Method and apparatus for adjusting light intensity based on content to achieve a uniform exposure

Patent metadata

Field	Value
Publication number	US-8947740-B1
Application number	US-201414181989-A
Country	US
Kind code	B1
Filing date	Feb 17, 2014
Priority date	Feb 17, 2014
Publication date	Feb 3, 2015
Grant date	Feb 3, 2015

Abstract

A method, non-transitory computer readable medium, and apparatus for adjusting a light intensity of a printhead are disclosed. For example, the method receives an image comprising a plurality of pixels, calculates a correction factor for each one of a plurality of pixels of the image by applying a filter to each one of the plurality of pixels of the image and summing a contribution of the light intensity of each one of a plurality of surrounding pixels to a pixel being analyzed to calculate an overlap value and comparing the overlap value to a development threshold range and adjusts the light intensity of a light source of the printhead in accordance with the correction factor of each one of the plurality of pixels of the image that require toner.

First claim

What is claimed is:

1. A method for adjusting a light intensity of a printhead, comprising:
receiving, by a processor, an image comprising a plurality of pixels;
calculating, by the processor, a correction factor for each one of a plurality of pixels of the image by applying a filter to each one of the plurality of pixels of the image and summing a contribution of the light intensity of each one of a plurality of surrounding pixels to a pixel being analyzed to calculate an overlap value and comparing the overlap value to a development threshold range; and
adjusting, by the processor, the light intensity of a light source of the printhead in accordance with the correction factor of each one of the plurality of pixels of the image that require toner.

2. The method of claim 1 , wherein the filter comprises a Gaussian profile.

3. The method of claim 1 , wherein the adjusting comprises:
reducing, by the processor, a power delivered to the light source that correspond to the one or more pixels that have the overlap value above the development threshold range to reduce the light intensity of the light source that correspond to the one or more pixels.

4. The method of claim 1 , wherein the adjusting comprises:
increasing, by the processor, a power delivered to the light source that correspond to the one or more pixels that have the overlap value below the development threshold range to increase the light intensity of the light source that correspond to the one or more pixels.

5. The method of claim 1 , wherein the adjusting comprises:
maintaining, by the processor, a power delivered to the light source that correspond to the one or more pixels that have the overlap value within the development threshold range to maintain the light intensity the light source that correspond to the one or more pixels.

6. The method of claim 1 , wherein the adjusting is performed on a line by line basis of the image.

7. The method of claim 1 , wherein the light source comprises a plurality of LEDs on the printhead or a laser.

8. The method of claim 7 , wherein the adjusting comprises adjusting the light intensity of each one of the LEDS of the printhead that correspond to a pixel of the plurality of pixels of the image that require an adjustment.

9. The method of claim 7 , wherein the correction factor for each one of a line of pixels of the image is provided to the printhead with a calibration factor of each one of the plurality of LEDs of the printhead between two consecutive lines of the image.

10. The method of claim 7 , wherein a calibration factor is adjusted with the correction factor for to calculate a modified calibration factor for a current line of pixels of the image that is written into a first buffer of a double buffer and the calibration factor of a subsequent line of pixels of the image is read into a second buffer of the double buffer.

11. A non-transitory computer-readable medium storing a plurality of instructions which, when executed by a processor, cause the processor to perform operations for adjusting a light intensity of a printhead, the operations comprising:
receiving an image comprising a plurality of pixels;
calculating a correction factor for each one of a plurality of pixels of the image by applying a filter to each one of the plurality of pixels of the image and summing a contribution of the light intensity of each one of a plurality of surrounding pixels to a pixel being analyzed to calculate an overlap value and comparing the overlap value to a development threshold range; and
adjusting the light intensity of a light source of the printhead in accordance with the correction factor of each one of the plurality of pixels of the image that require toner.

12. The non-transitory computer-readable medium of claim 11 , wherein the adjusting comprises:
reducing, by the processor, a power delivered to the light source that correspond to the one or more pixels that have the overlap value above the development threshold range to reduce the light intensity of the light source that correspond to the one or more pixels.

13. The non-transitory computer-readable medium of claim 11 , wherein the adjusting comprises:
increasing, by the processor, a power delivered to the light source that correspond to the one or more pixels that have the overlap value below the development threshold range to increase the light intensity of the light source that correspond to the one or more pixels.

14. The non-transitory computer-readable medium of claim 11 , wherein the adjusting comprises:
maintaining, by the processor, a power delivered to the light source that correspond to the one or more pixels that have the overlap value within the development threshold range to maintain the light intensity the light source that correspond to the one or more pixels.

15. The non-transitory computer-readable medium of claim 11 , wherein the adjusting is performed on a line by line basis of the image.

16. The non-transitory computer-readable medium of claim 11 , wherein the light source comprises a plurality of LEDs on the printhead or a laser.

17. The non-transitory computer-readable medium of claim 16 , wherein the adjusting comprises adjusting the light intensity of each one of the LEDS of the printhead that correspond to a pixel of the plurality of pixels of the image that require an adjustment.

18. The non-transitory computer-readable medium of claim 16 , wherein the correction factor for each one of a line of pixels of the image is provided to the printhead with a calibration factor of each one of the plurality of LEDs of the printhead between two consecutive lines of the image.

19. The non-transitory computer-readable medium of claim 16 , wherein a calibration factor is adjusted with the correction factor for to calculate a modified calibration factor for a current line of pixels of the image that is written into a first buffer of a double buffer and the calibration factor of a subsequent line of pixels of the image is read into a second buffer of the double buffer.

20. A method for adjusting a light intensity of a printhead, comprising:
receiving, by a processor, an image comprising a plurality of lines, each one of the plurality of lines comprising a plurality of pixels, wherein each one of the plurality of pixels correspond to an LED of a plurality of LEDs of the LED printhead;
calculating, by the processor, an overlap value for each one of a plurality of pixels of the image by applying a Gaussian filter to each one of all pixels of the image and summing a contribution of the light intensity of each one of a plurality of surrounding pixels to a pixel being analyzed;
calculating, by the processor, a correction factor based on a comparison of the overlap value to a development threshold range;
providing, by the processor, the correction factor for each one of the plurality of pixels of a current line of the plurality of lines to the LED printhead;
adjusting, by the processor, a power of each one of one or more LEDs of the plurality of LEDs in accordance with the correction factor to adjust the light intensity of the each one of the one or more LEDs that correspond to a respective one of the plurality of pixels that require toner of the current line; and
repeating, by the processor, the providing and the adjusting for each line of the plurality of lines of the image.

Assignees

• Xerox Corp

Inventors

• Wilsher Michael J
• De Echaniz Sebastián R

Classifications

• H04N1/40056 Primary

  Circuits for driving or energising particular reading heads or original illumination means (H04N1/401, H04N1/407 take precedence) · CPC title

• H04N1/0288 Primary

  using a two-dimensional light source, e.g. two-dimensional LED array · CPC title

• G03G15/04054

  by LED arrays · CPC title

• H04N1/40025 Primary

  Circuits exciting or modulating particular heads for reproducing continuous tone value scales (H04N1/401, H04N1/407 take precedence) · CPC title

• G03G15/043

  with means for controlling illumination or exposure (G03G15/041 takes precedence) · CPC title