JP2002305633A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that improves productivity of document image reading by performing correction only with one white reference plate and shortening a reading interval of each original. SOLUTION: When the image reader 1 reads a plurality of originals (S21 to S26) with reading in a second reading mode (S10; Y), the image reader 1 obtains both a time for reading the originals and a time that elapses from the preceding shading end, and performs shading correction (S22) before reading the originals (S21 to S24) only when the times surpass a period T for guaranteeing a correction allowable range to be reference for performing shading correction (S27; Y). If the both the time for reading the originals and the time that elapses from the preceding shading end are not longer than the period T (S27; N), the originals are read without performing shading correction (in and after S24).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly, to an image reading apparatus for reading an original while the original scanning means passes through a predetermined exposure position of the contact glass while the exposure scanning unit is fixed at the exposure position. The present invention relates to an image reading apparatus in which the shading correction in the reading mode is performed based on a period T that guarantees an allowable range of the correction.

[0002]

2. Description of the Related Art Conventional image reading apparatuses of this type include:
An apparatus is provided as an apparatus for converting a document image read by a relative movement between an exposure unit and a document into an electric signal using a light receiving element. In this image reading apparatus, there are two types of relative movement between the exposure unit and the document. The first method is a first reading mode in which an exposure scanning unit scans and reads a document placed on a contact glass. In the second method, a document is read in a state where the exposure scanning unit is fixed at the exposure position while the document is passed through a predetermined exposure position of the contact glass by the document transport means.
Reading mode. In the image reading apparatus as described above, when the original image is read by the light receiving element, shading correction is performed to correct variations in the illuminance of the exposure lamp, which is a light source, in the main scanning direction and changes in the amount of light due to elapse of the lighting time. Has been done. This "shading correction"
Means that every time a document is read, a white reference plate, which is a reference for white density, is read, and based on the read data of the white reference plate,
Correcting an electric signal of a document image output from the light receiving element. A specific method of the shading correction requires a process of once moving the exposure scanning unit to the white reference plate after reading the document, returning the exposure scanning unit to the reading position after reading the white reference.
For this reason, until the shading correction is completed, it is not possible to shift to reading of the next original, and for that time,
There has been a problem that the productivity of image reading (the number of originals read per time) decreases.

Therefore, if the exposure scanning unit is moved to the white reference plate and then moved back to the reading position, the time required for shading can be reduced by increasing the moving speed. There is a problem that there is a limit due to the mechanical operation, for example, the displacement of the exposure scanning unit is likely to occur. In order to solve such a problem, Japanese Patent Application Laid-Open No. 6-28
Japanese Patent No. 4284 (first prior art) or Japanese Patent Application Laid-Open No. Hei 8-9116 (second prior art) has been proposed. The first conventional technique is to read a plurality of originals before reading.
Based on the value corrected by the white reference plate, the correction is performed by the sub white reference plate installed at the reading position. In the second related art, the correction is performed by reading the data of the sub white reference plate by driving the reflection mirror every reading based on the value corrected by the white reference plate.

[0004]

However, in the first prior art, the variation in the main scanning direction cannot be accurately corrected because the sub-reference plate is located only in a part outside the reading range. On the other hand, in the second conventional technique, although the variation in the main scanning direction can be corrected,
Since the mirror needs to be driven, a mechanical operation of returning the mirror to the state at the time of reading after moving the mirror in the direction for reading the sub-reference plate is required, and there is a limit to shortening the time. . In addition, since both the first and second prior arts have two white reference plates, they deviate from the original correction values as the number of sheets to be read increases.

Accordingly, an object of the present invention is to improve the productivity of image reading of a document by shortening the reading interval for each document while performing correction using only one white reference plate. A reading device is provided.

