JP4222230B2 - Image reading apparatus, image forming apparatus, image processing apparatus, and program - Google Patents

Description

  The present invention relates to an image reading apparatus that reads an image of a document, such as a printer apparatus, a facsimile apparatus, a copying apparatus, or an image forming apparatus that forms an image on a predetermined output medium, such as a multi-function machine having a plurality of functions thereof. The present invention relates to an image processing apparatus and a program for performing image processing to be used. More specifically, the present invention relates to a technique of so-called background detection processing and background removal processing that prevents a background component of a processing target image from appearing in an output image.

  In an image forming apparatus capable of outputting an image, such as a copying machine or a facsimile, it is called automatic exposure (AE), and measures the density (in the case of a monochrome original) and the background color (in the case of a colored original). A function of performing a process of correcting to an appropriate density and a process of removing a ground color component is used by reflecting the image forming operation.

  For example, according to the measured background information of the input image (ground color component in the case of color), the image data below the predetermined background information in the image data of each color of YMCK is cut (invalidated) or in the vicinity thereof By correcting the gradation and reflecting the measured background detection amount in the image forming operation, the density adjustment processing function to obtain an appropriate density, processing for reducing the background component (background removal processing; background removal processing, This function is also called “ground color removal processing”.

  Specifically, in a copying machine, not only a document using ordinary white paper but also a document with a different color density of the paper itself, such as a newspaper, a half paper, a recycled paper, a colored paper, and the like may be read. is there. Since a document that does not use ordinary white paper has a high background density, when it is read by a light receiving unit such as a CCD sensor and the image data is output as it is, the reproduced document has a background and is dirty. End up.

  Therefore, in order to obtain an optimum output even when such a document is to be read, the density and saturation of the background portion other than characters and figures in the document to be read are detected (background detection). In addition, a device having a background processing function for performing gradation correction processing and saturation compression processing (collectively referred to as background removal processing) according to the detection result is proposed so that background information in the output image is reduced. (For example, see Patent Documents 1 to 5).

Japanese Patent Laid-Open No. 4-037258 JP 7-13399 A JP-A-8-65530 JP 2000-261676 A JP 7-322069 A

  Here, the technique for realizing the background detection process and the background removal process based on the detection result is to read (pre-scan) an image (formation image) of a document prior to a normal image forming operation (main reading; main scanning). By measuring the background density of the image to be processed, based on this measurement result, a pre-scan method for performing background removal processing on the processing target image obtained by the main scan, and performing background detection processing without pre-scanning, It is roughly classified into a real-time method (also referred to as a pre-scanless method) that performs background removal processing based on the detection result.

  For example, in Patent Document 1 that proposes a pre-scan method, a document is pre-scanned, a density histogram on the entire surface of the document is created during the pre-scan, and the background density of the document is determined based on the histogram. Next, the background density determined in advance from the original scanned document information is removed. In other words, the pre-scan method can also be referred to as a surface processing method, in which a target range surface is scanned and a two-dimensional data amount is detected using a histogram.

  However, in the pre-scan method, since a scanning operation for measuring background information is performed before entering a normal image forming operation, the document must be read at least twice, and an output command is issued (for example, start) There is a problem that the processing time FCOT (First Copy Out Time) from when the button is pressed to when the first output (for example, a copy) is discharged increases, resulting in a decrease in productivity. In addition, when detecting the background amount by histogram processing, a detection value may not be obtained depending on a detection parameter.

  Also, as a mechanism using histogram detection, in addition to a mechanism for pre-scanning and pre-storing the entire background data, before performing background removal processing using a memory or the like until the entire background detection result is obtained. There is also a mechanism for waiting for image processing. Therefore, in this case as well as the case of performing the prescan, it is impossible to avoid the problem that the processing time FCOT until the first output product is discharged increases and the productivity decreases.

  As a countermeasure for increasing the processing time, a real-time method that prioritizes detection speed is proposed, and various methods have been proposed (see, for example, Patent Documents 2 to 5). For example, in the methods described in Patent Documents 2 to 4, the background density (background amount) for each line is detected without pre-scanning, and tone correction is performed in real time (in units of lines) according to the detection result. A way to go is proposed.

  However, with the real-time method that performs density adjustment and background removal while detecting the background on the entire document surface, it is actually difficult to reliably detect the background density. For example, depending on the content of the document, such as a gradation image, If the background detection amount fluctuates, and the density adjustment process or background removal process is performed based on the detection results, the density level may change unnecessarily during the process, or the background removal level may fluctuate. This causes the problem of deterioration.

  For this reason, in the real-time method, background detection is performed only at the front edge of the document, and density adjustment and background removal are performed. However, at the center of the document where the main part of information is likely to exist, the background detection is stopped and Based on the background detection amount acquired on the side, a method of performing subsequent density adjustment (at the center of the original) and background removal is usually employed.

  In addition, as a technique for improving the problem in the above-described real-time method, Patent Document 5 discloses that when a background component (background density) is read in units of lines, the line is divided into a plurality of blocks, and the background is divided into the plurality of blocks. A method for detecting fluctuations in the detected value without being affected by fine noise by detecting the maximum value of the component and using the minimum value among the maximum values detected in each block in one line as the background component of the line, In addition to this, the background detection amount of the current line is corrected according to the background detection amount of the line, a change amount restriction range is provided to restrict the change amount of the background detection amount from the previous line, and the change amount restriction range is set to the processing line. A method is also applied such as gradually decreasing in accordance with this, setting the variation limit range to “0” in an arbitrary processing line, and providing an insensitive area on both sides of the document in order to prevent reference outside the document. And, the method to achieve a further improvement has been proposed.

  However, even if such a technique for improving the problem in the real-time method is applied, there may be a problem in detection accuracy due to the relationship between the arrangement position of the document to be read and the reading range. For example, if there is a difference between the leading edge position of the document and the reading start position depending on how the document is placed, background amount data is collected with the back (platen back) area of the document table cover as the document. In such a case, the background information of the document cannot be detected correctly, the background density level and saturation in the output image vary, and the quality of the output image deteriorates.

  Thus, the conventional pre-scan method and the real-time method cannot sufficiently satisfy both the processing time and the processing performance.

  The present invention has been made in view of the above circumstances, and in performing background removal processing and density adjustment processing, the relationship between the reading range and the position of the original to be read affects background removal performance and density adjustment performance. The purpose is to propose a mechanism without any problem. More preferably, an object of the present invention is to provide a mechanism that can achieve the above object without requiring a pre-scan.

  An image processing apparatus according to the present invention is an image processing apparatus that detects background information of a processing target image and performs image processing for forming an output image corresponding to the processing target image based on the detected background information. Then, based on the tip detection unit that detects the tip of the effective image portion in the processing target image represented by the image signal and the image signal after the tip detection unit detects the tip, the background information in the processing target image is detected. A background detection unit and a background removal processing unit that reduces background information of an effective image portion in the output image based on the detection result of the background detection unit are provided.

  An image reading apparatus according to the present invention is an image reading apparatus that reads an image of a document by moving a document to be read relative to a light receiving unit that reads the document in a predetermined movement direction. The function of the image processing apparatus according to the above is provided. That is, in the processing target image read by the light receiving unit, the leading edge detection unit that detects the leading edge of the document in the moving direction (corresponding to the effective image portion) and the light receiving unit after the leading edge detection unit detects the leading edge. A background detection unit that detects background information of the document in the processing target image based on the received image signal, and a background that reduces background information of the document portion that is an effective image portion in the output image based on the detection result of the background detection unit And a removal processing unit.

