JP3538939B2 - Document size detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document size detecting device in an image reading device such as a digital copying machine or a facsimile.

[0002]

2. Description of the Related Art Generally, an original set in a copying machine or the like has a predetermined size standardized to A or B plate. For this reason, if the document size is specified, the size of the copy sheet can be automatically set. Therefore, many copy machines now include a document size detection device. In this type of document size detection device, when light is irradiated on a document surface, a plurality of photosensors that detect reflected light are arranged at positions corresponding to each document size, and the output state of each of these photosensors is changed. It was generally performed based on. However, arranging a photo sensor for each document size increases costs.
Therefore, in a digital copying machine that reads an image using a photoelectric conversion element such as a CCD image sensor,
2. Description of the Related Art There is known an apparatus which detects a document width in a main scanning direction using a CCD image sensor and detects a document size based on the detected document width and a photosensor output. Specifically, an image of a document set on a platen glass is optically read by an image reading unit having a CCD image sensor, and a threshold is set for the read one line of image data to set a threshold. Generally, the binarization is performed, and a change point of the density level after binarization is detected as the position of the document edge, and the document size is generally detected based on the detected output.

[0003]

However, if a change point of the density level is simply detected as a document edge, if a foreign matter (paper piece, dirt, etc.) of about several mm adheres to the platen glass, the density of the foreign matter is detected there. Since the level changes, a portion that is not originally a document edge (a portion to which a piece of paper, dirt, or the like is attached) is recognized as a document edge, and there is a risk that erroneous detection of the document size may occur. As a countermeasure , a boundary pixel between the original area and the outside area, that is, the position of the original end is detected by recognizing that the original area pixels exist to some extent continuously, and the original is determined based on the position of the original end. A method of detecting the size is also conceivable. That is, a reference pixel for detecting the document edge is set in the area outside the document, and the pixel value (density level) is detected every predetermined pixel from the reference pixel toward the document area. When the document area is “white” in “black”, the pixel closest to the reference pixel is recognized as the document edge when the pixel value of “white” is continuously detected for the specified number of times.

However, in this document size detection method, although a remarkable effect can be obtained for a relatively large foreign matter of about several mm, for example, a very small foreign matter (about 0.3 mm or less) which is difficult to visually confirm. If there is any foreign matter at the pixel value detection point, data that should be continuous should be detected as discontinuous, or data that should be discontinuous should be detected continuously, which could lead to false detection of the original size. There was a problem that occurred. Further, even when an isolated point that appears due to deterioration of the CCD image sensor exists at a pixel value detection point, the pixel value always depends on the density level of the isolated point. Was one of the factors that caused this.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to prevent a foreign object from adhering to a platen glass (original platen) and the appearance of an isolated point without being misled. An object of the present invention is to provide a document size detecting device capable of accurately detecting a size.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to achieve the above-mentioned object, and therefore a document size detecting device for detecting the size of a document set in an image reading unit for optically reading image information of the document. In the apparatus, reference pixel setting means for setting a reference pixel for detecting a document edge in a non-document area with respect to a pixel row of image data for a predetermined line read by the image reading unit, and the reference pixel setting means Pixel value detection means for detecting a value of a pixel every predetermined pixel from the set reference pixel toward the document area side; pixel extraction means for extracting a pixel having a density value different from the reference pixel by a predetermined number of consecutive pixels; recognizing document end recognition means as document end pixels close to the reference pixels among the pixels extracted by the extraction means, the position of the recognized document edge by the sheet edge recognition means Based on it has a configuration including a document size determination means for determining document size.

[0007]

[Action] In the document size detecting device of the present invention, the image reading reference pixels for document end detection for a pixel column of the predetermined image data for one line read by the unit
Then, the value of each pixel is detected every predetermined pixel from the reference pixel toward the document area. At this time, if a predetermined number of consecutive pixels having different density values from the reference pixel are extracted, a pixel close to the reference pixel among those pixels is a boundary pixel between the non-document area and the document area. For,
This is recognized as a document edge, and the size of the document is determined from the position of the document edge.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to, for example, a digital copying machine will be described below in detail with reference to the drawings. Note that the document size detection device according to the present invention includes:
The present invention is not limited to the application to a copying machine, but can be applied to all electronic devices having an image reading unit that optically reads image information of a document.

