JP5784467B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including an original reading unit that reads an original placed on a platen glass, and more particularly to an image forming apparatus having an original size determination function.

  2. Description of the Related Art Conventionally, an electronic copying machine, a facsimile, and the like are known as an image forming apparatus provided with a document reading device that reads a document such as a photograph or document on a platen glass. In such an image forming apparatus, there is known an apparatus that first determines a document size of a document placed on a platen glass, and controls reading, selection of a sheet to be printed, and the like based on the determined document size. .

  As a document size detection method, it has been proposed to use image data read by a scanner that reads a document (see, for example, Patent Document 1). In Patent Document 1, the document scanning process is divided into two times in order to determine and remove a region outside the document from the image read from the document with the platen cover opened. Even if external light such as a fluorescent light is reflected on the reading surface by setting the threshold of the original recognition density level to the white side of the image data read in the first scan, These portions are deleted to obtain a rectangular area of the document. Next, in the first rectangular area in the second scan, an original recognition density level threshold value that can detect a gray portion is set to obtain a final original area, and an image that replaces the area other than the original area with white pixels Processing is in progress.

JP 2001-157018 A

  However, in the prior art of Patent Document 1, when a light source such as a fluorescent lamp is installed near the platen glass and the amount of external light is large, the threshold of the document recognition density level can be increased to the white side than usual. There is a problem that an area in which external light is reflected may be recognized as a document. If there is a high density background color at the edge of the document, the high density background color portion may not be recognized as a document and replaced with white pixels.

  In view of the above problems, the object of the present invention is to solve the problems of the prior art, and to make the document area highly accurate even when the amount of external light is large or there is a high density background color at the edge of the document. It is an object of the present invention to provide an image forming apparatus that can be recognized by the above.

The image forming apparatus of the present invention is an image forming apparatus that reads an image data by scanning a document placed on a platen glass while moving the scanner in the sub-scanning direction, and the document feeding unit is opened, Normal image data is acquired by a first scan in which the light source of the scanner is set to a normal light amount, and comparison image data is acquired in a second scan in which the light source of the scanner is set to a comparative light amount that is larger than the normal light amount. Compare the pixel density of the original reading means for acquiring the normal image data and the comparison image data for each pixel, and specify an area where the difference in pixel density is larger than a preset difference threshold as the original area A document area determination unit configured to determine whether the document area determination unit has a value obtained by adding the difference threshold value to the maximum density in the normal image data. Region at concentrations equal to or greater than the threshold which is set to be below is characterized in that identifying the original area.
Furthermore, in the image forming apparatus of the present invention, the first scan and the second scan may be executed by the reciprocation of the scanner.
Furthermore, the image forming apparatus of the present invention may further include a print control unit that prints the normal image data in the document area on a recording sheet by the document area determination unit.
Further, the image forming apparatus according to the present invention may further comprise an image processing means for replacing the normal image data other than the original area with white pixels by the original area determining means.

  According to the present invention, normal image data is acquired by the first scan in which the light source of the scanner is set to the normal light amount, and for comparison in the second scan in which the light source of the scanner is set to the comparison light amount different from the normal light amount. The image data is acquired, the pixel densities of the normal image data and the comparison image data are compared for each pixel, and an area where the difference in pixel density is larger than a preset threshold is specified as a document area. Thus, even when the amount of external light is large or there is a high density background color at the edge of the document, the document area can be recognized with high accuracy.

1 is a schematic cross-sectional view showing an internal configuration of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a block diagram illustrating a schematic configuration of the image forming apparatus illustrated in FIG. 1. 5 is a flowchart for explaining a document area determination operation in the embodiment of the image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating an example of placing a document on the platen glass illustrated in FIG. 1. It is a figure which shows the example of image data read by the scanner shown in FIG.