  An image forming apparatus according to the present invention has the functions of the image processing apparatus according to the present invention, and on a predetermined recording medium based on an output image in which background information is reduced by a background removal processing unit of the image processing apparatus. An image forming unit that forms a visible image is provided.

The image reading apparatus, the image forming apparatus, and the image processing apparatus according to the present invention can be realized by software using an electronic computer (computer), and a program for this purpose and a recording medium storing the program are extracted as the invention. It is also possible. The program may be provided by being stored in a computer-readable storage medium, or may be distributed via wired or wireless communication means.

Here, the leading edge detection unit sequentially acquires the background information of the processing target image in the processing target direction (sub-scanning direction; relative movement direction in the case of the image reading apparatus) with importance on reliability. The tip shall be detected with. Specifically, the underlying information to be processed the image processing sequentially acquires the subject direction shall be the one that detects the leading edge of the acquired base information by histogram analysis.

In addition, the background detection unit may determine the background information of the processing target image with emphasis on the detection speed . Specifically , the background detection unit determines the background information for each line of the processing target image. The background removal processing unit is assumed to reduce background information for each line based on the detection result of the background detection unit .

  In addition, the background detection unit and the background removal processing unit perform not only processing for reducing background information regarding lightness but also processing for reducing background information regarding saturation by paying attention to saturation. Good.

  According to the present invention, first, the leading edge of the effective image portion in the processing target image is detected, and the ground information in the processing target image is detected based on the image signal after the leading edge is detected to perform the ground removal processing. I did it. Thereby, for example, the background processing is performed substantially only on the image signal of the effective image portion in the processing target direction regardless of the arrangement relationship of the effective image portion (for example, the document portion) of the processing target image with respect to the reading range. Can do. By treating the area other than the effective image portion as the dead zone, it is not affected by the image signal other than the effective image portion at the time of the background detection process, so that the high precision background processing can be performed. Since the configuration for detecting the tip of the effective image portion in the processing target image is provided, the dead zone in the processing target direction can be set dynamically and adaptively.

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

<Configuration of image reading apparatus>
FIG. 1 is a side sectional view showing an outline of an embodiment of an image reading apparatus including an image processing apparatus including a background removal processing circuit according to the present invention. An image reading device 3 shown in FIG. 1 is used for, for example, a copying machine, a scanner device, a facsimile device, etc., and optically reads an image drawn on a document to be read from the document. In general, the image acquisition unit 10, the image processing unit 20, and the platen cover 61 are provided.

  The image acquisition unit 10 includes a casing 111 and a platen glass (original placement table) 112 that is made of transparent glass provided on the casing 111 and is slightly larger than the A3 size on which an original to be read is placed. have. The image processing unit 20 is provided on an image processing substrate 102 provided in the housing 111.

  In the case of constituting a copying apparatus, the image signal processed by the image processing unit 20 converts a visible image onto a predetermined recording medium using a known printing method such as a thermal sublimation method, an ink jet method, or an electrophotographic method. The image is sent to an image output unit including a print engine (image forming unit) to be formed.

  The image acquisition unit 10 irradiates reading light toward the surface (back surface) opposite to the document placement surface of the platen glass 112 below the platen glass 112 in the casing 111, that is, the document on the platen glass 112. An exposure light source 120 that irradiates reading light toward the platen, and a substantially concave reflecting shade 131 that reflects the reading light emitted from the exposure light source 120 toward the platen glass 112.

  The image acquisition unit 10 receives reflected light from the platen glass 112 side and performs a main scanning FS (Fast Scan) that is substantially orthogonal to the direction of the sub-scanning SS (Slow Scan) (the reading direction of the arrow X in the figure). A light receiving unit 140 that sequentially reads an image signal (analog electric signal) corresponding to the density, reads the image in the direction (the depth direction in the drawing), and amplifies and outputs the image signal from the light receiving unit 140 to a predetermined level. The contact optical system includes a read signal processing unit 14.

  The light receiving unit 140 includes a photoelectric conversion element such as a photodiode, a CCD (Charge Coupled Device), a CMOS (Complementary Metal-Oxide Semiconductor), and the like, and a line sensor (not shown) having a width substantially equal to the width of the document in the main scanning direction. ) Is used.

  The light receiving unit 140 is disposed on the substrate 103 together with the read signal processing unit 14 and the like, and constitutes an optical scanning system (sensor unit) 16. Instead of the light receiving mechanism using the contact optical system, a reading optical system (scanning optical system) employing a reduction optical system such as the exposure light source 120, the full rate carriage 134, the half rate carriage 138, or the lens 139 is employed. May be.

  As the exposure light source 120, a lamp whose longitudinal direction is the main scanning direction is used. As the color of the illumination light emitted from the exposure light source 120, a color that matches the spectral optical characteristics of each line sensor (not shown) constituting the light receiving unit 140 constituting the main part of the imaging device is used. Or green light is used. The lighting operation of the exposure light source 120 can be controlled by an illumination control unit (not shown).

  Although not shown, the image acquisition unit 10 also includes a wire, a drive pulley, and the like that move the reading optical system and the light receiving unit 140 under the platen glass 112 in the housing 111. The driving pulley is reciprocally rotated by the driving force of the driving motor, and the optical scanning of the exposure light source 120 or the lens 139 is performed below the platen glass 112 by winding the wire around the driving pulley by this rotational driving. The system 16 is moved at a predetermined speed.

  In the above configuration, the optical scanning system 16 of the image acquisition unit 10 is normally at the home position H indicated by a Δ mark in the drawing below the platen glass 112. The home position H is set on the reading area side below the platen glass 112 from the fixed reading image destination position F. For example, with respect to the fixed reading image destination position F, it is set in a reading area that is about 2 to 3 cm inward in the sub-scanning direction.

  Thus, in the fixed reading method, the document placed on the platen glass 112 by the line sensor provided in the light receiving unit 140 without moving the light receiving unit 140 in the sub-scanning direction before starting the reading. The size in the main scanning direction can be detected.

  In this fixed reading method, a document is placed on a platen glass 112 serving as a document placement table, and is fixed (stop-locked) at an arbitrary position on the platen glass 112. Using the fixed reading image destination position F as a reading reference, the optical scanning system 16 is scanned at a constant speed in the direction of the arrow X (sub-scanning direction) to expose a document and read an image.

  The light receiving unit 140 sends captured image signals of each spectral component obtained by capturing a document image with a line sensor to the read signal processing unit 14. The read signal processing unit 14 performs desired analog signal processing on the captured image signal obtained by the reading, and then converts the digital image data of each color component of red (R), green (G), and blue (B). After conversion and shading correction and other predetermined processing, red, green, and blue digital image data are sent to the image processing unit 20. In the image processing unit 20, for example, the color component digital image data R, G, B output from the read signal processing unit 14 is synchronized, or the color conversion processing for generating the lightness signal L and the color signals a, b. Etc.

  In the above description, the image reading apparatus 3 is shown as a single unit. However, the image reading apparatus 3 can be used as a scanner unit to constitute a copying apparatus. In this case, for example, an image output unit is provided below the image acquisition unit 10, and black (K), yellow (Y) based on the red, green, and blue image data R, G, and B from the image processing unit 20. , Magenta (M), cyan (C) binary or multivalued output image signal output image processing unit, and a recording medium such as printing paper based on the output image signal obtained by the output image processing unit An image forming unit (print engine) for forming a visible image may be provided on the top.

