JP3538938B2 - Image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus,
In particular, the present invention relates to an image reading apparatus such as a digital copying machine that reads an image using a photoelectric conversion element that converts an optical image obtained by irradiating a document with light into an electric signal.

[0002]

2. Description of the Related Art In recent years, digital copiers for converting an optical image obtained by irradiating a document with light into an electric signal, digitizing the same, and copying the digital image onto a medium such as paper have been developed and put into practical use. In this type of image reading apparatus, an optical image based on input light passing through a document is converted into an analog electric signal using a photoelectric conversion element such as a CCD solid-state image pickup element, and the analog electric signal is amplified and converted into a digital electric signal. After the conversion, various kinds of signal processing are performed. By the way, in a copying machine having a function of automatically setting the size of copy paper, it is necessary to automatically detect the size of a document set on a platen glass when reading a document image is started. .

Conventionally, in a copying machine, the size of a document is detected by irradiating the document with infrared light and arranging a plurality of photosensors for detecting reflected light at positions corresponding to the size of each document. It is common to perform based on the state of each output. However, arranging a photo sensor for each document size increases costs. Therefore, in a digital copying machine that reads an image using a CCD solid-state imaging device as a photoelectric conversion device,
There is a device that detects the size of a document using a D solid-state imaging device (for example, see Japanese Patent Application Laid-Open No. 54-83438). In this detection method, black / gray / mirror processing is performed on the platen cover surface so that black information is given to the CCD solid-state image pickup device in the area outside the original, and the continuous black value from the scanning end is counted. The document size is determined.

[0004]

However, according to the above-mentioned prior art, when dust or paper dust is present on the platen cover surface, it is recognized as white, so that even if it is originally black, Regardless, the document is determined to be the document edge, and there is a problem that the document size is erroneously detected. In order to prevent such erroneous detection, as disclosed in Japanese Patent Application Laid-Open No. 2-277038, the boundary between the original area and the outside area is recognized by recognizing that the original area pixels exist to some extent continuously. , Ie, the edge position of the original, and the original size is detected from the edge position.

[0005] This document size detection method is based on the premise that a fixed region at the document end is a document region pixel (white or the like). However, depending on the original, an image may exist up to the end of the original area. For example, when a character image, a halftone image, or a ladder image is present over the entire original area, it is determined that a predetermined number of original area pixels are not continuous despite the original area depending on the image pattern. Is not detected as a document area, and therefore the edge position of the document cannot be detected.
In some cases, erroneous detection of the document size was caused.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object the object of the present invention for a document in which an image is present up to the edge of the document, such as a full-text document, a ladder chart, a full-dot document. It is another object of the present invention to provide an image reading apparatus capable of accurately determining a document size.

[0007]

An image reading apparatus according to the present invention is an image reading apparatus that reads an image using a photoelectric conversion element that converts an optical image obtained by irradiating a document with light to an electric signal. Te, storage means for storing image data based on the output of the photoelectric conversion element, scans the stored contents of this storage means, first detecting means for detecting a change point of the scanning information, the stored contents of said memory means And scan the scanning information
A second detecting means for detecting that the density of the changing point of the scanning information is equal to or higher than a predetermined density ;
When it is detected that the change point exists continuously over a certain value
The second detecting means scans the change point on the document end side.
It is detected that the change point of the inspection information is higher than the predetermined density.
, Change points on the document edge side
It has an edge detecting means for detecting, a configuration in which a size determining means for determining the document size based on the detected edge position as.

[0008]

In the above-described image reading apparatus, the first detecting means sequentially scans the image data stored in the storage means and detects a change point where the logic of the pixel data is inverted. This change point is a pixel at the boundary of the area when scanning from the area outside the original to the original area. The second detection means is storage means
Scans the image data stored in the
It is detected that there is a predetermined number or more of change points at which the logic reverses within a certain range, that is, that the density of the change points is not less than a predetermined density. The high density of the changing points means that an image such as a character exists up to the end of the document. The edge detecting means determines that the change point of the scanning information is a constant value
When it is detected that the document exists continuously, the change point on the document end side is set as the edge position of the document, and the second detecting means scans the document.
When it is detected that the change point of information is higher than the specified density
Indicates that the change point on the document end side is the edge position of the document. Then, the size determining means determines the size of the document based on the detected edge position.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention applied to, for example, a digital copying machine will be described in detail with reference to the drawings. Note that the present invention is not limited to application to a digital copying machine, and an image is formed by using a photoelectric conversion element such as a CCD solid-state imaging device that converts an optical image obtained by irradiating a document with light to an electric signal. The present invention can be applied to all image reading apparatuses that read an image.

