JP2002016765A - Image reader and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems of a conventional image forming device that cannot have correctly read an image and used a memory with a high capacity in cases when an original is placed on an original platen with an offset because an exclusive size sensor is employed for sensing the size of the original. SOLUTION: Original size information is generated by using image data from a read section reading an image of an original and image data are trimmed on the basis of the generated original size information.

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 for reading an image of a document and generating image data in pixel units, and an image forming apparatus having the image reading apparatus, and more particularly to a technique for detecting a document size.

[0002]

2. Description of the Related Art Generally, in a conventional image reading apparatus, the size of a read document is detected by a dedicated size detection sensor to obtain document size information used at the time of image formation.

The image reading apparatus has a function of reading a still original placed on a document table and a function of reading a moving original conveyed by an automatic document feeder. What is different from the original size detecting means in reading is used.

Next, a document size detecting means used for reading a still document will be described with reference to FIG.

FIG. 1 shows a basic configuration of a conventional document size detecting means. In FIG. 1A, a document G is placed on a document table 27. For example, if the size of the placed document G is A4 size according to the short side of the document table 27,
Equipped with size detection sensors S1a and S1b at two corners corresponding to one short side of the A4 size document, the size detection sensors S1a and S1b detect that the document is placed and detect the size of the document. I have. Similarly, the size detection sensors S2a and S2 are located at positions corresponding to the standard size of each document.
b ... A plurality of Sna and Snb are provided to detect various document sizes. As shown in FIG. 1B, for example, size detection sensors S1a and S1b are provided at corner positions of the document G so that the document size can be detected even when the document is placed on the basis of the center line of the document table. The document size is detected.

[0006]

As described above, in the conventional document size detecting means, the document size is detected by a dedicated size detecting sensor corresponding to each size.

However, when the original G is placed on the original platen 27, as shown in FIG. 2A, it is sufficient that the original G is properly placed at a position corresponding to the original size. As shown in ()), when the document is to be placed with its long side aligned with the left end of the document table, the document may be placed with a shift of the area D1. In this case, the size detection sensor S detects an end position shifted to the right by an area D1 from the end position of the prescribed document size. Therefore, the left area D1 is read and stored as image data even though there is no image.
Further, since the right area D2 is not in the fixed size area, there is a problem that an image in this area cannot be read.

When the original is placed on one corner as shown in FIG. 2C, the original is greatly shifted to the left corner in the figure, so that the image reading area is not larger than the size detection sensor S.
The size of the document, which is much larger than the end position of the document of the specified size, is detected, including the extra area D3. Therefore, a large amount of memory is used to read the entire screen of the document table. There is.

The erroneous determination of the document size or the document area as shown in FIGS. 2B and 2C is based on the assumption that the edge of the document detected by the size detection sensor S is shifted by a predetermined width. If it is within the width, it is determined that the document is a specified size.If it is outside the width, it is determined that the document is not the specified size. This is a problem caused by using the detection sensor.

It is basically impossible to solve the above-mentioned problem with the document size detecting means using a dedicated size detecting sensor as in the prior art.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problem in document size detection when reading a static document.

[0012]

The object of the present invention is achieved by the following invention.

1. A reading unit that reads an image of a document and generates image data in pixel units, a comparing unit that compares the image data from the reading unit with a threshold value for each pixel, a column of pixels, or a block of pixels, and a change in output of the comparing unit Document size information generating means for generating document size information based on point coordinates, and an image for cutting out document size image data from image data from the reading unit based on document size information from the document size information generating means An image reading apparatus comprising: area information generating means.

2. 2. The image reading apparatus according to claim 1, further comprising storage means for storing image data from the image area information generating means.

3. A reading unit that reads an image of a document and generates image data in pixel units, a comparing unit that compares the image data from the reading unit with a threshold value for each pixel, a column of pixels, or a block of pixels, and a change in output of the comparing unit Document size information generating means for generating document size information based on point coordinates,
Based on the document size information from the document size information generating means, based on image area information generating means for cutting out image data of the document size from the image data from the reading unit, and based on the image data from the image area information generating means. And an image forming apparatus for forming an image.