<Configuration and operation of image processing unit>
FIG. 2 is a block diagram illustrating an embodiment of the image processing unit 20 provided in the image reading apparatus 3 having the configuration shown in FIG. Here, an example is shown in which a copying apparatus, which is an example of an image forming apparatus, is configured by using the image reading apparatus 3 as a scanner unit.

  The image forming apparatus 5 is configured to display an image represented by the image signal obtained by the image acquisition unit 10 after the image processing unit 20 by using an electrophotographic type, a thermal type, a thermal transfer type, an ink jet type, or the like. An image forming unit (image output unit) 906 that forms (prints) a visible image on plain paper or thermal paper using image forming processing is provided.

  The image forming unit 906 is a raster output scan base for operating the image forming apparatus 5 as a digital printing system based on print output data such as binary signals of yellow Y, magenta M, cyan C, and black K, for example. A print engine 964 is included.

  In the image processing unit 20, an image input unit 200 that acquires image data Vin having a relatively high bit number (for example, 8 to 10 bits) from the image acquisition unit 10 that is the preceding stage, and an image acquired by the image input unit 200. A background detection unit 300 that detects the background level (background level) of the processing target image based on the data Vin, and a background removal processing unit 400 that performs background removal processing based on the detection result of the background detection unit 300 are provided.

  In addition, between the image input unit 200 and the background removal processing unit 400, as indicated by a dotted line in the figure, scaling processing, color conversion processing (RGB data → Lab data → YMCK data, etc.), contrast adjustment (density adjustment) ) A signal processing unit (pre-processing unit) 280 that performs predetermined image processing (pre-processing) such as processing, color correction processing, and filter processing prior to the background removal processing may be provided. The details of the preprocessing itself in the signal processing unit 280 are the same as those in the prior art, and the description thereof is omitted here.

  The output data of the background removal processing unit 400 is sent to, for example, the output data processing unit 600 that converts the data into print engine data. A predetermined image such as contrast adjustment (density adjustment), color correction processing, filter processing, TRC (Tone Reproduction Control) correction (gradation correction) is provided between the background removal processing unit 400 and the output data processing unit 600. A signal processing unit (post-processing unit) 500 that performs processing (post-processing) may be provided. The details of the post-processing itself in the signal processing unit 500 are also the same as those in the prior art, and the description thereof is omitted here.

  The output data processing unit 600 uses the processed color image data Y, M, C, and K subjected to the background removal processing by the background removal processing unit 400 as input data, and an image forming unit 906 including a print engine 964 as a main part. Generates output data of the applicable number of bits. For example, binarized data (one-bit data) or multi-bit data (lower than the number of bits of input image data) obtained by applying screen processing to each is output.

  FIG. 3 is a diagram showing details of the background detection unit 300 and the background removal processing unit 400. In the present embodiment, the background detection unit 300 and the background removal processing unit 400 use the background color information of the document image, which is low speed (it takes time to acquire the background color information), but has high reliability. A leading edge detection unit that detects a leading edge of an effective image component (an image of a document) in a processing target image (for example, an image read by the image acquisition unit 10) by performing a background detection process and a background removal process that can acquire the background information. It has a feature in that it has a first processing system having the above function and a second processing system for performing general background detection and removal processing.

  The first processing system only needs to perform processing focusing on the leading end side of the reading range. For the second processing system, it is preferable to adopt a process (background detection process and background removal process excellent in immediacy) that emphasizes the background detection speed without requiring pre-scanning.

  Specifically, as illustrated in FIG. 3A, the background detection unit 300 performs processing that emphasizes background detection performance and background removal performance instead of processing that focuses on background detection speed in the first processing system. It is characterized in that it is performed. In other words, the ground color information of the original image captured by the image input unit 200 is determined not to give priority to the detection speed but to a low speed (it takes time to acquire the ground color information), but the background information with high reliability is determined. It is characterized in that background detection processing using values is executed.

  With such a configuration, an original placed on a platen glass 112 serving as an original placing table is scanned from a predetermined reading reference position, an image of the original is read, and detection accuracy is emphasized with respect to raster data sequentially scanned and input. Substrate processing is performed by the first processing system that employs the detection method described above. This detection method emphasizing detection accuracy is evaluated for each main scanning (line), and the change in image information outside the original range is less than a certain value, and the change in image information excluding the original range (that is, the original image information) is changed. If it is equal to or greater than a certain value, it is determined that the document is in the document, and after determining that the document is in the document, the background processing is switched to speed-oriented. Also, the detection process is stopped near the center of the document.

  Here, as the background detection method with an emphasis on reliability, various known methods can be used as long as the detection is performed without line variation of the background component (background density). As a typical example, it is preferable to provide a histogram background detection processing unit 310 using a histogram background detection method.

  The background removal processing unit 400 corresponds to the provision of the histogram background detection processing unit 310 in the background detection unit 300, and the highly reliable background detection amount DTH (Data of Top) obtained by the histogram background detection processing unit 310. As a processing system for performing background removal processing with reference to (Histogram), a histogram background removal processing unit 410 that performs background removal processing by determining a background removal amount ThTH corresponding to the background detection amount DTH is provided.

  The histogram background removal processing unit 410 receives the background detection amount DTH acquired by the histogram background detection processing unit 310 each time line information (pixel data for each line) is input until a definite value of the background detection amount DTH is obtained. Are used for the real-time background removal processing in the histogram background removal processing unit 410. When the determined value of the background detection amount DTH is obtained, the subsequent processing is left to the second processing system.

  Note that the background removal processing method in the histogram background removal processing unit 410 is basically the same as, for example, the methods described in Patent Documents 1 to 5, and the background detection detected by the histogram background detection processing unit 310 is performed. A background removal level corresponding to the amount DTH is set, and tone correction according to the background removal level is performed on the lightness signal L. The detailed explanation is omitted here.

  The histogram background detection processing unit 310 and the histogram background removal processing unit 410 obtain the ground color information by histogram analysis for the first half in the sub-scanning direction of the image signal Vin captured by the image input unit 200, thereby increasing the detection speed. The background processing using the fixed value of the background information with high reliability that is not important but is slow (acquisition takes time) is executed. This histogram background processing has better detection reliability than real-time background detection and removal, which is an example of background processing with an emphasis on detection speed.

  Here, the case where real-time detection fails and the accuracy and reliability of histogram detection and real-time detection will be described. Real-time detection is performed when the black image is concentrated on the tip (hereinafter referred to as the former), for example, when there is a punched hole, the corner of the document is broken, or the document is placed at an angle, etc. If the background part (platen cover 61 or the like) enters the detection region (hereinafter referred to as the latter), background detection (background detection) may fail.

  The former is because the detection amount returns to the initial value (low value) when the detection amount exceeds a certain value, and the background removal amount is also reduced. This is to prevent the original without the background from being removed. When the black image is concentrated on the tip, the background detection amount exceeds a certain value.

  In the latter, when the platen glass or the platen cover 61 of the background portion enters the detection area, the color (for example, white) on the back side of the platen cover (back platen) is recognized as the background, and is detected to be whiter than the actual document background. . However, it can be said that the histogram detection is more reliable than the real-time detection because the detection does not fail even in such a document (state).

  Next, from the viewpoint of accuracy, the histogram detection is a method in which errors are likely to enter because the histogram is created by dividing into regions having a certain width. The error depends on the width of the region. For example, when the pixel unit is used, there is no error, but it becomes difficult to set a parameter for determining the background detection amount, and the answer to the background amount cannot be obtained.

