JP2003037717A - Image reader and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that performs proper shading (hereinafter abbreviated 'SH'), even if the luminous quantity of a light source fluctuates, while reading of a reference white board data is omitted, in the case of consecutively reading originals by means of an ADF(automatic document feeder). SOLUTION: A second reference white board is placed at the outside of an original area at an ADF reading position. The image reader reads a first reference white board before reading an original and a FIFO 205 stores obtained white reference data as SH data by number of main scanning pixels. The image reader reads the second white board at reading of the first original, gives the obtained white reference data to a peak detection circuit (1) 206, which detects and stores a peak level D2sh- 1 of to specified pixels. When reading second and succeeding original, the image reader generates no SH data, reads only the second white board, gives obtained data to a peak detection circuit (2) 207, which detects and stores a peak value D2sh- n. The image reader corrects the SH data used for the second and succeeding originals by a ratio of D2sh- n/D 2sh- 1, to prevent a read image from being deteriorating, thereby preventing the throughput of ADF reading from decreasing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital copying machine,
More specifically, the present invention relates to an image reading device equipped in a scanner device, a facsimile device, and the like. More specifically, in a device capable of reading in two modes: fixed document reading (book reading) and conveyance document reading (ADF reading), both modes can be used. Second position on the ADF reading position (fixed position) outside the commonly used standard white plate for shading correction.
The present invention relates to an image reading apparatus which is provided with the reference white plate and corrects shading data by the read data of the second reference white board, and an image forming apparatus including the image reading apparatus.

[0002]

2. Description of the Related Art Generally, in a digital image reading device equipped in a digital copying machine, a scanner device, etc., a C
The CD line image sensor has uniform reflection characteristics due to factors such as uneven sensitivity of each pixel, variation in transmitted light amount in the lens, uneven illumination of the illumination / optical system, light amount distribution in the main scanning direction, and deterioration. The output from the light receiving element corresponding to each pixel when the reference plate is read does not always have a constant and uniform value. Shading correction is known as a means for correcting these. Shading correction is performed by illuminating a reference white plate (see 21 in FIG. 1) arranged near the document placing portion prior to the actual document reading process, reading the reflected light, and correcting the shading of each pixel. The white level reference data. Shading correction data is generated based on the acquired white level reference data, and correction calculation is performed on the document image data read by this correction data to normalize the read data.

By the way, in the image reading apparatus, the reading optical system (mirror, lamp, etc.) is moved in the sub-scanning direction (CCD).
Of the fixed document reading mode (hereinafter, referred to as “fixed document reading mode”), and the automatic document feeder (AD).
2. Description of the Related Art Conventionally, there is known an apparatus having a device capable of carrying a document by F) and reading a moving document (hereinafter referred to as “ADF reading mode”). When shading correction is performed in an image reading apparatus equipped with such two modes of fixed document reading and ADF reading, correction data obtained from a common reference white board is usually used for two modes. The method has been adopted. Therefore, in ADF scanning,
The reading optical system that is reading the document at the fixed position must be moved to the reference white plate (which is placed on the moving path when reading the fixed document) in order to obtain the shading data. According to the normally performed operation of reading the reference white plate every time the document is read, this movement time causes a decrease in the throughput of the apparatus (the number of sheets that can be read in a unit time). Therefore, when the originals are continuously fed, the reference white plate is not read every time the originals are read, and the data used so far is continuously used so that the original advantage of the ADF reading is not impaired. The method of doing is also adopted.

