JPH05258053A - Picture quality improvement control system for image forming device - Google Patents

Abstract

PURPOSE:To prevent generating the deterioration of a picture quality by control ling the presence/absence of picture quality improvement corresponding to the characteristic of an image concerning a picture quality improvement system for an image forming device used for improving the picture quality of a record ing image by a laser printer, LED printer, a liquid-crystal printer, etc. CONSTITUTION:When an image improving processing means 14 improves the picture quality by detecting a part where a jagger being the unevenness of an image edge part from an input bit map image, an image detection means 10 detects the kind of an image in fear of the deterioration of the image caused by improving the picture quality at the time of inputting the image to judge an area which is not to be improved its image. At the time of record output, an image improvement specifying means 12 switches whether to improve the picture quality or not in accordance with the kind of the input image and the area so as to suppress the unnecessary improvement of the picture quality, paticularly to prevent the deterioration of the picture image along with the improvement of the picture quality which can be seen in a KANJI (chinese character) pattern and a garadation image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus for performing high resolution recording for high quality recording, and more particularly to a laser printer and an LED.
The present invention relates to an image quality improvement control system of an image forming apparatus used for improving the image quality of a recorded image by a printer, a liquid crystal printer, or the like.

[0002]

2. Description of the Related Art Conventionally, for example, a laser printer used as an image forming apparatus is currently 240 dpi or 300 dpi.
dpi is the mainstream. Therefore, many of the image signals output from the computer are compatible with 240 dpi and 300 dpi. However, 240 dpi or 300 dpi
The i printer has a defect that the unevenness of the image edge portion known as jaggies shown in FIG.

In order to eliminate this drawback, the pixel density should be increased. However, if the pixel density is increased extremely simply, in addition to the cost increase of the printer due to the higher accuracy of the processor, for example, (1) the bitmap font for 300 dpi cannot be used, (2) it is widely distributed. I cannot use an input device such as a 300 dpi scanner
(3) There is a drawback that application software for 300 dpi cannot be used.

By the way, in the laser printer, it is difficult to increase the pixel density in the sub-scanning direction, that is, to increase the pitch of the paper feed / drum feed, and even if it is possible, the cost will be high. On the other hand, in order to increase the pixel density in the main scanning direction, it suffices to increase the frequency for modulating the laser light,
It is relatively easy and can be realized at low cost.

Therefore, as shown in FIG. 6, there has been proposed a method for improving the image quality by doubling the dot positioning accuracy in the main scanning direction and changing the size of one dot in 12 steps ( (U.S. Pat. No. 4,847,641). According to this method, the pixels of the image 90 input to the FIFO bitmap buffer 101 are cut out in a window 11 having a predetermined size, and compared with a reference pattern of a tenan plate 102 written in a ROM in advance, and a reference pattern is obtained. When they match, the position and size of the corresponding pixel are corrected as shown in FIG.

In the example of FIG. 5B, in order to reduce the jaggies at an angle close to the horizontal line, the original one dot is made up of two dots at the top and bottom to improve. That is, the size of the upper and lower two dots is made smaller than the original size of the dot, and the sizes of the upper and lower dots are changed so that the barycentric position of the two dots is positioned between the original two dot positions. Control. As a result, dot collapse at the intersection is reduced.

[0007]

By the way, in the recorded image of the printer, character images such as alphabets, symbols, hiragana, katakana, kanji, etc., and images such as straight line, curved line, graphic image of gradation, gradation image, etc. There is an image. Character image information is usually sent from a higher-level device such as a computer to a printer, and is expanded and recorded in a bitmap inside the printer. In addition, the graphic image is sent without changing the code information in which each element is represented by a vector or the bitmap information. In many cases, the vectorized code information is expanded into bitmap data on the memory, and the bitmap information is recorded as it is in the printer. The image image is sent as a bitmap image. This is also recorded by the printer device as it is.