  On the other hand, real-time detection may fail in detection, but can be said to be a detection method with fewer errors than the histogram. Failures increase when the background density of the document is high or when the document is placed out of the reading standard. For example, the larger the difference between the color and density of the back platen, the more noticeable the failure.

  That is, when the detection is high, the result of the real-time detection may be selected because the real-time detection is “not failed” and “there is little error”.

  In terms of speed, the real-time method usually has a processing delay of one line, but the histogram requires a certain amount of image area, so the real-time method is superior in terms of speed.

  In general, histogram detection is sometimes referred to as a detection method that emphasizes accuracy, and real-time detection is sometimes referred to as a detection method that emphasizes speed, but in this embodiment, based on the above, histogram detection is a detection method that emphasizes reliability, and real-time detection is Used as a speed-sensitive detection method.

  On the other hand, for the second processing system, the background detection unit 300 detects the background information (background density) of a document by a real-time background detection method in units of lines, which is an example of background detection processing with excellent immediacy. Similarly to the real-time detection unit 320, any one of the adaptive tip real-time detection unit 330 that switches the processing based on the information on the tip region and performs the background detection processing, the tip real-time detection unit 320, and the adaptive tip real-time detection unit 330 And a switching unit 360 for switching between selection and use.

  The control signal CN1 is input from the histogram background detection processing unit 310 to the enable terminals En of the tip real-time detection unit 320 and the adaptive tip real-time detection unit 330. This control signal CN1 is a signal indicating that the line data to be processed has reached the document area.

  Both the leading edge real-time detection unit 320 and the adaptive leading-edge real-time detection unit 330 perform background detection processing up to the center of the document, but the background after the center is based on the detection result when the processing is stopped at the center. Perform processing.

  Real-time background detection focuses only on the front edge of the document, even when high-density images are concentrated on the front edge of the document, ensuring high-density background information (background density) on the front edge of the document. This is to prevent image quality deterioration due to fluctuations in the background removal amount due to fluctuations in the background detection amount at the center of the document where main information is likely to exist.

  As the real-time detection, the front-end real-time detection unit 320 or the adaptive front-end real-time detection unit 330 that stops processing when the front end of the document is detected is used. However, real-time background detection is performed in units of lines over the entire surface. Also good.

  Real-time background detection, which is an example of a speed-oriented background detection method performed by the front-end real-time detection unit 320, is background information (background density) in units of lines based on information about the brightness of an image (specifically, L component in Lab data). As long as it obtains (), various known methods can be used.

  For example, the methods described in JP-A-7-13399 and JP-A-7-322069 can be used. In particular, when reading the background component (background density) in units of lines, the line is divided into a plurality of blocks, and the maximum value of the background component is detected for each of the plurality of blocks and detected in each block in one line. Use of the method described in Japanese Patent Laid-Open No. 7-322069, in which the minimum value among the maximum values is used as the background component of the line, is preferable because fluctuation of the detection value can be prevented without being influenced by fine noise.

  Also, as described in Japanese Patent Laid-Open No. 7-322069, the background detection from the previous line is performed by arbitrarily setting the size of a plurality of blocks, correcting the background detection amount of the current line according to the line background detection amount of the line Documents on both sides of the document are provided with a variable amount limit range to regulate the amount of change, the change amount limit range is gradually reduced according to the processing line, and the variable amount limit range is set to “0” on any processing line. It is more preferable to apply a technique such as providing a dead area in order to prevent external reference.

  The background detection performed by the adaptive tip real-time detection unit 330 basically has the same function as the tip real-time detection unit 320, and also determines the ground color type of the image based on information about the saturation in the image data. It has a function.

  For example, as shown in FIG. 3B, the adaptive tip real-time detection unit 330 includes a tip real-time detection unit (background detection unit) 332 having the same function as the tip real-time detection unit 320, and Based on the saturation components a and b, based on the color determination unit 334 that determines whether the background color of the document image is a color having a clear color, and the saturation components a and b in the Lab data, By including a yellowing determination unit 336 that determines whether or not the background color of the document image corresponds to “yellowing” defined as a predetermined color, the background color type of the document is determined. Here, “color” means coloring. “Yellowness” means a yellow component with low saturation.

  For example, the color determination unit 334 sets a color determination window corresponding to a color with a clear color on the color coordinates formed by the two saturation axes a and b, and the input data a and b determine the color determination. It is determined whether or not the pixel falls within the window. Then, the color determination unit 334 notifies the adaptive real-time background removal processing unit 430 of information DETclr indicating the color determination result.

  More specifically, the color determination unit 334 first divides the scanning start coordinate position to the scanning end coordinate position in the main scanning direction into a plurality of line blocks, and within each line block within the area of the color determination window. The number of existing pixels is counted, and if the result is equal to or greater than a predetermined first threshold, the line block is set as a color block. If the number of color blocks in one line is equal to or greater than a predetermined second threshold, the line is set as a color line.

  Further, when the color lines continue in the sub-scanning direction by a predetermined third threshold or more, the color determination unit 334 sets these line groups as color line blocks. If the color line block is greater than or equal to the predetermined fourth threshold, it is determined that the background color of the document is color. On the other hand, if it is determined that it is not a color, it is determined that the background color of the document is black and white (no color).

  The yellowing determination unit 336 sets a yellowing determination window corresponding to yellowing having a predetermined color on the color coordinates formed by the two saturation axes a and b, and the input data a and b are included in the yellowing determination window. It is determined whether or not the corresponding pixel. Then, the yellowing determination unit 336 notifies the adaptive real-time background removal processing unit 430 of information DETyel indicating the yellowing determination result.

  Specifically, the yellowing determination unit 336 first replaces the color determination window in the color determination unit 334 with a yellowing determination window, and performs the same procedure as the color determination unit 334, so that the background color of the document is “yellowing”. It is determined whether or not it has. Even if the yellowing determination unit 336 determines that “yellowing” has occurred, if the color determination unit 334 determines that the background color of the document is a color, this color determination is performed. The determination of the unit 334 is prioritized. That is, when the ground color is a color, it is not determined that yellowing has occurred.

  By performing color determination and yellowing determination using such blocks, it is possible to avoid erroneous determination due only to the presence of a diagram, and as a result, it is possible to improve accuracy of color determination and yellowing determination Become. In addition, since color determination and yellowing determination can be performed by paying attention only to the leading edge of the document, it is not necessary to perform pre-scan for the entire document, and color determination processing and yellowing determination processing can be speeded up. In addition, these functions can be realized with a relatively simple configuration.

  The background removal processing unit 400 refers to a background detection amount DTR (Data of Top Real time) obtained by the tip real-time detection unit 320 in correspondence with the provision of the tip real-time detection unit 320 in the background detection unit 300. On the other hand, it has a real-time background removal processing unit 420 that determines the background removal amount ThRT corresponding to the background detection amount DTR and performs the background removal processing in real time (every time pixel data is obtained in line units).

  Note that the background removal processing method in the real-time background removal processing unit 420 is basically the same as the method described in Patent Documents 1 to 5, for example, and the background detected by the histogram background detection processing unit 310. A background removal level corresponding to the detection amount DTH is set, and gradation correction is performed on the lightness signal L according to the background removal level. The detailed explanation is omitted here.

  In addition, the background removal processing unit 400 refers to the background detection amount DTRa obtained by the adaptive tip real-time detection unit 330 in correspondence with the provision of the adaptive tip real-time detection unit 330 in the background detection unit 300. The adaptive real-time background removal processing unit 430 performs the background removal processing in real time (each time pixel data is obtained in units of lines) by determining the background removal amount ThRTa corresponding to the background detection amount DTRa.

