JP4136618B2 - Image reading device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus.
[0002]
[Prior art]
Conventionally, when reading a double-sided document, an ADF has a document reversing mechanism. First, the image front side is read by the image reading device, and after the reading is finished, the document is reversed by the document reversing mechanism inside the ADF, and the back side of the document is read. The image reading device side performs an operation of reading and reads a double-sided original image.
[0003]
However, in this configuration, the time for reversing the document becomes a dead time as a reading device, which reduces reading performance and often damages the document because the document is reversed.
[0004]
In view of this problem, in recent years, a one-pass double-sided image reading apparatus has been proposed in which a reading system is provided in the ADF and a front image and a back image are read by a single document conveying operation.
[0005]
A reading operation of the one-pass double-sided image reading apparatus will be described.
[0006]
FIG. 2 is a diagram showing a schematic configuration diagram of the one-pass duplex reading apparatus.
[0007]
A plurality of double-sided originals placed on the original placing table 71 of the ADF 70 are conveyed one by one. The document is separated and conveyed one by one by the separation rollers 72 and 73 along the conveyance path, and the document is conveyed along the conveyance guides 74 and 77 according to the rotation of the conveyance roller 75 in the arrow direction.
[0008]
By the time the document is conveyed to the reading position, the reading unit 200 moves immediately below the shading correction plate 211 and performs shading correction. When the shading correction is completed, the reading unit 200 moves immediately below the flow reading window 212 and enters a reading standby state until the document is conveyed.
[0009]
When the document is conveyed, the surface image of the document is read directly below the conveyance roller 75. That is, the line image of the original image illuminated by the lamp 201 in the image reading apparatus 200 is imaged on the CCD 209 via the first mirror 205, the second mirror 206, the third mirror 207, and the lens 208, and the line image Reading is done. The conveyance roller 75 conveys the document at a predetermined speed, sequentially reads the document in the sub-scanning direction, and reads the surface image of the document. When the reading of the front side original image proceeds and the end portion of the original is conveyed directly below the equal magnification reading box 250, the image on the back side of the original is read by the equal magnification reading box 250. The optical system of the 1 × magnification reading box 250 includes a Selfoc lens 251, a contact sensor 252, and a lamp 253, and a line image of the back side image of the original illuminated by the lamp 253 is displayed on the contact sensor 252 via the Selfoc lens 251. To form an image. Reference numeral 254 denotes a platen, and the original passes through the upper surface of the platen when reading the original. The line image formed on the contact sensor is an equal magnification image. Since the transport roller 75 transports the document at a predetermined speed, the document is sequentially read in the sub-scanning direction, and the back image of the document is read. The double-sided originals that have been read are sequentially discharged onto a discharge tray section 78.
[0010]
The front and back image data read in this way is sent to an image processing circuit (not shown), and the image is reproduced by a host computer or a printer connected to the image reading device, and the image is displayed on a display or print paper. An image forming process is performed to form the image.
[0011]
On the other hand, when reading a book-type document such as a spread book, the ADF 70 is opened, the document is placed on the document glass, and the reading unit 200, the second mirror table, and the third mirror table are placed in the right direction in FIG. Scan and read the original image.
[0012]
[Problems to be solved by the invention]
However, since the reading box 250 is fixed in the shading correction of the reading box 250, the platen 254 can only be used as a shading plate. However, if dust adheres to the platen 254, the shading correction data for one line is correct. For example, an original image read by a pixel where black dust adheres is over-corrected in shading data, resulting in a white line in the sub-scanning direction. In order to create shading data, the platen 254 needs to be made of a white member to some extent. However, when the original is thin, the phenomenon of show-through occurs due to the influence of light reflected from the platen 254. There is.
[0013]
The show-through will be described with reference to FIG.
[0014]
FIG. 3A is a front image of the double-sided document 30. Similarly, FIG. 3B is a back side image of the double-sided original 30. When such an original is read by the image reading apparatus shown in FIG. 2, the reproduced image of the back image read by the reading box 250 is as shown in FIG. It can be seen that the image information of the front image (a) is thin and appears in the back reproduction image. If the original 30 is a monochrome binary original, the image may be reproduced by adjusting the contrast and density at the time of reading the image data. However, if the original is a color original, adjusting the contrast and density itself may be performed by changing the color of the original. It is difficult to say that it is the best method.
