JP3322050B2 - Image reading device - Google Patents

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 such as a digital copying machine for optically reading an image of a document set on a document table such as a platen glass.

[0002]

2. Description of the Related Art At present, a digital copying machine has been developed which converts an optical image obtained by irradiating an original with light into an electric signal and digitizes the same to copy the original image on a medium such as paper.
Has been put to practical use. In this type of image reading device, a CCD
After converting the optical image based on the input light passing through the original into an analog signal using a photoelectric conversion element such as an image sensor,
Various signal processing is performed. In recent years, there has been known an image reading apparatus provided with a document feeding mechanism for automatically feeding a plurality of documents to a document table and performing a reading process continuously. In an ordinary image reading apparatus, an image reading area corresponding to a document size is defined based on a preset registration position (a center position in the case of a center reference, and a corner position in the case of a corner reference). To read the original image. Therefore, in the document feeding mechanism provided therein, it is necessary to accurately position the document fed by the rotation of the transport roller in the image reading area. However, this type of document feeding mechanism employs a method in which the document is fed by the rotation of the transport roller. If skew occurs due to slippage between the roller surface and the document surface, the position of the actually fed document is reduced. Deviates from a target position (image reading area), and a part of an image to be read is lost.

[0003]

In the prior art, Japanese Patent Laid-Open No. Hei 6-266180 discloses a method in which the position of an original feeding mechanism with respect to the apparatus main body is adjusted to correct the positional deviation of the original during feeding. No. pp. 147-64. However, in the above-mentioned prior art, the copying process is actually performed using the document feed mechanism, the original image of the copy is compared with the output image after the copy, and the position of the original feed mechanism with respect to the apparatus body is determined based on this. The copying operation must be repeated many times until the original fed by the original feeding mechanism is fed to the correct position. Was. Further, since the mounting position of the document feed mechanism is adjusted by relying on manual work, the final fine adjustment is extremely difficult and requires skill.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. It is an object of the present invention to set a registration position, which is a reference when defining an image reading area, in a short time and without skill. It is an object of the present invention to provide an image reading apparatus that can perform the operation.

[0005]

The present invention SUMMARY OF THE INVENTION has been made in order to achieve the above object, subject copy which has been fed to the image reading position by the document feeding mechanism, run primarily preset
In an image reading apparatus that defines an image reading area corresponding to a document size based on a registration position in a scanning direction and optically reads a document image within the image reading area, at least a predetermined area on a document front side and a document rear end side. Using a test document in which a mark for detecting a change point is recorded at the position , the image reading area is defined.
A performs the setting of the registration position as a reference position when a constant, the image of the main scanning on the line including the recording position of the mark at the tip side and the rear side of the test document fed by the document feeding mechanism Reading means for detecting a change in the scanning information on the leading end side and a changing point of the scanning information on the trailing end side of the test document read by the reading means; Information and mechanism of the two change points detected by the means
Position relative to the normal image reading position obtained from the
And a registration position setting means for setting a registration position in accordance with the positional relationship .

[0006]

In the image reading apparatus of the present invention, the change point of the scanning information on the leading end side of the test document and the changing point of the scanning information on the trailing end side are detected by the change point detecting means. Since each change point varies depending on the document feeding position of the document feeding mechanism, if a skew occurs during document feeding, the actual document reading position will deviate from the normal position. Therefore, a registration position serving as a reference for setting an image reading area is set by a registration position setting unit based on the direction of the actual image reading position and how much the actual image reading position deviates from the normal position from the position information of each of the above-mentioned changing points. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to, for example, a digital copying machine will be described below in detail with reference to the drawings. The image reading apparatus according to the present invention is not limited to application to a copying machine, but can be applied to all electronic devices having a function of optically reading image information of a document.

FIG. 1 is a schematic configuration diagram of a digital copying machine to which the present invention is applied. In FIG. 1, an analog image signal output from a CCD image sensor 1 is converted into digital data by an image data generation circuit 2 and then supplied to a correction / filter circuit 3 as image data. The correction / filter circuit 3 performs shading correction on the input image data, and further performs a filtering process on the image data after the shading correction. The edit processing circuit 4 performs, for example, edit processing such as reduction or enlargement on the filtered image data. In this processing, a RAM is used as a storage means of the image data.
5 is used. The image data that has been subjected to the predetermined editing processing is sent to the output interface circuit 6, and is supplied to the image forming unit 7 such as a printer.

