JP2000188668A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the quality of a read image from being deteriorated by making the optical characteristics of the respective original reading means of the front surface side and the rear surface side of an original different from each other, thereby eliminating failures such as transmitting light or rear copying by a light source on the facing side of the original, without complicated control such as alternately controlling respective turning on and turning off of the light source of the respective original reading means by the unit of a scanning line. SOLUTION: A front surface reading part 13 and a rear surface reading part 14 set to the optical characteristics of both of the reduced optical system sensors or/and the optical characteristics of an unmagnificated optical system sensor (contact image sensor) to be respectively different. As an optical characteristic value, mainly spectroscopic sensitivity characteristic of the light emitting wavelength distribution/image sensor (photoelectric conversion element) of the light source can be cited. Optical interference can be reduced breaking into discrete parts the composite characteristic of the image signal of the front/back of the original by differentiating the spectroscopic sensitivity of a reading optical system. In addition, light-emitting wavelength distribution is varied by selecting a light-emitting color in the case of using a light-emitting diode for the light source but selecting a fluorescent film when a fluorescent lamp is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a facsimile apparatus, a digital copier apparatus, and an image scanner having a function of simultaneously reading both the front and back surfaces of a document.

[0002]

2. Description of the Related Art Conventionally, in an image reading apparatus such as a facsimile apparatus, a digital copier apparatus, and an image scanner apparatus having a function of simultaneously reading both the front and back sides of a document, the light sources on both sides are always turned on. In the case of a thin original, there is a problem in that the quality of a read image is degraded due to light transmitted by the light source on the opposite side or show-through. Therefore, an image reading apparatus that alternately controls the turning on and off of the light sources on the front side and the back side in units of scanning lines (for example,
Japanese Patent Application Laid-Open No. 9-321947) has been proposed.

[0003]

However, in the above-described image reading apparatus in which the turning on and off of the light sources on the front side and the back side are alternately controlled for each scanning line, the light transmitted by the light source on the opposite side of the document is used. Troubles such as and show-through,
Deterioration of the quality of the read image can be prevented, but there is a problem that the cost of the apparatus increases because the control processing is complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and when reading images on both sides of a document simultaneously by respective document reading means provided on the front side and the back side of the document, respectively, This eliminates problems such as transmitted light and show-through caused by the light source on the opposite side of the document, without performing complicated control such as alternately controlling the turning on and off of the light source for each scanning line. The purpose is to be able to prevent.

[0005]

In order to achieve the above object, the present invention has means for arranging manuscript reading means on the front and back sides of a manuscript, respectively, and means for simultaneously reading images on both sides of the manuscript by each manuscript reading means. In the image reading apparatus provided with the above, the optical characteristics of each of the document reading means on the front side and the back side are different from each other.

In the above-described image reading apparatus, it is preferable that the emission wavelength distributions of the original illumination light sources of the original reading means on the front side and the rear side are different from each other.

Further, in the above-described image reading apparatus, it is preferable that the spectral sensitivity characteristics of the photoelectric conversion elements of the document reading means on the front side and the back side are different from each other.

Further, at least one of the document reading means on the front side and the back side may be constituted by a close contact type image sensor using an equal magnification optical system sensor.

According to the first aspect of the present invention, when the images on both sides of the original are simultaneously read by the original reading means provided on the front side and the rear side of the original, respectively, the original reading means on the front side and the back side are provided. The optical characteristics of the light source on the front side and the light source on the back side do not need to be controlled alternately for each scanning line. Thus, it is possible to prevent the image quality from being deteriorated by the irradiation light of the facing light source at the time of double-sided image reading at low cost.

In the image reading apparatus according to the second aspect of the present invention, the light emission wavelength distributions of the light sources of the document reading means on the front side and the back side are made different from each other, so that the influence on the facing sensor during double-sided reading is reduced. Thus, it is possible to prevent the image quality from being degraded by the irradiation light of the facing light source at the time of reading the two-sided image at low cost.

