JP4873733B2 - Document color / monochrome determination method, image reading apparatus, image forming apparatus, and image transmitting apparatus - Google Patents

Description

The present invention relates to an original color / monochrome determination method, an image reading apparatus, an image forming apparatus , and an image transmission apparatus . That is, the present invention relates to a color / monochrome determination method for an original to be read, an image reading apparatus having the function, an image forming apparatus including the same , and an image transmission apparatus .

  In a conventional color multifunction peripheral, there is a color multifunction peripheral that automatically determines whether it is a color original or a black and white original in a document reading operation, and controls the recording operation and image data transmission operation based on the determination result. There is also a color multi-function peripheral in which the user selects the original reading mode switching and performs color and black-and-white copy operations and data transmission operations.

  Various determination methods have been proposed for "AUTO COLOR SELECT (hereinafter referred to as ACS)", which is an automatic determination function for whether a color document or a monochrome document.

  In Patent Document 1, first, color / monochrome is determined for each pixel, then the color / monochrome of the block is determined from the number of color pixels in a certain block, and whether the document is color based on the number of blocks determined to be color. An ACS for determining whether it is black and white is disclosed.

  Patent Document 2 discloses a method of counting the number of pixels in which the difference between the RGB data of each pixel is larger than each threshold value, and determining that the original is a color document when the count value exceeds the count threshold value.

  In Cited Document 3, as a circuit for determining whether the background of the image is color or black and white, the ratio of the color pixels in the background image area is compared with a threshold value to determine whether the background is a color background.

  Further, in the cited document 4, when the difference between the maximum and minimum RGB values of each pixel is within a certain empirical range, it is determined as a color pixel, and when there are a plurality of such color pixels, judge.

Further, in Cited Document 5, an ACS region is set, and within the ACS region, the minimum value of the RGB data is subtracted from the values of the other two components, and the absolute value of the difference between the two values obtained is “color”. Get as "degree". Then, it is determined that the target pixel indicates a color pixel only when a specific continuity of a pixel having a saturation greater than a certain threshold value can be confirmed with respect to the target pixel. The color / monochrome of the document is determined based on the total number of pixels determined as such color pixels in the ACS area.
JP2001-22614 JP 2000-32279 A JP-A-5-122535 JP-A-2005-244682 JP2001-119589

  However, the ACS function of the document is composed of the image reading apparatus and the image processing, and a highly accurate ACS configuration is very expensive. For example, when the entire area of the original is stored in the memory and the ACS is performed by recognizing a certain color pixel or more, a very large memory is required. With A4 size 600 dpi 24-bit color, the memory capacity becomes nearly 100 Mbytes.

  On the other hand, a document reading apparatus generally has a configuration in which image information is read for each line by CCD or CIS. In particular, in a reading apparatus constituted by a CCD, as is well known, each of the RGB photosensors is mounted separately, so that each reading is performed not on the same line on the document but on the separate lines. . Therefore, a color image is formed by synthesizing each line of RGB by scanning reading of a document transport by an automatic document feeder (hereinafter referred to as ADF) and scanning reading of a reading mechanism by book reading.

  At this time, RGB composition failure (color misregistration) occurs due to transport unevenness due to document transport or scanning transport unevenness. In particular, it occurs at the boundary between black and white pixels. Such a color shift occurring at the boundary between the black pixel and the white pixel causes a malfunction in the color / monochrome determination of the document because the monochrome boundary of the image in FIG. 6 appears as a color thin line as shown in FIG.

  In order to reduce this unevenness in document conveyance, a large number of conveyance rollers are used to stabilize document conveyance. Since the number of conveying rollers is increased, the cost is naturally increased and the size of the apparatus is also affected.

  In principle, if the RGB optical sensors read the same line, no color misregistration will occur even if uneven conveyance or uneven scanning conveyance occurs. However, since RGB optical sensors are semiconductors, it is currently difficult to mount them on the same line. Therefore, by shortening the pitch (distance away) between the lines of the RGB photosensors, the RGB photosensors can read near lines. At present, there are CCDs with a two-line pitch. One line pitch is the limit for the arrangement.

  However, since the solution by the line pitch of the optical sensor is very costly, it is only used as an expensive device for office machines, and generally a CCD with a 12-line pitch is the mainstream in an inexpensive device. It is.

The present invention makes it possible to reduce the cost of the ACS function that has been used in office color multifunction peripherals and to mount the apparatus in a low-priced machine as a smaller device. Thus, a document color / monochrome determination method, an image reading apparatus, an image forming apparatus , and an image transmitting apparatus are provided to provide a practical ACS function to many users.

