JP2006054820A - Image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct image data unevenness of a main scanning direction which occurs at the time of sheet through reading by a coefficient which is obtained by a predetermined method, and corrects white shading data at the time of the sheet through reading which performs in a position facing a reading position of a carriage through a draft. <P>SOLUTION: The device reads a white color roller 51 in a condition in which the draft is not set, obtains the main scanning data of several lines, averages these data of the main scanning data of several lines of the white roller in an average/smoothing processing circuit part 62, and makes them image data of a number of data for 1 line. Then, the device further calculates a running average of the main scanning direction of the data, creates white color roller reading data removing disturbance of data by noise, fine dust, dirt, etc., and holds them in a memory for a white shading data correction 63. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus mounted on a copying machine, in which background smearing, settling, and the like due to unevenness in the main scanning direction of an automatic document feeder are reduced.

In general, an image reading apparatus provided in a copying machine has two types of reading methods using a document placing table (hereinafter referred to as “BOOK reading”) and reading using an automatic document feeder (hereinafter referred to as “ADF reading”). There is.
In the ADF reading, a document to be copied is sent to a predetermined position and the carriage is moved to scan, and a type in which the carriage is fixed and the document is scanned (hereinafter referred to as sheet-through reading). ).
Normally, white reading correction is performed using the same white reference plate at the time of book reading and sheet through reading. However, since the white reference plate is positioned at the same height (on the plane) as the document table, at the time of book reading Is (image data distribution shape in the main scanning direction in the white reference plate area) = (image data distribution shape in the main scanning direction in the document area)
Thus, uniform image data output without unevenness can be obtained by shading correction as shown in FIG.
By the way, as a technique for correcting the shading correction data in different document reading units so that the brightness of the read document can be made almost equal regardless of the difference between the document reading units, the following patent document 1 describes. The invention can be given.

JP 2001-157052 A

On the other hand, in ADF reading, during sheet-through reading, a deviation in ADF mounting accuracy on the document table (see FIG. 4) or a deviation between the reading position determined by the carriage position and the reading center of the document (FIGS. 5 and 5). 6)
(Image data distribution shape in the main scanning direction in the white reference plate area) ≠ (Image data distribution shape in the main scanning direction in the document area)
Can happen. The image data output obtained in such a state is uneven in the main scanning direction as shown in FIG.
As described above, an appropriate read image can be obtained at the time of BOOK reading, but an abnormal image such as background smearing or setback can be caused at the time of sheet-through reading.

Accordingly, a first object of the present invention is to provide a coefficient for correcting white shading data obtained by a predetermined method at the time of sheet-through reading positioned opposite to the reading position of the carriage and the document against such a phenomenon. Accordingly, it is an object of the present invention to provide an image reading apparatus that corrects unevenness in image data in the main scanning direction that occurs during sheet-through reading.
The second object of the present invention is to read the data distribution in the main scanning direction by reading a white paper with uniform density using ADF for the data unevenness in the main scanning direction at the time of sheet-through reading. It is another object of the present invention to provide an image reading apparatus that obtains a coefficient for correcting white shading data obtained by reading a white reference plate and corrects image data unevenness in the main scanning direction that occurs during sheet-through reading.
A third object of the present invention is to obtain a user even in the case of market installation by preparing a calibration mode from a user I / F such as an operation unit to obtain a coefficient for correcting white shading data. It is an object of the present invention to provide an image reading apparatus that can easily correct data unevenness in the main scanning direction during sheet-through reading depending on the state of an image.

  According to the first aspect of the present invention, reading means for reading a document placed on a document placing table or an automatic document feeder, white shading data generating means for generating white shading data based on reading data of a white reference plate, An image reading apparatus that performs white shading correction on image data read by the reading unit using the white shading data generated by the white shading data generation unit, wherein the original is conveyed by the automatic document conveying device The main scanning when the original is conveyed by the automatic document feeder by exposing the white roller with the path, the white roller arranged to be opposed to the reading position with the position fixed with respect to the conveyed document, and the white roller. Direction image output distribution data is obtained, and the distribution data is subjected to a process such as smoothing, and is used to perform the automatic document feeder. Further comprising a white shading data correction means for correcting the white shading data when read by the, to achieve the first object.

  In the invention described in claim 2, a reading unit that reads a document placed on a document placing table or an automatic document feeder, a white shading data generation unit that generates white shading data based on reading data of a white reference plate, An image reading apparatus that performs white shading correction of image data read by the reading unit using white shading data generated by the white shading data generation unit, and has a certain reflection surface on the entire surface of the automatic document feeder. The image output distribution data in the main scanning direction on the automatic document feeder side is obtained by reading the document of the rate, and the distribution data is subjected to a process such as smoothing, and is used by the automatic document feeder. By providing white shading data correction means for correcting white shading data at the time of reading, the second shading data correction means is provided. To achieve the target.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the white shading data correcting means obtains a coefficient for correcting white shading data when read by an automatic document feeder. The third object is achieved by allowing the user to adjust the operation mode via the user interface of the operation unit.