[0004]

However, since the illuminance and the light amount distribution in the main scanning direction fluctuate due to changes in the temperature of the tube surface of the light source after the light source is started to be lit, the original is continuously read as in the ADF reading. When reading, for example, 1
In the original read data of the first sheet and the original read data of the 99th sheet, the influence of the light source variation appears and a difference occurs in the original read data level. Therefore, when the shading processing is performed on the 99th document read data with the shading correction data generated when the first sheet is read, a problem occurs in that the read density is different. The present invention has been made in view of the above-mentioned problems of the prior art in an image reading apparatus having equipment corresponding to two modes of fixed document reading and ADF reading, and an object thereof is to perform shading in the ADF reading mode. If the reading of the reference whiteboard data for use is omitted, even if there is a change in the light source during that time, a means for enabling appropriate shading correction according to the change is provided, thereby reducing the throughput in ADF reading. Another object of the present invention is to provide an image reading apparatus capable of outputting a read image without deterioration and an image forming apparatus including the image reading apparatus.

[0005]

According to a first aspect of the present invention, there is provided a reading optical system, a document conveying unit, and a moving unit of the reading optical system, the reading optical system is moved, and a fixed original is read. An image reading apparatus in which a reading optical system is fixed and which is capable of operating in both modes of reading an original while being conveyed by an original conveying unit, and in which a first reference white plate is provided at a moving position of the reading optical system,
A second reference white plate is provided at the fixed position of the reading optical system, means for performing shading correction based on the read data of the first reference white plate, and shading data correction based on the read data of the second reference white plate. An image reading apparatus comprising means.

According to a second aspect of the invention, in the image reading apparatus according to the first aspect, the means for acquiring the read data of the first reference whiteboard and the second reference whiteboard is a common image sensor. It is what

According to a third aspect of the invention, in the image reading apparatus according to the first or second aspect, the read data of the second reference white board used for correcting the shading data is an average value of the read data of the specific area. It is characterized by that.

According to a fourth aspect of the invention, in the image reading apparatus according to any one of the first to third aspects, the means for correcting the shading data is a second correction value when the shading data is created and when the shading correction is performed. It is characterized in that the ratio of the read data values of the reference white board is used.

According to a fifth aspect of the invention, in the image reading apparatus according to any one of the first to fourth aspects, the means for correcting the shading data performs the correction between the continuously conveyed originals. It is characterized by doing so.

According to a sixth aspect of the invention, in the image reading apparatus according to any one of the first to fifth aspects,
The reference white plate is placed outside the passage area of the document to be conveyed.

According to a seventh aspect of the present invention, there is provided an image forming apparatus including the image reading apparatus according to any one of the first to sixth aspects and a means for forming an image based on image data. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The image reading apparatus of the present invention will be described based on the following embodiments shown with accompanying drawings.
The embodiment described below can also be applied as a document image input unit in an image forming apparatus such as a digital copying machine. FIG. 1 is a schematic diagram showing the overall configuration of an image reading apparatus equipped with an ADF according to an embodiment of the present invention. The apparatus of the embodiment shown in FIG. 1 operates in two reading modes: fixed original reading (book reading) and ADF reading (sheet through reading). First, the configuration and operation of the fixed original reading mode will be described.
Place the original on the platen glass 1 and fix the original.
The illumination light 3 that is integrally formed with the first mirror 2 emits light, and the reflected light is transmitted by the first mirror 2 and the second and fourth mirrors 4 and 5 that are integrally formed. The first mirror 2, the illumination lamp 3, and the second mirror 4 and the third mirror 5 constitute a scanning optical system and are movable in the direction A by using the traveling body motor 7 as a drive source (in the fixed original reading mode). The state is shown by the broken line in FIG. 1), and the reflected light from the document is coupled to the focusing optical system in the subsequent stage while maintaining a constant optical path length. The reflected light from the third mirror 5 is converged by the lens 38, irradiated onto a CCD line image sensor (hereinafter, simply referred to as “CCD”, which indicates this) 6 and photoelectrically converted.

