JPH09149253A - Image reading device - Google Patents

Abstract

(57) [PROBLEMS] To correct an image read from a reading surface on the basis of an image on the back surface to realize reading of only an image formed on the reading surface without influence of show-through. It is an object of the present invention to provide an image reading apparatus capable of reading an image with high quality even on a document with show-through. SOLUTION: A first reading unit 23 that reads an image by taking in reflected light from one surface of a transported document P by an image sensor 22, and a second reading unit 23 that similarly reads an image on the other surface of the document. Only the image formed on one side of the document by subtracting the output of the image data of the reading unit 26 and one of the one side or the other side of the image data while reducing and correcting the left and right of the main scanning direction Show-through correction units 35a and 35b for correcting the image data of FIG.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device, and more particularly, to an image reading device capable of reading an image on a reading surface from an original without being influenced by an image on the back surface.

[0002]

2. Description of the Related Art Conventionally, there has been known an image reading apparatus which moves one of a document and a reading unit relative to the other to read an image from the document. The image reading apparatus is a copying machine or a facsimile machine. It is installed in. An example of this type of image reading apparatus is, for example, Japanese Patent Laid-Open No. 3-107.
276. This image reading device,
In recent years, the number of originals with images formed on both sides is increasing for cost saving and effective use of resources, but reading units for reading images from the originals are provided on both sides of the original to read images from one side and the other. By alternately performing the above steps, the image can be read from both sides of the original at once.

[0003]

However, in such a conventional image reading apparatus, since the image is simply read from both sides of the original at a time, it is necessary to use the original in the case of a thick paper original. However, there is a problem that the quality of the read image is low in the case of a thin document whose back side image is reflected on the reading side. Needless to say, this problem is not limited to an image reading device that reads images from both sides of a document, but also an image reading device that reads images from one side of a document with images formed on both sides.

Therefore, according to the present invention, by correcting the image read from the reading surface on the basis of the image on the back surface, the reading of the image from the reading surface without the influence of the show-through is realized, and the original document with the show-through appears. However, it is an object of the present invention to provide an image reading device capable of reading an image with high quality.

[0005]

In order to achieve the above object, the invention according to claim 1 is a reading means for reading an image from both sides of a document and outputting converted image data, and one side output from the reading means. Alternatively, a correction unit that corrects one image data of the other surface based on the other image data to make image data of only the image formed on one surface of the document is provided.

According to the first aspect of the invention, only the image formed on the reading surface is based on the image data read from one surface or the other surface as the reading surface and the image data read from the other surface which is the back surface. Corrected to image data. Therefore, the image data of the image on the back surface that is reflected on the reading surface is removed, and the image formed on the reading surface can be read.

According to a second aspect of the invention, in addition to the configuration of the first aspect of the invention, the correction means performs a reduction correction from the output of one image data and the other side of the original in the main scanning direction is reversed. The image data output is subtracted. According to the second aspect of the present invention, the output of the back side image data is corrected to be reduced, and the left and right sides of the document in the main scanning direction are reversed, so that the processed back side image data is converted from the image data read from the reading surface. Is subtracted. Therefore, it is possible to subtract the output and image data on the back surface that is transmitted (shown through) on the reading surface from the image data on the reading surface.

[0008] The invention described in claim 3 is claim 1 or 2.
In addition to the configuration of the invention described in (1), the reading unit includes a first reading unit that reads an image from one surface of the document, a second reading unit that reads an image from the other surface of the document, and the document or the first and second documents.
And a moving unit that moves one of the reading units relative to the other, and the first and second reading units move the reading unit from both sides of the document by a single movement of the document by the moving unit. It is characterized by reading an image.

According to the third aspect of the invention, the image data is read at once from both the reading surface and the back surface of the original. Therefore, both image data can be read only by the displacement of the arrangement positions of the first and second reading units without repeating the relative movement of the document. Here, the image reading apparatus to which the present invention is applied is not limited to one having both sides of the original as the reading surface, and may have only one side of the original as the reading surface. Further, it goes without saying that the reading means of the document reading apparatus according to the first or second aspect may read the image from both sides of the document by circulating the document.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 to 10 are views showing an example of a facsimile apparatus equipped with an embodiment of an image reading apparatus according to the present invention. First, the configuration will be described. FIG. 1 is a diagram showing the overall configuration of a facsimile apparatus.

