JP2005167933A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect dust and dirt without operating a movable optical system and to detect dust and dirt between paper sheets even when a document is fed at high speed. <P>SOLUTION: In the image reader including an apparatus body provided with an original platen, a movable optical system for reading a document image, and a first image pickup means having a photoelectric transducer and an image forming lens for making document reflection light from the optical system into an image signal. The image reader has second image pickup means having a photoelectric transducer and an image forming lens different from those of the first image pickup means, an image incident on the second image pickup means is guided by the movable optical system. Thus, images which are guided by the movable optical system, on the surface of the original platen at a reading position of the first image pickup means and in peripheral areas are made incident on the second image pickup means having the photoelectric transducer and the image forming lens different from those of the first image pickup means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus that reads a document image while moving the document at a constant speed.

  Conventionally, as a method for avoiding black streaks in the read image output due to adhesion of dust / dirt to the flow reading position on the platen glass during the flow reading for reading the original image while moving the black and white image original at a constant speed, For example, as shown in FIG. 7, the CPU 512 of the image reading apparatus performs dust detection processing on the platen glass by the dust detection circuit 520 during the non-document reading period, and dust is detected based on the dust detection processing result during continuous document reading. Correction processing is performed by interpolating the target pixel data with the peripheral pixel data, and during the period from the end of a series of image reading jobs to the next image reading job, the reading position is changed to a position where there is no dust on the platen glass. In addition, a dust avoidance process is performed, and when dust avoidance is difficult, the scanning itself is prohibited, and a control for switching to document reading by scanning optical system scanning is performed (Japanese Patent Laid-Open No. 200). 2-354213) and (Japanese Patent Laid-Open No. 2002-185725).

In addition, when dust is detected, a warning is issued to prompt the user to clean the glass (JP-A-7-115494) and JP-A-2001-144901.
Japanese Patent Laid-Open No. 7-115494 JP 2001-144901 A

However, in the conventional configuration, the dust detection operation for comparing the images sequentially recorded in the line memory using the imaging optical system for reading the original is performed by detecting and avoiding the dust by moving the optical system a predetermined distance several times. Because of the following problems,
1. If the gap between the manuscript papers is simply increased when improving the productivity at the time of the flow reading, the manuscript paper passes through the reading position before the optical system moving operation is completed several times, and only the first image pickup means is used. Unable to perform the dust detection operation. In order to solve this problem, if the second image pickup means is arranged for dust detection, the dust detection area overlaps with the standby position of the moving optical system, so that the same area as the first image pickup means is arranged to be read. Can not.

  If a 2.3 line color image sensor is used, it will be necessary to avoid dust for each line. Therefore, the movement distance of the optical system necessary for dust detection is increased, which is greater than with a 1 line monochrome image sensor. The time required for the dust avoidance operation becomes longer and the productivity is impaired.

  3. Since it is not possible to check the accumulation of paper dust and other floating substances moving on the glass surface between the sheets of paper, the paper dust generated during a large amount of JOBs will be detected early before entering the reading position. Cleaning warning cannot be made.

  The present invention has the following configuration in order to eliminate such problems.

  1. An apparatus body having a document table; a movable optical system for reading a document image; a first imaging means having a photoelectric conversion element and an imaging lens for converting reflected document light from the optical system into an image signal; The second imaging means having a photoelectric conversion element different from the first imaging means and an imaging lens is characterized in that the second imaging means includes a first imaging means reading position and a peripheral area guided by the movable optical system. An image on the surface of the document table is captured without operating the movable optical system.

  2. The second imaging means is characterized in that it captures an image of the surface of the platen glass near the reading position of the first imaging means in a wide area at least in the sub-scanning direction from the first imaging means, and based on the captured image information, The reading position of the first image pickup means is moved to a place where there is no foreign object by only one operation of the moving optical system.

  3. A circuit for detecting the distribution state of the area sensor and the foreign matter on the glass is added to the second image pickup means in the dust detection means, and the image on the glass is obtained from a wide area image of the surface of the platen glass taken in by one exposure operation. When it is detected that the accumulation state of foreign matter exceeds a certain area, the movement optical system is moved away from the accumulation area so that the reading position of the first imaging means moves away. In addition, a glass cleaning warning is generated.

As explained above The first imaging means reading position guided by the movable optical system and the image on the surface of the document table in the peripheral area are incident on the second imaging means having a photoelectric conversion element and an imaging lens different from the first imaging means. As a result, dust contamination can be detected without operating the movable optical system, and dust contamination can be detected between sheets even if the speed of document conveyance is increased.

