JP2006295404A - Image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus capable of accurately detecting the size of an original even if stripe dirt is caused on an original retainer and an original platen glass plate. <P>SOLUTION: A region discrimination section 513 of an image processing circuit 208 reads an image of a carrying belt after a composite machine 1 completes the reading of the entire original 40 to detect a region including the stripe dirt on the carrying belt 108 extended in the subscanning direction. A region storage section 514 stores positions and the range of the region detected by the region discrimination section 513. An original size detection section 515 references a region excluding the detected region stored in the region storage section 514 to detect the size of the original and inputs it to an image forming section 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, and more particularly to a technique for preventing erroneous detection of a document size.

  In recent years, copying machines have been designed for the convenience of users by automatically detecting the size of a document. In order for the copying machine to detect the size of the document, it is necessary to detect a boundary between the portion other than the document and the document (hereinafter referred to as “document edge”), such as a document press that presses the document against the reading glass. In this case, if the document presser is dirty, the document size cannot be detected correctly.

On the other hand, for example, a technique is proposed in which a document edge is detected by scanning a document surface with a light emitting diode beam having a beam diameter larger than the dirt pitch of the document presser and detecting a sudden change in the amount of reflected light. (See Patent Document 1). In this way, it is possible to suppress changes in the amount of reflected light caused by dirt on the document presser, thereby reducing erroneous detection of document edges.
JP 9-163083 A

However, in a copying machine equipped with an automatic document feeder (ADF), streak stains are generated in the sub-scanning direction by rubbing the document against the document presser or the document table glass. If such contamination is present, erroneous detection of the document edge is unavoidable even by the above prior art.
The present invention has been made in view of the above-described problems, and provides an image processing apparatus capable of accurately detecting a document size even when streak stains occur on a document presser or a document table glass. The purpose is to do.

  In order to achieve the above object, an image processing apparatus according to the present invention includes a document table glass on which a document is placed, reading means for reading an image, and a streak from an image read without placing the document on the document table glass. Detecting means for detecting a streak image that is a shape image, and specifying means for specifying a document size by detecting a document edge from an image read in a state where the document is placed on a platen glass. Is characterized in that the document edge is specified from an image other than the streak image detected by the detecting means.

In this way, the document size can be accurately detected even when streaky stains occur on the document presser and the document table glass. In particular, erroneous detection of the document size that occurs when streaks of dirt adhere to the platen glass or the transport belt of the automatic document transport device when the document is transported in the sub-scanning direction by the automatic document transport device. It can be effectively prevented.
The image processing apparatus according to the present invention is characterized in that the reading means reads an image with a CCD line sensor whose longitudinal direction is the main scanning direction. In this way, since the CCD line sensor is also used for detecting the document size, a dedicated sensor is not required. Therefore, the cost of the image processing apparatus can be reduced.

The image processing apparatus according to the present invention is characterized in that the specifying unit specifies a document edge from an image other than the region including the streak image detected by the detecting unit. In this way, not only the streak image but also the peripheral portion of the streak image is excluded, so that erroneous detection can be prevented regardless of the positional deviation that occurs during reading.
The image processing apparatus according to the present invention includes a receiving unit that receives a reading request for requesting reading of an image, and each time the reading unit completes reading related to one reading request, the detecting unit detects a streak image. Features. In this way, when a reading request relating to a plurality of documents is received, a streak image is detected after all the documents have been read, so the number of documents that can be read per unit time can be increased. .

Hereinafter, embodiments of an image processing apparatus according to the present invention will be described with reference to the drawings, taking as an example a multifunction peripheral (MFP: Multiple Functional Peripheral).
[1] Configuration of MFP A configuration of the MFP according to the present embodiment will be described.

(1) Overall Configuration FIG. 1 is a cross-sectional view showing a schematic configuration of a multifunction machine according to an embodiment of the present invention. As shown in FIG. 1, the multifunction machine 1 includes an automatic document feeder 10, a reading unit 20, and an image forming unit 30. The automatic document conveyance unit 10 includes conveyance rollers 101 to 105, a driving roller 106, a driven roller 107, and a conveyance belt 108, and a document 40 to be read is set. The reading unit 20 includes a platen glass 201, a light source 202, mirrors 203 to 205, a lens 206, a CCD (Charge Coupled Device) line sensor 207, an image processing circuit 208, optical benches 209 and 210, and a paper discharge tray 211. The image forming unit 30 forms an image based on the image data read by the reading unit 20.