CPU 8 has a data / address bus (CP)
The above-mentioned circuits are controlled via a U bus 9, and a control program therefor is stored in a ROM 10. In various processing operations of the CPU 8 (for example, shading correction processing), the RAM 11 is used for temporarily storing data. Further, the CPU 8
A document detection sensor 1 incorporated in a document feed mechanism described later
2 is connected, and based on the sensor output (on / off signal), the position of the document end at the time of document feeding can be detected. The CPU 8 sends a motor drive signal to a carriage motor 13 of a carriage for driving the optical system via a motor driver circuit 14, and a motor driver circuit 16 to a transport motor 15 serving as a drive source of a transport roller (described later). In addition to supplying a motor drive signal via the CPU, a normal document image reading process is performed, and a registration position serving as a reference position for defining an image reading area is also set. The registration position setting process will be described later in detail.

FIG. 2 is a schematic configuration diagram of an image reading apparatus in a digital copying machine. As shown in the drawing, a platen glass (document table) 31 on which the document P is placed is provided on the upper surface of the apparatus main body 30, and the document P placed there is provided.
Is pressed down from above by the platen cover 32. The platen cover 32 has a white document pressing surface on the lower surface side, and is attached to the apparatus main body 30 at one end side so as to be freely opened and closed at a pivot point.

On the other hand, below the platen glass 31, an exposure lamp 33 for irradiating the original P placed on the platen glass 31 with light, and a reflection lamp for reflecting the reflected light from the original P in a predetermined direction. An optical system including mirrors 34 and 35 and the CCD image sensor 1 that captures reflected light from the mirrors via an imaging lens 36 is provided. Among the components of the optical system, the exposure lamp 33 and the reflection mirrors 34 and 35 are mounted on a carriage (not shown), and move the document surface optically with the carriage in the horizontal direction in the figure, that is, in the sub-scanning direction. It is configured to be able to scan. The CCD image sensor 1 employs a line sensor in which a large number of pixels are arranged in a straight line, and is electrically fixed in a direction orthogonal to the sub-scanning direction, that is, in the main scanning direction. It is configured so that scanning can be performed.

In addition to the above, on the upper part of the apparatus main body 30,
A document feed mechanism 37 is mounted integrally with the platen cover 32. The document feed mechanism 37 includes a document tray 38 for setting a document P, and a document tray 3.
A conveyance roller 39 for feeding the originals P separated one by one from the original sheet 8 along a predetermined conveyance path, and an original detection sensor 12 for detecting the leading end position of the originals P fed out of the original tray 38 (see FIG. 1). The document P fed from the document tray 38 is fed onto the platen glass 31 by the rotation of the transport roller 39.

In the digital copying machine having the above configuration, when the apparatus power is turned on (ON), the exposure lamp 33 and the reflection mirror 34 mounted on a carriage (not shown) are provided.
The optical system including 35 moves to the main scanning original reading position.
Then, the optical system optically scans the original P set on the platen glass 31, and the original image is captured by the CCD image sensor 1, where it is photoelectrically converted and converted into an analog image signal. This analog image signal is converted into digital data by an image data generation circuit 2, and the converted image data is processed by a correction / filter circuit 3 and an editing and processing circuit 4 such as shading correction, filtering processing, and reduction / enlargement. After that, the image data is supplied to the image forming unit 7 via the output interface circuit 6, where the image is formed on a copy sheet.

Next, a process of setting a registration position, which is a reference position for defining an image reading area on the platen glass 31 when reading a document image, will be described.
The registration position setting process is performed by the CPU 8, and a functional block diagram for the setting process is shown in FIG. In the registration position setting process, a test document in which a mark for detecting a change point is recorded at least at respective predetermined positions on the leading edge side and the trailing edge side of the document, for example, as shown in FIG. A test document Pt in which a black line is drawn at the center position of the document width (in the left-right direction) is used.

In FIG. 3, the reading means 40 sets the registration position by using the leading edge F and the trailing edge R of the test document Pt (see FIG. 5) fed by the document feed mechanism 37.
1 reads an image on the main scanning lines L1 and L2 including a recording position of a mark (black line), which is a conveyance system (a document detection sensor 12, a conveyance motor 15, a motor driver circuit 16, etc.) for conveying the test document Pt. ) And an optical system for reading images (exposure lamp 33, reflection mirrors 34 and 3).
5, imaging lens 36, CCD image sensor 1, etc.), and further, each circuit system for image data processing (image data generation circuit 2, correction / filter circuit 3, editing processing circuit 4, etc.)
Composed of The image data obtained by the reading means 40 is stored in the RAM 5 used for editing processing such as reduction / enlargement.