  The background removal processing method in the real-time background removal processing unit 420 is basically the same as the method described in Patent Documents 1 to 5, for example, and the background detection amount DTR detected by the front-end real-time detection unit 320. A background removal level corresponding to is set, and tone correction is performed on the lightness signal L according to the background removal level. The detailed explanation is omitted here.

  The adaptive real-time background removal processing unit 430 also detects the background detection amount DTR detected by the tip real-time detection unit 332 in the adaptive tip real-time detection unit 330, and the ground color type of the image determined by the color determination unit 334 and the yellowing determination unit 336. Based on the detection results DETclr and DETyel, adaptive background removal processing is performed on the image data. By switching the background removal processing according to the background color of the document, even if the processing target image has a color tone in the background portion, the background removal according to the background color type is adaptively performed.

  For example, the adaptive real-time background removal processing unit 430 does not perform background removal processing on image data if the ground color type of the processing target image has a clear color (colored). For example, if the background color type is “color paper document”, since the background color of the entire document is color, the adaptive real-time background removal processing unit 430 does not depend on the level of the background detection amount DTRa by the tip real-time detection unit 332. The background removal process for removing the background level of the original is not performed. That is, tone correction for the L component is not performed on the Lab data to be processed.

  If the background color type of the processing target image is “yellowish original” having a slight tint such as yellowish, the adaptive real-time background removal processing unit 430 has a predetermined color corresponding to the yellowish color. Saturation correction is performed to remove the taste, and background removal processing (actually tone correction processing) is performed to remove the background level corresponding to the background detection amount DTRa detected by the front-end real-time detection unit 332.

  Since the yellow color region is mapped in the positive direction on the b-axis, in order to suppress the color reproduced as “yellowish”, the positive value region of the b component Correction processing is performed such that the input value is lowered to a value at which yellowing is not reproduced.

  Further, the adaptive real-time background removal processing unit 430 is similar to the real-time background removal processing unit 420 without performing saturation correction if the background color type of the processing target image is a white background document having no color. Then, a background removal process is performed to remove the background level according to the background detection amount DTRa detected by the tip real-time detection unit 332.

  As described above, by performing the background removal process adaptively according to the background color type of the document, even when the background removal process is performed on a document with yellowing, such as old newspaper or recycled paper, for example. The yellowing is not emphasized and can be removed appropriately. Further, for an original such as color paper, the background color can be faithfully reproduced as original information as it is, and the color of the original does not change.

  In addition, the background removal processing unit 400 has processed image data output from each of the histogram background removal processing unit 410, the real-time background removal processing unit 420, and the adaptive real-time background removal processing unit 430 as input data. A switching output unit 480 that selects and outputs one of them is provided.

  In the switching output unit 480, as a switching control signal, a control signal CN1 from the histogram background detection processing unit 310, and a selection control signal for selecting and specifying one of the tip real-time detection unit 320 and the adaptive tip real-time detection unit 330 are selected. CN2 is input. The selection control signal CN2 is based on a central control unit (not shown) or a user instruction.

  The switching output unit 480 outputs the processing result of the histogram background removal processing unit 410 until the leading edge of the document is detected by the histogram background detection processing unit 310, and when the leading edge of the document is detected, the real-time background removal processing unit 420. Then, the processing result of the one instructed by the selection control signal CN2 in the adaptive real-time background removal processing unit 430 is output.

  That is, the background removal processing unit 400 performs the background-side histogram detection and the background removal processing in response to the detection result until the processing target line reaches the leading edge of the document, and detects the real-time leading edge detection for the processing target lines after the document leading edge. And the base removal processing based on the detection result. When the front end of the document is not detected by the histogram background detection processing unit 310, only the front side histogram detection and the background removal processing that receives the detection result are performed.

  Note that the selection control signal CN2 may also be input to the tip real-time detection unit 320 and the adaptive tip real-time detection unit 330, and other processing units that do not correspond may be instructed to stop processing.

  Thereby, the background removal processing unit 400 performs background removal only with the functional block that performs the background removal processing with the background removal amount ThTH corresponding to the background detection amount DTH after the background detection value DTH is determined. The operation of other function blocks not applicable is stopped. In this way, power consumption is reduced by stopping the operation of the useless processing system.

  As described above, in the above configuration, first, the leading edge of the document is detected by performing the background detection processing by the histogram background detection processing unit 310 from the leading edge of the reading range. When the leading edge is detected, each of the leading edge real-time detection units 320 and 330 starts processing, so that the background detection process is performed substantially based only on the image data within the document range.

  Each of the real-time background removal processing units 420 and 430 performs background removal processing at a background removal level corresponding to the background detection amounts DTR and DTRa obtained by the background detection processing of the corresponding front-end real-time detection units 320 and 330.

  The switching output unit 480 outputs the processing result of the histogram background removal processing unit 410 until the leading edge of the document is detected. After the leading edge of the document is detected, one of the processes of the real-time background removal processing units 420 and 430 is performed. Output the result.

<Operation of Histogram Background Detection Processing Unit>
4 and 5 are diagrams for explaining the relationship between the state of the document placed on the platen glass 112 and the reading range.

  For example, FIG. 4 shows an example of how to place a document on the platen glass 112. In the example shown in FIGS. 4A and 4B, the platen cover 61 is used to determine the position where the document should be placed in the fixed position reading mode, that is, the reference reading range and the placement position of the document to be processed. Showing the relationship. In the “fixed position reading mode” of the present embodiment, the position where the lead registration guide LRG and the side registration guide SRG intersect (orthogonally), that is, the left rear corner of the platen glass 112 is set as the document setting reference position.

  The document is scanned over the desired area of the platen glass 112 with one end edge of the document abutting on the end of the lead registration guide and the end edge of the side registration guide abutting the edge perpendicular to the one end edge. It is assumed that an image is read. For example, the reading range at this time is set to be switched according to the document size specified on the operation panel, or the A3 document is set as the maximum size.

  Here, when the document is abutted against the lead registration guide LRG and the side registration guide SRG and aligned with the set reference position, the document is properly arranged as shown in FIG. For example, as shown in FIG. 4 (B), it may be shifted in the main scanning direction or the sub-scanning direction, or as shown in FIG. 5 (A). Sometimes it is done.

  When the document is placed in a shifted state as described above, an image of the background portion appears from the start of reading until it reaches the leading edge of the document as shown in FIG. Even if is an effective reading range, an image of the background portion appears from the set reference until it reaches the leading edge of the document. When the platen cover 61 is closed, the background image is the platen cover 61, and when the platen cover 61 is open, the background image is almost black.

  As described above, when the processing target document is shifted from the reading range, the platen glass 112 side (platen back) of the platen cover 61 is moved when the platen cover 61 serving as the document table cover is closed during the background processing. In addition, when the platen cover 61 is opened, black is regarded as a document and background amount data is collected. Therefore, the background information of the document cannot be detected correctly, and the background density level and saturation in the output image vary. The quality of the output image deteriorates.

  Therefore, in the present embodiment, in order to solve this problem, a background portion such as a platen back is detected by performing background detection processing for the front half in the sub-scanning direction using the histogram background detection processing unit 310, and as a result. In response, the front end of the document is specified and the background removal process is performed.

  FIG. 6 is a diagram illustrating a detailed example of the histogram background detection processing unit 310. The histogram background detection processing unit 310 receives L, a, and b signals obtained by color-converting the R, G, and B signals acquired by the image acquisition unit 10 as input data Vin. The input data Vin represents an image of a document placed on the platen glass 112. The component includes not only the document but also a component of the platen cover 61.