Referring to FIG. 1, the facsimile apparatus includes a system controller 11 for integrally controlling each section of the apparatus according to a program stored in advance, an operation section 12 for inputting settings and commands by an operator, and a communication line. A communication processing unit 13 that transmits and receives image data to and from a destination, a scanner (image reading device) 14 that reads an image from a document to be transmitted or copied and outputs the converted image data, and a reading (transmission / transmission / transmission). (Copy) or an image memory 15 for temporarily storing the received image data, and an electrostatic latent image formed by irradiating a laser diode on the photosensitive member based on the stored image data is visible on a recording medium in a so-called electrophotographic process. An image reproducing unit 16 that transfers and records the recording medium on a sheet after image formation and reproduces and outputs the image, and a document reading operation or an image reproducing operation. A mechanical control unit 17 that controls the timing of mechanical driving for conveying an original or a sheet in accordance with an instruction sent from the system controller 21 is connected via a system bus 18, and the system controller 11 includes an operation unit 12 A document (image) is transmitted or copied according to the operation input inputted from, and when the image data is transmitted, it is automatically received and the image is reproduced and output.

In this facsimile apparatus, it is possible to specify from the operation unit 12 that processing (transmission or copying) is performed by reading one side or both sides of a document by the scanner 14, and the scanner 14 is designated as double-sided reading. In the case where the image data has been read, both side images are simultaneously read according to the instruction of the system controller 11 and the image data is sent to the image memory 15. The image data on the surface side is separately stored.

Next, FIGS. 2 to 4 are views showing the configuration of the scanner 14. 2 and 3, the scanner 14 is
Arrange the reflected light of the light emitted from the light source 21 on one side of the document so that the image sensor 22 corresponds to each read pixel (array)
A photoelectric conversion unit for each line in the main scanning direction by the received light receiving element to output a read image signal (image data);
And a second reading unit 26 that outputs the image signal read by the image sensor 25 when the light source 24 irradiates the other surface of the original, and is placed at a position sandwiching the conveyance path for conveying the original P. The document P is arranged so that a pair of transport rollers, which are rotated in the transport direction (sub-scanning direction) by a transport unit (not shown), such as a document transport motor, sandwiches the document P in the press contact portion, and the document is read in the direction of the arrow in FIG. It is designed to be transported relative to 26. The scanner 14 prevents the light emitted from one of the light sources 21 and 24 from affecting the reading of the other image sensor 25 or 22 at the time of reading the leading edge or the trailing edge of the document, for example. The reference white plates 27 and 28, which are used at the time of shading correction to be described later, are arranged at positions opposed to each other with the conveyance path of the image sensors 22 and 25 interposed therebetween, respectively. White plates 27 and 28 block light from the light source 21 or 24 to the other image sensor 25 or 22.

The scanner 14 includes an image sensor 2 so that images can be read simultaneously from both sides of a document.
Image signals (image data) from 2 and 25 are processed by different systems, and the image signals read by the image sensors 22 and 25 are analog signal processing units 31 respectively.
a, 31b, analog / digital (A / D) converter 32a,
32b, offset correction units 33a and 33b, shading correction units 34a and 34b, show-through correction units 35a and 35b, filter processing units 36a and 36b, main scanning scaling processing units 37a and 37b, and gradation processing units 38a and 38b. It is sent to the image memory 15 via the. Then, the scanner 14 sends the image signal from the image sensor 22 which reads the image on the one side of the document in advance from the shading correction section 34a to the both of the show-through correction sections 35a and 35b after passing through the delay memory 39. The image signal from the image sensor 25 that reads the image on the other side of the document is directly output from the shading correction section 34b to the show-through correction section 35b.
It is designed to be sent to both a and 35b.

Individually, analog signal processing units 31a and 31b are provided.
Adjusts the analog waveform by performing level conversion, sample hold, signal amplification, and impedance conversion of the image signal, and A / D converters 32a and 32b quantize the analog image signal into a digital signal having a predetermined number of bits. Convert. Up to this point, the image signal is output according to the reflectance of the reading surface (one surface or the other surface) of the original read by the image sensors 22 and 25. The whiter the output value, the blacker the output value. There is.

