JP2000349980A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that can obtain more accurate image data. SOLUTION: A 1st read means 2 reads a front side of an original 1 and a 2nd read means 3 reads a rear side of the original 1. A 1st side detection means 9 detects the size and skew of the original 1, on the basis of image data obtained by the 1st read means 2. A 2nd size detection means 10 detects the size and the skew of the original 1, on the basis of the image data obtained by the 2nd read means 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an image reading apparatus.

[0002]

2. Description of the Related Art An image scanner is one of image input devices for inputting image information on a document to a host computer. This image scanner is used, for example, as an input device of an electronic filing system. For example, in an insurance company, a real estate business, or the like, it is necessary to input information described in many contracts and the like generated in business into a computer. Therefore, an electronic filing system that inputs the contents described on the original as image data using an image scanner has been constructed with the aim of sharing the information and improving the efficiency of the search operation, while simultaneously and accurately inputting these originals. Is done.

[0003]

In documents such as the above-mentioned contracts, contracts are often described on both sides, and these documents are read by a conventional one-sided image scanner. In this case, the reading operation must be performed twice for one document, and in the case of continuously reading a plurality of documents, scanning is required for each reading operation. In some cases, the page order of the document may be lost.
Therefore, there is an increasing demand for an image scanner that can read image data on the front and back surfaces of a document in one reading operation.

[0004] On the other hand, due to recent social demands such as resource saving and space saving, there is an increasing demand for paper documents to be captured by an image scanner, converted into electronic documents, stored, and shared. Since the volume of documents handled by image scanners is enormous, the demand for image scanners that can read at high speed is increasing.

In such an image reading apparatus, when the document is skewed (skewed), the image on the document cannot be read in an appropriate state, and the read image data only looks bad. If the skew amount is large, the image may be lost. Also, the document size may be erroneously detected due to the document skew, and image data may be lost, or conversely, data larger than the original image data may be transferred to a filing system or the like, resulting in wasted use of system memory or the like. In an image reading device such as an image scanner, the read image data can be confirmed by using a pre-scan function or the like provided in advance in driver software or the like, but the image data can be visually checked like a copy. Basically, we can't do that, and if you don't notice that the image is missing due to skew,
It is very likely that a correct image will never be obtained again. In particular, in the industry where a large number of documents are handled at once, it is extremely inefficient to confirm each original using the above-described pre-scan function.

[0006] Generally, the cause of the document skew in the document transport mechanism (ADF) is a speed difference between rollers or rollers when a document is transferred between a plurality of rollers or rollers for transporting the document, or a transport force. Differences, differences in the balance of the conveying force due to the rollers and abrasion of the roller surface, and those due to the original such as curl and wrinkles of the original. Since skew is generated by these various factors, it is difficult to completely prevent skew. Therefore, there is a demand for an image scanner that automatically detects the skew and document size that occur and transfers the image data as appropriate image data.

In the detection means disclosed in Japanese Patent Application Laid-Open No. 7-50745, it is necessary to provide a dedicated detection and discrimination means. It is also necessary to secure a layout and take measures against the effects of external noise.

An object of the present invention is to provide an image reading apparatus capable of obtaining more accurate image data.

[0009]

According to a first aspect of the present invention, there is provided a transport path for transporting a document, first reading means provided in the transport path for reading the surface of the document, And a second reading means for reading the back side of the document, the image reading apparatus capable of reading the front side and the back side of the document at the same time. First size detection means for detecting the size and skew of the document based on the
An image reading apparatus comprising: a second size detection unit that detects a size and a skew of the document based on image data obtained by the second reading unit.

Therefore, the size and skew of the document can be detected based on the image data of the surface of the document.
Since the size and skew of the document can be detected based on the image data of the back side of the document, more accurate image data can be obtained.

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the second reading means uses a contact image sensor for reading an image.

Therefore, by using the contact type image sensor, the space required for the optical system such as securing the optical path length required for the reduction optical system can be reduced, and the size of the entire apparatus can be reduced. It is possible to reduce a detection error of a document size and a skew caused by a slight shift of an optical path by the reduction optical system, and to provide more accurate image data.

According to a third aspect of the present invention, in the image reading apparatus according to the first or second aspect, the reading position of the original by the first reading unit and the reading position of the original by the second reading unit. Is different in the document conveyance direction.