[0006]

According to the first aspect of the present invention, there is provided a first reading mode in which an original placed on a contact glass is scanned and scanned by an exposure scanning unit, and the original is contacted by original transport means. A second reading mode in which the exposure scanning unit is read in a state where the exposure scanning unit is fixed to the exposure position while passing through a predetermined exposure position of the glass, and an electric signal of a document image read in each of the reading modes is obtained. In reading in the second reading mode, when reading a plurality of documents, a reading time of the documents and a time elapsed from the end of the previous shading are obtained, and the time is used as a reference for performing shading correction. The shading correction is performed before reading the original only when the allowable range is exceeded for the period T. By having a control means for causing the document reading without ring correction, to achieve the above object. According to the present invention, the shading correction is performed every time the document is read only when the reading time of the document and the time elapsed from the end of the previous shading exceed the period T in which the allowable correction range is guaranteed. Is not performed, accurate correction using one reference plate can be performed, and the productivity of document reading can be improved. According to the second aspect of the present invention,
In the description, the control unit is configured to allow the user to set the period T. According to a third aspect of the present invention, in the first aspect, the control means includes:
It is characterized in that the period T can be set on the basis of an image quality that the user can accept.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to FIGS. 1 to 4 are diagrams for explaining an embodiment of the present invention. FIG. 1 is a diagram showing an image reading apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view showing the vicinity of the white reference plate of the main part of the image reading apparatus according to the embodiment of the present invention. In these figures, an image reading apparatus 1 according to an embodiment of the present invention is an apparatus that converts a document image read by a relative movement between an exposure unit 3 and a document into an electric signal using a light receiving element 5 such as a CCD. In addition, two reading modes are provided depending on the type of relative movement between the exposure unit 3 and the document. The first reading mode is also called a book reading mode, and the exposure scanning unit 3 can scan and read a document placed on the book reading contact glass 7a. The second reading mode is also referred to as a sheet-through reading mode, in which the original scanning unit 3 is fixed to the exposure position P1 while the original is passed by the original conveying means 9 through a predetermined exposure position P1 of the sheet-through contact glass 7b. It can be read.

In the image reading apparatus 1, the book reading contact glass 7a and the sheet through contact glass 7b are arranged in parallel as shown in FIGS. 1 and 2 so as to form a single flat glass. It is arranged. As shown in FIGS. 1 and 2, an exposure unit 3 is disposed at a sheet-through reading position (exposure position) P1 below the sheet-through contact glass 7b. The exposure unit 3 includes a traveling body 31, a lamp 32 provided inside the traveling body 31, and a mirror 33 provided inside the traveling body 31. The contact glass 7a for sheet-through and the contact glass 7b for sheet-through can be reciprocated in parallel while maintaining a certain distance. Further, a mirror 11a is provided at the upper right side of the drawing on the right end of the contact glass 7a for book reading.
b is provided below the mirror 11a. The mirrors 11a and 11b are connected to the mirror 33 in the traveling body 31 of the exposure unit 3 by the contact glass 7 for book reading.
a or an original image read from an original on the sheet-through contact glass 7b can be guided to the light receiving element 5. As shown in FIGS. 1 and 2, a white reference plate 13 is disposed at a lower portion of the joint between the book glass 7a and the sheet-through contact glass 7b.

The document feeder 9 includes an automatic document feeder 90, a document table 91, a feed roller 92, and a guide roller 9.
3, a paper discharge roller 94, and a document collection table 95. The document conveying means 9 transfers the document placed on the document table 91 to a document.
When the original is transported, the original feed roller 92 is driven to take in the original, the guide roller 93 guides the original onto the book reading contact glass 7 a, and the discharge roller 94 collects the original.
5 can be discharged. The light receiving element 5 is connected to the control device 15 and takes in the electric signal of the document image read from the light receiving element 5 to form a copy signal. The control device 15 includes the light receiving element 5
A reading unit 151 that takes in an electric signal of a document image read from a printer, and a control processing unit 152 that performs various image processing, drive control, shading determination processing, and the like.
And a drive unit 153 for controlling the operation of the document conveying means 9 and the exposure unit 3, and a control panel 154 capable of inputting a data display and a scan command. Also,
Although not shown, the control processing unit 152 includes, for example, a central processing unit (CPU) that executes various types of arithmetic processing, a RAM used by the CPU to perform arithmetic processing,
ROM storing an image reading program and other control programs to be processed by U, and various data between external devices (the reading unit 151, the driving unit 153, the control panel 154, and other devices) and the CPU. And an input / output interface for exchanging various control signals.

