JP2005020224A - Image processor and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form image data whose quality is almost the same as an original image and to reduce an image quality difference which occurs between reading image data on a surface and a rear face. <P>SOLUTION: In an image processor, two image sensors read both face image data of an original by one operation. Image quality of image data which one image sensor reads is corrected based on prescribed reference image data. Image quality of image data which the other image sensor reads is corrected based on corrected image data. Thus, not only an image quality difference which occurs between reading image data on the surface and the rear face, but also the image quality difference with original image data, are reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and an image forming apparatus having a double-sided image reading function, and in particular, image processing for reading the front and back surfaces of a document with a single operation and processing the read image data based on predetermined reference image data. The present invention relates to an apparatus and an image forming apparatus.
[0002]
[Prior art]
Image processing apparatuses such as copying machines and image scanners having a double-sided image reading function for reading image data on both sides of a document and performing image processing are widely used. This double-sided image reading function is performed by a CIS (Contact Image Sensor), a CCD (Charge Coupled Device), or a CMOS (Complementary Metal-Oxide Semiconductor, complementary metal oxide semiconductor) provided in the apparatus. The image data on both sides of the document is read by an image sensor such as. Here, the CIS receives a light source such as an LED, a light guide that guides light emitted from the light source in the width direction of the document, a lens that collects reflected light from the document, and the collected reflected light. An integrated image sensor including a linear photosensor (a sensor that senses light arranged in a straight line).
As an example of this double-sided image reading function, there is one in which after reading the surface image data of a document using one image sensor, the document is reversely conveyed and the back image data of the document is read again by the image sensor. is there. Since the image data of the front and back sides read by this method are both read by the same image sensor, there is an advantage that there is no difference in image quality between the front and back sides of the output image. There has been a problem such as document jamming in the reversal conveyance path as a configuration.
In Non-Patent Document 1, two image sensors are used to read image data on both sides of a document substantially simultaneously in one operation, thereby eliminating the conventional document reversal operation and improving the processing speed. By absorbing the difference in characteristics between the scanned front and back image data by performing processing that matches the scanned image data with the image quality characteristics of the front scanned image data, An image processing apparatus is described that suppresses the difference in image quality between the front and back surfaces caused by reading the front and back surfaces of a document with individual image sensors within a predetermined allowable range.
[0003]
[Non-Patent Document 1]
Yasutaka Takagi, 7 others, “RICOH TECHNICICAL REPORT”, imagio NEO750 / 600 series, P143-P148, [online], November 30, 2002, Ricoh Co., Ltd., Research and Development Headquarters, [May 8, 2003 Day search], Internet <http: // www. ricoh. co. jp / rdc / techreport / No28 / Ronbun / C2802. pdf>
[0004]
[Problems to be solved by the invention]
However, the image processing apparatus described in the above-mentioned non-patent document can reduce the image quality difference between the scanned image data on the front side of the document and the image data on the back side of the document. When the accuracy of the image sensor that reads the image data on the front side of the document is lowered, the image data on the back side of the document is the image quality of the surface image data read by the image sensor that has been lowered in accuracy, that is, the surface image data with low reproduction accuracy. Since processing is performed in accordance with the characteristics, there is a problem that a large difference in image quality occurs compared to the image quality of the original.
Accordingly, the present invention has been made in view of the above circumstances, and the object of the present invention is not only to generate image data having substantially the same image quality as the original image data, but also to read the front and back sides of the read original. An object of the present invention is to provide an image processing apparatus and an image forming apparatus that can further reduce the difference in image quality that occurs between image data as compared with the prior art.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an image processing apparatus for processing read image data based on predetermined reference image data, the first reading means for reading surface image data of a document, and the same document. And a second reading unit that reads the back side image data of the first reading unit, the first reading unit corrects the image quality of the first read image data read by the first reading unit based on the reference image data. Image quality correcting means, and second image quality correcting means for correcting the image quality of the second read image data read by the second reading means based on the corrected image data corrected by the first image quality correcting means. It is comprised as an image processing apparatus characterized by comprising.
With this configuration, it is possible to reduce the difference in image quality that occurs between the read image data on the front and back surfaces, and to reduce the difference in image quality from the original image data. In this case, it is preferable that the first reading means reads the image data on the front side of the document by CIS, and the second reading means reads the image data on the back side of the document by CCD or CMOS. Preferably there is.