The offset correction units 33a and 33b are provided for each pixel of the image signals from the image sensors 22 and 25 sent from the A / D converters 32a and 32b in the dark (when the light sources 21 and 24 are off). Store output values in memory (not shown)
However, by subtracting the read output value in the darkness from the output value of each pixel actually read in the bright time (when the light sources 21 and 24 are turned on), the image signal output from the image sensors 22 and 25 (output The DC component variation of (value) is corrected (offset correction).

When the shading correction units 34a and 34b read the offset-corrected image signals sent from the offset correction units 33a and 33b on the reference white plates 27 and 28 having a uniform reflectance, prior to reading the original image. The image signal of each pixel when reading the original is normalized based on the white output value of each pixel of, the uneven light amount of the light sources 21 and 24, the influence of optical components such as lenses and mirrors, and the image sensors 22 and 25. The sensitivity variation for each pixel is corrected (shading correction). Then, the shading correction unit 34a sends the image signal after the shading correction to the delay memory 39, and the shading correction unit 34b sends it to both the show-through correction units 35a and 35b. The output value of the image signal after the shading correction is 0 for perfect white and takes a large value as the density increases. For example, when the number of gradations is 8 bits, perfect black is 255. Become.

The delay memory 39 includes a shading correction unit 34.
The image signal read by the image sensor 22 sent from a is delayed, the deviation of the reading position in the sub-scanning direction from the image sensor 25 is corrected, and the image signal is sent to both the show-through correction units 35a and 35b. The processing circuit in the latter stage is capable of processing the image signals of the same line corresponding to both the front and back sides of the document. Specifically, this delay memory 39 is FiFo.
The (First-in First-out) memory configuration is designed to delay the line by the deviation (the number of lines) of the reading position on the front and back sides of the document, and the generated delay amount can be varied. Perform a predetermined operation according to the instruction. Note that this delay of the image signal can be omitted when the entire image is read, stored in the memory, and then read and processed, but it takes time to write and read the read image signal. It is more preferable to delay the processing during the reading operation as in the embodiment.

The show-through correction sections 35a and 35b transmit the image signals of the reading surface (one side and the other side) sent from the shading correction section 34b and the delay memory 39 as the same line corresponding to the front and back sides of the original. Only the image formed on the reading surface by extracting the image signal (output value) due to the show-through on the reading surface of the image formed on the back surface using the image signal obtained by reading the back surface (other surface, one surface) The image signal is corrected. As shown in FIG. 4, the show-through correction units 35a and 35b each include a linear conversion processing unit 41, a mirroring processing unit 42, a line delay memory 43, and a subtractor 44, and the input 1
The show-through correction processing is executed by inputting a read image signal read from the reading surface and input 2 as a correction image signal read from the back surface. That is, the show-through correction unit 35
A and 35b form a correction means.

Individually, the linear conversion processing unit 41 determines the output value of the correction image signal by 1 / x (back surface) by a multiplier or by referring to a conversion table stored in advance in a memory (not shown). The image is converted into a transmittance that shows through (transmits) the image on the reading surface, and the output value at the time of show-through is extracted. It is preferable that the linearly converted 1 / x can be changed from the operation unit 12, and the influence of the show-through is optimized according to the reading result (reproduction output result) and the paper thickness of the document P. It can be eliminated under any condition. Also,
When the output value x of the correction image signal is processed as a power of 2, it is sufficient to simply shift the binary digit.

The mirroring processing section 42 carries out a mirroring processing for changing the position of the correction image signal line by line in the main scanning direction because the image on the back side, which is the back-view, is reversed from the reading side. Send out. Specifically, the mirroring processing unit 42 executes the mirroring processing by address control of the memory, sequentially writes from the address 0 to the address n, and reads from the address n to the address 0 in reverse on the next line.

The line delay memory 43 reads the read image signal because the mirroring correction image signal, that is, the image signal to be displayed on the back side, causes line delay due to writing / reading to / from the memory in the mirroring processing unit 42. Is delayed so as to be aligned with the correction image signal, and then sent to a subtractor 44. The subtractor 44 subtracts the output value extracted from the correction image signal from the output value of the read image signal to remove the image signal of the back side image from the back side image from the read side image signal to form on the read side. The image signal of only the displayed image and the filter processing unit 36a,
Send to 36b.