Next, the configuration and operation of the ADF reading mode will be described. The documents stacked on the document tray 8 are picked up by the pickup roller 9 and the registration roller pair 1.
0, the conveying drum 11, and the conveying roller 12 pass through the reading position B, and are fed to the pair of discharging rollers 13 and 14 and discharged onto the discharging tray 15. When the document passes through the reading position B, it is read by the reading system stopped there (the reading system moved in the fixed document reading mode is fixed and used). Similar to the above, the reading is performed by the illumination lamp 2, and the reflected light is reflected by the first mirror 2 and the second mirror 4, which is integrally formed.
After being focused by the lens 38 via the third mirror 5, C
The CD6 is irradiated and photoelectrically converted. Pickup roller 9 and resist roller pair 10 in these processes
Is driven by a sheet feeding motor (not shown), and the conveying drum 11, the conveying roller 12, the pair of discharging rollers 13, 1
4 is driven by the conveyance motor 16.

Although the white reference plate 21 reads a document of uniform constant density due to variations in the illumination lamp 3, changes over time, uneven sensitivity of each pixel of the CCD 6, and the like,
It is prepared to correct the phenomenon that the read data varies (shading correction). This reference white plate 2 provided for generating the shading correction data is provided here.
1 is referred to as a "first reference white plate", and will be distinguished from a "second reference white plate" described later, which is provided at a fixed position of the reading optical system in the ADF reading mode. The shading correction process will be described in detail later. FIG. 2 shows the configuration of the ADF reading position in the image reading apparatus shown in FIG. FIG. 2 is a view of the reading position B in FIG. 1 seen from above, and as shown in the drawing, the second reference white plate 302 and the ADF original platen glass 3 are arranged on the main scanning line of the ADF reading position B.
01 is set. The second reference white plate 302 is arranged outside the ADF platen glass 301 provided in the passage area of the document conveyed in the sub-scanning direction, but both are placed in the reading area of the CCD 6. When a document passes over the ADF platen glass 301, image information is taken in at the ADF reading position B. Further, the reading of the second reference white plate 302 is performed between the sheets of paper (original) in this example. At this time, by arranging the second reference white plate 302 outside the area where the original image passes, the second reference white plate 302 becomes dirty due to dirt or paper dust that may be attached when the original passes. Can be avoided. The image signal read by the CCD line image sensor 6 is processed by an SBU (Sensor Board Unit) 107 having a CCD, a control circuit therefor, an analog processing circuit for the image signal detected by the CCD, and the like, and then the subsequent image signal. It is input to the processing substrate 20. These image data processing units perform correction / adjustment processing on image data in the process of performing various processing such as analog processing, A / D conversion, and various correction processing on the converted digital signal of the input image signal, In the case of a utilization device, for example, an image forming device, the subsequent image data is output as an image forming signal to the optical writing means for the image carrier (photoconductor).

Next, the circuit configuration and operation of the image signal processing board 20 of the above-mentioned image reading apparatus regarding shading correction applied to the read image data will be described. In the embodiment described below, the reference whiteboard data used to generate correction data such as shading is not read every time a document is set, and when the reading time is shortened, the reference whiteboard data is read. Even if the light source fluctuates during the non-operation, proper shading correction can be performed according to the fluctuation. For this reason, in this embodiment, in addition to the first reference white board 21 (see FIG. 1) used for generating correction data such as shading, the ADF is used.
A second reference white plate 302 used during continuous document reading is provided, the second reference white plate 302 is arranged at a document reading position B during ADF reading, and a reading optical system including an illumination light source, a mirror, etc. during ADF continuous document reading ( The white reference data including the variation of the light source is obtained from the second reference white plate data without moving the document scanning unit), and the shading data generated by the first reference white plate 21 is changed to the second reference white plate data including the variation of the light source. By correcting with the white reference data, it is possible to eliminate the density fluctuation of the read image data without lowering the throughput when reading the ADF continuous document.

