JP2007135025A - Image reading apparatus and method for creating shading correcting data - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of reducing a labor by making a black reference original unnecessary while being able to eliminate the effect of the light-quantity ripple of a light source, and capable of preparing a more accurate black reference data and a method for preparing a shading correcting data. <P>SOLUTION: The image reading apparatus has the light source 13 irradiating a white reference original with a light, an image-sensing means 16 for outputting an electric signal based on a reflected light from the white reference original, and an A/D conversion means 19 for analog-digital converting the electric signal from the image-sensing means 16. The image reading apparatus further has a white reference-data storage means 20 for storing an output signal from the A/D conversion means 19, at a time when the reflected light from the white reference original is read by the image-sensing means 16 as a white reference data under the state in which the light source 13 is lit. The image reader further has a black correcting-data arithmetic means 21 for conducting an arithmetic operation by using the output signal from the A/D conversion means 19 under the state in which the light source 13 is put out, and the white reference data from the white reference-data storage means 20 and creating the black reference data; and a black reference-data storage means 22 storing the black reference data. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image reading apparatus used in a scanner, a facsimile machine, a copying machine, and the like, and a shading correction data generation method in the image reading apparatus, and in particular, an influence of a ripple of a light source by a technique not using a black reference original. The present invention relates to an image reading apparatus and a shading correction data creation method suitable for creating black reference data that can eliminate the above.

Along with the spread of computers and the increase in the volume of data to be communicated, there are many image reading apparatuses that read an original made up of printed characters and photographs and convert it into electronic image data.
Many of such image reading apparatuses use a one-dimensional image sensor, and scan image data line by line to read image information.

The document surface at the location scanned by the one-dimensional image sensor is lit in a line by a lamp.
In the document fixing type image reading apparatus, the one-dimensional image sensor and the lamp move in a direction orthogonal to the longitudinal direction, and accordingly, the image is scanned and read line by line. In a document moving type image reading apparatus, a one-dimensional image sensor and a lamp are fixed, and an image is scanned and read while the document moves.

In such an image reading apparatus, the characteristics of the lamp vary with time. Also, there is a difference in the brightness of the original between the central part and the peripheral part of the lamp. Furthermore, the characteristics of the individual photoelectric conversion elements constituting the image sensor are not the same.
For this reason, correction called shading correction has been conventionally performed in order to adjust the density of the read image.

Various techniques related to this shading correction have been proposed.
For example, a light source, a white reference plate, an imaging unit that converts optical information in the main scanning direction on which reflected light from the original or white reference plate is imaged, and a light source and an imaging unit are moved in the sub-scanning direction. And moving means for reading the document line by line, white data holding means for holding white data obtained from the imaging means by imaging reflected light from the white reference plate, and obtained from the imaging means with the light source turned off. Black data holding means for holding black data, shading calculation means for calculating shading correction coefficients from the data of the white data holding means and the black data holding means, and completion of data input to the white data holding means and the black data holding means And a control means for executing correction coefficient calculation by the shading calculation means while moving the position of the light source and imaging means by the movement means. Some (for example, see Patent Document 1.).

  According to such a configuration, the correction coefficient calculation by the shading calculation unit is performed while the position of the light source and the image pickup unit is moved by the moving unit after the data input to the white data holding unit and the black data holding unit is completed. Since it is executed, the reading time is shortened. Further, since the scale of the logic circuit of the shading calculation means does not increase, the cost of the image reading apparatus is not increased. Furthermore, since it is not necessary to increase the amount of light source and use a high-speed imaging means, it is possible to read an image with high image quality and high speed.

As another conventional technique, for example, an image reading unit that reads an image of a document by moving a scanning body mounted with a lamp in the sub-scanning direction, and the scanning body is placed under a white reference plate before starting image reading. The black level correction data is collected by using the black image data read with the lamp turned off while the scanning body is moving under the white reference plate. A white level using the white image data when the white reference plate is read by lighting the lamp at a predetermined timing before starting the reading of the image and after collecting the data for black level correction, after executing the data sampling processing And a means for executing white level correction data collection processing for collecting correction data (see, for example, Patent Document 2).
According to such a configuration, it is substantially necessary to collect the black level correction data as compared with the conventional case where the black level correction data is collected after the scanning body is moved below the white reference plate. The document image reading start time can be shortened by the time.