The image data scanning means 41 scans the contents stored in the RAM 5 following the reading timing of the reading means 40. Further, the first change point detecting means 42 and the second change point detecting means 43 detect a change point of each scan information of the scan information of the image data scanning means 41 obtained at a predetermined timing (described later). Is what you do.
Incidentally, in this embodiment, the test document P shown in FIG.
Due to the specification of t, each main scanning line L stored in the RAM 5
Boundary pixels from when the output color level of the image data (binary data) on L1 and L2 changes from “white” to “black” in the document area until it changes from “black” to “white” Intermediate positions X1 and X2 between them are detected as changing points on the front end F and the rear end R of the test document Pt.

The offset value calculating means 44 calculates a normal image reading position (a position recognized before the registration position setting process) obtained from the mechanical design value.
Based on the position information of each change point detected by the first and second change point detection means 42 and 43, in which direction the actual image reading position is displaced from the above-described normal position and how much distance is shifted Is calculated as an offset value. Then, the registration position setting unit 45 sets the registration position by registering the offset value calculated as described above, for example, as a displacement correction value at the time of image reading.

Next, the procedure of the registration position setting process executed by the CPU 8 will be described with reference to the flowchart of FIG. When the apparatus power is turned on (ON), the CPU 8 first sets the exposure lamp 33 and the reflection mirror 3.
The carriage on which the papers 4 and 35 are mounted is moved from the normal reading position (below the platen glass 31) to a predetermined reading position, in this case, substantially below the transport roller 39, and further, the main scanning reading of the front end F of the test document Pt is performed. The document stop position information corresponding to the line L1 position is set, and the motor driver circuit 1
Then, a motor control signal is output to step 6 (step S1). In this embodiment, due to the configuration of the image reading apparatus, the image of the document fed from the document feed mechanism 37 is optically read through a reading window (not shown) provided below the transport roller 39. Therefore, at the time of the registration position setting process, the carriage is moved at this point in order to read the image from the reading window. Next, the test document P set on the document tray 38 is
t is conveyed together with the rotation of the conveyance roller 39 by the motor control signal (step S2). Thereafter, it is determined whether or not the test document Pt has reached the reading position based on the on / off switching timing of the document detection sensor 12. For example, the determination is made based on the number of drive pulses given to the transport motor 15 from the motor driver circuit 16 (step S3).

Subsequently, when the test document Pt reaches a predetermined reading position, the conveyance motor 15 is turned off to stop the test document Pt (step S4). Image of CCD
The image data is read by the image sensor 1, and the obtained image data is subjected to a predetermined signal processing so that the RAM 5
(Step S5). Next, by scanning the content stored in the RAM 5, a change point X1 of the scan information is obtained.
(FIG. 5) is detected. Thereafter, in step S7, it is determined how many times the image has been read in the main scanning direction. At this point, since the reading has been performed only once in step S5, the process proceeds to step S8, where the position of the previously detected change point X1 is, for example, RA
M11 and the rear end R of the test document Pt.
The next document stop position information corresponding to the position of the main scanning read line L2 is set. Hereinafter, steps S2 to S
In step S5, the same processing as described above is performed, and
By scanning the contents stored in the RAM 5 in step 6, a change point X2 (FIG. 5) of the scanning information is detected. When the number of readings in step S5 becomes two, the process proceeds from step S7 to step S9. .

Next, at step S9, the previously stored change point X1 and the change point X2 obtained by the current reading operation are determined.
Average position, that is, the intermediate position Xc between the change points X1-X2
(FIG. 5) is detected. Then, the previously detected average position X
From the positional relationship between c and the normal position (the position recognized before the processing based on the mechanical design value), how much the actual image reading position Xc is in any direction with respect to the normal reading position described above. The offset is calculated as an offset value, and the calculated offset value is registered as a position shift correction value at the time of image reading, and a registration position is set (step S10). At this time, the method of setting the registration position is divided into two ways depending on the difference in the document positioning method. One is a case where the document positioning method is based on the center. In this case, the registration position is set by registering the previously obtained offset value as a displacement correction value as it is. The other is a case where the document positioning method is a corner reference (side reference). In this case, the document in the main scanning direction is determined from the average position Xc of the previously detected change point and the document size set on the document tray 38. The end position shift amount (including the shift direction) is obtained as an offset value,
By registering this as a position shift correction value, the registration position is set. Finally, the test document Pt is discharged from the platen glass 31 and a driving signal is output to the carriage motor 13 to move a carriage (not shown), and the exposure lamp 33 and the reflection mirror 3 mounted on the carriage are moved.
4, 35 are returned to the original position, that is, the normal image reading position (below the platen glass 31) (step S11).