  2. The second imaging means captures an image of the surface of the platen glass near the reading position of the first imaging means in a wide area at least in the sub-scanning direction from the first imaging means. Therefore, based on the captured image information, the moving optical Even if a three-line color image sensor is used, the time required for dust detection and avoidance does not increase because the first imaging means reading position is moved to a place where there is no foreign matter by only one operation of the system.

  3. A circuit for detecting the distribution state of the area sensor and the foreign matter on the glass is added to the second image pickup means in the dust detection means, and the image on the glass is obtained from a wide area image of the surface of the platen glass taken in by one exposure operation. When it is detected that the accumulation state of foreign matter exceeds a certain area, the movement optical system is moved away from the accumulation area so that the reading position of the first imaging means moves away. In addition, since a glass cleaning warning is generated, the probability of image failure due to floating dust is greatly reduced.

  4). Since the main scanning optical axes of the first imaging unit and the second imaging unit coincide with each other when viewed from the direction perpendicular to the platen glass, the time required for the calculation for calculating the optical system movement position for the dust avoidance operation is minimized. Can be.

  5). Since the longitudinal directions of the area sensors of the first imaging means line sensor and the second imaging means are matched, the second imaging means can be arranged without increasing the size in the height direction of the reading apparatus body.

  6). In the dust avoidance position calculation process, based on the detected dust position that is on the most upstream side in the original document transport direction, the position further upstream than this position is moved to a position that becomes the reading position of the first imaging means. As a result, the probability of sudden image failure due to floating dust can be greatly reduced.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

(Embodiment 1)
(FIG. 1) is an overall view showing an image reading apparatus according to Embodiment 1 of the present invention (FIG. 2) is a block diagram (FIG. 3) is a diagram for explaining a second imaging unit (FIG. 4) is an area sensor and a line FIG. 5 is a diagram for explaining the difference in the angle of view of the sensor (FIG. 5) is a flow chart at the time of flow reading. FIG. 6 is a diagram showing the positional relationship of each imaging means as seen from the direction perpendicular to the platen glass.

  Hereinafter, the first embodiment of the present invention will be described with reference to the above five figures.

  In FIG. 1, the image reading apparatus includes a scanner unit 100 as an apparatus body including a document table, and a document feeding device 200 as a document feeding unit that transports a document on the document table. Reference numeral 100 denotes a housing, and includes a book document platen glass 3 constituting a document table and a sheet document platen glass 2 on the top surface of the housing, and a book document platen glass 3 serving as a document table in the housing. There is provided a first image pickup means 1 including a line sensor 11 and a lens 11 for reading a document on the platen glass 2 for sheet document.

  The book original platen glass 3 is provided with a reference white plate 901. The density data of the reference white plate 901 is read by the line sensor 11, and the shading value S1 is generated based on the density data, thereby performing the first imaging. The density of the image read by the unit 1 is corrected.

  The image of the original S on the book original platen glass 3 or the sheet original platen glass 2 is illuminated by the lamp 4, and is lined by the lens 10 while the optical path is bent by the first, second, and third mirrors 5, 7, and 8. The image is formed on the sensor 11 and read by photoelectric conversion.

  Since the first mirror table 6 and the second mirror table 9 are moved at a speed ratio of 2: 1 by driving means (not shown), the document placed on the book document platen glass 3 and the sheet document platen glass 2. To the line sensor 11 is kept constant.

  Further, in this embodiment, the original platen glass is disposed at a position where an image is not blurred on the first imaging unit 1 on an optical axis 503 different from the imaging optical axis 502 of the line sensor 11 of the first imaging unit 1. A second image pickup unit 20 is mounted that images two images while bending the optical path with first, second, and third mirrors 5, 7, and 8, and performs photoelectric conversion.

  As shown in FIG. 8, the second imaging unit 20 has the same main scanning optical axis as that of the first imaging unit so as to minimize the influence of lens aberration on the end of the read signal main scanning direction. .

  Here, the difference in the angle of view between the area sensor and the line sensor will be described with reference to FIG. In the figure, 1000 is an imaging lens, 1001 is an area sensor imaging plane, 1002 is a line sensor imaging plane, 1003 is a line sensor reading area, and 1004 is an area sensor reading area. In this figure, in order to make the difference easy to understand, the horizontal length of the area sensor and the line sensor, the focal length of the imaging lens, and the optical axis are shown as being the same. In the drawing, the horizontal direction coincides with the scanning direction of the image reading apparatus, and the vertical direction coincides with the blowing scanning direction. As can be seen from the figure, even if a lens with the same focal length is used for the area sensor and the line sensor, the difference between HL and HA in the sub-scanning direction is generated in the shooting angle of view, and the area sensor captures a wider area image. Is possible.

