JP2002325176A - Image reader, its control method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that can accurately read an original image regardless of whether an original to be read is a black/white original or a color original and to provide its control method and a storage medium. SOLUTION: When the original is a black/white original, revising a shading correction coefficient based on data obtained by reading a luminous quantity reference white board adhered to an end of a glass plate for reading of the moving image of the original corrects image data obtained by reading the original (step S5 to S6-S8), and when the original is a color original, an original read interval is extended more than that of reading the black/white original and revising a shading correction coefficient based on data obtained by reading a standard white board until reading of a succeeding original is started corrects image data obtained by reading the original (step S5 to S9-S13).

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 having an automatic document feeder for reading an image of a document conveyed by the automatic document feeder, a control method thereof, and a storage medium.

[0002]

2. Description of the Related Art Conventionally, a copying machine has been known as an image reading apparatus which includes an automatic document feeder and reads an image of a document transported by the automatic document feeder.

In such a copying machine, a document is moved to and placed on a platen glass of a reading device by an automatic document feeder, and then a mirror unit equipped with an illumination light source is moved onto the platen glass. I was trying to read an image.

In recent years, however, in order to increase the number of originals read per unit time, a mirror unit is fixed at a predetermined position, and an original image is read while an original is being fed to a reading device by an automatic original feeder. Is being adopted.

FIG. 1 is a cross-sectional view showing the structure of a color copying machine employing such a flow reading system.

Referring to FIG. 1, the color copying machine mainly includes an automatic document feeder 200, an image scanner unit 201, and a printer unit 202.

The automatic document feeder 200 feeds a document to the image scanner unit 201.

[0008] The image scanner unit 201 reads a document and performs digital signal processing.

The printer unit 202 prints out an image corresponding to the original image read by the image scanner unit 201 on recording paper in full color.

In the image scanner section 201, the original 204 on the original platen glass 203 is a xenon lamp 2
05, and reflected light from the original is reflected by the reflection mirror 2
06 and 207, and an image is formed on the three-line sensor 210 by the lens 209. 3 line sensor 210
Is full color information from reflected light, red (R)
Components, a green (G) component, and a blue (B) component, respectively.
Send to 1.

The signal processing section 211 performs predetermined signal processing on the transmitted electric signals and outputs the processed signals to the printer section 202. The printer unit 202 forms a copy image of the document based on this signal.

The speed of the first mirror unit 208 having the xenon tube lamp 205 and the reflecting mirror 206 is v, and the speed of the second mirror unit 2071 having the reflecting mirror 207 is v / 2. The entire surface of the document is scanned by being driven by a motor (not shown) in a direction perpendicular to the target scanning direction.

When the original is read by the automatic document feeder 200 using the automatic document feeder 200, the first mirror unit 208 is held below the document reading glass 14 and the original is read. , Continuous reading of a document can be realized in a short time.

FIG. 2 is a sectional view showing the structure of the automatic document feeder 200, and FIG.
FIG. 7 is a diagram for explaining how a document 204 is sent by “0”.

In FIG. 3, when the original 204 is placed on the original feed tray 9 and the reading operation of the original is started, the feed roller 8 is lowered onto the original 204 ((a)) and the original 204 is moved.
Is picked up, and the document 204 is conveyed to the lower registration roller 3 and the upper registration roller 4 by the rotation of the conveyance roller 6. In the lower registration roller 3 and the upper registration roller 4, a loop is formed in the sheet, and the skew of the sheet is corrected ((b)).

Next, the document 204 is pressed against the large conveying roller 1 by the roller 2 and is conveyed in accordance with the rotation of the large conveying roller 1, and the small lead roller 13 prevents the document 204 from separating from the large conveying roller 1. ((C)).

Next, the original 204 is conveyed on the flow reading original reading glass 14 to read the original image, and the original 204 is discharged while preventing the original 204 from being separated from the conveying roller 1 by the large lead roller 12. The sheet is conveyed to the upper roller 11 and the lower discharge roller 10 ((d)).

Next, the document 204 is discharged to the discharge tray 15 by the upper discharge roller 11 and the lower discharge roller 10 ((e)).

The roller 2, the small lead roller 13 and the large lead roller 12 are pressed against the large transfer roller 1 with a predetermined pressure by a spring (not shown).

