Image recording apparatus and image recording method
View Patent ↗An image recording apparatus has low intensity ink ejection parts for ejecting low intensity ink, and a high intensity ink ejection part for ejecting high intensity ink. With respect to a direction orthogonal to a moving direction of printing paper, a pitch of outlets in the high intensity ink ejection part is larger than that in the low intensity ink ejection part. Thus, manufacturing cost of the apparatus is reduced. With respect to each gray level in a middle grayscale range, if a tint image is recorded with the high intensity ink, a spatial frequency of this tint image is lower than that of a tint image recorded with the low intensity ink. By the above image recording control, even if the high intensity ink ejection part includes an abnormal outlet where a flight direction of droplet is abnormal, streak unevenness in a color halftone image can be suppressed.
1. An image recording apparatus using an inkjet mechanism, for recording a halftone image on an object, comprising:
a first ejection part having a plurality of first outlets for ejecting droplets of low intensity ink toward an object;
a second ejection part having a plurality of second outlets for ejecting droplets of high intensity ink toward said object;
a moving mechanism for moving said object relative to said first ejection part and said second ejection part; and
a controller for controlling ejection of ink from said first ejection part and said second ejection part in synchronization with relative movement of said object; wherein
with respect to a direction which is orthogonal to a moving direction of said object by said moving mechanism and which is parallel with a recording surface of said object, a pitch of said plurality of second outlets is larger than a pitch of said plurality of first outlets,
under control of said controller, with respect to each gray level included in a predetermined middle grayscale range of image density, if a tint image is recorded with said high intensity ink, a spatial frequency of said tint image is lower than a spatial frequency of a tint image recorded with said low intensity ink, and with respect to each gray level which is lower than at least said middle grayscale range, dots each of which is a minimum unit of dot formation with said low intensity ink are randomly disposed on said object while being away from one another and grayscale representation is made with a number density of said dots.
2. The image recording apparatus according to claim 1 , wherein
said high intensity ink is yellow ink.
3. The image recording apparatus according to claim 1 , wherein
said high intensity ink is light cyan ink or light magenta ink.
4. The image recording apparatus according to claim 1 , wherein
said controller comprises:
a memory which stores threshold matrices each of which is a two dimensional array of a plurality of threshold values; and
a halftone image generator for generating data of a halftone image to be recorded, by comparing original image data with said threshold matrices.
5. The image recording apparatus according to claim 4 , wherein
under control of said controller, with respect to each gray level included in a range from zero to a transition value lower than said middle grayscale range, dots each of which is a minimum unit of dot formation with said high intensity ink are randomly disposed on said object while being away from one another and grayscale representation is made with a number density of said dots, and with respect to gray levels which are higher than said transition value, a number density of centers of dots with said high intensity ink is constant and grayscale representation is made with sizes of said dots.
6. The image recording apparatus according to claim 1 , wherein
a halftone image is recorded on said object by one movement of said first ejection part and said second ejection part relative to said object by said moving mechanism.
7. The image recording apparatus according to claim 2 , wherein
a halftone image is recorded on said object by one movement of said first ejection part and said second ejection part relative to said object by said moving mechanism.
8. The image recording apparatus according to claim 3 , wherein
a halftone image is recorded on said object by one movement of said first ejection part and said second ejection part relative to said object by said moving mechanism.
9. The image recording apparatus according to claim 4 , wherein
a halftone image is recorded on said object by one movement of said first ejection part and said second ejection part relative to said object by said moving mechanism.
10. The image recording apparatus according to claim 5 , wherein
a halftone image is recorded on said object by one movement of said first ejection part and said second ejection part relative to said object by said moving mechanism.
11. An image recording method using an inkjet mechanism, of recording a halftone image on an object, comprising the steps of:
a) moving an object relative to a first ejection part and a second ejection part;
b) ejecting droplets of low intensity ink toward said object from a plurality of first outlets of said first ejection part in parallel with said step a); and
c) ejecting droplets of high intensity ink toward said object from a plurality of second outlets of said second ejection part in parallel with said step a); wherein
with respect to a direction which is orthogonal to a moving direction of said object and which is parallel with a recording surface of said object, a pitch of said plurality of second outlets is larger than a pitch of said plurality of first outlets,
under ejection control of droplets of ink in said steps b) and c), with respect to each gray level included in a predetermined middle grayscale range of image density, if a tint image is recorded with said high intensity ink, a spatial frequency of said tint image is lower than a spatial frequency of a tint image recorded with said low intensity ink, and with respect to each gray level which is lower than at least said middle grayscale range, dots each of which is a minimum unit of dot formation with said low intensity ink are randomly disposed on said object while being away from one another and grayscale representation is made with a number density of said dots.
12. The image recording method according to claim 11 , wherein
said high intensity ink is yellow ink.
13. The image recording method according to claim 11 , wherein
said high intensity ink is light cyan ink or light magenta ink.
14. The image recording method according to claim 11 , wherein
under said ejection control, with respect to each gray level included in a range from zero to a transition value lower than said middle grayscale range, dots each of which is a minimum unit of dot formation with said high intensity ink are randomly disposed on said object while being away from one another and grayscale representation is made with a number density of said dots, and with respect to gray levels which are higher than said transition value, a number density of centers of dots with said high intensity ink is constant and grayscale representation is made with sizes of said dots.
15. The image recording method according to claim 11 , wherein
a halftone image is recorded on said object by one movement of said first ejection part and said second ejection part relative to said object.
16. The image recording method according to claim 12 , wherein
a halftone image is recorded on said object by one movement of said first ejection part and said second ejection part relative to said object.
17. The image recording method according to claim 13 , wherein
a halftone image is recorded on said object by one movement of said first ejection part and said second ejection part relative to said object.
18. The image recording method according to claim 14 , wherein
a halftone image is recorded on said object by one movement of said first ejection part and said second ejection part relative to said object.