In order to solve such a problem, the image reading apparatus of the present invention is stationary in a reading mode for reading an image of a document while the document is conveyed from the supply side to the discharge side, and a platen on which the document is placed. An image reading apparatus having a reading mode for reading an image of a document, and paying attention to the number of pixels having saturation continuously appearing in a main scanning direction perpendicular to the document transport direction, whether a color document or a monochrome document Focusing on the color / monochrome determination means in the main scanning direction and the number of pixels with saturation appearing continuously in the sub-scanning direction parallel to the document conveying direction and a sub-scanning direction of the color / monochrome judging means, in a reading mode for reading an image of an original in the conveying rather than the main scanning direction of the color / monochrome judging unit, the sub-scanning direction of the color / monochrome determination means of In the reading mode for determining whether the document is a color document or a monochrome document based on the determination result and reading the image of the stationary document, the color / monochrome determination means in the sub-scanning direction or the color / monochrome in the main scanning direction Based on the determination result of the determination means, it is determined whether the original is a color original or a black and white original, and the color / monochrome determination means in the sub-scanning direction has a number of pixels having a saturation equal to or greater than a first threshold in the main scanning direction. First reading line detection means for detecting as a reading line having saturation a reading line having a number of pixels having consecutive pixels in the main scanning direction by a number equal to or greater than a second threshold value is detected by the first reading line detection means. The document having the read line having the saturation in the sub-scanning direction by the number equal to or greater than the third threshold is determined as a color document, and the saturation detected by the first read line detecting unit is included. Reader A first color / monochrome determination unit that determines a document that has only a number less than the third threshold in the sub-scanning direction as a monochrome document, and the color / monochrome determination unit in the main scanning direction includes: , A reading line having a pixel group continuously having a number of pixels having saturation equal to or greater than the fourth threshold in the main scanning direction is detected as a reading line having saturation. A second reading line detecting means, and a document having the saturation detected by the second reading line detecting means in the sub scanning direction by a number equal to or more than a sixth threshold value is determined as a color original, And a second color / monochrome determination unit that determines a document having the saturation detected by the second scanning line detection unit as a monochrome document for a document having a number less than a sixth threshold in the sub-scanning direction.

Here, before Symbol fourth threshold 50, the fifth threshold value is 2, the sixth threshold is 30. In the pixel having the saturation, the minimum value of the pixel values of the three components R, G, and B is subtracted from the values of the other components, and the absolute value of the difference between the obtained values is the seventh value. The pixel is larger than the threshold value.

Also provided is an image forming apparatus having the image reading apparatus, wherein image formation is controlled according to a determination result of whether the original is a color original or a black and white original. Also provided is an image transmission device comprising the image reading device, wherein image transmission is controlled according to a determination result of whether the document is a color document or a monochrome document .

According to the present invention, the ACS function used in the office color multi-function machine can be reduced in cost, and can be mounted on a low-priced machine with a reduced size. Therefore, it is possible to provide a document color / monochrome determination method, an image reading apparatus, an image forming apparatus , and an image transmitting apparatus for providing a practical ACS function to many users.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Example of Configuration of Image Reading Apparatus of Present Embodiment>
As an embodiment according to the present invention, an example applied to a multifunction machine having a copy and printer function and a facsimile function will be specifically described with reference to the drawings. The description will be given in the following order.
(1) Overall configuration of image reading apparatus (FIGS. 1 and 2A),
(2) Configuration of ACS (FIGS. 2B to 3B)
In the following embodiments, a color multi-function peripheral will be described as an example. However, the present invention is a technology related to image reading, and is not limited to a color multi-function peripheral, and can be applied to a device that performs image reading. Included in the invention. Further, in the present embodiment, an example of determining the color / monochrome of a document from a thin line constituting a character is shown, but this is an example and it is not necessary to be limited. The present invention only needs to provide a low-cost configuration that eliminates the influence of conveyance unevenness that occurs during conveyance of a document on the ACS.

(1) Example of Overall Configuration of Image Reading Apparatus FIG. 1 is a cross-sectional view of a main part of an image reading apparatus in a multifunction peripheral.

  The image reading apparatus according to the present embodiment includes an automatic document feeder (hereinafter referred to as ADF) 100 and a reader unit 200. The ADF 100 automatically conveys a plurality of documents one by one from the supply side to the discharge side. The reader unit 200 includes an image reading unit that reads the surface of a document conveyed by the ADF 100, and is also capable of reading a book-type document (reading the document fixed on a platen glass (stationary)).

(Configuration example of ADF100)
In this example, the ADF 100 has a U-turn type document transport path from the supply side to the discharge side, as shown in FIG. This transport path is composed of an upper transport path and a lower transport path.

  The ADF 100 includes a pickup roller 1 that picks up a document from a document bundle S placed on the document tray 20, and a separation roller 2 a and a separation pad 2 b that are arranged on the downstream side of the conveyance path from the pickup roller 1.

  A separation unit 2 that guides the documents picked up by the pickup roller 1 to the conveyance path one by one, and is disposed along the conveyance path downstream of the separation unit 2 along the conveyance path. The conveyance roller 3 and the conveyance roller 5 And have. In this embodiment, two transport rollers are provided, but one transport roller may be used.

