US 6,439,682 B1 · Printing method, printing apparatus, and recording medium

Abstract

In a printing apparatus that enables at least three different types of dots to be created in different ink weights by at least two different inks having an identical hue but different densities, the halftone processing is carried out in an appropriate sequence and according to an appropriate technique, which are determined by taking into account both the dispersibility of dots and the processing speed. The method of the present invention determines the on-off state of six different types of dots, which have different ink densities and ink weights, in the sequence of the large deep dot, the medium deep dot, the small deep dot, the large light dot, the medium light dot, and the small light dot. The dots created by an identical ink are subjected to the determination for the on-off state in a consecutive manner. A dither method that utilizes the recording ratio set for each type of dot according to the tone data is adopted in the determination for the on-off state of the dot. The method determines the on-off state of a target dot, based on a corrected recording ratio. The corrected recording ratio is obtained by adding the recording ratios of all the dots previously subjected to the determination for the on-off state to the recording ratio of the target dot. For example, the sum of the recording ratios of the large deep dot, the medium deep dot, and the small deep dot and the recording ratio of the large light dot is used in the determination for the on-off state of the large light dot. This arrangement of the present invention effectively prevents the different types of dots, especially the dots created by the identical ink, from being created in an identical pixel in an overlapping manner. One modified structure determines the on-off state of the small light dot by an error diffusion method. This improves the picture quality of the resulting printed image.

Claims24

Dependent claims

A method of printing a multi-tone image as a distribution of dots created with a head, said head handling at least two different inks that have an identical hue but different densities and creating at least three different types of dots, which include at least two different types of dots that have different ink weights and are created by at least one ink among the at least two different inks, to be created on a printing medium, said method comprising the steps of:

(a) inputting tone data of an image to be printed;
(b) successively determining on-off state of the at least three different types of dots with respect to each pixel in a preset sequence, the preset sequence comprising a specific order of ink weight in which the at least two different types of dots created by the identical ink are consecutively subjected to the determination for the on-off state;
and
(c) driving said head based on results of the determination carried out in said step (b), so as to create the respective types of dots,
wherein said step (b) comprises the steps of:
(b1) setting a recording ratio regarding each of the at least three different types of dots, based on the tone data;
(b2) comparing the recording ratio set in said step (b1) for a specific dot, which is a first object of the determination, with a threshold value read from a dither matrix that has been provided in advance and determining on-off state of the specific dot based on a result of the comparison;
and
(b3) comparing a corrected recording ratio with the threshold value and determining on-off state of another dot, which is a second or subsequent object of the determination, based on a result of the comparison with respect to pixels in which all the dots previously subjected to the determination for the on-off state are set in the off state, said corrected recording ratio being obtained by correcting the recording ratio set in said step (b1) for the another dot with the recording ratios of all the dots previously subjected to the determination for the on-off state.

6 more elements

A method of printing a multi-tone image as a distribution of dots created with a head, said head handling at least two different inks that have an identical hue but different densities and creating at least three different types of dots, which include at least two different types of dots that have different ink weights and are created by at least one identical ink among the at least two different inks, to be created on a printing medium, said method comprising the steps of:

(a) inputting tone data of an image to be printed;
(b) dividing the at least three different types of dots according to a preset classification into a first group including a plurality of different types of dots having higher density evaluation values and a second group including at least one type of dot having a lower density evaluation value;
(c) successively determining on-off state of the plurality of different types of dots in said first group with respect to each pixel in a preset sequence, the preset sequence comprising a specific order of ink weight in which the at least two different types of dots created by the identical ink are consecutively subjected to the determination for the on-off state;
(d) determining on-off state of the at least one type of dot in said second group by an error diffusion method based on correction data, the correction data being obtained by correcting the tone data with density errors occurring due to the on-off state of the plurality of dots in said first group;
and
(e) driving said head based on results of the determinations carried out in said step (c) and said step (d), so as to create the respective types of dots,
wherein said step (c) comprises the steps of:
(c1) setting a recording ratio regarding each of the plurality of different types of dots in said first group, based on the tone data;
(c2) comparing the recording ratio set in said step (c1) for a specific dot, which is a first object of the determination, with a threshold value read from a dither matrix that has been provided in advance and determining on-off state of the specific dot based on a result of the comparison;
and
(c3) comparing a corrected recording ratio with the threshold value and determining on-off state of another dot, which is a second or subsequent object of the determination, based on a result of the comparison with respect to pixels in which all the dots previously subjected to the determination for the on-off state are set in the off state, said corrected recording ratio being obtained by correcting the recording ratio set in said step (c1) for the another dot with the recording ratios of all the dots previously subjected to the determination for the on-off state.