Therefore, the reading position of the front side and the reading position of the back side of the original are shifted to avoid the influence of show-through of the original, thereby improving the quality of the image data and the accuracy of the original size detection data. Can be done.

[0015] The invention according to claim 4 is the invention according to claims 1, 2, and 3.
3. The image reading apparatus according to claim 3, wherein the first size detection unit and the second size detection unit are switchable.

Therefore, according to the needs of the user,
Alternatively, the first size detection unit and the second size detection unit can be switched for protection when one image reading function is disabled.

[0017]

FIG. 1 is a functional block diagram schematically showing the functions of the image reading apparatus. The image reading apparatus includes first reading means 2 for reading image data on the front side of document 1 and second reading means 2 for reading image data on the back side of document 1.
And a third reading unit 4 for reading image data of only one side of the document. Note that the first reading means 2 and the third reading means 4 are the same, and are used by moving their positions depending on the reading mode.
In addition, the first mode may be selected according to the requested read operation mode.
The reading means 2 and the third reading means 4 are controlled by a first reading control means 5, and the second reading means 3 is controlled by a second reading control means 23. First reading means 2 and second reading means 3
Has a first image processing means 6 and a second image processing means 7 at the subsequent stage, respectively, and the image data read by the first reading means 2 or the third reading means 4 is the first image processing means. At 6, the image data read by the second reading means 3 is subjected to necessary processing such as shading correction by the second image processing means 7 and then sent to the data transfer means 8 as image data. The data is transferred to an external interface (not shown) at a predetermined transfer speed.

It is now assumed that the duplex reading mode is selected. At this time, the first reading means 2 and the second reading means 3
Under the control of the first reading control means 5 and the second reading control means 23, the front and back of the document 1 are read simultaneously. The read image data is subjected to predetermined processing by the first image processing means 6 and the second image processing means 7, respectively, and transferred to the data transfer means 8. The data transfer means 8 is an image memory for temporarily storing the image data in order to transfer the image data of the front side of the document 1 and the image data of the back side of the document 1 to the external interface at a predetermined transfer speed for each page. Etc.

Next, it is assumed that the one-sided reading mode is selected. In the case of a single-sided reading mode using an automatic document feeder (ADF) (not shown), the operation is the same as that of the above-described double-sided reading mode, but the image data read by the second reading unit 3 is transferred to the data transfer unit 8. Will not be forwarded. As another method of the single-sided reading mode, there is a means for fixing the original 1 and scanning the reading means. At this time, the original 1 is placed on the contact glass 22 (see FIG. 2), and the third reading means 4 is scanned along the original. Here, the first reading means 2 and the third reading means 4 are the same device. That is, in the single-sided reading mode and the double-sided reading mode using the ADF, the first reading unit 2 is stopped at a predetermined reading position, and in the single-side reading in which the document 1 is placed on the contact glass 22,
The first reading unit 2 reciprocates along the document 1. These first reading means 2, second reading means 3, third reading means
The operation of the reading means 4 is based on the first reading control means 5 and the second reading control means 2 in accordance with the previously requested reading mode.
3 is controlled.

