JP3545464B2 - Composite device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a multifunction peripheral having the functions of a digital copying machine and a facsimile machine.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a digital copying apparatus that prints image data read by a document sensor such as a line image sensor on paper using laser light and records it has been put to practical use, and has begun to be used as a multifunction apparatus combined with a facsimile apparatus.
Such a multifunction device has the functions of a copying device and a facsimile device by itself, so it is cheaper than purchasing a copying device and a facsimile device separately, and because it does not take up installation space, it is increasingly used. It has come to be.
[0003]
Conventional multifunction devices often have a facsimile function added based on a digital copying device. FIG. 9 is a block diagram of main functions related to digital copy processing of a conventional multifunction peripheral, and FIG. 10 is a block diagram of main functions related to facsimile transmission processing of the multifunction peripheral.
[0004]
As shown in FIG. 9, in a digital copying process in a conventional multifunction peripheral, an image of a document is read by a document sensor such as a CCD and a video signal of the read multi-valued image data is subjected to shading correction by a shading correction circuit 20. The spatial filter processing circuit 21 corrects the resolution by MTF correction.
Further, gradation correction by gamma correction is performed by a gamma correction look-up table (LUT) 22, and thereafter, a scaling process is performed by an electric scaling unit 23, and the result is sent to a recording processing unit for printing.
[0005]
This uses a multi-level recording method in which multi-level image data (multi-level image signal) read from a document is directly guided to a multi-level modulation unit of a recording processing unit. In the digital copy processing using such a method, the reproducibility of the image of the original is important, and the resolution is not corrected by the spatial filter processing (MTF correction processing) before scaling the multi-valued image data. This is because when the image data is enlarged, the MTF correction does not work well and the resolution becomes poor, which may cause image blur.
[0006]
In addition, when the γ correction is performed on the multi-valued image data before the MTF correction processing is performed, and the input characteristics such as the cut of the background noise are suddenly changed by the γ correction, the changing portion of the γ curve in the γ correction is reduced. This is because the MTF correction is performed so as to emphasize the image, and there is a possibility that a streak such as a contour line is formed in the vicinity of the all-white clamped portion on the copy image and the image quality is deteriorated.
[0007]
On the other hand, in a facsimile transmission process in a conventional multifunction peripheral, as shown in FIG. 10, a document image is read by a document sensor such as a CCD, and a video signal of the read multi-valued image data is subjected to shading correction by a shading correction circuit 30. I do.
[0008]
Then, the spatial filter / pictogram separation processing unit 31 performs resolution correction by MTF correction, further separates the character area and the picture area of the image data, and converts the image data of the character area into a character γ correction look-up table (LUT) 32. Then, the image data of the picture area is sent to the picture γ correction look-up table (LUT) 35.
[0009]
The character γ correction LUT 32 performs gradation correction by γ correction on the image data of the character area, and then performs scaling by the electric scaling unit 33, and converts the image data into binary data by the binarization unit 34. This is sent to the pictograph combining section 38.
[0010]
Further, the picture γ correction LUT 35 performs gradation correction by γ correction on the image data of the picture area, and thereafter, the electric magnification processing section 36 changes the magnification, and the binarization processing section 37 converts the image data into binary data. And sends it to pictogram combining section 38.
Then, the binarized data of the character area and the pattern area are synthesized by the pictorial character synthesizing section 38, and the process proceeds to the facsimile transmission process.
[0011]
As described above, when multi-valued image data is binarized and facsimile-transmitted, the character portion is less likely to be blurred or resolved by performing pseudo halftone processing by dither processing or error diffusion processing during halftone.
[0012]
Therefore, if the pictorial character separation processing for separating the character part and the picture part of the image data is performed by the same functional unit as the spatial filter and the dither processing or the error diffusion processing is applied only to the picture area, the MTF processing is first performed on the image data. Since (filter processing) is included, there is no adverse effect caused by performing the MTF processing after the γ correction or the scaling processing.
[0013]
[Problems to be solved by the invention]
However, the conventional multifunction peripheral has a problem that the circuit configuration is large and the cost is high in order to improve both the quality of the image to be copied and the quality of the image to be transmitted by facsimile. For example, as shown in FIG. 10, in the facsimile transmission process, there are two processing systems from the spatial filter / pictogram separation processing unit 31 to the pictogram synthesizing unit 38, and the number of processing function units increases.
