JP2009194762A - Image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus capable of detecting, with simple configuration, an accurate document placing state also including a document placing angle, regardless of a type of the document. <P>SOLUTION: A sheet body provided on a platen-glass side surface of a platen cover is prescanned in a state where the sheet body is made white, to capture first image data (a) and the sheet body is prescanned in a state where the sheet body is made black, to capture second image data (b). Differential image data (c) between the first image data and the second image data are determined. In the differential image data, a document region becomes a bottom gradation level (black level) and a background, other than the document region, becomes a peak gradation level (white level). On the basis of the differential image data, the document placing state (document position, document size and document tilting angle) is detected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image processing apparatus that reads an image of a document placed on a document table by optical scanning, and more particularly to an image processing device that easily detects a document placement state on a document table.

  In the case of an FBS (Flat Bed Scanner) system that reads an image of a document placed on a platen (platen) by optical scanning, the document is placed on the platen to prevent the document from floating or moving. Optical scanning is performed in a state where the document is held by a document presser (platen cover). At this time, the surface of the platen cover that comes into contact with the original is read together with the original as the background of the original during optical scanning.

In Patent Document 1, for the purpose of preventing show-through of a document, the color of the surface of the platen cover that comes into contact with the document is black depending on whether the document is a standard size or an irregular size. And a document reading apparatus that controls the background color of the document.
JP 2001-2108018 A

  When an image of a document is read by the FBS method, when the document is placed in an inclined state without being placed at the correct position on the document table, optical scanning is performed in the oblique state as it is to obtain image data. Also, the image is copied in the state of being oblique.

  In order to solve such a problem, an image processing apparatus having an original skew correction function is known. In this image processing apparatus, the image data obtained by optical scanning is analyzed to detect the edge position of the document, the line image of the document, etc., and the document placement angle (oblique degree) is obtained from the detection results, Diagonal correction is performed.

  However, since the document placement angle is obtained by the image data analysis process, a circuit for executing the analysis process is necessary, and there is a problem that the configuration of the apparatus is increased. Further, since the document placement angle is obtained based on the edge position of the document, the line image of the document, etc., an accurate placement angle may not be obtained depending on the type of document (such as a document with a black edge). There is also the problem that it can happen enough.

  The present invention has been made in view of such circumstances, and can detect an accurate placement state of a document including a placement angle of the document with a simple configuration regardless of the type of the document. An object of the present invention is to provide an image processing apparatus capable of performing the above.

  The image processing apparatus according to the present invention is an image processing apparatus that reads an image of the document by optical scanning by pressing a document placed on a document table with a document press. A pressing surface that can be changed to a second density color that is higher than the first density is provided on the document table side, and the pressing surface is used as the first density color and the second density color, respectively. By means of optical scanning to acquire image data, and by first optical data acquired by optical scanning with the pressing surface having the first density color and optical scanning with the pressing surface having the second density color. A difference means for obtaining a difference from the acquired second image data; and a detection means for detecting a placement state of the document placed on the document table based on a difference result by the difference means. To do.

  The document pressing in the image processing apparatus of the present invention has a pressing surface that can be changed between a first density color (for example, white) and a second density color (for example, black) that is higher than the first density. . Then, before reading the original document, optical scanning is performed with the pressing surface as the first density color to obtain the first image data, and optical scanning is performed with the pressing surface as the second density color. Get image data. The difference between the acquired first image data and the acquired second image data is taken, and the placement state of the document placed on the document table is detected based on the difference result (difference image data). The difference result (difference image data) is almost black level in the area where the original is placed (original area) and almost white level in the area where the original is not placed (background area). Therefore, it is possible to accurately detect the document placement state from the difference result (difference image data).

  The image processing apparatus according to the present invention is characterized in that the scanning direction is reverse between optical scanning with the pressing surface having the first density color and optical scanning with the pressing surface having the second density color. To do.

  In the image processing apparatus according to the present invention, when the optical scanning is performed in one reciprocation, the pressing surface is read with the first density color by the forward optical scanning, and the second pressing is performed by the backward optical scanning. Read density color. Therefore, the two optical scans for detecting the document placement state can be performed efficiently and in a short time.

  In the image processing apparatus according to the present invention, the document placement state detected by the detection unit includes a document position, a document size, and a document placement angle on the document table.

  In the image processing apparatus of the present invention, the position of the document, the size of the document, and the document placement angle are accurately detected as the document placement state.