  For example, as shown in FIG. 6A, the histogram background detection processing unit 310 includes a back area counter 312 that contributes to specifying the background portion, an area area counter 314 that contributes to background detection of the document portion, and a determination unit 318. I have. The back area counter 312 and the area area counter 314 pass the count result to the determination unit 318.

  The back area counter 312 is used to set a brightness and saturation area having a certain width and create a histogram in the area. For example, the platen cover 61 has a function of detecting the platen glass 112 side (platen back) when the platen cover 61 is closed, and detecting a background portion such as black when the platen cover 61 is opened.

  The back area counter 312 increases the counter value when the input image data Lab indicates the background portion for each pixel from the main / sub scanning reference. In other words, the background portion such as the platen back is detected by detecting a specific color or density that can be a background portion such as the lightness L and saturation a, b or black of the platen back. When the document is placed with an inclination with respect to the reading range, the pixels of the background portion and the document portion are mixed in one line, but the two can be separated by analyzing the histogram.

  Specifically, as shown in Expression (1), when the input image data Lab falls within a predetermined range (pixel determination threshold) of lightness L and saturations a and b corresponding to platen back and black, the back area The counter value of the counter 312 is increased.

  Since the brightness and saturation of the platen cover 61 or the black level when the cover is open varies, an area having a width is set and detection is performed in that area. With respect to the brightness L range PLmin to Lmax, the saturation a range Pamin to Pamax, and the saturation b range Pbmin to Pbmax corresponding to the black level when the platen back or the cover is open, the platen cover 61 is not used in advance. A predetermined margin may be set for the data (center value) when read in the closed state. Or it is good also as what can be arbitrarily changed by operation from a user interface.

  For example, when receiving the Lab signal, the back area counter 312 sequentially sets each pixel information in the Lab signal as a pixel of interest and compares it with a pixel determination threshold value stored in a memory (not shown) or the like. For example, as shown in FIG. 6B, the pixel determination threshold is for setting a threshold space indicating the range of brightness and saturation of the platen back in the three-dimensional space region of L, a, and b. However, at this time, as the threshold space, two of the specific color space C1 and the monochrome space C2 are set.

  The specific color space C1 corresponds to a color space to which only specific brightness / color corresponding to the platen back belongs. Here, the specific color space C1 for specifying the platen back is set for both lightness and saturation. However, the present invention is not limited to this, and only one of lightness and saturation may be set. . The black and white space C2 corresponds to a color space representing an achromatic color and corresponds to when the cover is open.

  The histogram background detection processing unit 310 determines whether the pixel of interest is a background pixel depending on whether the value of the Lab signal of the pixel of interest belongs to either the specific color space C1 or the monochrome space C2. Roughly categorize whether it is a pixel. For example, if the value of the Lab signal of the pixel of interest belongs to one of the specific color space C1 and the black and white space C2, the histogram background detection processing unit 310 determines that the pixel is a background portion pixel. If the pixel does not belong to either the specific color space C1 or the monochrome space C2, it is determined that the pixel is a pixel of the original portion. Then, the count value of the back area counter 312 is incremented by one. Histogram analysis can be performed by sequentially processing this count process for all pixels of the processing target line.

  Whether the platen cover 61 is open or closed is detected by a predetermined sensor. When the platen cover 61 is closed, the pixel is only in the case of belonging to the specific color space C1. It is determined that the pixel is in the background portion (that is, the platen cover 61), and when the platen cover 61 is opened, the pixel is in the background portion only when belonging to the monochrome space C2. You may judge. In the former case, it is possible to prevent the black character pixel in the document from being recognized as the background portion.

Further, for example, as shown in FIG. 6C, the histogram background detection processing unit 310 focuses on only the saturation of the Lab signal, that is, the two-dimensional space of the signals a ^* and b ^* , and specifies the space within the space. Two color spaces C1 and monochrome space C2 may be set and compared.

  The histogram background detection processing unit 310 includes an area area counter 314 as a configuration for detecting the background of a document by histogram analysis. Here, a technique similar to the technique described in Japanese Patent Laid-Open No. 4-37258 is adopted as a histogram analysis technique provided with the area area counter 314. For example, input data (in this case, brightness data) is processed in blocks. For this reason, as the area area counter 314, counters corresponding to the area are prepared. Each counter of the area area counter 314 is used to set a density area having a certain width and create a histogram in the density area.

  If the processing result of the first processing system including the histogram background detection processing unit 310 and the histogram background removal processing unit 410 is applied to the document portion by making the brightness data into blocks and performing the background processing, the density distribution over the entire surface of the document can be obtained. Since the histogram is created and the background density area is determined, each of the background density areas can be accurately detected even in a laminated document in which a plurality of background densities are mixed, and the optimum background removal threshold value can be determined.

  In addition, since the density region is divided and the processing is performed only in a general background density region, circuit components such as a counter can be reduced. In addition, by setting the density area with a width corresponding to the unevenness of the background density, or by setting the area by overlapping, it is possible to improve the peak detection accuracy of the histogram and cope with the unevenness and unevenness of the background density.

  FIG. 7 is a diagram for explaining the function of the area area counter 314. It may be considered that the background density of the document is limited to the lower predetermined range in the image data of the entire density range of the input image (for example, 256 gradations at 8 bits). Therefore, in the present embodiment, the number of counters is reduced by setting a region having the highest background density, which is a general background, for example, a region up to about 138 in a newspaper.

  Since the degree of background density variation varies depending on the document, the width of the density region is changed for each density region corresponding to the document, so that the number of counters can be reduced and the variation caused by the document can be reduced. However, the determination and the background removal process are performed with high accuracy.

  Further, the density data of 0 to 138 is divided into 10 blocks as shown in FIG. 7B according to the uneven background document so that the density for creating the histogram has various widths. Then, as shown in (A), (C), and (D) in the figure, when the peaks are overlapped by half and the peak is found, next, the two neighbors are not selected.

  Each area area counter 314 of each histogram area (area No .: No. 1 to No. 9 in this example) is input image data for each pixel from the main / sub reading reference as shown in Expression (2). It is determined whether or not the lightness component L of the Lab is within the respective density ranges, and if applicable, the counter value is increased. That is, it is detected to which density range the lightness component L of the input image data Lab corresponds.

Thereafter, the determination unit 318 evaluates a counter value for each line, that is, a histogram.
Each time line processing ends, the count value of each histogram is evaluated, and it is determined whether or not the evaluation target line corresponds to the document area as shown in Expression (3). If applicable, the document area IN signal (control signal CN1) is made active. This document area IN signal is used to separate the background portion from the document leading edge when the leading edge in the sub-scanning direction is actually a background portion instead of the document because the document is placed out of the reading reference. .

  Here, the determination evaluation value α is a platen back region determination change amount. For example, the number of divided blocks for histogram counting x · 1/5> α = 0 may be set, and it may be determined that the change amount of the platen back area data is extremely decreased.

  Further, the determination evaluation value β is a change amount of determination of background data in the original document. For example, the number of divided blocks for histogram counting x · 1/4 <β <the number of divided blocks x · 1/2 may be set, and it may be determined that the data count of the document area is started.

  From these two AND (logical product) conditions, it can be estimated that the line under histogram analysis is in the document. The determination evaluation values α and β are not fixed, but may be changed as appropriate via a user interface (not shown).

  FIG. 8 is a timing chart for explaining the background processing function in the present embodiment. The image input unit 200 takes in data from the image acquisition unit 10 and passes it to the background detection unit 300 and the background removal processing unit 400 (t20 to t21).