FIG. 1 is a schematic configuration diagram of a digital copying machine to which the present invention is applied. In FIG. 1, an analog image signal output from a CCD image sensor 1 is converted into digital data by an image data generation circuit 2 and then supplied to a correction / filter circuit 3 as image data. The correction / filter circuit 3 performs shading correction on the input image data, and performs a filtering process on the image data after the shading correction. The editing processing circuit 4 performs, for example, editing processing such as reduction or enlargement on the filtered image data. In this processing, a RAM is used as image data storage means.
5 is used. The image data that has been subjected to the predetermined editing processing is sent to the output interface circuit 6, and is supplied therefrom to the image forming unit 7 such as a printer.

The CPU 8 has a data / address bus (CP)
The above-mentioned circuits are controlled via a U bus 9, and a control program therefor is stored in a ROM 10. In various processing operations (for example, shading correction processing) of the CPU 8, the RAM 11 is used for temporarily storing data. The CPU 8 receives a motor drive signal via a motor driver circuit 13 for a carriage motor 12 of a carriage for driving an optical system, and receives a motor drive signal via a motor driver circuit for a transport motor serving as a drive source for a transport roller (not shown). In addition to supplying a motor drive signal, a normal document image reading process is performed, and a document size detection process set in an image reading unit described later is performed. This document size detection processing will be described later in detail.

FIG. 2 is a schematic configuration diagram of an image reading unit in a digital copying machine. As shown in the figure, a platen glass (document table) 31 on which the document P is placed is provided on the upper surface of the unit body 30, and the document P placed there is pressed from above by a platen cover 32. Is to be included. The platen cover 32 has a white document pressing surface on the lower surface thereof, and is attached to the unit main body 30 at one end side so as to be freely opened and closed at a pivot point.

On the other hand, below the platen glass 31, an exposure lamp 33 for irradiating the original P placed on the platen glass 31 with light, and a reflection lamp for reflecting the reflected light from the original P in a predetermined direction. An optical system including mirrors 34 and 35 and a CCD image sensor 1 that captures reflected light from the mirrors via an imaging lens 36 is provided. Among the components of such an optical system, the exposure lamp 33 and the reflection mirrors 34 and 35 are mounted on a carriage (not shown), and move the document surface optically with the carriage in the horizontal direction in the figure, that is, in the sub-scanning direction. It is configured to be able to scan. The CCD image sensor 1 employs a line sensor in which a large number of pixels are arranged in a straight line, and is electrically fixed in a direction orthogonal to the sub-scanning direction, that is, in the main scanning direction. It is configured so that scanning can be performed.

In addition to this, on the upper part of the apparatus main body 30,
A document feed mechanism 37 is mounted integrally with the platen cover 32. The document feed mechanism 37 includes a document tray 38 for setting a document P, and a document tray 3.
A conveyance roller 39 for feeding the originals P separated one by one from the sheet tray 8 along a predetermined conveyance path, and an original detection sensor (not shown) for detecting the leading end position of the originals P fed from the original tray 38. The document P fed from the document tray 38 is fed by the rotation of the transport roller 39.

In the digital copying machine having the above configuration, when the apparatus power is turned on (ON), the exposure lamp 33 and the reflection mirror 34 mounted on a carriage (not shown) are provided.
The optical system including 35 moves to the main scanning original reading position.
Then, the optical system optically scans the original P set on the platen glass 31, and the original image is captured by the CCD image sensor 1, where it is photoelectrically converted and converted into an analog image signal. The analog image signal is converted into digital data by the image data generation circuit 2, and the converted image data is processed by the correction / filter circuit 3 and the editing / processing circuit 4 such as shading correction, filtering processing, and reduction / enlargement. After that, the image data is supplied to the image forming unit 7 via the output interface circuit 6, where the image is formed on a copy sheet.