[0015]
The same can be said for reading a front document.
[0016]
That is, when the reading unit 200 reads the surface image of the double-sided document, if there is dust at the reading position on the flow reading window 212, the pixel at the spot where the dust is attached always reads the dust image. If it is dust, it becomes a black streak in the sub-scanning direction, and if it is white dust, it becomes a white streak in the sub-scanning direction.
[0017]
Therefore, in order to detect dust on the flow reading window 212, the surface of the conveyance roller 75 is read through the flow reading window 212 while rotating the conveyance roller 75, and dust attached to the flow reading window 212 is detected. By such a dust detection method, dust attached to the transport rotor 75 is not determined to be dust attached to the reading window 212. For example, when the read data has a lower value than the surrounding pixel data, the pixel position is determined. Judge that black dust has adhered. In this case, for example, interpolation data of pixels with dust can be created from surrounding pixels without dust, and a reproduced image in which dust is not noticeable can be output. For this reason, black dust cannot be detected unless the member color of the conveying roller 75 is a white member to some extent. However, if the conveying roller is made of a white member, the influence of the show-through described above cannot be avoided. FIG. 3D shows the show-through state of the surface image.
[0018]
Further, when the attached dust is white dust, there is a problem that the detection accuracy is extremely low.
[0019]
As a proposal to eliminate the influence of show-through, there is an example in which a reference white plate that can be inserted and retracted is provided by causing Hei 06-062245 to select a non-reflective surface or a white background at the reading position according to an operator's instruction. Although the mechanism for inserting and retracting the reference white plate becomes complicated, it is not practical, and if the operator makes a mistake, the desired reading result cannot be obtained.
[0020]
Further, in 2000-059569, a proposal has been made to provide a white part and a black part on a member such as a square member, and to change the surface of the member as necessary. However, since cost and space are required for driving the member, it is a practical avoidance. It's not a good idea.
[0021]
[Means for Solving the Problems]
In view of the above problems, the present invention includes a first image reading unit for reading a front surface image of a document, and a second image reading unit for reading a back surface image of the document. An image reading apparatus capable of reading a document illumination light source of the first image reading unit in a state where the first image reading unit and the second image reading unit face each other. In the state where the original illumination light source of the second image reading unit is turned off, the reading operation by the second image reading unit is executed, so that the dust existing on the reading optical path of the second image reading unit Is detected .
[0026]
DETAILED DESCRIPTION OF THE INVENTION
(Example 1)
Embodiments of the present invention will be described with reference to the drawings.
[0027]
FIG. 1 is a schematic configuration diagram of a double-sided image reading apparatus according to an embodiment reflecting the present invention. Of the constituent members, the same members as those in FIG.
[0028]
The difference from FIG. 2 is that the reading unit 200 of FIG. 2 is replaced with a contact image sensor (hereinafter CIS) 10 in FIG. The CIS 10 has a configuration close to that of the reading box 250 in FIG. 1 and includes an equal-size image reading sensor.
[0029]
The configuration of the CIS 10 is shown in FIG.
[0030]
FIG. 4 is a diagram showing a schematic configuration of the CIS 10. A line image of the original illuminated by the light sources 42-1 and 42-2 is formed on the line sensor 41 through the self-focus lens 43 at the same magnification. The line sensor 41 has 7050 pixels at a 42.3 μm pitch, and can read a 297 mm line image at 600 dpi. The member 13 is a white member and has a uniform density D = 0.3, which is equivalent to that of the shading correction plate. The member 14 is a black member and has a uniform density of black density D = 1.6 of a general printed matter. As shown in FIG. 4, the white member 13 and the black member 14 are configured to be arranged horizontally as constituent members of the CIS 10.
[0031]
If such a CIS is used for the reading system of FIG. 2, the mechanical members and optical members of the reading system can be largely omitted, and a compact image reading apparatus can be constructed. When reading a double-sided document using the ADF 70, the CIS 10 reads the surface image of the document. The roles of the white member 13 and the black member 14 will be described later.
[0032]
Returning to FIG. 1, the description of the image reading apparatus will be continued.
[0033]
The CIS 11 is a line image reading sensor having the same configuration as the CIS 10. Since the configuration is almost the same as that of CIS 10, the description of the configuration is omitted. Reference numeral 12 denotes a protective glass, which is a member provided so that dust and dust adhering to a document generated in the course of transporting the document when the ADF 70 is used are not mixed into the CIS 11. When reading a double-sided original using the ADF 70, the CIS 11 reads the back image of the original.
