JP2003324585A - Image-forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image-forming apparatus, using a simple structure capable of preventing a set-off from occurring in reading both-sided originals. <P>SOLUTION: When a rear image prevention mode is set in an operation panel 20, and a pressure plate is in a closed state, in reading the image recorded on the original, a control section 40 makes a contact type image sensor 13 read the original with a light source of the sensor 13 turned on, to obtain reflection light multivalued image data. Also, the section 40 makes the sensor 13 read the original with the light source of the sensor 13 off, to obtain transmission light multivalued data. An operation section 60 determines multivalued image data, in which a set-off portion is removed from the reflection light multivalued image data, on the basis of the reflection light multivalued image data and the transmission light multivalued image data. The multivalued image data which are determined are recorded in a data-recording section 50. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, such as a digital copying machine, an image scanner, a facsimile machine, etc., having an original reading means.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a digital copying machine, an image scanner, a facsimile machine, etc., which is equipped with a document reading means, when a front side of a document having an image recorded on both sides is read, There is a problem that a so-called show-through phenomenon occurs in which the recorded image is transparent and is read together with the image recorded on the surface. Such show-through is likely to occur particularly when thin paper, which is easy to show the back side document, is used, or when the copy density is set to be high because the characters of the document are thin. Such a show-through problem becomes more noticeable as the frequency of handling originals with images recorded on both front and back sides increases due to the spread of copiers that read both front and back sides simultaneously and the promotion of reuse of the back side of used paper. It has become to.

As a measure for preventing show-through when reading a document, an operator who operates an image forming apparatus, such as a copying machine, first copies a document at a normal print density, and then a blur or show-through of the copied image occurs. The images were checked and recognized, and the print density was qualitatively set darker or lighter according to the degree, and the original was copied again.

In such a method, the operator is required to confirm the image quality and input the setting of the print density, and at the same time, the paper is wasted. Also, because the print density to be re-input is only set qualitatively,
In the copy after re-input, the front side image was blurred or the back side image (show-through) was not sufficiently removed, and it was necessary to repeatedly set the print density until good image quality was obtained. .

As a method of effectively solving such a problem, for example, as disclosed in Japanese Patent Laid-Open No. 2000-188668, reading portions having different optical characteristics are provided on the front and back surfaces, and the reading portions are provided. Has proposed a method of reading the front and back sides at the same time and performing arithmetic processing. Further, as disclosed in Japanese Patent Laid-Open No. 9-135344,
The light from the LED light source is radiated to the back of the document,
There is also proposed a method of turning off and turning on each line and removing the show-through component by the image data level correcting means.

[0006]

However, the former method requires a reading unit for simultaneously reading the front and back surfaces, while the latter method requires an LED light source for irradiating light from the back surface of the document. You will need it. Therefore, there is a problem that the structure including the control processing device that controls the reading unit or the LED light source becomes more complicated, and the device cost increases significantly.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming apparatus having a simple structure and capable of preventing occurrence of show-through when reading a double-sided original. To do.

[0008]

