Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
2002-08-30
2004-08-24
Rogers, Scott (Department: 2626)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S003260, C382S205000, C382S216000, C382S218000, C382S269000
Reexamination Certificate
active
06781718
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image correcting method and an image correcting apparatus for improving the quality of a dot printed image in an image forming apparatus such as a printer and, more particularly, to a dot image correcting method, and apparatus, which stores correction data corresponding to a correction dot pattern in a window, detects while scanning a dot image whether or not the dot pattern in the window coincides with the correction dot pattern, and if the coincidence is detected, corrects the dot image in accordance with the correction data.
DESCRIPTION OF THE RELATED ART
In a digital printer such as a laser beam printer, or in a display such as a liquid crystal display, CRT or the like, an image is formed with dots. Usually, the positions of the dots and the dot diameters are controlled so as to remain approximately constant. However, when an oblique line is printed in a dot image, a step called a jaggy appears at the edge portion, and a processing called a smoothing process is performed by detecting a jaggy edge portion in a dot image and correcting the edge portion so as to change smoothly,
FIG. 1
is a view showing the construction of a dot image correcting apparatus for performing the above-described correction. In
FIG. 1
, reference number
11
denotes an image memory for storing dot image data, and
12
denotes a dot image correcting apparatus. The dot image correcting apparatus
12
comprises, as shown in the Figure, a line buffer
21
that temporarily stores dot image data for a few lines which are stored in the image memory
11
, a window register
23
for storing the window portion denoted by reference numeral
22
, a coincidence detection circuit
24
that detects whether or not the dot pattern in the window register
23
coincides with a preset correction dot pattern, and a correction data table
25
that stores correction data corresponding to the correction dot pattern and outputs the correction data in accordance with the coincidence detection result from the coincidence detection circuit
24
.
The line buffer
21
has the memory capacity for storing image data for a few lines, sequentially stores image data read from the image memory
11
, and successively shifts the range of lines to be stored. The window register
23
temporarily stores data for each dot from the line buffer
21
in the range where comparison of the dot pattern is performed, and outputs them to the coincidence detection circuit
24
. When the comparison in the coincidence detection circuit
24
has been done, the window register
23
shifts the position of the window to the right by one dot. This operation is repeated from the left end to the right end of the line buffer
21
, and when completed, the line buffer
21
erases the image data for the top line and stores the image data for the next line anew. Reference number
23
A denotes the dot at the center of the window
23
, and this dot is referred to as an observation dot. In other words, the position of the observation dot
23
A is successively scanned on the image to detect coincidence with the correction dot pattern. Correction data indicate how to correct the observation dot
23
A.
FIGS. 2A and 2B
are views showing the correcting method for correcting a jaggy. As shown in
FIG. 2A
, a jaggy occurs at the dot denoted by reference number
27
. In this case, the dot
27
is shifted to the left by half pitch, the dot above the dot
27
is shifted to the left by an amount less than half pitch, and the dot beneath the dot
27
is shifted to the right by an amount less than half pitch. Shifting the position of a dot is performed, for example, in the case of a laser beam printer, by shifting the modulating signal of the laser,
There is a case where the coincidence of a pattern is not detected, and pattern recognition is performed by processing the dot pattern in the window register
23
with an operation circuit
26
to obtain correction data. In such a construction, however, there is a problem that, as the pattern is stored in the operation circuit
26
to detect the coincidence, size of the operation circuit becomes large and requires longer time for operation.
FIG. 4
is a view showing an example of the construction of the window register
23
and the coincidence detection circuit
24
and the correction data table
25
of FIG.
1
. The coincidence detection circuit is well known and, therefore, a detailed explanation thereof is omitted, Basically, a signal line in which signal indicating the value of each dot is output is taken out from the window register
23
, and is arranged in parallel in the coincidence detection circuit
24
so as to form a first wiring array. A second wiring array with number of lines corresponding to the number of correction dot patterns is formed so as to intersect the first wiring array. In each signal line of the second wiring array, a gate is provided at the intersection corresponding to each correction data pattern, When a dot pattern output from the window register
23
coincides with correction dot pattern of a second wiring, only the output from the wiring is modified and the correction data register
251
storing the corresponding correction data is activated to output the correction data via a selector
252
. When there is no coincident correction dot pattern, no correction data register
251
is activated, and therefore no correction data is output. In practice, another signal line is provided for each signal line of the first wiring array, and an inverted signal is applied to this signal line. One of this set of signal lines is connected to the gate of the transistor connected to each signal line of the second wiring array. When the transistor is connected to a high potential, each signal line of the second wiring array is connected to ground via a resistor.
Japanese Unexamined Patent Publication (Kokai) No. 07-205483 discloses an image processing method and apparatus wherein a smoothing process is performed efficiently at high speed by the primary detection of an edge corner and by computing the number of continuous dots extending vertically and horizontally from the primary detection point as starting point to perform correction processing. However, this patent publication discloses only a smoothing process and does not disclose correction of any portion other than jagged portions, nor disclose correction of line width as described later.
Conventionally, only a smoothing process has been performed. However, with recent advances in the performance of an image forming apparatus such as a printer, an improvement in image quality by performing correction processes other than the smoothing process is being increasingly required, In particular, more precise control of the size and position of a dot, than has been possible before, is required for such a repeating pattern as a single thin line, an outlined thin line, a repetition of thin line, and so forth. In the case of an isolated thin line, for example, processing for increasing line width is performed because a printing process may adversely affect the visibility of the line, Thus, in the case of a black line of 1 dot, correction is performed so as to increase the dot diameter, and in the case of white line of 1 dot, correction is performed so as to decrease the dot diameter on both sides of the line. This correction is performed by varying the width of the modulation signal in the case of a laser printer, and by varying the amount of ink in the case of an ink jet printer. In such a case, an isolated thin line is stored as a correction dot pattern and, by comparison with a dot pattern in the window, it is detected whether or not the dot pattern is an isolated thin line.
Japanese Unexamined Patent Publication (Kokai) No. 11-216910 discloses an image forming apparatus which corrects a dot diameter in accordance with a dot pattern. Also in this case, coincidence with the correction dot pattern needs to be detected, and the same coincidence detection circuit as shown in
FIG. 4
is used for this purpose.
In or
Fuji 'Xerox Co., Ltd.
Rogers Scott
Westerman Hattori Daniels & Adrian LLP
LandOfFree
Image correction method and image correcting apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image correction method and image correcting apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image correction method and image correcting apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3284455