  In the image processing apparatus of the present invention, the first image data acquired by optical scanning with the pressing surface of the document pressing as the first density color and the pressing surface acquired by optical scanning with the second density color darker than the first density. Since the placement state of the document placed on the platen is detected based on the difference result with the second image data, the accurate placement state of the document can be obtained with a simple configuration regardless of the type of the document. Can be detected. As a result, it is possible to easily form a precise copy image on a sheet even when the document is placed on the document table at an angle.

  In the image processing apparatus of the present invention, it is possible to complete the optical scanning with the pressing surface having the first density color and the optical scanning with the pressing surface having the second density in one reciprocal optical scanning. Yes, the processing speed can be increased.

  The image processing apparatus of the present invention can accurately detect the position of the document on the document table, the size of the document, and the placement angle of the document as the detected document placement state.

  Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments thereof. Note that the present invention is not limited to the following embodiments.

  FIG. 1 is a block diagram illustrating a configuration example of a digital multi-function peripheral as an image processing apparatus according to the present invention. In the figure, reference numeral 1 denotes a multifunction device. The multifunction device 1 includes a control unit 10, a ROM 11, a RAM 12, an NCU (Network Control Unit) 13, a modem 14, a reading unit 15, an image data processing unit 16, an image memory 17, and an operation unit 18. , A display unit 19, a recording unit 20, a communication interface 21, a codec 22, and the like, which are connected to each other via a bus 23.

  Specifically, the control unit 10 is configured by a CPU (Central Processing Unit), controls the above-described hardware units connected via the bus 23, and according to a control program stored in the ROM 11. Implement various software functions. The ROM 11 stores various control programs necessary for the operation of the multifunction machine 1 in advance. The RAM 12 is configured by SRAM, flash memory, or the like, and temporarily stores data generated when the control program is executed by the control unit 10.

  The modem 14 is a fax modem capable of facsimile communication, and is directly connected to the NCU 13. The NCU 13 is connected to the public telephone line network L. If necessary, the NCU 13 can connect the modem 14 to the public telephone line network L to enable facsimile communication with an external device via the public telephone line network L. It is said.

  The reading unit 15 acquires image data of a document by reading the document by optical scanning using a CCD (Charge Coupled Device) or the like, and outputs the acquired image data to the image data processing unit 16. Based on the image data acquired by the reading unit 15, the image data processing unit 16 detects a document placement state on a document table (platen glass) described later.

  The image memory 17 is constituted by a DRAM, and stores image data obtained by reading an image of a document, image data received from an external facsimile machine, image data received from an external device via a communication interface 21, and the like. To do. The codec 22 compresses the image data according to a predetermined method (for example, MH, MR, MMR, JBIG, etc.), or decompresses the compressed image data according to a predetermined method.

  The recording unit 20 is an electrophotographic printer device, and prints out an image corresponding to image data of a document read by the reading unit 15 and received image data on a sheet. The operation unit 18 includes various keys necessary for operating the multifunction device 1. The display unit 19 is configured by a liquid crystal display (LCD), and displays an operation status of the multifunction device 1, a display screen to be displayed as the multifunction device 1, characters input from the operation unit 18, and the like. In addition, it is also possible to substitute a part or all of the various keys of the operation unit 18 by using the display unit 19 of a touch panel type.

  The communication interface 21 transmits image data to an external computer or other device connected via a network (not shown), and receives image data from an external device via the network.

  FIG. 2 is a diagram illustrating a configuration example of the reading unit 15. 2A, the reading unit 15 includes a rectangular parallelepiped housing 30, a rectangular platen glass 31 serving as a document table provided on the upper surface of the housing 30, and one side of the upper surface of the housing 30. And a platen cover 32 as a document presser that is attached to be freely opened and closed.

  In addition, a sheet body 33 having a spread corresponding to the reading area of the platen glass 31 is provided on the surface (original pressing surface) of the platen cover 32 facing the platen glass 31. The sheet body 33 is configured by electronic paper that can be changed between white, which is the color of the first density, and black, which is the color of the second density, according to the polarity of the voltage applied.

  FIG. 2B is a block diagram illustrating an example of the internal configuration of the reading unit 15, and FIG. 2B illustrates a diagram viewed from the direction indicated by the arrow A in FIG. Inside the housing 30 is a white fluorescent lamp, and changes the optical path of the reflected light from the original and the sheet body 33, the light source lamp 34 for irradiating light on the original and the sheet body 33 placed on the platen glass 31. The plate-like first mirror 35, second mirror 37, and third mirror 38 are arranged at predetermined positions, respectively, and the longitudinal direction is arranged in parallel with the main scanning direction (direction indicated by x in FIG. 2A). is there. The light source lamp 34 and the first mirror 35 have one end portion of the platen glass 31 as a home position in the sub-scanning direction (the direction indicated by y in FIGS. 2A and 2B), and the other end portion from the home position. It is mounted on the first carriage 36 that can move up to. The second mirror 37 and the third mirror 38 move from the center of the platen glass 31 to the other end in the sub-scanning direction y in response to the movement of the first carriage 36. It is mounted on.