FIG. 1 is a schematic configuration diagram of a digital copying machine to which the present invention is applied. In FIG. 1, a document 1 to be copied is arranged on a platen glass 2 such that one end thereof is in contact with a density reference plate 3, and a back side and a periphery thereof are covered by a platen cover 4. A cover sheet 5 is adhered inside the platen cover 4. In order to detect the open / closed state of the platen cover 4, as shown in FIG. 2, the platen open / close sensor 2 is turned on when the platen cover 4 is closed and turned off when opened.
1 and an angle sensor 22 which is turned off when the platen cover 4 is opened via the actuator 23 and turned on when the platen cover 4 is closed to a predetermined angle.

The original 1 placed on the platen glass 2 is irradiated with light emitted from an exposure lamp 6 directly or by being reflected by a reflector 7. The reflected light from the original 1 based on the irradiation light passes through a reflection mirror 8 and is imaged by an imaging lens 9 on an imaging surface of a CCD solid-state imaging device 10 which is a photoelectric conversion device. The optical system including the exposure lamp 6, the reflector 7, and the reflection mirror 8 is mounted on a carriage (not shown) and is movable in the left-right direction of the figure, that is, in the sub-scanning direction. A line sensor in which pixels are arranged linearly is used as the CCD solid-state imaging device 8, and scanning in a direction perpendicular to the paper surface, that is, main scanning, is electrically performed on the CCD solid-state imaging device 10. The CCD solid-state imaging device 10 generates a C signal based on various timing signals generated by a timing generation circuit 11.
Driven by the CD drive circuit 12.

An analog image signal output from the CCD solid-state image pickup device 10 is amplified by an amplifier 13 and A / D
After being converted into digital data by the converter 14, it is supplied to the digital signal processing circuit 15. The digital signal processing circuit 15 includes a shading correction circuit 151 for performing shading correction on input image data, and a RAM (1) 1 used for the shading correction processing.
52, and a digital filter circuit 153 that performs a filtering process on the image data after the shading correction.
And a reduction / enlargement circuit 154 that performs reduction and enlargement processing on the filtered image data, and a RAM (2) 155 and a RAM (3) 156 used for reduction / enlargement processing.
And a CPU 158 connected to these circuits 151, 153, 154 via a data / address bus 157.

The CPU 158 has a data / address bus 1
Each circuit 15 in the digital signal processing circuit 15 via 57
1, 153, 154, and a motor drive control signal for a drive motor (not shown) of a carriage for driving an optical system, and a lamp control for a drive circuit (not shown) of the exposure lamp 6. A signal is supplied, and a process of detecting the size of the document 1 placed on the platen glass 2 is performed. This document size detection processing will be described later in detail. The image data subjected to various signal processing by the digital signal processing circuit 15 is transmitted to an image forming unit 16.
Supplied to

In the digital copying machine having the above configuration, when the apparatus power is turned on (ON), a carriage (not shown) on which an optical system including an exposure lamp 6, a reflector 7, a reflection mirror 8, and an imaging lens 9 is mounted. ) Moves to the main scanning original reading position. Then, at that position, platen glass 2
By reading the original 1 placed thereon, the original image is formed on the imaging surface of the CCD solid-state imaging device 10 and photoelectrically converted to an analog electric signal. This analog image signal is converted by the A / D converter 14 into n
It is converted into digital data of bits (8 bits in this example). The image data converted into digital data is subjected to shading correction, filtering, reduction / enlargement, and the like in a digital signal processing circuit 15 and then sent to an image forming unit 16 to be printed and formed on paper.

