SCREEN GENERATING APPARATUS, SCREEN GENERATING METHOD, AND IMAGE PROCESSING APPARATUS

• US 20090213433A1
• Filed: 02/03/2009
• Published: 08/27/2009
• Est. Priority Date: 02/08/2008
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Tec Corporation (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation), Toshiba Tec Corporation (Toshiba Corporation)
• Inventors: Nakahara, Nobuhiko
• Granted Patent: US 8,254,002 B2
• Time in Patent Office: Days
• US Class Current: 358/3.70
• CPC Class Codes: H04N 1/4056 the pattern varying in one dimension only, e.g. dash length, pulse width modulation [PWM]
• CPC Class Codes: H04N 1/4058 with details for producing a halftone screen at an oblique angle H04N1/4056 takes precedence
• CPC Class Codes: H04N 1/52 Circuits or arrangements for halftone screening

Abstract

Disclosed is a method of generating a screen for an image processing apparatus, which reproduces a multi-gradation image in one pixel using a PWM technique for controlling a pulse width and reference position data. The method includes inputting image data with a first resolution, virtually increasing the first resolution to a second resolution using the reference position data, and generating a screen with the second resolution with respect to the image data using two reference vectors based on the reference position data.

Claims

1. A method of generating a screen for an image processing apparatus, which reproduces a multi-gradation image in one pixel using a PWM technique for controlling a pulse width and reference position data, the method comprising:

inputting image data with a first resolution; and

generating a screen with a second resolution with respect to the image data using two reference vectors based on the reference position data, the second resolution being enhanced from the first resolution using the reference position data.

2. The method according to claim 1,

wherein the screen formed with the second resolution includes halftone dots with a line number and angle which are not included in the screen formed with the first resolution.

3. The method according to claim 1,

wherein the second resolution is set to be three times higher than the first resolution using three kinds of left, center, and right position signals as the reference position data.

4. The method according to claim 1,

wherein the second resolution is set to be two times higher than the first resolution using two kinds of left and right position signals as the reference position data.

5. The method according to claim 1,

wherein, when a color screen is formed, the screen formed with the second resolution and a screen formed with the first resolution are selectively combined for each color, to thereby adjust a difference in screen angle between colors.

6. The method according to claim 1,

wherein, when the screen is formed with the second resolution, if subpixels within one pixel are allocated to different halftone cells, a position signal of a subpixel having a high priority of pixel growth is preferentially allocated to a corresponding pixel.

7. The method according to claim 1,

wherein the image is an image in which a plurality of pixels are arranged in a main scanning direction and a sub scanning direction.

8. The method according to claim 7,

wherein the second resolution is set to be K times higher than the first resolution using K kinds (where K is an integer of 2 or more) of position signals as the reference position data.

9. The method according to claim 8,

wherein a screen angle α

of at least one color is expressed by the following expression;

tan α

=k×

j/(n+k×

i)

tan α

≠

(j/i)

for the expression, i is a main scan side arbitrary integer, j is a sub scan side arbitrary integer, k is the number of kinds of reference position signals, and n is an integer ranging from 0 to (k−

1).

10. An apparatus for generating a screen that reproduces a multi-gradation image in one pixel using a PWM technique for controlling a pulse width and reference position data, the apparatus comprising:

an input section configured to input image data with a first resolution;

a resolution conversion section configured to increase the first resolution to a second resolution using the reference position data; and

a screen generation section configured to generate a screen with the second resolution with respect to the image data using two reference vectors based on the reference position data.

11. The apparatus according to claim 10,

wherein the screen formed with the second resolution includes halftone dots with a line number and angle which are not included in the screen formed with the first resolution.

12. The apparatus according to claim 10,

wherein the resolution conversion section sets the second resolution to be three times higher than the first resolution using three kinds of left, center, and right position signals as the reference position data.

13. The apparatus according to claim 10,

wherein the resolution conversion section sets the second resolution to be two times higher than the first resolution using two kinds of left and right position signals as the reference position data.

14. The apparatus according to claim 10,

wherein, when generating a color screen, the screen generation section selectively combines the screen formed with the second resolution and a screen formed with the first resolution for each color, to thereby adjust a difference in screen angle between colors.

15. The apparatus according to claim 10,

wherein, when the screen is formed with the second resolution, if subpixels within one pixel are allocated to different halftone cells, the screen generation section preferentially allocates a position signal of a subpixel having a high priority of pixel growth to a corresponding pixel.

16. The apparatus according to claim 10,

wherein the image is an image in which a plurality of pixels are arranged in a main scanning direction and a sub scanning direction.

17. The apparatus according to claim 16, higher than the first resolution using K kinds (where K

wherein the second resolution is set to be K times is an integer of 2 or more) of position signals as the reference position data.

18. The apparatus according to claim 17,

wherein a screen angle α

of at least one color is expressed by the following expression;

tan α

=k×

j/(n+k×

i)

tan α

≠

(j/i).

for the expression, i is a main scan side arbitrary integer, j is a sub scan side arbitrary integer, k is the number of kinds of reference position signals, and n is an integer ranging from 0 to (k−

1).

19. An image processing apparatus that supplies output data to an image forming apparatus, which reproduces a multi-gradation image in one pixel using a PWM technique for controlling a pulse width and reference position data, the apparatus comprising:

an input section configured to input image data with a first resolution;

a resolution conversion section configured to increase the first resolution to a second resolution using the reference position data; and

a screen generation section configured to generate output data obtained by screening the image data with the second resolution using two reference vectors based on the reference position data.

20. The apparatus according to claim 19,

wherein the image is an image in which a plurality of pixels are arranged in a main scanning direction and a sub scanning direction,

the second resolution is set to be K times higher than the first resolution using K kinds (where K is an integer of 2 or more) of position signals as the reference position data, and

a screen angle α

of at least one color is expressed by the following expression;

tan α

=k×

j/(n+k×

i)

tan α

≠

(j/i).

for the expression, i is a main scan side arbitrary integer, j is a sub scan side arbitrary integer, k is the number of kinds of reference position signals, and n is an integer ranging from 0 to (k−

1).