  Next, a document edge sensor (hereinafter referred to as DES) 12 that is arranged on the downstream side of the conveyance path with respect to the conveyance roller 5 and detects the passage of the document and a document that is arranged on the downstream side of the conveyance path with respect to the reading position R1 are arranged along the conveyance path. Conveying rollers 6 and 7 for conveying are arranged along the conveying path. In addition, it has a discharge roller 8 that is arranged on the downstream side of the conveyance path with respect to the conveyance rollers 6 and 7 and discharges the original from the conveyance path, and a discharge tray 21 on which the original discharged by the discharge roller 8 is placed. In the present embodiment, two transport rollers and a discharge roller are provided on the downstream side of the transport path from the reading position R1, but only the discharge roller 8 may be provided. The CIS reading unit 30 at the reading position R2 between the conveying rollers 6 and 7 and the discharge roller 8 is a CIS for back side reading, but is not a main part of the present invention, and thus will not be described in detail.

(Configuration example of reader unit 200)
Next, the reader unit 200 includes an ADF platen glass 201 used when reading a document being conveyed conveyed by the ADF 100, and a book platen glass 202 as a document placement table on which a book type document can be placed. have. Below the book platen glass 202, there is a scanner unit 209 that integrally includes a lamp 203 for irradiating a document and a mirror 204 for guiding reflected light from the document to a predetermined optical path. Then, there are a mirror unit 205 and a lens 207 that integrally include a mirror 205a and a mirror 205b that guide reflected light guided by the mirror 204 to a predetermined optical path. Further, a CCD sensor 208 that obtains an optical image by guiding reflected light from the document by the mirror 204, the mirror unit 205, and the lens 207 is provided. With such a configuration, image information recorded on the original is optically read and photoelectrically converted to obtain image data.

  Here, the scanner unit 209 can reciprocate a predetermined image reading range below the book platen glass 202 so that an image of a document placed on the book platen glass 202 can be read. The operation of reading a document stationary on the book platen glass 202 in this way is referred to as fixed document reading.

  Further, as shown in FIG. 1, the scanner unit 209 can move to a position immediately below the reading position R <b> 1 set on the downstream side of the conveyance path 5 with respect to the conveyance roller 5 and on the upstream side of the conveyance path 6 with respect to the conveyance roller 6. Is arranged. By moving to the position immediately below the reading position R1, it is possible to read an image of the document when passing the reading position R1. Such an operation of reading a moving document is referred to as document flow reading.

  Similarly to the scanner unit 209, the mirror unit 205 is also arranged so as to be able to reciprocate within a predetermined range below the book platen glass 202.

  These scanner unit 209 and mirror unit 205 constitute a moving exposure scanning optical system. At this time, when the moving speed of the scanner unit 209 is V, for example, the moving speed of the mirror unit 205 is set using a mechanism such as a wire and a pulley so as to be 1/2 V that is half of the moving speed V. . By doing so, it is possible to perform an original image reading operation while keeping the optical path length from the original reading surface to the CCD sensor 208 constant.

  In this embodiment, a CCD sensor is used, but a contact image sensor (hereinafter CIS) may be used. An integrated reduction optical system using a CCD sensor may be used. In this example, a low-priced CCD is used, and although not shown, the RGB line spacing is 12-pitch pitch.

  Further, the image reading apparatus is connected to and mounted on the upper part of the image forming means 300 for recording an image based on image information read from the original by the image reading apparatus on a recording sheet (not shown) so as to be communicable with the image forming means 300. Is placed. If necessary, it can be used as an image forming apparatus, that is, a copying machine. Here, as the image forming unit 300, a thermal transfer method, a laser exposure method, an ink jet method, or the like can be used. The image forming unit 300 will not be described in detail because it is not a main part of the present invention.

  Next, the operation of the image reading apparatus of this example will be described.

  In FIG. 1, an ADF 100, which is an automatic document feeder, is fed from a document bundle S set on a document tray 20 with the document surface facing upward to a separation unit 2 by a pickup roller 1 in order from the top document. It is. Specifically, the separation unit 2 includes a separation roller 2a that comes into contact with the upper surface of the document supplied from the pickup roller 1, and a separation pad 2b that presses against the separation roller 2a so as to press the document from below. ing. With this configuration, the originals picked up from the original bundle S are separated one by one from the uppermost original.

  When reading the image of the document, the document separated from the document bundle S by the separation unit 2 passes through the transport roller 3 and is transported while being transferred to the transport roller 5 and the transport roller 6 to be read position R1. The document image is read while the document is being conveyed. Then, the paper is sequentially discharged from the conveying roller 7 onto the discharge tray 21 by the discharge roller 8.

  When the reader unit 200 reads an image on the surface of the document when the document conveyed by the ADF 100 passes the reading position R1, the following operation is performed. The scanner unit 209 of the reader unit 200 is moved directly below the ADF platen glass 201, and image information is read by the scanner unit 209 while the document is being conveyed on the reading position R1.

  Further, when reading an image of an original placed on the book platen glass 202, the following operation is performed. The scanner unit 209 is moved in a predetermined direction from a document set reference (not shown) as a predetermined position set below the book platen glass 202 to read image information.