Further, as another conventional technique, for example, a reference black correction data generation unit that generates reference black correction data in a reference black correction circuit when a document reading start signal indicating timing of starting image reading processing of a document is generated; After the reference black correction data is generated by the reference black correction data generating means, the white reference plate is read using the lighting means for turning on the main light source and the auxiliary light source and the main light source turned on by the lighting means. The reference white correction data generating means for generating the reference white correction data, the original image reading means for reading the original using the main light source lit by the lighting means, and the original image reading means. The document image data includes a correction unit that corrects data based on the reference black correction data and the reference white correction data (for example, patents). Document 3 reference.).
According to such a configuration, when generating black correction data without using a reference blackboard serving as a reference for black density, generation of black correction data is started using the reading start signal. A blackboard and a dedicated signal line are not required, and the number of connection lines to the main system can be reduced.
JP 2001-036743 A JP 2003-179731 A JP 2004-080730 A

  However, in the above-described conventional image reading apparatus, no consideration is given to the light amount ripple of the light source, and therefore the influence of the light amount ripple cannot be eliminated.

As shown in FIG. 7, a light source used in a one-dimensional CIS sensor or the like is generally one in which LEDs as the light source 100 are arranged at certain intervals. Therefore, a light amount ripple occurs depending on the position in the main scanning direction. To do.
As a method for eliminating the influence of the light amount ripple of the light source, for example, it is conceivable to use an output signal when the light source is turned on and a black reference original is read by a sensor as black reference data for shading correction. Thereby, since the black reference data includes ripple information, the influence of the light amount ripple can be eliminated. However, in this case, there is a problem that it takes time since it is necessary to prepare a black reference document.

  Therefore, as a technique for eliminating the need for a black reference original, for example, it is conceivable to use the sensor output with the light source turned off as black reference data. According to this method, the black reference document is certainly unnecessary. However, since the black reference data obtained by this method is obtained with the light source turned off, it does not include ripple information. For this reason, there is a problem that the influence of the light amount ripple cannot be eliminated even if a black document is read at the time of actual document reading and the output data of the photoelectric conversion element is corrected.

  The present invention has been considered in view of the above circumstances, and it is possible to reduce the time and effort by eliminating the need for a black reference document, and to create more accurate black reference data that can eliminate the influence of the light intensity ripple of the light source. An object of the present invention is to provide an image reading apparatus and a shading correction data generation method that can be performed.

  In order to achieve this object, the image reading apparatus of the present invention uses a light source for irradiating light to the white reference realization means and optical information in the main scanning direction on which the reflected light from the white reference realization means is formed into an electrical signal. An image reading apparatus comprising an imaging means for conversion and an A / D conversion means for analog-to-digital conversion of an electrical signal output from the imaging means, and the reflection from the white reference realizing means with the light source turned on White reference data storage means for storing the electrical value of the output signal of the A / D conversion means when the light is read by the imaging means as white reference data, and output of the A / D conversion means with the light source turned off Black correction data calculation means for generating black reference data by performing calculation using the electrical value of the signal and the white reference data extracted from the white reference data storage means; and black reference data storage means for storing black reference data With It is constituted.

When the image reading apparatus has such a configuration, in the shading correction of the output data of the imaging unit, the black reference data used for the shading correction is generated, the white reference data used for the shading correction, and the light source is turned off. Since the calculation is performed using the output data of the A / D conversion means, the black reference data can be created by reflecting the ripple information included in the white reference data. For this reason, more accurate black reference data that can eliminate the influence of the light amount ripple of the light source can be created.
Further, in the present invention, the black reference data is created by calculation using the white reference data extracted from the white reference data storage means and the output data of the A / D conversion means with the light source turned off. This eliminates the need for a black reference document. This eliminates the trouble of preparing a black reference document.

In the image reading apparatus of the present invention, the electrical value of the output signal of the A / D conversion means when the light source is turned off is used as data when the light source is turned off, and the black correction data calculation means is used when the white reference data and the light source are turned off. The sum obtained by this addition is divided by a predetermined coefficient, the quotient obtained by this division and the data when the light source is turned off are added, and the sum obtained by this addition is referred to as black reference data. It is as composition to do.
When the image reading apparatus has such a configuration, more accurate black reference data including ripple information can be calculated by executing the calculation procedure shown.

