JPH08307685A - Facsimile equipment - Google Patents

Abstract

PURPOSE: To control execution/non-execution of rear side read processing operation for each prescribed range of one sheet of original. CONSTITUTION: The facsimile equipment reads image information of both front and rear sides of an original simultaneously, and applies image processing to each image information on the front side 3 and the rear side of the original respectively based on a parameter individually set for the front side and the rear side in order to enhance the quality of the image information as a result of the reading. Then parameters or the like for each of correction processing sections 6, 7, 8, 6a, 7a, 8a of both processing sections (front side image processing section 1 and rear side image processing section 2) are dynamically revised corresponding to a density change represented by each image information read from the front side and the rear side of the original and is provided with a control section 11 preventing both image information transmitted through each image information of the front side and the rear side of the original.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facsimile apparatus for performing various image processing such as MTF correction and .gamma. Correction in order to read image information of an original with high quality, and in particular, information is recorded on both front and back sides. The present invention relates to a facsimile apparatus suitable for reading image information of a document with high quality.

[0002]

2. Description of the Related Art In recent years, in many cases, the back side of a paper that has been used once is reused as a manuscript used in a facsimile machine in view of environment and economy. When reading a document (front surface) on which information is also written on the back surface, information on the opposite surface (back surface) may appear on the front surface, that is, show-through may occur. In addition, there is a conventional facsimile apparatus in which reading sensors are installed on both front and back sides of a document so that a document having information recorded on both sides thereof (double-sided document) can be read at a time. As described above, even when the double-sided recording original is read at one time, the information on the opposite side may show through.

As a conventional technique for preventing the show-through when reading such a double-sided recording original document, for example, Japanese Patent Laid-Open No. Hei 5 (1999) -58242 is available.
No. 14717 and Japanese Patent Laid-Open No. 1-318.
There is one disclosed in Japanese Patent Publication No. 460. JP-A-5-1471
The technique described in Japanese Patent Laid-Open No. 7-74 is intended to prevent show-through by blackening the background on the reading line by switching the members. When the image is read, the show-through is prevented by changing the image density standard.

However, in these conventional techniques, the members are switched and the image density standard is changed by simply recognizing whether or not the original is a double-sided recording original having information written on both front and back sides. There is. That is, for one double-sided recording original, the processing operation relating to the show-through prevention is continued from the start to the end of reading the image information of the original. Therefore, for example, when only the leading part of the document is double-sided recorded, or conversely, when only the rear half of the document is double-sided recorded, the quality of the image information of the double-sided recorded part and There is a difference from the quality of the remaining image information that has not been recorded.

[0005]

The problem to be solved is that the prior art cannot control execution / non-execution of the show-through processing operation for each predetermined range of one original. . An object of the present invention is to solve these problems of the prior art and to provide a facsimile apparatus capable of reading image information from a partially partially double-sided document with high quality.

[0006]

In order to achieve the above object, the facsimile apparatus of the present invention is (1) preset when reading image information of an original document in order to improve the quality of the image information as the read result. In a facsimile apparatus that performs image processing based on the parameter values, the back side reading unit (contact image sensor 24) that reads the image information on the back side (back side) of the reading side (front side) of the document, and the back side reading unit reads the image information. A show-through for dynamically changing the parameter value of each correction unit in the image processing unit 2 in accordance with the density change indicated by the image information to prevent the image information on the back side of the document from showing through on the image information on the front side of the document. Preventing means (control unit 1
1) and are provided. Further, (2) parameter values set individually for the front side and the back side in advance in order to simultaneously read the image information on both the front and back sides of the document and to improve the quality of the image information as a result of reading when reading the image information of the document. Based on the above, in a facsimile apparatus that performs image processing on image information on the front and back sides of an original, both (front side image processing unit 1 , A backside image processing unit 2) which dynamically changes the parameter value of each correction processing unit and the like to prevent the image information of both the front side and the back side of the original from being offset. It is characterized in that the (control unit 11) is provided. Also,
(3) The facsimile apparatus according to (1) or (2) above is provided with MTF correction units 7 and 7a that perform image processing by MTF correction for improving the quality of image information as a reading result. The show-through prevention unit (control unit 11) is characterized in that the parameter value is dynamically changed by dynamically switching the setting as to whether or not to perform the MTF correction. Also, (4) above (1), or
In the facsimile machine according to any one of (2),
MT for improving the quality of image information as a reading result
The MTF correction units 7 and 7a for performing image processing by F correction are provided, and the show-through prevention unit (control unit 11) dynamically changes the parameter value by using the MTF correction coefficient used by the MTF correction units 7 and 7a for MTF correction. The feature is that the setting value is dynamically changed. (5) In the facsimile apparatus according to any one of (1) to (4) above,
Γ correction units 8 and 8a for performing image processing by γ correction for improving the quality of image information as a read result are provided, and the show-through prevention unit (control unit 11) controls the dynamic change of the parameter value by the γ correction unit. It is characterized in that the gamma correction tables 8 and 8a refer to at the time of gamma correction by dynamically switching.
(6) In the facsimile apparatus according to any one of (1) to (5), peak detection units 4 and 4a for performing peak value detection processing for improving the quality of image information as a read result are provided. , Show-through prevention means (control unit 1
1) is for dynamically changing the parameter value,
4a is performed by dynamically changing the time (following time constant) used for detecting the peak value.

