JP2007266981A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus for achieving sophisticated alignment without using any adjustment tools, such as a test chart, by arranging a plurality of image sensors zigzag and overlappingly arranging the read ranges of respective adjacent image sensors in a main scan direction, and by using an adjustment mechanism required for insuring characteristics as a scanner when adjusting a read position. <P>SOLUTION: In the apparatus, the plurality of image sensors CIS1-CIS3 are arranged zigzag, and original read ranges DRR1-DRR3 of respective adjacent image sensors are overlappingly arranged in the main scan direction. In this case, a pixel OPB for dark current correction is provided outside the original read ranges DRR1-DRR3 of the image sensors CIS1-CIS3 to detect the positions of respective image sensors CIS1-CIS3, and the image signal of the pixel OPB is utilized for detection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a document movement type image reading apparatus such as a scanner, a copying machine, a facsimile machine, and an MFP having a plurality of image sensors to cope with a large format paper.

2. Description of the Related Art Conventionally, it is known that an image reading apparatus using a large format paper in a scanner, a copier, a facsimile machine, an MFP, or the like is a document moving type using a contact image sensor (CIS).
In addition, when adjusting the reading position of each adjacent CIS in the main scanning direction, the same applicant reads two lines parallel to each sub-scanning direction across the CIS joint on the test chart (original) in the original reading range. A technique is disclosed in which the distance between each two lines on a read image is matched with a desired value by changing the range.

If an attempt is made to read large format paper with the optical system moving means, the document table becomes large, and the carriage for moving the optical system also becomes large, which is not realistic.
In addition, a contact image sensor (CIS) of an image reading apparatus for large format paper needs to have a length in the main scanning direction that is at least equal to or larger than the document width.
For example, a CIS length of 841 mm or more is required to read an A0 size document. In this case, it is technically difficult to produce the CIS with one chip, and the cost increases.

Therefore, a process of arranging a plurality of small image sensors in the main scanning direction, forming an image of light rays from the scanning of the original on each image sensor, and electrically connecting the image signals read by these image sensors. In general, image information corresponding to the entire scanning line is obtained.
In the configuration in which a plurality of image sensors are arranged in this way, it is necessary to partially overlap the reading areas of adjacent image sensors so that there is no seam in the image at the boundary between the image sensors.
By partially overlapping the reading regions of adjacent image sensors in this way and electrically connecting the image signals read at the overlapping portions, an image without deviation can be obtained.

However, when the image signal cannot be read in the overlapping reading area of the image sensor (when there is no character or image in the overlapping reading area of the image sensor), the image signal cannot be electrically connected. .
In view of the above, there is a method of obtaining an image having no deviation using a test chart (document) in the adjustment of the reading position of adjacent image sensors in the main scanning direction as in the prior art disclosed by the present applicant.

However, when adjusting the reading position of adjacent image sensors in the main scanning direction using the test chart in this way, due to variations in conveyance speed, skew, test chart waviness, etc. during test chart conveyance, dirt, etc. An error will occur.
In addition, it is necessary to hold the test chart for maintenance, and it is difficult to automate the adjustment because of the insertion of the test chart. There is a problem that the original must be read in a state in which the document has been printed.

  Accordingly, an object of the present invention is to adjust the reading position by arranging a plurality of image sensors in a staggered manner and overlapping the reading ranges of adjacent image sensors in the main scanning direction in consideration of the above situation. In addition, an object of the present invention is to provide an image reading apparatus that realizes high-level alignment without using an adjustment jig such as a test chart by using an adjustment mechanism necessary for guaranteeing characteristics as a scanner.

In order to solve the above-described problem, the invention according to claim 1 is an image in which a plurality of image sensors are arranged in a staggered manner, and reading ranges of adjacent image sensors are overlapped in the main scanning direction. In the reading device, in order to detect the position of each of the image sensors, a dark current correcting pixel is provided outside the document reading range of the image sensor.
The invention according to claim 2 is characterized in that the dark current correcting pixels are constituted by a plurality of continuous pixels.

According to a third aspect of the present invention, there is provided the image reading device according to the first or second aspect, wherein black shading is performed with black correction data of the pixel region for dark current correction.
The invention according to claim 4 comprises storage means for storing the output value of the light receiving element outside the document reading range, and comparison means for comparing the stored output value with the current output value, The image reading apparatus according to any one of claims 1 to 3, wherein fluctuations in the light amount of the light source are detected by comparing output values of the light receiving elements.

Further, the invention according to claim 5 is provided with a light quantity control means capable of controlling the light quantity of the light source, and the light quantity control means determines the light quantity of the light source based on the detection result of the fluctuation of the light quantity of the light source. Control is performed so as to approach the light amount of the initial value.
Further, the invention described in claim 6 is characterized by comprising display means for displaying an abnormality of the light source based on a detection result of fluctuations in the light amount of the light source.