  As described above, in order to more effectively implement the present invention, it is desirable that the second imaging unit uses an area sensor, and moreover, an area sensor that has recently been adopted for a mobile phone is used. Since the installation space in the apparatus can be minimized by using the small camera module, the use of this module will be described below.

  Details of the second imaging unit 20 will be described with reference to FIG.

  Reference numeral 20a in FIG. 3 denotes an imaging lens of a small camera module, which rotates the lens barrel to change the lens position along the optical axis and align with the pin. 20b is an electric board having a connector 20g for connecting an image signal circuit in the camera module and a reader control circuit (not shown), 20c is a small camera module body, and 20d is an integrated board of the small camera module and the board. A support plate 20e for supporting and attaching to the reader body, 20e is a caulking shaft attached to the support plate, and a substrate 20b is attached thereon with screws 20f. 20h is a long hole for fitting into the embossing of the mounting partner, and 20g is a screw hole for connecting the second imaging unit to the main body.

  Here, since the small camera module has the TV output as before, the imaging plane is rectangular. In this case, the long side of the imaging plane is in the same direction as the line sensor 11 of the first imaging unit. The size of the image reading apparatus is prevented from being increased in the height direction.

  The second imaging unit 20 having the above configuration is adjusted to a position where a desired image signal can be obtained while adjusting the position in the vertical direction by guiding the long hole 20h when the main body is mounted, and the screw is closed to 20j. Fasten to the main body.

  The document feeder 200 serves as a transport system, a pickup roller 12 that picks up the documents S on the document tray 300 one by one, a separation roller pair 13 that prevents double feeding of the retrieved documents, and the document S as a platen platen. A pair of conveying rollers 14, 15, 16, and 17 that lead to the glass 2, a paper feed guide 904 and a relay paper guide 905, a platen roller 18 that approaches the platen glass 2 for sheet originals, and a paper discharge tray 400 A paper discharge roller pair 19 and a paper discharge paper guide 906 are provided.

  In the case of a flow reading mode in which a document moving at a constant speed is read by the document feeder 200 while the moving optical system is fixed, the first and second mirror stands 6 and 9 are fixed at the positions shown in FIG. Read.

  When reading a book document or a document that cannot be used by the document feeding device 200, the document feeding device 200 is rotated to open the book document platen glass 3, and then the document is placed on the first document mirror. Reading is performed by moving and scanning the stage 6 and the second mirror stage 9.

  The document feeder 200 has a function of pressing and conveying a document to the platen glass 2 for sheet document as a reading unit, and a function of covering and pressing the document on the platen glass 3 for book document.

  Next, the operation will be described with reference to (FIG. 1), (FIG. 2) and (FIG. 5).

After loading the document S on the document tray 300, the start switch 51 of the operation unit 50 is turned on (# 1).
The pickup roller 12 of the automatic document feeder removes and conveys the uppermost document on the tray. Even if several originals are sent out at the same time, they are separated and conveyed by the separation roller pair 13. (# 2)
Then, the sheet is conveyed toward the sheet original platen roller 18 by the next conveyance rollers 14, 15, 16.

Next, the document illumination lamp is turned on, and before the first document S passes through the reading position of the line sensor 11, the mirror table is moved, and the density data of the reference white plate 901 is obtained by the first imaging unit. To obtain the shading value S1. (# 3) (# 4)
The mirror table is moved again, and the density D1 of the platen roller 18 is read by the first imaging unit. (#Five)
Further, in parallel with the above processing, in the second imaging unit 20, when the line sensor 11 reads the density D 1 of the platen roller 18 before the first document S passes the reading position of the line sensor 11. Then, after performing auto white balance adjustment by a circuit in the second imaging unit, the image on the glass surface is taken in and the image signal J1 is taken in the sub memory 50. (# 6)
When the first imaging unit has read D1 and the second imaging unit has read J1, the lamp 4 is turned off. (# 7)
The image data read by the line sensor 11 of the first imaging unit is subjected to shading correction of image density based on the shading value S1. (# 8)
Here, the glass surface image data J0 captured by the second imaging unit 20 in a state where there is no dust or dirt on the surface is captured in advance in the sub memory 51.