According to the conventional image quality improving method shown in FIGS. 5 and 6, in our research, relatively simple images such as alphabet, hiragana, katakana, straight line, curved line, etc.
It has the effect of improving the image quality, and the image quality hardly deteriorates. On the other hand, in complicated figures such as kanji and gradation images, for example, as can be seen by comparing the improvement in FIG. 7A and the improvement in FIG. Is also improved and the image quality may deteriorate.

[0009] Specifically, among the elements forming the kanji, a simple straight line portion has an image quality improving effect. However, the part where lines and points are compounded is regarded as a part of a continuous straight line, and an extra improvement is made. For example, a small dot is added to a portion that should not be present, or a dot that should not be moved is moved, so that the image quality is deteriorated.
Further, the gradation image is expressed by area gradation combining a plurality of dots, but as a result of the improvement of the image quality, the gradation level changes, so that pseudo contours may occur and the image quality may deteriorate.

The present invention has been made in view of such conventional problems, and the image quality of an image forming apparatus is controlled so as to prevent the deterioration of the image quality by controlling the presence or absence of the image quality improvement according to the property of the image. It is intended to provide an improved control method.

[0011]

FIG. 1 illustrates the principle of the present invention. As shown in FIG. 1, the image quality improvement control method for an image forming apparatus according to the present invention detects the property of an input image and determines whether or not to improve the image quality for each image area of different types. When the input image is recorded and output, the image quality improvement suppression means 12 that does not output the image quality improvement suppression signal in the area where the image quality is improved and outputs the image quality improvement suppression signal in the area where the image quality is not improved, and the image quality improvement suppression signal An image quality improvement processing unit 14 is provided which prohibits the image quality improvement operation in a certain case and performs the image quality improvement operation when there is no image quality improvement suppression signal, and switches the image quality improvement processing according to the property of the input image.

Here, the image detecting means 10 detects a kanji area as an image area in which the image quality is not improved, and the image quality improvement designating means 12 outputs an image quality improvement suppressing signal at the time of recording and outputting the kanji area to output the image quality improving processing means 14. The image quality improvement operation by is prohibited. Further, the image detection means 10 further detects the size of the kanji and judges that the image quality is not improved in the case of a kanji larger than a predetermined size, and the image quality improvement designating means 12 suppresses the image quality improvement when recording and outputting the kanji area. The image quality improving processing means 14 causes the image quality improving operation to be performed without outputting a signal.

Further, the image detecting means 10 detects an area of the gradation image as an image area in which the image quality is not improved, and the image quality improvement designating means 12 outputs an image quality improvement suppressing signal when recording and outputting the gradation image area. The image quality improvement operation by the image quality improvement processing means 14 is prohibited. The image quality improvement processing means 14 cuts out the input image developed into bit map data into a predetermined pattern, and compares it with a predetermined reference pattern for improving the image quality.
When the two match, a predetermined image quality improvement output corresponding to the reference pattern is performed. A neural network may be used as the image improvement processing means 14.

[0014]

According to the image quality improvement control system of the image forming apparatus according to the present invention having such a configuration, the portion in which the jaggies, which are the irregularities of the image edge portion, are detected from the input bitmap image and the correction is performed. When improving the image quality with
By detecting the image type that may deteriorate the image due to the image quality improvement and determining the area where the image improvement is not performed, it is possible to switch whether to perform the image quality improvement or not depending on the type and area of the input image when recording and outputting. Unnecessary image quality improvement can be suppressed, and in particular, deterioration of image quality due to image quality improvement as seen in Chinese character patterns and gradation images can be prevented.

[0015]

【Example】

[First Embodiment] FIG. 2 is a block diagram of an embodiment showing the first embodiment of the present invention.

In FIG. 2, this embodiment shows an image expansion unit 1.
5, an image quality improvement designation unit 12, an image quality improvement processing unit 14, and an exposure control unit 24. The input image expansion unit 15
An image detection unit 10 that detects the type of an input image and determines whether or not to improve the image quality for each image region of a different type.
An image expansion unit 16 that expands image data from a higher-level device into a bitmap and a character font storage unit 18 that stores a character font that is expanded into bitmap data are provided.