[0007]

According to the present invention, whether or not information is recorded on the back side of the read original surface is recognized for each area of the width of the original in the conveying direction, and each parameter for defining image processing is determined according to the recognition result. To prevent show-through by dynamically changing for each area. In this way, by performing the show-through prevention control for each area, it is possible to read high-quality image information. Further, in a facsimile machine capable of simultaneously reading information recorded on both sides of a document,
By utilizing the reading sensors on the front surface and the back surface, the show-through can be prevented easily and with high quality without adding a new mechanical mechanism or control mechanism as much as possible.

MTF correction can be used as a parameter that is dynamically changed for each area. in this case,
For example, by selecting whether or not to execute the MTF correction, it is possible to prevent the show-through mainly on the background portion of the document, and by changing the value of the MTF correction coefficient, the density becomes light and the image information is reduced. It is possible to prevent the show-through without causing the image to be missing. The MTF correction is the spatial frequency transfer characteristic (MTF: Modulation Transfer Func) of the document contrast, the optical system, and the image sensor.
In order to cope with the deterioration of the photoelectric conversion output due to the rotation), a process of emphasizing the high frequency component of the output is performed. By this MTF correction, the fine line and the contour portion are reproduced more clearly.

Further, γ correction can be used as a parameter that is dynamically changed for each area. In this case, by dynamically switching the γ correction table to be referred to during the γ correction, it is possible to prevent the show-through, which does not result in an unnatural reproduced image due to a low density in a halftone image such as a photograph. be able to. The γ correction defines the density conversion characteristic in the reading range of the original, and in order to faithfully reproduce the halftone information, the gradation correction is performed according to the recording characteristic. Further, the peak value of the image signal that becomes the reference white level in the document reading range can be used as a parameter that is dynamically changed for each area unit. In this case, the occurrence of show-through can be suppressed by dynamically switching the tracking time constant of the peak value.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 is a block diagram showing an embodiment of the configuration of the facsimile apparatus of the present invention according to the present invention.
FIG. 2 is a side end view of the facsimile apparatus having the configuration shown in FIG. 1. In FIG. 2, 21 is a document guide on which a document is set, 22 is a document separation / conveyance roller that separates and conveys the set document, 23 is a document conveyance roller that conveys the separated document, and 24 is a document scan. A contact image sensor that performs photoelectric conversion by using a light source, a light source 25 such as a halogen lamp, a contact glass 26 on which a document is adhered, a document discharge roller 27 for discharging a document, 28 a mirror for reflecting a document image, 29 a mirror 28 A lens for converging the original image reflected from the lens 40 is a CCD (Charge Coupled D) for photoelectrically converting the original image converged by the lens 29.
evice, charge-coupled device), 41 is a paper discharge tray for stacking discharged originals.

The facsimile apparatus of this embodiment has a structure in which one side of the document surface is read by a reduction optical system sensor consisting of a CCD 40 and the other surface is read by a contact image sensor 24 incorporating a light source 25 as a module. Both front and back sides can be read at the same time. The operation will be described below. When the original is set on the original guide 21 and the reading operation is started, the original is first conveyed by the original separating / conveying roller 22 and then by the original conveying roller 23 in the direction of the arrow, and finally the original discharging roller. The sheet is stacked on the sheet discharge tray 41 by 27.