Next, a description will be given of a document size detection process performed prior to reading a document image. This document size detection process is performed by the CPU 8, and a functional block diagram for the detection process is shown in FIG. In FIG. 3, the RAM 5 stores one line of image data read by the image reading unit. The storage content stored in the RAM 5 is image data on the read line L defined along the main scanning direction X, as shown in FIG. Generally, a white document is used as a document. Therefore, the image reading operation at the time of document size detection is performed with the platen cover 32 being closed. Therefore, in the image data stored in the RAM 5, since the platen cover 32 is still open and there is no reflected light, the background color of the area outside the original is "black" and the original area is "white". Data.

The reference pixel setting means 40 sets a plurality of reference pixels for detecting a document edge in a region outside the document with respect to a pixel row of the image data stored in the RAM 5. A reference pixel setting unit 41 that specifies a position of a reference pixel with respect to a column, and a reference pixel output unit 42 that extracts a reference pixel specified by the reference pixel setting unit 41 and outputs the pixel value (density level). It is composed of The pixel value detecting means 43 is provided with the reference pixel setting means 4.
The value of the comparison pixel (pixel) is detected every predetermined pixel from the plurality of reference pixels set by 0 toward the document area side. A comparison pixel setting unit 44 that specifies the position of the comparison pixel as a base point, and a reference pixel output unit 45 that extracts the comparison pixel specified by the comparison pixel setting unit 44 and outputs the pixel value (density level) Be composed.

More specifically, first, the reference pixel setting means 40, as shown in FIGS.
A plurality of, in the example shown, five reference pixels (0 to 4)
No.) is designated by the reference pixel setting unit 41, and the pixel value of each reference pixel is detected by the reference pixel output unit 42.
This is supplied to the comparing means 46 described later. On the other hand, the pixel value detection unit 43 sets the comparison pixels (every 16 pixels → 8 pixels → 8 pixels... → 8 pixels) from the respective reference pixels (0 to 4) toward the document area side. 16
-20, 24-28, 32-36, 40-44, 48-
52, 56 to 60) are designated by the comparison pixel setting unit 44, and the pixel value of each comparison pixel is detected by the comparison pixel output unit 45, and is supplied to the comparison unit 46 described later.

The comparing means 46 compares the reference pixel supplied from the reference pixel setting means 40 with the comparison pixel supplied from the pixel value detecting means 43. Incidentally, in this embodiment, as shown in FIG. 4, one of the plurality of reference pixels (0 to 4) supplied from the reference pixel
16, 2 for the 0th reference pixel, for example,
Since a total of six comparison pixels such as Nos. 4, 32, 40, 48, and 56 are supplied from the pixel value detection unit 43, six comparison operations are performed for each reference pixel. Will be. That is, for the first reference pixel, 17, 25, 33, 41, 49, and 57 comparison pixels, and for the second comparison pixel, 18, 26, 34, and 4
No. 2, 50, and 58 comparative pixels, No. 19, 27, 35, 43, 51, and 59 comparative pixels for the third reference pixel;
20, 28, 36, 44, 5 for the fourth comparison pixel
The comparison pixels No. 2 and 60 are compared.

The pixel extracting means 47 extracts a pixel (comparative pixel) having a predetermined number of consecutive density values different from the reference pixel. Specifically, as shown in FIG. 4, when the plurality of reference pixels (No. 0 to No. 4) set by the reference pixel setting unit 40 are, for example, “black” data, the reference pixels (No. 0 to 4), the individual comparison pixels (16 to 4)
20, 24 to 28, 32 to 36, 40 to 44, 48 to 5
Pixels satisfying the condition that all the data are the “white” data are extracted. In the process of extracting pixels, if the above-described extraction conditions are not satisfied, the reference pixel setting means 40 changes the setting (position change) of the reference pixel each time. At 43 also, the setting of the comparison pixel is changed. By the way, in this embodiment, when the above extraction condition is not satisfied, the position of the reference pixel is shifted by one pixel toward the document area side, and the position of the comparison pixel is shifted by one pixel accordingly.