The image quality improvement processing unit 14 comprises an input image cutout unit 20 and a pattern recognition / improvement signal generation unit 22. The image detection unit 10 is a unit that detects the property of the input image data 40, and detects the property of the image, that is, an alphabet, a Chinese character, a line drawing, a gradation image, etc., from the code information and the bitmap information sent from the host device or the like. Then, it is determined whether or not the image quality is deteriorated due to the image quality improvement. When the image quality is deteriorated in the determination regarding the presence or absence of the image quality improvement, the image type information 40 of the area causing the image quality deterioration is output to the image quality improvement designating unit 12.

Whether or not the image quality deteriorates depends on the image quality improvement control method in the image quality improvement processing unit 14 which will be described later. Although a relatively simple image has an effect of improving the image quality,
The image quality may deteriorate in a complicated pattern. That is,
A simple straight line portion has an image quality improving effect, but a portion where lines and dots are compounded is regarded as a part of a continuous straight line and extra improvement is performed, resulting in deterioration of image quality.

Therefore, when the input image data 40 is Chinese character information and gradation image information, it is determined that the image is deteriorated due to the image quality improvement, and the image type information 40 indicating the position of the image quality deterioration area is used as the information. Send to 12. When the input image data 40 is a Chinese character input by code information, the image expanding unit 16 reads the corresponding Chinese character pattern from the character font storage unit 18 and expands the bitmap data of the corresponding Chinese character. When the input information data 40 is a gradation image, it is converted into an area gradation pattern. Further, when the input image data 40 is bitmap data, the bitmap data is sent as it is. Further, the image expansion unit 16 outputs the expansion position information 44 of the image expanded into the bitmap data to the image quality improvement specifying unit 12 at the same time.

FIG. 3 is a block diagram of an embodiment of the image quality improvement designating section 12. In FIG. 3, the image quality improvement designating unit 12 includes a coordinate extracting unit 26, a memory 28, a coordinate reading unit 30, and a comparator 32.
Equipped with. When the input image shown in FIG. 4A is to be processed, for example, for the line A, the coordinate extraction unit 26 obtains the coordinate information of the start position of the Kanji region 34 and the coordinate information of the end position of the Kanji region from the image type information 40. The extracted coordinate information is stored in the memory 28. Similarly, for the line C, the coordinate information of the start position and the end position of the image area 36 as the gradation image is stored in the memory 28.

Subsequently, at the time of actual recording, the recording position information 46 sent from the image quality improvement processing unit 14 in synchronization with the fact that the developed bitmap image is added to the image improvement processing unit 14 and the memory. The start coordinates and the end coordinates of the image area stored in 28 are read by the coordinate reading unit 30 and then compared by the comparator 32. In this comparison, when the image recording position is between the start position and the end position stored in the memory 28, the comparator 32 outputs the image quality improvement suppression signal 50.

For example, as shown in FIG. 4B, the image quality improvement suppression signal 50 is output from the start coordinate to the end coordinate of the Chinese character area 34 when the A line is recorded, and the image area is also recorded when the C line is recorded. The image quality improvement suppression signal 50 is output from the start coordinate to the end coordinate of 36. Figure 2 again
The image quality improvement processing unit 14 will be described with reference to FIG.

The image cropping section 20 is provided with the bitmap image converted by the image expanding section 16. Here, the image cutout unit 20 cuts out the bitmap image in a size according to the window as follows. The image cutting unit 20
It consists of a shift register and a read control circuit from the memory. The bitmap image is read from the memory one dot at a time and stored in a shift register having a shape suitable for each image cutout. For example, the image is cut out into 9 dots (vertical direction) × 9 dots (horizontal direction). Each time the image data is sent dot by dot, the contents of the shift register are rewritten in the form of being shifted dot by dot.