  According to the first aspect of the present invention, the roller that controls the conveyance of the document at the time of sheet-through reading positioned opposite to the reading position of the carriage and the document is white, and the white roller is exposed to expose the main roller at the time of sheet-through reading. Since the coefficient for correcting the white shading data obtained by acquiring the data distribution in the scanning direction and reading the white reference plate based on the obtained data distribution is obtained, the image data unevenness in the main scanning direction that occurs during sheet-through reading is corrected. In addition, abnormal image output such as background smearing and setback during sheet-through reading can be prevented.

  According to the second aspect of the invention, an automatic document feeder is used to read a white paper with a uniform density, and at that time, a data distribution in the main scanning direction at the time of sheet-through reading is obtained, and based on this, a white reference plate is obtained. By obtaining a coefficient that corrects the white shading data obtained by reading the image and correcting the image data unevenness in the main scanning direction that occurs during sheet-through reading, abnormal image output such as background stains and back-off during sheet-through reading Can be prevented.

  In the invention of claim 3, since the correction of the main scanning level unevenness when using the automatic document feeder can be performed from the user I / F of the operation unit or the like, the user or the like can perform the correction according to the image output state obtained by himself / herself. Correction can be applied.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a diagram showing an image reading apparatus according to the present embodiment.
The image reading apparatus shown in FIG. 1 reads an image with a photoelectric conversion element (CCD), converts the image signal into a digital signal, and performs processing. The image reading apparatus includes a first carriage 39 including a contact glass 34 on which a document 47 is placed, a xenon lamp 35 for document exposure, and a first reflection mirror 36, a second reflection mirror 37, and a third reflection mirror 38. A second carriage 40, a lens unit 41 for forming an image on a CCD linear image sensor 42 (hereinafter referred to as a CCD), and a white reference plate 48 for correcting various distortions caused by a reading optical system or the like.

During scanning, the first carriage 39 and the second carriage 40 are moved in the sub-scanning arrow A direction by a stepping motor. In the figure, reference numeral 49 denotes an automatic document feeder (hereinafter referred to as ADF scanning) that serves both as a document presser on the document table of the image reading apparatus and a plurality of document conveying functions.
The document 47 set on the document placement portion of the ADF is transported to the sheet-through reading slit 50 and then transported in the direction of arrow B therefrom. The original surface to be conveyed is scanned at a position directly below the sheet-through reading slit 50 while the first carriage is stopped. In this embodiment, the roller is a white roller 51 having a uniform density.

FIG. 2 is a block diagram showing a signal processing procedure from the output of a CCD linear image sensor (hereinafter referred to as CCD) 42 to obtaining a digital image signal. First, image signals VE and VO are output from the CCD 42 in synchronization with the drive pulse, and the image signal VE and VO are sampled and held by the sample hold circuit 52 by the sample hold circuit 52, whereby the image signal is converted into a continuous analog signal. The level correction circuit unit 53 corrects variations in the dark output level of the CCD 42. Thereafter, the output of the odd and even pixels is multiplexed in the multiplex circuit 54 to become an image signal V.
The image signal V is amplified to the level of the reference voltage for A / D (analog / digital) conversion by the amplifier circuit 55 and converted into 8-bit digital data by the A / D conversion circuit 56. The digital image signal thus obtained is read by the CCD 42 with the reflected light of the white reference plate 48 irradiated by the xenon lamp 35 in the shading correction circuit 57. In this way, a predetermined density level is obtained, the sensitivity variation of the CCD 42 and the light distribution unevenness of the irradiation system are corrected, and further the digital processing such as γ correction is performed by the γ correction circuit unit 58 at the subsequent stage.
Signals necessary for driving the CCD 42 and other circuits are generated by a timing signal generation circuit 60 based on an oscillator (OSC) 59 on a signal processing unit 45 and input to each circuit unit.

Next, correction of image data unevenness in the main scanning direction during sheet-through reading will be described.
First, the first carriage 39 turns on the lamp at the sheet-through document reading position, reads the white roller 51 without passing the document, and acquires main scanning data for a plurality of lines. In the averaging / smoothing processing circuit unit 62, these data are averaged in the line direction (sub-scanning direction) for the plurality of lines of the white roller to form image data of the number of data for one line. Thereafter, a moving average of the data in the main scanning direction is further calculated to generate white roller read data from which data disturbance due to noise, fine dust, dirt, etc. has been removed, and held in the white shading data correction memory 63. .