FIG. 3 is a block diagram showing the basic structure of the image signal processing unit related to the processing of the read image data, which enables the correction of the shading data with respect to the light source fluctuation by using the second reference white board 302. . In the illustrated embodiment, the SBU 107 and the image signal processing board 20.
In the image data processing section consisting of, the analog image signal read by the CCD image sensor is subjected to A / D conversion, and only the image processing section for performing shading correction on the converted digital data is shown. The correction operation of the embodiment described below is performed by the scanner operation,
A CPU in a control unit (not shown) that controls the entire reading operation such as document transportation of the ADF and processing of a reading signal.
Executed under the control of. The configuration and operation of the circuit of this embodiment will be described with reference to FIG.
The analog image signal read by the CD 201 is a signal processing circuit 20 for waveform shaping, sample hold, amplification, etc.
2 is processed by the A / D converter 203 and converted into digital data by the A / D converter 203.
4 is input.

The shading correction circuit 207 includes an image data input path, a first reference whiteboard data input path, and a second reference whiteboard data input path.
A reference whiteboard data input path (first sheet) and a second reference whiteboard data input path (second and subsequent sheets) are provided so as to be selectable. In the fixed original reading mode, the first reference white board 21 is read before reading the original, and the obtained white reference data from the first reference white board data input path is stored in the FIFO 205 by the number of main scanning pixels. The output data D1sh from the FIFO 205 becomes the shading data Dsh as it is. At the time of reading a document subsequent to the reading of the first reference white plate 21, the document image data from the image data input path is corrected by the previously generated shading data Dsh. For this purpose, the ROM 20 operated by the original reading data Di and the shading data Dsh input from the FIFO 205.
9 is provided. In the ROM 209, arithmetic processing according to the inputs Di and Dsh is performed by a lookup table method created based on a shading correction arithmetic expression stored in advance, and data Do after shading correction arithmetic is generated.
Output.

In the ADF reading mode, except for the continuous original reading, the same processing as the fixed original reading mode is performed on the original reading data and the first reference whiteboard data, and the data Do after the shading correction calculation is performed.
Is output. However, as a matter of course, since it is the ADF reading mode, an operation different from the fixed original reading mode of returning to the original reading position B at the time of ADF reading is required to read the original after reading the first reference white plate. To do. On the other hand, during ADF continuous document reading, the first reference white plate 21 is read before the document is read according to the operation common to the ADF reading mode, and the obtained white reference data from the first reference white plate data input path is input to the shading data D1sh to the FIFO 205. When the operation for storing the number of main scanning pixels is performed, the second reference white board 302 is read (actually, AD
Return to the original reading position B for F reading, and select before reading the first original or after reading as shown in FIG. 4). The white reference data from the second reference whiteboard data input path (first sheet) obtained at this time is used as the peak detection circuit (1) 2
06, and the white reference data peak value D2sh_1 of the specific pixel
Is detected and its value is held. In the case of reading the first sheet, the data D1sh stored in the FIFO 205 at the reading timing of the first sheet as described above is used as the shading data Dsh. When reading the second and subsequent pages, unlike the first page, shading data is not generated, that is, the first page
Only the second reference white plate 302 is read without reading the reference white plate 21. The read white reference data of the second reference white board 302 is
It is input to the peak detection circuit (2) 207 through a second reference whiteboard data input path (second and subsequent sheets) that is an input path different from the first sheet, and the specific pixel (first, peak detection circuit (1) The white reference data peak value D2sh_n (which is preferably the same pixel as that detected in 206) is detected, and the value is held.