[0014]
The present invention has been made in view of the above, and an object thereof to improve the image quality of the image when enlarged copying without increasing the scale of the circuit configuration.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a multifunction device according to the present invention includes: an image reading unit that reads an image of a document; a first gradation correction unit that corrects a gradation of multi-valued image data read by the unit; Scaling means for scaling the image data corrected by the means, MTF correction / pictogram separation means for MTF- correcting the resolution of the image data scaled by the means to separate it into a character area and a picture area, Means for converting each of the multi-valued image data of the character area and picture area separated by the means into binary data, means for combining each of the binary data converted by the means, and facsimile transmission; A second gradation correction means for correcting the gradation of the multi-valued image data of the entire area whose resolution has been corrected by the MTF correction / pictogram separation means, and the multi-value corrected by the means Comprising a printing means for printing the image data, when printing multivalued image data read by the image reading means, gamma correction and the gradation of the first gray level correction means of the multi-value image data a the correction by the sum of the γ correction of the second gradation correction means, and at the time of large-size printing performed with γ curve correction γ to be used in multi-valued image data of Oite magnification to the second gray level correction unit 2 It is corrected using the γ curve of the crank-shaped curve closer to the binarization than valued, if the facsimile transmission multivalued image data read by the image reading means, the above in the multi-level image data to the print The same correction as the γ correction performed by the first gradation correction means is performed, and the data is transmitted by the facsimile transmission means .
[0025]
【Example】
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a multifunction peripheral according to an embodiment of the present invention. This multifunction device includes a document sensor 1, a pre-stage AMP / AD converter 2, a scanner (γ-correction) lookup table (LUT) 3, an electric scaling unit 4, a spatial filter / pictogram separation unit 5, and the like. .
[0026]
Further, a binarization processing section 6, a pictorial character synthesis section 7, a data compression processing section 8, a SAF memory section 9, a data decompression / compression processing section 10, a modem 11, a network control unit (NCU) 12, a multi-level line buffer 13, It includes a plotter (γ correction) lookup table (LUT) 14, a multi-level modulation circuit 15, and an LD light emitting unit 16.
[0027]
The document sensor 1 is a scanner of a line sensor such as a CCD, and corresponds to an image reading unit that reads an image of a document. The pre-stage AMP / AD converter 2 converts an image read by the original sensor 1 into multi-valued image data by AD conversion, and performs shading correction for correcting variations in sensitivity between elements of the CCD sensor.
[0028]
The scanner (γ correction) LUT 3 performs γ correction for logarithmic conversion of a sensor output and image tone correction at an input unit as correction of document density at the scanner with respect to the multivalued image data. Is corrected.
At this time, the gradation of the multi-valued image data read from the document is corrected using different correction tables for printing and facsimile transmission, and the gradation of the multi-valued image data is gently corrected for printing. That is, it corresponds to the above-mentioned first gradation correction means.
[0029]
The electric scaling unit 4 scales the image data corrected by the scanner (γ correction) LUT 3. That is, it corresponds to the above-described zooming means.
The spatial filter / pictogram separation processing section 5 performs MTF correction on the image data scaled by the electrical scaling processing section 4 and separates the image data into a character area portion and a picture area portion such as a photograph, thereby performing scaling. MTF correction and pictographic character separation means for correcting the resolution of the image data to be separated into a character area and a picture area.
[0030]
The binarization processing unit 6 corresponds to a unit that converts each multi-valued image data of the separated character area and picture area into binary data.
The pictorial character synthesizing unit 7 performs a process of synthesizing each binarized data of the character area and the picture area. The data compression processing unit 8 compresses the binarized data synthesized by the pictorial character synthesis unit 7. The SAF memory unit 9 stores the binarized data compressed by the data compression processing unit 8.
[0031]
The data decompression / compression processing unit 10 performs a process of compressing the binarized data stored in the SAF memory unit 9 for facsimile transmission and a process of decompressing the received image data. The modem 11 modulates the image data compressed by the data expansion / compression processing unit 10 for facsimile communication, demodulates the received image data, and sends a signal to the data expansion / compression processing unit 10 for signal conversion.
[0032]
The NCU 12 performs a network control process for switching between telephone communication and facsimile communication. In other words, the function processing units 7 to 12 correspond to a unit that combines the binarized data converted by the binarization processing unit 6 and transmits the data by facsimile.
The multi-level line buffer 13 is a memory that stores the image data whose resolution has been corrected by the spatial filter / pictogram separation processing unit 5.
[0033]
The plotter (γ-correction) LUT 14 performs γ-correction processing on the image data stored in the multi-value line buffer 13, that is, the gradation of the multi-value image data of the entire area whose resolution has been corrected by the spatial filter / pictogram separation processing unit 5. To correct.