The filter processing units 36a and 36b open the apertures of the optical components and the light-receiving surfaces of the image sensors 22 and 25 of the image signals sent from the show-through correction units 35a and 35b and subjected to the show-through correction processing. Degree, afterimage, MTF (Modulation Transfer Func) caused by an integration effect (conveyance deviation) in the sub-scanning direction that occurs when a document is conveyed, and scanning unevenness.
compensation). Specifically, the filter processing units 36a and 36b perform spatial filtering processing to enhance high-frequency components of the image signal and restore blur of the image.

The main-scanning scaling units 37a and 37b are arranged in the light-receiving element arrays of the image sensors 22 and 25 which have been filtered.
A virtual sampling point corresponding to the scaling factor set by the operation unit 12 and instructed by the system controller 11 is calculated for the image signal for each pixel corresponding to the pair 1, and the output value at that position is complementarily calculated. To obtain the image signal after scaling.
The scaling in the sub-scanning direction is realized by changing the transport speed of the document transport motor.

The gradation processing units 38a and 38b binarize or multivalue (requantize) an image signal having multivalued gradation information (output value). Next, the operation will be described with reference to FIGS. In FIG. 5, the alphabet "F" is on one side.
When an image is read from a document P on which the letters “L” and the letter “L” of the alphabet is formed on the other surface and the image is processed, the document P is displayed on the reading surface when the document P is a thick paper having a sufficient thickness. The image on the back does not show through. However, when the original P is a thin paper, as shown by the broken line in FIG. 6, the image on the back side is a so-called mirror image in which the left and right sides are reversed from the state viewed from the front, and the density becomes 1 / x. At (for example, a transmittance of about 20% (less than)), the image is thinly reflected and looks like an image formed on the reading surface.

Image signals F read by the image sensors 22 and 25 for images on these reading surfaces (one surface and the other surface),
L is an analog signal processing unit 31a, 31b, an analog / digital (A / D) converter 32a, 32b, an offset correction unit 33a, 33b, and a shading correction unit 34a, respectively.
The image signal F from the shading correction unit 34a is input to both the show-through correction units 35a and 35b via 34b. The corrected show-through correction unit 35a,
Sent to 35b. Therefore, the same line of the corresponding image signals F and L on the front and back of the document P can be processed quickly during the reading operation.

The image signals F and L are, for example, in the line AB shown in FIG. 6, as shown in FIG. 7 in which the horizontal axis represents the main scanning direction and the vertical axis represents the output value. The output waveform has the density of the show-through image added. Next, the correction image signals F and L input from the input 2 of the other system in the show-through correction units 35a and 35b are converted into 1 / x output values by the linear conversion processing unit 41 as shown in FIG. Then, the correction image signals F ₁ and L ₁ of the output waveform when the show-through is performed are extracted and input to the mirroring processing unit 42. Next, as shown in FIG. 9, the correction image signals F ₁ and L ₁ are output waveforms when a show-through image whose left and right are reversed is read by a mirroring process in which the positions thereof are switched in the main scanning direction by the mirroring processing unit 42. The corrected image signals F ₂ and L ₂ are input to the subtractor 44.

On the other hand, the read image signals F and L input from the input 1 of one system in the show-through correction units 35a and 35b are synchronized with the processing of the correction image signals F and L by the line delay memory 43. It is delayed and input to the subtractor 44. And
As shown in FIG. 10, the read image signals F and L are image signals F ₀ and L _{0 obtained} by subtracting the correction image signals F ₂ and L ₂ by the subtractor 44 and reading only the image formed on the reading surface.
Is corrected to the output waveform of
b, main-scanning scaling units 37a and 37b, and gradation processing unit 38
It is sent to the image memory 15 via a and 38b.

As described above, in the present embodiment, the document P
The image signals F and L read from both sides of the image are used as the read image signal and the correction image signal, and the output value is reduced and corrected from one (one surface or the other surface) of the read image signals F and L and the other ( Since the correction image signals L ₂ and F ₂ on the other surface or one surface are subtracted, the image that is visible on the reading surface can be excluded, and only the image formed on the reading surface can be obtained. Therefore, it is possible to easily read the image on the reading surface with high quality even for the original P having the show-through.

At this time, the correction image signals F and L are
In the case of a gradation image, for example, when the original P is transmitted and the transmittance is reduced so that the density is reflected on the reading surface, the correction is performed and the image is judged to be reflected by a threshold value. In some cases, the image on the reading surface may be determined to be the show-through image, but the show-through image can be subtracted by the output value according to the degree of the show-through. Therefore, even if a gradation image is formed on the reading surface of the document P with show-through, the gradation image can be read with high accuracy.