Next, embodiments of the present invention will be specifically described with reference to the drawings.
An image forming apparatus 1 according to the present embodiment is a copying machine. Referring to FIG. 1, a document reading unit 2, a document feeding unit 3, a body unit 4, a stack tray 5, and an operation unit 6 are provided. I have. The document reading unit 2 is disposed on the top of the main body unit 4, and the document feeding unit 3 is disposed on the top of the document reading unit 2. The stack tray 5 is disposed on the recording paper discharge port 41 side of the main body unit 4, and the operation unit 6 is disposed on the front side of the image forming apparatus 1. The document feeding unit 3 is configured to be retractable, and the upper surface of the document reading unit 2 can be opened by opening the document feeding unit 3 upward.

  The operation unit 6 is provided with a liquid crystal display unit 61 and operation buttons 62. The user operates the operation unit 6 to input an instruction, thereby performing various settings of the image forming apparatus 1 and executing various functions such as image formation. The liquid crystal display unit 61 displays the state of the image forming apparatus 1, displays the image forming status and the number of copies, and can be used as a touch panel to perform various settings such as functions such as double-sided printing and black-and-white reversal, magnification setting, and density setting. It has become. As the operation button 62, a start button for instructing the user to start image formation, a stop / clear button used when the image formation is stopped, etc., and used for setting various settings of the image forming apparatus 1 to a default state. A reset button, a numeric keypad and the like are provided.

  The document reading unit 2 includes a scanner 21, a platen glass 22, a document reading slit 23, and an open / close sensor 24. The scanner 21 includes a light source 25 using an LED (Light Emitting Diode), a CCD (Charge Coupled Device) sensor as a light receiving unit, and the like, and is configured to be movable in the document conveyance direction by the document feeding unit 3. Lighting of the light source 25 is controlled by the drive circuit 26. The drive circuit 26 can adjust the light amount of the light source 25 by causing the light source 25 to blink at a predetermined cycle, for example, by turning on the light source 25 by PWM control. In the present embodiment, the light quantity of the light source 25 can be switched between two levels, a normal light quantity used when reading a document and a comparative light quantity that is larger than the normal light quantity. The platen glass 22 is a document table which is made of a transparent member such as glass and is disposed on the upper surface of the document reading unit 2. The document feeding unit 3 functions as a platen cover that opens and closes the upper surface of the platen glass 22. By opening the document feeding unit 3 upward, the upper surface of the platen glass 22 is opened and a document can be set on the platen glass 22. Become. The document reading slit 23 has a slit formed in a direction perpendicular to the document transport direction by the document feeder 3. The open / close sensor 24 is a platen cover open / close detection unit that detects open / close of the document feeder 3.

  The document feeding unit 3 includes a document placement unit 31, a document discharge unit 32, and a document transport mechanism 33. The originals placed on the original placement unit 31 are sequentially fed out one by one by the original conveyance mechanism 33, conveyed to a position facing the original reading slit 23, and then discharged to the original discharge unit 32.

  When reading of a document is instructed by the operation button 62 of the operation unit 6 in a state where no document is placed on the document placement unit 31 or in an opened state where the document feeding unit 3 is opened, the document is placed on the platen glass 22. The placed document is scanned. When reading a document placed on the platen glass 22, the scanner 21 is moved to a position facing the platen glass 22, and scans the document placed on the platen glass 22 in the sub-scanning direction indicated by arrow A. The image data is acquired by reading the image data, and the acquired image data is output to the main unit 4.

  When reading of the document is instructed by the operation button 62 of the operation unit 6 in a state where the document is placed on the document placing unit 31, the document conveyed by the document feeding unit 3 is read. When reading the document conveyed by the document feeding unit 3, the scanner 21 is moved to a position facing the document reading slit 23, and the document feeding operation by the document feeding unit 3 is performed via the document reading slit 23. The document is read synchronously to acquire image data, and the acquired image data is output to the main unit 4.