The image cut out in each window is added to the next pattern recognition / improvement signal generation unit 22 as information of a signal line having one dot according to the number of dots included in each window. In the pattern recognition / improvement signal generation unit 22, for example, as shown in FIG. 6, the bitmap image cut out by the image cutout unit 20 and the template pattern prepared in advance are compared. The template pattern is a pattern for detecting jaggies (angle of straight line and generation interval) and for detecting dots near the jaggies generation point for improvement.

As a result of the comparison, if they match each other, the improved control signal 48 peculiar to the template pattern stored in advance corresponding to each detected pattern is obtained.
Is output. If they do not match, the non-improved control signal 48 is output. Here, the image quality improvement suppressing signal 50 from the image quality improvement designating unit 12 is added to the portion for outputting the control signal 48 of the pattern recognition / improvement signal generating unit 22,
While the image quality improvement suppression signal 50 is being applied, even if the cutout pattern and the template pattern match, the improved control signal is not output, but the control signal based on the bit pattern before the improvement is output. Therefore, even if a Chinese character or a gradation image is recorded, the deterioration of the image quality does not occur due to the suppression of the image quality improvement.

The exposure controller 24 controls the exposure timing and the exposure time of the laser light source so that the dot position and the dot size are in accordance with the control signal 48 from the pattern recognition / improvement signal generator 22. At this time, if the control signal 48 is improved, the dot position and dot size of the portion where jaggies such as diagonal lines are generated are changed, jaggies are reduced, and image quality is improved. [Second Embodiment] Next, a second embodiment of the present invention will be described. The second embodiment is characterized in that a neural network is used in the pattern recognition / improvement signal generation unit 22 of the image quality improvement processing unit 14 shown in FIG.

When a neural network is used for the pattern recognition / improvement signal generation unit 22, the image cutout unit 2 is used.
A set of information of the bitmap image obtained by 0 and the improved output is prepared as learning data, and the neural network is learned in advance using this learning data. This learning is to determine the coefficient of each neuron in the neural network according to the back propagation method, for example.

By thus learning the input image and the improved output in association with each other to determine the coefficient of each neuron, the desired improved output can be obtained even for an unlearned input pattern. The image quality can be improved with respect to various changes in the input image. Also in this case, the image quality improvement suppression signal 50 is added to the part where the improvement signal is output from the neural network, and when there is the image quality improvement suppression signal 50, the image quality improved control signal 48 is not issued and the image quality is not improved. Of course, when the image quality improvement suppression signal 50 does not exist, the image quality improved control signal 48 is validated to improve the image quality. [Third Embodiment] Next, a third embodiment of the present invention will be described.

The third embodiment is similar to the image detecting unit 10 shown in FIG.
When detecting a kanji pattern in, the size of the kanji itself is detected, and whether or not to improve the image quality is determined according to the size of the kanji. Explaining the reason for this, when the bitmap image is cut out with the size of the window in a certain area to improve the image quality, in the case of a large font, the complex part of the line of each element of the kanji is enlarged, so a simple pattern Can be regarded as Therefore, the image quality does not deteriorate when the image quality improving operation is performed. That is, in the case of a large character, the image after bit map expansion can be regarded as a part of a simple straight line or curve when cut out with a window.

Therefore, by determining in advance the condition in which the image quality does not deteriorate from the character size and resolution, it is determined that the image quality can be improved without deterioration for large Kanji characters, and the image quality improvement suppression signal is output. Try not to. Specifically, since information indicating the size of a character is sent at the same time as the code information from the upper-level device for the kanji, the image detection unit 10 detects the information on the size of the character and the kanji code. If the size is equal to or larger than the predetermined size, it is determined that the image quality is improved. If the size is smaller than the predetermined size, it is determined that the image quality is not improved, and it is determined whether the image quality is improved or not and whether the image information is added is determined. This image quality improvement addition signal is sent to the image quality improvement specification unit 12, and when the image quality improvement addition signal is added, the image quality improvement suppression signal 50 is output when the kanji area is recorded. On the contrary, when the image quality improvement addition signal is not added, the image quality improvement suppression signal 50 is not output even in the Chinese character area.