8 more elements

A printing apparatus that enables a multi-tone image to be printed as a distribution of dots created with a head, said head handling at least two different inks that have an identical hue but different densities and creating at least three different types of dots, which include at least two different types of dots that have different ink weights and are created by at least one ink among the at least two different inks, to be created on a printing medium, said printing apparatus comprising:

an input unit that inputs tone data of an image to be printed;
a dither determination unit that successively determines on-off state of the at least three different types of dots with respect to each pixel in a preset sequence, the preset sequence comprising a specific order of ink weight in which the at least two different types of dots created by the identical ink are consecutively subjected to the determination for the on-off state;
and
a dot creation unit that drives said head based on results of the determination carried out by said dither determination unit, so as to create the respective types of dots,
wherein said dither determination unit comprises:
a memory unit in which a relationship between tone data and a recording ratio regarding each of the at least three different types of dots is stored;
a setting unit that refers to said memory unit and sets the recording ratio of each of the at least three different types of dots corresponding to the input tone data;
and
a dot creation determination unit that compares a corrected recording ratio of a target dot with a threshold value stored in a dither matrix that has been provided in advance, said corrected recording ratio being obtained by correcting the recording ratio of the target dot set by said setting unit with the recording ratios of all the dots previously subjected to the determination for the on-off state, said dot creation determination unit then determining on-off state of the target dot with respect to pixels in which all the dots previously subjected to the determination for the on-off state are set in the off state, based on a result of the comparison.

6 more elements

a storage unit that stores divisions, which are obtained by dividing the at least three different types of dots according to a preset classification into a plurality of different types of dots having higher density evaluation values and at least one type of dot having a lower density evaluation value;
an input unit that inputs tone data of an image to be printed;
a dither determination unit that successively determines on-off state of the plurality of different types of dots having the higher density evaluation values with respect to each pixel in a preset sequence, the preset sequence comprising a specific order of ink weight in which the at least two different types of dots created by the identical ink are consecutively subjected to the determination for the on-off state;
an error diffusion determination unit that determines on-off state of the at least one type of dot having the lower density evaluation value by an error diffusion method based on correction data, the correction data being obtained by correcting the tone data with density errors occurring due to the on-off state of the plurality of dots having the higher density evaluation values;
and
a dot creation unit that drives said head based on results of the determinations carried out by said dither determination unit and said error diffusion determination unit, so as to create the respective types of dots,
wherein said dither determination unit comprises:
a memory unit in which a relationship between tone data and a recording ratio regarding each of the plurality of different types of dots having the higher density evaluation values is stored;
a setting unit that refers to said memory unit and sets the recording ratio of each of the plurality of different types of dots having the higher density evaluation values corresponding to the input tone data;
and
a dot creation determination unit that compares a corrected recording ratio of a target dot with a threshold value stored in a dither matrix that has been provided in advance, said corrected recording ratio being obtained by correcting the recording ratio of the target dot set by said setting unit with the recording ratios of all the dots previously subjected to the determination for the on-off state, said dot creation determination unit then determining on-off state of the target dot with respect to pixels in which all the dots previously subjected to the determination for the on-off state are set in the off state, based on a result of the comparison.

8 more elements

A recording medium in which a program for enabling a multi-tone image to be printed by a printing apparatus is recorded in a computer readable manner, said printing apparatus comprising at least two different inks that have an identical hue but different densities and creating at least three different types of dots, which include at least two different types of dots that have different ink weights and are created by at least one ink among the at least two different inks, to be created on a printing medium,

said program comprising:
a program code that causes a computer to successively determine on-off state of the at least three different types of dots with respect to each pixel in a preset sequence, the preset sequence comprising a specific order of ink weight in which the at least two different types of dots created by the identical ink are consecutively subjected to the determination for the on-off state,
said program code causing the computer to actualize the functions of:
setting a recording ratio regarding each of the at least three different types of dots, based on tone data of an original image;
comparing the recording ratio of a specific dot, which is a first object of the determination, with a threshold value read from a dither matrix that has been provided in advance and determining on-off state of the specific dot based on a result of the comparison;
and
comparing a corrected recording ratio with the threshold value and determining on-off state of another dot, which is a second or subsequent object of the determination, based on a result of the comparison with respect to pixels in which all the dots previously subjected to the determination for the on-off state are set in the off state, said corrected recording ratio being obtained by correcting the recording ratio of the another dot with the recording ratios of all the dots previously subjected to the determination for the on-off state.

4 more elements

said program comprising:
a first program code that causes a computer to divide the at least three different types of dots according to a preset classification into a plurality of different types of dots having higher density evaluation values and at least one type of dot having a lower density evaluation value;
a second program code that causes the computer to successively determine on-off state of the plurality of different types of dots having the higher density evaluation values with respect to each pixel in a preset sequence, the preset sequence comprising a specific order of ink weight in which the at least two different types of dots created by the identical ink are consecutively subjected to the determination for the on-off state;
and
a third program code that causes the computer to determine on-off state of the at least one type of dot having the lower density evaluation value by an error diffusion method based on correction data, the correction data being obtained by correcting the tone data with density errors occurring due to the on-off state of the plurality of dots having the higher density evaluation values,
said second program code causing the computer to actualize the functions of:
setting a recording ratio regarding each of the plurality of different types of dots having the higher density evaluation values, based on tone data of an original image;
comparing the recording ratio of a specific dot, which is a first object of the determination, with a threshold value read from a dither matrix that has been provided in advance and determining on-off state of the specific dot based on a result of the comparison;
and
comparing a corrected recording ratio with the threshold value and determining on-off state of another dot, which is a second or subsequent object of the determination, based on a result of the comparison with respect to pixels in which all the dots previously subjected to the determination for the on-off state are set in the off state, said corrected recording ratio being obtained by correcting the recording ratio of the another dot with the recording ratios of all the dots previously subjected to the determination for the on-off state.

7 more elements

Dependencies are inferred from the claim text.

Printing method, printing apparatus, and recording medium

Life of this patent

Printing method, printing apparatus, and recording medium

Life of this patent

Abstract

Claims24