Next, a description will be given of a document size detection process performed prior to reading of a document image. This document size detection processing is performed by the CPU 158, and a functional block diagram for the detection processing is shown in FIG. In the drawing, the RAM (2) 155 stores one line of image data read while the platen cover 4 is being closed. Thereby, the RAM (2) 155
The image data stored in the platen cover 4
Is still open and there is no reflected light, so that the background color of the area outside the original is "black" data. On the other hand, RAM
(3) 156 stores image data of one line read in a state where the platen cover 4 is closed. Accordingly, in the image data stored in the RAM (3) 156, the background color of the area outside the document is “white” because the cover sheet 5 is white.

The image data scanning means 31 includes a RAM (2)
155, the stored contents of the RAM (3) 156 are sequentially scanned. The first detecting means 32 determines, for each of the scanning information of the RAM (2) 155 and the RAM (3) 156 by the image data scanning means 31, a changing point of the scanning information, that is, a boundary between the original area and the outside area of the original. Detect pixels. Specifically, in the conceptual diagram shown in FIG. 4, the area outside the document (the background color outside the document is “black” in the case of the RAM (2) 155), and the RAM (3)
In the case of "156""white"), scanning is sequentially performed from the left and right sides of the drawing toward the document area, and it is detected that the document area pixels are continuously present at a predetermined value or more. In addition, RAM
It is assumed that (2) 155 and RAM (3) 156 store one line of image data along the scanning line L.

Here, taking as an example a case where the size of a document whose color of the document area is white is detected, in this case, the RAM in which the image data of the area outside the document is stored as "black"
(2) Scan the stored contents of 155. At this time, when scanning is performed from the non-document area toward the manuscript area, the pixel data changes from a logic indicating “black” to a logic indicating “white” at the boundary of the area, and “white” pixel data continues. become. On the other hand, when the color of the original area is a black original, the content of the RAM (3) 156 in which the image data of the area outside the original is stored as “white” is scanned, and the original is similarly scanned. It can be detected that the area pixels continuously exist for a certain value or more.

The second detecting means 33 includes a RAM (2) 155 and a RAM (3) 156 by the image data scanning means 31.
Is detected, the density of the change point of the scanning information is equal to or higher than a predetermined density. In particular,
As shown in FIG. 5, when an image is present at the end of the document area, the pixels of the document area do not continue over a certain value when scanning from the outside area to the document area. In the detection means 33, during scanning, black → white or white →
When a black change point is detected, image data within a certain range from the change point is monitored, and the number of black-to-white or white-to-black change points within the certain range is counted. Detect that there is more than a number. Here, the fact that the number of change points is equal to or more than a predetermined number, that is, the density of change points is equal to or more than a predetermined density means that an image such as a character exists up to the end of the document.

The detection outputs of the first and second detection means 32 and 33 are supplied to an edge detection means 35 via an OR circuit 34. The edge detection means 35 detects the edge position of the document based on the detection output supplied first among the detection outputs of the first and second detection means 32 and 33. Specifically, when a detection output indicating that the document area pixels have continued for a predetermined value or more is supplied from the first detection unit 32 first,
The first change point is detected as a boundary pixel between the outside document area and the document area, that is, edge positions X1 and X2 shown in FIG.
When a detection output indicating that the number of change points is equal to or more than a predetermined number is supplied from the detection means 33, the first change point is detected as the edge positions X1 and X2 shown in FIG. The size determining means 36 determines the width of the document 1 in the main scanning direction from the data of the edge positions X1 and X2 detected by the edge detecting means 35, and further determines the predetermined width of the document 1 from information supplied from a photo sensor (not shown). The document presence / absence information in the sub-scanning direction at the position is obtained, and the size of the document 1 is determined.

As described above, the second detecting means 33 is provided in addition to the first detecting means 32 which can accurately determine the size of a document for a document having no image at the end of the document area. Thus, when an image is present at the end of the document area, the edge position of the document can be detected after recognizing the presence of the image. As described above, the document size can be accurately determined even for a document in which an image is present up to the document end.

Next, the procedure of the document size detection process executed by the CPU 158 will be described with reference to the flowcharts of FIGS. Power on the device (O
N), the CPU 158 first moves the carriage on which the optical system is mounted to the document detection position, and starts supplying the CCD clock to the CCD solid-state imaging device 10 by activating the timing generation circuit 11 (step S1). ). Next, it is determined whether or not a start button (not shown) has been pressed before the angle sensor 22 is turned on (step S2). If the start button has not been pressed yet, the process waits until the angle sensor 22 is turned on (step S3).

