PRINTING APPARATUS AND DITHER MASK

• US 20100141699A1
• Filed: 10/26/2009
• Published: 06/10/2010
• Est. Priority Date: 12/04/2008
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: KAKUTANI, Toshiaki, YAMAZAKI, Satoshi
• Granted Patent: US 8,376,495 B2
• Time in Patent Office: Days
• US Class Current: 347/15
• CPC Class Codes: B41J 19/142 with a reciprocating print head printing in both directions across the paper width

Abstract

Provided is a printing apparatus that performs printing by moving a print head in main scan directions and sub scan directions relative to a printing medium, including: an input unit that inputs image data constituting an image; a halftone processing unit that converts the input image data to dot data indicating whether or not dots are formed; and a printing unit that performs printing by controlling ejection of ink from the print head based on the result of the halftone process, wherein, in a printing area where an ink duty is in a predetermined range, the printing unit forms dots by forward movement in which the print head relatively moves in one direction of the main scan directions and backward movement in which the print head relatively moves in the direction opposite to the one direction so that a forward-moving dot occurrence ratio that is a ratio of forming the dots by the forward movement and a backward-moving dot occurrence ratio that is a ratio of forming the dots by the backward movement are gradually increased with a biased magnitude relation as the ink duty is increased.

Claims

1. A printing apparatus that performs printing by moving a print head in main scan directions and sub scan directions relative to a printing medium, comprising:

an input unit that inputs image data constituting an image;

a halftone processing unit that converts the input image data to dot data indicating whether or not dots are formed; and

a printing unit that performs printing by controlling ejection of ink from the print head based on the result of the halftone process,

wherein, in a printing area where an ink duty is in a predetermined range, the printing unit forms dots by forward movement in which the print head relatively moves in one direction of the main scan directions and backward movement in which the print head relatively moves in the direction opposite to the one direction so that a forward-moving dot occurrence ratio that is a ratio of forming the dots by the forward movement and a backward-moving dot occurrence ratio that is a ratio of forming the dots by the backward movement are gradually increased with a biased magnitude relation as the ink duty is increased.

2. The printing apparatus according to claim 1,

wherein the halftone processing unit compares a dither mask constructed with a plurality of threshold values with the image data to generate the dot data, and

wherein the plurality of threshold values of the dither mask are set so that the forward-moving dot occurrence ratio and the backward-moving dot occurrence ratio are gradually increased with the biased magnitude relation in the printing area.

3. The printing apparatus according to claim 2, wherein the plurality of threshold values of the dither mask are set so that dot dispersiveness of any one of the dots formed by the forward movement, the dots formed by the backward movement, and the entire dots formed by the forward movement and the backward movement can be secured.

4. The printing apparatus according to claim 1, wherein the halftone processing unit generates the dot data by an error diffusion method of quantizing the image data by comparing the image data with the predetermined threshold value while adding quantization errors of the image data to surrounding image data with a predetermined distribution ratio, so that the predetermined threshold value used to determine whether or not the dot is formed at any one of the dot forming position at which the dot is formed by the forward movement and the dot forming position at which the dot is formed by the backward movement in the printing area is relatively increased according to the dot forming position.

5. The printing apparatus according to claim 1, wherein the halftone processing unit generates the dot data by an error diffusion method of quantizing the image data by comparing the image data with the predetermined threshold value while adding quantization errors of the image data to surrounding image data with a predetermined distribution ratio, so that the quantization errors at the time of determining that the dots are formed in the printing area are added with a relatively high distribution ratio that is set to any one of the image data corresponding to the dot forming position at which the dots are formed by the forward movement and the image data corresponding to the dot forming position at which the dots are formed by the backward movement.

6. The printing apparatus according to claim 1, wherein the halftone processing unit generates the dot data by an error diffusion method of quantizing the image data by comparing the image data with the predetermined threshold value while adding quantization errors of the image data to surrounding image data with a predetermined distribution ratio, so that the quantization errors at the time of determining that the dots are not formed in the printing area are added with a relatively low distribution ratio that is set to any one of the image data corresponding to the dot forming position at which the dots are formed by the forward movement and the image data corresponding to the dot forming position at which the dots are formed by the backward movement.

7. The printing apparatus according to claim 1, wherein the printing unit at least controls ejection of a first ink having a predetermined ink color and a second ink having an ink color different from that of the first ink, so that the forward-moving dot occurrence ratio is larger than the backward-moving dot occurrence ratio with respect to the first ink, and so that the backward-moving dot occurrence ratio is larger than the forward-moving dot occurrence ratio with respect to the second ink.

8. A dither mask that is constructed with a plurality of threshold values to be used for a halftone process for performing printing by moving a print head in main scan directions and sub scan directions relative to a printing medium,

wherein, in a printing area where an ink duty is in a predetermined range, dots are formed by forward movement in which the print head relatively moves in one direction of the main scan directions and backward movement in which the print head relatively moves in the direction opposite to the one direction, and

wherein the plurality of threshold values are set so that a forward-moving dot occurrence ratio that is a ratio of forming the dots by the forward movement and a backward-moving dot occurrence ratio that is a ratio of forming the dots by the backward movement are gradually increased with a biased magnitude relation as the ink duty is increased.

9. A computer program product that is used to perform printing by moving a print head in main scan directions and sub scan directions relative to a printing medium, the computer program causing a computer to execute a function of performing printing by controlling ejection of ink from the print head, by forming dots, in a printing area where an ink duty is in a predetermined range, by forward movement in which the print head relatively moves in one direction of the main scan directions and backward movement in which the print head relatively moves in the direction opposite to the one direction so that a forward-moving dot occurrence ratio that is a ratio of forming the dots by the forward movement and a backward-moving dot occurrence ratio that is a ratio of forming the dots by the backward movement are gradually increased with a biased magnitude relation as the ink duty is increased.

10. A printing method of performing printing by moving a print head in main scan directions and sub scan directions relative to a printing medium, wherein printing is performed by controlling ejection of ink from the print head, by forming dots, in a printing area where an ink duty is in a predetermined range, by forward movement in which the print head relatively moves in one direction of the main scan directions and backward movement in which the print head relatively moves in the direction opposite to the one direction so that a forward-moving dot occurrence ratio that is a ratio of forming the dots by the forward movement and a backward-moving dot occurrence ratio that is a ratio of forming the dots by the backward movement are gradually increased with a biased magnitude relation as the ink duty is increased.