Since the generation of shading data is omitted in the reading of the second and subsequent sheets, if the shading data of the first sheet is used as it is, the fluctuation of the light source cannot be guaranteed. The shading data D1sh of the first sheet is corrected by the white reference data of the second reference white board 302, which is included, and the obtained data is used. This correction is processed by the white reference data correction unit 208 shown in FIG. The white reference data correction unit 208 is a peak detection circuit.
(1) White reference data peak value D2sh_1 from 206 and peak detection circuit (2) White reference data peak value D2sh_2 from 207
Is used as the correction data for the shading data D1sh for the first sheet, and the shading data Dsh used for correcting the original data Di for the second and subsequent sheets according to the following formula.
Calculate [n]. Dsh [n] = (D2sh_n / D2sh_1) × D1sh At this time, the correction data is used for each pixel data of the shading data D1sh. After that, at the time of reading the second and subsequent originals, the original image data from the image data input path is subjected to light source fluctuation correction output from the white reference data correction unit 208, and Dsh [n] is used as the shading data Dsh. In order to perform the correction, the original reading data Di and the shading data Dsh from the white reference data correction unit 208 are input to the ROM 209. ROM209
Then, the calculation processing according to the inputs Di and Dsh is performed by the look-up table method created based on the shading correction calculation expression stored in advance, and the data Do after the shading correction calculation is generated and output.

FIG. 4 shows a time chart in which the second reference white plate reading in this embodiment and the image reading timing of the original image reading are related to each other. As shown in FIG. 4, XFGATE, which is a gate signal that sets the period of the effective pixel signal for reading the original, takes in the original reading signal in the “L” section, and in that section, the read data Di from the data input path side is White reference data correction unit 208
The shading correction data Dsh for each pixel is
The data Do is input to the M209 (see FIG. 3), the correction calculation processing is performed in the ROM 209, and the data Do is output. During ADF continuous document reading, D2sh_1 of the peak detection circuit (1) 206 or D2sh_n of the peak detection circuit (2) 207 is updated and "L" → when the second reference whiteboard reading period signal is "L".
The data is fixed when it is negated to “H”. Here, as shown in FIG. 4, the value of D2sh_n is changed for each sheet interval.

Next, another embodiment relating to processing of image data capable of correcting shading data with respect to light source fluctuation will be described. This embodiment basically has the same purpose as the above embodiment intended to be applicable to ADF continuous document reading, but the read data of the second reference white board used for correcting shading data is more appropriate. It aims at the improvement by making it. In the above example,
Peak value D2sh_1 as white reference data according to light source fluctuation,
D2sh_n was detected and correction data was generated based on the peak value. However, when the peak value is used, noise due to uneven sensitivity of the CCD sensor may be mixed in the detection signal of a specific pixel in the detection range. It may be affected and correct correction may not be possible. In this embodiment, this point is improved by using the average value of the read data of the specific area. FIG. 5 is a block diagram showing the basic configuration of the image signal processing unit of the present embodiment relating to the processing of read image data which enables correction of shading data with respect to light source fluctuation. As shown in FIG. 5, in this embodiment, the area averaging unit 5
No. 06 is replaced with the peak detection circuit (1) 206 and the peak detection circuit (2) 207 in the embodiment shown in FIG. 3 to provide the image signal processing unit. There is no difference in the elements. Therefore, only the area averaging unit 506 will be described below, and the other components will be referred to the description given in FIG. 3 above.

In the area averaging unit 506, the second reference white board 3 is used.
In the detection of the white reference data No. 02, the average value of a predetermined area is calculated for each of the image data from the second reference whiteboard data input path (first sheet) and (the second and subsequent sheets), and the obtained average value is calculated. The white reference data correction unit 508 displays the correction data.
Output as D2sh_1 and D2sh_n. The average value of the predetermined area is on the main scanning line in a certain period defined as the second reference whiteboard reading period signal of the CCD sensor 501 (the period when the second reference whiteboard reading period signal referred to in FIG. 4 is “L”). It is calculated by averaging the pixel data included in the period corresponding to the fixed area defined in 1. In addition,
Again, the value of D2sh_n will be changed for each sheet interval. Here, the area is specified by pixel data whose position and number are determined in the main scanning direction, the average is first taken for each line of the main scanning, and the average value taken for each line is further averaged over a predetermined number of lines. The area average value is obtained by the method. As a method of obtaining the area average value, for example, a method of expanding the data of the target area in a dot map form in a two-dimensional memory area and obtaining the overall average value at once may be performed.

