JP2002300394A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that is provided with a shading correction function adaptive to a high-speed reader and suppressing deterioration in an SPM to the utmost. SOLUTION: When a sheet-through type automatic draft feeder continuously carries an original, an exposure lamp luminous quantity of a 1st original is monitored to perform shading correction. Even when no shading correction is applied to 2nd succeeding originals, monitoring of the exposure lamp luminous quantity is performed for each reading of the original, and when a change of a preset change or more is detected in the process of the monitoring, shading correction is applied again. A density of a member carrying the original is read to monitor the exposure lamp luminous quantity for the 2nd and succeeding originals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
The present invention relates to an image reading apparatus mounted on a scanner, a facsimile or the like, and more particularly to an image reading apparatus having a function of monitoring a lighting state of a fluorescent lamp of the image reading apparatus.

[0002]

2. Description of the Related Art As shown in FIG. 5, an image reading apparatus 1 such as a digital copying machine applies light from a light source including an exposure (fluorescent) lamp 3 to a document placed on a contact glass 2 in a first and a second direction. There is provided a device for irradiating the second carriages 4 and 5 while scanning them, forming an image of reflected light from an original image by a lens 6, and reading the image by an image sensor (CCD) 7. In such an apparatus, a reference white plate 8 set as a white reference is first read immediately before reading a document as a white to be a reference of image density when reading the document, and shading data (step 601) as shown in FIG. ) Is generated, thereafter, the read image data and the shading data are calculated to perform shading correction (step 602), and thereafter, each image processing is performed and output. In FIG. 5, reference numeral 9 denotes an original scale, 10 denotes an SBU (Scanner Board Unit) on which the CCD 7 is mounted, and the first carriage 4 and the second carriage 5 are driven by a scanner motor 11. In this specification, the scanner refers to the first carriage 4 and the second carriage 5.

In reading an original, the exposure lamp 3 is turned on based on a start command of the scanner, and the first and fourth carriages 4 and 5 are driven at a preset speed. After the start of driving, first, a SHGATE signal is generated as a timing for reading the reference white plate 8, and in synchronization with this, white data of the reference white plate (hereinafter also referred to as white plate data) is read, and the first carriage 4 is moved to the document reading start position. Upon arrival, an FGATE signal is generated, and the original data is read in synchronization with the FGATE signal. After reading the document, the first and second carriages 4 and 5 return to their original positions, and stop at the designated original positions.

[0004] Due to the above operation, even when shading data becomes abnormal due to some influence, a series of document reading and image processing are performed, and eventually, an abnormal image is output. is there. One of the causes of the shading abnormality is a problem of rising light quantity. That is, when a rare gas fluorescent lamp with a small light quantity fluctuation is used as a reading light source (exposure lamp 3),
If the lamp is not used for a long time, the rise time of the lamp light amount becomes longer than usual. For this reason, a state occurs in which the light amount has not yet risen when the white data is read at the reference white plate position. Further, in the case of being left in the dark, such a problem of the amount of light appears more remarkably.

[0005] On the other hand, as this type of image reading apparatus, the inventions disclosed in JP-A-10-254074 and JP-A-10-200711 are known.

Japanese Patent Application Laid-Open No. Hei 10-254074 discloses an image reading apparatus using a fluorescent lamp as a document illumination lamp. Since the starting characteristics appear remarkably, the ordinary lamp O
It is disclosed that lighting is performed for a short time of about one second separately from the N trigger signal.

Japanese Patent Application Laid-Open No. 10-200711 discloses a method for obtaining an image having no density difference regardless of whether a document is fixedly read on a document table or read while moving the document on the document table. The disclosed image reading device is disclosed.

[0008]

In the conventional example described above, a document fixed scanner is very effective. However, in a document moving (sheet-through) type reading apparatus having a high reading productivity, it is always effective. Since shading could not be performed for each document, it was not possible to detect an exposure lamp abnormality during reading. That is, in the case of performing reading with a sheet-through type, in the case of a device (low-speed reader) with a low number of scans (SPM) capable of ensuring a sufficient time between documents, even if the conventional method or the conventional device described above is used. Implementation was possible.

However, in the case of a high-speed reader, the transport speed of a document is increased, and the reading speed is also increased accordingly. Also, by reducing the space between sheets, the SPM
To increase productivity. Moreover, in order to improve productivity, in the case of a high-speed reader, the time between sheets tends to be shorter. As a result, the shading operation (scanner driving) between sheets cannot be performed for each document.