  The multifunction machine 1 guides the document 40 onto the document table glass 201 by the conveyance rollers 101 to 104 and the conveyance belt 108. The conveyor belt 108 is driven by a driving roller 106 and a driven roller 107. The document 40 placed on the document table glass 201 reflects light from the light source 202. The reflected light from the original 40 passes through the mirrors 203 to 205 and is imaged on the CCD line sensor 207 by the lens 206. The image signal obtained by the photoelectric conversion by the CCD line sensor 207 is processed by the image processing circuit 208.

  The light source 202 and the mirror 203 are fixed to the optical bench 209, and the mirrors 204 and 205 are fixed to the optical bench 210. The multifunction device 1 moves the optical benches 209 and 210 along the platen glass 201 using a stepping motor (not shown) while reading the document 40. In this way, the multifunction device 1 reads the image data line by line by the CCD line sensor 207. When the multifunction device 1 finishes reading the document 40, the multifunction device 1 discharges the document 40 to the sheet discharge tray 211 by the conveyance belt 108 and the conveyance roller 105.

When all the documents 40 are read, the multi-function device 1 reads the conveyance belt 108 and detects a stripe image that is a stripe image, whereby a region including stripe-like dirt extending in the sub-scanning direction on the conveyance belt 108 is detected. Detect and memorize. Thereafter, when the document size is detected, the area including the streaks is excluded.
(2) Configuration of Image Processing Circuit 208 Next, the configuration of the image processing circuit 208 will be described.

  FIG. 2 is a block diagram showing the main functional configuration of the image processing circuit 208. As shown in FIG. 2, the image processing circuit 208 includes an image synthesis unit 501, an A / D conversion unit 502, a shading correction unit 503, an interline correction unit 504, a chromatic aberration correction unit 505, a magnification / movement processing unit 506, a color A conversion unit 507, a manual background adjustment unit 508, an electronic sort memory 509, an auto background adjustment unit 510, a color correction unit 511, an MTF correction unit 512, an area determination unit 513, an area storage unit 514, and a document size detection unit 515 are provided. Yes. The image processing unit 208 receives an image signal from the CCD line sensor 207, performs image processing, and then outputs image data to the image forming unit 30.

  Now, the image composition unit 501 provided in the image processing circuit 208 composes an image for each color output from the CCD line sensor 207 to generate an analog image signal. The A / D conversion unit 502 converts the analog image signal generated by the image composition unit 501 into a digital image signal. A shading correction unit 503 performs shading correction on the digital image signal. The interline correction unit 504 performs interline correction on the digital image signal. A chromatic aberration correction unit 505 corrects chromatic aberration of the digital image signal. The output of the chromatic aberration correction unit 505 is input to the magnification / movement processing unit 506 and the document size detection unit 515.

  A scaling / moving processing unit 506 executes scaling processing (paper designation scaling, independent scaling) and movement processing (binding margin, centering, cornering, vertical parallel movement) according to a user request. The color conversion unit 507 executes color conversion processing for converting the digital image signal from the RGB color system to the Lab color system. The manual background adjustment unit 508 executes background adjustment processing in response to a user request. An electronic sort memory 509 is a memory used when executing a sort process in response to a user request.

  The automatic background adjustment unit 510 performs background adjustment processing regardless of a user request. The output of the automatic background adjustment unit 510 is input to the color correction unit 511 and the area determination unit 513. The color correction unit 511 expresses the digital image signal from the Lab color system to CMYK in order to express all the colors read by the CCD line sensor 207 with a minimum color difference in the color space that can be expressed by the image forming unit 30. Convert to color system. An MTF (Modulation Transfer Function) correction unit 512 executes an MTF correction process for reproducing characters and line drawings sharply faithfully to the original.

  The area determination unit 513 generates and outputs a control signal for controlling the MTF correction unit when the multifunction device 1 reads the document 40. The area determination unit 513 detects an area including streak-like dirt extending in the sub-scanning direction on the conveyor belt 108 when the multifunction device 1 has read the entire document 40 and then reads the conveyor belt 108. The area storage unit 514 stores the position and range of the area detected by the area determination unit 513. The document size detection unit 515 detects the document size with reference to the area excluding the area stored in the area storage unit 514, and inputs this to the image forming unit 30.

(3) Configuration of Region Discriminating Unit 513 Next, the configuration of the region discriminating unit 513 will be described.
FIG. 3 is a block diagram illustrating a main functional configuration of the area determination unit 513. As shown in FIG. 3, the area determination unit 513 includes a color signal generation unit 601, various edge signal generation units 602, an image noise area signal generation unit 603, a halftone area signal generation unit 604, and a color signal generation unit 605. Yes.