[0006]
Here, the first image quality correction unit reads the reference image data stored in advance in a predetermined storage device, and corrects the image quality of the first read image data based on the read reference image data. It is thought that it is what to do.
As a result, the image data of the first read surface is corrected in accordance with the image quality characteristics of the reference image data. Therefore, the image data of the first read surface always has substantially the same image quality as the original image data. Will be obtained. In this case, it is preferable that the first image quality correction means corrects the image quality of the first read image data based on a characteristic parameter relating to the image quality characteristics of the reference image data. It is preferable that the correcting means corrects the image quality of the second read image data based on a characteristic parameter relating to the image quality characteristics of the corrected image data. Furthermore, the characteristic parameter is at least one of a color correction parameter indicating a color characteristic, a gamma correction parameter indicating a gamma characteristic, an MTF correction parameter indicating an MTF characteristic, or a correction parameter indicating a chromatic aberration characteristic. It is possible that there is. Among the many characteristic parameters related to the image quality characteristics, correction is made based on the above-described four characteristic parameters that greatly affect the image quality.
[0007]
Further, even the image forming apparatus provided with the image processing apparatus can solve the problem.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a schematic cross-sectional view showing a schematic structure of an image processing apparatus according to an embodiment of the present invention. FIG. 2 is an outline of an image processing control apparatus provided in the image processing apparatus according to the embodiment of the present invention. FIG. 3 is a flowchart for explaining an image processing procedure executed in the image processing apparatus according to the embodiment of the present invention.
[0009]
First, the schematic configuration of the image processing apparatus X according to the embodiment of the present invention will be described with reference to the schematic cross-sectional view of FIG. 1 and the block diagram of FIG. The image processing apparatus X includes two image sensors, a CCD that reads the image on the front side of the document and a CIS that reads the image on the back side of the document, and reads image data on the front and back sides of the document at approximately the same time and performs image processing. For example, a copier and a printer having a double-sided reading / printing function, a scanner device having a double-sided reading function, or a digital multi-function peripheral having the functions of these plural devices is applicable.
As shown in FIG. 1, the image processing apparatus X includes an exposure device 21 that exposes a surface F of a document that is sent from an ADF (Auto Document Feeder) 10 and is transported in a transport path 11, and a document. Mirrors 22a, 22b, and 22c that guide the irradiation light applied to the surface F to the optical lens 23 and the CCD 24, the optical lens 23 that collects the reflected light, and the CCD 24 that receives the reflected light collected by the optical lens 23. (Corresponding to a first reading unit) and an image processing control device 20 that executes image processing based on the reflected light received by the CCD 24 are provided. The CCD 24 converts image information contained in the received reflected light into an electrical signal that can be read by the image processing control device 20.
Further, the image processing apparatus X is also provided with a CIS 12 (corresponding to the second reading means) provided to read the image data on the back surface R of the document in the transport path 11 for transporting the document sent from the ADF 10. ing. The CIS 12 converts image information contained in the received reflected light into an electrical signal that can be read by the image processing control device 20.
Thus, in the present image processing apparatus X, by providing two image sensors in one conveyance path 11, both sides of the document can be read substantially simultaneously, and the time spent for the reading process can be shortened. it can.
[0010]
As shown in FIG. 2, the image processing control device 20 includes a CIS reading circuit 110, a CCD reading circuit 120, a storage unit 140, a CIS image correction unit 150, a CCD image correction unit 160, and a CPU that controls these units. The image processing control unit 100 includes an ASIC (Application Specific Integrated Circuit) or the like.
The storage unit 140 includes a non-volatile memory such as a ROM for storing reference image data (data serving as a reference for image quality) used for correcting the image quality of image data read by the CCD 24 and the like, and a CIS reading circuit described later. 110 and the digital image data converted by the CCD reading circuit 120, and a semiconductor memory such as a RAM used as a work area when image processing is executed.
[0011]
The CCD reading circuit 120 (corresponding to the first reading means) is a circuit that reads the electric signal converted by the CCD 24 and converts it into digital image data. The CIS reading circuit 110 (corresponding to the second reading means) is a circuit that reads the electrical signal converted by the CIS 12 and converts it into digital image data.