The present invention has been made in view of such a technical background, and an object of the present invention is to provide a shading correction function capable of coping with a high-speed reader and suppressing a decrease in SPM as much as possible. The present invention provides an image reading device provided with the same.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a scanner movable along a document table, a function of fixing the scanner at a predetermined position, and moving and reading a document; Provide a reference white plate for shading correction at a different position from the optical system having a function of reading the reference white plate by moving the scanner to the reference white plate position during shading, and controlling the scanner,
A control unit for performing shading correction based on the data of the read reference white plate, wherein the control unit is configured such that when a document is continuously conveyed by a sheet-through type automatic document feeder, The shading correction operation is performed on the original document to monitor the exposure lamp light amount, and the exposure lamp light amount is monitored for the second and subsequent original documents regardless of the shading correction. When a change amount equal to or larger than the set change amount is detected, the shading correction operation is performed again.

In this case, the control means performs the same operation as the shading operation on the second and subsequent originals based on a signal generated corresponding to the time interval between the sequentially transmitted originals. The amount of light from the exposure lamp is monitored by reading the density of the member that conveys the image.

Further, the monitor of the light amount of the exposure lamp is based on the density of the member for conveying the original document between the sheets after the completion of reading the first original document as a reference value. This is performed by calculating the amount of change from the density of the member between the subsequent sheets.

Further, the change amount is determined as a change amount of an absolute value with respect to a reference value.

The apparatus further comprises means for arbitrarily setting the document feed interval. The means for arbitrarily setting the document feed interval has a function of arbitrarily setting the document feed interval during reading of a series of n documents. Configure as provided.

[0016]

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

<First Embodiment> FIG. 1 is a diagram showing an image reading apparatus and a reading operation timing according to an embodiment of the present invention. It is an example equipped. In this embodiment, two types of reading operations, ie, original fixing and original moving, are possible. FIG. 2 is a functional block diagram showing a control system of the image reading apparatus according to the first embodiment of the present invention.
7 is a timing chart showing output timing of each signal when reading by sheet-through.

The image reading device itself is the same as in FIG. However, the reading unit 12 is provided on the upstream side in the scanner movement direction for reading the image of the reference white plate 8, that is, on the left side in the figure, in order to read the document by sheet-through.

A sheet-through type automatic document feeder (hereinafter, referred to as ADF) 100 includes a document tray 101, a pickup roller 102, a transport drum 103, a transport roller 104, a paper discharge roller 105, and a paper discharge tray 106. It is attached to the upper surface of the device 1 so that it can be opened and closed. An original bundle before reading is placed on the original tray 101, and when the reading operation is started, the originals are picked up one by one from the upper surface of the original bundle by the pickup roller 102 and sent to the transport drum 103 side. A document is placed between a plurality of pairs of transport rollers 104,
And the conveying path 107 is sent to the reading unit 12 side, and is read by the reading unit.
The paper is discharged from a paper discharge roller 105 onto a paper discharge tray 106.

As shown in FIG. 2, the image reading device 1
Functionally, the image processing unit 201, the reading device unit 202,
And a sub-scan timing generator 203. The image processing unit 201 further includes a CPU 2010, a shading data generation / update unit 2011, a shading correction unit 2012, and an image data processing unit 2013.
Further, the reading device section 202 is provided with a main scanning timing generation section 2021.

The state in which the original is fixed to the contact glass 2 is the same as that described with reference to FIG. In the following description, asserting means starting a process by raising a signal, and negating means terminating the process by restoring a rising signal. The fact that the read white board data is normal means that the 8-bit image data is 255 on the white side and 0 on the black side.
This is a value close to 5.

Upon receiving the reading start information, the sub-scanning timing generator 203 resets the abnormality flag, turns on the exposure lamp 3 for reading, and sets the scanner motor 1
1, the scanner (first and second carriages 4,
5) is driven. When the first carriage 4 reaches the position where the reference white plate 8 is read, the SLEAD signal is asserted. While the SLEAD signal is asserted, the scanner reads the white data of the reference white plate 8 area and
, The white data 2011 read from the reference white plate 8 is transmitted, and the generation of shading data starts.