Subsequently, when reading the sheet-through original, the first carriage 39 turns on the lamp, moves under the white reference plate 48, acquires the data of the white plate area, and moves the first carriage 39 to the sheet-through reading slit 50. Move below. The original document that is automatically conveyed is read, but the data acquisition of the white plate area is actually performed as follows.
First, the white reference plate 48 is read to obtain main scanning data for a plurality of lines. This is averaged in the line direction inside the shading correction circuit 57 to obtain image data of the number of data for one line. This processing procedure is shown in FIG. This data becomes white shading data when the BOOK reading is actually read.

When reading through a sheet-through document, the following correction is applied to the white shading data.
First, the peak value Xpeak is extracted from the white shading data Xn, and the white roller reading data Ypeak corresponding to the main scanning direction address is extracted.
Next, the ratio of each of the white shading data and the white roller data to Xpeak and Ypeak is calculated.
White roller data peak ratio: Yn / Ypeak
White shading data peak ratio: Xn / Xpeak
Using these, the shading data Sn at the time of reading the sheet-through document is calculated as follows.
Sn = ((Yn / Ypeak) / (Xn / Xpeak)) * Xn
Then, by performing a shading operation on the ADF document data Dn, as shown in FIG. 9, it is possible to obtain an image output in which unevenness in the main scanning direction at the time of reading the ADF document is corrected.
The ADF document read image data is = Dn / Sn * 255.
Further, the generation of the white roller data can be executed by the user as the ADF calibration mode from the user I / F such as the operation unit 64 according to the obtained image output state.

Next, a second embodiment will be described. In the first embodiment, the white roller 51 is exposed and white shading data is corrected from the data. However, instead of the white roller 51, sheet-through reading is performed using a white paper with a uniform density as a whole. Even if the correction value of the white shading data is obtained from the read data, an equivalent effect can be obtained.
In this case as well, as in the first embodiment, the user can execute the ADF calibration mode from the user I / F such as the operation unit in accordance with the obtained image output state.

It is the figure which showed the image reading device which converts the image signal into a digital signal and processes it based on this Embodiment. It is the block diagram which showed the procedure of the signal processing until it obtains a digital image signal from CCD output. FIG. 6 is a diagram illustrating that a white paper having a uniform density is read as an original. FIG. 5 is a diagram showing a deviation in the accuracy of ADF attachment to the document table during sheet-through reading. FIG. 6 is a diagram illustrating that the carriage position is in an ideal state, so that uniform image output is performed. FIG. 10 is a diagram illustrating uneven image output because the carriage position is shifted. FIG. 5 is a diagram illustrating that a blank sheet with uneven density is read as a document. It is the figure which performed the averaging process in the line direction inside the shading correction circuit part, and showed the image data of the data number for 1 line. FIG. 6 is a diagram illustrating that a white paper having a uniform density is read as an original.

Explanation of symbols

34 Contact glass 35 Xenon lamp 36 First reflection mirror 37 Second reflection mirror 38 Third reflection mirror 39 First carriage 40 Second carriage 41 Lens unit 42 CCD linear image sensor 43 Sensor board 44 Signal cable 45 Signal processing section 46 Scanner body 47 Document 48 White reference plate 49 Automatic document feeder 50 Sheet-through reading slit 51 White roller 52 Sample hold circuit 53 Black level correction circuit unit 54 Multiplex circuit 55 Amplification circuit 56 A / D conversion circuit 57 Shading correction circuit 58 γ correction Circuit part 59 Oscillator (OSC)
60 Timing Signal Generation Circuit Unit 62 Average / Smoothing Processing Circuit Unit 63 White Shading Data Correction Memory 64 Operation Unit

Claims (3)

Reading means for reading a document placed on a document placing table or an automatic document feeder;
White shading data generating means for generating white shading data based on the reading data of the white reference plate;
An image reading apparatus that performs white shading correction of image data read by the reading unit using white shading data generated by the white shading data generation unit,
A document transport path through which the document is transported by the document auto-conveying device, a white roller disposed at a position opposite to the reading position with a position fixed to the transported document,
The image output distribution data in the main scanning direction when the white roller is exposed and the original conveyed by the automatic document feeder is read is obtained, and the distribution data is subjected to processing such as smoothing, and then used. An image reading apparatus comprising white shading data correction means for correcting white shading data at the time of reading by the automatic document feeder. Reading means for reading a document placed on a document placing table or an automatic document feeder;
White shading data generating means for generating white shading data based on the reading data of the white reference plate;
An image reading apparatus that performs white shading correction of image data read by the reading unit using white shading data generated by the white shading data generation unit,
In the automatic document feeder, by reading a document having a certain reflectance on the entire surface, image output distribution data in the main scanning direction on the automatic document feeder side is obtained, and processing such as smoothing the distribution data is performed. An image reading apparatus comprising: a white shading data correcting unit that corrects white shading data when read by an automatic document feeder using the automatic document feeder. A calibration mode for acquiring a coefficient for correcting white shading data when read by an automatic document feeder by the white shading data correction means can be adjusted by a user via a user interface of an operation unit. The image reading apparatus according to claim 1.

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