  The main body unit 4 includes the recording unit 7, and includes a paper feeding unit 42, a paper conveyance path 43, a conveyance roller 44, and a discharge roller 45. The paper feed unit 42 includes a plurality of paper feed cassettes 42a1 to 42an and paper feed rollers 42b1 to 42bn that feed recording sheets from the paper feed cassettes 42a1 to 42an one by one to the paper transport path 43. The paper feed rollers 42b1 to 42bn, the transport roller 44, and the discharge roller 45 function as a transport unit, and the recording paper is transported. The recording paper fed to the paper transport path 43 by the paper feed rollers 42 b 1 to 42 bn is transported to the recording unit 7 by the transport roller 44. Then, the recording paper on which recording is performed by the recording unit 7 is discharged to the stack tray 5 by the discharge roller 45.

  The recording unit 7 includes a photosensitive drum 71, an exposure unit 72, an image forming unit 73, a transfer unit 74, and a fixing unit 75. The exposure unit 72 is an optical unit including a laser device, a mirror, and the like, and outputs a laser beam based on image data to expose the photosensitive drum 71 to form an electrostatic latent image on the surface of the photosensitive drum 71. To do. The image forming unit 73 is a developing unit that develops the electrostatic latent image formed on the photosensitive drum 71 using toner, and forms a toner image based on the electrostatic latent image on the photosensitive drum 71. The transfer unit 74 transfers the toner image formed on the photosensitive drum 71 by the image forming unit 73 to a recording sheet. The fixing unit 75 heats the recording paper on which the toner image is transferred by the transfer unit 74 to fix the toner image on the recording paper.

  FIG. 2 is a block diagram illustrating a schematic configuration of the image forming apparatus 1. The document reading unit 2, the document feeding unit 3, the transport unit (feed rollers 42 b 1 to 42 bn, the transport roller 44, the discharge roller 45), the operation unit 6, and the recording unit 7 are connected to the control unit 8. The operation is controlled by 8. The control unit 8 is connected to an image processing unit 9, a storage unit 10, and a document area determination unit 11.

  The control unit 8 is an information processing unit such as a microcomputer including a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The ROM stores a control program for controlling the operation of the image forming apparatus 1. The control unit 8 reads out a control program stored in the ROM and develops the control program in the RAM, thereby controlling the entire apparatus according to predetermined instruction information input from the operation unit 6.

  The image processing unit 9 is means for performing predetermined image processing on the image data. For example, image improvement processing such as enlargement / reduction processing, gradation adjustment, and density adjustment is performed.

  The storage unit 10 is a storage unit such as a semiconductor memory or an HDD (Hard Disk Drive). The storage unit 10 stores image data acquired by reading a document by the document reading unit 2, and stores various management information. Yes.

  The document area determination unit 11 includes normal image data acquired by scanning with the light source 25 set to a normal light amount, and comparison image data acquired by scanning with the light source 25 set to a comparative light amount larger than the normal light amount. The pixel density is compared for each pixel, and an area where the difference in pixel density is larger than a preset threshold is specified as the document area.

Next, the document area determination operation in the image forming apparatus 1 of the present embodiment will be described in detail with reference to FIGS.
The document area determination operation in the image forming apparatus 1 is executed when a document placed on the platen glass 22 is read with the document feeding unit 3 (platen cover) opened.

  Referring to FIG. 3, when the control unit 8 recognizes that the open / close sensor is turned on and the document feeding unit 3 is in the open state (step A <b> 1), the control unit 8 controls the document by the operation button 62 of the operation unit 6. The reading instruction (step A2) and the open / close sensor OFF (step A3) are monitored.

  If the document feeding unit 3 is closed without accepting a document reading instruction in step A2 and the opening / closing sensor is detected OFF in step A3, the control unit 8 performs the following steps without performing the subsequent steps. The judgment operation is terminated. If it is detected in step A3 that the open / close sensor is ON, the process returns to step A2.