  The histogram background detection processing unit 310 of the background detection unit 300 uses a histogram detection process after a predetermined time delay after capturing the image, and uses the histogram detection processing to provide background information (background density) of the processing target image passed from the image input unit 200. Is started (t21 to t24).

  Here, the histogram background detection processing unit 310 performs histogram analysis on the pixel data on the tip side in the sub-scanning direction of the image reading range as a processing target, thereby determining the definite value DTH of the background information (background density) of the processing target image. Try to detect.

  For example, the histogram background detection processing unit 310 creates a histogram of the background information distribution of the document based on the background detection pixel data (the number of which sequentially increases) sequentially obtained after the reading is started, and the frequency of the histogram Is determined from the high density side, and the background removal threshold value TL is determined as the ground color image data DTH based on the first density area exceeding the predetermined frequency.

  At this time, ground color information (density information) is first detected for each line, and the background removal threshold value TL is converged based on the ground color information for each line. Get a definite value of. At this time, the histogram background removal processing unit 410 performs background removal processing using the ground color image data DTH obtained for each line, and the switching output unit 480 outputs the processing result.

  As a result, until the histogram background detection processing unit 310 detects the leading edge of the document, it is possible to output an image that has been subjected to the background processing by the first processing system that emphasizes reliability. For example, as shown in FIG. 5A, even when the document is inclined and the leading edge of the document is detected at the Top position in the drawing, the histogram background is related to the area S1 in which the background portion increases as line data. The background removal processing result by the removal processing unit 410 can be output. The background information of the original can be detected with a certain degree of accuracy, and it may be considered that there is almost no background discontinuity with the image subjected to the background processing by the second processing system after the leading edge of the original.

  On the other hand, if an image subjected to background processing by the second processing system that performs background detection and background removal for each line with respect to this area S1 is output, the background portion of the line data increases, so that the background information of the document is accurately detected. It cannot be detected well, and background processing is performed at a level different from that of the document leading edge and output, so that discontinuity of the background may occur greatly in the output image.

  Next, when the document is placed with a deviation from the reading reference, the histogram background detection processing unit 310 detects that the front end side in the sub-scanning direction is actually a background portion instead of the document, and controls the control signal CN1 (document The background portion and the front end of the document are separated by the area IN signal. In the figure, the histogram background detection processing unit 310 detects the leading edge of the document at time t22.

  When the processing target line enters the document area (t22), the histogram background detection processing unit 310 notifies the tip real-time detection unit 320, the adaptive tip real-time detection unit 330, and the switching output unit 480 to that effect.

  The tip real-time detection unit 320 and the adaptive tip real-time detection unit 330 start the background detection processing from the line after receiving the control signal CN1 as the processing target of the background processing, and the real-time background removal corresponding to the detection result. By passing the processing to the processing unit 420 or the adaptive real-time background removal processing unit 430, the background processing focusing on the document portion is performed as a whole.

In addition, when the processing target line reaches a predetermined position (hereinafter referred to as a tip detection area end position), the tip real-time detection unit 320 and the adaptive tip real-time detection unit 330 stop the background detection process (t23 in the figure), and thereafter ( The real-time background removal processing unit 420 and the adaptive real-time background removal processing unit 430 perform background removal processing based on the background detection amounts DTR and DTRa at the stop point (t23).
As the leading edge detection area end position, for example, it is preferable that the leading edge detection area is positioned about 20 mm from the leading edge of the document. In this way, the adaptive real-time AE processing identifies yellowishness and color conditions within the range from the document leading edge to 20 mm, and removes the same background from the leading edge of the output using a pipeline delay until the output. Is used as a possible system. An advantage that the detection accuracy can be ensured can be obtained by restricting that the data of the platen back is included in a short range of about 20 mm on the front end side of the document. In addition, regarding the histogram AE and the normal real-time AE, there is also a mode for determining the ground data collection by detecting the 20 mm tip.

  Even if the leading edge position of the document and the reading start position are misaligned depending on how the document is placed, the background part such as the platen back area is treated as a dead area, and the background part is collected as the document background data. Can be prevented. Since the histogram background detection processing unit 310 sequentially detects the leading edge of the document from the leading edge of the reading range, the dead zone in the processing target direction (sub-scanning direction in this example) is dynamically and adaptively applied regardless of how the document is placed with respect to the reading range. Can be set automatically.

  After receiving the control signal CN1, the switching output unit 480 receives one of the processed signals of the real-time background removal processing unit 420 and the adaptive real-time background removal processing unit 430 from the processed signal of the histogram background removal processing unit 410. And output as output image data Vo. The image of the original portion in the reading range is the portion after t22.

  In the case where the histogram background detection processing unit 310 misses the background amount detection processing and cannot detect the leading edge of the document well, the background detection is performed at time t24 by detecting the background on the leading edge side of the document (for example, up to the middle point of the document). When the determined value of the detection value DTH is obtained, the background removal processing result made by the histogram background removal processing unit 410 is output based on the background detection value DTH each time until the determination time t24. After the confirmation time t24, the background removal processing result obtained by the histogram background removal processing unit 410 can be output based on the detection level at the confirmation time t24. That is, the detection result of real time AE is used as it is. Even when the histogram background detection cannot be performed properly, the switching output unit 480 always outputs the image data.

  As described above, according to the processing of the present embodiment, until the leading edge of the document is detected, the histogram background detection processing unit 310 and the histogram background removal processing unit 410 perform reliability-oriented background processing and output the result. After detection processing unit 310 detects the leading edge of the document, switching to speed-oriented background processing by leading edge real-time detection unit 320 and real-time background removal processing unit 420 or adaptive leading-edge real-time detection unit 330 and adaptive real-time background removal processing unit 430 is switched. Output.

  As a result, even if there is a deviation between the leading edge position of the document and the reading start position depending on how the document is placed, the discontinuity of the background density is reduced by connecting the leading edge portion of the document as the switching portion. By performing real-time background removal processing within the document range, background removal processing excellent in both speed and accuracy can be performed. There is no need for pre-scanning.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the gist of the invention, and embodiments to which such changes or improvements are added are also included in the technical scope of the present invention.

  Further, the above embodiments do not limit the invention according to the claims (claims), and all combinations of features described in the embodiments are not necessarily essential to the solution means of the invention. Absent. The embodiments described above include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. Even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, as long as an effect is obtained, a configuration from which these some constituent requirements are deleted can be extracted as an invention.

  For example, in the above-described embodiment, after the leading edge of the document is detected by the first processing system that performs background processing capable of acquiring ground color information (background information) with high reliability, the second processing is performed for speed-oriented background processing. I switched to the processing system.

  However, after detecting the leading edge of the document by the first processing system, at least a second processing system that detects background information based on only image data in the document and performs background removal, saturation correction, and the like is provided. In many cases, the second processing system does not need to be a processing system that performs ground processing with an emphasis on speed.

  For example, the configuration includes a histogram background detection processing unit 310 and a histogram background removal processing unit 410. After the histogram background detection processing unit 310 detects the leading edge of the document in the sub-scanning direction, it is out of the original document range. The histogram information acquired based on the data is once swept away, and the histogram analysis is performed based only on the image data in the document in the sub-scanning direction, thereby shortening the time required to acquire the final value of the background detection amount DTH. (Refer to the time t24a in FIG. 8).

  The mechanism of the background detection and background removal processing described above is not limited to being configured by a hardware processing circuit such as an ASIC (Application Specified Integrated Circuit), but is based on a program code that realizes the function. ) Can also be realized in software.

