JP5642645B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that selects a recording paper size according to a document.

  Conventionally, a technique for identifying an image size in a document has been proposed (see, for example, Patent Document 1). In Patent Document 1, the image density for each pixel of image data read from a document is determined, and when it is determined as a pixel in the image area, the count value of the image position in the main scanning direction and the sub-scanning direction of the pixel is picked up. . Next, the picked-up count value is compared with the minimum and maximum values in the main scanning direction and the sub-scanning direction, and the minimum and maximum values in the main scanning direction and the sub-scanning direction are updated. Finally, after the document reading is completed, the image size is determined by analyzing the minimum and maximum values in the main scanning direction and the sub-scanning direction.

JP 2004-112479 A

  However, in the conventional technology, it is necessary to determine the background portion or the image portion based on the pixel density for each pixel, and the amount of information to be processed becomes enormous, so that the determination time of the image size becomes long. There was a problem that the cost was high. That is, assuming that the document reads A3 in the main scanning direction and the sub-scanning direction at 600 dpi, the number of pixels is about 70 million dots, and it is necessary to repeat the same processing about 70 million times.

  In view of the above problems, an object of the present invention is to solve the problems of the prior art, reduce the amount of information processing required for determining the image size, and shorten the image size determination time. An object of the present invention is to provide an image forming apparatus capable of reducing the cost.

An image forming apparatus according to the present invention reads a document and obtains image data indicating image density of each pixel, and adds the pixel density of each of a plurality of main scanning lines in the document in the sub-scanning direction. A histogram generation unit that generates a plurality of density histograms, and an image size determination unit that determines an image size based on the density histogram generated by the histogram generation unit. The image size determination unit includes a plurality of density histograms . The main scanning image width is specified for each of the density histograms, and the maximum main scanning image width of each specified is determined as the image size .
Further, in the image forming apparatus of the present invention, the histogram generation unit generates the density histogram in parallel with reading of the original by the original reading unit.
Further, in the image forming apparatus of the present invention, each time one main scanning line is read by the original reading unit until the main scanning line read by the original reading unit reaches a set number, A density histogram generation cycle in which pixel density is added in the sub-scanning direction to generate the density histogram is repeated until reading of the original by the original reading unit is completed .

  According to the present invention, a plurality of density histograms are generated by adding the pixel densities of a plurality of main scanning lines in a document in the sub-scanning direction, and the image size is determined based on the generated density histograms. By configuring, it is possible to significantly reduce the amount of information processing required for determining the image size rather than processing in units of pixels, and it is possible to determine the image size determination time and to reduce the cost. There is an effect that can be realized.

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. 3 is a flowchart for explaining a histogram generation operation by a histogram generation unit shown in FIG. 2. It is explanatory drawing for demonstrating operation | movement of the histogram production | generation part shown in FIG. 3 is a flowchart for explaining an image size determination operation by an image size determination unit shown in FIG. 2. FIG. 5 is an explanatory diagram for explaining a reading operation at the time of document size mixed loading according to the embodiment of the image forming apparatus according to the present invention.

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 on which the main body unit 4 is formed, and the operation unit 6 including a start key, a numeric keypad, and an LCD is disposed on the front side of the image forming apparatus 1. Has been.

  The document reading unit 2 includes a scanner 21, a platen glass 22, and a document reading slit 23. The scanner 21 includes an exposure lamp, a CCD (Charge Coupled Device) sensor, and the like, and is configured to be movable in the document transport direction by the document feeder 3. The platen glass 22 is an original table made of a transparent member such as glass. The document reading slit 23 has a slit formed in a direction orthogonal to the document transport direction by the document feeder 3.

  When reading a document placed on the platen glass 22, the scanner 21 is moved to a position facing the platen glass 22 and reads the document while scanning the document placed on the platen glass 22 to obtain image data. The acquired image data is output to the main unit 4. 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 is conveyed by the document feeding unit 3 through the document reading slit 23. The document is read in synchronization with the operation to acquire image data, and the acquired image data is output to the main body unit 4.

  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. The document feeding unit 3 is configured to be retractable, and the upper surface of the platen glass 22 can be opened by lifting the document feeding unit 3 upward.

  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 421 that store recording papers of different sizes or orientations, and a paper feed roller 422 that feeds the recording papers one by one from the paper feed cassette 421 to the paper transport path 43. Yes. The paper feed roller 422, 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 roller 422 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, document feeding unit 3, transport unit (paper feed roller 422, transport roller 44, discharge roller 45), operation unit 6, and recording unit 7 are connected to the control unit 8 and are controlled by the control unit 8. Operation controlled. In addition, a storage unit 9, an image processing unit 10, a histogram generation unit 11, and a document size determination unit 12 are connected to the control unit 8.

  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 storage unit 9 is a storage unit such as a semiconductor memory or an HDD (Hard Disk Drive), and includes image data acquired by reading a document by the document reading unit 5, a density histogram generated by a histogram generation unit 11 to be described later, The document size determined by the document size determination unit 12 is stored.