When the first carriage 4 comes out of the area of the reference white board 8 and comes to a position where the SLEAD signal is negated, the SLEAD signal is negated, and the sub-scan timing generator 203 takes in the white board data. If the captured white board data indicates a value close to white, the image reading process is continued as it is. When the scanner (the first carriage 4) comes to a position where the document is read, the SSCAN signal is asserted and the normal reading is performed. continue processing. If the captured white board data indicates a value that is not close to white, the SSCAN signal (FGATE signal) is not generated so that the processing of reading the original data is not performed.
This prevents abnormal image data from flowing to the image processing unit 201 and prevents output of an abnormal image.

In the case of moving the original, the original is set on the original tray 101 of the ADF 100 and the reading is started.
First, in order to perform shading, the first carriage 4 is driven to read the reference white plate 8 and returns to the reading position 12 for sheet-through again. After returning, Document Tray 1
01 is conveyed, and the original is read at the reading position 12. Shading correction is performed on the read data. In response to the return of the first carriage 4 to the reading position, the document starts to be conveyed again, and is sequentially read when passing through the reading position.

FIG. 2 shows a signal flow. Upon receiving the reading start information, the sub-scanning timing generation unit 204 drives the scanner motor 11 and outputs an SLEAD signal in the reference whiteboard reading area to the reading unit 202.
In response to this assertion, a signal corresponding to the actual whiteboard reading position is output to the image processing unit 201 as SHGATE with line synchronization. The image processing unit 201 reads the density of the reference white board 8 in the SHGATE signal section and generates shading data. When the shading operation is completed, the scanner returns to the sheet-through reading position.

Next, the ADF 100 receives the document transport start information and starts transporting the document set on the document tray 101. When the document reaches reading position 12
Output SSCAN signal. In the reading unit 202, the SSC
FGATE is output to the image processing unit 201 in line synchronization with the AN signal. The DFEND signal is negated when the trailing edge of the document has passed the reading position 12 after passing the document reading area. A * SHGT signal is generated for this edge and ANDed with SHGT. By doing this,
The reading device unit 202 can detect the density of the member that conveys the document from the time after the trailing edge of the document to the next document (between the sheets). This member is constituted by a white transport drum or a guide plate (not shown, but a guide plate for bringing a document into close contact with a glass window at a reading position) and capable of sufficiently detecting the density. With this control, the shading operation is performed as if it were past the trailing edge of the original. In this case, the shading data of the shading data can be monitored simply by monitoring the density of the member on the side that conveys the original. Do not update. In this control, reset is activated by assertion of the SLEAD signal, and DFEND
A signal for performing a preset operation with the signal is generated, and the shading data is updated based on the signal.

The monitor of the exposure lamp 3 for the first sheet is shown in FIG.
The shading operation is performed as shown in the timing chart of FIG. 7, and after the second sheet, the shading operation is performed as described above to detect the density of the member on the side that conveys the original as if it passed the rear end of the original. Monitor the state of the exposure lamp 3. If the result of monitoring is within the range of a change in the amount of light that does not affect the read image data, the shading operation is not performed. on the other hand,
If the light amount change is considered to have an effect on the image, the shading data is updated according to the read density.

The updating of the shading data is performed only when the reference white plate 8 is read. If the data obtained by the shading operation performed between sheets is not updated as the shading data, the exposure lamps of the second and subsequent exposure lamps are updated. The light amount monitor 3 is performed by forcibly executing the shading operation. However, it is necessary to prohibit the use of shading data generated by the shading operation for the second and subsequent sheets for correction of a document. As the control signal, a signal (or an information flag) for performing a preset operation by the assertion of the SLEAD signal and performing a preset operation by the DFEND signal is generated, and based on this, the shading data is updated and prohibited.

In the sheet-through reading in which the intermittent shading operation is performed, the above-described operation is performed for the first sheet, and the second and subsequent sheets are conveyed at a constant interval following the operation. When the shading operation is performed on the n-th document, the n-th document is stopped just before the document reading position after reading the (n-1) -th document. Also, n-
Immediately after reading the first sheet, the scanner starts driving to read the reference white plate. Upon completion of the reading and returning to the reading position, the n-th document is conveyed again, and is sequentially read thereafter. The above operation is repeated.

The shading is performed to correct a change in the reading level due to a change in the distribution characteristics of the light source in the main scanning direction and a change in the amount of light, a stain on the reference white plate, a stain on the mirror, and a stain on the contact glass of the reading unit due to aging. Shading performed for each document is mainly intended to cope with a change in lamp light amount. In addition, the light quantity stability from the start of lighting of the light source has individual differences (different for each light source) and is not a constant characteristic.