The large transport roller 1 is pressed against the original reading glass 14 with a predetermined pressure by a spring (not shown) so as to absorb a shock when the original 204 collides with the original reading glass 14. I have.

Here, the case where one document is read has been described. However, when reading a plurality of documents continuously, the same operation is repeated repeatedly with a predetermined interval between each document transport.

Further, when the original is read by the flowing reading method, a large number of originals are read in succession. Therefore, when the lighting time of the xenon tube lamp 205 is several minutes, the amount of light fluctuates, and Could not be read correctly.

In order to solve this problem, as shown in FIG. 4, a light amount reference white plate 141 is adhered to an end of the flow-reading document reading glass 14.
The image data is corrected by a known shading correction circuit according to the data obtained when 1 is read.
More specifically, the image data obtained by reading the reference white plate 5102 provided on the
The correction coefficient is set for each pixel so as to be at the level (8 bits: 0 to 255).
If the data obtained when reading is reduced by 2%, the image data obtained when reading the reference white plate 5102 becomes 245 levels, that is, the level of the read image signal of the document increases by 2%. The correction coefficient is changed in real time to correct the light quantity fluctuation of the xenon tube lamp 205.

[0024]

However, in the above-mentioned conventional image reading apparatus, when the original to be read is a black-and-white original, the effect of the light quantity fluctuation of the xenon tube lamp appears on the original read image if the above-described correction method is used. However, if the original to be read is a color original, the subtle variations in the light distribution and the subtle variations in the emission frequency characteristics due to the fluctuations in the amount of light will appear in the scanned image, making it impossible to read the original image accurately. could not.

The present invention has been made in view of this point, and is capable of accurately reading an original image regardless of whether the original to be read is a black-and-white original or a color original. , A control method thereof, and a storage medium.

[0026]

According to a first aspect of the present invention, there is provided an image reading apparatus, comprising: an automatic document feeder for automatically feeding a document to a position where an image written on the document is read; An image reading device for reading an image of a document being conveyed by the automatic document conveyance means, wherein the light irradiation means irradiates light to the document being conveyed by the automatic document conveyance means; Photoelectric conversion means for receiving the light reflected from the document and converting it to an electric signal; processing means for performing signal processing on the converted electric signal; and non-uniformity of the light irradiation means and the photoelectric conversion means. A first reference white plate for correction is irradiated with light by the light irradiating means, and a predetermined signal processing of the signal processing is corrected based on an electric signal obtained by the photoelectric conversion means. A first correcting unit, and irradiating a light to the second reference white plate for correcting a variation of a light amount of the light irradiating unit by the light irradiating unit, based on an electric signal obtained by the photoelectric converting unit; A second correction unit for correcting the predetermined signal processing; and, when the original being transported is a color original, selecting the correction by the first correction unit, while the original being transported is a monochrome original. in case of,
Control means for controlling so as to select the correction by the second correction means.

According to a second aspect of the present invention, in the image reading apparatus of the first aspect, the predetermined signal processing is a shading correction processing.

According to a third aspect of the present invention, there is provided a method for controlling an image reading apparatus, comprising: an automatic document feeder for automatically feeding a document to a position where an image written on the document is read; In a control method for controlling an image reading device that reads an image of a document being conveyed by an automatic document conveyance device, a light irradiation step of irradiating light to a document being conveyed by the automatic document conveyance device with a light irradiation device; A processing step of receiving the light reflected from the document in accordance with the applied light and performing signal processing on the electric signal converted by the photoelectric conversion means for converting the light into an electric signal; and The first reference white board for correcting the non-uniformity is irradiated with light by the light irradiating unit, and based on the electric signal obtained by the photoelectric conversion unit, A first correction step of correcting a predetermined signal processing of the signal processing, and irradiating light to the second reference white plate for correcting a change in the light amount of the light irradiating means by the light irradiating means; A second correction step for correcting the predetermined signal processing based on the electric signal obtained by the conversion means; and a correction by the first correction step when the original being transported is a color original. On the other hand, if the original being transported is a black and white original,
And a control step of performing control so as to select the correction by the second correction step.

According to a fourth aspect of the present invention, in the control method of the third aspect, the predetermined signal processing is a shading correction processing.