  Therefore, a program suitable for realizing the image processing apparatus and the image reading apparatus according to the present invention by software using an electronic computer (computer) or a computer-readable storage medium storing the program is extracted as an invention. You can also. By adopting a mechanism that is executed by software, it is possible to enjoy the advantage that the processing procedure and the like can be easily changed without changing hardware.

  When making a computer execute a series of background detection processing and background removal processing by software, a program (such as an embedded microcomputer) or a CPU (program that constitutes the software) is installed in dedicated hardware. By installing functions such as Central Processing Unit), logic circuits, and storage devices on a single chip to achieve the desired system, you can install a system on a chip (SOC) or various programs. The software is installed from a recording medium in a general-purpose personal computer or the like that can execute various functions.

  The recording medium causes a change state of energy such as magnetism, light, electricity, etc. to the reading device provided in the hardware resource of the computer according to the description content of the program, and in the form of a signal corresponding thereto. The program description can be transmitted to the reader.

  For example, a magnetic disk (including a flexible disk FD), an optical disk (CD-ROM (Compact Disc-Read Only Memory)), a DVD on which a program is recorded, which is distributed to provide a program to a user separately from a computer. (Including Digital Versatile Disc), magneto-optical disc (including MD (Mini Disc)), or package media (portable storage media) made of semiconductor memory, etc. It may be configured by a ROM, a hard disk, or the like in which a program is recorded, which is provided to the user in a state of being recorded. Or the program which comprises software may be provided via communication networks, such as a wire communication or radio | wireless.

  A storage medium in which a program code of software that realizes a background detection processing function and a background removal processing function is recorded is supplied to a system or apparatus, and a computer (or CPU or MPU) of the system or apparatus is stored in the storage medium By reading and executing the code, the same effect as that achieved by the hardware processing circuit can be achieved. In this case, the program code itself read from the storage medium realizes the functions of background detection processing and background removal processing.

  In addition, based on program code instructions, an OS (Operating Systems; basic software) running on a computer performs part or all of actual processing, and performs background detection processing and background removal processing by the processing. May be realized.

  Further, after 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, the function expansion is performed based on the instruction of the program code. The CPU or the like provided in the card or the function expansion unit may perform a part or all of the actual processing, and a function of performing background detection processing or background removal processing by the processing may be realized.

  Note that the program is provided as a file describing a program code for realizing the function of performing background detection processing and background removal processing. In this case, the program is not limited to being provided as a batch program file, and is configured by a computer. Depending on the hardware configuration of the system, it may be provided as an individual program module.

1 is a side cross-sectional view illustrating an outline of an embodiment of an image reading apparatus including an image processing apparatus including a background removal processing circuit according to the present invention. FIG. 2 is a block diagram illustrating an embodiment of an image processing unit provided in the image reading apparatus illustrated in FIG. 1. It is the figure which showed the detail of the background detection part and the background removal process part. It is a figure explaining the relationship between the state of the original document mounted on platen glass, and a reading range. (Part 1) It is a figure explaining the relationship between the state of the original document mounted on platen glass, and a reading range. (Part 2) It is a figure explaining the detailed example of a histogram base | substrate detection process part. It is a figure explaining the function of an area area counter. It is a timing chart explaining a background removal function.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 3 ... Image reading apparatus, 5 ... Image forming apparatus, 10 ... Image acquisition part, 14 ... Read signal processing part, 16 ... Optical scanning system, 20 ... Image processing part, 61 ... Platen cover, 112 ... Platen glass, 120 ... Exposure Light source, 139... Lens, 140 light receiving unit, 200 image input unit, 280 signal processing unit, 300 background detection unit, 310 histogram background detection processing unit, 312 back area counter, 314 area area counter, 318 ... Determining unit, 320 ... Tip real-time detection unit, 330 ... Adaptive tip real-time detection unit, 332 ... Tip real-time detection unit, 334 ... Color judgment unit, 336 ... Determination unit, 360 ... Switching unit, 400 ... Background removal processing unit , 410 ... Histogram background removal processing section, 420 ... Real-time background removal processing section, 430 ... Adaptive real-time background removal processing Management unit, 480 ... switching output section, 500 ... signal processing unit, 600 ... output data processing unit, 906 ... image forming unit, 964 ... print engine

Claims (7)

An image reading apparatus that reads an image of the original by moving a document to be read relative to a light receiving unit that reads the original in a predetermined movement direction,
The background information of the processing target image read by the light receiving unit is sequentially acquired in the processing target direction, and the acquired background information is subjected to histogram analysis to detect the leading edge of the document in the moving direction in the processing target image . A tip detector that
A background detection unit that determines the background information of the document in the processing target image for each line based on an image signal obtained by the light receiving unit after the front end detection unit detects the front end;
An image reading apparatus comprising: a background removal processing unit that reduces the background information of the document portion in the output image for each line based on a detection result of the background detection unit. A leading edge detection unit that sequentially acquires the background information of the processing target image represented by the image signal in the processing target direction, and analyzes the acquired background information by histogram analysis, thereby detecting a leading edge of the effective image portion in the processing target image ; ,
Based on the image signal after the tip detection unit has detected the tip, a background detection unit that determines the background information in the processing target image for each line ;
A background removal processing unit that reduces the background information of the effective image portion of the output image for each line based on the detection result of the background detection unit;
An image forming apparatus comprising: an image forming unit that forms a visible image on a predetermined recording medium based on an output image in which the background information is reduced by the background removal processing unit. An image processing apparatus that detects background information of a processing target image and performs image processing for forming an output image corresponding to the processing target image based on the detected background information.
A tip detection unit for detecting the tip of the effective image portion in the processing target image represented by the image signal;
A background detection unit that detects background information in the processing target image based on the image signal after the tip detection unit has detected the tip;
A background removal processing unit that reduces the background information of the effective image portion in the output image based on a detection result of the background detection unit ;
With
The leading edge detection unit sequentially acquires background information of the processing target image in a processing target direction, detects the leading edge by analyzing the acquired background information by histogram analysis,
After the leading edge detection unit detects the leading edge, the ground detection unit determines ground information for each line of the processing target image, and the ground removal processing unit performs line by line based on the detection result of the ground detection unit. Reduce the background information
An image processing apparatus. The background removal processing unit performs a process of reducing the background information of the effective image portion based on the background information acquired by the tip detection unit until the tip detection unit detects the tip. The image processing apparatus according to claim 3 . The image processing apparatus according to claim 3 , wherein the background detection unit determines the background information of the processing target image with emphasis on detection speed. The background detection unit determines the background information based on information on brightness of the processing target image, determines a ground color type of the processing target image based on information on saturation of the processing target image,
The background removal processing unit, and characterized by performing a process wherein the obtained by the background detection unit base information of the detection result and said ground color species separately based, to reduce the underlying information in accordance with the background color type The image processing apparatus according to any one of claims 3 to 5 . A program for detecting background information of a processing target image and performing image processing for forming an output image corresponding to the processing target image based on the detected background information using a computer,
The computer,
A leading edge detection unit that sequentially acquires the background information of the processing target image represented by the image signal in the processing target direction, and analyzes the acquired background information by histogram analysis, thereby detecting a leading edge of the effective image portion in the processing target image; ,
Based on the image signal after the tip detection unit has detected the tip, a background detection unit that determines the background information in the processing target image for each line ;
A program that functions as a background removal processing unit that reduces the background information in an output image for each line based on a detection result of the background detection unit.

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