In the image reading apparatus according to the third aspect of the present invention, since the spectral sensitivities of the photoelectric conversion elements of the original reading means on the front side and the rear side are different from each other, the influence of the light source on the facing side during double-sided reading is reduced. Thus, it is possible to prevent the image quality from being degraded by the irradiation light of the facing light source at the time of reading the two-sided image at low cost.

In the image reading apparatus according to a fourth aspect of the present invention, at least one of the document reading means on the front side and the back side is constituted by a close contact type image sensor using an equal magnification optical system sensor. Compared with a general method of scanning a document image by a system sensor, it is easier to secure an optical path when reading both sides of a document at the same time, and the size of the device can be easily reduced.

[0013]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a basic configuration of a facsimile apparatus which is an embodiment of the image reading apparatus of the present invention.

This facsimile apparatus has a CPU, an RO,
A system control unit 1 that is realized by a microcomputer including an M and a RAM and performs control processing of each unit of the apparatus and facsimile transmission control procedure processing, and executes a control processing program and a processing program executed by the system control unit 1. And a system memory 2 which constitutes a work area of the system control unit 1.

A parameter memory 3 for storing various information unique to the G3 facsimile apparatus, a scanner unit 4 for performing various image processing by resolving and scanning an original image at a predetermined resolution, A plotter unit 5 for recording processed data or image information received from another facsimile device at a predetermined resolution, various keys for operating the facsimile device, status display on the facsimile device, and messages for various operations are displayed. And an operation panel 6 including various displays.

Furthermore, the image signal is encoded and compressed,
An encoding / decoding unit 7 for decoding the encoded / compressed image information into an original image signal, and an image storage device 8 for storing the image information in a state of being encoded / compressed by the encoding / decoding unit 7 It has.

Furthermore, a low-speed modem function (V.21 modem) for realizing a G3 facsimile modem function for exchanging transmission procedure signals and a high-speed modem function for mainly exchanging image information are provided. Function (V.
34 modem. 29 modem, V.I. 27ter modem etc.) and a facsimile machine with ISDN
A network controller (Network Controller) for connecting to a public line such as
ol Unit: NCU).

The system control unit 1, system memory 2, parameter memory 3, scanner unit 4, plotter unit 5, operation panel 6, encoding / decoding unit 7, image storage unit 8, modem 9, and network control unit (NCU) ) 10 are connected to a system bus 11, and data exchange between these units is mainly performed via the system bus 11. Data exchange between the network controller 10 and the modem 9 is performed directly.

FIG. 2 is a block diagram showing an example of the basic configuration of the scanner section 4. As shown in FIG. The scanner unit 4 reads the front side image information of the document 12 and outputs the same as an analog electric signal, and the back side reading unit 14 reads the back side image information of the document 12 and outputs the same as an analog electric signal.
And a multiplexer 15 for mixing read image signals read by the front surface reading unit 13 and the back surface reading unit 14 at a predetermined timing.

An operational amplifier 16 for amplifying the front and back analog image signals mixed by the multiplexer 15 at a predetermined amplification factor and reducing the impedance to output the amplified analog image signals;
An A / D converter 17 for quantizing the analog image signal output from the operational amplifier 16 based on a predetermined reference level;
A shading correction unit 18 is provided to correct shading distortion caused by superimposing an image signal mainly due to an optical system.

Further, a digital image processing section 19 for performing various image processing on the digital image signal from which the distortion has been removed by the shading correction section 18 and a digital image processing section which the shading correction section 18 refers to when performing shading correction processing. Reference numeral 19 includes a line buffer 20 for storing various data to be referred to in digital image processing.

FIG. 3 is a diagram showing an example of an internal configuration of the front surface reading unit 13 and the back surface reading unit 14 using a reduction optical system sensor (CCD).

The front side reading unit 13 guides the document 12,
Target glass 23 for preventing dust and the like from entering the optical system
And a light source 24 for illuminating the vicinity of the reading unit on the surface of the document 12
A mirror section 25 for guiding the reflected light from the document 12 by a predetermined optical path length, a lens 26 for forming an image of the light guide reflected light signal at a predetermined reduction ratio by the mirror section 25, and an image formed by the lens 26. A surface image sensor 27, which is a photoelectric conversion element for converting the optical signal into an electric signal, and a sample and hold circuit 28 for detecting and holding an analog output level from the surface image sensor 27 at a predetermined timing.

