JP2010153975A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of correctly detecting the outline of a document without being affected by density of the document. <P>SOLUTION: An illumination light source is arranged so that the shadow of a document can be formed in an upper part of a read image of a first surface of the document, and another illumination light source is arranged so that a shadow of the document is formed in a lower part of a read image of a second surface the document. Both the surfaces of the document are read, an end of the upper part of the document is detected from an image read from the first surface, and an end of the lower part of the document is detected from an image read from the second surface. The outline of the entire document is obtained by combining both the detection results with each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that reads image information of a document.

  In general, an image reading apparatus is equipped with a contour detection function for detecting the size and inclination of a document from a read image. For example, a member on the opposite surface of the image reading sensor is a black member, a black and white binary image is created with a predetermined threshold value, and changes in the peripheral area (white part) and background area (black part) of the document in the binary image The contour is detected based on the above. However, in a document with a black peripheral edge, it is difficult to detect the boundary position between the background and the document portion. In order to avoid this problem, in the image reading apparatus disclosed in Patent Document 1, the color of the opposing member is set to a color having a high reflectance.

In particular, in a sheet feed scanner that reads a document while conveying it, the member on the opposite surface of the image reading sensor is made white, and the read image is subjected to primary differentiation or secondary differentiation in the sub-scanning direction to generate differential information. There is also a differential information generating means for detecting a document boundary by utilizing a large change in differential information at the upper and lower ends of the document.
JP 2005-57813 A

However, in an image reading apparatus provided with a black background member, in a document with a black peripheral edge, the difference between the document density and the background density is small, making it difficult to detect the contour of the document. On the other hand, in the contour detection method for detecting a shadow formed on a white background member devised to avoid the difficulty of contour detection in a black background, when the document density is sufficiently bright, that is, between the document density and the background density. When the difference is small, the differential information may not obtain a sufficient change value. In this case, it is possible to capture a small change by increasing the detection sensitivity of the differential information, but on the other hand, the resistance to noise is weakened, which causes a false detection. Thus, it has been difficult to accurately detect the contours of various types of originals.

An object of the present invention is to provide an image reading apparatus capable of accurately detecting the contour of a document.

In order to achieve the above object, an image reading apparatus according to the present invention includes first image data including image information of a first document surface from a document and second image data including image information of a second document surface. In the image reading apparatus, the first end of the document is detected from the first image data, the second end of the document is detected from the second image data, and the detected first And a contour detecting means for detecting the contour of the document based on the second end portion.

The outline of the original can be accurately detected regardless of the brightness of the original surface, such as a bright original or a dark original.

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

  FIG. 4 illustrates an image reading system in which the image reading apparatus 1 of the present invention and the host computer 2 are connected by a general-purpose communication cable 3. FIG. 1 is a cross-sectional view for explaining a conveyance path of an image reading apparatus according to the present invention. The image reading apparatus has a mechanism in which the original 101 is separated from the original bundle on the original table 102 one by one by the paper feed roller 106 and the like, sent to the conveyance path 108, and conveyed along the conveyance path by the conveyance roller 107. The image reading apparatus reads an image from a document passing in front of the image reading sensor units 104 and 105 and discharges the image to the paper discharge unit 103.

FIG. 2 is a circuit block diagram of an image reading apparatus provided in the image reading apparatus 1 according to the present invention. The image reading apparatus 1 includes a control circuit board 200, a CPU 202, a RAM 203, a ROM 204, a reading unit 206, and a motor driver. 207, a stepping motor 208, an external I / F 205, and the like. The CPU 202, RAM 203, ROM 204, reading unit 206, motor driver 207, and external I / F 205 are connected to each other via a system bus 201.

The CPU 202 controls the entire image reading apparatus. A RAM 203 provides a work area to the CPU 202 and functions as a buffer memory that temporarily stores image data obtained from the reading unit 206 during image scanning. The ROM 204 stores various programs and initial setting values.

The reading unit 206 includes an A / D converter and a shading correction processing unit (not shown) for controlling the image reading sensor 209 and processing an image signal from the image reading sensor 209. The reflected light of the light irradiated on the document surface by the illumination LED 210 is read by the image reading sensor 209, the read analog image signal is A / D converted, shading correction is performed, and the image data is written to the RAM 203.

The paper feed roller 106 is driven by a gear, a belt, a motor, and a motor driver (not shown), and is controlled by the CPU 202. The conveyance roller 107 is connected to the stepping motor 208 by a gear and a belt (not shown). The stepping motor 208 is controlled by the CPU 202 through the motor driver 207.

FIG. 3 is an enlarged cross-sectional view of the front surface image reading sensor unit and the back surface image reading sensor unit of the image reading apparatus. As shown in FIG. 3, the surface image reading sensor unit 104 is a unit sealed by a housing 301 and glass 304. In the image reading sensor unit 104, an illumination lamp 302, an image reading sensor 303, and a background plate 305 serving as a background member when the back side of the document is read by the back side reading sensor unit are provided. On the other hand, the back surface image reading sensor unit 105 has the same configuration. In FIG. 3, it is assumed that an image is read from a document conveyed from right to left.