<Second Embodiment> In the first embodiment,
Although the shading data is intermittently updated every n sheets, it is not possible to cope with an abnormality in the light amount data within the range of n sheets. Therefore, in this embodiment, as shown in the flowchart of FIG. 4, the amount of change in the light amount data is monitored between sheets, and the shading data is updated when the amount of change exceeds an allowable range. FIG. 4 is a flowchart showing a processing procedure of such intermittent shading correction. Since the hardware configuration itself is the same as that of the above-described first embodiment, the same reference numerals are given to the same components, and the duplicate description will be omitted.

In the figure, after the trailing edge of the first document has passed, in other words, the reading of the first document has been completed.
While the second original is being transported to the reading position (between sheets)
Next, the density of the member that conveys the original is detected by the reading unit 202 (step 401). Since the detected data is data after the trailing edge of the first sheet has passed, the reference whiteboard 8 is read before reading the first sheet, and the shading data is updated based on the read value. The density of the member after the first sheet has passed is stored as a reference value as data (step 403). The density of reading the above member between the sheets of the second and subsequent originals is determined by CPU2.
At 010, the change is compared with the reference value to calculate the amount of change (step 404). In this calculation, for example, a change in the light amount is expressed in% with respect to the reference value, an amount of change in the light amount affecting the image is obtained in advance, and it is checked whether the change amount is within an allowable range (step 405) If the change amount is within the allowable range, the process returns as it is; if not, the reference value is updated (step 40).
6).

In order to update the reference value, an instruction is issued to stop the document feeding operation at the time when the value exceeds the allowable range (step 407). When the document feeding is stopped, the scanner is moved to perform shading correction. To read the reference white plate 8 (step 408). When this operation is completed (step 409), the shading data is updated based on the current intermittent shading correction operation. Then, an instruction to start document feeding is issued (step 41).
0), the operation returns to the normal document reading operation. Thereafter, by repeating this, reading of an abnormal image due to a change in light amount can be prevented.

The light amount stability (light amount change) of the light source is as follows.
There is no fixed direction for brightening or darkening. Therefore, the amount of change is treated as an absolute value.

Further, in the image reading apparatus 1, there is a definition of the number of sheets to be read (SPM: number of sheets to be scanned / minute) according to the size of the document. If intermittent shading is performed when there is not enough time to perform the shading operation between sheets, the SPM specification cannot be satisfied. Also, if intermittent shading is performed many times per minute, the result will be much lower than the SPM. As a countermeasure, when the intermittent shading operation is completed, in order to satisfy the SPM, a document feed interval for the remaining number of documents is calculated from the number of documents read so far and the time spent, and based on the result, Target SPM by feeding the original
Can be approached.

That is, SPM = K sheets Original conveyance speed = F (m / sec) In the case of the original size A4 width (= 0.21 m), if the original is read at an interval of 60 / K (sec), the specified SPM Can be satisfied. The inter-sheet time (B) in this case is B = (60 / K)-(0.21 / F) -A. Here, A is the extra time required for conveyance due to slippage of the document. The interval between sheets varies depending on the reader, but also includes a time for normally controlling the reader system.

If the shading operation can be performed between the sheets, the n-th and subsequent sheets are conveyed at the same document feed interval. However, if the time exceeds the paper interval, for example, n
When the shading operation is performed for the sheet (K> n), in order to satisfy the SPM, the document feed interval (T) for the nth and subsequent sheets is set as follows.

T = (60−Tn−1−Tshd) / (K−n + 1) where Tn−1 = reading time up to the (n−1) th sheet Tshd = time required for shading operation As described above, intermittent shading Is performed, by changing the document feed interval for subsequent documents, the specified S
It becomes possible to approach PM. When the intermittent shading is not performed on the K-th sheet, the specified SPM can be satisfied. However, if the intermittent shading is performed on the K-th sheet,
One SPM cannot be satisfied. If the time between the sheets can be further reduced, the SPM can be satisfied by performing a calculation in which one extra document is added as in the following equation.

T = (60−Tn−1−Tshd) / (K−n + 1 + 1)

[0040]

As described above, according to the present invention, when a document is continuously conveyed by the sheet-through type automatic document feeder, the light amount of the exposure lamp is monitored for the first document. The shading correction operation is performed, and the amount of light of the exposure lamp is monitored for each of the second and subsequent originals each time the original is read, and when a variation greater than a preset variation is detected during the monitoring process, shading is performed again. Since the correction operation is performed, the shading correction can be performed intermittently only when necessary, it is possible to cope with a high-speed reader, and the decrease in SPM can be suppressed as much as possible.