  The image processing unit 10 is a unit that performs predetermined image processing on the image data. For example, image improvement processing such as enlargement / reduction processing, density adjustment, and gradation adjustment is performed.

  The histogram generation unit 11 generates a density histogram obtained by adding the pixel densities of a plurality of main scanning lines in the sub-scanning direction, and stores the generated density histogram in the storage unit 9. The density histogram is generated in parallel with the reading of the document by the document reading unit 2, and a plurality of density histograms are stored in the storage unit 9 when the document reading is completed. For example, when the original is A3, the main scanning direction and the sub-scanning direction are read at 600 dpi, and the number of pixels in the sub-scanning direction is 9600 dots, the density histogram is generated for each of the 240 main scanning lines. Thus, 40 density histograms may be stored in the storage unit 9.

  The document size determination unit 12 determines the document size in the main scanning direction and the document size in the sub-scanning direction based on the plurality of density histograms stored in the storage unit 9, and outputs the determination result to the control unit 8. To do. In the present embodiment, the histogram generation unit 11 and the document size determination unit 12 are configured separately from the control unit 8. Thereby, by making the histogram generation unit 11 and the document size determination unit 12 hardware, the processing speed can be further increased and the load on the control unit 8 can be reduced. Note that the operations of the histogram generation unit 11 and the document size determination unit 12 may be set as a control program and executed by the control unit 8.

Next, the histogram generation operation by the histogram generation unit 11 will be described in detail with reference to FIGS.
When the document reading unit 2 starts reading the document, the histogram generation unit 11 sets 0 to the variable n (step A1), and monitors the input of image data for one main scanning line from the document reading unit 2. (Step A2). When image data for one main scanning line is input from the document reading unit 2, the histogram generation unit 11 performs an adding process of adding each pixel density of the image data for one main scanning line in the sub-scanning direction. (Step A3). Next, the histogram generator 11 increments the variable n (step A4), and determines whether or not the variable n has reached a preset number N (step A5).

  If the variable n has not reached the preset setting number N in step A5, the process returns to step A2, and the processing of steps A2 to A4 is performed until the variable n reaches the preset setting number N. Is repeated. As a result, each time image data for one main scanning line is input from the document reading section 2, the pixel density for one main scanning line is added in the sub-scanning direction, and a set number N of main scannings are added. A density histogram is generated in which the pixel density of each line is added in the sub-scanning direction.

  When the variable n reaches the preset number N in step A5, the histogram generation unit 11 outputs the generated density histogram and stores it in the storage unit 9 (step A6). Next, the histogram generation unit 11 determines whether or not scanning is completed, that is, whether or not reading of the original by the original reading unit 2 is completed (step A7).

  If the scan is not completed in step A7, the process returns to step A1, and the density histogram generation cycle of steps A1 to A6 is repeated until the scan is completed. Accordingly, for example, when reading the document shown in FIG. 4A, assuming that the number of dots in the sub-scanning direction is 9600 and the set number N is 240, 9600/240 = 40 density histograms h1 to h40 are generated. It will be. The 40th density histogram h40 generated at the end is generated at the end of scanning, and 40 density histograms h1 to h40 are stored in the storage unit 9 at the end of scanning. In FIG. 4A, the arrow X indicates the sub-scanning direction, the arrow Y indicates the main scanning direction, and C indicates the technical position when reading the document. 4B shows the ninth generated density histogram h9 when reading the original shown in FIG. 4A, and FIG. 4C shows the 31st generated density histogram h31. Each is shown.

Next, the document size determination operation by the document size determination unit 12 will be described in detail with reference to FIG.
First, when reading of a document is started by the document reading unit 2, the document size determination unit 12 sets 1 to a variable m (step B1), and monitors the generation of a density histogram by the histogram generation unit 11 (step B2). ). When the density histogram is generated by the histogram generation unit 11, the main scanning image width of the density histogram hm generated for the variable m is specified (step B3). The main scanning image width is specified by referring to FIGS. 4B and 4C, whether or not the pixel density exceeds a preset threshold value from the main scanning maximum size (7000 dots) toward the reference position C. First, a pixel having a pixel density exceeding a threshold value is first specified as the main scanning image width from the reference position C. It is determined whether the pixel density exceeds a preset threshold value from the reference position C toward the main scanning maximum size (7000 dots), and finally the pixel having the pixel density exceeding the threshold value is used as a reference. The main scanning image width from the position C may be specified.

  Next, the document size determination unit 12 increments the variable m (step B4), and determines whether the variable m has reached a preset number M (step B5). Note that the setting number M is the number of density histograms generated when reading a document. For example, when the number of dots in the sub-scanning direction is 9600 and the setting number N is 240, the setting number M is set to 40. The If the variable m has not reached the preset setting number M in step B5, the process returns to step B2, and the processes of steps B2 to B4 are performed until the variable m reaches the preset setting number M. Is repeated. Thus, the main scanning image width is specified for each of the density histograms h1 to hM generated by the histogram generation unit 11.