4. Storage means for storing image data from the image area information generating means, wherein the image forming means forms an image based on the image data from the image area information generating means or the storage means. 4. The image forming apparatus according to the above 3, wherein

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an image forming apparatus equipped with an image reading apparatus according to an embodiment of the present invention will be described.

FIG. 3 shows an image forming apparatus according to an embodiment of the present invention. In FIG. 3, in the document reading apparatus provided in the image forming apparatus, the automatic document feeder U is configured to be of a downward type. When the automatic document feeder U is raised, the document table 27 made of platen glass is opened. It can be used.

When reading a still original, the automatic original transport unit U
And lift the original G onto the original platen 27 (shown in FIG. 4).
Then, the optical system described later moves to read the original.

The original reading device 2 includes a light source 23a and a mirror 23.
b and the first mirror unit 23 including
There is a second mirror unit 24 provided with a mirror 24a and a mirror 24b that further reflect light from the mirror. At first, each of the mirror units 23 and 24 is stationary with the left end position in the figure as a home position. The document image is reflected by the operation described below, and is imaged on a line CCD (imaging element) 26 corresponding to the short side of the document table via the imaging lens 25 to read the image.

When the original G is placed on the original table 27,
The first mirror unit 23 below the platen 27 and the second
The mirror unit 24 moves from the home position in the direction of the arrow Y in the figure to satisfy certain optical conditions, scans the width, sequentially forms an image on the line CCD 26, and reads the image of the original. The main scanning is performed electronically by the line CCD 26.

Next, when the automatic document feeder U is set on the document table 27, the document is placed on the document feeder plate 11 of the automatic document feeder U with the image surface facing upward, and
The document G is sent out one sheet at a time by the operation of 2, after the document G is temporarily stopped by the registration roller 13 and the leading end is adjusted,
Sub-scanning is performed while the document G is conveyed to the conveyance drum 14 and the document G rotates integrally and counterclockwise along the peripheral surface of the conveyance drum 14, and the document surface is read by the document reading device 2. That is, in the document reading device 2, the first mirror unit 23 is stopped at the home position immediately below the transport drum 14, and the second mirror unit 24
Is also stationary at a nearby position and sequentially illuminates the passing document, and the reflected light is further reflected by a second mirror unit 24 including a mirror 24a and a mirror 24b arranged so as to be orthogonal to the moving direction of the document, An image is formed on the line CCD 26 via the image forming lens 25 and is converted into an electric signal. Thereafter, the sheet is branched from the drum surface at a position substantially halfway around and discharged to the sheet discharge table 15. The automatic document transport unit U has a transport function for double-sided scanning in addition to the transport function for single-sided scanning, but this operation is omitted.

Next, detection of a document size according to the embodiment of the present invention will be described. In the present embodiment,
The detection of the document size and the reading of the image of the document G are performed with the document table 27 opened.

In this example, each pixel of the line CCD 26 corresponds to the short side of the document table via an optical system. For example, if a document of up to A3 size can be placed (read), a short size of A3 size is set. In a configuration in which the side is read at 400 dpi (the number of pixels per 25.4 mm), a line CCD of about 47000 pixels is used as the line CCD 26.

FIG. 4 is an overall view showing a state where a document is placed on the document table 27. FIG. 5 is an enlarged view of a corner portion surrounded by a dotted line in FIG.

As shown in FIG. 4, main scanning is performed in the direction of the short side (long side of the document) of the document table 27 from left to right in the figure.
In the direction of the long side of the document table 27 (short side of the document), sub-scanning is performed from top to bottom in the figure. As already mentioned, the platen 27
In the short side direction, each pixel of the line CCD 26 corresponds, and therefore, it can be considered that the document table 27 forms coordinates by these pixels. Therefore, by assigning an address number to each of these pixels, each position on the document table 27 can be determined by this address number.