In order to achieve the above object, the storage medium according to the fifth aspect includes an automatic document feeder for automatically feeding the original to a position where an image written on the original is read,
A storage medium storing a program that can be implemented by a computer, including a control method for controlling an image reading device that reads an image of a document being conveyed by the automatic document conveyance means, wherein the control method is performed by the automatic document conveyance means. A light irradiating step of irradiating the original being conveyed with light by a light irradiating unit, and an electric conversion unit that receives light reflected from the original according to the irradiated light and converts the received light into an electric signal. A signal processing step of performing signal processing on a signal, and irradiating light to the first reference white plate for correcting non-uniformity of the light irradiation unit and the photoelectric conversion unit by the light irradiation unit; A first correction step of correcting a predetermined signal processing of the signal processing based on the obtained electric signal; A second correction step of irradiating a second reference white plate for correction with light by the light irradiating unit and correcting the predetermined signal processing based on an electric signal obtained by the photoelectric conversion unit; When the original being transported is a color original, the correction in the first correction step is selected. On the other hand, when the original being transported is a black and white original, the correction in the second correction step is selected. And a control step of performing the control.

According to a sixth aspect of the present invention, in the storage medium of the fifth aspect, the predetermined signal processing is a shading correction processing.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In the present embodiment, a copying machine is shown as an application example of the present invention. However, the present invention is not limited to this, and it goes without saying that the present invention can be applied to various other apparatuses.

FIG. 1 is a cross-sectional view showing a schematic configuration of an image reading apparatus according to an embodiment of the present invention. As described above, the present invention is applied to a color copying machine.

Referring to FIG. 1, the image reading apparatus according to the present embodiment is mainly constituted by an automatic document feeder 200, an image scanner unit 201, and a printer unit 202.

The automatic document feeder 200 feeds a document to the image scanner unit 201.

The image scanner unit 201 reads a document and performs digital signal processing.

The printer unit 202 prints out an image corresponding to the original image read by the image scanner unit 201 on recording paper in full color.

In the image scanner section 201, a document 204 on a platen glass (hereinafter, referred to as "platen") 203 is irradiated with light from a xenon tube lamp 205, and reflected light from the document is guided to reflection mirrors 206 and 207. Then, an image is formed on the three-line sensor 210 by the lens 209. The three-line sensor 210 extracts electric signals corresponding to the red (R) component, the green (G) component, and the blue (B) component, which are full-color information, from the reflected light, and transmits the signals to the signal processing unit 211.

The signal processing unit 211 performs predetermined signal processing on the transmitted electric signals and outputs the processed signals to the printer unit 202. The printer unit 202 forms a copy image of the document based on this signal.

The speed of the first mirror unit 208 having the xenon tube lamp 205 and the reflection mirror 206 is v, the speed of the second mirror unit 2071 having the reflection mirror 207 is v / 2, and the electric power of the three-line sensor 210 is The original is scanned by a motor (not shown) in a direction (hereinafter, referred to as a “sub-scanning direction”) perpendicular to a target scanning direction (hereinafter, referred to as a “main scanning direction”).

The standard white plate 5102 is used for correcting data read by the three-line sensor 210 when the xenon tube lamp 205 is used.

When an original is read by the automatic document feeder 200 using the automatic reading apparatus, the first mirror unit 208 is held below the original reading glass 14, and the original is read. , Continuous reading of a document can be realized in a short time.

In the signal processing section 211, the three-line sensor 2
The image signal read by the digital camera 10 is converted into a digital signal, subjected to a predetermined process, and then temporarily stored in a memory (not shown). Synchronously, magenta (M), cyan (C), yellow (Y), black (B
The image signal decomposed into the components K) is transmitted to the printer unit 202. If the original is a monochrome image, the image signal stored in the memory in the signal processing unit 211 is digitally processed, and the black (BK) component image signal is output to the printer in synchronization with the image forming process of the printer unit 202. Part 20
Send to 2.

The M, C, Y, and BK image signals transmitted from the image scanner unit 201 are transmitted to the laser driver 212. The laser driver 212 modulates and drives the semiconductor laser 213 according to the transmitted image signal. The laser beam passes through the polygon mirror 214, the f-θ lens 215 and the mirror 216,
7 is scanned.

The rotary developing device 218 includes the magenta developing device 21
9, four developing units 219 to 222 are alternately in contact with the photosensitive drum 217, and are formed on the photosensitive drum 217. M, C, Y, and M are formed by a cyan developing unit 220, a yellow developing unit 221 and a black developing unit 222. Each electrostatic latent image of BK is developed with the corresponding toner.