[0034]
Hereinafter, the operation at the time of reading a single-sided original and at the time of reading a double-sided original will be described with reference to FIG.
[0035]
(Single-sided original scanning)
When the reading command is input by the operator, the image reading apparatus performs the shading correction by the shading plate 211 with the CIS 10 arranged as shown in FIG. At the time of shading correction, the document illumination lamp of the CIS 10 is turned on and the shading correction plate 211 is read. The shading correction plate 211 is colored to a uniform white density, and corrects the output non-uniformity maintained by each pixel of the CIS 10 and the illumination unevenness of the document illumination lamp, so that the signal output characteristics obtained from each pixel of the CIS 10 are uniform. The signal is corrected by a shading circuit (not shown) in the subsequent stage.
[0036]
In addition, if dust is present on the shading plate 211 during the shading correction, the shading correction parameter of the pixel from which the dust is read becomes an excessive value, and white stripes are generated in the read image.
[0037]
The white line generation algorithm will be described.
[0038]
FIG. 6 shows output characteristics of the CIS 10 obtained by reading the shading correction plate before the shading correction. The horizontal axis represents the pixel address, and the vertical axis represents the reading level. The reading level ranges from 0 to 255, and image data of 256 gradations is output. Since the numerical value represents luminance, black is 0 and white is 255.
[0039]
In FIG. 6, there is dust at the position X, and the read value of the read data is smaller than that of other pixels.
[0040]
When the shading correction is performed as it is, when the reading target value of the shading plate is 245, the output characteristics after the shading correction are as shown in FIG. In FIG. 7, the location where dust is present is corrected so as to become the target value 245.
[0041]
However, since the pixel output is not low at the X position, for example, when a document having the same density as the shading plate 211 is read, the result is as shown in FIG. If a document having an intermediate density as shown in FIG. 9A is read as it is, an image is reproduced as shown in FIG. 9B.
[0042]
In order to eliminate this problem, when performing the shading correction in the member arrangement of FIG. 5, the shading data is sampled a plurality of times while gradually moving the CIS 10 in the direction of the arrow A or B in the figure, and the average value is obtained. Can be used as final shading data. Such a shading correction method is referred to as “movement shading”.
[0043]
When moving shading is performed, even if dust is present when the shading plate 211 is read a plurality of times, the influence of dust is reduced by the averaging process. The shading characteristics after the moving shading are uniform as shown in FIG. 7 even when a document having the same density as the shading plate 211 is read.
[0044]
When the shading correction process is completed, the image reading apparatus moves the CIS 10 to the position shown in FIG. 10, moves the CIS 10 at a predetermined speed in the direction of the arrow, reads continuous line images of the document 71, and reads a desired image range of the document 71. Read. The read image is reproduced by a connected printer or host computer. When reading a single-sided original, the ADF 70 serves only as a pressure plate for pressing the original 51 against the original platen glass 203, and is electrically in a standby state.
[0045]
(Double-sided original scanning)
In the case of reading a double-sided document, when a reading command is input by an operator, the image reading apparatus first performs shading correction by the shading plate 211 with the CIS 10 arranged as shown in FIG. The shading correction procedure is the same as described in the section of (Single-sided original reading), and is omitted here.
[0046]
After the CIS 10 shading correction is completed, the CIS 11 shading correction is performed.
[0047]
At the time of shading correction of the CIS 11, the image reading apparatus controls the white member 13 to be arranged at the reading position of the CIS 11 by moving the CIS 10 to the position of FIG.
[0048]
When the shading correction is started, the CIS 11 turns on the built-in document illumination lamp, illuminates the white member 13, reads the white member 13, and creates shading correction data. At this time, since the focus position of the CIS 11 is the upper part of the flow reading window 212 through which the document is conveyed by the ADF 70, the white member 13 is not in focus, so the reading level may be lowered. If the target value is set low, data equivalent to the shading data by the pair of the CIS 10 and the shading plate 211 can be obtained. For example, the shading target value may be set to 235.
