Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-08-01
2002-01-29
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06341841
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printing system, which has a head for recording three or more different inks that are mixable to express hues in a predetermined range and records multi-tone images with the inks discharged from the head onto a printing object. The present invention also pertains to a method of recording images and an ink cartridge attachable to such a printing system.
2. Description of the related Art
Color printers with a head for recording a plurality of color inks on a printing object are widely used as an output device of a computer, which prints multi-color, multi-tone images processed by the computer. The following techniques are known as the method of recording inks on a printing object: a thermal transfer system that melts inks on ink ribbons and transfers the molten inks to a sheet of paper; an ink jet system that sprays colored ink solutions onto a sheet of paper; and an electrophotographic system that uses laser or another light to create a latent image on a photoconductive intermediary and transfers color toners to render the latent image visible. All such available techniques reproduce colors in a predetermined hue range by mixing a plurality of color inks. Three color inks, cyan, magenta, and yellow (CMY) are generally used for full-color printing.
There are several techniques available for printing multi-tone, multi-color images with a plurality of color inks. One available technique, which is adopted in the conventional printers, expresses the tone of a printed image by the density of dots (the frequency of appearance of dots per unit area) while fixing the size of dots formed on a sheet of paper by a stream of ink droplets. Another available technique adjusts the diameter of dots formed on a sheet of paper, in order to vary the density of ink per unit area. The advanced fine working of the head for creating ink particles has improved the density of dots formable per predetermined length or the variable range of dot diameters.
The improvement in printers has, however, so far been limited to 300 dpi through 720 dpi in printing density or resolution and several tens microns in particle diameter. This is significantly lower than the level of expression or resolution of silver photography, which has reached several thousands dpi on the film. Dots are sparsely formed in an area of low image density, that is, in an area of low density of dots to be printed. This increases the degree of granularity and makes the dots undesirably conspicuous. In printers for spraying liquid ink onto a paper, the total amount of ink sprayed per unit area is restricted by the absorbable volume of ink by the paper (generally referred to as ink duty). The restriction of ink duty is an issue to be cleared in printers using a plurality of color inks for color printing. The issue of ink duty is actualized especially in case that higher-density ink and lower-density ink are provided for the respective colors and the lower-density ink is used for printing low-tone areas in order to decrease the degree of granularity. Expression of a specific tone with the lower-density ink results in increasing the total amount of ink sprayed per unit area.
SUMMARY OF THE INVENTION
The object of the present invention is thus to regulate the density of a specific color ink and relieve the restriction of ink duty while keeping the quality of a printed image in a printing system with a head for spraying three or more different inks that are mixable to express hues in a predetermined range.
At least part of the above and the other related objects are realized by a first printing system having a head for recording at least three different color inks, which are mixable to express hues in a predetermined range, on a printing object, wherein a density ratio of a specific color ink, which has highest lightness against a fixed recording ratio among the at least three different color inks, to the other color inks is determined, in order to enable a color balance to be biased to the specific color ink having the highest lightness in case that the specific color ink and the other color inks have an identical recording ratio per unit area. The first printing system includes correction means for correcting a recording amount of the specific color ink having the highest lightness to a level that cancels the bias.
The present invention is also directed to a first image recording method corresponding to the first printing system. The first method records a multi-tone image by controlling a head that is able to record at least three different color inks, which are mixable to express hues in a predetermined range, and regulating a distribution of dots formed by the at least three different color inks based on tone signals regarding an original image to be printed. The first method includes the steps of:
determining a density ratio of a specific color ink, which has highest lightness against a fixed recording ratio among the at least three different color inks, to the other color inks, in order to enable a color balance to be biased to the specific color ink having the highest lightness in case that the specific color ink and the other color inks have an identical recording ratio per unit area; and
correcting a recording amount of the specific color ink having the highest lightness to a level that cancels the bias.
The first printing system (or the corresponding first image recording method) of the present invention has a head for recording at least three different color inks that are mixable to express hues in a predetermined range. The printing system forms dots of these color inks at a predetermined ratio, so as to record images of various hues and lightness (densities). In the first printing system, the color balance is biased to the specific color ink having highest lightness against a fixed recording ratio, in case that all the color inks have an identical recording ratio per unit area. The correction means then corrects the recording amount of the specific color ink having the highest lightness to a level that cancels the bias. Such correction ensures a normal color balance and reduces the recording amount of the specific color ink having the highest lightness and less effect of granularity in a low density area. This structure accordingly reduces the total amount of inks to be recorded while keeping the quality of a resulting image.
At least part of the above and the other related objects are also realized by a second printing system having a head for recording at least three different color inks, which are mixable to express hues in a predetermined range, on a printing object, wherein a density ratio of a specific color ink, which has lowest conspicuousness of granularity against a fixed recording ratio among the at least three different color inks, to the other color inks is determined, in order to enable a color balance to be biased to the specific color ink having the lowest conspicuousness of granularity in case that the specific color ink and the other color inks have an identical recording ratio per unit area. The second printing system includes correction means for correcting a recording amount of the specific color ink having the lowest conspicuousness of granularity to a level that cancels the bias.
The present invention is further directed to a second image recording method corresponding to the second printing system. The second method records a multi-tone image by controlling a head that is able to record at least three different color inks, which are mixable to express hues in a predetermined range, and regulating a distribution of dots formed by the at least three different color inks based on tone signals regarding an original image to be printed. The second method includes the steps of:
determining a density ratio of a specific color ink, which has lowest conspicuousness of granularity against a fixed recording ratio among the at least three different color inks, to the other color inks, in order to enable a color balance to be biased
Kakutani Toshiaki
Shimada Kazumichi
Nguyen Thinh
Seiko Epson Corporation
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