  When the operation button 62 of the operation unit 6 is operated and a document reading instruction is received in step A2, the control unit 8 instructs the document reading unit 2 to perform forward scanning with the light source 25 set to a normal light amount. The document reading unit 2 instructed to perform the forward scan controls the drive circuit 26 to set the light source 25 to the normal light amount (step A4), and moves the scanner 21 in the sub-scanning direction indicated by the arrow A in FIG. A forward scan for reading the entire readable range of the platen glass 22 is executed. The image data acquired by the forward scan is stored in the storage unit 10 as normal image data by the control unit 8 (step A5).

  In FIG. 4, a document A having a relatively low density background color and a document B having a relatively high density background color are placed on the platen glass 22, and the area including the document B has strong external light. An example of a reflected area is shown. Also, FIG. 5A shows an example of normal image data in the sub-scanning direction X line shown in FIG. 4 acquired by normal scanning. The pixel density of the original B and the pixel density of the reflection area are shown. Therefore, it is difficult to specify the area of the document B. In the example shown in FIG. 5A, the pixel density of the original B is slightly higher than the pixel density of the reflection area. However, depending on the background color of the original B, the pixel density of the original B may be high. It is also conceivable that the pixel density is less than or equal to.

  Next, after the forward scan is completed, the control unit 8 instructs the document reading unit 2 to perform the reverse scan with the light source 25 set to the comparative light amount. The reverse scan instruction is issued before the scanner 21 returns to the home position after the forward scan is completed, and the forward scan and the reverse scan are executed by the reciprocating operation of the scanner 21.

  The document reading unit 2 instructed to perform the reverse scan controls the drive circuit 26 to set the light source 25 to a comparative light amount larger than the normal light amount (step A6), and the scanner 21 performs sub-scanning indicated by an arrow A in FIG. A reverse scan is performed to read the entire readable range of the platen glass 22 while moving in the direction opposite to the direction. The image data acquired by the reverse scan is output to the document area determination unit 11 as comparison image data (step A7).

  Next, the document area determination unit 11 compares the pixel densities of the normal image data stored in the storage unit 10 and the comparison image data from the document reading unit 2 for each pixel (step A8). An area where the difference between the two is larger than a preset threshold value is specified as a document area (step A9). Note that the comparison operation in step A8 may be performed after the image data acquired by the reverse scan is temporarily stored in the storage unit 10 as comparison image data.

  FIG. 5B shows an example of comparative image data for the X-line in the sub-scanning direction shown in FIG. 4 acquired by reverse scanning in which the light source 25 is set to a comparative light amount larger than the normal light amount. In FIG. 5B, when the comparison image data indicated by the solid line is compared with the normal image data indicated by the dotted line, the pixel density of the comparison image data in the areas of the original A and the original B is greater than the pixel density of the normal image data. Is also high. This is because, in the reverse scan, the light source 25 is set to a comparative light amount that is larger than the normal light amount, and therefore the amount of reflected light from the document A and the document B is increased in the regions of the document A and document B. The pixel density of the comparison image data is higher than the pixel density of the normal image data. On the other hand, in the areas other than the original A and the original B (including the reflected area), the pixel density of the comparison image data and the normal image data are not affected by the reflected light from the original A and the original B. There is almost no difference. Accordingly, areas where the difference in pixel density is larger than a preset difference threshold can be specified as the areas of the original A and the original B.

  When the document area is specified by the document area determination unit 11 in step A9, the control unit 8 controls the image processing unit 9 to convert normal image data other than the document area specified by the document area determination unit 11 into white pixels. At the same time as (maximum density) (step A10), the size of the recording paper on which the specified document area can be printed is specified (step A11), and the document area determination operation is terminated.

  Next, the control unit 8 controls the main body unit 4 to print the normal image data of the document region whose document region is specified by the document region determination unit 11 in step A9 on the recording paper of the size specified in step A11. Let Note that the size of the recording paper may be set by the user through the operation unit 6. In this case, the normal image data in the document area is enlarged or reduced by the image processing unit 9 in accordance with the size of the recording paper. You may make it do.