  According to the present invention, the position of the adjacent image sensor is determined using the output signal of the dark current correction pixel (optical black pixel, OPB (optical black)) provided outside the document reading range of the image sensor. Since detection and position adjustment can be performed, advanced alignment can be performed without using an adjustment jig such as a test chart in the prior art.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an image reading apparatus according to the present invention. FIG. 2 is a top view showing an outline of the mechanism of the image reading apparatus of FIG.
The image reading apparatus A in FIGS. 1 and 2 will be described using an example in which a CIS (contact image sensor) is used as an image sensor. In this embodiment, three contact image sensors CIS1, CIS2, and CIS3 are arranged in a staggered manner.

The operation of the image reading apparatus will be described with reference to FIG. The document 7 is inserted into the conveyance roller 4 from the left side of FIG. When the document insertion sensor 5 detects the document 7, the transport roller 4 and the transport roller 6 are rotated by a transport motor (not shown), and light sources for document illumination (not shown) in the contact image sensors CIS 1, CIS 2, and CIS 3 are turned on. To do.
Thereafter, the registration sensor 8 detects the leading edge of the document 7 and sequentially recognizes the position of the document 7 in the conveyance path. The image (lower surface) of the document 7 is read by the contact image sensor CIS2 and then read by the contact image sensors CIS1 and CIS3.

The read signal of the contact image sensor CIS2 is delayed by the time required for sub-scanning between the contact image sensors CIS2 and CIS1 (distance L between the read position of CIS2 and the read position of CIS1), and the read signal of the contact image sensor CIS3 is Delayed by the time required for sub-scanning between the CIS2 (distance L between the reading position of CIS2 and the reading position of CIS3), the signals of the contact image sensors CIS1 to CIS3 are combined to obtain a reading signal that is made into one line.
The image of the document 7 is sequentially read from the left to the right in the figure, and is discharged through the conveyance roller 6. FIG. 1 shows a reading back member 9 and a contact glass 10 described later.

In FIG. 2 (when the operation is viewed from the top), the document 7 is conveyed from the upper side to the lower side in FIG. The effective reading ranges ERR1 to ERR3 of the contact image sensors CIS1 to CIS3 are arranged so as to overlap with the effective reading ranges ERR1 to ERR3 of the adjacent contact image sensors CIS (CIS1 and CIS2, CIS2 and CIS3).
The document reading ranges DRR1 to DRR3 of the contact image sensors CIS1 to CIS3 have adjustment reading ranges W1 and W2 for obtaining image signals used at each time point, and the adjustment reading ranges W1 and W2 are in the main scanning direction. And can be arbitrarily set independently.

According to the present invention, each contact image sensor CIS1 is detected by an image signal of a dark current correcting pixel (optical black pixel, hereinafter referred to as OPB (optical black)) provided outside the document reading range DRR1 of the contact image sensor (CIS). A feature of detecting the position of CIS3 will be described with reference to FIG.
Since each of the contact image sensors CIS1 to CIS3 has an OPB area, the output value of the output signal of the CIS made into one line is small only in the OPB area as shown in FIG.
That is, as described above, the read signal of the contact image sensor CIS2 is delayed by the time required for sub-scanning between the contact image sensors CIS2 and CIS1, and the read signal of the contact image sensor CIS3 is sub-scanned between the contact image sensors CIS3 and CIS2. The signals of the contact image sensors CIS <b> 1 to CIS <b> 3 are synthesized.

The position information W1 and W2 of the adjacent CIS can be detected from the pixel information of the output value, and the position of the adjacent CIS can be adjusted using the position information W1 and W2.
When a CIS having no OPB area or a CIS having only one side of the OPB area is used, the OPB areas must be created at both ends within the effective reading range ERR outside the CIS original reading range DRR.
The number of pixels of OPB can be composed of several consecutive pixels. Thereby, by increasing the number of pixels of OPB, the output value of the OPB area can be easily understood, and the position information W1 and W2 of the adjacent CIS with higher accuracy can be detected and adjusted.

Black shading is performed with black correction data in the OPB area. A method for performing black shading using black data in the OPB area will be described. Since the image signal read by the CIS is an output signal including a black level, the black level is removed from the image signal when image processing is performed.
In the case of CIS, the black level of all pixels (for one line) in the effective reading range ERR is stored in a memory (not shown) with the light source turned off, and the black level is removed for each line. .

In this method, since black level data cannot be collected during job operation, black level data collected immediately before the job operation is used. For this reason, optimal black shading cannot be performed, and a memory for one line is required.
However, in the method of removing the black level using the black data in the OPB area, the black data can be sampled for each line and black shading can be performed. Further, since black data does not require the black level of all pixels (for one line), the capacity of the memory can be reduced.