  When an image of a document is read by the scanner unit 209, the lamp 203 is first turned on to irradiate the document. Then, the reflected light from the document surface is input to the CCD sensor 208 via the mirror 204, the mirror unit 205 and the lens 207. Then, the reflected light of the document input to the CCD sensor 208 is subjected to electrical processing such as photoelectric conversion and is subjected to normal digital processing to obtain image information of the document.

(Configuration example of control unit of image reading apparatus)
FIG. 2A is a block diagram illustrating a configuration example for controlling the image reading apparatus in FIG. 1.

  In FIG. 2A, reference numeral 400 denotes a scanner control unit that controls the entire scanner as an image reading apparatus. The scanner control unit 400 includes a CPU 410 for arithmetic control, a ROM 420 for storing fixed programs and data, a RAM 430 used as a work memory when the CPU 410 operates, and an external storage unit 440 such as a disk for storing programs and parameters.

  The scanner control unit 400 controls each unit of the image reading apparatus according to the processing procedure of the CPU 410 (see FIGS. 3A and 3B below).

  When the ADF 100 is used, the scanner control unit 400 recognizes a signal from each sensor 404, controls each mechanism shown in FIG. 1 by the ADF control unit 405, and conveys the document. At the same time, it recognizes signals from the sensors 404 and controls the document reading operation via the illumination / operation control unit 406.

  Analog data read by a photoelectric conversion element (CCD or the like) 401 is corrected by an analog correction & shading correction unit 402 and output as digital data (RGB) by an image processing unit 403. Such digital data (RGB) is sent to the image forming unit 300 when the multifunction machine functions as a copier, and to a communication control unit (not shown) when the multifunction machine functions as a facsimile.

  Also, the digital data (RGB) is sent to the ACS unit 118 of the present embodiment to determine whether the document is color or monochrome, and the determination result is output together with the digital data (RGB) for the next processing.

(2) Configuration Example of ACS Unit 118 The ACS determines whether the document image is color or monochrome. Therefore, the saturation for each pixel is obtained, and color determination may be performed depending on how many pixels are above a certain threshold. However, even for a black and white document, for example, there are a large number of color pixels around the edge due to the influence of various processes such as MTF, so it is generally difficult to simply perform ACS determination on a pixel basis. . For this reason, various methods as introduced in the prior art are provided as ACS methods.

  Hereinafter, an inexpensive and stable ACS method that is not affected by the unevenness of conveyance due to document conveyance in the ADF mode according to the present embodiment will be described.

  FIG. 2B is a block diagram illustrating a detailed configuration example of the ACS unit 118.

  The ACS unit 118 is controlled by the scanner control unit 400 as shown in FIG. 2A.

  As described above, since even a black and white image has a large number of color pixels when viewed microscopically, determination is made by counting the continuity of the color pixels.

  In FIG. 2B, reference numeral 1403 denotes a color determination unit. The color determination unit 1403 uses the ACS region signal 1405 generated by the region detection circuit 1402 according to the registers 1407 to 1410 storing four addresses that determine the ACS region for color determination as an enable signal. Note that the ACS area is a target area where color determination (ACS) of the document is performed. Then, by referring to the peripheral pixel held in the filter 1401 for the target pixel in the ACS area, it is determined whether the target pixel is a color pixel or a monochrome pixel, and a color determination signal 1406 is output. To do.

  Specifically, for the ACS region indicated by the ACS region signal 1405, first, the minimum value of DATA-R, DATA-G, and DATA-B is subtracted from the values of the other two components, and the two values obtained are obtained. Get the absolute value of the difference as "saturation". Here, DATA-R, DATA-G, and DATA-B are data of the red component, green component, and blue component of the pixel of interest, respectively. Then, only when a specific continuity of a pixel having a saturation greater than a certain threshold value can be confirmed for the target pixel, the color determination signal 1406 is output indicating that the target pixel indicates a color pixel. In this operation, determination processing is performed for each line in order to minimize ACS image processing.

  Reference numeral 1404 denotes a counter that counts the color determination signal 1406 output from the color determination unit 1403. Then, the count result is sent to the scanner control unit 400 as an ACS determination signal 1411.

  The setting signal 1403a of the color determination unit 1403 includes two signals. One is a signal that sets the threshold for the number of continuous color pixels in the case of “horizontal thin line determination” and the threshold for the number of continuous color pixels in the case of “vertical thin line determination”, which are described in detail below, in the color determination unit 1403 (See 440b and 440e in FIG. 2C). The other is a pixel determination area value for determining whether each pixel is color or black and white (see 440a in FIG. 2C).

  In the present embodiment, the final color / monochrome determination of the document is configured such that the software of the scanner control unit 400 determines each line and the document based on the ACS determination signal 1411 of each line. Show. However, these may be configured by hardware, and the ACS unit 118 may be realized by software. It may be selected based on processing speed, cost, miniaturization, flexibility of change, and the like.