Next, the means for detecting the document size will be described. In the case of the reading mode using the ADF, one of the first size detecting means 9 and the second size detecting means 10
Or, it is possible to select both. A case where the one-sided document reading is performed by the ADF will be described. At this time, the reading of the document 1 is started by a READ command from a host computer or the like (not shown). When the original 1 is transported by the ADF and reaches the reading position by the first reading unit 2, the first reading unit 2 reads the image data on the front surface of the original 1. The image data read by the first reading means 2 is the first image data.
The image data is transferred to the image processing means 6, where predetermined image processing is performed. At the same time, the first size detecting means 9 detects each data such as the leading edge, the trailing edge, and the skew amount of the document from the image data. You. After being image-processed by the first image processing means 6, it is transferred to the data transfer means 8 together with the information relating to the document size and the like, and temporarily stored in the image memory by the data transfer means 8. Is output. On the other hand, the original 1 is the first reading means 2
After passing through the reading position of, it is transported at the same speed,
The reading position is reached by the second reading unit 3. Second
The reading means 3 starts a reading operation when the document 1 reaches a predetermined reading position, and transfers the read image data to the second reading position.
To the image processing means 7. After that, the second size detecting means 10 provided in the second image processing means 7 converts the image data transferred from the second reading means 3 into
Similarly to the first size detecting means 9, the leading end, the trailing end,
Detects data such as the amount of skew. Since the single-sided original reading mode using the ADF is selected as described above, the image data of the back side of the original 1 transferred to the second image processing unit 7 is not transferred to the data transfer unit 8 at the subsequent stage. The CPU of a microcomputer (not shown) that controls the image reading apparatus reads the image data of the front side of the document 1 detected by the first size detecting means 9, that is, the data relating to the document size by the first reading means 2 and the second data. The image data of the back side of the document 1 detected by the size detecting means 10, that is, the data on the document size by the second reading means 3 is compared to determine the correct size of the document 1. In the above description, the first reading unit 2 and the second reading unit 2
The size detection of the original 1 is performed by using both the first size detecting means 9 and the second reading means 3 and the second size detecting means 10. It is possible to select or perform size detection by using. For example, the single-sided original reading mode using the ADF as described above is selected, and the size detection is performed by the first reading unit 2 and the first size detecting unit 9.
In this case, the second reading means 3, the second image processing means 7, the second reading control means 23, and the second size detecting means 10 do not need to read the back side of the document 1 itself. This is good, so if the power lines are completely separated for each reading system and the signal lines are properly processed, the power supply to the reading system of the second reading means 3 can be cut off. Therefore, it is possible to save energy.

As disclosed in Japanese Patent Application Laid-Open No. 7-1075, when a dedicated detecting means for detecting the leading edge and the trailing edge of the original 1 is constituted by a sensor, an error in the detection due to paper dust of the original may occur. In order to detect the skew or to detect the skew, a plurality of detecting means and discriminating means are required separately from the original reading means, which is not efficient. Further, since the output of the sensor is weak, there is a possibility that the detection accuracy may be reduced due to the influence of disturbance such as a temperature change. On the other hand, according to the image reading apparatus of the present embodiment, the first reading unit 2 and the second reading unit 3 read the image data on the document 1 and detect the leading edge and the trailing edge of the document 1. , Skew detection, it is possible to detect the leading edge and the trailing edge of the document 1 and the skew detection at the same level as the image data on the document 1. Also, the first reading means 2 and the second reading means 3
Because one or both of them can be used as the detecting means, it is possible to improve the detection accuracy of the document size and the skew in one reading of the document 1, and to temporarily determine the detection method described later. Even if one of the uniform density members used deteriorates with time, the detection function can be continuously used using the other member and the reading means. Further, in the case of a high-speed image scanner that reads both sides of the original 1 without lowering the original reading speed and the transfer speed to the external interface as in the image reading apparatus of the present embodiment, the A3 size original is read. If it corresponds, the first reading means 2
In some cases, a certain distance may be required between the reading position of the document 1 and the reading position of the second reading unit 3, and the transport path of the document 1 in the ADF tends to be long due to the layout of the apparatus. In other words, the factors causing the skew of the original 1 increase accordingly, so that the original size obtained by the first reading unit 2, the detection information on the skew, the original size obtained by the second reading unit 3, There is also a possibility that a discrepancy may occur between the detection information and the skew detection information. In order to improve this, the image data on the front and the back of the document 1 can be independently corrected, and can be transferred as accurate image data to an external interface.