On the other hand, the back side reading unit 14 guides the original 12 to prevent dust or the like from entering the optical system, a light source 34 for illuminating the vicinity of the reading unit on the back side of the original 12, and the original 12 A mirror section 35 for guiding the reflected light from the lens by a predetermined optical path length, a lens 36 for forming an image of the light guide reflected light signal by the mirror section 35 at a predetermined contraction rate, and a light signal formed by the lens 36 It comprises a backside image sensor 37 which is a photoelectric conversion element for converting into an electric signal, and a sample and hold circuit 38 which detects and holds an analog output level from the backside image sensor 37 at a predetermined timing.

When the reading of the document 12 is instructed from the operation panel 6, the system control unit 1
4 is turned on to start conveying the document 12. When the original 12 reaches a predetermined reading position, the reading of the front and back sides of the image is started, and the image information of the front side photoelectrically converted by the front side image sensor 27 is sampled and waveform-shaped by the sample and hold circuit 28 and output to the multiplexer 15. Is done.

On the other hand, the image information on the back surface photoelectrically converted by the back image sensor 37 is stored in a sample-and-hold circuit 38.
, And is output to the multiplexer 15.

The multiplexer 15 combines the two-sided image information signals from the sample and hold circuits 28 and 38 into one system and outputs the combined signal to the operational amplifier 16.
Performs a predetermined amplification and impedance conversion to obtain A /
Output to the D converter 17. The A / D converter 17 quantizes the input image signal into a predetermined number of bits on the basis of, for example, the maximum value of the input image signal, and outputs the result to the shading correction unit 18.

The shading correction unit 18 performs A / A based on the correction data stored in the line buffer 20.
The shading distortion caused by the light source / optical system of the digital data quantized by the D converter 17 is corrected,
The digital image processing unit 19 performs various image processing on the image signal after the shading correction.

The signal switching by the multiplexer 15 may be performed in either pixel units or line units according to the reading method of the front and back surfaces.

FIG. 4 is a diagram showing an example of the internal configuration of the front surface reading unit 13 and the back surface reading unit 14 using a 1: 1 optical system sensor (contact image sensor).

The front side reading unit 13 guides the document 12,
Target glass 43 for preventing dust and the like from entering the optical system
And a light source 44 for illuminating the vicinity of the reading unit on the surface of the document 12
And an SLA (SELFOC LEN) that forms an image of the reflected light from the original 12 on the surface image sensor 47 at the same magnification.
S ARRAY), a surface image sensor 47 which is a photoelectric conversion element for converting an optical signal formed by the image forming lens 49 into an electric signal, and an analog signal from the surface image sensor 47. A sample and hold circuit 4 for detecting and holding an output level at a predetermined timing
8

On the other hand, the back surface reading unit 14 guides the document 12 to prevent dust and the like from entering the optical system, a light source 54 for illuminating the vicinity of the reading unit on the back surface of the document 12, a document 12 (SELFOCL) that forms an image of the reflected light from
ENS ARRAY) and a back-side image sensor 57 that is a photoelectric conversion element that converts an optical signal formed by the same-size imaging lens 59 into an electric signal.
And a sample and hold circuit 58 for detecting and holding the analog output level from the backside image sensor 57 at a predetermined timing.

When the reading of the document 12 is instructed from the operation panel 6, the system controller 1 causes the light sources 44 and 5 to operate.
4 is turned on to start conveying the document 12. When the document 12 reaches a predetermined reading position, reading of the front and back surfaces of the image is started, and the illumination light from the light source 44 is irregularly reflected by the document 12 and is incident on the same-magnification imaging lens 49.
7 converts the imaging light into an electric signal, and converts the surface image sensor 4
The image information on the surface photoelectrically converted by 7 is sampled and shaped by a sample and hold circuit 48 and output to the multiplexer 15.