When the angle sensor 22 is turned on, the CPU 15
8 turns on the exposure lamp 6 and stores 1 in the RAM (2) 155.
The image data for the line is stored (step S4), and waits until the platen open / close sensor 21 is turned on (step S4).
5). When the platen open / close sensor 21 is turned on, the RAM
(3) One line of image data is stored in 156 (step S6), then the exposure lamp 6 is turned off, and the RAM
(2) The respective storage contents of the 155 and the RAM (3) 156 are scanned (step S7). Then, it is determined whether or not a change point from the background color outside the document is detected (step S8), and this determination is repeated until it is determined in step S9 that scanning of all the pixels of one line has been completed. If the change point cannot be detected even after the scanning of all the pixels of one line is completed, the document edge position cannot be detected, and therefore the document size cannot be detected, so "document size cannot be detected". Is displayed (step S10), and the process of detecting the appropriate document size is terminated.

If a change point from the background color outside the document is detected in step S8, it is determined whether the pixels of the document area are continuous over a certain value (step S11). In step S12, it is determined whether or not the number of change points is equal to or greater than a predetermined number within a certain range (step S12). These two determinations are repeated until it is determined in step S9 that scanning of all pixels on one line has been completed. If it is determined that the document area pixels are continuous for a certain value or more or that the number of change points is a predetermined number or more within a certain range, the pixel position of the first change point is detected as the document edge position (step S13). The document width in the main scanning direction is obtained from the detected document edge position (step S14), and then the document size is obtained from the document width in the main scanning direction and the output of the photo sensor arranged in the sub-scanning direction (step S15). .

If it is determined in step S2 that the start button has been pressed before the angle sensor 22 has been turned on, the exposure lamp 6 is turned on (step S1).
6), image data for one line is stored in the RAM (2) 155 (step S17), and then the exposure lamp 6 is turned off.
F (step S18), and then the process proceeds to step S8 to execute the above-described processing.

[0025]

As described above, according to the present invention,
A first method for detecting that a predetermined number of continuous change points of scanning information
The addition to the detection means, providing the second detection means for detecting the density of the change point of the predetermined density or more, the first detection means
Is that the scanning information change point exists continuously more than a certain value
Is detected, the change point on the document end side is detected by the second detecting means.
Detects that the change point of the scanning information is higher than the predetermined density.
In this case, the change point on the document end side is detected as the boundary pixel between the document area and the outside area, that is, the edge position of the document, and the document size is determined based on this edge position. It is possible to accurately determine the size of an original such as a ladder chart, a ladder chart, and an original having an image up to the end of the original, such as a halftone original.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a digital copying machine to which the present invention is applied.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a functional block diagram for detecting a document size.

FIG. 4 is a conceptual diagram of a detection operation by a first detection unit.

FIG. 5 is a conceptual diagram of a detection operation by a second detection unit.

FIG. 6 is a flowchart (part 1) illustrating a processing procedure of document size detection.

FIG. 7 is a flowchart (part 2) illustrating a processing procedure of document size detection.

[Explanation of symbols]

1 manuscript 2 Platen glass 6 Exposure lamp 10 CCD solid-state imaging device 15 Digital signal processing circuit 16 Image forming unit 21 Platen open / close sensor 22 Angle sensor 32 First detecting means 33 Second detecting means 35 Edge detection means 36 Size determination means

Claims (1)

(57) [Claims] 1. An image reading apparatus for reading an image using a photoelectric conversion element that converts an optical image obtained by irradiating a document with light into an electric signal, wherein image data based on an output of the photoelectric conversion element is provided. storage means for storing, scans the stored contents of the storage means, and scanning a first detection means for detecting a change point of the scanning information, the stored contents of said storage means, the change point of the scanning information A second detecting means for detecting that the density is equal to or higher than a predetermined density;
When it is detected that the document is
The second detection means determines the change point of the scanning information.
When it is detected that the density is higher than the predetermined density, the document edge side
An image reading apparatus comprising: edge detection means for detecting a change point of each of them as an edge position of a document; and size determination means for determining a document size based on the edge position.