At that time, the gradation of the multi-valued image data is corrected so as to be emphasized at the time of printing, and the gradation of the multi-valued image data to be printed at the time of enlargement printing is closer to binary than at the same size or reduced printing. Correction as follows. That is, it corresponds to the above-mentioned second gradation correction means.
[0034]
The multi-level modulation circuit 15 performs a multi-level modulation process of converting the image data corrected by the plotter (γ correction) LUT 14 into a signal for printing. The LD light emitting unit 16 forms an image based on image data using laser light from a laser diode. The formed image is printed on paper with toner.
[0035]
That is, the multi-level modulation circuit 15 and the LD light emitting unit 16 correspond to a printing unit that prints the multi-level image data corrected by the plotter (γ correction) LUT 14. The MTF correction is to correct the deterioration of optical frequency characteristics by a two-dimensional spatial filter and to correct the resolution of image data.
[0036]
Next, a description will be given of processing at the time of facsimile transmission in the multifunction peripheral.
In this process, when an image is read by the original sensor 1 and the pre-stage AMP / AD converter 2, the image is read by a γ correction process using a γ curve of a correction table used for facsimile transmission by the scanner (γ correction) LUT 3. The gradation of the multi-valued image data is corrected, scaled by the electric scaling unit 4 and sent to the spatial filter / pictogram separation unit 5.
[0037]
The spatial filter / pictogram separation processing unit 5 corrects the resolution of the image data after scaling by MTF correction processing to separate it into a character area and a picture area, and a binarization processing unit 6 separates the character area and the picture area. Each multi-valued image data is converted into binary data, and the pictorial character combining unit 7 combines the binary data.
[0038]
After that, the binarized data synthesized by the data compression processing unit 8 is compressed and stored in the SAF memory unit 9, and the data stored in the SAF memory unit 9 by the data decompression / compression processing unit 10 is transmitted for facsimile transmission. The data is modulated by the modem 11 and facsimile-transmitted to the destination by the NCU 12.
[0039]
Next, a description will be given of processing at the time of printing in the multifunction peripheral. First, an initial setting process at the time of printing will be described. FIG. 2 is a flowchart showing the processing. In this process, it is determined in step (indicated by "S" in the figure) 1 whether or not enlargement / resize copying (printing) is to be performed, and if it is enlargement printing, the process proceeds to step 2 where enlargement printing of the plotter (γ correction) LUT is performed. Γ curve of the correction table is set, and the process proceeds to step 3.
[0040]
If the printing is not the enlargement printing, the process proceeds to step 4 to set the γ curve of the correction table for normal printing (actual size or reduction) of the plotter (γ correction) LUT, and then proceeds to step 3. In step 3, if other modes (at the time of printing) are set, the initial setting is finished and the copying operation is started. 7 shows a γ curve of a correction table for normal printing of the plotter (γ correction) LUT, and FIG. 8 shows a γ curve of a correction table for enlarged printing of the plotter (γ correction) LUT.
[0041]
Next, the printing process will be described. First, during normal (1 ×) printing and reduced printing, when an image is read by the original sensor 1 and the pre-stage AMP / AD converter 2, the scanner (γ correction) LUT 3 uses the γ curve of the correction table used for printing. The gradation of the read multi-valued image data is gently corrected by the γ correction processing, and is scaled by the electric scaling unit 4 and sent to the spatial filter / pictogram separation unit 5.
[0042]
The spatial filter / picture character separation processing unit 5 corrects the resolution of the image data after scaling by MTF correction processing to separate the image data into a character area and a picture area, and stores them in the multi-level line buffer 13 for plotter ( Gamma correction) The LUT 14 corrects the multivalued image data of the entire area whose resolution has been corrected so as to emphasize the gradation, and the multivalued modulation circuit 15 and the LD light emitting unit 16 convert the corrected multivalued image data. Print on paper.
[0043]
Also, at the time of enlargement printing, the gradation of the multi-valued image data of the entire area whose resolution has been corrected by the plotter (γ correction) LUT 14 is emphasized, and is closer to binary than in the case of equal-size or reduced-size printing. The multi-level modulation circuit 15 and the LD light emitting unit 16 print the corrected multi-level image data on paper.
[0044]
In this composite apparatus, the spatial filter / pictogram separation processing section 5 is located behind the electric scaling processing section 4 on the premise of the pictogram separation processing at the time of facsimile transmission, and as shown in FIG. Since it is not necessary to have a unit, the circuit configuration of the device can be simplified and the cost can be reduced.