[0010] To further explain, the image reading apparatus 1
The traveling body 31 is fixed at the sheet-through reading position (exposure position) P1, and is read by passing a document placed on the sheet-through contact glass 7b in a sheet-through reading mode, or on the book-reading contact glass 7a. The document is read in a book reading mode in which the document is read by moving the traveling body 31 under a fixed document at a constant speed. In the book reading mode, the control device 15 of the image reading apparatus 1 reads the white reference plate 13 when the traveling body 31 reaches the white reference plate reading position P2 while moving below the book reading contact glass 7a. To perform shading correction. Further, in the sheet-through reading mode, the control device 15 of the image reading apparatus 1 temporarily moves the traveling body 31 to the white reference plate reading position P2 below the white reference plate 13 before passing the document to the reading position. By reading the white reference plate 13, shading correction is performed. afterwards,
The controller 15 returns the traveling body 31 to the sheet-through reading position (exposure position) P1, and allows the document to be read by passing the document over the sheet-through contact glass 7b by the document conveying means 9. It has become.

In the image reading apparatus 1 of the present invention, shading correction is usually performed using the same white reference plate 13 in the book reading mode and the sheet through reading mode, so that the book reading mode and the sheet through reading mode can be used. Whichever image is read, there is no difference in image quality. Further, the control processing unit 152 of the control device 15
When the PU processes the image processing program in the ROM, the sheet through reading mode (second reading mode) is performed.
When reading multiple documents,
The reading time Tr of the document and the time Ta elapsed from the end of the previous shading are obtained, and the obtained time (Tr +
A period during which Ta) guarantees a correction allowable range that serves as a reference for performing shading correction (hereinafter, “correction allowable range guarantee period”)
Only when the time exceeds T, the shading correction is performed before reading the original, and the time (Tr + Ta)
The control means for reading the original without performing the shading correction when does not exceed the correction allowable range guarantee period T is realized.

Control means for executing or not executing the shading correction by the control device 15 will be further described with reference to FIG. FIG. 3 is a characteristic diagram showing a temporal change characteristic of an output of a lamp used in a control method adopted by the image reading apparatus according to the embodiment of the present invention;
The time t is plotted on the horizontal axis, and the light quantity Wt of the lamp is plotted on the vertical axis. First, the traveling body 3 of the exposure unit 3
Assuming that the output (light amount) of the lamp 32 installed in the unit 1 is Wt, the lamp output Wt changes with time t as shown in FIG. In the present invention, when the output (light amount) of the lamp 32 when the shading correction is performed is W1 and the error value of the allowable output (light amount) is Δw using the output characteristics of the lamp 32, An allowable time T (a period during which the error Δw is within an allowable range from the end of the shading correction) T in which the output Wt of the data is within the range (W1−Δw) is obtained in advance, and this is stored in the ROM of the control processing unit 152 of the control device 15. It shall be set. Then, the control processing unit 15 of the control device 15
2 realizes means for calculating the time Tr required for reading from the size of the document to be read and the speed of document conveyance, and the time Ta elapsed from the end of the previous shading, by processing the image processing program in the ROM by the CPU. I have. In addition, the control processing unit 152 of the control device 15
By the PU processing the image processing program in the ROM, a judging means for judging whether or not the time (Tr + Ta) obtained by the above means exceeds a correction allowable range guarantee period T which is a reference for performing shading correction is realized. I have. The determination means in the control device 15 determines the time (T
When it is determined that (r + Ta) exceeds the correction allowable range guarantee period T serving as a reference for performing shading correction, the control device 15 implements means for performing shading correction before reading the document.