The transfer drum 223 includes a paper cassette 224
Alternatively, the paper fed from 225 is wound, and the toner image developed on the photosensitive drum 217 is transferred to the paper.

After the four colors of M, C, Y, and BK are sequentially transferred in this manner, the sheet passes through the fixing unit 226 and is discharged.

FIG. 5 is a diagram showing an example of the configuration of the three-line sensor 210.

Referring to FIG.
10-2 and 210-3 are for reading each wavelength component of R, G and B, respectively.

The three light receiving element rows having different optical characteristics are monolithically mounted on the same silicon chip so that the R, G, and B sensors are arranged in parallel with each other to read the same line of the document. It is configured.

FIG. 6 is an enlarged view in which the light receiving element array of FIG. 5 is enlarged.

As shown in FIG.
Reference numeral 210-3 denotes one pixel in the main scanning direction, for example, one pixel.
It has a width of 0 μm. Then, each sensor 210-1
210-3, so that the short side direction (297 mm) of the A3 document can be read at a resolution of 400 dpi.
There are 5000 pixels in the main scanning direction. The distance between the lines of the R, G, and B sensors 210-1 to 210-3 is, for example, 80 μm, and each line is separated by 8 lines for a sub-scanning resolution of 400 lpi. Further, in each of the line sensors 210-1 to 210-3, an optical filter is formed on the sensor surface in order to obtain predetermined spectral characteristics of R, G, and B.

FIG. 7 is a block diagram showing the configuration of the image scanner unit 201.

In the figure, an image signal output from the CCD 210 is input to an analog signal processing unit 4001, converted into an 8-bit digital image signal in the analog signal processing unit 4001, and then converted to a shading correction unit 4.
002.

FIG. 8 is a block diagram showing a configuration of analog signal processing section 4001. Here, since the processing circuits for R, G, and B are all the same, only the circuit for one color is shown.

In the figure, an image signal output from the CCD 210 is sent to a sample & hold (S / H) section 410.
Sample & 1 to stabilize the analog signal waveform
It is held. A CPU (not shown) converts the image signal into an A / D converter 41 via a voltage control circuit 4103.
To make full use of the dynamic range of 05,
The variable amplifier 4103 and the clamp circuit 4102 are controlled. The A / D converter 4105 converts the analog image signal into
For example, it is converted into an 8-bit digital image signal.

Referring back to FIG. 7, the 8-bit digital image signal is subjected to shading correction by a known shading correction method in a shading correction unit 4002. When reading shading data, the CPU responds to a read signal from the three-line sensor 210.
Stores a read signal for one line from the standard white plate 5102 in the line memory 4003, and sets a shading correction coefficient for setting the read data of each pixel stored in the line memory 4003 to a predetermined level, for example, 240, in the pixel. Calculated for each line, and this is stored in the coefficient memory
005. When reading the original,
In synchronization with the output of each pixel by the line reading of the line sensor 210, the shading correction coefficient corresponding to the pixel is read from the coefficient memory 4005,
At 07, shading correction is performed by multiplying each pixel signal from the three-line sensor 210.

When a black-and-white document is read by the flow reading method, the shading correction coefficient is determined in real time according to data obtained by reading the light amount reference white plate 141 (see FIG. 4) attached to the end of the flow reading document reading glass 14. Has been corrected. For example, when the data obtained by reading the light amount reference white plate 141 decreases by 2%, the image data obtained by reading the reference white plate 5102 becomes 245.
The correction coefficient is changed in real time so that the level becomes the level, that is, the level of the read image signal of the document increases by 2%, and the light amount fluctuation of the xenon tube lamp 205 is corrected.

Next, the correction of the physical distance of the three-line sensor 210 will be described.

As shown in FIG. 6, since the light receiving sections 210-1, 210-2 and 210-3 of the sensor 210 are arranged at a fixed distance, the delay elements 401 and 402 cause the light receiving sections 210-1, 210-2 and 210-3 to move in the sub-scanning direction. Is corrected. More specifically, the R and G signals read earlier in the sub-scanning direction with respect to the B signal are delayed in the sub-scanning direction and superimposed on the B signal.