  In the image reading apparatus of the present invention, the white reference data storage unit has a plurality of white reference data storage units for storing the white reference data acquired for each of the plurality of colors for each color, and the black correction data calculation unit However, using the electrical value of the output signal of the A / D conversion means when the light source is turned off, and the white reference data for each color extracted from the plurality of white reference data storage units of the white reference data storage means A black reference data is created for each color by performing an operation, and the black reference data storage means has a plurality of black reference data storage units for storing the black reference data for each of the colors for each color.

  When the image reading apparatus has such a configuration, even in a color image reading apparatus using a white light source and having photoelectric conversion elements (imaging means) for each color of R, G, and B, it is possible to obtain each color with high accuracy without taking time and effort. Black reference data can be created.

In addition, the image reading apparatus of the present invention is configured to include a control unit that turns on or off the light source, performs photoelectric conversion processing in the imaging unit, and calculates black reference data in the black correction data calculation unit.
When the image reading apparatus has such a configuration, the control unit controls the light source, the imaging unit, and the black correction data calculation unit to create more accurate black reference data that can eliminate the influence of the light intensity ripple. Can do.

In the image reading apparatus of the present invention, the imaging means has a one-dimensional image sensor and / or a two-dimensional image sensor.
When the image reading apparatus has such a configuration, accurate black reference data can be created by the imaging unit in either case of the one-dimensional image sensor or the two-dimensional image sensor.

  In the shading correction data creation method of the present invention, the imaging means is configured to illuminate the optical information in the main scanning direction in which the light source irradiates the white reference realizing means and the reflected light from the white reference realizing means. A shading correction data generation method having a procedure for converting to a signal and a procedure for A / D conversion means for analog-to-digital conversion of an electrical signal output from an imaging means, and realizing a white reference with the light source turned on The procedure in which the white reference data storage means stores the electrical value of the output signal of the A / D conversion means when the reflected light from the means is read by the imaging means, and the A with the light source turned off. A procedure in which the black correction data calculation means calculates black reference data by using the electrical value of the output signal of the / D conversion means and the white reference data extracted from the white reference data storage means; There a method for quasi-data storage means having a procedure for storing black reference data.

When the shading correction data creation method is such a method, the black reference data used for the shading correction is generated, the white reference data used for the shading correction, the output data of the imaging means with the light source turned off, Therefore, a black reference document is not necessary. For this reason, it is possible to eliminate the trouble of using a black reference document.
Further, since the white reference data includes ripple information, the black reference data created by calculation using the white reference data also includes ripple information. Therefore, it is possible to create black reference data that can eliminate the influence of the light amount ripple of the light source. Therefore, more accurate black reference data can be created compared to the case where the sensor output with the light source turned off is used as it is as black reference data.

  As described above, according to the present invention, in the shading correction of the output data of the imaging means, the creation of the black reference data used for the shading correction, the white reference data used for the shading correction, and the state where the light source is turned off. Since the calculation is performed using the output data of the imaging means, a black reference document is not required, and more accurate than when the sensor output with the reading light source turned off is used as it is as black reference data. Black reference data can be created.

  Hereinafter, preferred embodiments of an image reading apparatus and a shading correction data generation method according to the present invention will be described with reference to the drawings.

[First embodiment]
First, a first embodiment of an image reading apparatus and a shading correction data creation method of the present invention will be described with reference to FIG.
FIG. 1 is a schematic side view showing the physical configuration of the image reading apparatus of the present embodiment.
As shown in the figure, the image reading apparatus 1a includes an original table glass 11, a white reference original 12, a light source 13, and a mirror 14 (first mirror 14-1, second mirror 14-2, and third mirror 14). -3), a lens 15, and an imaging means 16.

The document table glass 11 is a transparent glass plate on which a document is placed.
The white reference original (white reference chart) 12 is a pure white sheet for realizing the white reference. The white reference document 12 is placed on the document reading area on the upper part of the document glass 11 with the reading surface facing downward.
In the present embodiment, the white reference document is used as a means for realizing the white reference. However, the present invention is not limited to the white reference document, and for example, a white reference plate can be used.
Here, the white reference plate is a plate-like member having a white surface, and is arranged in the vicinity of the upper end portion of the original table glass 11 with the main scanning direction perpendicular to the original paper surface as the longitudinal direction.
The white reference original and the white reference plate are collectively referred to as “white reference realizing means”.

