and

printing an output pixel on a medium based on the M-bit pulse width value.

15. The method of claim 14, further comprising:

moving a window across the multi-bit image to read the plurality of pixels, wherein the plurality of pixels includes a center pixel, a left pixel, and a right pixel.

16. The method of claim 15, further comprising:

generating a justification value by comparing an N-bit value of the center pixel to either an N-bit value of the left pixel or an N-bit value of the right pixel.

17. The method of claim 15, further comprising:

generating a justification value by comparing an N-bit value of the left pixel to an N-bit value of the right pixel.

18. The method of claim 17, wherein the justification value indicates a left justification when the N-bit value of the left pixel exceeds the N-bit value of the right pixel by a predetermined amount, and the justification value indicates a right justification when the N-bit value of the right pixel exceeds the N-bit value of the left pixel by the predetermined amount.

19. The method of claim 14, wherein generating the M-bit pulse width value from the N-bit value is nonlinear.

20. The method of claim 14, wherein generating the M-bit pulse width value from the N-bit value is linear.