  In this embodiment, the comparative light amount is set to be larger than the normal light amount. However, even if the comparative light amount is set to be smaller than the normal light amount, the comparison image data and the normal image data are used in the original portion. A difference occurs in pixel density, and the document area can be specified. Further, the comparison image data may be acquired by the forward scan, and the normal image data may be acquired by the reverse scan.

  When the background color of the original is completely white, the pixel density is close to the maximum density in the original area in the normal image data. Therefore, there may be no difference between the pixel density of the comparison image data and the pixel density of the normal image data even in the document area. Therefore, it is preferable that the document area is specified as a document area even if there is no difference between the pixel density of the comparison image data and the pixel density of the normal image data above the density threshold value set in advance in the normal image data. Here, the density threshold value used for specifying the document area in the normal image data is obtained by adding the density threshold value and the difference threshold value used for comparing the pixel density of the comparison image data and the pixel density of the normal image data. It is better to set the value below the maximum density.

  As described above, in the present embodiment, normal image data is acquired by forward scanning with the light source 25 of the scanner 21 set to a normal light amount, and the light source 25 of the scanner 21 is set to a comparative light amount different from the normal light amount. The comparison image data is acquired by the set reverse scan, and the document area determination unit 11 compares the pixel densities of the normal image data and the comparison image data for each pixel, and the difference in pixel density is set in advance. Since the area larger than the threshold is specified as the original area, the original area can be recognized with high accuracy. That is, the area where the document is not placed can be removed because there is no difference between the normal image data and the comparison image data even if the amount of external light is large, and the area where the document is placed is Even if there is a high-density background color at the edge of the document, a difference occurs between the normal image data and the comparison image data, and the document region can be specified. Further, since the comparison image data can be acquired during a series of operations for acquiring the normal image data (reciprocating motion of the scanner 21), a new scan operation is not required, The document area can be specified at the same time.

  Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a suitable number, position, shape, and the like in practicing the present invention. In each figure, the same numerals are given to the same component.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Original reading part 3 Original feeding part 4 Main body part 5 Stack tray 6 Operation part 7 Recording part 8 Control part 9 Image processing part 10 Storage part 11 Original area determination part 21 Scanner 22 Platen glass 23 Original reading slit 24 Open / close sensor 25 Light source 26 Drive circuit 31 Document placement section 32 Document discharge section 33 Document transport mechanism 41 Discharge port 42 Paper feed section 42a1-42an Paper feed cassette 42b1-42bn Paper feed roller 43 Paper transport path 44 Transport roller 45 Discharge roller 61 Liquid crystal display unit 62 Operation buttons 71 Photosensitive drum 72 Exposure unit 73 Image forming unit 74 Transfer unit 75 Fixing unit

Claims (4)

An image forming apparatus that reads an image data by scanning a document placed on a platen glass while moving a scanner in a sub-scanning direction,
Normal image data is acquired in a first scan in which the scanner light source is set to a normal light amount with the document feeding unit opened, and the light source of the scanner is set to a comparative light amount that is larger than the normal light amount. Original reading means for acquiring comparison image data in the second scan,
A document area determining unit that compares the pixel densities of the normal image data and the comparison image data for each pixel and specifies an area where the difference in pixel density is larger than a preset difference threshold as a document area; And
The document area determination means, in the normal image data, a region value obtained by adding said difference threshold is set density threshold above to below the maximum density, the image formation and identifies as the original area apparatus.   The image forming apparatus according to claim 1, wherein the first scan and the second scan are executed by reciprocation of the scanner.   3. The image forming apparatus according to claim 1, further comprising a print control unit that prints the normal image data of the document area on a recording sheet by the document area determination unit.   4. The image forming apparatus according to claim 1, further comprising an image processing unit that replaces the normal image data other than the original region with white pixels by the original region determination unit.

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