Document transport roller 23 and document discharge roller 27
A sensor for reading image information on both the front and back sides of the document is installed between the two, and the contact image sensor 24 for reading the back side is located on the document conveyance path more than the contact glass 26 which is the line for front side reading. It is located on the upstream side, and has a positional relationship such that the reading scans on the front and back sides of the document do not interfere with each other. Focusing on a certain part of the document based on the positional relationship of the sensors, the back side is first read by the contact image sensor 24, and then the front side of the same part is the light source 25, the contact glass 26, the mirror 28, the lens 29, and the CCD 40.
It is read by a reduction optical system composed of

As described above, when the image information recorded on both the front and back sides is read simultaneously, both records cause the show-through of each other. As shown in FIG. 1, the present facsimile machine can prevent such show-through efficiently and with high quality by controlling each correction operation in the image processing section. Below, a description of the show-through prevention is given in FIG.
Using.

In FIG. 1, 1 is the CCD in FIG.
A front side image processing unit that performs image processing such as correction based on various preset parameter values on image information on the front surface (front surface) of the document read by 40 to improve the quality of the image information. 2 is a back side image processing unit that enhances the quality of image information on the back side (back side) of the original read by the contact image sensor 24 in FIG. 2, and 11 is the front side image processing unit 1 and the back side image. The control unit performs the show-through prevention control according to the present invention based on the processing result of the processing unit 2.

The front-side image processing unit 1 and the back-side image processing unit 2 have the same configuration, and A / D converters 3 and 3a for converting the photoelectrically converted analog image signal into a digital signal, and this A Peak detectors 4 and 4a for detecting the peak value by an overflow signal at the time of D / D conversion or the like
Shading correction of the digital signal data (image information) A / D converted by the D / A converters 5 and 5a for converting the peak value into an analog signal and the A / D converters 3 and 3a. Shading correction unit 6, 6
a and MTF correction units 7 and 7a that perform MTF correction of image information
And γ correction units 8 and 8a that perform γ correction of image information, and binarization processing units 9 and 9a that perform binarization processing of each corrected image information.
And command registers 10, 10a for storing control information from the control unit 11.

With such a configuration, the front side image processing section 1
And the back side image processing unit 2 converts the control signals 12 and 13 from the control unit 11 into internal control signals by the command registers 10 and 10a and transmits the internal control signals to the internal blocks, thereby setting various parameters relating to image processing, Also, the parameters are changed while the document is being read. In this example, the image processing is performed on the front side and the back side of the original by using different circuits as described above. However, for example, multi-valued data after A / D conversion is toggled input line by line. Therefore, it is possible to use a common processing circuit. However, each process setting on the front and back sides (setting of parameters used for each correction process) must be made independently. The operation of the front image processing unit 1, the back image processing unit 2, and the control unit 11 according to the present invention will be described below.

The front side image processing section 1 and the back side image processing section 2 are respectively the contact image sensor 24 and C shown in FIG.
The analog image signal of the original read by CD40 is
The D converters 3 and 3a convert it into a digital signal of several bits. The A / D converted data is used for the peak detection units 4 and 4
In addition to the detection by a, the shading correction units 6 and 6a correct the distortion of the sensor and the optical system of the digital signal data. Further, the peak detection units 4 and 4a sequentially update and hold and output the peak value by the overflow signal at the time of shading correction. This peak value is D
The signals are converted into analog signals by the / A converters 5 and 5a and applied as the upper reference voltage of the A / D converters 3 and 3a.

Here, the peak detectors 4 and 4a, when there is no overflow signal for a certain period of time (t),
The held peak value is lowered by 1 LSB (Least Significant Bit, least significant bit). This series of operations is intended to effectively use the dynamic range of the A / D converters 3 and 3a together with the image signal,
This operation is always performed during the reading operation of the document. Generally, in the case of simple binarization, the time constant (t) is made small to improve the followability so that the background of the document is not read. However, in the case of halftone processing, the density uniformity of the document is improved. The time constant is often increased (or made infinite) to keep trackability. The control unit 11 controls all the conditions and timings for reducing the peak value.