[0049]
The problem of the white streak image is the same for the CIS 11 reading. If dust adheres to the white member 13, a white streak image as described in the section (Single-sided original reading) is generated. In order to eliminate this problem, when performing the shading correction in the member arrangement of FIG. 10, the shading data is sampled a plurality of times while gradually moving the CIS 11 in the direction of the arrow A or B in the figure, and the average value is obtained. It is sufficient to perform movement shading as final shading data.
[0050]
As described above, when the shading correction of the CIS 10 and the CIS 11 is completed, the image reading apparatus sets each member to the member arrangement shown in FIG.
[0051]
FIG. 12 is a diagram illustrating a state where two double-sided originals are placed on the tray 71 and the back image of the first original is about to be read by the CIS 11.
[0052]
The originals 51-1 and 51-2 placed on the tray 71 are first separated from the original 51-2 by the separation rollers 72 and 73 and the original is guided to the guides 74 and 77 by the transport roller 75. Be transported. When the leading edge of the document reaches the reading position of the CIS 11, reading of the back image of the document 51-1 is started. Since the black member 14 is arranged at the back of the reading position of the CIS 11, the reflected light transmitted through the original does not enter the CIS 11, and the influence of the show-through is reduced, so that the line image of the back image of the original 51-1. Read continuously.
[0053]
When conveyance of the original 51-1 and reading by the CIS 11 proceed, the leading edge of the original 51-1 reaches the position shown in FIG. 13, and reading of the surface image of the original 51-1 by the CIS 10 is started. A surface emitting sheet 15 is provided on the back of the reading position of the CIS 10. The surface emitting sheet is used for a liquid crystal backlight of a notebook personal computer and has a characteristic of emitting light when a predetermined voltage is applied. When no voltage is applied, the light is turned off and the sheet is close to black. When reading the original, the surface emitting sheet 15 is turned off so that the reflected light transmitted through the original does not enter the CIS 10 and the influence of the show-through is reduced, and the line image of the surface image of the original 51-1 is continuously read. It is done. The control when the surface emitting sheet 15 is caused to emit light will be described later.
[0054]
In this way, the double-sided image of the double-sided original 51-1 is read substantially simultaneously.
[0055]
When the front end of the double-sided document 51-1 is read by the CIS 10, the ADF 70 discharges the document 51-1 to the tray 78 and then feeds the document 51-2. I do.
[0056]
Although the arrangement relationship between the black member 14 and the white member 13 may be reversed, the reading positions of the CIS 10 and the CIS 11 should be separated as much as possible in order to avoid the influence of the light sources of the CIS 10 and the CIS 11 when reading both sides.
[0057]
Accordingly, as described above, it can be said that the black member 14 is preferably connected to the white member 13 and the white member 13 is preferably connected to the CIS 10.
[0058]
The double-sided image data read by the above control is reproduced by a connected printer or host computer.
[0059]
(Example 2)
In the first embodiment, reading of a double-sided image including shading correction has been described. However, when a line image is read with the reading unit fixed while conveying a document as in the first embodiment, dust adhered to the reading unit. You must be careful about the effects of In the example of the configuration of FIG. 13, when dust is attached to the reading position of the protective glass 12 of the CIS 11 or when dust is attached to the reading position of the flow reading window 212 of the CIS 10, the line sensor between the CIS 11 or the CIS 10 and the document is placed. There is always dust, and during the image reading, these dusts are always read. As a result, dust lines are reproduced in the reproduced image in the sub-scanning direction.
[0060]
In order to solve this problem, dust detection processing is performed.
[0061]
First, the control when performing dust detection of the CIS 10 will be described.
[0062]
When detecting dust adhering to the flow reading window 212 which is a reading point of the CIS 10, the CIS 10 is arranged as shown in FIG. 14 without placing the original.
[0063]
In this arrangement state, the surface emitting sheet 15 is caused to emit light. The document illumination lamp built in the CIS 10 is turned off.
[0064]
By performing such control, if dust adheres to the reading point of the CIS 10 on the flow reading window 212, the dust becomes a shadow because it is backlit against the light incident from the opposite side of the CIS 10. Whether the color of the dust is white or black, the reading of the CIS 10 becomes a black image.
[0065]
Therefore, the image processing circuit of the CIS 10 compares the read data with the surrounding pixels, and can determine that there is dust at the pixel position where the output level is extremely lowered.
[0066]
Similarly, when detecting dust adhering to the protective glass 12 of the CIS 11, the CIS 10 is arranged as shown in FIG. 15 without placing a document.
