IMAGE FORMING DEVICE, AND DENSITY CONTROL METHOD OF THE IMAGE FORMING DEVICE

Abstract

An image forming device scans an original document and generates a bi-level image signal. The image forming device obtains a first counted value by counting black pixels included in the bi-level image signal. The image forming device obtains a first generation copy by forming an image on a printing medium according to the bi-level image signal of the original document. The image forming device scans the first generation copy and generates a second bi-level image signal. The image forming device obtains a second counted value by counting the black pixels included in the second bi-level image signal. The image forming device compares whether or not the second counted value is within a target range of the first counted value, and controls the density of an image to be formed according to the comparison result.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a network system including an MFP.

FIG. 2 is a block diagram illustrating a hardware configuration of the MFP.

FIG. 3 is a block diagram illustrating a counter arranged in a printer unit to count a number of black pixels.

FIG. 4 is a block diagram illustrating a configuration of a density adjusting unit of a printer image signal processor.

FIG. 5 illustrates pulses output by the density adjusting unit.

FIG. 6 illustrates a change in the density of an image.

FIG. 7 is a flowchart illustrating a process for adjusting the density of an image.

FIG. 8 illustrates an example of a confirmation screen when changing the density.

FIG. 9 illustrates another example of a confirmation screen when changing the density.

Claims

1. An image forming device comprising: an image scanning unit arranged to scan an original image of an original document and generate a bi-level image signal;an image forming unit arranged to form an image on a printing medium according to the bi-level image signal;a counter arranged to count a value of black pixels included in the bi-level image signal;a memory unit arranged to store the value counted by the counter;a comparator arranged to compare a first counted value of black pixels included in the bi-level image signal generated by scanning the original image with a second counted value of black pixels included in a second bi-level image signal generated by scanning an image copied from the original image; anda control unit arranged to control a density of an image to be formed such that the second counted value is within a target range of the first counted value.

2. The image forming device according to claim 1, further comprising: a laser scanner unit arranged in the image forming unit; anda density adjustment unit arranged to change a pulse width of a laser in the laser scanner unit.

3. The image forming device according to claim 2, further comprising: a plurality of pulse generators arranged to generate pulses having different pulse widths; anda selector arranged to select one of the pulse generators.

4. The image forming device according to claim 3, further comprising an AND gate to which the pulses output from the selector and the bi-level image signal are input.

5. The image forming device according to claim 4, further comprising a delay circuit arranged to delay a trailing edge of the pulses output from the AND gate.

6. The image forming device according to claim 1, further comprising: a second comparator arranged to set a permissible range to be wider than the target range, and to compare whether or not the second counted value is within the permissible range of the first counted value; anda display unit arranged to display a message when the second comparator determines that the second counted value is outside the permissible range.

7. An image forming device comprising: means for scanning an original image of an original document and generating a bi-level image signal;means for forming an image on a printing medium according to the bi-level image signal;means for counting black pixels included in the bi-level image signal;means for storing a counted value;means for comparing a first counted value of black pixels included in a bi-level image signal generated by scanning the original image with a second counted value of black pixels included in a second bi-level image signal generated by scanning an image copied from the original image; andmeans for controlling a density of an image to be formed such that the second counted value is within a target range of the first counted value.

8. The image forming device according to claim 7, further comprising: means for scanning by laser light arranged in the means for forming; andmeans for changing a pulse width for driving a laser light source in the means for scanning.

9. The image forming device according to claim 8, further comprising: means for generating a plurality of pulses having different pulse widths; andmeans for selecting one pulse from the plurality of pulses.

10. The image forming device according to claim 9, further comprising means for obtaining a logical AND of the selected pulse and the bi-level image signal and outputting a second pulse.

11. The image forming device according to claim 10, further comprising means for delaying a trailing edge of the second pulse, which is the logical AND of the selected pulse and the bi-level image signal.

12. The image forming device according to claim 7, further comprising: means for setting a permissible range to be larger than the target range and comparing whether or not the second counted value is within the permissible range of the first counted value; andmeans for providing notification when the second counted value is determined to be outside the permissible range.

13. A density control method of an image forming device, the method comprising the steps of: scanning an original document and generating a bi-level image signal;obtaining a first counted value by counting black pixels included in the bi-level image signal;obtaining a first generation copy by forming an image on a printing medium according to the bi-level image signal of the original document;scanning the first generation copy and generating a second bi-level image signal;obtaining a second counted value by counting black pixels included in the second bi-level image signal;comparing whether or not the second counted value is within a target range of the first counted value; andcontrolling a density of an image to be formed according to a comparison result obtained in the comparing step.

14. The density control method of the image forming device according to claim 13, the method further comprising the steps of: reducing the density of the image by one level when the second counted value is larger than the target range; andincreasing the density of the image by one level when the second counted value is smaller than the target range.

15. The density control method of the image forming device according to claim 13, the method further comprising the steps of: setting a permissible range larger than the target range; andproviding notification of an error when the second counted value is outside of the permissible range.

16. The density control method of the image forming device according to claim 13, the method further comprising the steps of: generating a plurality of pulses having a plurality of duty ratios;selecting one pulse from the plurality of the pulses; andgenerating a second pulse by obtaining a logic AND of the selected pulse and the bi-level image signal.

17. The density control method of the image forming device according to claim 16, the method further comprising the step of delaying a trailing edge of the second pulse.

18. The density control method of the image forming device according to claim 17, the method further comprising the steps of: driving a laser light source by the second pulse or the second pulse of which the trailing edge has been delayed; andforming an image by scanning by laser light from the laser light source.