  FIG. 2C is a diagram illustrating a configuration example regarding the ACS of the RAM 430 and the external storage unit 440 of the scanner control unit 400 of FIG. 2A.

  In FIG. 2C, the following storage areas are secured in the RAM 430. Reference numeral 430a denotes a mode flag indicating whether the image reading apparatus reads an original in the ADF mode or an original in the book reading mode. Such a flag is set based on a sense of document placement on the ADF, a document check on the platen, or in accordance with operator settings.

  Reference numeral 430b denotes a horizontal thin line determination flag indicating that the horizontal thin line determination is currently being performed, and a determination result of whether the document is color or monochrome based on the horizontal thin line determination. Reference numeral 430c denotes a vertical thin line determination flag indicating that vertical thin line determination is currently being performed, and a determination result of whether the document is color or black and white by vertical thin line determination.

  Reference numeral 430d denotes an area for storing the count number of the color pixel group in one line in the main scanning direction transmitted from the counter 1404 of the ACS unit 118 as the ACS determination signal 1411. Reference numeral 430e denotes an area for storing the count number in the sub-scanning direction of the determined line of the color line.

  430f is color determination area information for generating the ACS area signal 1405 of the area detection circuit 1402 of the ACS unit 118, and is data set in the registers 1407 to 1410.

  Reference numerals 430g and 430h denote storage areas for storing various sensor information and outputting image reading control signals for controlling the image reading operation of the image reading apparatus.

  Further, reference numeral 430i denotes a program load area in which a computer program executed by the CPU 410 is loaded from the external storage unit 440.

  In FIG. 3C, the external storage unit 440 stores the following programs and parameters.

  Reference numeral 440a denotes a pixel determination threshold value for determining whether each pixel is color or monochrome, and is set in the color determination unit 1403 in FIG.

  Reference numerals 440b to 440d are horizontal thin line determination parameters for determining a horizontal thin line of a color. Among them, 440b is a threshold value for the number of color pixels continuous in the main scanning direction for determining a color area in the main scanning direction. Reference numeral 440c denotes a threshold value for the number of color regions in the main scanning direction for determining whether one line in the main scanning direction is color. Reference numeral 440d denotes a threshold value for the number of lines determined to be a color in the sub-scanning direction for determining whether the document is color or monochrome. A specific example of such a threshold is shown below.

Reference numerals 440e to 440g are vertical thin line determination parameters for determining color vertical thin lines. Among them, 440e is a threshold value for the number of color pixels continuous in the main scanning direction for determining a color area in the main scanning direction. Reference numeral 440f denotes a threshold value of the number of color regions in the main scanning direction for determining whether one line in the main scanning direction is color. Reference numeral 440g denotes a threshold value for the number of continuous lines determined to be a color in the sub-scanning direction for determining whether the document is color or black and white. A specific example of such a threshold is shown below.

  Similar to 430f, 440h is color determination area information for generating the ACS area signal 1405 of the area detection circuit 1402 of the ACS unit 118, and is data set in the registers 1407 to 1410.

  The following program is prepared as a program closely related to this example. Reference numeral 440i denotes an image reading control program for controlling the entire image reading apparatus. Reference numeral 440j denotes an image processing control program for controlling the image processing unit 403 in FIG. 2A. 440k is an ADF control program for controlling the ADF via the ADF control unit 405 in FIG. 2A. 440m is an ACS processing program for executing the ACS processing that is a feature of the present embodiment.

<Operation Example of Image Reading Apparatus of this Embodiment>
FIG. 3A is a flowchart showing an outline of the entire processing procedure of the image reading apparatus of the present embodiment.

  First, in step S31, it is determined whether or not the start key has been pressed. If the start key is not pressed, it waits. When the start key is pressed, it is determined in step S32 whether or not the document is conveyed by ADF. If the document is transported by ADF, the process proceeds to step S 33, and the vertical thin line determination condition is set for the ACS unit 118. For example, in this example, a threshold value for the number of color pixels continuous in the main scanning direction is set in the color determination unit 1403. If the document is not transported by ADF, the process proceeds to step S 34, and a condition for determining a horizontal thin line or a vertical thin line is set for the ACS unit 118. That is, the determination criterion in ACS can be switched according to whether the document is scanned or fixed. Such a selection may be made by an operator. Similar to step S <b> 33, in this example, the color determination unit 1403 is set with a threshold value for the number of color pixels continuous in the main scanning direction. In step S35, the document is read according to whether the document is conveyed by ADF.

  Next, in step S36, color / monochrome determination processing using the ACS unit 118 of the present embodiment is performed. Details of step S36 will be described below with reference to FIG. 3B.

  When the color / monochrome determination process in step S36 is completed, the process branches in step S37 depending on whether the document is color or black and white. If color, the process proceeds to step S38. If the copy function is selected, color recording is performed on the image. The forming unit 300 is instructed. On the other hand, if it is monochrome, the process proceeds to step S39, and if the copy function is selected, monochrome recording is instructed to the image forming means 300.