FIG. 3 is a schematic diagram illustrating detection of fluctuations in the light amount of the light source. The storage means (not shown) for storing the output value of the light receiving element (not shown) within the effective reading range ERR outside the document reading range DRR of the CIS (contact image sensor CIS1 in FIG. 3) is an image. In preparation for the reading device or the image forming apparatus, the output value of the light receiving element within the effective reading range ERR outside the CIS document reading range DRR is held and placed.
For example, the output value (initial value) of the light receiving element in the effective reading range ERR outside the CIS document reading range DRR when the image reading apparatus is installed at the user's site is stored in the memory, and this light receiving element Is compared with the output value of the light receiving element in the effective reading range ERR outside the CIS document reading range DRR collected during the job operation by a comparator (not shown). Can be detected.

As shown in FIG. 3 (viewed from the side), there is a reading back member 9 on the CIS, and this reading back member 9 is used as a reference white plate so as to serve as a white level reference, and is used for shading correction. Yes.
The reading output value of the reading back member 9 at the light receiving element is stored in the memory so that the reading back member 9 is also applied to the effective reading range ERR outside the document reading range DRR of the CIS.
By using the effective reading range ERR that is outside the CIS document reading range DRR, it is possible to prevent a decrease in the output value of the light receiving element due to contamination of the contact glass 10 due to passing of the document or contamination of the reading back member 9.

According to the present invention, the light amount control means (not shown) capable of controlling the light amount of the light source based on the detection result of the fluctuation of the light amount of the light source (not shown) is provided, and can be controlled to an appropriate light amount. . Therefore, for example, when an LED is used as the light source, the light amount of the LED is proportional to the current, so that the light amount can be easily adjusted.
Therefore, the CIS document reading range when the image reading device is installed at the user's site according to the detection result of the fluctuation of the light amount of the light source with a certain margin in the design of the light amount of the initial LED. For example, the current is changed by a variable resistor (not shown) so that the output value (initial value) of the light receiving element within the effective reading range ERR outside the DRR is obtained. It is possible to control the amount of light.

According to the present invention, even if the above-described operation is performed, the output value (initial value) of the light receiving element within the effective reading range ERR outside the CIS document reading range DRR when the image reading apparatus is installed at the user's destination. When it is not possible, an abnormality of the system is communicated to the user or service person by a display means (not shown) such as an operation unit of the image reading apparatus or a monitor.
At this time, since this abnormality is not a decrease in the amount of light but may be affected by contamination of the contact glass 10 or the reading back member 9, an instruction to clean the contact glass 10 or the reading back member 9 is displayed first. To.

After cleaning according to the cleaning instruction, the current is again set to the output value (initial value) of the light receiving element within the effective reading range ERR outside the CIS document reading range DRR when the image reading device is installed at the user's site. Fluctuate.
However, even if this does not reach the output value (initial value) of the light receiving element within the effective reading range ERR that is outside the CIS document reading range DRR when the image reading apparatus is installed at the user's end, an instruction to replace the light source is given. Is displayed so that optimum image reading can be performed. Thus, the optimum image reading can be performed by determining the replacement of the light source.

1 is a schematic diagram showing an image reading apparatus according to the present invention. It is a top view which shows the mechanism outline | summary of the image reading apparatus of FIG. It is the schematic explaining the detection of the fluctuation | variation of the light quantity of a light source.

Explanation of symbols

A Image reading device 4 Conveying roller 6 Conveying roller 7 Document
9 Reading back member 10 Contact glass CIS1 Contact image sensor
CIS2 contact image sensor CIS3 contact image sensor DRR1 CIS1 original reading range ERR1 CIS1 effective reading range DRR2 CIS2 original reading range ERR2 CIS2 effective reading range DRR3 CIS3 original reading range ERR3 CIS3 effective reading range L CIS2 reading position and Distance OPB from CIS1 and CIS3 reading position Pixel for dark current correction (optical black pixel)
W1 CIS position information (adjustment reading range)
W2 CIS position information (adjustment reading range)

Claims (6)

  In an image reading apparatus in which a plurality of image sensors are arranged in a staggered manner and the reading ranges of adjacent image sensors are arranged overlapping in the main scanning direction, the image sensor is used to detect the position of each image sensor. An image reading apparatus comprising a dark current correcting pixel outside a document reading range of a sensor.   The image reading apparatus according to claim 1, wherein the dark current correcting pixels include a plurality of continuous pixels.   3. The image reading apparatus according to claim 1, wherein black shading is performed using black correction data of the dark current correction pixel region.   A storage means for storing the output value of the light receiving element outside the original reading range and a comparison means for comparing the stored output value with the current output value, and comparing the output value of the light receiving element, The image reading apparatus according to claim 1, wherein fluctuations in the amount of light from the light source are detected.   A light amount control unit capable of controlling a light amount of the light source, and the light amount control unit controls the light amount of the light source to be close to an initial light amount based on a detection result of a variation in the light amount of the light source; The image reading apparatus according to claim 4.   6. The image reading apparatus according to claim 5, further comprising display means for displaying an abnormality of the light source based on a detection result of fluctuations in the light amount of the light source.

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