The document edge recognition means 48 recognizes a pixel closest to the reference pixel among the pixels extracted by the pixel extraction means 47 as a document edge. More specifically, referring to FIG. 4, pixels (16 to 20, 24 to 28, and 32) satisfying the above-described extraction conditions are set for a plurality of reference pixels (0 to 4) set by the reference pixel setting unit 40. ~ 36,
When pixels 40 to 44, 48 to 52, and 56 to 60 are extracted by the pixel extracting means 47, these pixels (16
-20, 24-28, 32-36, 40-44, 48-
52, 56 to 60), the reference pixel (for example,
The 16th pixel closer to the reference pixel (0th) among the pixels (16th to 20th) close to the 0th (0th) is recognized as the document end positions X1 and X2 shown in FIG. The document size discriminating means 49 obtains the document width in the main scanning direction from the document end positions X1 and X2 recognized by the document edge recognizing means 48, and obtains the document width in the sub-scanning direction from information supplied from a photo sensor (not shown). The document width is determined, and the document size is determined from the document width in both scanning directions.

As described above, in the document size detecting apparatus according to the present embodiment, when a pixel value having a predetermined number of different density values from the reference pixel is extracted when a pixel value is detected every predetermined pixel from a plurality of reference pixels. Only the pixel closest to the reference pixel among these pixels is recognized as the document edge, so for example, in FIG. Even if the data is “white”, which is the same as that of the document area, due to the attachment of a size of about three pixels), by setting a plurality of reference pixels as described above, Since there is always a pixel having the same "black" data as the area outside the document, the 16th pixel is not erroneously recognized as the document end as in the related art. Also, the appearance of an isolated point due to deterioration of the CCD image sensor 1 or the like causes
For example, in the pixel row shown in FIG. 4, the 32nd and 33rd pixels actually present in the document area (since the isolated point usually ranges from 1 to 2 pixels) are the same as those in the non-document area. black"
In the process of moving the reference pixel fetch position to the original area side even when the data of the reference pixel is moved, the empty area (3 pixels in this embodiment) is secured between the respective comparison pixels. Since the 32nd and 33rd pixels always exist, it is possible to accurately recognize the edge of the document by excluding the abnormal data due to the isolated point from the comparison pixels.

Next, the procedure of the document size detection process executed by the CPU 8 will be described with reference to the flowcharts of FIGS. First, in the document size detection processing, the image data of the read line L in the main scanning direction X shown in FIG. 8, that is, the image data of one line read by the image reading unit is stored in the RAM 5 (step S1). Next, from the image data stored in the RAM 5, the reference data (density data) of the nth pixel is taken in as a reference pixel (step S2), and n + 16 pixels separated from the reference pixel by 16 pixels toward the document area.
The reference data of the pixel is taken in as a comparison pixel (step S3). Then, the previously acquired reference data of the nth pixel and the reference data of the (n + 16) th pixel are compared (step S4). At this time, the reference data is n +
When the reference data of the 16th pixel is small, for example, when the reference data of the nth pixel is “black” and the reference data of the (n + 16) th pixel is “white”, the reference pixel is compared with the nth pixel. The process proceeds to step S5 on the assumption that the (n + 16) th pixel is changed in density.

In step S5, the reference data of the (n + 24) th pixel which is separated by 8 pixels from the (n + 16) th pixel is fetched, and then the criterion data of the nth pixel fetched as the reference pixel is compared with the reference data of the (n + 24) th pixel. In the same manner as above, it is determined whether or not the density of the reference data of the (n + 24) th pixel has changed with respect to the reference data of the nth pixel (step S6). Hereinafter, in steps S7 to S14,
In the same manner as described above, the n + 32th pixel, the n + 40th pixel, the n + 48th pixel, and the nth
The reference data of the + 56th pixel is sequentially taken in, and each time it is compared with the reference data of the nth pixel which is the reference pixel.