(Example of color / monochrome determination processing)
First, with reference to FIG.4 and FIG.5, the specifics of the determination conditions by a horizontal thin line and the determination conditions by a vertical thin line in this embodiment are demonstrated.

  FIG. 4 shows an example in which a color original is determined by horizontal fine line determination by ACS, and FIG. 5 shows an example in which a color original is determined by vertical thin line determination by ACS. The broken line arrows in FIGS. 4 and 5 indicate the main scanning direction, the solid line arrows indicate the sub-scanning direction, and black and color described for each square indicate pixels. Black may be white.

In the example of FIG. 4, the continuity of color pixels in the main scanning direction is defined in order to detect a horizontal thin line, and in this embodiment, five pixels are used for easy understanding in the drawing.
First stage of ACS: First, n1 continuous clusters of color pixels are detected in the main scanning direction.
Second stage of ACS: n2 lines having n1 chunks are counted in the sub-scanning direction. However, there is no need for continuity in the sub-scanning direction.

  If n2 is a certain number or more, color determination is made. Of course, if it is less than a certain number, it is determined as black and white. By doing so, it becomes possible to detect a horizontal thin line.

On the other hand, in FIG. 5, in order to detect vertical thin lines, the continuity of color pixels in the main scanning direction is defined, and the continuity of color lines in the sub-scanning direction is defined. In this embodiment, the continuous in the main scanning direction is set to 5 pixels for easy understanding in the drawing.
First stage of ACS: First, m1 color pixel clusters are detected in the main scanning direction.
Second stage of ACS: It is counted that m2 lines continue in the sub-scanning direction.

  If the number of lines m2 is equal to or greater than a certain number, color determination is made. Of course, if it is less than a certain number, it is determined as black and white. By doing so, it becomes possible to detect vertical thin lines.

  A specific example in which such a condition is determined for 10-point Mincho characters, alphabets, and kana characters is shown below.

The horizontal and vertical lines of the character at 10 points are roughly the following dimensions.
Horizontal line length: 3.0mm main scan (70 pixels at 600 dpi)
Horizontal line thickness (height): Sub-scan 0.15 mm (4 lines at 600 dpi)
Vertical line width: Main scan 0.3 mm (7 pixels at 600 dpi)
Vertical line length: Sub-scanning 3.0mm (70 lines at 600 dpi)
For this reason, the setting of conditions for horizontal thin line determination and vertical thin line determination by the ACS is performed as follows.

(Horizontal thin line judgment by ACS: 1st color / monochrome judgment)
(1) Detect a block of 50 pixels continuous in the main scan.
(2) Detect that there are two or more clusters satisfying the condition of (1) in the same main scanning direction.
(3) It is detected that there are 30 or more lines (which can be discontinuous) over the entire sub-scanning direction that satisfy the condition (2).

(Vertical fine line judgment by ACS: 2nd color / monochrome judgment)
(1) Detect a cluster of 5 pixels in the main scanning direction (first threshold or more).
(2) It is detected that there are two or more clusters satisfying the condition of (1) in the same main scanning direction (second threshold or more).
(3) A case where 60 lines or more satisfying the condition of (2) continue in the sub-scanning direction is detected (third threshold or more).

  By setting such conditions, the above-described color / monochrome determination with 10-point characters can be performed in both horizontal thin line determination and vertical thin line determination by ACS.

  However, when the document S is transported by the ADF 100 as a composite apparatus, the leading edge of the document S moves toward the transport rollers 6 and 7 and the discharge roller 8 after the document S passes the reading position R1. At that time, slight conveyance unevenness occurs on the reading position R1. If there is a boundary between black information and white information during document reading in a situation where the conveyance unevenness occurs, an erroneous determination may occur. When FIG. 6 shows image information of a document, as shown in FIG. 7, in the ADF read image information, color pixels are generated immediately before and immediately after black information.

  At this time, the determination of the horizontal line by the ACS is erroneously determined, and there is a risk that even a black and white document is subjected to color determination. In addition, the occurrence of color pixels at the boundary due to uneven conveyance is usually about 1 to 4 lines (0.15 mm when converted to 600 dpi).

  Therefore, there is a risk of erroneous determination in the above-described ACS horizontal line determination during document scanning, and in this embodiment, vertical line determination by ACS is performed during document scanning.

  In this way, even if conveyance irregularity occurs in the ADF, it is possible to perform normal color determination by performing vertical line determination by ACS that counts continuous lines in the sub-scanning direction. Therefore, the ADF can be made inexpensively, the apparatus can be downsized, the inexpensive CCD can be selected, and the image memory can be reduced, so that the apparatus cost can be suppressed.

(Detailed procedure example of color / monochrome determination processing)
FIG. 3B is a detailed procedure example of color / monochrome determination processing using the ACS unit 118 in step S36 of FIG. 3A.