On the other hand, the illumination light from the light source 54 is irregularly reflected by the original 12 and is incident on the same-size imaging lens 59. The backside image sensor 57 converts the imaging light into an electric signal. The sampled image information of the surface is sampled and shaped by the sample and hold circuit 58,
Output to the multiplexer 15.

The multiplexer 15 combines the two sets of image information signals from the sample and hold circuits 48 and 58 into one system and outputs the combined signal to the operational amplifier 16.
Performs a predetermined amplification and impedance conversion to obtain A /
Output to the D converter 17. The A / D converter 17 quantizes the input image signal into a predetermined number of bits on the basis of, for example, the maximum value of the input image signal, and outputs the result to the shading correction unit 18.

The shading correction section 18 performs A / A based on the correction data stored in the line buffer 20.
The shading distortion caused by the light source / optical system of the digital data quantized by the D converter 17 is corrected,
The digital image processing unit 19 performs various image processing on the image signal after the shading correction.

In this way, unlike the case where the reduction optical system sensor shown in FIG. 3 is used, since the image of the document 12 is photoelectrically converted at the same magnification, a long optical path length is secured like the reduction optical system. There is no need to perform optical adjustment after the product is assembled, and in recent years, the performance / cost ratio has been improved, and personal devices have been frequently used.

Further, since the irradiation lights from the light sources 44 and 54 do not have perfect directivity, they illuminate a certain area near the reading position of the original 12, and the light that illuminates the reading position among them. Are diffusely reflected on the document surface and are guided to the front image sensor 47 and the back image sensor 57, respectively.

Further, a part of the illumination light is transmitted to the opposite side according to the thickness (transmittance) of the document 12, so that a part of the transmitted light is strayed to the original optical system as a flare. When the level of the flare light is sufficiently smaller than the original level of the reflected light, the quality of the read image is hardly affected. Will affect you.

Therefore, in the facsimile apparatus of this embodiment, the face-to-face interference of the irradiation light when reading both sides of the document is reduced with a relatively simple configuration, thereby preventing the quality of the read image from deteriorating.

Next, the function of the facsimile apparatus according to claim 1 of the present invention will be described. If the optical characteristics of the front-side reading unit 13 and the back-side reading unit 14 of the facsimile apparatus are made different from each other, it is possible to make the irradiation light from the light source less likely to have an effect on the facing side. A double-sided image reading environment that is hardly affected by irradiation light can be obtained.

Therefore, in the case of the front surface reading unit 13 and the back surface reading unit 14 shown in FIG. 3, the optical characteristics of both reduction optical system sensors (CCD) are set to be different from each other. Also,
In the case of the front side reading unit 13 and the back side reading unit 14 shown in FIG.
The optical characteristics of the unit-magnification optical system sensor (contact image sensor) are set to be different from each other.

As the above-mentioned optical characteristic values, there are mainly the emission wavelength distribution of the light source and the spectral sensitivity characteristics of the image sensor (photoelectric conversion element). Since the spectral sensitivity of the reading optical system is substantially equal to the combined function of the emission length distribution of the light source and the spectral sensitivity characteristic of the photoelectric conversion element, the optical interference can be reduced by discretizing the combined characteristic of the image signals on the front and back of the document. Can be.

As described above, since the optical characteristics of the respective document reading means provided on the front side and the back side of the document are different from each other, the influence of the facing light source at the time of double-side reading can be reduced.

Next, the function of the facsimile apparatus according to claim 2 of the present invention will be described. In this facsimile apparatus, the emission wavelength distribution is made different as the optical characteristics of the front surface reading unit 13 and the back surface reading unit 14. When an LED (light emitting diode) is used as a light source, the emission color can be made variable by selecting the emission color, and when using a fluorescent tube, the emission film can be made variable by selecting a fluorescent film.

Therefore, in the case of the front surface reading unit 13 and the back surface reading unit 14 shown in FIG. 3, the light emission wavelength distributions of the light sources 24 and 34 are set to be different from each other. In addition, in the case of the front surface reading unit 13 and the back surface reading unit 14 shown in FIG. 4, the emission wavelength distributions of the light sources 44 and 54 are set to be different from each other.