[0067]
In this arrangement state, the document illumination lamp built in the CIS 10 is turned on, and at the same time, the document illumination lamp built in the CIS 10 is turned off.
[0068]
By performing such control, when dust adheres to the reading point of the CIS 11 on the protective glass 12, the dust becomes a shadow due to the backlight against the light incident from the opposite side of the CIS 11. Regardless of whether the color of the image is white or black, the reading of the CIS 11 becomes a black image.
[0069]
Therefore, the CIS 11 image processing circuit compares the read data with the surrounding pixels, and can determine that there is dust at the pixel position where the output level is extremely lowered.
[0070]
As described above, when dust detection of CIS10 and CIS11 is performed, the process of detecting dust again by slightly shifting the reading position is repeated to perform control for searching for a reading position without dust, or it is determined that there is dust. As the pixel data, it is possible to output image data in which no dust lines occur by a method such as creating interpolation data from surrounding pixel data and performing image processing to replace the interpolation data.
[0071]
【The invention's effect】
As described above , according to the present invention, the document illumination light source of the first image reading unit is turned on and the second image reading unit and the second image reading unit face each other. In the state where the original illumination light source of the image reading unit is turned off, the reading operation by the second image reading unit is executed to detect the dust existing on the reading optical path of the second image reading unit. Detection accuracy can be increased.
[Brief description of the drawings]
FIG. 1 is a schematic view of a double-sided image reading apparatus embodying the present invention. FIG. 2 is a schematic view of a conventional double-sided image reading apparatus. FIG. 3 is a view showing a show-through state. Schematic diagram of CIS for reading an image FIG. 5 is a diagram showing the arrangement relationship of members when the CIS 10 performs shading correction. FIG. 6 is a diagram showing a reading state when there is dust on the shading plate. FIG. 8 is a diagram showing a reading state of a shading plate after shading correction. FIG. 8 is a diagram showing a reading state of a document after shading correction. FIG. 9 is a diagram showing a state of document reproduction when dust is found on the shading plate. 10 is a diagram illustrating an operation when a single-sided original is read by a double-sided image reading device. FIG. 11 is a diagram illustrating an operation when performing shading correction of CIS11 in the double-sided image reading device. In Figure 12 shows the double-sided image reading apparatus, shows the member arrangement for reading a two-sided document (back side document reading start)
FIG. 13 is a diagram showing a member arrangement when reading a double-sided document with a double-sided image reading device (at the time of starting a front-side document reading).
FIG. 14 is a diagram showing a member arrangement at the time of dust detection by the CIS10 in the double-sided image reading device. FIG. 15 is a diagram showing a member arrangement at the time of dust detection by the CIS11 in the double-sided image reading device.
10, 11 CIS
12 Protective glass 13 White member 14 Black member 41 Line sensors 42-1 and 42-2 Document illumination lamp 43 Self-focus lens array 15 Light-emitting sheet 206 Second mirror 207 Third mirror 208 Lens 209 CCD
210 Document pressure plate 211 Shading correction plate 301 Analog amplifier 302 A / D converter 303 Shading correction circuit 304 I / F circuit 501 Switch 502 Line memory 503 Multiplier 71 White streak 1001 I / F circuit 1002 Log conversion circuit 1003 Edge enhancement circuit 1004 γ Conversion circuit 1005 Binary processing circuit

Claims (3)

The first image reading unit, and a second image reading means for reading a back surface image of the document, an image reading apparatus which can take read images on both sides of the document for reading the surface image of the document Because
With the first image reading unit and the second image reading unit facing each other, the original illumination light source of the first image reading unit is turned on, and the original illumination light source of the second image reading unit An image reading apparatus for detecting dust existing on a reading optical path of the second image reading unit by executing a reading operation by the second image reading unit in a state where the light is turned off. The first image reading means for reading an image of a document is movable and includes a light emitter disposed at a position facing the first image reading means, and the light emitter is caused to emit light. in a state where the document illumination light source is turned off in the first image reading means, by performing a read operation by the first image reading means, detecting the dust present in the reading light path of the first image reading means The image reading apparatus according to claim 1, wherein: 3. The reading device according to claim 2, wherein when the original image is read by the first image reading unit, the light emitting body is turned off so that the light emitting body functions as a background member for reducing the show-through of the document. The image reading apparatus described .

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