The operation of the image reading apparatus 1 configured as described above will be described with reference to FIGS. 1 to 3 and FIG. FIG. 4 is a flowchart for explaining the operation of the image reading apparatus according to the embodiment of the present invention. First,
When the reading is started, the control processing unit 152 of the control device 15 checks whether or not the sheet-through reading mode is being performed while the document is being conveyed (step 10). This control processing unit 152
When the mode is not the sheet-through reading mode (step 10; N), it is determined that the mode is the book reading mode, and the book reading mode after step 12 is entered. Control processing unit 152
Controls the driving of the driving unit 153 and
Is moved to the original side (step 12).
When detecting that the traveling body 31 of the exposure unit 3 has reached the white reference plate reading position P2, the control processing unit 152 causes the light receiving element 5 to read the white reference plate 13, and
Is read in via the reading unit 151, and shading correction is performed (step 13). The control processing unit 152 controls the driving of the drive unit 153, and
1 is further moved as it is to read the original on the book reading contact glass 7a (step 1).
4). That is, the control processing unit 152 captures the image detection signal from the light receiving element 5 via the reading unit 151. When the reading is completed, the control processing unit 152 controls the driving of the drive unit 153 to return the traveling body 31 to the standby position (sheet-through reading position (exposure position)) P1 (step 15). Here, when the traveling body 31 of the exposure unit 3 moves to the standby position (sheet-through reading position (exposure position)) P1, the control processing unit 152 proceeds to step S16. The control processing unit 152 determines whether to perform the scan again (step 16). Here, when the control processing unit 152 determines that the reading has not been completed (Step 16; N), the process returns to Step 12, and executes the reading process again. When the control processing unit 152 determines that the reading is completed (Step 16; N), the reading is completed.

On the other hand, when the control processing section 152 determines that the mode is the sheet-through reading mode (step 10;
Y), reading is performed in the sheet through reading mode after step 21. That is, the control processing unit 152 drives and controls the drive unit 153 to move the traveling body 31 of the exposure unit 3 to the white reference plate reading position P2 (step 2).
1). The control processing unit 152 controls the traveling unit 3 of the exposure unit 3.
1 is moved to the white reference plate reading position P2, the read image from the white reference plate 13 is given to the light receiving element 5, the signal from the light receiving element 5 is taken in via the reading unit 151, and the shading correction is executed (step). 22). The control processing unit 152 drives and controls the drive unit 153, and after the correction is completed, returns the traveling body 31 of the exposure unit 3 to the sheet-through reading position (exposure position) P1 (step 23). Thereafter, the control processing unit 152 drives and controls the document conveying means 9 by driving and controlling the drive unit 153,
The original is conveyed from the original table 91 to the sheet-through contact glass 7b (step 24), and the original is passed through the sheet-through reading position (exposure position) P1 to give an image to the light receiving element 5 and read the image (step 24). 2
5). After reading one document, the control processing unit 152 determines whether there is still another document to be read (step 26), and when the reading is completed (step 26;
Y), the reading operation ends. The control processing unit 152
If the reading is not completed in the determination as to whether or not there is a document to be read (step 26; N), the necessity / unnecessity of shading correction is determined (step 27).

The means realized by the control processing unit 152 determines the necessity / unnecessity of shading correction, firstly, the time Tr required for reading based on the size of the document to be read and the speed of document conveyance, and the time from the end of the previous shading. The elapsed time Ta is calculated, and a process of adding them is executed. Next, the control processing unit 15
2, the determining means realized by the time (T
It is determined whether or not (r + Ta) exceeds a correction allowable range guarantee period T serving as a reference for performing shading correction. When the determination unit of the control processing unit 152 determines that the time (Tr + Ta) obtained by the unit exceeds the correction allowable range guarantee period T serving as a reference for performing shading correction (step 27; Y), the control processing is performed. The unit 152 returns to the process of Step 21. Thereby, the control processing unit 152
Performs the shading correction before the step of reading the original (step 24) by executing the processing of steps 21 to 22 to 23.

On the other hand, when the determining means realized by the control processing unit 152 determines that the time (Tr + Ta) obtained by the above means is within (within) the correction allowable range guarantee period T serving as a reference for performing shading correction. (Step 27; N), Step of Reading the Original (Step 2)
The process proceeds to 4), and the next document is read without performing shading correction. Thereby, the control device 15
Eliminates the need to issue a command to move the traveling body 31 of the exposure unit 3 to the white reference plate reading position P2,
The document reading operation can be started immediately. As described above, according to the embodiment of the present invention, when the error range is allowable, the shading correction is not performed, so that the time required for reading the next document can be reduced (steps 21 to 23 can be reduced), and the document reading can be performed. Productivity can be increased.

