Method and apparatus for ink-jet gray-scale printing

Claim 2

An ink-jet printing apparatus using an ink-jet head having a plurality of ejection orifices, forming a pixel by ejecting ink through the ink-jet head toward a printing medium for performing printing with a set of the pixels, comprising: primary scanning means for moving the ink-jet head in a primary scanning direction; feeding means for feeding the printing medium in an auxiliary scanning direction different from the primary scanning direction; determining means for determining a number of ink droplets to be ejected through ejection orifices of the ink-jet head during a plurality of movements of the ink-jet head in the primary scanning direction so as to form respective pixels using ink droplets elected from different ejection orifices of the ink-let head, respectively, the number of ink droplets being determined in accordance with a half tone value of the respective pixels, and a remainder from division of a sum of (i) a value corresponding to a scanning cycle in which a predetermined election orifice is used in the primary scanning direction for forming the pixel among a plurality of scanning cycles, and (ii) a value corresponding to a position of the pixel in the primary scanning directions, by a number of the plurality of scanning cycles; and control means for controlling ejection of the number of ink droplets determined by said determining means at each pixel position in each scanning cycle in the primary scanning direction.

Claim 3

An ink-jet printing apparatus as claimed in claim 1, wherein a number of ink droplets A is determined by: A=(K(x, y)+(z/M+F(x)%S)/S wherein K(x, y) is a half tone value at a pixel position x,y (x and y respectively represent a position in the primary scanning direction and the auxiliary scanning direction), z is an ejection orifice number, M is a feeding amount of the printing medium expressed by a number of the ejection orifices, F(x) is a predetermined function of the pixel position x, S is a number of ejection orifices ejecting ink to form the pixel, the operator "%" represents derivation of remainder in division of an integer therebefore by an integer thereafter, and the operator "/" represents derivation of an integer quotient in division of an integer therebefore by an integer thereafter.

Claim 4

An ink-jet printing apparatus as claimed in claim 2, wherein F(x), the predetermined function of the pixel position x, is expressed by F(x)=x.

Claim 5

An ink-jet printing apparatus as claimed in claim 2, wherein F(x), the predetermined function of the pixel position x, is expressed by F(x)=2x.

Claim 6

An ink-jet printing apparatus as claimed in claim 2, wherein said ink-jet head generates a bubble in the ink utilizing a thermal energy and ejects ink associating with generation of the bubble.

Claim 7

An ink-jet printing apparatus as claimed in claim 1, using a black colored ink as the ink.

Claim 8

An ink-jet printing apparatus as claimed in claim 1, using a plurality of colors of ink as the ink.

Claim 9

An ink-jet printing apparatus as claimed in claim 1, wherein said ink-jet printing apparatus is usable with a copying apparatus.

Claim 10

An ink-jet printing apparatus as claimed in claim 1, wherein said ink-jet printing apparatus is usable with a facsimile apparatus.

Claim 11

An ink-jet printing apparatus as claimed in claim 1, wherein said ink-jet printing apparatus is usable with a terminal apparatus for a computer.

Claim 12

An ink-jet printing method for forming one pixel with m ink droplets (where m is an integer ≧2) using an ink-jet head having n ejection orifices (where n is an integer ≧2), comprising the steps of: providing an ink let head such that the n ejection orifices of the ink-jet head are arrayed in a direction perpendicular to a direction of relative movement of a printing medium and the ink-jet head, and such that each pixel is formed by ejecting m ink droplets through S different ejection orifices (where S is an integer corresponding to n/L excluding a fraction less than 1, and L is a number of election orifices corresponding to a distance of relative movement of the ink-jet head and the recording medium) for every relative movement between the ink-jet head and the printing medium; performing image formation of the pixel by ejecting T ink droplets according to a half tone data of the pixel (where T is an integer ≧m), the pixel being formed by ejecting (B+1) ink droplets (where B is an integer derived from T/S excluding a fraction less than 1) through ejection orifices up to an Ath numbered ejection orifice from an ejection orifice of a highest preferential order (where A is a remainder of T/S) and ejecting B ink droplets through (S-A) ejection orifices in a lower preferential order, when there is a preferential order for use of S different ejection orifices, and a remainder of T/S is present; and performing image formation of the pixel with T ink droplets by ejecting T/S ink droplets through S different ejection orifices, when the remainder of T/S is not present.

Claim 13

An ink-jet printing method for forming one pixel with m ink droplets (where m is an integer ≧2) using an ink-jet head having n ejection orifices (where n is an integer ≧2), comprising the steps of: providing an ink let head such that the n ejection orifices of the ink-jet head are arrayed in a direction perpendicular to a direction of relative movement of a printing medium and the ink-jet head, and such that each pixel is formed by ejecting m ink droplets through S different ejection orifices (where S is an integer corresponding to n/L excluding a fraction less than 1, and L is a number of election orifices corresponding to a distance of relative movement of the ink-jet head and the recording medium) for every relative movement between the ink-jet head and the printing medium; performing image formation of the pixel by ejecting T ink droplets according to a half tone data of the pixel (where T is an integer ≧m), the pixel being formed by ejecting (B+1) ink droplets (where B is an integer derived from T/S excluding a fraction less than 1) through ejection orifices up to an Ath numbered ejection orifice from an ejection orifice of a highest preferential order (where A is a remainder of T/S) and ejecting B ink droplets through (S-A) ejection orifices in a lower preferential order, when there is a preferential order for use of S different ejection orifices, and a remainder of T/S is present; and performing image formation of the pixel with T ink droplets by ejecting T/S ink droplets through S different ejection orifices, when the remainder of T/S is not present.

Claim 14

An ink-jet printing method as claimed in claim 11, further comprising the step of electing ink by generating a bubble in the ink utilizing thermal energy.