A first look-up table (hereinafter referred to as "L
Reference numeral 4008) is used to correct the gradation of the original image reading signal. A document on which an image having a predetermined density shown in FIG. 9 is drawn is placed on the platen 203, and the document image data is read. As shown in FIG. 10, when the read level 1001 has no linearity, linearity is obtained. The input signal is corrected by the correction curve 1002 for
003.

The memory 4009 temporarily stores the image signal, and outputs the image signal in synchronization with the printer unit 202. In addition, from the memory 4009, a predetermined density (hereinafter, referred to as a predetermined density)
9 is output, and the printer unit 203 generates a PG image similar to the image shown in FIG.

Each of the log converters 403 to 405 is constituted by a look-up table ROM, and converts a luminance signal into a density signal.

The second LUT 4010 is the first LUT 4
The circuit similar to 008 performs gradation correction of the printer unit 203.

A PG image based on the PG data output from the memory 4009 is read by the image scanner unit 201 and the read data and the memory 40 are read.
09 is compared with the PG data output from the PG image, and when linearity is not obtained in the PG image, as shown in FIG.
The input signal is corrected by the correction curve and output.

The masking and UCR circuit 406 is a well-known circuit, and a detailed description thereof is omitted. However, the Y, M, C, and BK signals for output are read each time the reading operation is performed according to the input three primary color signals. Are sequentially output at a predetermined bit length, for example, 8 bits.

The above circuits are controlled by a CPU (not shown).

The operation processing executed by the image reading apparatus configured as described above will be described below with reference to the flowchart of FIG.

In FIG. 11, an operator sets a document on the document feed tray 9 of the automatic document feeder 200, designates whether the document is a monochrome document or a color document from an operation unit (not shown) (step S1), and starts. When the copying operation is started by the key (step S2), the CPU (not shown) moves the first mirror unit 208 to the reference white plate 510.
2 and reads one line of shading correction data, and stores the calculated shading correction coefficient in the coefficient memory 4 in the shading correction circuit 4002.
006 is set (step S3).

Next, the first mirror unit 208 is moved below the original glass plate 14 (step S).
4).

Next, it is determined whether the original is a black-and-white original or a color original (step S5). If the original is a black-and-white original, the feed roller 8 of the automatic document feeder 200 is lowered onto the original 204 (step S5). In FIG. 3A, the uppermost sheet of the original 204 is picked up, and the original 204 is rotated by the rotation of the conveying roller 6 so that the lower registration roller 3 and the upper registration roller 4 are rotated.
Transported to A loop is formed in the sheet at the lower registration roller 3 and the upper registration roller 4, and the skew of the sheet is corrected (FIG. 3B).

Next, the document 204 is pressed against the large conveying roller 1 by the roller 2 and is conveyed in accordance with the rotation of the large conveying roller 1, and the small lead roller 13 prevents the document 204 from separating from the large conveying roller 1 ( FIG. 3 (c)).

Next, the original 204 is conveyed onto the original reading glass 14 to perform an original image reading operation. The original 204 is ejected while preventing the original 204 from being separated from the conveying roller 1 by the large lead roller 12. The sheet is conveyed to the upper paper roller 11 and the lower paper discharge roller 10 (FIG. 3D).

Next, the document 204 is discharged onto the discharge tray 15 by the upper discharge roller 11 and the lower discharge roller 10 (FIG. 3E). At this time, the CPU sets the shading correction coefficient set in the coefficient memory 4006 in the shading correction circuit 4002 to 1 based on the data obtained when reading the light amount reference white plate 141 attached to the flow reading original glass 14. The document image data is read into the memory 4009 while correcting each line (step S6) (step S7).

Next, the document reading operation (step S) is performed until there is no document placed on the automatic document feeder 200.
6 and S7) are repeated (step S8), and when there are no more originals, the image data is read from the memory 4009, a copy image is formed by the printer unit 202 (step S14), and the copy operation ends.

If the original is a color image, the automatic reading operation of the automatic original feeder 200 is performed (step S9), and the original image data is read into the memory 4009 (step S10).

Next, it is determined whether or not the document placed on the automatic document feeder 200 remains (step S).
11) If the original remains, the first mirror unit 208 is moved below the reference white plate 5102, and the shading correction coefficient is set in the coefficient memory 4006 in the shading correction circuit 4002 as in step S3. Then, the first mirror unit 208 is moved below the original glass 14 (step S13).
Steps S9, S10, S12 and S13 are repeated (step S11). When there are no more originals, the image data is read from the memory 4009, a copy image is formed by the printer unit 202 (step S14), and the copy operation ends.