On the other hand, the shading-corrected data is
The MTF correction unit 7, 7a is sent to the MTF correction unit 7,
The blur of the optical system and the quantization is corrected by 7a. In this embodiment, it is assumed that the MTF correction coefficient that defines the strength of correction by the MTF correction units 7 and 7a can be selected from several types. Then, the selection setting is performed by the control unit 1.
The control signal from 1 is used. It should be noted that it is also possible to use a multiplexer or the like to select data that is not MTF-corrected data. The data thus selected is sent to the γ correction units 8 and 8a, and the γ correction units 8 and 8a convert the image data, which is the reflectance proportional data from the input optical system, into the density proportional data. . In this embodiment, this conversion table can be selected from several types. Further, the γ correction may be effective in the halftone processing and may be passed through in the simple binarization.

The image data converted into the density proportional data by the γ correction units 8 and 8a is sent to the binarization processing units 9 and 9a, and is sent to the 2
The binarization processing units 9 and 9a convert this image data into binary data of 1 bit per pixel. In this conversion, simple binarization with a constant value suitable for a character image, or dither processing or error diffusion processing suitable for a halftone image such as a photograph is performed. Image data 14 and 1 binarized in this way
5 is sent to the control unit 11.

For example, when the image data 15 indicates image information having a high density, the control unit 11 has a high possibility that the information on the back surface of the original document of that portion is offset to the image information on the front surface of the corresponding portion. Therefore, a control signal 12 for controlling the operations of the peak detection unit 4, the MTF correction unit 7, the γ correction unit 8 and the like is sent to the front side image processing unit 1 so as to prevent the show-through. Further, when the image data 15 indicates image information with low density, or when the image data 15 indicates a white background,
Since there is no possibility of show-through, the control unit 11 does not send the control signal 12, and the front side image processing unit 1 uses the peak detection unit based on each parameter whose initial value is set in the command register 10. 4, MTF correction unit 7, γ correction unit 8
Etc. to control the operation.

When the control signal 12 from the control unit 11 is received by the command register 10, the front image processing unit 1 operates the peak detection unit 4, the MTF correction unit 7, the γ correction unit 8 and the like based on the control signal 12. To control. For example, FIG. 3 shows the decrease time constant when the overflow during shading does not occur with respect to the peak value of the image data applied as the upper reference voltage of the A / D converter 3 to the peak detection unit 4. As shown, it switches between two types. That is,
In simple binarization suitable for character images, by increasing the initial value that has a relatively small time constant (A in FIG. 3) (B in FIG. 3), an analog image due to back-side reflection is displayed. Make the signal drop relatively small. In addition, in halftone processing suitable for photographs and the like, the initial value is infinity (Fig.
C) of (1) is given a value so that the peak follows (FIG. 3B), the drop of the analog image signal is absorbed in the white dead zone region of the γ correction.

Further, for the MTF correction unit 7, the MTF correction that was enabled by default is turned off (disabled) so that the MTF correction is not performed, or the MTF used for the MTF correction is changed. The set value of the correction coefficient is weakened, that is, the correction effect is weaker than the initial set value.
By switching the setting to the correction coefficient, the emphasis correction of the decrease in the analog image signal in the white area on the front surface of the document due to the reflection of the image information on the back surface of the document is invalidated. As a result, the possibility that the binarization processing unit 9 misidentifies it as a black pixel is reduced. Further, for the γ correction unit 8, the γ correction table referred to during the γ correction is changed to a table in which the white side dead zone has a γ curve that is wider than the initial setting, as shown in FIG. The deterioration of the analog image signal due to the back surface reflection can be removed by γ conversion.

Next, the processing operation according to the present invention of the facsimile apparatus of this embodiment will be described with reference to FIG. Figure 5
3 is a flowchart showing an example of processing operation according to the present invention of the facsimile apparatus in FIG. 1. Note that the situation described in this flowchart is a case where only the front side of the document is read and the back side of the document is not read (the presence or absence of image information is detected). This is an operation to prevent show-through.