  Further, the housing 30 is provided with an imaging lens 40 for condensing the reflected light from the original and the sheet 33 whose optical path has been changed by the first mirror 35, the second mirror 37, and the third mirror 38. The CCD line sensor 41 into which the reflected light enters through the image lens 40 is also arranged with the longitudinal direction parallel to the main scanning direction x. With such a configuration, the reading unit 15 moves the first carriage 36 and the second carriage 39 in the sub-scanning direction y while the CCD line sensor 41 sets the main scanning direction x as the longitudinal direction to 1 in the sub-scanning direction y. The original image is read line by line.

  With the configuration described above, when the document is placed on the platen glass 31 and the platen cover 32 provided with the sheet body 33 is closed, the first carriage 36 moves in the sub-scanning direction y along the lower surface of the platen glass 31. The reflected light reflected by the document and the sheet member 33 is reflected by the first mirror 35. The reflected light is reflected by the second mirror 37 and the third mirror 38 to change to a predetermined optical path, and the CCD line sensor 41 receives the light incident on the predetermined optical path via the imaging lens 40. Image data is acquired by such optical scanning.

  Next, the operation of the multifunction device 1 will be described. The present invention is characterized by a reading operation in the reading unit 15 of the multifunction device 1, and in particular, based on the prescan (preliminary scan) operation performed before the original document reading and the reading result of the prescan. It is characterized by the operation of detecting the mounting state.

  When the document is placed on the platen glass 31 and the platen cover 32 provided with the sheet member 33 is closed, the optical scanning system (the first carriage 36 and the second carriage 39) is reciprocated once in the sub-scanning direction. Perform pre-scan. In this reciprocation, image data is acquired by optical scanning with the sheet 33 being white in the forward path, and image data is acquired by optical scanning with the sheet 33 being black in the backward path. Image data (first image data) acquired in a state where the sheet body 33 is white and image data (second image data) acquired in a state where the sheet body 33 is black are sent from the reading unit 15 to the image data processing unit 16. Output to.

  The image data processing unit 16 detects the document placement state (document position, document size, document tilt angle) according to the following procedure.

  The image data processing unit 16 obtains difference image data between the input first image data and second image data. FIG. 3 schematically shows each of these image data. FIG. 3 (a) shows the first image data, FIG. 3 (b) shows the second image data, and FIG. 3 (c) shows the difference image data. Show.

  When the pre-scan is performed with the sheet body 33 white, most of the light is reflected by the sheet body 33 because the sheet body 33 is white, and as shown in FIG. The background is almost white. That is, if the image data is represented by 256 gradation levels (0 to 255), the background is almost 255 gradation levels (white level). On the other hand, when the pre-scan is performed with the sheet 33 being black, most of the light is absorbed by the sheet 33 because the sheet 33 is black, as shown in FIG. The background is almost black. That is, in this case, the background is almost 0 gradation level (black level).

  Therefore, when the difference between the two image data is obtained, the first image data and the second image data have substantially the same gradation level in the document area, so that the difference is almost as shown in FIG. 0 gradation level (black level). On the other hand, in the background area, the first image data has a 255 gradation level (white level), and the second image data has a 0 gradation level (black level). Therefore, as shown in FIG. The level is approximately 255 gradation levels (white level). Therefore, it is possible to easily obtain an accurate document area from the difference image data.

A position where the change in gradation level in the difference image data is steep is detected as an end point of the document area. If the document has a rectangular shape, as shown in FIG. 4, two end points (in FIG. 4) whose coordinates in the main scanning direction x are the minimum value and the maximum value are selected from the plurality of end points. Points C and A) and two end points (points B and D in FIG. 4) having the minimum and maximum coordinates in the sub-scanning direction y are extracted, and the x coordinates (x in FIG. 4) of these four end points are extracted. _{a, x B, x C,} x D) and the y-coordinate (in FIG. _{4 y a, y B, y} C, obtaining a y _D).

  Since the area surrounded by these four end points (rectangular ABCD in FIG. 4) corresponds to the position of the document placed on the platen glass 31, the position of the document can be easily detected.