  First, in step S361, the process branches depending on whether the color determination is based on the horizontal thin line or the color determination based on the vertical thin line. In FIG. 3A, in the case of document conveyance by ADF, color determination by vertical thin lines is selected in step S33.

  In step S362, the sub-scanning direction color area count 430e is initialized to zero. In step S363, it is determined whether the output of the counter 1404 (in this case, the number of blocks of 5 pixels or more in the main scanning direction), which is the processing result in the one-line ACS unit 118, is 2 or more. If it is 2 or more, the process proceeds to step S364, and the sub-scanning direction color area count 430e is incremented by one. On the other hand, if a line less than 2 is generated, the process proceeds to step S365, where the sub-scanning direction color area count 430e is reset to zero.

  In step S366, it is determined whether or not the count value of the sub-scanning direction color area count 430e is 60 or more. If it is 60 or more, the process advances to step S369 to determine that the document is a color image. On the other hand, if it is less than 60, the process advances to step S367 to determine whether or not the determination region in the sub-scanning direction has been lost, and if not yet, the process returns to step S363 to perform color determination for the next line. If there is no determination area in the sub-scanning direction, the process advances to step S368 to determine that the document is a monochrome image.

  If the determination in step S361 is horizontal thin line determination, the process branches to step S370.

  In step S370, the sub-scanning direction color area count 430e is initialized to zero. In step S371, it is determined whether the output of the counter 1404 (in this case, the number of blocks of 50 pixels or more in the main scanning direction), which is the processing result in the one-line ACS unit 118, is 2 or more. If it is two or more, the process proceeds to step S372, and the sub-scanning direction color area count 430e is incremented by one. On the other hand, if it is less than 2, the process proceeds to step S373.

  In step S373, it is determined whether the count value of the sub-scanning direction color area count 430e is 30 or more. If it is 30 or more, the process advances to step S376 to determine that the document is a color image. On the other hand, if it is less than 30, the process proceeds to step S374 to determine whether or not all the determination areas in the sub-scanning direction have been determined. If not yet, the process returns to step S371 to determine the color of the next line. If all the determination areas in the sub-scanning direction are determined, the process proceeds to step S375, where it is determined that the document is a monochrome image.

  In the present embodiment, the ACS is described based on the RGB color elements. However, the color elements may be YMC or Lab, and do not affect the gist of the present invention.

  In the present embodiment, an example in which image formation is performed based on a color mode obtained as an ACS result has been described. However, as described at the beginning of the embodiment, the present invention is not limited to this example. For example, it is of course possible to output (image transmission) both the image data read by the reader unit 200 and the color mode information to another apparatus via the external interface.

  In addition, the present invention may be applied to a system or an integrated device composed of a plurality of devices (for example, a host computer, an interface device, a printer, etc.) or an apparatus composed of a single device.

  Another object of the present invention is to supply a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus. Needless to say, this can also be achieved by the computer (or u CPU or MPU) of the system or apparatus reading and executing the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  The functions of the above-described embodiments are not only realized by executing the program code read by the computer. This includes the case where the operating system (OS) running on the computer performs part or all of the actual processing based on the instruction of the program code, and the functions of the above-described embodiments are realized by the processing. Needless to say.

  Further, the program code read from the storage medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU provided in the function expansion card or function expansion unit performs part or all of the actual processing. It goes without saying that the case where the functions of the above-described embodiments are realized by such processing is also included.

  When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above.

1 is a cross-sectional view of a main part of an image reading apparatus included in a color multifunction peripheral according to an embodiment. It is a block diagram which shows the structural example of the control part of the image reading apparatus of this embodiment. It is a block diagram which shows the detailed structural example of the ACS part of this embodiment. It is a figure which shows the structural example of RAM of the scanner control part of FIG. 2A, and an external memory | storage part. 5 is a flowchart illustrating an example of a processing procedure of the image reading apparatus according to the present embodiment. It is a flowchart which shows the example of a detailed process sequence of the color / monochrome determination process by the ACS part of step S36 of FIG. 3A. It is a figure which shows the image data example of the horizontal thin line determination of this embodiment. It is a figure which shows the image data example of the vertical thin line determination of this embodiment. It is a figure which shows the example of the normal image information of the boundary part in image information. It is a figure which shows the example of the read image information at the time of the conveyance unevenness of the boundary part by image information.