When the original is set and the operator inputs the start of the original reading operation and the reading of the original is started (step 501), in the image processing units 1 and 2 of FIG. 1, the control unit 11 of FIG. Initial values are set in the processing parameters (step 502). It should be noted that this initial setting is a set value on the assumption that the image information is written only on the front surface of the document. That is, the image processing setting does not consider the show-through. Regarding the image processing unit 2 of FIG. 1 that reads the image information on the back side of the document, the initial setting value of each processing parameter is set to read the image information on the back side as usual (here, the image information is always displayed on the front side of the document. May be set so that the image information on the front surface does not affect the rear surface) or a special setting for simply detecting the presence or absence of the image information on the rear surface.

Based on the binary image signal output from the back side image processing section 2 in FIG. 1, the control section 11 in FIG.
Determines whether there is an image on the back side (step 50).
3). This criterion is not particularly problematic in the present invention, but a criterion (algorithm) capable of making a macro determination in a wide area is preferable because it is sufficient to detect an image that requires attention to show-through. . For example, it is determined that an image is present when several pixels are continuously black, or an image is present in a certain area where black pixels are present.

When the controller 11 of FIG. 1 judges that there is an image on the back surface of the original by this judgment, it reads the image information on the front surface as described with reference to FIGS. The setting of each image processing parameter is set to be different from the initial setting (step 504). Then, based on the changed image processing parameters, or based on the initial setting value when it is determined that there is no image on the back side,
Several lines are read (step 505). As can be seen from the configuration of the facsimile apparatus shown in FIG. 2, these several lines determine the presence / absence of image information on the back surface of a certain portion in the sensor positional relationship in which the sensor for the back surface scans the document earlier. It also fills in the time difference between the surface of that portion and the surface being scanned by the front surface sensor, and also corresponds to the macro area processing which is ideal as the above-described image information presence / absence determination standard.

After reading several lines, it is determined whether reading of one page is completed (step 506).
If not, the process returns to step 503 to read the next few lines. In this way, whether or not information is recorded on the back side of the read document surface is checked for each several lines.
That is, recognition is performed for each area of the width of the document in the conveyance direction, and each parameter that defines image processing is determined according to the recognition result.
The show-through is prevented by dynamically changing each area. If the reading of one page is completed in the process of step 506, it is determined whether there is a next page (step 507). If there is a next page, step 50
Returning to the initial setting processing in 2, the document reading is ended (step 508).

In the above description, the setting change of the parameters in the front side image processing section 1 based on the image information reading operation of the back side image processing section 2 has been described, but even when the image information is read from both sides of the document, the front side image processing is performed. High-quality double-sided image information can be obtained by the unit 1 and the back-side image processing unit 2 controlling mutual parameter change switching based on the mutual image information reading operation. In this way, when the back side of the document is also read as image information, the image information on the front side always affects the image information on the back side. Therefore, in this case, with respect to the back side image processing unit 2, the initial value of each parameter is set to a value in consideration of the influence from the image information on the front side.

As described above with reference to FIGS. 1 to 5, in the facsimile apparatus of this embodiment, whether or not information is recorded on the back side of the read original surface is determined by the unit of the width of the original in the conveying direction. In this case, the show-through is prevented by dynamically changing each parameter that defines the image processing for each area according to the recognition result. In this way, by performing the show-through prevention control for each area, it is possible to process the show-through only for an area having a high possibility of the show-through, so that it is possible to perform processing by the image processing parameter different from that in the normal reading. While preventing the above, the original can be read without making the entire image thin, and high-quality image information can be read. As a result, a clear image without show-through can be transmitted, and unnecessary image information is not transmitted, so that communication efficiency can be improved. Further, it is possible to improve the utilization efficiency of the rear surface sensor, which has been conventionally unnecessary for reading image information of a single-sided original.

Further, for example, the peak follow-up time constants of the front surface and the back surface can be independently and dynamically set at any time, so that the image becomes thin while preventing the show-through when reading the image information on the front surface. Can be prevented. Also,
Whether or not to execute MTF correction, or the coefficient of MTF correction can be selectively set dynamically on the front surface and the back surface, so that the image can be thinned while accurately preventing the show-through on the background portion. Can be prevented. Also,
The γ correction tables for the front and back sides can be set independently and dynamically at any time, so even when reading image information on the front surface, especially for halftone reading of photo originals, etc. You can prevent it from becoming light.