FIG. 2 is a diagram showing a document transport path and first reading means 2 in the ADF of the image reading apparatus according to the embodiment of the present invention.
FIG. 3 is a block diagram illustrating a positional relationship of a second reading unit 3.
The document 1 is fed into the ADF by a sheet feeding unit (not shown), conveyed along the rotation of the conveying drum 13, and when the reading position A is reached, the first reading unit 2 starts reading the front side of the document 1. The first reading means 2 starts the reading operation when the leading edge of the document reaches the lead sensor 14 (see FIG. 3) located in front of the reading position A, and the document 1 continues to be conveyed, and the trailing edge of the document is After a lapse of a predetermined time after the passage, the reading operation ends. Here, the lead sensor 14 uses a reflection type photo sensor. Second
The reading means 3 moves the reading operation to the reading position B after a predetermined time has passed after the leading end or the rear end of the document 1 has passed over the read sensor 14 or after the first reading means 2 has started the reading operation. , And the lead sensor 14
The reading operation is terminated after a predetermined time has passed after the rear end of the original 1 has passed above or after the first reading means 2 has finished reading. The predetermined time is set by the first reading unit 2 and the second reading unit 3 slightly before the leading edge of the document reaches the reading position A and the reading position B. The first reading means 2 and the second reading means 3
By setting the predetermined time, the first uniform density member 11 and the second uniform density member 12 are read before the leading edge of the document actually reaches the reading positions A and B, and the density of the document 1 is compared with the density of the document 1. By detecting the difference, the size and skew of the document 1 are detected. Here, the first uniform density member 11 uses the surface of the transport drum 13 that transports the original 1. Since the surface of the transport drum 13 requires a certain degree of concentration uniformity, a cleaning means for the surface of the transport drum 13 which is configured to be separately pressed against the transport drum 13 (for example, a length approximately the same as the axial direction of the transport drum 13) A cleaning roller having a paper feeder) is provided to remove paper dust and the like generated in the ADF due to conveyance of the document 1 or the like.

Here, the second reading means 3 utilizes a contact image sensor. The contact type image sensor includes an LED as a light source, a lens, and a sensor element. The original 1 is illuminated by the LED in the contact image sensor, and the reflected light is focused by the lens of the contact image sensor, irradiates the sensor element of the contact image sensor, and is photoelectrically converted. The second uniform concentration member 12
In order to maintain the close contact between the document at the reading position B and the second reading means 3 and the transportability, the document is pressed against the second reading means 3.

Here, the timing from reading by the image reading apparatus to data transfer will be schematically described with reference to FIG. The document 1 is fed by a sheet feeding unit (not shown), and the document passes over the read sensor 14 and passes the front surface reading standby position. The front side reading standby position is a position where the next original 1 to be read is temporarily stopped in a case where a plurality of originals 1 are continuously read from the relationship between the transfer speed to the external interface and the original conveying speed. The document 1 reaches the front-side reading position (reading position A in FIG. 2) after a time t1 has elapsed after passing the front-side reading standby position,
Reading of the front side of the document 1 by the first reading means 2 is started. The image data on the front side of the document 1 read by the first reading unit 2 is subjected to predetermined image processing by the first image processing unit 6, then transferred to the data transfer unit 8, and transferred to an external interface. . (“Surface data transfer time” in FIG. 3 indicates a transfer time to the external interface.) The original 1 continues to be transported while being read by the first reading unit 2, and is read by the second reading unit 3 ( When the reading position B) in FIG. 2 is reached, reading of the back surface of the document by the second reading means 3 is started. At this point, the data transfer unit 8 has not yet transferred the image data of the front surface of the original that has been read to the external interface. 2 image processing means 7
After the predetermined image processing is performed, the image data is transferred to the data transfer unit 8 and temporarily stored in the image memory or the like (not shown) by the data transfer unit 8. After the image data on the front side of the document 1 has been transferred to the external interface, the data transfer means 8 starts transferring the image data on the back side of the document 1 stored in the image memory to the external interface. In FIG. 3, since the image data on the front side of the document 1, that is, the image data read by the first reading unit 2, is transferred to the external interface in a hanging state, a plurality of document 1 When reading is performed, the next original 1 is temporarily suspended at the front side reading standby position, and the image data of the back side of the original 1 by the data transfer unit 8, that is, the image data obtained by the second reading unit 3, is read. It is necessary to wait for the transfer to the external interface to end (the period indicated by “Note” in FIG. 3). Here, t1 is the time required for the document 1 to reach the reading position by the first reading means 2 from the front surface reading standby position, t2 is the reading time of the surface of the document 1, ie, the reading time by the first reading means 2, and the obtained image data. Is the time when the document 1 reaches the reading position by the second reading means 3 from the reading position by the first reading means 2, and t4 is the time when the second reading means 3 And t5 is the time required to release the image data on the back side of the document obtained by the second reading means 3 to the external interface. The document presence / absence sensor 15 detects a document 1 to be read in a document tray portion of the ADF, a pickup roller 16 and a feed roller 1.
7 is a paper feeding means for feeding the original 1 to the ADF original traveling path;
The transport drum 13 is a transport unit that transports the original 1 in the ADF, and the traveling body 18 is a first reading unit 2 that mounts a light source for irradiating the surface of the original 1 and a mirror in the first reading unit 2.
Of the original 1 to be read
Detecting means for detecting the position of a document tray used to lift a document tray (not shown) loaded with the document tray into the paper feed port of the ADF or to lower the position of the document tray for setting a document on the document tray; 20 is A
This is detection means for detecting when the paper is discharged from the DF.
Further, the feed sensor 21, the lead sensor 14, and the paper discharge sensor 20 also detect a document feed jam in the ADF.