FIG. 5 is a diagram showing the addresses of the document table 27 in an enlarged manner. As shown in FIG. 5, for example, the pixel at the upper left corner is [0, 0]. Here, the numbers on the left side represent the addresses (coordinates) of the main scanning, and the numbers on the right side represent the addresses (coordinates) of the sub-scanning. Subsequently, one line corresponding to the line CCD 26 is moved from left to right at [1, 0], [2, 0],.
0] ... [x, 0], and the second column is similarly assigned [0,1], [1,1] .. [h, 1] ... [x,
1], and addresses are assigned to [x, y] corresponding to the entire surface of the document table. As the scanning is performed, the address number is counted separately for the main scanning and the sub-scanning, and the image density (pixel value) is calculated for each pixel at each address.
Is compared with a preset threshold density. The image area of the document can be detected based on the comparison result. That is, in this example, the main scanning proceeds, the start of the image area is detected at the address [h, k], and then the address [h + n, k] is detected.
The comparison with the threshold value is performed for each pixel until it is detected that the pixel is a document area. Then, the scanning is continued, and the document area from the address [h, k + m] to [h + n, k + m] is detected as described above. As the scanning progresses, the document size is calculated and determined from the count value of the address and the detection of the document area, and at the same time, the image data of the document is read.

FIG. 6 is a block diagram of an embodiment of the present invention. The process of size detection will be described with reference to FIG.

Including the line CCD 26, the line CCD 2
The image data from the reading unit 90 which converts the output of the digital conversion unit 6 into digital data to generate image data is input one pixel at a time to a data comparison circuit 91 as comparison means.
To enter. A main scanning synchronization pulse generated every time the main scanning progresses one pixel at a time is input to the data comparison circuit 91 and the main scanning counter circuit 92. Similarly, a sub-scanning pulse generated for each sub-scan (one line) is supplied to a data comparison circuit 91.
Is input to the sub-scanning counter circuit 93. Here, the transmission path indicated by a thick chain line in the figure shows a bus form, and the main scanning synchronization pulse and the sub scanning synchronization pulse are transmitted independently.

Then, the data comparing circuit 91 compares the image data with the threshold value for each pixel, and determines whether the image data is black or white. The main scanning counter circuit 92 counts as the main scanning advances by one pixel. Similarly, the sub-scanning counter circuit 93 counts as the sub-scanning proceeds line by line. While the output of the data comparison circuit 91 is white, the counting of each synchronization pulse is continued by both counter circuits 92 and 93, but when the result of the data comparison circuit 91 is black, the counting of the synchronization pulses is continued by the two counter circuits 92 and 93. Each counted value is transferred to the image effective area point storage circuit 95 and stored. Similarly, while the output of the data comparison circuit 91 indicates black, the main scanning counter circuit 92 counts the number of synchronization pulses, and stores the point at which the color changed from black to white in the image effective area point storage circuit 95. Further, the count values are transferred to an arithmetic function circuit 96. The arithmetic function circuit 96 compares and compares the count values with the image data to calculate and store image area information which is a basic document size. Then, the image area information based on the calculation result and a preset, for example, A
4 and B4, etc., are input to an arbitrary original size storage circuit 94, and the arbitrary original size storage circuit 94
The document size is determined and stored.

As described above, based on the count values of the data comparison circuit 91, the main scanning counter circuit 92, and the sub-scanning counter circuit 93, the image effective area point storage circuit 95, the arithmetic function circuit 96, and the arbitrary document size storage Document size information is created by the circuit 94, and these constitute document size information generating means.

The original size information, the main scanning synchronization pulse, the sub-scanning synchronization pulse, and the image data are input to an image area information generation circuit 97. Image area information generation circuit 97
Scans the image data from the reading unit 90 in accordance with the document size information to form and output image data corresponding to the document size. The image area information generation circuit 97 outputs a synchronization pulse in the main scanning direction corresponding to the document size information, that is, a horizontal valid signal, and a synchronization pulse in the sub-scanning direction, that is, a vertical synchronization signal.

In the above-described example, the data comparison circuit 91 compares the threshold value with the image data for each pixel. However, instead of each pixel, the data comparison circuit 91 applies a line (line in the main scanning direction).
It is configured to detect the coordinates of the edge of the document G by comparing the average value of the pixel values of the upper plurality of pixels with a threshold value or comparing the average value of the pixel values of the block including the plurality of pixels with the threshold value. It is also possible.

The image data read in this way is usually processed and temporarily stored in an image memory (not shown) as storage means, read again and used for image formation.

As means for forming an image on a recording sheet of a size corresponding to the size of the original based on the image data stored in the image area information generating circuit 97 or the image memory, for example, an image using an electrophotographic process is used. Forming means is used.