A light source (lamp) 13 irradiates light on the original (white reference original 12) from below the original table glass 11. For example, as shown in FIG. 7, the light source 13 may have a configuration in which a plurality of light sources 13 are arranged in a line at regular intervals.
The first mirror 14-1 reflects the reflected light from the white reference document 12 and sends it to the second mirror 14-2. The reflected light is sequentially reflected by the second mirror 14-2 and the third mirror 14-3 and is sent to the imaging means 16 through the lens 15.

The imaging means (image sensor, photoelectric conversion element) 16 is constituted by a reading element for one line, and an image of a part irradiated by the light source 13 is formed on the reading element. Then, the imaging means 16 converts the optical information in the main scanning direction on which the reflected light from the original is formed into an electrical signal and outputs it.
For example, an image sensor can be used as the imaging unit 16. This image sensor may be a one-dimensional image sensor or a two-dimensional image sensor.
The image sensor includes a CCD image sensor, a CMOS image sensor, a CIS (contact image sensor), and the like.

The light source 13, the first to third mirrors 14-1 to 14-3, the lens 15, and the imaging unit 16 are housed inside the main body (device main body 17) of the image reading apparatus 1 a.
The light source 13 and the first mirror 14-1 are housed in a moving body 18, and are reciprocated in a sub-scanning direction (left-right direction in FIG. 1) parallel to the longitudinal direction of the document table glass 11 by a motor (not shown). Can move.

Further, as shown in FIG. 2, the image reading apparatus 1a includes an A / D conversion unit 19, a white reference data storage unit 20a, a black correction data calculation unit 21a, a black reference data storage unit 22a, and a control unit 23. And. FIG. 2 is a block diagram showing the configuration of the control system of the image reading apparatus.
The A / D conversion means 19 converts the electrical signal (analog voltage output) output from the imaging means 16 from an analog signal to a digital signal.
The white reference data storage means 20a stores the voltage value (electrical value) of the output signal of the A / D conversion means 19 when the reflected light from the white reference document 12 is read by the imaging means 16 as white reference data.

The black correction data calculation means 21a outputs the voltage value (data when the light source is turned off) of the A / D conversion means 19 when the light source 13 is turned off and the white reference data stored in the white reference data storage means 20a. To calculate black reference data.
The black reference data storage means 22a stores the black reference data created by the black correction data calculation means 21a.

The control unit 23 controls various functions of the image reading apparatus 1a. Specifically, the control unit 23 performs control such that the light source 13 is turned on or off, the photoelectric conversion process in the imaging unit 16, the black reference data calculation process in the black correction data calculation unit 21a, and the like.
In the present embodiment, the white reference data and the black reference data are collectively referred to as “shading correction data”.

Next, the operation (shading correction data creation method) of the image reading apparatus according to the present embodiment will be described with reference to FIGS.
FIG. 3 is a flowchart showing an operation procedure of the shading correction data creation method of the present embodiment, and FIG. 4 is a curve diagram showing output values of white reference data, light source extinction data, and black reference data obtained by the image reading apparatus. It is.

On the platen glass 11 of the image reading apparatus 1a, a white reference document 12 is placed with the reading surface facing down.
First, in order to create white reference data for shading correction, the light source 13 is turned on under the control of the control means 23 (step 10). The white reference document 12 is irradiated with light emitted from the light source 13 by this lighting. The irradiated light is reflected by the white reference document 12, and the reflected light is captured by the imaging means 16 via the mirrors 14-1 to 14-3 and the lens 15, and is converted into an electrical signal and output. The output electrical signal is converted from an analog signal to a digital signal by the A / D conversion means 19 and output (reading of the white reference document, step 11).
The voltage value of the digital signal (output signal) output from the A / D conversion means 19 is stored in the white reference data storage means 20a as white reference data (step 12).
The white reference data (Vwhite) stored in the white reference data storage means 20a is represented by a curve as shown as “white reference original reading” in FIG. In the figure, Vwhite (n) indicates the sensor output level at position n when reading the white reference document.