  The color signal generation unit 601 generates a black area signal (_BLACK) from the output digital image signal and outputs it. Upon receiving the L signal, the various edge signal generation unit 602 receives halftone dot isolated point signals (WAMI (white isolated point), KAMI (black isolated point)), character edge signal (_INEDG), and character edge region signal (_EDG). ) Is generated and output. The image noise region signal creation unit 603 receives the character edge region signal (_EDG) output from the various edge signal creation units 602, generates a noise region signal (_NOISE), and outputs it to the region storage unit 514.

  The halftone dot region signal generator 604 receives a halftone dot isolated point signal (WAMI, KAMI) from the various edge signal generators 602, generates a halftone dot region signal (_AMI), and outputs it. The MTF control signal generator 605 receives the black area signal (_BLACK) from the color signal generator 601, the character edge signal (_INEDG) and the character edge area signal (_EDG) from the various edge signal generators 602, and the dot area A halftone dot region signal (_AMI) is received from the signal creation unit 604, MTF correction unit control signals (CMPX, KMPX) are generated, and output to the MTF correction unit 512.

(4) Configuration of Various Edge Signal Creation Unit 602 Next, the configuration of various edge signal creation unit 602 will be described.
FIG. 4 is a block diagram showing the main functional configuration of various edge signal creation units 602. As shown in FIG. 4, various edge signal creation units 602 include a matrix creation unit 701, a main scanning primary differential filter 702, a sub-scan primary differential filter 703, a secondary differential filter (+) 704, a secondary differential filter ( X) 705, an inner edge discrimination filter 706, an isolated point detection unit 707, comparators 708 to 711, and a NOR element 712.

Among these, the main scanning primary differential filter 702, the sub-scan primary differential filter 703, the secondary differential filter (+) 704, the secondary differential filter (×) 705, the inner edge discrimination filter 706, and the isolated point detection unit 707 are features. Configure the extraction filter.
The matrix creation unit 701 receives the L signal, generates a 5 × 5 matrix of pixels, and inputs it to the feature extraction filter.

  The main scanning primary differentiation filter 702 performs primary differentiation in the main scanning direction for a 5 × 5 matrix. The sub-scanning primary differentiation filter 703 performs primary differentiation in the sub-scanning direction for the 5 × 5 matrix. A secondary differential filter (+) 704 calculates a secondary differential of a 5 × 5 matrix in the main scanning direction and the sub-scanning direction. A secondary differential filter (×) 705 calculates a secondary differential of a 5 × 5 matrix with respect to a direction oblique to the main scanning direction and the sub-scanning direction. The inner edge discriminating filter 706 determines whether or not there is an inner edge for the 5 × 5 matrix.

  The isolated point detection unit 707 detects isolated points in the 5 × 5 matrix. That is, if the value of the central pixel is larger than the value of the surrounding 8 pixels in the 5 × 5 matrix and larger than the 2-pixel average value in 8 directions, a white isolated point is determined and a WAMI signal is output. If the value of the center pixel is smaller than the value of the surrounding eight pixels and smaller than the average value of two pixels in eight directions, a black isolated point is determined and a KAMI signal is output.

  The comparator 708 compares the output value of the main scanning primary differential filter 702 and the output value of the sub-scanning primary differential filter 702 and outputs the larger value. The comparator 710 compares the output value of the comparator 708 with a predetermined value (EDGREF), and outputs a signal indicating that the logical value is true if the output value of the comparator 708 is larger. Otherwise, a signal indicating false is output.

  The comparator 709 compares the output of the secondary differential filter (+) 704 and the output of the secondary differential filter (×) 705 and outputs the larger value. The comparator 711 compares the output value of the comparator 709 with a predetermined value (EDGREF), and outputs a signal indicating that the logical value is true if the output value of the comparator 709 is larger. Otherwise, a signal indicating false is output. The NOR element 712 calculates the negative logical sum of the outputs of the comparators 701 and 711 and outputs the result.

(5) Configuration of Image Noise Area Signal Creation Unit 603 Next, the configuration of the image noise area signal creation unit 603 will be described.
FIG. 5 is a circuit diagram showing a configuration of the image noise area signal creation unit 603. As shown in FIG. 5, the image noise region signal creation unit 603 includes a plurality of delay elements 801 and NOR elements 802. The image noise region signal creation unit 603 obtains a logical product (AND) for all signals obtained by shifting the character edge region signal (_EDG) by the number of delay elements 801 in synchronization with the main scanning synchronization signal (_TG), and obtains the image noise region signal. (_NOISE) is generated. As a result, the position and range of the area where the character edge area signal (_EDG) continues for a predetermined number of lines in the sub-scanning direction are detected.