FIG. 6 shows an example of the internal structure of the area averaging unit 506 which performs the area averaging process. As shown in FIG. 6, the area averaging unit 506 provides a main scanning averaging unit and a sub scanning averaging unit on each path. That is, the main scanning averaging unit (1) 601 and the sub-scanning averaging unit (1) 603 in the second reference whiteboard data input path (first sheet), and the main scanning average in the second reference whiteboard data input path (second sheet and thereafter). Section (2) 602 and sub-scanning average section (2) 60
4 is provided. An average value of pixel data whose position and number are determined in the main scanning direction from the second reference whiteboard data input path (first sheet) (for example, if 100 pixels near the center of the reference whiteboard is a predetermined area, the 100 pixels Average value) for main scanning averaging (1)
It is calculated from 601 and one average value for each line is output to the sub-scanning average unit (1) 603. The sub-scanning average unit (1) 603 has an internal memory, and the main-scanning average unit (1) 601 for the number of lines while the second reference whiteboard reading period signal is “L” (see FIG. 4). By averaging the average value data from, the area average value of the second reference white board is calculated and held, and D2sh
Output as _1. Also, regarding D2sh_n by the input of the second reference whiteboard data input path (the second and subsequent sheets), as in the case of the second reference whiteboard data input path (the first sheet), the main scanning averaging unit (2) 602 and the sub-scanning average are used. The part (2) 604 calculates and holds the area average value of the second reference white board, and outputs it as D2sh_n. The obtained area averages D2sh_1 and D2sh_n are input to the white reference data correction unit 208 as correction data, and the shading data D1sh for the first sheet is corrected as in the above-described embodiment. By performing the shading correction process based on the shading data that has been corrected according to the light source variation as described above, it is possible to output a read image without deterioration without reducing the throughput in the ADF continuous document reading. .

In the image forming apparatus of the present invention, a line image sensor is used at the input stage of the image information that is the source of image formation, and shading correction is performed on the image signal from the line image sensor using a white reference plate. By replacing or applying the image reading device shown in the above-mentioned embodiment as an image reading unit in an image forming apparatus such as an existing digital copying machine, a scanner device, or a facsimile device having an image reading unit thus configured, The implementation is possible.

[0025]

(1) Effect corresponding to the invention of claim 1 In an image reading apparatus capable of operating in two modes of fixed original reading and ADF reading, a second reference white plate is provided at the ADF original reading position, By correcting the shading data generated based on the read data of the first reference white plate shared by the modes with the read data of the second reference white plate, the first reference white plate can be read as in the ADF continuous original reading. Even if the white plate is not read and the light source fluctuates during that period, proper shading correction can be performed according to the fluctuation, and even if such an operation is performed, the read image does not deteriorate and AD
The throughput of F reading can be improved. (2) Effect corresponding to the invention of claim 2 In addition to the effect of (1) above, the first reference white plate and the second reference white plate are read by a common image sensor, so that the reading with the sensor is performed. Since it is not necessary to separately provide a data processing circuit, the configuration is simplified. (3) Effect corresponding to the invention of claim 3 In addition to the effects of (1) and (2) above, the read data of the second reference white board used for correcting the shading data is the average of the read data of the specific area. By setting the value, C included in the detection signal of the pixel in the detection range
The influence of noise due to uneven sensitivity of the CD sensor can be reduced, and proper correction can be performed.