In order to achieve the above object, an image forming apparatus according to the invention of claim 1 is configured such that an original placed on an original table, which is openable and closable, is pressure-bonded from above. A pressure plate, a contact image sensor for reading an image recorded on a document placed on the document table, which is provided immediately below the document table, and the contact image when the image is read. Moving means for reciprocating the sensor along a predetermined direction; setting means for setting a show-through prevention mode that is a mode for performing a process for preventing show-through when reading a document having images recorded on both sides thereof; When the show-through prevention mode is set by the setting means and the pressure plate is in the open state, the contact is performed while the light source of the contact-type image sensor is turned on when reading the image recorded on the document. By obtaining the first multi-valued image data by causing the image sensor to read the document, and by causing the contact image sensor to read the document with the light source of the contact image sensor turned off. Control means for acquiring second multi-valued image data, and image data of a show-through portion is removed from the first multi-valued image data based on the first multi-valued image data and the second multi-valued image data. The present invention is characterized by comprising a calculating means for obtaining the multivalued image data and a recording means for recording the multivalued image data obtained by the calculating means.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the arithmetic means includes third multi-valued image data obtained by subtracting a predetermined density value from the second multi-valued image data. After comparing with the first multi-valued image data, and in the third multi-valued image data, after specifying a portion where the density value of the third multi-valued image data is larger than the density value of the first multi-valued image data , For the first multi-valued image data,
Multivalued image data obtained by removing the image data of the show-through portion from the first multivalued image data is obtained by performing a process of canceling the specified portion as noise.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, there is provided a pressure plate open / close detection means for detecting whether the pressure plate is in an open state or a closed state, and the control means is provided. When the show-through prevention mode is set by the setting means, when the signal indicating that the pressure plate is open is sent from the pressure plate opening / closing detection means, the setting of the show-through prevention mode is accepted. When the signal indicating that the pressure plate is in the closed state is sent from the pressure plate opening / closing detection means, the setting of the show-through prevention mode is rejected and a notification that the pressure plate is opened is performed. It is what

According to a fourth aspect of the invention, in the image forming apparatus according to the first or second aspect, there is provided a pressure plate open / close detection means for detecting whether the pressure plate is open or closed, and the control means is provided. When an instruction to start reading a document is sent after the show-through prevention mode has been set by the setting means, the pressure plate opening / closing detection means sends a signal indicating that the pressure plate is in the open state. At the same time, an instruction to start reading the original document is accepted, and on the other hand, when a signal indicating that the pressure plate is closed is sent from the pressure plate opening / closing detection means, the instruction to start reading the original document is rejected, It is characterized in that a notification to the effect that the pressure plate is opened is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining a document reading unit in the image forming apparatus.

The image forming apparatus of this embodiment, as shown in FIGS. 1 and 2, has a document reading section, an operation panel (setting means) 20, a display section 30, a control section 40, and a data recording section 50. And a calculation unit 60. Further, the document reading unit includes a document table glass 11, a pressure plate (not shown), a pressure plate opening / closing detection unit 12, an image reading unit 13, and a moving unit 14.

The document table glass 11 is for placing the document 2 thereon. The pressure plate is for pressing the document 2 placed on the platen glass 11 from above, and is openably and closably installed. The pressure plate opening / closing detection means 12 detects whether the pressure plate is in an open state or a closed state. A signal from the pressure plate open / close detection means 12 is sent to the control unit 40.

The image reading means 13 is for reading the image recorded on the original 2 placed on the original table glass 11. In the present embodiment, the image reading unit 13 is a contact image sensor (CIS).
Will be used. As shown in FIG. 2, the CIS 13 is provided immediately below the document table glass 11 and has a light source 13a and a light receiving portion 13b. When the light source 13a is turned on, the light from the light source 13a is applied to the original 2 via the original table glass 11. Then, the light reflected by the original 2 is received by the light receiving portion 13b, whereby the image recorded on the original 2 is read. CIS13 is a means of transportation 1
An image reading operation is performed while moving in the left-right direction by 4. The operations of the CIS 13 and the moving means 14 are controlled by the controller 40.

On the operation panel 20, a reading start switch for giving an instruction to start reading a document (for example, an instruction to start copying in the case of a copying machine) and a show-through prevention mode are set. A mode setting switch and the like are provided for this purpose. The show-through prevention mode will be described in detail later. Instructions and setting contents input from the operation panel 20 are sent to the control unit 40. Further, the display unit 30 has
Various setting information and predetermined messages are displayed.

The control unit 40 controls the respective units and controls the shift to the show-through prevention mode.
The data recording unit 50 records multi-valued image data obtained by reading an image recorded on a document by the CIS 13, and multi-valued image data obtained as a result of calculation in the show-through prevention mode as described later.