Next, the light source 13 is turned off under the control of the control means 23 to create black reference data (step 13).
The analog signal output from the image pickup means 16 is converted into a digital signal by the A / D conversion means 19 (white reference original reading, step 14).
The voltage value (data when the light source is turned off, Vledoff) of the digital signal output is represented by a straight line as shown as “light source off reading” in FIG. In the figure, Vledoff (n) indicates the sensor output level at position n when the light source is turned off.

  In the black correction data calculation means 21a, the digital signal output from the A / D conversion means 19 is input and the white reference data stored in the white reference data storage means 20a is taken out (black reference data calculation data). Acquisition, step 15). Then, the black reference data is calculated by the following formula 1 using the data when the light source is turned off based on the digital signal and the white reference data extracted from the white reference data storage means 20a (calculation, step 16).

  Vblack (n) = (Vwhite (n) −Vledoff (n) / X + Vledoff (n) (Equation 1)

This Formula 1 adds the white reference data (Vwhite (n)) and the light source off time data (Vledoff (n)), and divides the sum obtained by this addition by a predetermined (arbitrary) coefficient (X). The quotient obtained by this division and the data when the light source is turned off (Vledoff (n)) are added, and the sum obtained by this addition is calculated as black reference data (Vblack (n)).
Then, the calculated black reference data is stored in the black reference data storage means 22a (step 17).
The black reference data (Vblack) stored in the black reference data storage means 22a is represented by a curve as shown by a dotted line in FIG. In the figure, Vblack (n) indicates black reference data at position n.

  With the above operation, it is possible to remove the light amount ripple of the light source during shading correction from the signal output from the sensor with the light source turned off and the white reference data when the white reference document is read with the light source turned on. Black reference data can be created. As a result, more accurate black reference data can be created as compared with a method in which the output of the A / D conversion means with the light source turned off is used as it is as black reference data.

[Second Embodiment]
Next, a second embodiment of the image reading apparatus and shading correction data creation method of the present invention will be described with reference to FIG.
FIG. 2 is a block diagram showing the configuration of the control system of the image reading apparatus of this embodiment.
This embodiment is different from the first embodiment in the type of white reference data or black reference data that is created. That is, in the first embodiment, one type of data is created for both the white reference data and the black reference data, whereas in this embodiment, both the white reference data and the black reference data are generated for each color of RGB. To be created. Other components are the same as those in the first embodiment.
Therefore, in FIG. 5, the same components as those in FIG. 1 and the like are denoted by the same reference numerals, and detailed description thereof is omitted.

The image reading apparatus 1b according to the present embodiment includes an original table glass 11, a white reference original 12, a light source 13, and a mirror 14 (first mirror 14-1, second mirror 14-2, and third mirror 14-3). A lens 15 and an imaging means 16.
Here, the light source 13 is a white light source.
The imaging means 16 has a photoelectric conversion element for each color of R (RED), G (GREEN), and B (BRUE).

Further, as shown in FIG. 5, the image reading apparatus 1b includes an A / D conversion unit 19, a white reference data storage unit 20b, a black correction data calculation unit 21b, a black reference data storage unit 22b, and a control unit 23. And.
The white reference data storage unit 20b includes an R white reference data storage unit 20b-r, a G white reference data storage unit 20b-g, and a B white reference data storage unit 20b-b. The R white reference data storage unit 20b-r stores R white reference data (R white reference data), and the G white reference data storage unit 20b-g stores G white reference data ( G white reference data) is stored, and B white reference data (B white reference data) is stored in the B white reference data storage unit 20b-b.

The black correction data calculation means (RGB black correction data calculation means) 21b supplies the voltage value (data when the light source is turned off) of the A / D conversion means 19 with the light source 13 turned off and the white reference data storage means 20b. Calculation is performed using the stored white reference data of each color of R, G, B, and black reference data of each color of R, G, B is created.
That is, the black correction data calculation unit 21b performs calculation using the light source extinction data from the A / D conversion unit 19 and the R white reference data stored in the R white reference data storage unit 20b-r. , R black reference data (R black reference data) is created. Further, an arithmetic operation is performed using the data when the light source is turned off from the A / D conversion means 19 and the white reference data for G stored in the white reference data storage means 20b-g for G, and the black reference data for G (G Black reference data). Further, a calculation is performed using the data when the light source is turned off from the A / D conversion means 19 and the white reference data for B stored in the white reference data storage means 20b-b for B, and the black reference data for B (B Black reference data).
The black reference data of R, G, B colors obtained by these arithmetic processes is sent to and stored in the black reference data storage means 22b.