[0012]
The CCD image correction unit 160 (an example of the first image quality correction unit) corrects the image quality of the digital image data converted by the CCD reading circuit 120 based on the reference image data stored in advance in the storage unit 140. For example, it corrects the image quality of the digital image data converted by the CCD reading circuit 120 based on the characteristic parameter relating to the image quality characteristics of the reference image data, that is, an element that affects the image quality. In consideration of this characteristic, the characteristic is treated as a parameter, and the characteristic parameter is adjusted by changing the numerical value of the parameter, thereby correcting the image quality.
The CIS image correcting unit 150 (an example of the second image quality correcting unit) converts the image quality of the digital image data converted by the CIS reading circuit 110 based on the CCD corrected image data corrected by the CCD image correcting unit 160. And correcting the image quality of the digital image data converted by the CIS reading circuit 110 on the basis of a characteristic parameter relating to the image quality characteristics of the CCD corrected image data. Similar to 160, the image quality is corrected by adjusting the parameters.
In order to generate image data having substantially the same quality as that of the original image data, it is conceivable to correct the image quality based on all the characteristic parameters relating to the characteristics of the image quality. However, factors affecting image quality include, for example, characteristics of ink, toner or film, characteristics of paper media, characteristics of document types (photos, illustrations, graphics, text), characteristics of color format, and gray balance. , Brightness, contrast, saturation, color characteristics, gamma characteristics, lens characteristics (especially chromatic aberration), MTF (Modulation Transfer Function) characteristics, etc., and all these characteristics are used as parameters. If it is used and corrected, it takes a lot of time for image processing. Therefore, in the present embodiment, the color characteristics, gamma characteristics that most affect the image quality, and then parameters of the MTF characteristics and chromatic aberration characteristics that affect the image quality are used as correction parameters, and the image quality is corrected based on the correction parameters. I will do it. Accordingly, the CIS image correction unit 150 and the CCD image correction unit 160 include color correction circuits 151 and 161 that correct image quality based on characteristic parameters of color characteristics, gamma characteristics, MTF characteristics, and chromatic aberration characteristics, and a gamma correction circuit 152. 162, MTF correction circuits 153 and 163, and chromatic aberration correction circuits 154 and 164 are provided.
[0013]
Next, the operation of the image processing apparatus X according to the embodiment of the present invention will be described using the schematic cross-sectional view of FIG.
After the document S to be read on both sides of the image is set on the ADF 10, the user inputs an operation from an operation panel (not shown) arranged on the front surface of the exterior of the apparatus, or both sides from an external host device such as a personal computer. When a document reading instruction is given, the image processing control unit 100 operates the CCD 23, the CIS 12, and the like based on the double-sided reading function to prepare for reading a double-sided document.
When the user operates the start key, a main drive motor (not shown) is started, and the driving torque is transmitted to a transport roller (not shown) that transports the document S via a plurality of gears. It is sent out to the conveyance path 11.
When the document S passes through the U-shaped portion of the conveyance path 11, the leading end of the document S first reaches a position P where image data on the document surface F is read by the CCD 24. At the point P, the exposure device 21 starts exposure of the document surface F. Irradiation light applied to the document surface F becomes reflected light (reflected light from the document) including image information of the document S, and this reflected light passes from the first mirror 22a to the second mirror 22b and the third mirror 22c. Then, the reflected light guided to the optical lens 23 and condensed by the optical lens 23 is received by the CCD 24.
While the document surface F is read, the leading end portion of the document S further conveyed reaches a position Q where image data on the document back surface R is read by the CIS 12. At point Q, the CIS 12 receives reflected light that is irradiated from an LED or the like and reflected from the original.
[0014]
The reflected light received by the CCD 24 and the CIS 12 is converted into an electric signal including image information, and the converted electric signal corresponds to the electric signal by the image processing control unit 100 in the CCD reading circuit 120 and the CIS reading circuit. Converted into digital image data.