Therefore, it is possible to reduce the optical interference with each of the facing image sensors, and to obtain a good read image quality with less show-through.

As described above, since the emission wavelength distributions of the light sources for illuminating the originals of the respective original reading means provided on the front side and the rear side of the original are different from each other, the influence on the facing sensor during double-sided reading is reduced. can do.

Next, the function of the facsimile apparatus according to claim 3 of the present invention will be described. In this facsimile apparatus, the spectral sensitivity characteristics of the image sensor differ as the optical characteristics of the front-side reading unit 13 and the back-side reading unit 14.

In this setting, the spectral sensitivity may be controlled in the semiconductor process, or a specific color filter may be added to the upper surface of the sensor. Therefore, it is possible to reduce the amount of optical interference received from the facing image sensor, and to realize good double-sided image reading with little show-through.

The emission wavelength distribution of the light source and the spectral sensitivity characteristic of the image sensor may both be different, or one of them may be different depending on the situation of use.

As described above, the spectral sensitivity characteristics of the photoelectric conversion elements of the respective document reading means provided on the front side and the back side of the document are different from each other. Can be.

Next, the function of the facsimile apparatus according to claim 4 of the present invention will be described. In this facsimile apparatus, at least one of the front-side reading unit 13 and the back-side reading unit 14 is a contact image sensor, so that the degree of freedom in the mechanical design related to the configuration of the back-side reading unit can be increased.

As described above, since at least one of the document reading means provided on the front side and the back side of the document is constituted by the close contact type image sensor, the degree of freedom in mechanism design can be increased.

[0055]

As described above, according to the image reading apparatus of the present invention, when the images on both sides of the original are simultaneously read by the original reading means provided on the front side and the back side of the original, respectively. Eliminates problems such as transmitted light and show-through caused by the light source on the opposite side of the original, without performing complicated control such as turning on and off the light source of the original reading means alternately in units of scanning lines. Quality degradation can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a facsimile apparatus as an embodiment of an image reading apparatus according to the present invention.

FIG. 2 is a block diagram illustrating a basic configuration example of a scanner unit illustrated in FIG. 1;

FIG. 3 is a diagram showing an example of an internal configuration of a front-side reading unit and a back-side reading unit shown in FIG. 2 using a reduction optical system sensor (CCD).

FIG. 4 is a diagram illustrating an example of an internal configuration of a front-side reading unit and a back-side reading unit illustrated in FIG. 2 using a 1: 1 optical system sensor (contact image sensor).

[Explanation of symbols]

 1: System control unit 2: System memory 3: Parameter memory 4: Scanner unit 5: Plotter unit 6: Operation panel 7: Encoding / decoding unit 8: Image storage unit 9: Modem 10: Network control unit (NCU) 11: System bus 12: Document 13: Front side reading unit 14: Back side reading unit 15: Multiplexer 16: Operational amplifier 17: A / D converter 18: Shading correction unit 19: Digital image processing unit 20: Line buffers 23, 33, 43, 53: target glass 24, 34, 44, 54: light source 25, 35: mirror unit 26, 36: lens 27, 47: front image sensor 28, 38, 48, 58: sample and hold circuit 37, 57: back image sensor 49 , 59: 1 × imaging lens

Claims (4)

[Claims] 1. An image reading apparatus comprising: a document reading unit disposed on a front side and a back side of a document; and a unit for simultaneously reading images on both sides of the document by each document reading unit. An image reading apparatus wherein the optical characteristics of each document reading means are different from each other. 2. The image reading apparatus according to claim 1, wherein a light emission wavelength distribution of a document illumination light source of each of the document reading means on the front side and the back side is different from each other. . 3. The image reading device according to claim 1, wherein the spectral sensitivity characteristics of the photoelectric conversion elements of the document reading means on the front side and the back side are different from each other. apparatus. 4. The apparatus according to claim 1, wherein at least one of the original reading means on the front side and the back side is constituted by a close contact type image sensor using an equal-magnification optical system sensor. An image reading device according to the item.