[0045]
Further, since the spatial filter / pictogram separation processing section 5 is provided after the electric scaling processing section 4, there is a problem that the MTF correction (filter correction) does not work effectively after the scaling processing at the time of enlarged copying. However, by performing a correction approaching the binary value based on the steep curve γ correction curve in the plotter (γ correction) LUT 14, the MTF correction effect can be improved in the same manner as when the filter is inserted before scaling. The MTF correction can be made to work effectively, and the image quality at the time of enlarged copy can be maintained.
[0046]
Further, by providing the scanner (γ correction) LUT 3 in front of the spatial filter / pictogram separation processing unit 5, when the curve of the γ curve is sharpened by the scanner (γ correction) LUT 3 during printing, This is emphasized by the MTF correction of the filter / pictogram separation processing unit 5, resulting in an unnatural image.
[0047]
FIG. 3 is a diagram showing an example of a steep curve γ curve set in the scanner (γ correction) LUT 3, and FIG. 4 is a diagram of a γ curve when the γ curve in FIG. 3 is emphasized by MTF correction. 5 is a diagram showing an example of a gentle γ curve set in the scanner (γ correction) LUT 3, and FIG. 6 is a diagram of a γ curve when the γ curve in FIG. 5 is emphasized by MTF correction.
[0048]
For example, if the curve of a γ curve near white is changed to a steep curve in order to cut a thin white background part to all white (portion surrounded by a circle in FIG. 3), this change is performed by MTF correction processing. The curve may be emphasized (a portion surrounded by a circle in FIG. 4), and a discontinuity of density such as a contour line may occur in a portion of the copy image close to a white background.
[0049]
However, in the scanner (γ correction) LUT 3, the γ correction is performed gently based on the γ curve having a gentle slope as shown in FIG. 5 to avoid the subsequent MTF correction, and the plotter (γ correction) LUT 14. In this case, based on the γ curve having a steep slope as shown in FIG. 6, γ correction is performed using the γ curve of a steep curve such as the background expression cut or the all black part clamp, so that the image quality at the time of copying can be maintained.
[0050]
At the time of facsimile transmission, γ correction is performed only by the scanner (γ correction) LUT 3, and at the time of printing, the AND of the γ correction at the scanner (γ correction) LUT 3 and the γ correction at the plotter (γ correction) LUT 14 is γ. Since correction is performed, by using different correction tables for printing and facsimile transmission, it is possible to use γ curves corresponding to the respective correction tables.
[0051]
Further, since the scaling process in the electrical scaling unit 4 is performed by interpolation calculation with surrounding pixels, it depends on the interpolation calculation method. However, during enlargement printing, the density difference between adjacent pixels becomes gentler. Therefore, in the copy mode in which the multi-level level is directly modulated and recorded, the MTF correction is hardly effective and the image is easily blurred at the white and black edges.
[0052]
However, at the time of enlargement printing, by setting the gamma curve of the crank-shaped curve in the plotter (γ correction) LUT 14 as shown in FIG. Correction can be made so as to approach the binary expression, and image blur can be prevented. Note that a γ curve as shown in FIG. 7 is set at the time of normal (1: 1 or reduced) printing.
[0053]
This multifunction device corrects the gradation of multi-valued image data read from a document, scales the corrected image data, and MTF- corrects the resolution of the scaled image data to perform a character area and a picture area. The multivalued image data of the separated character area and picture area are converted into binary data, and the converted binary data are combined and transmitted by facsimile. Further, the gradation of the multi-valued image data of the entire area whose resolution has been corrected is corrected, and the corrected multi-valued image data is printed. When printing the read multi-valued image data, the gradation of the multi-valued image data is calculated by adding the γ correction of the upper scanner (γ correction) LUT 3 and the γ correction of the plotter (γ correction) LUT 14. Of the crank-shaped curve which is closer to the binarization than the binarization performed by the γ curve of the γ correction used in the same-size multi-valued image data in the plotter (γ correction) LUT 14 at the time of enlarged printing. When performing the correction using the γ curve and transmitting the read multi-valued image data by facsimile, the same correction as the γ correction performed by the scanner (γ correction) LUT 3 on the multi-valued image data to be printed is performed. Send by facsimile.
Therefore, even if the resolution of the image data after the magnification change is not effective, it is possible to approach the binarization by gradation correction at the time of printing to sufficiently suppress the image blur, and to enlarge the copy without increasing the scale of the circuit configuration. The image quality of the image at the time can be improved.