In FIG. 3 showing the image forming means 3, a laser beam modulated in accordance with image data from a laser emitter of the image writing section 33 based on the image data mainly drives the photosensitive drum 31 by rotating the polygon mirror. Scan and expose. A main scanning exposure in the axial direction of the photoconductor drum 31 and a sub-scanning by rotation of the photoconductor drum 31 are performed on the photoconductor drum 31 to which the charging potential has been previously applied by the charger 32, and the photoconductor drum 31 is subjected to image data. An electrostatic latent image is formed. The electrostatic latent image is reversely developed by a developer in a developing device 40 to form a toner image. At the same time, the recording paper is fed from the manual paper feed unit 19 as the recording paper supply means or the paper feed tray 7 that stores the recording paper. The paper feed tray 7 has, for example, three stages of 7A, 7B, and 7C, and each of the paper feed rollers 51.
A, 51B, or 51C operates to convey the recording paper, and feed the recording paper to the conveyance rollers 55 and 56 and the timing roller 39 so that the recording paper is transferred to the photosensitive drum 31 in synchronization with the toner image on the photosensitive drum 31. Feed paper. The toner image on the photosensitive drum 31 is transferred to a recording paper side by applying a voltage of an opposite polarity by a transfer unit 35 and transferred to the recording paper side. The fixing roller 38 is separated from the fixing roller 31, is conveyed to a fixing device 38, and is fixed by fusing and fixing the toner by pressurizing and heating of a pair of heat rollers, discharged from a fixing discharge roller 81 of a discharge section 8 and discharged to a discharge tray 84. An image is formed based on the image data.

On the other hand, the photosensitive drum 31 from which the recording paper is separated
After the residual potential is removed, the residual toner is removed and cleaned by the cleaning device 37, so that the next image forming process can be executed.

[0038]

According to the first or third aspect of the present invention, even if the position or angle of the original placed on the original plate is shifted from the regular position, the original size is accurately detected and the detected original is detected. Since the image data is trimmed to the size, the detection of the correct document size is always performed, and the appropriate image data without excess and deficiency is created, so that the image memory can be used effectively. Further, since there is no need to provide a dedicated size detection sensor for detecting the development size, a highly reliable original size can be realized at low cost.

According to the second or fourth aspect of the present invention, since the storage means can be used effectively, a memory having a relatively small capacity can be used as the storage means for the image data, and the cost can be reduced. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a conventional document size detecting unit.

FIG. 2 is a diagram illustrating the influence of size detection on a document table by a document position on the document table.

FIG. 3 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 4 is an overall view showing a state where a document is placed on a document table.

FIG. 5 is a partially enlarged view of FIG. 4;

FIG. 6 is a block diagram of an embodiment of the present invention.

[Explanation of symbols]

 2 Document Reading Device 3 Image Forming Means 27 Document Table 90 Reading Unit 91 Data Comparison Circuit 92 Main Scanning Counter Circuit 93 Sub Scanning Counter Circuit 94 Arbitrary Document Size Storage Circuit 95 Image Effective Area Point Storage Circuit 96 Arithmetic Function Circuit 97 Image Area Information Generation Circuit G Original U Automatic Document Feeder

Claims (4)

[Claims] A reading unit that reads an image of a document and generates image data in pixel units; a comparing unit that compares the image data from the reading unit with a threshold value for each pixel, row of pixels, or block of pixels; Document size information generating means for generating document size information based on the coordinates of the change point of the output of the means; and document size information from image data from the reading unit based on document size information from the document size information generating means. An image reading apparatus, comprising: image area information generating means for cutting out image data. 2. The image reading apparatus according to claim 1, further comprising storage means for storing image data from said image area information generating means. 3. A reading unit for reading an image of a document and generating image data in pixel units, a comparing unit for comparing the image data from the reading unit with a threshold value for each pixel, row of pixels or block of pixels. Document size information generating means for generating document size information based on the coordinates of the change point of the output of the means, based on the document size information from the document size information generating means, a document size image from the image data from the reading unit. Image area information generating means for cutting out data, based on image data from the image area information generating means,
An image forming apparatus comprising an image forming means for forming an image. 4. A storage device for storing image data from the image area information generating means, wherein the image forming means comprises:
The image forming apparatus according to claim 3, wherein an image is formed based on image data from the image area information generation unit or the storage unit.