  The black reference data storage unit 22b includes an R black reference data storage unit 22b-r, a G black reference data storage unit 22b-g, and a B black reference data storage unit 22b-b. The R black reference data storage unit 22b-r stores R black reference data, the G black reference data storage unit 22b-g stores G black reference data, and the B black reference data. The black reference data for B is stored in the data storage unit 22b-b.

Next, the operation (shading correction data creation method) of the image reading apparatus of this embodiment will be described with reference to FIG.
This figure is a flowchart showing the operation procedure of the shading correction data creation method of the present embodiment.

On the platen glass 11 of the image reading apparatus 1a, a white reference document 12 is placed with the reading surface facing down.
First, in order to create white reference data for each color of R, G, B for shading correction, the white light source 13 is turned on under the control of the control means 23 (step 20). The white reference document 12 is irradiated with light emitted from the light source 13 by this lighting. The irradiated light is reflected by the white reference document 12, and the reflected light is captured by the image pickup means 16 through the mirrors 14-1 to 14-3 and the lens 15, converted into an analog signal, and output. It is converted into a digital signal by the conversion means 19 (reading of a white reference original, step 21).
The R white reference data output from the A / D conversion means 19 is stored in the R white reference data storage section 20b-r of the white reference data storage means 20b (step 22).

Here, it is determined whether or not white reference data for all the colors R, G, and B has been created (step 23).
As a result of the determination, when the white reference data for all the colors of R, G, and B has not been created, the white reference data for the color that has not been created is created. When the white reference data for G is created, it is stored in the white reference data storage unit 20b-g for G of the white reference data storage means 20b, and when the white reference data for B is created, it is stored in the white reference data storage means 20b. It is stored in the white reference data storage unit for B 20b-b.

On the other hand, when the white reference data of all the colors R, G, and B are created, the white light source 13 is then turned off under the control of the control means 23 to create black reference data (step 24).
Then, the analog signal output from the imaging means 16 is converted into a digital signal by the A / D conversion means 19 (reading of the white reference chart, step 25).

In the black correction data calculation means 21b, the digital signal output from the A / D conversion means 19 is input, and the R data stored in the R white reference data storage section 20b-r of the white reference data storage means 20b. White reference data is extracted (obtain black reference data calculation data, step 26). Then, the R black reference data is calculated by the above-described equation 1 using the light source extinguishing data based on the digital signal and the R white reference data extracted from the R white reference data storage unit 20b-r. (Calculation, step 27).
The calculated R black reference data is stored in the R black reference data storage section 22b-r of the black reference data storage means 22b (step 28).

Here, it is determined whether or not black reference data for all the colors R, G, and B has been created (step 29).
As a result of the determination, if black reference data for all the colors R, G, and B has not been created, black reference data for a color that has not yet been created is created. When the G black reference data is created, it is stored in the G black reference data storage section 22b-g of the black reference data storage means 22b, and when the B black reference data is created, the black reference data storage means 22b. The black reference data storage unit 22b-b for B is stored.
When the black reference data for all the colors R, G, and B are created, the shading correction data creation method of this embodiment is finished.

With the above operation, even in a color image reading apparatus using a white light source and having photoelectric conversion elements for each color of R, G, and B, black reference data can be created with high accuracy without trouble.
Moreover, the light amount ripple of the light source is removed during shading correction from the signal output from the imaging means (image sensor) with the light source turned off and the white reference data when the white reference document is read with the light source turned on. Can be created.

Note that the shading correction data creation method of the image reading apparatus in each of the above embodiments can be executed by a computer controlled by a program. The program is provided by a recording medium, for example. As the recording medium, for example, a magnetic disk, an optical disk, a semiconductor memory, or any other means readable by a computer can be used.
Further, the program recorded on the recording medium can be loaded into the computer directly by the recording medium and read by the computer, or may be read by the computer via a communication line.