In such a process, six comparison pixels n + 16, n + 24, n + 32, n + 40, n + 4 set for n pixels which are reference pixels for document edge detection.
If any one of 8, n + 56 has the same or higher level of reference data as the reference data of the n-th pixel, the process proceeds to step S15 at that point, and the counter value is reset to zero there. Thereafter, the value of n is incremented by 1 (step S16). Then, in step S17 following this, in addition to whether or not a completion bit described later is set, whether or not the value of n is within a specified allowable range, that is, the pixel position specified by the value of n is determined. A determination is made as to whether or not the area is outside the edge position of the minimum document to be detected. If not, the process returns to step S2 to repeat the above processing.

On the other hand, also in step S14, if it is determined that the reference data of the (n + 56) th pixel has changed in density similarly to the reference data of the nth pixel, the reference data of the nth pixel (reference pixel) N + 16, n + 2
Assuming that all the reference data (comparative pixels) of the 4, n + 32, n + 40, n + 48, and n + 56 pixels have changed in density, the value of the counter is incremented by 1 (step S1).
8) Yes. This counter value is the number of times that a specified number (six in this embodiment) of comparison pixels having the same density level change form are extracted for one piece of reference data.

Next, a comparison is made as to whether or not the counter value has reached a prescribed number of times (5 in this embodiment), that is, a comparison of a prescribed number (6 in this embodiment) having the same change with respect to the reference data. It is determined whether the pixel has been extracted five times in a row (step S19). Here, if the counter value has not reached "5", the process directly proceeds to step S16,
Therefore, the value of n is incremented by one. In this case, since the completion bit has not been set, step S1 is executed.
7 returns to step S2, and repeats the above processing. On the other hand, if the counter value has reached "5" in step S19, a completion bit indicating that "pixel extraction has been completed" is set at that time (step S20). Note that the specified number of times “5” is a value that depends on the set number of reference pixels, and in setting the number, the characteristics and reading resolution of the CCD image sensor 1 and foreign matter (dirt) that may cause an erroneous document size detection are set. , Scratches, etc.).

When the pixels are extracted in this manner, the process proceeds to step S21 because the completion bit is set in the previous step S20, in which the reference pixel (n−n) is selected from the pixels (comparative pixels) extracted earlier. The pixel [(n-5) +16] closest to 5) is recognized as the document edge (step S21). Then, it was recognized as the document edge [(n-
5) +16 pixels], the document width in the main scanning direction is obtained (step S22). Finally, the document size is determined based on the document width in the main scanning direction and the output of the photo sensor arranged in the sub-scanning direction (step S22). S23).

[0028]

As described above , according to the document size detecting apparatus of the present invention, the appearance of isolated points due to the attachment of foreign matter to the platen glass (document table) and the deterioration of the CCD image sensor can be prevented. The document size can be detected .

[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 a schematic configuration diagram of an image reading unit in the embodiment.

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

FIG. 4 is a schematic diagram illustrating a processing operation of document size detection.

FIG. 5 is a flowchart of document size detection (part 1).
It is.

FIG. 6 is a flowchart of document size detection (part 2).
It is.

FIG. 7 is a flowchart of document size detection (part 3).
It is.

FIG. 8 is a basic conceptual diagram of document size detection.

[Explanation of symbols]

40 Reference pixel setting means 43 pixel value detecting means 47 Pixel extraction means 48 Original edge recognition means 49 Document Size Determination Means

Claims (2)

(57) [Claims] An original size detecting device for detecting the size of an original set in an image reading unit for optically reading image information of the original, wherein the image data of a predetermined one line read by the image reading unit is Reference pixel setting means for setting a reference pixel for document edge detection in a region outside the document with respect to the pixel row; and a pixel value at predetermined pixels from the reference pixel set by the reference pixel setting means toward the document area. Pixel value detecting means for detecting a pixel, a pixel extracting means for extracting a pixel having a predetermined number of consecutive density values different from the reference pixel, and a pixel close to the reference pixel among the pixels extracted by the pixel extracting means. Document edge recognition means for recognizing an edge, and document size determination means for determining a document size based on the position of the document edge recognized by the document edge recognition means. Document size detection apparatus characterized by comprising a. 2. The document size detecting device according to claim 1, wherein said reference pixel setting means sets a plurality of reference pixels in the area outside the document.