In addition, the gradation of the read multi-valued image data is gently corrected, thereby suppressing the adverse effects of the subsequent resolution correction, and correcting the gradation of the multi-valued image data to be printed so as to emphasize the gradation. , And sharp gradation correction such as clamping of all black parts is performed, so that the image quality of an image at the time of copying can be improved without increasing the scale of the circuit configuration.
Furthermore, it is possible to be different from the time of printing a gradation correction during transmission off Akushimiri, it is possible to improve the image quality of the image at the time of facsimile transmission without enlarging the scale of the circuit configuration.
Composite apparatus of this embodiment, performing the character separation process of the binary data of the facsimile sending optimally, it is possible to maintain the image quality of the image at the time of multi-level copy.
Further, it is possible to eliminate a negative factor that lowers the image quality of the copy image without increasing the cost. Further, the image quality of the image at the time of facsimile transmission can be improved. Furthermore, it is possible to eliminate a negative factor that degrades the image quality of a copy image at the time of enlarged printing without increasing costs.
[0054]
Therefore, it is possible to simplify the circuit configuration in the conventional apparatus while maintaining the quality of the image at the time of copying and the quality of the halftone image at the time of facsimile transmission at the best, and to secure the reliability of the apparatus and reduce the cost. Down can also be achieved.
[0055]
【The invention's effect】
As has been described, according to the multifunction apparatus according to the present invention, image quality and the copy when images without enlarging the scale of the circuit configuration, the image quality of image at the time of facsimile transmission, the image at the time of enlargement copy quality Can also be improved.
Therefore, the cost of the apparatus can be reduced and the reliability can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a multifunction peripheral according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating an initial setting process at the time of printing in the multifunction peripheral according to the embodiment.
FIG. 3 is a diagram showing an example of a steep curve γ curve set in a scanner (γ correction) LUT 3 of FIG. 1;
FIG. 4 is a diagram of a γ curve when the γ curve shown in FIG. 3 is emphasized by MTF correction.
FIG. 5 is a diagram showing an example of a gentle γ curve set in the scanner (γ correction) LUT 3 of FIG. 1;
6 is a diagram of a γ curve when the γ curve shown in FIG. 5 is emphasized by MTF correction.
7 is a diagram showing a γ curve of a correction table for normal printing of the plotter (γ correction) LUT 14 of FIG. 1;
8 is a diagram illustrating a γ curve of a correction table for enlarged printing of the plotter (γ correction) LUT 14 of FIG. 1;
FIG. 9 is a block diagram illustrating main functional units related to digital copy processing of a conventional multifunction peripheral.
FIG. 10 is a block diagram showing main functional units relating to facsimile transmission processing of a conventional multifunction peripheral.
[Explanation of symbols]
1: Document sensor 2: Pre-stage AMP / AD converter 3: Scanner (γ correction) lookup table (LUT)
4: Electric scaling unit 13: Multi-level line buffer 5: Spatial filter / pictogram separation processing unit 6: Binarization processing unit 7: Pictogram synthesis unit 8: Data compression processing unit 9: SAF memory unit 10: Data expansion / Compression processing unit 11: Modem 12: Network control unit (NCU)
14: Lookup table (LUT) for plotter (γ correction)
15: Multi-level modulation circuit 16: LD light emitting unit

Claims (1)

Image reading means for reading an image of a document, first gradation correction means for correcting the gradation of the multi-valued image data read by the means, and scaling means for scaling the image data corrected by the means MTF correction / pictogram separation means for MTF- correcting the resolution of the image data scaled by the means to separate it into a character area and a picture area, and multi-valued images of the character area and the picture area separated by the means Means for converting the data into binary data, means for synthesizing each of the binary data converted by the means for facsimile transmission, and means for converting the entire area whose resolution has been corrected by the MTF correction / pictogram separation means. A second gradation correction unit for correcting the gradation of the multi-valued image data; and a printing unit for printing the multi-valued image data corrected by the unit. When printing a multi-valued image data read is the correct the gradation of the multi-valued image data by the sum of the γ correction γ correction and the second tone correcting means of the first gray level correction means and, and of the time of large-size printing crank shape curve closer to the binarization than binarization performed by the γ curve of the second tone correcting means used in the multi-value image data such as the magnification Oite the γ correction γ is corrected by using a curve, when transmitting facsimile multivalued image data read by the image reading means, similar correction performed γ correction and by the first gray level correction means in the multivalued image data to the printing And transmitting by the facsimile transmission means .

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