Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-08-27
2001-06-26
Rogers, Scott (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S451000, C358S451000, C358S461000, C347S184000
Reexamination Certificate
active
06252678
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to an image formation method and in particular to an image formation method effective for providing a record image of high quality.
2. Description of Related Art
In recent years, full-color laser beam printers and thermal transfer printers have been rapidly finding spreading use as output terminals of personal computers, workstations, etc. In this case, required performance includes the capability of outputting text data, line drawing data, and image data, namely, continuous-tone output is required.
As this kind of system, for example, a system disclosed in Unexamined Japanese Patent No. Hei 9-1866 is well known.
The system divides an image into a plurality of blocks, changes the input/output characteristics corresponding to the positions of pixels therein for each block, converts image data density level into density level to recorded dots, and changes and disperses the positions where dots of the same size are recorded for each block, thereby preventing appearance of structural pattern in the image such as moire.
Basically, the conventional system is a kind of a pseudo area gradation technique using a multilevel dither method having only less discrete density level. When, the configuration as described above is adopted, characteristics such as, size and, placement regularity of recorded dots is weakened as much as possible, thereby preventing appearance of structural pattern in the image such as moire.
In more detail, image data is converted from R(red), G(green), and B(blue) of brightness data into density data of three primary colors of C(cyan), M(magenta), and Y(yellow) for printing, then an under color is removed for preparing a black plate based on the density data, and C, M, Y, and BK (black) data is prepared. Further, correction processing such as masking is applied, then gradation processing is executed in such a manner that the pixels at the positions in the block described above are divided into odd and even lines and different gradation conversion table characteristics are applied to each of the lines.
However, in the system, the gradation conversion table characteristics are monotonous, thus occurrence of roughness is inevitable when low-density recorded pixels are formed on a white background.
The system assumes that a printed matter has stable characteristics. In fact, it is necessary to consider printing on a printed matter for which is hard to say that its characteristics are always stable. That is, with photosensitive material for thermal developing or photo-thermal-sensitive recording material, even if energy at the minimum level required for recording is given, the threshold as to whether or not color is developed varies due to variation in sensitivity caused by humidity, etc., and the print result becomes delicately different.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an image formation method which can also be used for printing on a printed matter which is hard to say that its characteristics are always stable and is effective for providing a high-quality recording image.
In order to achieve the above object, there is provided a method for forming an image comprising the steps of: dividing an inputted image into a plurality of unit areas; preparing at least five gradation conversion tables relating a gradation value of the inputted image to a dot generation energy value corresponding to a size of a dot to be printed; preparing a matrix dividing each of the unit areas into predetermined number of element areas; dividing each of the unit areas into a predetermined number of the element areas by means of the matrix; assigning one of the plurality of gradation conversion tables to each of the element areas in each of the unit area; and recording dots according to the dot generation energy value obtained from the assigned gradation conversion table, wherein the plurality of conversion tables are prepared in such a manner that there exists at least three converted energy values other than a minimum and a maximum energy value at an arbitrary density value in halftone density, and wherein the plurality of conversion tables are prepared in such a manner that a number of element areas in which the minimum value of the converted energy is assigned is more than half of the number of all the element areas when a minimum density level has the maximum value of the converted energy.
In the method, the inputted image data may include a plurality of color plate image data, and all the above steps may be executed with respect to each of the color plate image data. The plurality of color plate image data may be image data of cyan, magenta, yellow and black plates.
Here, there may be prepared at least three kinds of matrixes in which the numbers of the element areas arranged in one of the horizontal direction and the vertical direction thereof are different from each other.
With respect to one of the color plate image data, the assignment of the plurality of conversion tables to the each of the element areas are executed randomly. The one color plate image data is a color plate image data having the least density, specifically, the yellow color plate data.
In the method, with respect to the color plate image data other than the one color plate image data (e.g. the yellow color plate), the assignment of the plurality of conversion tables to the each of the element areas are executed based on a predetermined rule. The predetermined rule is different from each other in the color plate image data.
Accordingly, even if recorded pixels at low density are formed on a white background, occurrence of roughness can be decreased remarkably. Therefore, the image formation method can also be used for printing on a printed matter for which it is hard to say that characteristics thereof are always stable, and can provide a high-quality recording image.
REFERENCES:
patent: 5073966 (1991-12-01), Sato
patent: 5287209 (1994-02-01), Hiratsuka et al.
patent: 5394252 (1995-02-01), Holladay et al.
patent: 0 680 195 (1995-11-01), None
patent: 0 720 350 (1996-07-01), None
patent: 0 761 434 (1997-03-01), None
patent: 7-117359 (1995-05-01), None
patent: 9-1866 (1997-01-01), None
patent: 2608808 (1997-02-01), None
patent: WO 95/02938 (1995-01-01), None
Fuji Photo Film Co. , Ltd.
Rogers Scott
Sughrue Mion Zinn Macpeak & Seas, PLLC
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