The digital image data (CCD digital data) of the document surface P previously read by the CCD 24 is subjected to image quality correction in the CCD image correction unit 160 based on the reference image data stored in the storage unit 140. Specifically, the image processing control unit 100 reads the numerical values of the characteristic parameters of the image quality characteristics (color characteristics, gamma characteristics, MTF characteristics, chromatic aberration characteristics, etc.) of the reference image data and the CCD digital data, and the CCD digital data. The numerical values of the characteristic parameters of the CCD digital data are changed so that the characteristic parameters of the data are within an allowable range based on the characteristic parameters of the reference image data. As a result, the image quality is corrected.
The digital image data (CIS digital data) on the back side Q of the document read by the CIS 12 after the CCD 24 is converted into corrected image data (CCD corrected image data) corrected by the CCD image correcting unit in the CIS image correcting unit 150. Based on this, the image quality is corrected. Specifically, in the same manner as the processing performed in the CCD image correction unit 160, the image processing control unit 100 reads numerical values of image quality characteristic parameters of the CCD correction image data and the CIS digital image data, and the CIS. The image quality is corrected by changing the numerical values of the parameters of the CIS digital data so that the characteristic parameters of the digital data are within an allowable range based on the characteristic parameters of the CCD corrected image data.
[0015]
Next, an image processing procedure of the image processing control unit 100 executed in the image processing apparatus X according to the embodiment of the present invention will be described using the flowchart of FIG. When a document to be scanned on both sides of image data is set in the ADF 10 (FIG. 1) and a double-sided image reading instruction is input by the user, a conveyance roller for feeding the document set on the ADF 10 to the conveyance path 11 is rotationally driven. Documents are sent one by one to the conveyance path 11. At this time, the image processing control unit 100 performs the image processing described below on the double-sided image data of the document conveyed in the conveyance path 11. In the figure, S100, S110 ..., S200, S210 ... indicate processing procedure (step) numbers. The process starts from step S100.
[0016]
When the leading edge of the document reaches point P (a point where image data on the surface of the document can be read by the CCD 24), in step S100, the image processing control unit 100 exposes the exposure device 21 to expose the document using the CCD 24. The image data of the surface F is read. When the document read by the CCD 24 reaches the point Q at the downstream side in the transport direction (a point where image data on the back side of the document can be read by the CIS 12), the image data of the back side R of the document is transferred to the CIS 12 in step S200. Let me read.
In step S110, the reference image data stored in advance in the ROM or the like of the storage unit 140 and the numerical values of the characteristic parameters relating to the image quality of the digital data (CCD digital data) read by the CCD 24 are read, and each characteristic of the CCD digital data is read. The parameter and each parameter of the reference image data are compared.
In the next step S120, it is determined whether each characteristic parameter of the CCD digital data is within a certain allowable range based on each parameter of the reference image data. If it is determined that at least one of the characteristic parameter values is not within the allowable range, in step S130, the characteristic parameter that is not within the allowable range of the CCD digital data is shifted so as to be within the allowable range. The parameters are adjusted by changing the numerical values of the parameters of the CCD digital data. Thereafter, the process of step S120 is repeatedly executed again. Steps S120 to S130 are repeatedly executed until it is determined in step S120 that it is within the allowable range. If it is determined in step S120 that it is within the allowable range, the image data (first adjusted image data) whose characteristic parameters have been adjusted is stored in a predetermined storage area of the storage unit 140 (S140).
As described above, the first image quality correction means is a means for executing the process of adjusting the characteristic parameter by comparing the digital image data read by the CCD and the reference image data by executing the processes of steps S110 to S130. It is an example.
[0017]
When the process of step S140 is completed, the image processing of the image data of the document back surface R read by the CIS 12 in step S200 is started from step S210.
In step S210, numerical values of characteristic parameters relating to image quality of the first adjustment image data stored in the storage unit 140 and digital data (CIS digital data) read by the CIS 12 are read, and each characteristic of the CIS digital data is read. The parameter and each parameter of the first adjusted image data are compared.
In the next step S220, it is determined whether or not each characteristic parameter of the CIS digital data is within a certain allowable range based on each parameter of the first adjusted image data. If it is determined that at least one characteristic parameter value is not within the allowable range, in step S230, the characteristic parameter that is not within the allowable range of the CIS digital data is shifted so as to be within the allowable range. The parameter is adjusted by changing the numerical value of the parameter of the CIS digital data. Thereafter, the process of step S220 is repeatedly executed again. Steps S220 to S230 are repeatedly executed until it is determined in step S220 that the value is within the allowable range. If it is determined in step S220 that the value is within the allowable range, the image data (second adjusted image data) whose characteristic parameters have been adjusted is stored in a predetermined storage area of the storage unit 140 (S240).