Next, the show-through prevention mode will be described. The show-through prevention mode is a mode for performing a process for preventing so-called show-through, in which the image on the back side is transparent and is read together with the image on the front side when the document 2 on which the image is recorded on both the front side and the back side is read. Is. Here, in the present embodiment, the surface of the document 2 is a surface on which an image is to be read, that is, a surface facing the document table glass 11 when the document 2 is placed on the document table glass 11. Say.

When the show-through prevention mode is set on the operation panel 20, the control section 40 determines whether the pressure plate is in the open state or the closed state based on a signal from the pressure plate opening / closing detecting means 12. The control unit 40, when the pressure plate is in the open state,
Accepts show-through prevention mode settings. On the other hand, when the pressure plate is in the closed state, the setting of the show-through prevention mode is rejected and, for example, a message “Please open the pressure plate” is displayed on the display unit 30.

The image reading operation in the show-through prevention mode is different from the image reading operation in the normal mode other than the show-through prevention mode. In the show-through prevention mode, it is necessary to acquire two types of multi-valued image data. In the show-through prevention mode, the control unit 40 first, as in the case of the normal mode, as shown in FIG. 2A, while the CIS 13 is moving forward from the left side to the right side, the light source of the CIS 13 is moved. 13a is turned on.

At this time, the light from the light source 13a is reflected by the original 2 through the original table glass 11, and the reflected light is received by the light receiving portion 13b, whereby multi-valued image data is acquired. Next, as shown in FIG. 2B, the control unit 40 turns off the light source 13a while the CIS 13 moves backward from the right side to the left side. At this time, external light is transmitted through the document 2 and the platen glass 11, and the transmitted light is received by the light receiving section 13b, whereby multi-valued image data is acquired. That is, the multi-valued image data of the document 2 is acquired under external light while the light source 13a is turned off.
Here, the former multi-valued image data obtained by receiving reflected light when the light source 13a is turned on is "reflected light multi-valued image data (first multi-valued image data)", and transmitted light is received when the light source 13a is off. The latter multi-valued image data obtained in this manner will also be referred to as "transmitted light multi-valued image data (second multi-valued image data)".

The reflected light multi-valued image data thus obtained is recorded in the data recording section 50. On the other hand, regarding the transmitted light multi-valued image data, the transmitted light converted multi-valued image data (third multi-valued image data) obtained by converting the transmitted light multi-valued image data is recorded in the data recording unit 50. I will decide. The transmitted light multi-valued image data is the light source 1 of CIS13.
This is because the image is very dark because it is acquired with 3a turned off. As the transmitted light converted multivalued image data, for example, the one obtained by reducing the density value of the transmitted light multivalued image data to ½ is used.

FIG. 3 is a diagram for explaining the contents of the processing in the show-through prevention mode. Now, on the surface, "AB
The letter "C" is recorded, and the letters "AB"
Consider a double-sided document in which the character "<E <" is recorded at a position different from the position corresponding to the position where the character "C" is recorded. FIG. 3A shows a reflected light multi-valued image obtained from the reflected light multi-valued image data when such a double-sided original is read, and reflected light multi-valued image data along the broken line shown in the image. . Further, FIG. 3B shows a transmitted light converted multi-valued image obtained from the transmitted light converted multi-valued image data when the double-sided original is read, and the transmitted light converted multi-valued image along the broken line shown in the image. Multi-image data is shown.

As shown in FIG. 3A, show-through has occurred in the reflected light multi-valued image. As can be seen from the reflected light multi-valued image data along the broken line shown in the image, “A
The density value of the character portion "BC" is "10", the density value of the show-through portion is "3", and the density value of the background portion of the document is "0". On the other hand, as shown in FIG. 3B, in the transmitted light converted multi-valued image, the characters on the back surface are clearly shown, and the background of the document is included as noise. As can be seen from the transmitted light conversion multi-valued image data along the broken line shown in the image, the density value of the character portion "ABC" and the show-through portion is "6", and the density value of the background portion of the document. Is "3".