(4) Effect corresponding to the invention of claim 4 In addition to the effects of (1) to (3), the ratio of the read data value of the second reference white board at the time of shading data creation and shading correction is corrected. By using it as a value, it is possible to provide implementation means that enables more appropriate correction. (5) Effects corresponding to the invention of claim 5 In addition to the effects of (1) to (4), the throughput is improved by correcting the shading data between the continuously conveyed originals. It is possible to read without causing deterioration. (6) Effects corresponding to the invention of claim 6 In addition to the effects of (1) to (5) above, a second reference white plate is added.
By arranging it outside the passage area of the document to be conveyed, it is possible to avoid deterioration of the white plate surface due to dirt or paper dust that may adhere when the document passes. (7) Effects corresponding to the invention of claim 7 A copying machine equipped with the image reading device of claims 1 to 6,
In the image forming apparatus such as a facsimile, the above (1) to
By realizing the effect of (6), it becomes possible to improve the performance of the image forming apparatus.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of an image reading apparatus equipped with an ADF according to an embodiment of the present invention.

2 is an AD in the image reading apparatus shown in FIG.
The structure of the F reading position is shown.

FIG. 3 is a block diagram showing a basic configuration of an embodiment relating to an image signal processing unit capable of correcting shading data with respect to a light source fluctuation.

FIG. 4 shows a time chart in which the second reference white plate reading and the image reading timing of the document image reading are associated with each other.

FIG. 5 is a block diagram showing a basic configuration of another embodiment relating to an image signal processing unit capable of correcting shading data with respect to a light source fluctuation.

6 shows an example of an internal configuration of an area averaging unit 506 in the image signal processing unit of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Platen plate (contact glass), 2 ... Light source lamp, 3 ... 1st mirror, 4 ... 2nd mirror,
5 ... Third mirror 6, 201, 501 ... CCD line image sensor, 1
7 ... SBU (sensor board unit), 20 ... Image signal processing board, 21 ... First reference white board, 204,
504 ... Shading correction circuit, 205, 505 ... F
IFO (First-In First-Out), 206 ... Peak detection circuit (1), 207 ... Peak detection circuit (2), 208, 5
08 ... White reference data correction unit, 209, 509 ... ROM,
301 ... ADF platen glass, 302 ... Second reference white plate, 506 ... Area averaging part, 601 ... Main scanning averaging part (1), 602 ... Main scanning averaging part (2), 6
03 ... Sub-scanning average part (1), 604 ... Sub-scanning average part
(2).

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5B047 AA01 BA02 BB02 BC14 BC18                       DA04 DC01                 5C072 AA01 BA08 FB12 LA15 NA01                       UA02 UA03                 5C077 LL04 MM27 PP06 PP10 PP47                       PP48 PQ08 PQ12 PQ20 PQ24                       SS01 TT06

Claims (7)

[Claims] 1. A reading optical system, a document feeding unit, and a moving unit for the reading optical system, wherein the reading optical system is moved to fix a fixed document reading mode and the reading optical system. An image reading apparatus capable of operating in both modes of reading a document during conveyance, wherein a first reference white plate is provided at a moving position of a reading optical system and a second reference white plate is provided at the fixed position of the reading optical system. An image reading apparatus provided with a white plate, and means for performing shading correction based on read data of a first reference white plate, and means for correcting shading data based on read data of a second reference white plate. . 2. The image reading device according to claim 1, wherein the means for acquiring the read data of the first reference white plate and the second reference white plate is a common image sensor. . 3. The image reading device according to claim 1 or 2, wherein the read data of the second reference white board used for correcting the shading data is an average value of the read data of the specific area. Image reading device. 4. The image reading device according to any one of claims 1 to 3, wherein the means for correcting the shading data is the read data of the second reference white plate at the time of creating the shading data as a correction value and at the time of the shading correction. An image reading apparatus using a ratio of values. 5. The image reading apparatus according to any one of claims 1 to 4, wherein the means for correcting the shading data is adapted to execute the correction between the continuously conveyed originals. Characteristic image reading device. 6. The image reading apparatus according to claim 1, wherein the second reference white plate is arranged outside a passage area of a document to be conveyed. 7. An image forming apparatus, comprising: the image reading apparatus according to claim 1; and a unit that forms an image based on image data.