The present invention is not limited to the embodiment described with reference to FIGS. 1 to 5, and various modifications can be made without departing from the scope of the invention. For example, in the present embodiment, the contact image sensor and the CCD are used as the document reading sensor, but in the present invention, there is no restriction on the type and combination of the sensors, and any sensor may be used. Further, as shown in FIG. 1, in the present embodiment, the front side image processing unit 1 and the back side image processing unit 2 have the same processing configuration, but different processing configurations do not pose a problem to the present invention. Further, as the operation during double-sided reading, in response to the setting of double-sided reading by the operator, the parameter initial settings of the front side image processing unit 1 and the back side image processing unit 2 are set in advance for mutual show-through prevention. The operation of setting the image processing parameter on the front side to the normal setting for the area where the back image is not detected is also effective.

[0033]

According to the present invention, the execution / non-execution of the show-through processing operation can be controlled for each predetermined range of one original, and image information from the partially partially double-sided original is recorded. It is possible to read with high quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a configuration of a facsimile apparatus of the present invention according to the present invention.

FIG. 2 is a side end view of the facsimile apparatus having the configuration shown in FIG.

FIG. 3 is an explanatory diagram showing an example of a time constant changing operation of the peak detection unit in FIG.

FIG. 4 is an explanatory diagram showing a change example of a γ curve based on a change of a γ correction table used in a γ correction unit in FIG. 1.

5 is a flowchart showing an example of processing operation according to the present invention of the facsimile apparatus in FIG.

[Explanation of symbols]

1: Front side image processing unit 2: Back side image processing unit 3, 3a:
A / D converters 4, 4a: peak detector 5, 5a: D
/ A converter, 6, 6a: Shading correction unit. 7, 7
a: MTF correction unit, 8, 8a: γ correction unit, 9, 9a: 2
Quantization processing unit 10, 10a: command register, 11:
Control section 12, 13 ,: Control signal, 14, 15: Image data, 21: Document guide, 22: Document separating / conveying roller, 2
3: Document transport roller, 24: Contact image sensor, 2
5: light source, 26: contact glass, 27: original discharge roller, 28: mirror, 29: lens, 40: CCD, 4
1: Paper output tray

Claims (6)

[Claims] 1. A reading device (front surface) of a document in a facsimile apparatus which performs image processing when reading image information of a document based on a preset parameter value in order to improve the quality of the image information as a result of the reading. The back side reading means for reading the image information on the back side (back side) of the document, and the parameter values are dynamically changed in response to the density change indicated by the image information read by the back side reading means. And a show-through preventing means for preventing show-through of the image information on the back side of the document. 2. The image information on both the front and back sides of an original is read at the same time, and when the image information on the original is read, the front side and the back side are individually set in advance in order to improve the quality of the image information as a reading result. In a facsimile apparatus that performs image processing on the image information on the front side and the back side of the document based on the parameter value, both of the above two types of image information are processed according to the density changes indicated by the image information read from the front side and the back side of the document. A facsimile apparatus comprising a show-through preventing means for dynamically changing the parameter value to prevent show-through of both image information on the front and back sides of the document. 3. The facsimile apparatus according to claim 1 or 2, further comprising MTF correction means for performing image processing by MTF correction for improving the quality of image information as the reading result. The show-through preventing unit changes the dynamic change of the parameter value to the MTF.
A facsimile apparatus, which is characterized by dynamically switching whether or not to perform correction. 4. The facsimile apparatus according to claim 1, further comprising MTF correction means for performing image processing by MTF correction for improving the quality of image information as the reading result. The show-through preventing unit changes the dynamic change of the parameter value to the MTF.
A facsimile apparatus characterized in that the correction means dynamically changes the set value of the MTF correction coefficient used for the MTF correction. 5. The facsimile apparatus according to claim 1, further comprising: a γ correction means for performing image processing by γ correction for improving the quality of the image information as the read result. The facsimile apparatus, wherein the image blur prevention means dynamically changes the parameter value by dynamically switching the γ correction table referred to by the γ correction means during the γ correction. 6. The facsimile apparatus according to claim 1, further comprising peak detection means for performing peak value detection processing for enhancing the quality of image information as the reading result, The facsimile apparatus, wherein the image capturing means dynamically changes the parameter value by dynamically changing a time period used by the peak detection means for tracking the detection of the peak value.