[0031]

As described above, according to the present invention, the image is not improved when the area of the kanji or the gradation image is recorded. Therefore, the image quality of the kanji or the gradation image is deteriorated by the unnecessary image improvement. Therefore, it is possible to improve the Kase chamber only for the image area where the image quality is not deteriorated.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of the present invention.

FIG. 2 is a configuration diagram of an embodiment showing the first embodiment of the present invention.

FIG. 3 is a block diagram of an embodiment of an image quality improvement designation unit in FIG.

FIG. 4 is an explanatory diagram showing a processing operation of an image quality improvement designation unit in FIG.

FIG. 5 is an explanatory diagram showing a jaggy occurrence image before improvement and an image after improvement.

FIG. 6 is an explanatory diagram showing a conventional improvement process.

FIG. 7 is an explanatory diagram showing kanji images with and without image quality improvement.

[Explanation of symbols]

 10: Image detection means (image detection section) 12: Image improvement designation means (image improvement designation section) 14: Image improvement processing means (image improvement processing section) 16: Image expansion section 18: Character font storage section 20: Input image cutout Part 22: Pattern recognition / improvement signal generating part 24: Exposure control part 26: Coordinate extracting part 28: Memory 30: Coordinate reading part 32: Comparator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location G06G 7/60 (72) Inventor Jun Shio 1015 Ueodachu, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited (72) Inventor Tomohisa Mikami 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited (72) Inventor Yumiko Ito 1015, Uedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu (72) Inventor Iwai Shigeo 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Inside Fujitsu Limited

Claims (6)

[Claims] 1. An image detecting means 10 for detecting a property of an input image and determining whether or not to improve the image quality for each of different types of image areas, and an area for improving the image quality when recording and outputting the input image. The image improvement designating unit 12 that outputs the image quality improvement suppression signal in the area where the image quality improvement suppression signal is not output and the image quality is not improved.
And an image quality improvement processing unit 14 that prohibits the image quality improvement operation when there is the image quality improvement suppression signal and performs the image quality improvement operation when there is no image quality improvement suppression signal. An image quality improvement control method for an image forming apparatus characterized by switching. 2. The image quality improvement control system for an image forming apparatus according to claim 1, wherein said image detecting means 10 detects a kanji area as an image area for which image quality is not improved, and said image quality improvement designating means 12 An image quality improvement control system for an image forming apparatus, wherein an image quality improvement suppression signal is output at the time of recording and outputting a Chinese character area to prohibit the image quality improvement operation by the image quality improvement processing means 14. 3. The image quality improving control system for an image forming apparatus according to claim 2, wherein said image detecting means 10 further detects the size of the kanji and if the kanji is larger than a predetermined size, the image quality improving operation is performed. The image forming apparatus is characterized in that the image quality improvement designating means 12 does not output an image quality improvement suppressing signal at the time of recording and outputting the Chinese character area, and causes the image quality improvement processing means 14 to perform image quality improvement. Device image quality improvement control method. Image quality improvement method characterized by. 4. The image quality improvement control system for an image forming apparatus according to claim 1, wherein said image detecting means 10 detects a gradation image area as an image area where image quality is not improved, and said image quality improvement designating means. Reference numeral 12 denotes an image quality improvement control system for an image forming apparatus, which outputs an image quality improvement suppression signal at the time of recording and outputting the gradation image area to prohibit the image quality improvement operation by the image quality improvement processing means 14. 5. An image quality improvement control system for an image forming apparatus according to claim 1, wherein said image quality improvement processing means 14 cuts out an input image expanded into bit map data into a predetermined pattern and preliminarily improves the image quality. Compare with the defined reference pattern,
An image quality improvement control system for an image forming apparatus, which outputs a predetermined image quality improvement output corresponding to a reference pattern when the two match. 6. An image quality improvement control system for an image forming apparatus according to claim 5, wherein a neural network is used as said image improvement processing means.