When in the show-through prevention mode, the arithmetic unit 60 removes the image data of the show-through portion from the reflected light multi-valued image data based on the reflected light multi-valued image data and the transmitted light multi-valued image data. The process of obtaining the image data (show-through prevention process) is performed. Specifically, the calculation unit 6
For 0, first, the transmitted light converted multi-valued image data obtained by subtracting a predetermined density value from the transmitted light converted multi-valued image data is compared with the reflected light multi-valued image data. A portion where the density value of the transmitted light converted multi-valued image data is larger than the density value of the light multi-valued image data is specified. After that, the reflected light multi-valued image data is subjected to a process of canceling the specified portion as noise to obtain multi-valued image data in which the image data of the show-through portion is removed from the reflected light multi-valued image data. .

In the present embodiment, the following processing is performed as processing for canceling the specified portion as noise in the reflected light multi-valued image data. That is,
The calculation unit 60 first subtracts transmitted light converted multivalued image data from reflected light multivalued image data, and then adds reflected light multivalued image data to the multivalued image data obtained by the subtraction.
In the multi-valued image data obtained by such processing, the difference between the density value of the image portion recorded on the document surface and the density value of the show-through portion and the background portion of the document becomes outstanding.
Next, in the multi-valued image data after the addition, the calculation unit 60 sets a predetermined threshold value within the range between the density value of the image portion recorded on the document surface and the density value of the show-through portion.
After that, threshold processing is performed on the multivalued image data after the addition using the set threshold.

As an example, the right side of FIG.
3A shows multi-valued image data obtained by subtracting the transmitted light converted multi-valued image data of FIG. 3B from the reflected light multi-valued image data of FIG. 3A and then adding the reflected light multi-valued image data of FIG. . In the multi-valued image data after such addition, the density of the character portion "ABC" is 10+ (10-6) = 16,
It is "16". The density of the show-through portion is 3+ (3-
Since 6) = 0, it is “0”. The density of the background portion of the document is "-3" from 0+ (0-3) =-3. Therefore, if the threshold value is set to “0” or a range of “0” or more and less than “16” in the multivalued image data after the addition, the calculation unit 60 performs the threshold processing,
It is possible to obtain a multi-valued image in which show-through is completely removed.
On the left side of FIG. 3C, an image obtained by setting the threshold value to “0” and performing threshold processing on the multivalued image data after the addition is shown.

Next, an operation procedure when the double-sided original is read in the show-through prevention mode in the image forming apparatus of this embodiment will be described.

First, the operator sets the original 2 on the original table glass 11. At this time, the pressure plate is not closed and is left open. Next, the operator presses the mode setting switch on the operation panel 20 to set the show-through prevention mode. A signal indicating that the show-through prevention mode has been set is sent to the control unit 40.

When the control unit 40 receives a signal indicating that the show-through prevention mode has been set, it determines whether the pressure plate is in the open state or the closed state based on the signal from the pressure plate opening / closing detecting means 12. When the control unit 40 determines that the pressure plate is in the closed state, the control unit 40 rejects the setting of the show-through prevention mode, and the display unit 50
Display the message "Please open the pressure plate." On the other hand, when the control unit 40 determines that the pressure plate is in the open state, the control unit 40 receives the setting of the show-through prevention mode.

After that, when the operator presses the reading start switch of the operation panel 20, an instruction to start reading the original is sent from the operation panel 20 to the control section 40. As a result, the document reading operation in the show-through prevention mode is started.

In the document reading operation in the show-through prevention mode, the control section 40 first sends a signal to the CIS 13 to turn on the light source 13a and sends a signal to the moving means 14 to move the CIS 13 forward. This allows CIS
During the forward movement of 13, the reflected light multi-valued image data is acquired and recorded in the data recording unit 50. When the CIS 13 reaches the turning point on the right side, the control section 40 sends a signal to the CIS 13 to turn off the light source 13a and move the moving means 14
To the CIS 13 to move backward.