Explanation of symbols

100 ADF
S Document Bundle 1 Pickup Roller 3, 5 Transport Roller 6, 7 Transport Roller 8 Discharge Roller 12 DES
20 Document tray 21 Document discharge tray R1 Reading position 200 Reader unit 201 ADF platen glass 202 Book platen glass 203 Lamp 204, 205 Mirror 207 Lens 208 CCD
209 Scanner unit 300 Image forming means

Claims (6)

An image reading apparatus having a reading mode for reading an image of a document while the document is being conveyed from a supply side to a discharge side, and a reading mode for reading an image of a document stationary on a platen on which the document is placed ,
Color / monochrome determination means in the main scanning direction for determining whether a color document or a black and white document is focused on the number of pixels with saturation appearing continuously in the main scanning direction perpendicular to the document transport direction;
Color / monochrome determination means in the sub-scanning direction for judging whether a color document or a black-and-white document is focused on the number of pixels with saturation appearing continuously in the sub-scanning direction parallel to the document transport direction ;
In the reading mode in which the image of the document is read during conveyance, the document is a color document or a monochrome document based on the determination result of the color / monochrome determination unit in the sub-scanning direction, not the color / monochrome determination unit in the main scanning direction. or it is determined,
In the reading mode for reading the image of the stationary document, whether the document is a color document or a monochrome document based on the determination result of the color / monochrome determination unit in the sub-scanning direction or the color / monochrome determination unit in the main scanning direction. Determine
The color / monochrome determination means in the sub-scanning direction is
A reading line having a pixel group continuously having a number equal to or greater than the first threshold in the main scanning direction in the main scanning direction is detected as a reading line having a saturation. First reading line detection means;
A document having continuously the number of reading lines having the saturation detected by the first reading line detecting means equal to or greater than a third threshold in the sub-scanning direction is determined as a color document, and the first reading line detecting means First color / monochrome determination means for determining, as a black and white document, a document having the number of read lines having the saturation detected in step S3 in the sub-scanning direction continuously less than the third threshold value;
Have
The color / monochrome determination means in the main scanning direction is
A reading line having a pixel group continuously having a number of pixels having saturation equal to or greater than the fourth threshold in the main scanning direction is detected as a reading line having saturation. Second reading line detection means;
An original having the number of reading lines having the saturation detected by the second reading line detecting means as a color original in the sub-scanning direction is determined as a color original, and is detected by the second reading line detecting means. Second color / monochrome determination means for determining a document having a number less than a sixth threshold in the sub-scanning direction as a monochrome document for the reading line having the saturation.
Have
An image reading apparatus.   In the pixel having saturation, the absolute value of the difference between the obtained values is smaller than the seventh threshold value by subtracting the minimum value of the three component pixel values of R, G, and B from the values of the other components. The image reading apparatus according to claim 1, wherein the image reading device is a larger pixel. And an image reading apparatus according to claim 1 or 2, the document is an image forming apparatus and controls the image forming in accordance with a color or monochrome document or the determination result. And an image reading apparatus according to claim 1 or 2, the document image transmission apparatus and controls the image transmission in accordance with a color or monochrome document or the determination result. Document reading in an image reading apparatus having a reading mode for reading an image of a document while the document is being conveyed from the supply side to the discharge side, and a reading mode for reading an image of a document stationary on a platen on which the document is placed . A color / monochrome determination method,
The main scanning direction in which the color / monochrome determination means in the main scanning direction determines whether a color document or a black and white document is focused on the number of pixels with saturation appearing continuously in the main scanning direction perpendicular to the document transport direction. Color / black and white judgment process,
The sub-scanning direction determines whether the color / monochrome document in the sub-scanning direction is a color document or a black-and-white document by paying attention to the number of pixels with saturation appearing continuously in the sub-scanning direction parallel to the document transport direction. And a color / black-and-white determination process .
In a reading mode for reading an image of a document during conveyance, the document is a color document or a monochrome document based on the determination result of the color / monochrome determination process in the sub-scanning direction, not the color / monochrome determination process in the main scanning direction. or it is determined,
In the reading mode for reading the image of the stationary document, whether the document is a color document or a monochrome document based on the determination result in the color / monochrome determination process in the sub-scanning direction or the color / monochrome determination process in the main scanning direction. Determine
The color / monochrome determination process in the sub-scanning direction is
The first reading line detection means includes a reading line having a pixel group continuously having a number of pixels having saturation in the main scanning direction by a number equal to or greater than the first threshold in the main scanning direction. A first reading line detection step of detecting as a reading line having a degree;
The first color / monochrome determination unit determines that a document having a number of reading lines having the saturation detected in the first reading line detection step in a number equal to or greater than a third threshold in the sub-scanning direction is a color document. The first color / determining the original having only the number of the read lines having the saturation detected in the first read line detecting step in the sub-scanning direction as the black and white original in the sub-scanning direction. Black and white judgment process
Have
The color / monochrome determination process in the main scanning direction includes
The second reading line detecting means has a saturation of a reading line having a pixel group continuously having a number of pixels having saturation in the main scanning direction by a number equal to or greater than the fourth threshold in the main scanning direction. A second reading line detecting step of detecting as a reading line having:
A second color / monochrome determining unit determines that a document having the number of reading lines having the saturation detected in the second reading line detecting step in the sub-scanning direction is equal to or more than a sixth threshold is a color document; A second color / black-and-white determination step for determining, as a black-and-white document, a document having a saturation line detected by the second scanning line detection means and having a number less than a sixth threshold in the sub-scanning direction;
Have
A color / monochrome determination method for a document in an image reading apparatus. A computer program for causing a computer to execute the steps of the color / monochrome determination method for an original according to claim 5 .

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