[2] Operation of MFP 1 Next, the operation of the MFP 1 will be described.
(1) Main Routine FIG. 6 is a flowchart showing main operations of the multifunction machine 1. As shown in FIG. 6, when the start button on the operation panel is pressed (S601: YES), the multi function device 1 checks whether or not a document is set on the automatic document feeder 10. If the original is set (S602: YES), only one original is conveyed (S603). After the document is transported and when no document is set on the automatic document transport unit 10, the document size is detected (S604). After the original is read (S605), if the original remains in the automatic original conveyance unit 10 (S606: YES), the previous original is discharged, the next original is conveyed (S602), and the above processing is performed. repeat.

If no document remains on the automatic document feeder 10 (S606: NO), dust detection processing is executed (S607). After that, and when the start button is not pressed (S601: NO), it waits for the start button to be pressed.
(2) Document size detection processing (S604)
Next, the document size detection process (S604) will be described. Since the multifunction device 1 detects the size of the document in the sub-scanning direction using a dedicated sensor, a process for exclusively detecting the size of the document in the main scanning direction will be described here.

FIG. 7 is a diagram illustrating an image obtained by reading a document placed on the platen glass 201. As shown in FIG. 7, the document 902 is arranged at one corner of the reading area 901. Further, streak-like stains 903 attached on the conveyance belt 108 or the document table glass 201 together with the document 902 are also read.
The document size in the main scanning direction is determined by detecting the document edge extending in the sub-scanning direction. However, when a figure extending in the sub-scanning direction such as a stain 903 is read, the detection of the document edge is erroneous and the document size is incorrect. There is a risk of detection. On the other hand, in the present embodiment, after the original is read and discharged, the conveying belt 108 and the original platen glass 201 are read to detect the dirt 903, and the area including the dirt 903 is excluded to detect the original size. . In this way, it is possible to prevent the erroneous detection of the document edge due to the contamination of the conveyance belt 108 and the document table glass 201, and hence the erroneous detection of the document size.

  FIG. 8 is a flowchart illustrating the document size detection process (S604). As shown in FIG. 8, the multifunction device 1 first causes the document size detection unit 515 to set the variable s to 0 (S801), and then executes an edge detection loop (S802 to S809). That is, the pixel values arranged in the sub-scanning direction are traced for each pixel of the CCD line sensor 207 having N pixels, and it is determined whether or not the gradation value of the pixel is larger than a predetermined threshold value. If the gradation value is larger than the threshold value (S803: YES), it is determined whether or not the pixel belongs to the region stored in the region storage unit 514. If the pixel does not belong to the region (S804: NO), the value of the variable s is increased by 1 (S805).

  When the pixel belongs to the region (S804: YES) and when the gradation value of the pixel is not larger than the threshold value (S803: NO), the value of the variable s is compared with the constant S. If the value of the variable s is larger than the constant S (S806: YES), the value of the variable s and the value of the variable n are stored (S807), and the value of the variable s is set to 0 (S808). The constant S is a constant that defines the minimum value of the length of the stripe extending in the sub-scanning direction, and the document size detection unit 515 detects a stripe longer than the length defined by the constant S as the document edge.

After finishing the above-described processing for all n from 1 to N, the document size detection unit 515 sets the document size with n corresponding to the largest value of the stored variable s as the position of the document edge in the main scanning direction. Is determined (S810).
(3) Dust detection processing (S607)
Next, the dust detection process (S607) will be described.

  FIG. 9 is a flowchart illustrating the dust detection process (S607). As illustrated in FIG. 9, the area determination unit 513 first sets a variable s to 0 (S901), and then executes a dirt detection loop (S902 to S908). That is, the pixel values arranged in the sub-scanning direction are traced for each pixel of the CCD line sensor 207 having N pixels, and it is determined whether or not the gradation value of the pixel is larger than a predetermined threshold value. If the gradation value is larger than the threshold value (S903: YES), the value of the variable s is increased by 1 (S904).