Thereby, the transmitted light multi-valued image data is acquired during the backward movement of the CIS 13. Then, the transmitted light multi-valued image data is converted into transmitted light converted multi-valued image data, and the transmitted light converted multi-valued image data is converted into the data recording unit 50.
Recorded in.

Next, the calculation unit 60 performs the show-through prevention processing based on the reflected light multi-valued image data and the transmitted light converted multi-valued image data recorded in the data recording unit 50 to remove the show-through. Obtain value image data. The obtained multivalued image data is recorded in the data recording unit 50. This completes the operation for reading the double-sided original in the show-through prevention mode.

Next, how the double-sided document actually appears and how it is processed will be schematically described. Figure 4
FIG. 4 is a diagram for schematically explaining how an actual double-sided original is processed. Here, as shown in FIG. 4A, the characters "ABC" are recorded on the front surface of the document, and the characters "EEE" are recorded on the back surface thereof. When such a double-sided original is read in the show-through prevention mode, the reflected light multi-valued image obtained from the reflected light multi-valued image data has the reverse image of the back side of the original as shown in FIG. 4B. It is projected with the image of. The transmitted light converted multi-valued image obtained from the transmitted light converted multi-valued image data is shown in FIG.
As shown in (c), while the ground appears as noise,
Not only the image on the front side but also the image on the back side is clearly projected. Then, in the image after the show-through prevention processing,
As shown in FIG. 4D, only the image on the surface is clearly projected.

In the image forming apparatus of this embodiment, when the show-through prevention mode is set and the pressure plate is in the open state,
When reading an image recorded on a document, the CIS reads the document while the light source of the CIS is turned on to acquire reflected light multivalued image data, and C
The transmitted light multi-valued image data is acquired by causing the CIS to read the document with the light source of the IS turned off. Then, the computing unit obtains multivalued image data in which the image data of the show-through portion is removed from the reflected light multivalued image data based on the acquired reflected light multivalued image data and transmitted light multivalued image data. Therefore, in the image forming apparatus of the present embodiment, it is possible to prevent the show-through when the double-sided original is read with a simple configuration.

The present invention is not limited to the above embodiment, but various modifications can be made within the scope of the gist thereof.

In the above embodiment, the case where the reflected light multi-valued image data is acquired during the forward movement of the CIS and the transmitted light multi-valued image data is acquired during the backward movement of the CIS has been described. In order to more reliably align the reflected light multi-valued image data with the transmitted light converted multi-valued image data when performing the subtraction processing of the value image data, C
The IS may be moved twice, and the reflected light multi-valued image data and the transmitted light multi-valued image data may be acquired when the CIS moves along the same direction.

Further, in the above-described embodiment, when the signal indicating that the show-through prevention mode has been set is sent, the control unit sets the show-through prevention mode based on the signal from the pressure plate opening / closing detecting means. The case of accepting or rejecting the above has been described. However, when a signal indicating that the show-through prevention mode has been set is sent, the control unit does not determine whether to accept or reject the setting of the show-through prevention mode, and then instructs to start reading the original. When is sent, it may be possible to determine whether to accept or reject the instruction to start reading the document based on the signal from the pressure plate opening / closing detection means.

[0040]

As described above, in the image forming apparatus according to the present invention, the show-through prevention mode is set by the setting means,
In addition, when the pressure plate is in the open state, when reading the image recorded on the document, the contact-type image sensor is made to read the document while the light source of the contact-type image sensor is turned on, so that the first multi-valued The image data is acquired, and the second multi-valued image data is acquired by causing the contact image sensor to read the document while the light source of the contact image sensor is turned off. Then, the calculating means obtains the multivalued image data by removing the image data of the show-through portion from the first multivalued image data, based on the acquired first multivalued image data and the second multivalued image data. . Therefore, with the image forming apparatus of the present invention, it is possible to prevent the occurrence of show-through when reading a double-sided original with a simple configuration.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an image forming apparatus that is an embodiment of the present invention.