Next, control for detecting the position and size of the original 1 will be described. The image reading apparatus according to the embodiment of the present invention includes a pixel counter and a line counter that output count values indicating positions in the main scanning direction and the sub-scanning direction, and reads with the values indicated by these two counters. Points can be shown. Further, in this embodiment, as shown in FIG. 2, a second uniform density member 12 is provided for the second reading means 3 and a first uniform density member 11 is provided for the third reading means 4. Have been. Further, the first reading means 2 for reading using the ADF has a transport drum 13 whose surface is maintained at a uniform density. The first and second uniform concentration members 1
Since the densities 1 and 12 are intended to be separated from the background density of the original 1, the densities must be set so that they can be reliably separated from the background of the original 1. Note that the density level of a general white original is represented by an optical density value (OD
Value) is about 0.1, so that it is sufficient that the uniform density member has a density that can be separated from this OD value. FIG.
(A) is a distribution diagram showing the density level distribution of the first and second uniform density members 11 and 12 in the main scanning direction. In this embodiment, the black level is large and the white level is small.
Here, for the sake of simplicity, it is shown that the first and second uniform density members 11 and 12, which are uniform densities, are read and uniform density levels are output. Further, the ends of the first and second uniform density members 11 and 12 in the main scanning direction are also illustrated as positions a and b, but are not particularly limited.
The position a in the figure is the first pixel of the pixel counter, and the pixel counter sequentially counts up in correspondence with each pixel in the main scanning direction. FIG. 4B is a diagram showing the density level distribution when the original 1 is detected in the areas of the first and second uniform density members 11 and 12, where the position c is the start of the original density distribution in the main scanning direction. The position and position d indicate the end position of the document density distribution in the main scanning direction, and the position between position c and position d indicates the width of the document 1. These c positions,
Both the d position and the point position are digitized by a pixel counter in the main scanning direction, and the point indicated by this address indicates the position and width of the document 1 thereafter. Further, the displacement in the sub-scanning direction is digitized by a line counter in the sub-scanning direction, and can be indicated as address information.

Next, the document size detection process will be described. First, the original 1 is conveyed until the leading end of the original 1 appears with respect to the original size detection position, and the original information at that time, that is, the positions c and d in FIG.
If the detection is successful, an interrupt is generated at that point in time for a CPU (not shown). The CPU receives the interrupt, and determines the c position and d obtained by detecting the document size.
By reading the address of the position, information on the document position and the document width can be obtained. When the document size detection process is completed, the CPU reads the document 1 and transfers the document size detection information together with the image data on the document 1 to the external interface. In a device that obtains image data from the image reading apparatus via an external interface, for example, a host computer, the image data and the document size information can faithfully reproduce the image data as data obtained in the main scanning synchronization. Becomes
In the above description, the means for detecting the document size at the leading edge of the document 1 is described. However, the trailing edge of the document 1 can be detected by a similar method.