In the present embodiment, a method of printing all original image data after storing it in the memory 4009 has been described. However, a method of printing and outputting original image data while reading it into the memory 4009 is adopted. Is also good.

In the present embodiment, when performing the flow reading of the black-and-white document, the flow reading document reading glass 14 is used.
The method of correcting the shading correction coefficient in real time according to the data obtained by reading the light amount reference white plate 141 attached to the end of the original reading glass 14 is not limited to this. The reading of the light amount reference white plate 141 attached to the document may be performed between the document reading and the document reading, and the shading correction coefficient may be changed every time the document is read.

In the present embodiment, the method is used in which the operator specifies whether the original is a color original or a black and white original. However, the present invention is not limited to this. Is also good.

Further, in this embodiment, when the original is a color original, the reference white plate 5102 is read for each original,
Although the updating of the shading correction coefficient has been performed, but the reading image is not affected, the reference white plate 5102 may be read for each of a plurality of documents to update the shading correction coefficient. In this case, when reading a document in which the reference white plate 5102 is not read, the light amount reference white plate 14 affixed to the end of the flow reading document reading glass 14.
Even if a method of correcting the shading correction coefficient in real time according to the data obtained by reading 1 is used,
A method may be used in which reading of the light amount reference white plate 141 affixed to the end of the flow reading document reading glass 14 is performed between document reading and document reading, and the shading correction coefficient is changed every time the document is read.

Further, in this embodiment, when the original is a black-and-white original, the shading correction coefficient is updated only before reading the first original. It is also possible to update the shading correction coefficient for each of a plurality of documents.

A storage medium storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or an apparatus, and a computer (or CPU or MPU) of the system or apparatus stores the storage medium in the storage medium. It goes without saying that the object of the present invention is also achieved by reading and executing the program code.

In this case, the program code itself read from the storage medium realizes the novel function of the present invention, and the storage medium storing the program code constitutes the present invention.

Examples of a storage medium for supplying the program code include a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, and C
A D-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used. Further, the program code may be supplied from a server computer via a communication network.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS running on the computer based on the instruction of the program code. It goes without saying that a part or all of the actual processing is performed, and the functions of the above-described embodiments are realized by the processing.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

[0089]

As described above, according to the present invention, when the original being conveyed by the automatic original conveying means is a color original, the light irradiating means and the light irradiating means are used. Irradiating the first reference white plate for correcting non-uniformity of the photoelectric conversion unit with light by the light irradiation unit;
The document is irradiated with light by the light irradiating unit based on the electric signal obtained by the photoelectric conversion unit, and a predetermined signal processing of the signal processing for the electric signal obtained by the photoelectric conversion unit is corrected. On the other hand, when the original being conveyed is a black-and-white original, light is irradiated by the light irradiating means on the second reference white plate for correcting fluctuations in the amount of light of the light irradiating means, and is obtained by the photoelectric conversion means. Based on the received electric signal, the original is irradiated with light by the light irradiating unit, and a predetermined signal processing among the signal processing for the electric signal obtained by the photoelectric conversion unit is corrected. Regardless of whether the document is a monochrome document or a color document, the document image can be read accurately.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of the automatic document feeder of FIG.

FIG. 3 is a diagram for explaining how a document is sent by the automatic document feeder of FIG. 2;

FIG. 4 is a bottom view of the flow-reading glass used in the image reading apparatus of the present embodiment.

FIG. 5 is a diagram showing a configuration of a CCD sensor used in the image reading device of the present embodiment.

FIG. 6 is an enlarged view of a light receiving element of the CCD sensor of FIG.

FIG. 7 is a block diagram illustrating a configuration of a signal processing unit used in the image reading device according to the present embodiment.

FIG. 8 is a block diagram illustrating a configuration of an analog signal processing unit used in the image reading device according to the present embodiment.

FIG. 9 is a diagram illustrating an example of a PG image.

FIG. 10 is a diagram for explaining one method of gradation correction.