After taking in J1, the dust detection circuit 52 is driven, and J0 and J1 are compared to detect dust and dirt on the original glass surface before JOB. (# 9) (# 10)
The image data read by the second imaging unit for dust or dirt detected by the circuit differs in the optical characteristics, the number of pixels, etc., and the read image data from the first imaging unit differs from the pixel data addresses on the memory. Therefore, the moving optical system cannot be changed to a place where there is no dust and dirt with the data as it is. Therefore, in the present invention, this difference is resolved by incorporating a correction circuit in the dust detection circuit, and each pixel address of the image signal of the second imaging unit is made to correspond to the image signal of the first imaging unit. Yes. Here, as described above, the second imaging unit 20 has the same main scanning optical axis as that of the first imaging unit to minimize the influence of lens aberration on the read signal main scanning direction end. The variable for pixel address correction calculation is reduced, and the time required to complete the calculation process can be shortened. (# 11)
Based on the movement amount and direction of the mirror base calculated by the above-described calculation process, the first imaging unit reading position is moved to a position free from dust and dirt. (# 12)
After the above dust avoidance operation is completed, the first document S passes through the reading position of the line sensor 11 at a predetermined speed, whereby reading of the image information on the first page is started by the first imaging unit, and the reading data Is stored in the main memory 55. (#13)
In addition, since floating dust such as paper dust that has entered the platen glass moves in the document conveyance direction, in the dust avoidance position calculation process described above, one of the detected dust positions is the same in the document document conveyance direction. With the upstream side as a reference, the upstream of this position is moved to a position that becomes the reading position of the first imaging means, thereby reducing the probability of sudden image failure due to floating dust. Therefore, the reading position of the first image pickup means is set on the original platen glass at the most downstream side of the original conveyance that can ensure the image quality at the start of the dust detection operation.

  If the movement destination of the reading position cannot be calculated even by the above-described arithmetic processing, the operation is temporarily stopped and a glass surface cleaning warning is given to the user as in the past.

  If no dust or dirt is detected, the process proceeds from (# 10) to (# 13), and the first document S passes through the reading position of the line sensor 11 at a predetermined speed, thereby 1 Reading of the image information of the face is started by the first imaging unit, and the read data is stored in the main memory 55. The document S that has been read is conveyed toward the document discharge tray 400 by the discharge roller 19.

  Thereafter, while the space between the manuscript sheets passes through the flow reading position, the process of reading the density D2 of the platen roller 18 again and the automatic white balance adjustment by the circuit in the second image pickup means are performed, and then the glass surface Processing to capture the image and overwrite the image signal J1 in the sub memory 50, and after taking in J1, the dust detection circuit 52 is driven, J0 and J1 are compared, and dust and dirt on the glass surface are detected to detect dust. After the reading position is set at a position where there is no dirt, the image of the second original S is read by the line sensor 11.

Since the light amount of the lamp 4 changes with time, shading correction of the image density of the second document S is performed based on the corrected shading value S1 according to the change of the density D1. The same operation is repeated for the third and subsequent sheets, and the operation is stopped after the last document S is discharged. (# 14) (# 15)
Note that driving such as paper feed is performed by a motor (not shown).

(Example 2)
The same effect can be obtained by using a line sensor for the second imaging unit, moving the second imaging means by a drive mechanism different from the moving optical system, and scanning and reading the image on the surface of the platen glass.

(Example 3)
The same effects as those of the first and second embodiments can also be obtained in an image reading apparatus equipped with an automatic document feeder that uses a conveyor belt for conveying a document on the platen glass.

1 is an overall view showing an image reading apparatus according to Embodiment 1 of the present invention. FIG. 3 is a block diagram of the first embodiment. The figure explaining a 2nd imaging unit. The figure explaining the difference in the angle of view of an area sensor and a line sensor. Flow chart when reading. The figure which shows the positional relationship of each imaging means seeing from the platen glass perpendicular | vertical direction. The block diagram which shows garbage detection processing.

Claims (6)

  An apparatus main body having a document table, a movable optical system for reading a document image, and a first imaging means having a photoelectric conversion element and an imaging lens for converting a document reflected light from the optical system into an image signal A second image pickup device having a photoelectric conversion element different from the first image pickup device and an imaging lens, and an image incident on the second image pickup device is guided by the movable optical system. A featured image reading apparatus.   2. An image reading apparatus having the feature of claim 1, further comprising dust detection means for detecting foreign matter on the glass surface using a read image signal of the second imaging means.   2. The image reading apparatus having the feature of claim 1, wherein the optical axis in the main scanning direction of the second imaging unit is at least parallel to the optical axis of the first imaging unit.   2. The image reading apparatus having the characteristics of claim 1, wherein the photoelectric conversion element of the second imaging unit is an area sensor.   2. The image reading apparatus according to claim 1, wherein the second imaging unit reads an image when there is no document image at the image formation position. An image reading apparatus having the feature of claim 2 and an automatic document feeder, wherein the image is read by the second image pickup means only in a flow reading mode in which the first image pickup means reads the document while conveying the original. Reader.

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