FIG. 2 is a diagram for explaining a document reading unit in the image forming apparatus.

FIG. 3 is a diagram for explaining the content of processing in a show-through prevention mode.

FIG. 4 is a diagram for schematically explaining how an actual double-sided original is processed.

[Explanation of symbols]

2 ... manuscript, 11 ... manuscript platen glass, 12 ... pressure plate opening / closing detecting means, 13 ... CIS, 13a ... light source, 13b ...
・ Light receiving part, 14 ... Moving means, 20 ... Operation panel, 3
0 ... Display unit, 40 ... Control unit, 50 ... Data recording unit, 60 ... Computing unit

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5B047 AA01 BA02 BA07 BB02 BC11                       BC14 CA07 DC20                 5C072 AA01 BA02 CA05 DA25 EA07                       LA02 LA07 UA20 WA01 WA02                       XA01                 5C077 LL02 MM27 PP25 PP47 PQ12                       PQ25 SS01 TT06

Claims (4)

[Claims] 1. A pressure plate configured to be openable and closable to press a document placed on a document table from above, and a document plate provided directly below the document table and mounted on the document table. Contact image sensor for reading the image recorded on the document, moving means for reciprocating the contact image sensor along a predetermined direction at the time of reading the image, and a document for recording the image on both sides of the document. Setting means for setting the show-through prevention mode, which is a mode for preventing show-through during reading, and the set-through prevention mode set by the setting means, and when the pressure plate is in the open state, When the recorded image is read, the first multi-valued image data is obtained by causing the contact image sensor to read the document while the light source of the contact image sensor is turned on. In addition, the control unit that acquires the second multi-valued image data by causing the contact type image sensor to read the document in a state where the light source of the contact type image sensor is turned off, and the first multi-valued image data. And the second multi-valued image data, the multi-valued image data obtained by the operation means, the multi-valued image data obtained by removing the image data of the show-through portion from the first multi-valued image data, An image forming apparatus comprising: a recording unit that records data. 2. The calculating means compares the third multi-valued image data obtained by subtracting a predetermined density value from the second multi-valued image data with the first multi-valued image data to obtain the third multi-valued image data. In the value image data, after specifying a portion in which the density value of the third multi-valued image data is larger than the density value of the first multi-valued image data, the specified portion of the first multi-valued image data is specified. The image forming apparatus according to claim 1, wherein the multivalued image data in which the image data of the show-through portion is removed from the first multivalued image data is obtained by performing a process of canceling out as noise. 3. A pressure plate opening / closing detection means for detecting whether the pressure plate is in an open state or a closed state, and the control means is configured to set the pressure plate when the show-through prevention mode is set by the setting means. When a signal indicating that the pressure plate is in the open state is sent from the opening / closing detection means, the show-through prevention mode setting is accepted, while a signal indicating that the pressure plate is in the closed state is received from the pressure plate opening / closing detection means. 3. The image forming apparatus according to claim 1, wherein when sent, the setting of the show-through prevention mode is rejected and a notification that the pressure plate is opened is issued. 4. A pressure plate opening / closing detection means for detecting whether the pressure plate is in an open state or a closed state, wherein the control means sets the original document after the show-through prevention mode is set by the setting means. When an instruction to start reading is sent, when the signal indicating that the pressure plate is in the open state is sent from the pressure plate opening / closing detection means, the instruction to start reading the original document is accepted, while the pressure plate is opened. When a signal indicating that the pressure plate is in the closed state is sent from the opening / closing detection means, an instruction to start reading the document is rejected and a notification that the pressure plate is opened is issued. The image forming apparatus according to item 1 or 2.