In the embodiment of the present invention, the correction allowable range guarantee period T serving as a reference for performing shading correction is shown in FIG.
As shown in FIG.
Is obtained, and the output characteristic is set as the correction allowable range guarantee period T which is a reference value for performing shading correction. However, in another embodiment of the present invention, the control panel 154 The correction allowable range guarantee period T
Can be arbitrarily set by the user or can be set as desired. In another embodiment of the present invention, which will be described with reference to FIGS. 1 to 4, in the image reading apparatus 1 according to the other embodiment, the control processing unit 152 of the control device 15 includes a control panel. Since the determination of step 27 in FIG. 4 is made based on the correction allowable range guarantee period T set arbitrarily or as desired by the user in 154, the user waits until the next shading correction is performed after the completion of the shading correction. Can be set freely. However, in other embodiments of the present invention, depending on the user, the image quality of reading may not be a problem, and the productivity of reading may be emphasized. , The control panel 154 can set the period T to be large. Of course, when the image quality is more important than the productivity, the period T can be set to be small in the control panel 154, so that it is possible to flexibly respond to the user's request.

According to still another embodiment of the present invention,
The setting of the period T for guaranteeing the reference value for performing shading correction is set based on the image quality. When the user sets the allowable range of the shading correction error via the control panel 154, a period T that falls within the set allowable range of the error is obtained from the characteristics of the lamp 32 of the exposure unit 3 and is set as a standard. By causing the control processing unit 152 to make the determination in step 27, the image quality or productivity desired by the user can be obtained based on the read image quality. As a result, the user can limit the execution of the shading correction by the estimated error of the shading correction.

[0019]

According to the first aspect of the present invention, when reading a plurality of documents in the second reading mode, the reading time of the documents and the time elapsed from the end of the previous shading are obtained. Since the shading correction is performed before reading the document only when the time exceeds a period T that guarantees a correction allowable range serving as a reference for performing shading correction, a deviation in the correction value of the document reading can be tolerated. Shading is not performed in the range, the number of times of shading can be reduced, and the productivity of reading a plurality of originals can be improved. According to the second aspect of the invention, the user can freely set the time from the completion of the shading correction to the next shading correction, so that the image quality and productivity required by the user can be reduced. Can be obtained on the basis of gender. According to the third aspect of the present invention, by enabling the user to limit the execution of shading correction based on the estimated error of the shading correction, the image quality and productivity required by the user are obtained based on the image quality. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing an image reading device according to an embodiment of the present invention.

FIG. 2 is an enlarged view showing the vicinity of a white reference plate of a main part of the image reading apparatus according to the embodiment of the present invention.

FIG. 3 is a characteristic diagram illustrating a temporal change characteristic of an output of a lamp used in a control method adopted by the image reading apparatus according to the embodiment of the present invention.

FIG. 4 is a flowchart for explaining the operation of the image reading apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image reading apparatus 3 Scanning exposure unit 5 Light receiving element 7a Contact glass for book reading 7b Contact glass for sheet through 9 Document conveying means 11a, 11b Mirror 13 White reference plate 15 Controller 31 Running body 32 Lamp 33 Mirror 90 Automatic document conveying apparatus 91 Document Stand 92 Feed Roller 93 Guide Roller 94 Discharge Roller 95 Document Collection Board 151 Reading Unit 152 Control Processing Unit 153 Drive Unit 154 Control Panel

Claims (3)

[Claims] A first reading mode in which an exposure scanning unit scans a document placed on a contact glass to scan the document; and a step of exposing the document while passing the document through a predetermined exposure position of the contact glass by document transport means. A second reading mode for reading in a state in which the scanning unit is fixed at the exposure position, wherein the image reading apparatus obtains an electric signal of a document image read in each of the reading modes. When reading a sheet of original document, the reading time of the original document and the time elapsed from the end of the previous shading are obtained, and only when the time exceeds the period T that guarantees a correction allowable range serving as a reference for performing shading correction. Make the shading correction before reading the original, and if the Image reading apparatus characterized by comprising a control means for causing the take-up saw. 2. The image reading apparatus according to claim 1, wherein said control means enables the user to set the time period T. 3. The image reading apparatus according to claim 1, wherein the control unit is capable of setting the period T based on an image quality that a user can accept.