As described above, the first image quality correction unit is a unit that executes the process of steps S210 to S230 to execute the process of adjusting the characteristic parameter by comparing the digital image data read by the CIS and the reference image data. It is an example.
When the adjustment of the characteristic parameters in steps S130 and S230 is completed, that is, when the image quality correction of the image data on both sides of the original image is completed, predetermined image processing is executed in step S150.
[0018]
【Example】
In the above embodiment, the image processing apparatus X including the two image sensors of the CCD for reading the image on the front side of the document and the CIS for reading the image on the back side of the document has been described. However, the present invention is not particularly limited thereto. In principle, there is no special combination of image sensors for reading image data on the front or back side of the document, and the same kind of image sensors may be used. However, in recent years, considering that the apparatus tends to be compact, it is desirable to use CIS, which is a relatively compact image sensor on both sides of the original, or at least one of the back and front sides of the original is CIS. It is desirable to have a configuration that reads by the above. In addition, it is desirable to use CIS for the same reason when an image sensor is provided in a conveyance path that has little space.
[0019]
【The invention's effect】
As described above, according to the image processing apparatus of the present invention, one image sensor based on predetermined reference image data is transferred to an image processing apparatus that reads two-sided image data of a document with one operation by two image sensors. The image quality of the image data read by the image sensor is corrected, and the image quality of the image data read by the other image sensor is corrected based on the corrected image data. Not only the image quality difference that occurs between the image data on the back side is reduced, but also the image quality difference with the original image data can be reduced.
Further, the correction process is simplified by correcting the image quality based on the characteristic parameter relating to the image quality characteristic of the reference image data.
The characteristic parameter is at least one or more of a color correction parameter indicating a color characteristic, a gamma correction parameter indicating a gamma characteristic, an MTF correction parameter indicating an MTF characteristic, or a correction parameter indicating a chromatic aberration characteristic. As a result, the image quality difference between the image data on the front and back sides of the document can be suppressed within an allowable range that cannot be visually recognized without processing many parameters, and the processing speed is improved.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a schematic structure of an image processing apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a schematic configuration of an image processing control apparatus provided in the image processing apparatus according to the embodiment of the present invention.
FIG. 3 is a flowchart illustrating an image processing procedure executed in the image processing apparatus according to the embodiment of the present invention.
[Explanation of symbols]
10 ... ADF (Auto Document Feeder)
11 ... Conveying path 12 ... CIS
20 ... Image processing control device 21 ... Exposure device 22 ... Mirror 23 ... Optical lens (condensing lens)
24 ... CCD

Claims (8)

An image processing apparatus for processing read image data based on predetermined reference image data, a first reading unit for reading the front surface image data of the document, and a second reading unit for reading the back side image data of the document In an image processing apparatus comprising:
First image quality correction means for correcting the image quality of the first read image data read by the first reading means based on the reference image data;
And second image quality correcting means for correcting the image quality of the second read image data read by the second reading means based on the corrected image data corrected by the first image quality correcting means. An image processing apparatus. The image processing apparatus according to claim 1, wherein the first reading unit reads surface image data of a document by CIS. 2. The image processing apparatus according to claim 1, wherein the second reading means reads back side image data of a document by a CCD or a CMOS. The first image quality correcting means reads the reference image data stored in advance in a predetermined storage device and corrects the image quality of the first read image data based on the read reference image data. The image processing apparatus according to claim 1. 5. The image processing according to claim 1, wherein the first image quality correction unit corrects the image quality of the first read image data based on a characteristic parameter relating to an image quality characteristic of the reference image data. apparatus. 5. The image processing according to claim 1, wherein the second image quality correcting unit corrects the image quality of the second read image data based on a characteristic parameter relating to the image quality characteristics of the corrected image data. apparatus. The image processing apparatus according to claim 5, wherein the characteristic parameter is at least one of a color correction parameter, a gamma correction parameter, an MTF correction parameter, or a chromatic aberration correction parameter. An image forming apparatus comprising the image processing apparatus according to claim 1.

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