  When the gradation value of the pixel is not larger than the threshold value (S903: NO), the value of the variable s is compared with the constant S. If the value of the variable s is larger than the constant S (S905: YES), the value of the variable s and the value of the variable n are stored (S906), and the value of the variable s is set to 0 (S907). This constant S is a constant that defines the minimum value of the length of dirt extending in the sub-scanning direction, and the area discriminating unit 513 detects dirt that is longer than the length defined by the constant S and stores it in the area storage unit 514. Remember. When the above process is completed for all n from 1 to N, the dust detection process ends.

[3] Modifications As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) In the above embodiment, the stain detection is performed after reading all the documents set on the automatic document feeder 10. However, the present invention is not limited to this, and every time a document is read. Dirt may be detected.

  When the document is placed on the platen glass 201, the stain may be detected when the start button is not pressed for a predetermined time or more, for example, 10 minutes or more after the start button is pressed. In this way, even when the image is read manually, the next original can be read immediately because the stain is not detected every time the original is read. Therefore, user convenience can be improved.

  (2) Although not particularly mentioned in the above embodiment, if the dirt area detected by the area discriminating unit 513 is included in or coincides with the already detected area, the area storage unit 514 It is also good not to remember. When the newly detected area includes the already detected area, the newly detected area may be stored instead of the already detected area. In this way, the storage capacity used in the area storage unit 514 can be reduced.

  The image processing apparatus according to the present invention is useful as a technique for preventing erroneous detection of the document size.

1 is a cross-sectional view illustrating a schematic configuration of a multifunction peripheral according to an embodiment of the present invention. It is a block diagram which shows the main function structures of the image processing circuit 208 which concerns on embodiment of this invention. It is a block diagram which shows the main function structures of the area | region discrimination | determination part 513 which concerns on embodiment of this invention. It is a block diagram which shows the main function structures of the various edge signal production | generation part 602 which concerns on embodiment of this invention. It is a circuit diagram which shows the structure of the image noise area | region signal preparation part 603 which concerns on embodiment of this invention. 3 is a flowchart showing main operations of the multifunction machine 1 according to the embodiment of the present invention. It is a figure which illustrates the image obtained by reading the manuscript put on manuscript table glass 201 concerning an embodiment of the invention. 6 is a flowchart illustrating document size detection processing (S604) according to an embodiment of the present invention. It is a flowchart which illustrates the dust detection process (S607) which concerns on embodiment of this invention.

Explanation of symbols

1 ……………… MFP 10 ……………… Automatic Document Feeder 20 ……………… Reading Unit 30 ……………… Image Forming Units 40, 902… Documents 101 to 105… Conveying roller 106... Driving roller 107... Followed roller 108... Conveying belt 201. Lens lens 207 CCD line sensor 208 Image processing circuits 209, 210 Optical stage 211 Sheet tray 501 Image composition unit 502 A / D converter 503 ... Shading correction unit 504 ... Interline correction unit 505 ... Chromatic aberration correction unit 506 ... Scaling / movement processing unit 507 ... ..... Color conversion unit 508 ........... Manual background adjustment unit 09 ......... Electronic sort memory 510 ......... Automatic background adjustment unit 511 ......... Color correction unit 512 ......... MTF correction unit 513 ......... Region determination unit 514 ... ... Area storage unit 515... Original size detection unit 601... Color signal generation unit 602... Various edge signal generation units 603. ............... dot area signal generator 605 ......... color signal generator 701 ......... matrix generator 702 .......... main scanning primary differential filter 703 .......... sub scanning Primary differential filter 704 ......... Secondary differential filter (+)
705 ... 2nd order differential filter (x)
706 ..... Inner edge discriminating filter 707 ..... Isolated point detectors 708 to 711 ... Comparator 712 ..... NOR element 801. 901 ... Reading area 903 ... Dirt

Claims (4)

A platen glass on which a document is placed;
Reading means for reading an image;
Detection means for detecting a streak image that is a streak-like image from an image read without placing the document on the platen glass;
A specifying means for specifying a document size by detecting a document edge from an image read with the document placed on a platen glass;
An image processing apparatus characterized in that the specifying means specifies a document edge from an image other than the streak image detected by the detecting means. The image processing apparatus according to claim 1, wherein the reading unit reads an image with a CCD line sensor whose longitudinal direction is the main scanning direction. The image processing apparatus according to claim 1, wherein the specifying unit specifies a document edge from an image other than an area including the stripe image detected by the detecting unit. Comprising a receiving means for receiving a reading request for reading an image;
The image processing apparatus according to claim 1, wherein the detection unit detects a streak image each time the reading unit completes reading related to one reading request.

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