  Also, by calculating the short side (AB or CD in FIG. 4) and the long side (AD or BC in FIG. 4) of the document area, the size of the document can be easily detected.

Further, by obtaining θ satisfying (x _A −x _D ) / (y _D −y _A ) = tan θ, the document inclination angle (θ) can be easily detected.

  Then, after the pre-scan is finished, the original scanning (main scanning) is performed by moving the optical scanning system (the first carriage 36 and the second carriage 39) in the sub-scanning direction, and the image of the original is read. At this time, when there is no concern about show-through, the sheet 33 is white, and when it is desired to prevent show-through, the sheet 33 is black.

  An image based on the image data acquired by the original scan is printed out on a sheet by the recording unit 20. At this time, if necessary, oblique correction is performed in the recording unit 20. However, as described above, the present invention can accurately detect the placement of the original, so that the copy image can be exactly printed on the sheet without tilting. Can be recorded. In addition, since the size of the document can be accurately detected, it is possible to automatically select a suitable size paper.

  Here, as in the present invention, when the background color is switched between white and black and two pre-scans are performed to detect the original placement state (original region), the background color is black and only once. A difference from a case where a pre-scan is performed to detect a document placement state (document region) will be described.

  When the document area is detected based only on pre-scan image data with a black background color, when the background color is dark and close to black, the gradation level change between the document area and the background is small. It is difficult to obtain and an accurate document area cannot be detected. On the other hand, in the present invention, since the document area is detected based on the difference between the prescan image data with the white background color and the prescan image data with the black background color, the background color is An accurate original area can be detected not only for a dark original but also for an original whose upper half is black and whose lower half is white.

  Since the pre-scan in the present invention is for detecting the document area, there is no problem even if the resolution is lowered as compared with the original scan for reading the document. For example, when the original scanning resolution is 600 dpi, even if the pre-scanning resolution is about 100 dpi, there is no problem in detecting the document area.

  In the above-described embodiment, the difference image data is obtained by subtracting the second image data from the first image data. However, when the white level is expressed as 0 gradation level and the black level is expressed as 255 gradation level. Needless to say, the present invention can be performed in the same manner by subtracting the first image data from the second image data to obtain the difference image data.

  In the above-described embodiment, the example in which the sheet 33 at the time of pre-scan is changed to white (first density color) and black (second density color) has been described, but is limited to white and black. However, the present invention can be applied to any combination of two colors having different densities. For example, a combination of pale yellow and black, white and gray may be used.

  In the above-described embodiment, the sheet body 33 constituted by electronic paper is provided on the platen glass 31 (original platen) side of the platen cover 32 (original holder). 32 (original presser) itself may be configured by electronic paper. In other words, the configuration of the document pressing unit is arbitrary as long as the surface of the document pressing unit facing the document table (document pressing surface) can be changed between the first density color and the second density color. It may be.

  In addition, the multifunction apparatus has been described as an example, but it is needless to say that the present invention can be applied to all image processing apparatuses such as a copying machine and a facsimile apparatus that read an image by the FBS method.

1 is a block diagram illustrating a configuration example of a digital multifunction peripheral as an image processing apparatus according to the present invention. It is a figure which shows the structural example of a reading part. FIG. 4 is a diagram illustrating an example of acquired image data and difference image data for explaining a document placement state detection process. FIG. 5 is a diagram illustrating a document area for explaining a document placement state detection process.

Explanation of symbols

1 MFP (image processing device)
DESCRIPTION OF SYMBOLS 10 Control part 15 Reading part 16 Image data processing part 31 Platen glass (original platen)
32 Platen cover (document holder)
33 Sheet body 41 CCD line sensor

Claims (3)

In an image processing apparatus that reads a document image by optical scanning while pressing a document placed on a document table with a document press,
The document pressing member has a pressing surface on the document table side that can be changed between a first density color and a second density color higher than the first density.
Means for optically scanning the pressing surface as the first density color and the second density color, respectively, to acquire image data;
Difference means for obtaining a difference between first image data acquired by optical scanning with the pressing surface having the first density color and second image data acquired by optical scanning with the pressing surface having the second density color. When,
An image processing apparatus comprising: detecting means for detecting a placement state of the document placed on the document table based on a difference result by the difference means.   2. The image processing apparatus according to claim 1, wherein the scanning direction is reverse between the optical scanning in which the pressing surface has the first density color and the optical scanning in which the pressing surface has the second density color. .   The image processing apparatus according to claim 1, wherein the document placement state detected by the detection unit includes a document position on the document table, a document size, and a document placement angle.

Images