Thus, in the subsequent image reading process, the image reading area is defined based on the registration position set based on the offset value. Thus, it is possible to accurately position the image reading area defined on the platen glass 31.

In the above embodiment, the change points X1 and X2 are detected on both the leading end F and the trailing end R of the test document Pt, for the following reasons. . That is, since the original P fed by the original feeding mechanism 37 may cause skew during the feeding, image data for an arbitrary one line of the test original Pt, for example, the main scanning on the leading end side F of the test original Pt. If the change point X1 obtained from the image data on the line L1 is used as a reference position for setting the registration position, the read position (change point X1) recognized there is slightly shifted from the actual read position (average position Xc of change points). As a result, the resist position cannot be appropriately set. Therefore, when the skew occurs in the document fed by the document feed mechanism 37 after the registration position is set as described above, only the change point X1 on the main scanning line L1 on the leading end side of the document is detected. 6
As shown in (a), the original P is largely shifted to the left side of the image reading area E1, and that part is deviated from the image reading area E1, but each of the main scanning lines L1 on the leading end side and the rear end side of the original. , L2, the skewed document P is detected as shown in FIG. 6B.
Is positioned substantially at the center of the image reading area E2, and the registration position is appropriately set.

In the above embodiment, in setting the registration position, the optical system such as the exposure lamp 33 and the reflection mirrors 34 and 35 mounted on the carriage (not shown) is moved below the transport roller 39, and during that time, Although the image on the specified main scanning lines L1 and L2 is read through the reading window provided in the printer, the present invention is not limited to this. In the case where a reading operation is performed in a state of being placed on the platen glass 31, the original image on the prescribed main scanning lines L1 and L2 is read while moving the carriage below the platen glass 31. Is also good.

[0024]

As described above, according to the present invention,
Reading means for reading an image on a main scanning line including a recording position of a mark (for detecting a change point) at a leading end and a trailing end of a test original fed by the original feeding mechanism; Change point detecting means for detecting a change point of the scan information on the leading end side and a change point of the scan information on the rear end side of the obtained test document, and a resist position for appropriately setting a resist position from each detected change point Since the apparatus is provided with the setting means, it is not necessary to repeat the copying operation many times in adjusting the registration position as in the related art, and the registration position can be set in a short time and skilllessly.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a digital copying machine to which the present invention is applied.

FIG. 2 is a schematic configuration diagram of an image reading apparatus according to an embodiment.

FIG. 3 is a functional block diagram for a registration position setting process.

FIG. 4 is a flowchart illustrating a registration position setting procedure;

FIG. 5 is a diagram illustrating a relationship between a specification example of a test document and an output level of image data.

FIG. 6 is a comparison diagram illustrating a relationship between an image reading area and a document feeding position.

[Explanation of symbols]

 Reference Signs List 40 reading means 42 first change point detection means 43 second change point detection means 45 registration position setting means Pt test original

Claims (2)

(57) [Claims] An image reading area is defined for a document fed to an image reading position by a document feeding mechanism in accordance with a document size based on a preset registration position in a main scanning direction. in the image reading apparatus for reading a document image optically in the image reading area, the mark for the change point detection on the predetermined position of at least the original tip end side and the document rear end with a test document recorded, image
Setting the registration position as a reference position when defining the image reading area, the recording position of the mark at the front end side and the rear end side of the test document fed by the document feed mechanism Reading means for reading an image on a main scanning line including: a change check for detecting a change point of the scan information on the leading end side and a change point of the scan information on the same rear end side of the test document read by the reading means; Output means, and the positions of two change points detected by the change point detection means.
Regular image reading obtained from the position information and mechanical design values
An image reading device comprising: a registration position setting unit configured to set the registration position according to a positional relationship with a take position . 2. The method according to claim 1, wherein the registration position setting means is configured to perform the change.
The position information of the two change points detected by the point detection means
Regular image reading obtained from mechanical design values based on
Calculate the offset value that represents the deviation from the
The document skewed using the offset value
Set the resist position so that it is positioned almost at the center.
2. The image reading apparatus according to claim 1, wherein the image reading apparatus is configured to set the image reading apparatus.