When image reading is started by the user operating the host computer 2, after the paper feeding roller is driven, the registration sensor 109 detects that the document has arrived immediately before the image reading sensor, and illumination is performed after a certain time. The lamps 302 and 307 are turned on, and the image reading sensors 303 and 308 are simultaneously operated to read an image. An image signal output by reading an image is converted into digital image data by the reading unit 206. Furthermore, operations until image data subjected to image processing such as shading correction, gamma correction, edge emphasis processing, etc. for which an image is suitable are sent to the host computer 2 are generally performed scanning operations. is there.

Next, a contour detection process for detecting the contour of a document from image data, which is a feature of the image processing apparatus, will be described.

FIG. 5 shows the positional relationship between the light source (illumination LED) and the image reading sensor in the image reading apparatus. In FIG. 5, if the document is conveyed from right to left as in FIG. 3, the image reading sensor (surface image reading sensor) first reads the reflected light from the background member before the document arrives. As the document approaches, the light emitted from the illumination LED to the background member is blocked, and a shadow of the document is formed on the background member. Therefore, the image reading sensor reads the shadow. When the document is further conveyed thereafter, the image reading sensor reads the document surface. That is, when an image is read from the original shown on the left in FIG. 6, a certain amount of dark shadow portion obtained by reading the shadow is displayed on the upper side of the original image in the read image on the front surface as shown on the right in FIG. Is formed. In FIG. 3, the operation of reading the image by the surface reading sensor unit can be described as described above with reference to FIG.

On the other hand, the operation in which the back side reading sensor unit reads an image in FIG. 3 corresponds to the image reading operation when the document is conveyed from left to right in FIG. That is, after the document has passed through the image reading sensor, the document blocks the light emitted from the illumination LED to the background member. Therefore, the back side scanned image has a dark portion of a certain amount due to a shadow on the lower side of the document image. Is formed. As described above, in this image reading apparatus, the illumination lamp 302 for the front surface and the image reading sensor 303 are arranged as shown in FIG. It is configured as follows. Also, an illumination lamp 307 for the back surface and an image reading sensor 308 are arranged as shown in FIG. 3, and the shadow is read on the lower end side of the document on the back surface by irradiating irradiation light obliquely.

FIG. 7A shows an image in which a shadow portion is formed at the upper end, and a density graph at a position indicated by A is shown in FIG. A method for detecting the document edge will be described with reference to the graph of FIG. 8 and the flowchart of FIG.

FIG. 8 shows an example of a density graph of an original document as in FIG. 7, but this graph shows a document with a bright original surface (bright original) and a document with a dark original surface (dark original) such as blank paper. Both graphs are shown. The slice level th and the shadow length h are fixed values determined in advance. The flowchart in FIG. 9 is a process of scanning in the sub-scanning direction from the upper end position of the read image in a certain column and searching for the end portion of the document image in the read image. First, the CPU 202 performs initialization in step S901. Here, y is a pixel position in the sub-scanning direction, and edge is an upper end position of the detected document image. When the value of edge is −1, it represents that there is no document image edge in the vertical line. In order to perform the processing of step S903 by shifting one pixel at a time in the sub-scanning direction, a loop is formed that repeats the processing from step S902 to step S904. In step S903, pix (y) is the image brightness at the y position (the brighter the value), and when pix (y) is large and bright, it is determined to be the background image, and the loop processing is continued. When pix (y) is equal to or less than th (position P in FIG. 8), it is determined that the upper end of the shadow formed outside the original image in the read image is detected, and the upper end position shadow of the shadow is determined. Store the value of y. Further, the process of detecting the rear end of the shadow, that is, the upper end of the original is performed from the next step, but the value of shadow + h is stored in the upper end position edge of the original in case the upper end of the original is not found. Here, h is a shadow length value, which is obtained geometrically from the positional relationship between the image reading sensor and the light source LED of the image reading apparatus and the distance between the document conveyance path and the background member. .

The loop that repeats the processing from step S906 to step S908 forms a loop processing for repeatedly performing step S907 by shifting one pixel at a time in the sub-scanning direction, up to the smaller one of the height value and the shadow + h value. Processing is to be performed. When the image brightness exceeds th in step S907, it is determined that y has reached the upper end of the document image (position Q in FIG. 8), and the process proceeds to step S909. In step S909, the upper end position is stored in edge and the process ends.

In the case of a bright original as shown in FIG. 8, the determination in Step 907 is YES at the upper end of the original image in the read image, whereas in the case of a dark original, the determination in Step 907 is always NO. In the case of a dark original, the loop process is terminated without performing the process of Step 909, and therefore the edge value is terminated with shadow + h. In other words, in the case of a bright original, the upper end of the original is detected as it is, and in the case of a dark original, the upper end of the shadow formed on the original image is detected and calculated using the distance h therefrom. The position of the document can be specified regardless of the brightness of the document.