  When the variable m reaches the preset number M in step B5, the histogram generation unit 11 determines the maximum main scanning image width based on the main scanning image width specified for each of the density histograms h1 to hM. Is determined as the image size (step B6), and the document size determination operation is terminated. In the example shown in FIG. 4, the density histogram h9 shown in FIG. 4B generated ninth by the histogram generator 11 is the maximum main scanning image width, and the main scanning image width is determined as the image size. The determined image size is output to the control unit 8, and when image processing is performed thereafter, image processing, file formation, and output paper are determined according to the determined image size.

  In this embodiment, the maximum main scanning image width from the reference position C is determined as the document size. However, in the density histograms h1 to hM, the pixel density first exceeding the threshold value from the reference position C is determined. The maximum main scanning image width may be determined as a document size between a pixel having a pixel density and a pixel having a pixel density that first exceeds a threshold from the main scanning maximum size (7000 dots). Further, the document size in the sub-scanning direction may be determined based on the density histograms h1 to hM. That is, in the density histograms h1 to hM, the document size in the sub-scanning direction can be determined by setting the upper and lower main scanning image widths to “0” as blanks. In the example shown in FIG. 4A, the density histograms h1 to h6 and the density histograms h35 to h40 are blanks, and the width from the density histograms h7 to h34 can be determined as the document size in the sub-scanning direction.

  FIG. 6A shows an example in which originals of different sizes (A4R and A3) are set on the original placing part 31 of the original feeding part 3. In this way, when different sizes (A4R and A3) of originals are set on the original placing unit 31, the first original is read and a density histogram is generated as shown in FIG. Determine the image size. Next, as shown in FIG. 6C, the second original is similarly read, a density histogram is generated, and the image size is determined. As a result, the output paper can be determined for each image size. Note that the paper size is not limited to the actual size of the recording paper, but also the paper size when performing FAX transmission or file transmission.

  As described above, in the present embodiment, the histogram generation unit 11 generates a plurality of density histograms obtained by adding the pixel densities of the plurality of main scanning lines in the document in the sub-scanning direction, and the generated plurality of density histograms. By configuring the document size determination unit 12 to determine the image size based on the density histogram, the amount of information processing required for determining the image size can be greatly reduced rather than processing in units of pixels. As a result, the image size determination time can be obtained, and the cost can be reduced.

  Further, in the present embodiment, density histogram generation by the histogram generation unit 11 is performed in parallel with document reading by the document reading unit 2. That is, each time the main scanning line is read by the original reading unit 2, each pixel density is added in the sub-scanning direction until the main scanning line read by the original reading unit 2 reaches the set number. By repeating the density histogram generation cycle in which the density histogram is generated until the document reading unit 2 finishes reading the document, the time required to determine the document size can be determined.

  Further, in the present embodiment, the document size determination unit 12 specifies the main scanning image width for each of the plurality of density histograms, and determines the maximum main scanning image width of each specified as the image size. Easy to determine the image size.

  In this embodiment, a copying machine is shown as an example of the image forming apparatus according to the present invention. However, the image forming apparatus according to the present invention is not limited to this, and an apparatus having a document reading function. For example, it may be a facsimile machine, a printer, a multifunction peripheral (an image forming apparatus having functions such as a copy machine, a facsimile machine, and a printer).

  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 number, position, shape, and the like that are suitable for implementing 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 Storage part 10 Image processing part 11 Histogram generation part 12 Original size determination part 21 Scanner 22 Platen glass 23 Document reading slit 31 Document placement section 32 Document discharge section 33 Document transport mechanism 41 Discharge port 42 Paper feed section 43 Paper transport path 44 Transport roller 45 Discharge roller 71 Photosensitive drum 72 Exposure section 73 Image formation section 74 Transfer section 75 Fixing section 421 Paper feed cassette 422 Paper feed roller

Claims (3)

An original reading means for reading an original and acquiring image data indicating the image density of each pixel;
Histogram generating means for generating a plurality of density histograms by adding the pixel densities of the plurality of main scanning lines in the document in the sub-scanning direction;
Image size determination means for determining an image size based on the density histogram generated by the histogram generation means ,
The image size determination means specifies a main scanning image width for each of the plurality of density histograms, and determines the largest main scanning image width of each specified as the image size. apparatus.   The image forming apparatus according to claim 1, wherein the histogram generating unit generates the density histogram in parallel with reading of the original by the original reading unit.   Each time the main scanning line is read by the original reading unit, the respective pixel densities are added in the sub-scanning direction until the main scanning line read by the original reading unit reaches the set number. 3. The image forming apparatus according to claim 2, wherein a density histogram generation cycle for generating the density histogram is repeated until reading of the original by the original reading unit is completed.

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