FIG. 11 is a flowchart illustrating a procedure of an operation process performed by the image reading apparatus of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Large conveyance roller 2 Roller 3 Below the registration roller 4 Above the registration roller 6 Transportation roller 8 Paper feed roller 9 Document feed tray 10 Below the paper discharge roller 11 Above the paper discharge roller 12 Large lead roller 13 Small lead roller 14 Flowing document reading glass 200 Document Automatic conveyance device 201 Image scanner unit 202 Printer unit 203 Document table glass 205 Xenon tube lamp 206, 207 Reflection mirror 2071 Second mirror unit 208 First mirror unit 209 Lens 210 3 Line sensor 211 Signal processing unit 212 Laser driver 213 Semiconductor Laser 214 Polygon mirror 215 f-θ lens 216 Mirror 217 Photosensitive drum 218 Rotary developing device 223 Transfer drum 224, 225 Paper cassette 226 Fixing unit 5102 Standard white plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5B047 AA01 AB04 BB02 BC14 DA04 5C072 AA01 BA08 BA19 FB12 QA16 UA02 UA03 XA01 5C077 LL19 MM03 MP08 PP06 PP32 SS01 5C079 HB01 JA23 LA12 LA19

Claims (6)

[Claims] An automatic document feeder configured to automatically feed a document to a position where an image written on the document is read;
In an image reading apparatus for reading an image of a document being conveyed by the automatic document conveyance means, light irradiating means for irradiating light to the document being conveyed by the automatic document conveyance means, and Photoelectric conversion means for receiving the reflected light and converting it to an electric signal; processing means for performing signal processing on the converted electric signal; and correcting non-uniformity of the light irradiation means and the photoelectric conversion means A first correction means for irradiating a first reference white plate with light by the light irradiating means for correcting predetermined signal processing among the signal processing based on an electric signal obtained by the photoelectric conversion means; Irradiating a light to the second reference white plate for correcting the variation of the light amount of the light irradiating means with the light irradiating means, and based on the electric signal obtained by the photoelectric conversion means, A second correction unit that corrects the signal processing of the above. If the original being transported is a color original, the correction by the first correction unit is selected, and if the original being transported is a monochrome original, And a control means for controlling so as to select the correction by the second correction means. 2. The image reading apparatus according to claim 1, wherein the predetermined signal processing is a shading correction processing. 3. An automatic document feeder for automatically feeding a document to a position where an image written on the document is read,
A control method for controlling an image reading apparatus that reads an image of a document being conveyed by the automatic document conveyance means, wherein a light irradiation step of irradiating light by light irradiation means to the document being conveyed by the automatic document conveyance means; A processing step of receiving light reflected from the original in response to the irradiated light and performing signal processing on the electric signal converted by the photoelectric conversion means for converting the light into an electric signal; and the light irradiation means and the photoelectric conversion means A first reference white plate for correcting non-uniformity is irradiated with light by the light irradiating means, and a predetermined signal processing of the signal processing is corrected based on an electric signal obtained by the photoelectric conversion means. Performing a first correction step of: irradiating light to the second reference white plate for correcting a variation in the amount of light of the light irradiating means by the light irradiating means; A second correction step of correcting the predetermined signal processing based on the electric signal obtained by the conversion means; and selecting the correction by the first correction step when the original being transported is a color original. A control step of selecting the correction by the second correction step when the original being conveyed is a black-and-white original. 4. The method according to claim 3, wherein the predetermined signal processing is shading correction processing. 5. An automatic document feeder for automatically feeding a document to a position where an image written on the document is read,
A storage medium storing a computer-implementable program, including a control method for controlling an image reading apparatus that reads an image of a document being conveyed by the automatic document conveyance means, wherein the control method is performed by the automatic document conveyance means. A light irradiating step of irradiating the original being conveyed with light by light irradiating means; A signal processing step of performing signal processing on the signal; and irradiating the light by the light irradiating unit to the first reference white plate for correcting the non-uniformity of the light irradiating unit and the photoelectric converting unit. A first correction step of correcting a predetermined signal processing of the signal processing based on the obtained electric signal; A second correction step of irradiating a light to the second reference white board for correcting the above by the light irradiating means, and correcting the predetermined signal processing based on the electric signal obtained by the photoelectric conversion means; If the original being transported is a color original, the correction in the first correction step is selected, while if the original being transported is a black-and-white original, the correction in the second correction step is selected. And a control step of performing control as described above. 6. The storage medium according to claim 5, wherein said predetermined signal processing is shading correction processing.