As described above, by performing original image edge detection based on a change in brightness in the sub-scanning direction for all the columns of the entire image, a set of edge positions can be obtained as shown in FIG. By performing the same processing on the back surface shaded at the lower end, the set of edge positions shown in FIG. 10B can be obtained.

In the figure showing the upper and lower document edges illustrated in FIG. 10C, first, a mirror image is created by inverting the left and right in FIG. 10B, and further combined with the upper document edge in FIG. 10A. Can be made. By drawing an auxiliary line from the edge of the set at one edge position in FIG. 10C to the end of the set at the other edge position, the outline of the entire document can be obtained as shown in FIG. I can do it. Further, in order to create a diagram representing the outline of the document image on the back side, first, the left and right in FIG. 10A are reversed and aligned with FIG. 10B to draw an auxiliary line.

As described above, in this embodiment, a shadow is generated at the upper end of the front image and at the lower end of the back image, and both sides of the document are read to obtain the outline. Regardless of whether the original is a dark original or not, a stable and accurate contour detection result can always be derived. Furthermore, if this invention is used, the tolerance to the noise of outline detection can be raised easily. In this embodiment, a shadow is generated at the upper end of the front image and at the lower end of the back image. However, a shadow may be generated at the lower end of the front image and at the upper end of the back image.

The contour detection process of the present embodiment may be used in combination with, for example, a well-known document size detection process that cuts out a minimum area having a contour as a boundary. Further, the contour detection process of the present embodiment may be used in combination with a well-known tilt detection process.

For example, the inclination may be calculated from the contour, and a warning may be given to the user when the inclination is large, or rotation processing may be performed so that the original image read using the detected inclination is erected.

The contour detection processing of this embodiment is executed by the CPU 202 based on the processing program stored in the ROM 204, but may be executed by another CPU (not shown) or the like. Further, part or all of the contour detection processing of the present invention may be realized by processing by hardware.

The contour detection process of the present invention may be executed by an external device such as the host computer 2. In this case, an image reading system including the image reading device and an external device connected thereto corresponds to the image reading device of the present invention.

Schematic sectional view of the image reading device Block diagram of control system of image reading device Sectional drawing of the image reading sensor unit in the image reading apparatus of this invention Schematic diagram of a system connecting an image reading device and a host computer The figure for demonstrating the positional relationship of a light source and an image reading sensor. Illustration for explaining the shadows that appear in the image when the document is scanned Figures and graphs for explaining the effect of document shadows on the brightness of scanned images The figure for demonstrating the method to detect the image edge of a document Flowchart of processing for detecting image edge of document The figure for demonstrating the outline detection process of the original document from the set of the front and back edge positions

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reading apparatus 2 Host computer 3 Communication cable 101 Original 102 Original stand 103 Paper discharge part 104 Front surface image reading sensor unit 105 Back surface image reading sensor unit 106 Paper feed roller 107 Conveyance roller 108 Conveyance path 109 Registration sensor 200 Control circuit board 201 System Bus 202 CPU
203 RAM
204 ROM
205 External Interface 206 Reading Unit 207 for Controlling Image Reading Sensor Motor Driver 208 Stepping Motor 209 Image Reading Sensor 210 Light Source (Lighting LED)
301 Image reading sensor unit housing 302 Light source 303 Image reading sensor 304 Glass 305 Background plate 306 Image reading sensor unit housing 307 Light source 308 Image reading sensor 309 Glass 310 Background plate 311 Document 312 being conveyed Reflected by the background plate and received Optical path 313 of light reflected and received by the document surface 314 Optical path of light reflected and received by the background plate 315 Optical path of light reflected and received by the document surface

Claims (4)

In an image reading apparatus that reads first image data including image information of a first document surface and second image data including image information of a second document surface from a document,
Detecting a first edge of the document from the first image data;
Detecting a second edge of the document from the second image data;
An image reading apparatus comprising contour detecting means for detecting a contour of a document based on the detected first and second end portions. A first light source for irradiating light on the first document surface;
A first image reading sensor for receiving reflected light from the first document surface;
A second light source for irradiating light on the second document surface;
A second image reading sensor for receiving reflected light from the second document surface;
The first light source is disposed at a position where light is irradiated obliquely toward the first document surface so that a shadow is generated on the first end side of the document,
2. The first light source according to claim 1, wherein the second light source is arranged at a position where light is irradiated obliquely toward the second document surface so that a shadow is generated on the second end side of the document. The image reading apparatus described. The contour detection means includes
3. The outline of the document is detected by connecting the detected end of the first end to the end of a mirror image obtained by inverting the detected second end. Image reading apparatus. An outline detection method for an image reading apparatus that reads first image data including image information on a first original surface and second image data including image information on a second original surface from an original,
Detecting a first edge of the document from the first image data;
Detecting a second edge of the document from the second image data;
A contour detecting method for an image reading apparatus, comprising: detecting a contour of a document based on the detected first and second end portions.

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