Next, the processing in the case where the conveyed document 1 has a skew will be described. In the above example, the original 1 is conveyed until the original 1 reliably appears at the original size detection position. However, when the skew of the original 1 is detected, the detection process is executed before the original 1 reaches the detection position. There is a need to. When the skew detection is executed, the position information and the document width of the document 1 are detected in the line length in the main scanning direction in order from the leading edge of the document 1 at the document size detection position, and an interrupt is generated for the CPU each time. Is written to the register. While performing this interrupt processing, the CPU retrieves the position information of the document 1 at the time of the previous interruption from the register and compares it with the position information of the document 1 at the time of the current interruption. As a result, if the original widths are different, original 1
Can be determined to have caused skew. The processing related to skew detection will be described. FIG.
In (a), since the document 1 has not yet appeared, no interruption to the CPU occurs. The conveyance of the original 1 is continued, and when the line data of FIG.
The tip of appears. From this time, an interrupt occurs to the CPU, and the CPU writes the read positional information of the document 1 to the register. Subsequently, when the document information shown in FIG. 5C is obtained, the CPU generates an interrupt to write the information shown in FIG. 5C into the register, and also obtains the document position information obtained at the previous position shown in FIG. Compare with the data. In this case, the line data at the position shown in FIG. 5C has a wider original width, so that the original 1 is skewed and the original width has not yet reached the maximum value, and is being expanded. And judge. Further, while writing the document position information at the time of occurrence of the interrupt in FIG.
The document position data of the document 1 where the interruption has occurred in FIG. 5D is read. Then, similarly to the above, the document position data of FIG. 5C and the document position data of FIG. 5D are compared to determine that the document width is wide. Then, it is determined that the data is the same as the previous data, that is, the data obtained in FIG.
That is, at this point, the document 1 has been conveyed to the maximum width. The maximum width is due to the conveyance up to FIG. 5D, and the data in FIG. 5E is used as data for determining whether or not the data is the maximum data. As described above, the document width data is updated while performing the interruption process by the document detection process, and the maximum width of the document is detected. In the example of FIG. 5, the leading edge of the document 1 is detected from FIG.
The transport distance up to (d) is the amount of deviation due to skew. In order to actually represent the skew amount, the position information (X1, Y1) in FIG.
The position information (X2, Y2) and (X3, Y3) of (d) are used. The CPU that has determined in FIG. 5E that the data in FIG. 5D has the maximum width collects the data and sends the obtained document position information to the external interface in accordance with an instruction from the external interface. Then, it is determined whether or not to send the document position information to the external interface, and when to send the document position information (for example, before and after the image data of the document 1).

In the method described with reference to FIG. 5, if foreign matter such as dust adheres to the document size detection position, the dust or the like may be erroneously detected as information on the leading edge of the document 1. Therefore, a processing method in which erroneous detection is not performed by a foreign substance such as dust will be described. In the detection processing, the document width grows so as to cover the position data of the leading edge of the document 1. At this time, since the position of the foreign matter such as dust does not change, it is generated as interrupt data at the same position and the same width many times. Therefore, if an interrupt occurs at the same position and the same width, it is determined as a foreign substance such as dust, and thereafter, data at this position is deleted from the data to detect skew, and interrupts at other positions are not detected. The generated data is determined to be the original 1. With this processing, the skew amount of the document 1 can be accurately detected.

Next, an example of processing means for fixing the original 1 and placing it on the contact glass and scanning the first reading means 2 to read the original 1 will be described. It is assumed that the original 1 is placed in contact with a preset origin position. Also in this case, similarly to the above-described detection processing in the ADF reading, it is necessary to separate the original 1 from the other areas. Therefore, by providing a uniform density area on the surface of the pressure plate that holds the original 1, this can be achieved during the reading operation. The position information of the document 1 can be detected by utilizing the information. The operation of detecting the document position information (including the size information) is as follows. First, the document 1 is placed at a position where the area of the document 1 can be reliably determined within the uniform density area, and the first reading means 2 is attached to the document 1. The same control as described with reference to FIG. 5 is performed by reading the uniform density area including the original 1 while scanning along the original, and the original position and original width are detected based on the detection data. Now, since the original 1 is placed against the origin position, the original reading starts from the origin position. At this time, in order to reliably detect the trailing end of the original 1, it can be determined that the original 1 is present in the original 1, and the size of the original 1 is not hindered by the density of image data in the original 1. Trace processing is performed on image data inside the original-side surface of the document 1. While reading the document 1 in the sub-scanning direction at the same reading position thereafter, the presence or absence of the document 1 is detected based on the density of the document 1. If the original 1
Is completed, the density is switched to the density on the back of the pressure plate instead of the density of the original 1 at that time. The switching from the document density to the density of the uniform density member on the back of the pressure plate is detected, and an interrupt is generated for the CPU. In response to the interruption, the CPU stops reading the original 1 and stops scanning of the first reading unit 2. Further, the CPU detects the count value of the sub-scanning line counter when an interruption for ending the document 1 occurs. By grasping this count value, the number of lines of the read image data can be known.