Further, according to the present invention, the same operation as the shading operation is performed on the second and subsequent originals based on a signal generated corresponding to the time interval between the sequentially transmitted originals. Because the density of the member that conveys the document is read and the amount of the exposure lamp is monitored, the time for reading the reference white plate is unnecessary for the second and subsequent documents, and the SP is not necessary.
M does not decrease.

Further, according to the present invention, the monitor of the light amount of the exposure lamp is based on the density of the member on the side of transporting the original after the end of reading of the first original. Is calculated by calculating the amount of change from the density of the member between the sheets after the reading of each document is completed, so that the data of the member on the side of transporting the document monitored by the lamp abnormality detecting means conventionally used is used. , And appropriate intermittent shading can be performed at no cost.

Further, according to the present invention, since the detected change in density is determined as a change in absolute value with respect to the reference value, the change in light amount of the light source can be accurately determined, and the shading operation can be optimally performed. it can.

Further, according to the present invention, since the means for arbitrarily setting the document feed interval is provided, the document feed interval that is extended during the intermittent shading operation can be shortened after the intermittent shading operation. Thereby, the SPM of the reading device can be satisfied.

Further, according to the present invention, the means for arbitrarily setting the document feed interval has a function of arbitrarily setting the feed interval during reading of a series of n documents.
The SPM of the reading device during the document reading operation in which n sheets constitute one job can be satisfied by increasing the document feeding interval that is extended during the intermittent shading operation to the document feeding interval after the intermittent shading operation.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image reading apparatus according to an embodiment of the present invention and a timing of reading a document.

FIG. 2 is a block diagram illustrating an electrical configuration and a signal flow of the image reading apparatus according to the embodiment of the present invention.

FIG. 3 is a timing chart showing output timings of signals in FIG.

FIG. 4 is a flowchart illustrating a control procedure of an intermittent shading operation.

FIG. 5 is a diagram illustrating a configuration of a conventionally implemented image reading apparatus and a timing of reading a document.

FIG. 6 is a diagram showing a data flow during a shading operation in a conventional example.

[Explanation of symbols]

 Reference Signs List 1 image reading device 3 exposure lamp 4 first carriage 5 second carriage 7 CCD 8 reference white plate 11 scanner motor 12 reading position 100 sheet-through automatic document feeder (ADF) 201 image processing unit 2010 CPU 2011 shading data generation / update unit 2012 Shading correction unit 2013 Image data processing unit 202 Reading unit 2021 Main scanning timing generation unit 203 Sub scanning timing generation unit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (6)

[Claims] 1. A scanner movable along a platen, a function of fixing the scanner at a predetermined position, moving and reading an original, and a reference white plate provided at a position different from the predetermined position for shading correction. , When shading,
An image reading apparatus comprising: an optical system having a function in which a scanner moves to the reference white board position and reads the reference white board; and a control unit that controls the scanner and performs shading correction based on the read data of the reference white board. In the apparatus, when the sheet is continuously conveyed by a sheet-through type automatic document feeder, the control unit monitors a light amount of an exposure lamp for the first document and executes a shading correction operation. Even if the shading correction operation is not performed on the originals after the first sheet, the monitor of the exposure lamp light amount is executed every time each original is read, and a change amount equal to or larger than a preset change amount is detected in the process of this monitor. An image reading device for performing a shading correction operation again. 2. The control device according to claim 1, wherein the control unit performs the same operation as the shading operation on the second and subsequent originals based on a signal generated in accordance with a time interval between the sequentially transmitted originals. 2. The document reading apparatus according to claim 1, wherein the density of the member on the side to be conveyed is read and the light amount of the exposure lamp is monitored. 3. The monitor of the light amount of the exposure lamp,
Calculating the amount of change from the density of the member between the sheets after the reading of each of the second and subsequent originals, using the density of the member on the side of conveying the original after the end of the reading of the first sheet as a reference value. The image reading device according to claim 1, wherein the image reading is performed by performing the following. 4. The image reading apparatus according to claim 1, wherein the change amount is determined as a change amount of an absolute value with respect to a reference value. 5. The image reading apparatus according to claim 1, further comprising means for arbitrarily setting a document feeding interval. 6. The apparatus according to claim 4, wherein the means for arbitrarily setting the document feed interval has a function of arbitrarily setting the document feed interval during reading of a series of n documents.
An image reading device according to claim 1.