The preferred embodiments of the image reading apparatus and the shading correction data creating method of the present invention have been described above. However, the image reading apparatus and the shading correction data creating method according to the present invention are not limited to the above-described embodiments. It goes without saying that various modifications can be made within the scope of the present invention.
For example, in the above-described embodiment, a scanner, a facsimile machine, and a copying machine (copy machine) are described as examples of the image reading device. However, the image reading device is not limited to the scanner or the like, and is a composite device (MFP). For example, a device or a device having a function of reading an image from a document is included.

  Since the present invention relates to shading correction in an image reading apparatus, it can be used in devices and apparatuses that perform shading correction.

1 is a schematic side view illustrating a physical configuration of an image reading apparatus according to a first embodiment of the present invention. 2 is a block diagram illustrating a configuration of a control system of the image reading apparatus in the first embodiment. FIG. 3 is a flowchart illustrating an operation of the image reading apparatus according to the first embodiment. It is a curve diagram which shows each value of white reference data, light source extinction data, and black reference data obtained by the image reading apparatus. It is a block diagram which shows the structure of the control system of the image reading apparatus in 2nd embodiment of this invention. 10 is a flowchart illustrating an operation of the image reading apparatus according to the second embodiment. It is a perspective view which shows the external appearance structure of a light source.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Image reading apparatus 11 Original plate glass 12 White reference board 13 Light source 14 Mirror 15 Lens 16 Imaging means (image sensor, photoelectric conversion element)
Reference Signs List 17 device main body 18 moving body 19 A / D conversion means 20a, 20b white reference data storage means 21a, 21b black correction data calculation means 22a, 22b black reference data storage means 23 control means

Claims (6)

A light source for irradiating light to the white reference realization means, an imaging means for converting optical information in the main scanning direction on which the reflected light from the white reference realization means is imaged, and an electric power output from the imaging means An image reading apparatus comprising A / D conversion means for analog-digital conversion of a signal,
White reference data storage for storing, as white reference data, an electrical value of an output signal of the A / D conversion means when reflected light from the white reference realizing means is read by the imaging means with the light source turned on. Means,
A black reference data is generated by performing an operation using the electrical value of the output signal of the A / D conversion means when the light source is turned off and the white reference data extracted from the white reference data storage means. Correction data calculation means;
An image reading apparatus comprising: black reference data storage means for storing the black reference data. The electrical value of the output signal of the A / D conversion means in a state where the light source is turned off is used as data when the light source is turned off.
The black correction data calculation means is
The white reference data and the light source off-time data are added, the sum obtained by the addition is divided by a predetermined coefficient, the quotient obtained by the division and the light source off-time data are added, and this addition The image reading apparatus according to claim 1, wherein the sum obtained in the step is used as the black reference data. The white reference data storage means includes a plurality of white reference data storage units for storing the white reference data acquired for each of the plurality of colors for each of the colors;
The black correction data calculation means is extracted from the electrical value of the output signal of the A / D conversion means when the light source is turned off and the plurality of white reference data storage units of the white reference data storage means. Perform calculations using the white reference data for each color, create black reference data for each color,
The image reading apparatus according to claim 1, wherein the black reference data storage unit includes a plurality of black reference data storage units that store black reference data for a plurality of colors for each of the colors. The control means for executing lighting process of the light source, photoelectric conversion process in the imaging unit, and calculation process of black reference data in the black correction data calculation unit is provided. The image reading apparatus described. The image reading apparatus according to claim 1, wherein the imaging unit includes a one-dimensional image sensor and / or a two-dimensional image sensor. A procedure in which the light source irradiates light to the white reference realizing means, a procedure in which the imaging means converts optical information in the main scanning direction on which the reflected light from the white reference realizing means is imaged, and from the imaging means A method for generating shading correction data including a procedure in which an A / D converter performs analog-to-digital conversion on an output electrical signal,
The white reference data storage means uses the electrical value of the output signal of the A / D conversion means as white reference data when the reflected light from the white reference realizing means is read by the imaging means with the light source turned on. The procedure to remember,
The black correction data calculation means performs an operation using the electrical value of the output signal of the A / D conversion means in a state where the light source is turned off and the white reference data extracted from the white reference data storage means. The steps to create the baseline data,
And a black reference data storage means for storing the black reference data.

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