Document 1 as described in the present embodiment
In the image reading apparatus that can simultaneously read the front and back surfaces of the document 1, the transport path of the document 1 in the ADF is as shown in FIG.
As shown in the layout of FIG.
A difference may occur between original position information obtained when the front side of the original 1 is read, particularly skew information, and original position information (skew information) obtained when the second reading unit 3 reads the back side of the original 1. It is thought enough. Therefore, it is possible to obtain accurate image data by providing the above-described detecting means in each of the first reading means 2 and the second reading means 3 and adopting a configuration in which the CPU obtains the respective document position information. In addition, according to an instruction from the external interface, when reading a document using the ADF, one of the information on the document position, size, and skew by the first reading unit 2 and the information by the second reading unit 3 is selected. By providing selection means and switching means for selecting whether to increase the accuracy by using both information or both, it is possible to always obtain good original information and obtain accurate and accurate original information. Becomes possible.

In the image reading apparatus of this embodiment, the first reading means 2 uses a reduction optical system using a photoelectric conversion element, and the second reading means 3 uses a contact image sensor. When an automatic document feeder (ADF) for automatically feeding the original 1 is mounted as in the image reading apparatus of the present embodiment, a reading mechanism for reading the back surface of the original 1, that is, the second reading unit 3 is provided inside the ADF. When the second reading means 3 is configured by a reduction optical system, it is expected that the size of the ADF will increase in order to secure an optical path length. Therefore, by using a contact image sensor for the second reading unit 3 that is likely to be arranged in the ADF,
The size of the ADF device can be reduced, and as a result, the size of the entire image reading device can be reduced. Further, instead of applying the means for detecting the position and width of the document 1 only to the first reading means 2, a similar detection means is provided for the second reading means 3, so that, for example, one of the reading means Even if the detecting means by means performs erroneous detection for some reason, it becomes possible to continue to provide the detecting function by the detecting means by the other reading means.

[0032]

According to the first aspect of the present invention, the size and skew of a document are detected based on image data of the front surface of the document, and the size and skew of the document are detected based on image data of the back surface of the document. So you can
More accurate image data can be obtained.

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, by using a contact type image sensor, a space required for an optical system such as securing an optical path length required for a reduction optical system is obtained. It is possible to reduce the size of the entire apparatus, and to reduce the detection error of the original size and skew due to the slight deviation of the optical path due to the reduction optical system, so that more accurate image data can be obtained. Can be provided.

According to a third aspect of the present invention, in the image reading apparatus according to the first or second aspect, the reading position of the front side of the document is shifted from the reading position of the back side to avoid the influence of the show-through of the document. , While improving the quality of image data,
The accuracy of the document size detection data can also be improved.

The invention according to claim 4 is the invention according to claims 1, 2, and
3. In the image reading apparatus according to any one of the first to third aspects, the first size detecting means and the second size detecting means may be used in response to a user's need or for protection when one of the image reading functions is disabled. And the size detecting means can be switched.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a functional block diagram of the image reading device.

FIG. 3 is an explanatory diagram of the image reading device.

FIG. 4 is a timing chart illustrating an operation of the image reading apparatus.

FIG. 5 is a timing chart illustrating the operation of the image reading apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original 2 First reading means 3 Second reading means 9 First size detecting means 10 Second size detecting means

Claims (4)

[Claims] A first transport unit that is provided in the transport path and reads a front surface of the original; and a second read unit that is provided in the transport path and reads a back surface of the original. An image reading apparatus comprising: reading means for simultaneously reading the front side and the back side of the document; and a first detecting means for detecting a size and a skew of the document based on image data obtained by the first reading means. An image reading apparatus comprising: a size detecting means for detecting the size and skew of the document based on image data obtained by the second reading means. 2. The image reading apparatus according to claim 1, wherein the second reading unit uses a contact image sensor for reading an image. 3. The document reading position according to claim 1, wherein a reading position of the document by the first reading unit and a reading position of the document by the second reading unit are different in a conveying direction of the document. The image reading device according to claim 1. 4. The image reading apparatus according to claim 1, wherein said first size detecting means and said second size detecting means are switchable.