Further, since the scanner 14 is provided with the first and second reading sections 23 and 26 with the conveyance path of the original P being sandwiched therebetween, one side and the other side of the original are used as the reading side and the back side thereof. The image data (image signal) can be read at one time, and the document can be quickly processed without repeating the conveyance. Further, since the image signals read from both sides of the document P are only displaced in the sub-scanning direction due to the positional relationship,
The image data can be easily corrected with high accuracy.

In the present embodiment, an example in which images are read from both sides of the original and processed is described. However, when only one side of the original is read, the show-through correction units 35a, 35 are used.
It goes without saying that after b, only one may be used.
Further, although an example of the image reading apparatus including two sets of reading units has been described, even if the image is read from both sides of the original by circulating the original, the read image data is temporarily stored in the memory. It goes without saying that the configuration may be such that the show-through correction processing is performed.

[0033]

According to the first aspect of the present invention, the image data read from the reading surface is corrected to the image data of only the image on the reading surface based on the image data read from the back surface thereof. The image on the reading surface can be read without the need. Therefore, it is possible to read an image on the reading surface with high quality even for an original with show-through.

According to the second aspect of the present invention, the image data on the back side when the show-through is subtracted from the image data on the read side, so that the image on the read side can be read without the influence of the show-through. Therefore, the image data read from the reading surface can be easily corrected. According to the third aspect of the invention, since the image data is read at once from the reading surface and the back surface, both image data can be read in a clear positional relationship. Therefore, the image data read from the reading surface can be corrected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a facsimile apparatus equipped with an embodiment of an image reading apparatus according to the present invention, and is a block diagram showing a schematic overall configuration thereof.

FIG. 2 is a configuration diagram showing a reading mechanism of the reading means.

FIG. 3 is a block diagram showing a configuration for processing the read image data.

FIG. 4 is a block diagram showing a configuration for correcting the image data.

5A and 5B are diagrams showing a document to be read, in which FIG. 5A is a plan view of one surface thereof, and FIG. 5B is a plan view of the other surface thereof.

6A and 6B are diagrams illustrating the show-through of a document to be read, in which FIG. 6A is a plan view of one surface thereof, and FIG. 6B is a plan view of the other surface thereof.

7A and 7B are diagrams illustrating the read image data before processing, FIG. 7A is an output waveform of image data obtained by reading one surface of the image data, and FIG. 7B is an output waveform of image data obtained by reading the other surface thereof. .

8 is a diagram for explaining the processing of the image data of FIG. 7, (a) is an output waveform of the image data of one surface side,
(B) is an output waveform of the image data of the other surface.

FIG. 9 is a diagram illustrating a process following that of FIG. 8;
(A) is an output waveform of the image data of the one side, and (b) is an output waveform of the image data of the other side.

FIG. 10 is a diagram illustrating image data after the processing,
(A) is an output waveform of the image data of the one side, and (b) is an output waveform of the image data of the other side.

[Explanation of symbols] 11 System controller 12 Operation unit 13 Communication processing unit 14 Scanner (image reading device) 15 Image memory 16 Image reproducing unit 21, 24 Light source 22, 25 Image sensor 23 First reading unit (reading means) 26th 2 reading unit (reading means) 27, 28 reference white boards 35a, 35b show-through correction unit (correction means) 39 delay memory 41 linear conversion processing unit 42 mirroring processing unit 43 line delay memory 44 subtractor

Claims (3)

[Claims] 1. A reading means for reading an image from both sides of a document and outputting converted image data, and one image data of one side or the other side outputted from the reading means is corrected based on the other image data. An image reading apparatus comprising: a correction unit that converts image data of only an image formed on one surface of a document. 2. The correction means reduces the output of one image data and subtracts the output of the other image data in which the left and right of the original in the main scanning direction are reversed. Image reading device. 3. The reading means includes a first reading section for reading an image from one side of the original, a second reading section for reading an image from the other side of the original, and a reading section for reading the original or the first and second reading sections. Moving means for moving one relative to the other, and the first and second reading sections read images from both sides of the original by a single relative movement of the original by the moving means. The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus.