JPH05191645A - Picture reader and facsimile equipment - Google Patents

Abstract

PURPOSE:To provide the picture reader in which the accuracy deterioration due to a stain of a roller in the density correction system using a white level density of a face of an original carrier roller as a reference level is avoided and an output change in a white density level caused by a temperature change or optical deterioration in an original reading photoelectric conversion element is corrected with high accuracy. CONSTITUTION:A shading correction photoelectric conversion element 3 and a white color member 4 covering the element 3 fixedly are provided to at least one outside of original reading photoelectric conversion elements 2, an output of the photoelectric conversion element 3 and a stored reference value are compared to obtain a temperature change or a secular change in the output thereby correcting the picture information from the photoelectric conversion elements 2 based on the change. Since it is not required to use an original carrier roller face for a reference of a white level density, an output change in the white density level is corrected with high accuracy without being affected of stain and it is not required to employ a special roller such as a Teflon coated roller and then the original carrying capability is ensured.

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 having a photoelectric conversion element, and relates to a facsimile apparatus, an image scanner apparatus, etc. equipped with this image reading apparatus.

[0002]

2. Description of the Related Art An image reading apparatus which irradiates a document surface to be read with a light source and converts the reflected light into an electric signal by a photoelectric conversion element is widely used in facsimiles and image scanners. In this type of image reading apparatus, the output waveform of the photoelectric conversion element is not flat even when reading a document having a uniform reflection density. For example, there are fluctuations such that the output of the pixel at the center of the left and right is high and the output of the pixel at the end is low. This fluctuation phenomenon is called a shading phenomenon.

There are mainly two possible causes of the shading phenomenon. (1) Non-uniformity of sensitivity of photoelectric conversion element and its change with time A photoelectric conversion element having a photoelectric conversion film such as amorphous silicon has non-uniform sensitivity and temperature characteristics due to variations in manufacturing conditions in the manufacturing process. Often becomes. In addition, if it is exposed to the light from the light source for a long time, the sensitivity deteriorates. The degree of this deterioration is not uniform in all pixels and increases the nonuniformity of the sensitivity. (2) Illuminance unevenness of the light source lamp and its change with time As the light source lamp for illuminating the original, for example, an LED array is used. Since the illuminance of light irradiating each pixel of the photoelectric conversion element is greatly different between the position directly above the LED element and the position above the LED element, and the illuminance of the LED element itself is not uniform, the output of the photoelectric conversion element is Also, a shading phenomenon occurs accordingly. Further, the LED element has a decrease in emission luminance with time, but the degree of the decrease is not uniform, which further increases the shading phenomenon.

In order to correct this shading, various methods have been conventionally proposed. For example, there is a method of correcting the shading by guiding the reflected light on the ground surface of the document transport roller on the photoelectric conversion element to the photoelectric conversion element for each original document, and A / D converting the output signal thereof. In this method, it is possible to accurately correct variations in the sensitivity of the photoelectric conversion film, variations in the output value due to temperature change or deterioration of the photoelectric conversion film, variations in the light amount of the light source LED elements, variations in the output value due to deterioration, etc. It is said to be a good method for improvement.

[0005]

However, in this method, if there is a change in the reflection density due to dirt or the like on the roller surface facing the reference photoelectric conversion element, it causes deterioration of the correction accuracy. It becomes noise. That is, when shading correction is performed using the document transport roller as a reference surface, if the surface of the document transport roller becomes soiled with foreign matter and differs from the original reference white density, the accuracy of shading correction will be significantly reduced. Become. Therefore, the photoelectric conversion element roller needs to be a roller in which a surface of rubber, which is a material of the conveying roller, is coated with a material such as Teflon which is not easily soiled. However, such a dirt-resistant roller generally has a low coefficient of friction between the original and the paper, and it is difficult to accurately convey the original to be transmitted. Therefore, in this method, in addition to the original-conveying roller on the photoelectric conversion element, another original-conveying auxiliary roller using a material having a high friction coefficient with the paper of the original is provided,
It is necessary to devise a method to stably convey the original. In this case, the number of parts of the document reading section increases and the mechanism becomes complicated, so that there is a problem that the entire apparatus becomes large and the cost increases.

In order to solve these problems, Japanese Patent Laid-Open Publication No.
In JP-A-8-27466 or JP-A-58-223963, the conversion output of a specific pixel of a photoelectric conversion element is sampled to obtain a shading correction coefficient of the sampling pixel, and at the time of shading correction, the correction coefficient of the non-sampling pixel is sequentially calculated by an interpolation method. We have proposed a method for obtaining and correcting shading. In this method, at least the surface of the document-conveying roller surface on the photoelectric conversion element, which is located at the position corresponding to the non-sampling pixel, is not used as a reference surface, and therefore even if the roller is dirty, No problem. Therefore, basically, it is possible to employ a roller which has a high coefficient of friction with paper and has a sufficient paper conveying force although it is easily soiled. In other words, there is no need to specially prepare a conveyance auxiliary roller for ensuring stable conveyance, which is advantageous for downsizing of the apparatus and cost reduction.

However, even in this system, the sampling pixel performs photoelectric conversion using the roller surface immediately above the pixel as a reference surface, so that the roller immediately above the sampling pixel is
At least it needs to be clean. However, it is difficult to predict which part of the roller will be soiled, and keeping the roller surface, which is used as the reference surface, in a clean state will impose a heavy burden on the user.

Further, Japanese Patent Publication No. 3-24827 discloses a copying machine in which a document table is moved, and the reflected light from a reference white density reflecting surface fixed to the lower surface of the document conveying frame is taken in before reading the document. A method of correcting the density of a document based on the output of the photoelectric conversion element has been proposed. Since no particular consideration is given to the material of the white density reflecting surface, even in this method, the reference white density reflecting surface may become dirty as the usage time increases. In particular, in the case of a system in which only a document is sent by a transport roller and read by a contact type photoelectric conversion element, dirt is expected to be attached, and it is difficult to apply as it is.

An object of the present invention is to use, as a document carrying roller on a photoelectric conversion element, a roller which has a high friction coefficient with a paper and a sufficient paper carrying force, as a roller for carrying an original on a photoelectric conversion element.
An object of the present invention is to provide an image reading apparatus and an application product thereof, such as a facsimile apparatus, which can always ensure high shading correction accuracy.

[0010]

In order to achieve the above object, the present invention provides an original reading photoelectric conversion element for converting image information of an original to be read into an electric signal, and an original from the original reading photoelectric conversion element. An image reading apparatus having an image processing circuit for A / D converting an analog output voltage corresponding to a density and converting the analog output voltage into a digital signal indicating a density gradation value, and the photoelectric conversion element having the same structure as a photoelectric conversion element for reading an original. A photoelectric conversion element for shading correction which is arranged in the vicinity of the element, a means which faces the photoelectric conversion element for shading correction and which always provides a reflection surface having a constant reference white density, and reflection from a reflection surface having a reference white density. An image reading apparatus is provided, which includes a unit that corrects the density gradation value based on the output of a shading correction photoelectric conversion element that photoelectrically converts light. It is intended.

The shading correction photoelectric conversion element is arranged on one side or both sides in the longitudinal direction of the original reading photoelectric conversion element array.

When the shading correction photoelectric conversion element is arranged in the vicinity of the original reading photoelectric conversion element array or on one side in the longitudinal direction, the means for correcting the density gradation value is such that the current output of the shading correction photoelectric conversion element is the initial value. Value α
When doubled, the density gradation value is corrected at a constant rate according to the magnification α.

When the shading correction photoelectric conversion elements are arranged on both sides in the longitudinal direction of the original reading photoelectric conversion element row, the means for correcting the density gradation value is an average of the current outputs of the shading correction photoelectric conversion elements. When is equal to α times the initial value, the density gradation value is corrected at a constant rate according to the magnification α.

Instead of the method, when the current outputs of the shading correction photoelectric conversion elements on both sides are α times and β times the initial values, the density gradation value is α + (β−α) depending on the pixel position. n / (N-1) However, you may make it correct | amend by multiplying n: the pixel number of a photoelectric conversion element, N: the total number of pixels of the original-reading photoelectric conversion element.

In any of the above cases, the means for providing the reflection surface having the reference white density includes a white member fixed over the shading correction photoelectric conversion element and a sliding member pressed so as to cover the shading correction photoelectric conversion element. It can be selected from a white film on the surface.

In order to achieve the above-mentioned object, the present invention also has a light-shielding film on the back surface that blocks direct incident light from the document illumination light source, and converts the image information from the document to be read into an electrical signal. Photoelectric conversion element, an image processing circuit for A / D converting the analog output voltage corresponding to the original density from the original reading photoelectric conversion element to a digital signal indicating the density gradation value, and the original reading photoelectric conversion A photoelectric conversion element for shading correction which has the same structure as the element and has a light-shielding film on the surface which is arranged in the vicinity of the photoelectric conversion element and which blocks the incident light from the document conveying roller or the like, and captures only the direct incident light from the document illumination light source. Image reading provided with an element and means for correcting the density gradation value based on the output of the photoelectric conversion element for shading correction, which is obtained by photoelectrically converting the direct incident light from the document illumination light source. It is intended to propose a taking apparatus.

Also in this case, the shading correction photoelectric conversion elements are arranged on one side or both sides in the longitudinal direction of the original reading photoelectric conversion element array.

When the photoelectric conversion element for shading correction is arranged in the vicinity of the photoelectric conversion element array for reading the original or on one side in the longitudinal direction, the means for correcting the density gradation value is such that the current output of the photoelectric conversion element for shading correction is initially set. Value α
When doubled, the density gradation value is corrected at a constant rate according to the magnification α.

When the shading correction photoelectric conversion elements are arranged on both sides of the original reading photoelectric conversion element array in the longitudinal direction, the means for correcting the density gradation value is an average of the current outputs of the shading correction photoelectric conversion elements. When is equal to α times the initial value, the density gradation value is corrected at a constant rate according to the magnification α.

Instead of that method, when the current outputs of the shading correction photoelectric conversion elements on both sides are α times and β times the initial values, the density gradation value is α + (β-α) depending on the pixel position. n / (N-1) However, you may make it correct | amend by multiplying n: the pixel number of a photoelectric conversion element, N: the total number of pixels of the original-reading photoelectric conversion element.

Further, in order to achieve the above object, the present invention further includes an original reading photoelectric conversion element for converting image information of an original to be read sent by an original feeding roller shorter than the reading width into an electric signal, and the original. An image reading apparatus having an image processing circuit for A / D converting an analog output voltage corresponding to a document density from a reading photoelectric conversion element and converting the analog output voltage into a digital signal indicating a density gradation value,
Immediately before reading the original, the smooth white film facing the photoelectric conversion element for reading the original where there is no original conveyance roller and providing a reflective surface with a constant reference white density, and the reflected light from the reflective surface with the reference white density An image reading apparatus is provided, which further comprises means for correcting the density gradation value of an original read subsequently based on the output of the photoelectric conversion element for original reading which is photoelectrically converted.

When the current output of the shading correction photoelectric conversion element becomes α times the initial value, the means for correcting the density gradation value corrects the density gradation value in proportion to the magnification α.

By combining any one of the above-mentioned image reading apparatus and an image recording apparatus for converting the transmitted electric signal into image information, a facsimile apparatus having the characteristic structure of the present invention can be obtained. Further, an image scanner device including any one of the above image reading devices as an image reading means can be realized.

[0024]

As described above, the output voltage of the photoelectric conversion element of the image reading apparatus included in the facsimile apparatus or the image scanner apparatus has the same density due to the influence of temperature change and photodegradation due to long-term use. It also changes when photoelectric conversion is performed on the like.

FIG. 8 is a diagram showing an example of the temperature dependence characteristic of the output voltage when photoelectric conversion is performed on the white density that is the reference for the photoelectric conversion element, and FIG. 9 is a graph showing the white density that is the reference for the photoelectric conversion element. It is a figure which shows an example of the time-dependent change characteristic of the output voltage at the time of photoelectric conversion. The horizontal axis of FIGS. 8 and 9 shows the position of each pixel of the photoelectric conversion elements of 1728 pixels which have a resolution of 8 lines / mm and are arranged in a line for reading an A4 original, for example, and the vertical axis is the reference. Shows the output voltage when the white density is photoelectrically converted.

In a facsimile device or an image scanner device, in order to transmit or process a read image, the analog output voltage corresponding to the original density photoelectrically converted by the photoelectric conversion element is further A / D converted and digitally converted. It is necessary to set the density gradation value. Therefore, the difference between the output voltage when the white density is photoelectrically converted and the output voltage when the black density is photoelectrically converted is divided by a predetermined number of gradations, and the output voltage when the actual original is photoelectrically converted is Determine if it is at a gradation level.

However, if the output voltage when the standard white density is photoelectrically converted or the output voltage when the black density is photoelectrically converted fluctuates due to temperature or light deterioration, the actual original is photoelectrically converted. The output voltage deviates from the gradation level that should be originally supported, which causes deterioration of image quality.

In order to avoid this deterioration of image quality, conventionally,
Before scanning the original, the surface of the white original feeding roller is photoelectrically converted, and the output voltage when the white density is photoelectrically converted is measured each time, and the original is read while correcting the gradation level based on the measured value. The output voltage is A / D converted. In this correction method, originally, it is more accurate to measure and correct both the output on the black density side and the output on the white density side, but the output on the black density side has a low voltage and temperature fluctuation. Since it is less affected by light deterioration and light deterioration, a method of measuring and correcting only the output on the white density side is often adopted.

FIG. 10 shows a white surface-treated transfer roller 12 in which a document transfer roller serving as a reference for obtaining a white density output is coated with Teflon so that foreign matter such as paper powder and pencil powder of a transmission document does not easily hit the roller. It is a perspective view which shows roughly the whole structure of an example of the conventional facsimile apparatus using the auxiliary roller 13.

Since the surface of the white surface-treated conveying roller 12 is used as a reference for the white density, if the roller 12 gets dirty, the density of that portion changes, the output voltage changes, and the tone shift occurs, resulting in image quality deterioration. The Teflon coating prevents dirt on the roller surface.

However, if the surface of the roller 12 is subjected to such stain prevention processing, the coefficient of friction between the roller 12 and the paper of the original 6 is lowered, and the original 6 cannot be conveyed accurately.

Therefore, a document carrying auxiliary roller 13 is provided to stably carry the document 6. Such a facsimile device or an image scanner device is satisfactory in image quality, but the conveyance roller 12 whose surface is white treated.
In addition to the above, since the auxiliary roller 13 for document transportation is required,
There is a drawback that the entire device becomes large and the cost increases.

FIG. 11 is a diagram for explaining an example of a shading correction method using an interpolation method as another conventional correction method. For example, in an image reading apparatus having a maximum A4 size, among the photoelectric conversion elements having 1728 pixels, only a specific pixel is used as a sampling pixel to photoelectrically convert the white density on the roller surface before reading an original, and the output of other pixels is Interpolate using the output voltage of those sampling pixels,
It shows a method of correcting the output of the photoelectric conversion element at low temperature.

The symbol "x" shows the output voltage with respect to the white density of the sampling pixel at a low temperature. For example, the first sampling pixel has outputs A ₁₀ to A ₁₁ at room temperature.
, And the second sampling pixel changes from A ₂₀ to A ₂₁ . Next, the rate of change of output β ₁ = A ₁₁ / A ₁₀ , β ₂
= A ₂₁ / A ₂₀ , ... For pixels between the first sampling pixel and the second sampling pixel, β
Assuming that the output voltage changes at the rate of change obtained by linearly interpolating ₁ and β ₂ , the output at low temperature indicated by the dotted line is calculated.

However, the output voltage at room temperature must be stored in the memory of the facsimile device or the image scanner device. Further, here, the characteristic that the output of the central pixel is larger than the output of the pixels at the left and right end portions is shown as it is, but in reality, the characteristic is corrected by a sensitivity correction curve that is the reverse of this characteristic, and a flat characteristic in the horizontal direction is obtained. The means for realizing the above are incorporated at the time of manufacturing. The present invention relates to a method of correcting a change in output voltage caused by a temperature change or photodegradation depending on a use condition even if a flat characteristic at room temperature is realized during manufacturing.

According to the correction method shown in FIG. 11, it is possible to correct the output change caused by the temperature change or the light deterioration with respect to the reference white density. In this case, since the entire surface of the carrying roller does not become a white reference surface, a normal roller having a high carrying power can be used and the auxiliary roller is unnecessary. However, when the roller surface facing the sampling pixel is soiled, there is a drawback that the correction accuracy is significantly reduced.

Therefore, in the present invention, the method shown in FIG. 12 is used to correct the temperature change during photoelectric conversion and the output change due to photodegradation. For example, since the shading correction photoelectric conversion elements arranged at both ends of the original reading photoelectric conversion element behave exactly the same as the original reading photoelectric conversion element, the shading correction photoelectric conversion element has a constant white density. The output value when the document reading photoelectric conversion element photoelectrically converts the same white density can be predicted from the output value when photoelectric conversion is performed. If the shading is corrected using this predicted value, high-precision shading correction can be realized without using auxiliary conveying rollers or the like, which is advantageous in improving the image quality of a facsimile device or image scanner device, downsizing the device, and reducing the cost. Is.

The correction is performed as follows. First, the low-temperature output voltage Al _{1 of the} photoelectric conversion element at the position adjacent to the left end of the original reading photoelectric conversion element and the low-temperature output voltage Ar _{1 of the} photoelectric conversion element at the position of the right end adjacent to the original are read. taking measurement. Since the surface of these photoelectric conversion elements is fixedly covered with a white member, a voltage corresponding to the white density is always output. Next, the ratio of the output voltage of the shading correction photoelectric conversion element at the time of reading the original is calculated with respect to the output voltage corresponding to the white density at room temperature stored in the memory of the facsimile apparatus, that is, the initial value in the memory. When the ratio is α times at one end and β times at the other end, the density gradation value is α + (β−α) n / (N−1) depending on the pixel position, where n: photoelectric conversion Element pixel number N: Shading correction is performed by multiplying by the total number of pixels of the original reading photoelectric conversion element. Here, it is assumed that the characteristics change linearly between the left and right ends.

Also in the present invention, the white member is photoelectrically converted by the photoelectric conversion element for shading correction and the photoelectric conversion element for reading the original at the time of manufacturing, and the initial value at that time is stored in a non-volatile memory such as an EPROM. Then, a flat characteristic is realized in the left-right direction.

When the correction method of the present invention is used, it is not necessary to use the document conveying roller surface itself as a reference for the white density, and therefore it is possible to completely avoid the deterioration of the correction accuracy due to roller contamination. Further, since it is not necessary to use a special roller such as that coated with Teflon, the conveyance of the original is stable, and the auxiliary roller is completely unnecessary. Therefore, it is possible to realize an image reading apparatus that is compact and inexpensive and can obtain high image quality.

In the present invention, the white member is photoelectrically converted by the photoelectric conversion element for shading correction and the photoelectric conversion element for reading the original during manufacturing, and the initial value at that time is stored in a non-volatile memory such as an EPROM. Then, a flat characteristic is realized in the left-right direction.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image reading apparatus according to the present invention will be described below with reference to FIGS. Figure 1
1 is a perspective view schematically showing the overall structure of a facsimile machine including an image reading device according to the present invention. The image information of the transmission document 6 conveyed by the document conveying roller 5 is converted into an electric signal by the image reading device 1, and the image processing circuit 1
After 0, it is transmitted to the communication partner. On the other hand, the electric signal received from the communication partner passes through the image processing circuit 10,
It is sent to the image recording device 7 and recorded on the recording paper 8. The recording paper 8 is conveyed by a recording paper conveyance roller 9. The image reading apparatus 1 includes a photoelectric conversion element 2 that converts the image information of the original 6 into an electric signal, and a photoelectric conversion element 3 that is covered with the white member 4 and always photoelectrically converts the white density of the white member 4. ..

FIG. 2 shows the positional relationship among the original reading photoelectric conversion element 2, the shading correction photoelectric conversion element 3, the white member 4, and the transmission original 6 of the image reading apparatus 1 included in the facsimile apparatus of FIG. FIG. The photoelectric conversion element 2 has, for example, a resolution of 8 pixels / mm and is A4 size.
Is formed by arranging photoelectric conversion elements of 1728 pixels for reading the original document and 2048 pixels for reading the B4 original document in a line, and converts the image information of the transmission original document 6 into an electric signal. In addition, the photoelectric conversion element 3 covered with the white member 4
Are arranged in the same column as the photoelectric conversion elements 2 and on at least one side of the photoelectric conversion elements 2. The pixel of the photoelectric conversion element 3 may be one pixel or a plurality of pixels. The photoelectric conversion element 2 and the photoelectric conversion element 3 have exactly the same structure. In order to make the characteristics of the films of these photoelectric conversion elements as close as possible, the positions of the both are arranged as close as possible. However, in the present embodiment, both are arranged in a line, but if they are close to each other, it is not necessary to arrange them in the same line. The white member 4 may be anything as long as it has a constant white density, for example, only white paint may be applied on the photoelectric conversion element 3.

The image reading apparatus 1 shown in FIG. 2 is composed of an original reading photoelectric conversion element 2 and a photoelectric conversion element 3 covered with a white member 4. A change in temperature due to photoelectric conversion of white density and a change in output due to light deterioration are corrected by the correction method shown in FIG. 12, as described above.

First, the output voltage Al _{1 of the} photoelectric conversion element 3 at the position adjacent to the left end of the original reading photoelectric conversion element 2 at low temperature and the output voltage Al _{1 of the} photoelectric conversion element 3 at the position adjacent to the right end at low temperature. Measure the output voltage Ar ₁ . The surface of each of these photoelectric conversion elements 3 is covered with a constant white member 4, so that the photoelectric conversion element 3 always outputs a voltage corresponding to the white density. next,
The change rates α = Al ₁ / Al ₀ and β = Ar ₁ / Ar ₀ from the output voltages Al ₀ and Ar ₀ corresponding to the white density stored in the memory of the facsimile machine at room temperature are calculated. Finally, assuming that the output with respect to the white density of the original reading light conversion elements 2 changes at a change rate obtained by linearly interpolating α and β, the low temperature of all the original reading photoelectric conversion elements 2 shown by the dotted line in FIG. Calculate the output voltage at. That is, when the current outputs of the shading correction photoelectric conversion elements 3 on both sides are α times and β times the initial values, respectively, the density gradation value is α + (β−α) n / (N− depending on the pixel position. 1) However, n is the pixel number of the photoelectric conversion element, N is the total number of pixels of the photoelectric conversion element for reading the original, and the correction is performed.

If the correction method of this embodiment is used, it is not necessary to use the surface of the original document carrying roller 5 as a reference for white density.
It is possible to completely avoid deterioration of correction accuracy due to roller contamination. Further, since it is not necessary to use a special roller such as that coated with Teflon, the conveyance of the original is stable, and the auxiliary roller is completely unnecessary. Therefore, it is possible to realize a facsimile apparatus that is compact and inexpensive and can obtain high image quality.

In this embodiment, the correction photoelectric conversion elements 3 are arranged on both sides of the original reading photoelectric conversion element 2, but they may be arranged on only one side. Further, the number of pixels of the correction photoelectric conversion element 3 may be one or plural. When there are a plurality of pixels, it is possible to include a procedure of obtaining the change rate of the average value of the output, for example.

Furthermore, as shown in FIG. 3, a white film 14 may be pressed against the surface of the correction photoelectric conversion element 3.

Next, another embodiment of the image reading apparatus according to the present invention will be described with reference to FIGS. Figure 4
5 is a diagram showing the positional relationship among the original reading photoelectric conversion element 2, the shading correction photoelectric conversion element 3, the light-shielding film 15b, and the original 6 of the image reading apparatus 1 of the present embodiment, and FIG. FIG. 7 is a diagram showing a cross-sectional structure in the AA direction of the original reading photoelectric conversion element section of the image reading apparatus shown in FIG. 6, and FIG. 6 is a white density output correction photoelectric conversion element section of the image reading apparatus shown in FIG. It is a figure which shows the cross-section of a BB direction.

In this embodiment, the shading correction photoelectric conversion elements 3 are provided on both sides of the aligned original reading photoelectric conversion elements 2. Irradiation light beam 20 from the illumination light source 16
Is reflected by the original 6 and then enters the photoelectric conversion element 2.
A light shielding film 15 a is provided below the photoelectric conversion element 2 so that light from the illumination light source 16 does not directly enter. A light-shielding film 15b is formed on the surface of the correction photoelectric conversion element 3 so that light from the outside does not enter, and an irradiation light beam 20 from the original illumination light source 16 directly enters the photoelectric conversion element 3 so that it is below the light. A certain light shielding film 15a is omitted. The photoelectric conversion elements 2 and 3 and the light shielding films 15a and 15b are formed on the glass substrate 18
It is formed on the top and the top is covered with a protective film 19.
The glass substrate 18 is fixed on the fixed aluminum plate 17. The light shielding films 15a and 15b may be any film that does not transmit light, and are, for example, metal films formed by a sputtering method or a vapor deposition method. In order to allow the light beam 20 emitted from the illumination light source 16 to directly enter the shading correction photoelectric conversion element 3, the corresponding portion of the light shielding film formed for the original reading photoelectric conversion element 2 may be removed.

In the image reading apparatus 1 of the present embodiment having such a structure, the correction photoelectric conversion element 3 always photoelectrically converts the direct incident light from the same illumination light source 16, so that the photoelectric conversion element 3 is used. This is substantially the same as the surface of is covered with a white member. Therefore, the change of the white density output due to the temperature change or the light deterioration can be corrected by the same method as the correction method shown in FIG. Again,
Since the surface of the document conveying roller 5 is not used as a standard for the white density, a normal roller having a large conveying force can be used as the document conveying roller 5, and an auxiliary roller for stable conveyance is not particularly required. As a result, a compact and inexpensive high-quality facsimile device can be obtained.

FIG. 7 is a diagram showing still another embodiment of the image reading apparatus included in the facsimile apparatus according to the present invention. The image reading device 21 of the present embodiment has the original reading photoelectric conversion element 2, but does not include the shading correction photoelectric conversion element 3 in particular.

The image reading unit 21 of the present embodiment differs from the conventional image reading unit and the above-described embodiment in that the length of the document feeding roller 5 in the main scanning direction is shorter than the size of the transmission document 6 and the document is read. A white film 14 is formed on the original reading photoelectric conversion element 2 which is not opposed to the conveying roller 5.
Is pressed against.

Prior to transmitting the original, the output voltage of the photoelectric conversion element 2 in the portion covered with the white film 14 is measured. Next, it is calculated how much the measured voltage changes from the initial output voltage at room temperature stored in the memory of the facsimile apparatus, and the change rate is obtained. Further, the rate of change of the photoelectric conversion elements 2 arranged in the left-right direction is interpolated, and the output voltage with respect to the white density of each pixel of the original reading photoelectric conversion elements 2 below the original conveyance roller 5 is calculated.

This calculation procedure is the same as that in the above embodiment, but in this embodiment, the correction is performed by using a part of the original reading photoelectric conversion element 2. Document transport roller 5
Does not require white surface density, so it is not necessary to perform a special surface treatment for preventing stains, and a roller having a high coefficient of friction with paper can be used. Further, the auxiliary roller is unnecessary. The white film 14 is made of a material such as Teflon that does not easily get dirty and is pressed against the original reading photoelectric conversion element 2. At the time of shading correction, the photoelectric conversion element 2 directly below the white film 14 photoelectrically converts the white density of the white film 14, and at the time of reading the original, the original surface of the transmission original 6 conveyed by the conveyance roller 5 is photoelectrically converted. .. At this time, the white film 14 presses the transmission original 6 against the original reading photoelectric conversion element 2, so that the transport roller 5 is pressed.
Even in the non-existent portion, there is no problem that the image quality is deteriorated such as floating of the transmission document 6.

Also according to this embodiment, a compact and inexpensive facsimile machine with high image quality can be obtained.

Although the embodiment in which the image reading apparatus according to the present invention is applied to the facsimile apparatus has been described here, it is obvious that the present invention can be applied to an image scanner apparatus or the like as long as the apparatus has an image reading mechanism. Let's see

[0058]

According to the present invention, since it is not necessary to use the surface of the document conveying roller itself as a reference for the white density, deterioration of correction accuracy due to roller contamination is completely avoided, and the temperature of the photoelectric conversion element for reading the document is reduced. Changes in white density output due to changes and light deterioration can be corrected with high accuracy, and there is no need to use special rollers such as those with Teflon coating, so the originals are transported stably and image reading without auxiliary rollers is required. The device is obtained.

Further, if this image reading apparatus is adopted, the construction of the carrying section is particularly simplified, so that a small-sized and inexpensive high-quality facsimile apparatus or image scanner apparatus is provided.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing the entire structure of an embodiment of a facsimile apparatus including an image reading apparatus according to the present invention.

FIG. 2 is a diagram showing a positional relationship among an original reading photoelectric conversion element, a shading correction photoelectric conversion element, a white member and an original of an image reading apparatus included in the facsimile apparatus of FIG.

FIG. 3 is a diagram showing another embodiment of the image reading apparatus of the facsimile apparatus according to the present invention.

FIG. 4 is a diagram showing a positional relationship among an original reading photoelectric conversion element, a shading correction photoelectric conversion element, a light shielding film, and an original in another embodiment of the image reading apparatus included in the facsimile apparatus according to the present invention. ..

5 is a diagram showing a cross-sectional structure of the image reading apparatus shown in FIG. 4 in the AA direction.

FIG. 6 is a diagram showing a cross-sectional structure of the image reading device shown in FIG. 4, taken along the line BB.

FIG. 7 is a diagram showing still another embodiment of the image reading apparatus included in the facsimile apparatus according to the present invention.

FIG. 8 is a diagram showing a temperature dependence characteristic of an output voltage when a photoelectric conversion element photoelectrically converts white density.

FIG. 9 is a diagram showing a change characteristic of an output voltage with time when a photoelectric conversion element photoelectrically converts white density.

FIG. 10 is a perspective view schematically showing the entire structure of an example of a conventional facsimile apparatus using a white surface-treated conveying roller and an auxiliary roller.

FIG. 11 is a diagram illustrating a conventional shading correction method using an interpolation method.

FIG. 12 is a diagram illustrating a shading correction method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image reading device 2 Photoelectric conversion element for reading original 3 Photoelectric conversion element for shading correction 4 White member 5 Original conveying roller 6 Original 7 Image recording device 8 Recording paper 9 Recording paper conveying roller 10 Image processing circuit 11 Facsimile device 12 White surface treatment Conveyor roller 13 Auxiliary roller 14 White film 15 Light-shielding film 16 Light source 17 Aluminum plate 18 Glass plate 19 Protective film 20 Irradiated light beam 21 Image reading device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tasaku Kiyono 502 Jinritsucho, Tsuchiura-shi, Ibaraki Prefecture Hiritsu Seisakusho Co., Ltd. (72) Inventor Katsuo Oki 502 Jinritsucho, Tsuchiura-shi, Ibaraki Hitsuritsu Co., Ltd. Machinery Research Laboratory (72) Inventor Hiromitsu Fukuda 502 Jinritsucho, Tsuchiura City, Ibaraki Prefecture Hitate Manufacturing Co., Ltd. (72) Inventor Motoo Oga 1410 Inada, Katsuta City, Ibaraki Hitachi Tokai Plant, Ltd.

Claims (18)

[Claims] 1. A photoelectric conversion element for reading an original, which converts image information of an original to be read into an electric signal, and an analog output voltage corresponding to the original density from the photoelectric conversion element for reading the original, which is A / D-converted to obtain a density level. In an image reading apparatus having an image processing circuit for converting into a digital signal indicating a tonal value, a shading correction photoelectric conversion element having the same structure as the original reading photoelectric conversion element and arranged in the vicinity of the photoelectric conversion element. A means for facing the shading correction photoelectric conversion element to provide a reflection surface having a constant reference white density, and a device for shading correction photoelectric conversion element photoelectrically converting light reflected from the reference white density reflection surface. An image reading apparatus comprising: means for correcting the density gradation value based on an output. 2. An original reading photoelectric conversion element for converting image information of an original to be read into an electric signal, and an analog output voltage corresponding to the original density from the original reading photoelectric conversion element, which is A / D converted to a density level. In an image reading apparatus having an image processing circuit for converting into a digital signal indicating a tonal value, a shading correction photoelectric conversion device having the same structure as the original reading photoelectric conversion device and arranged on one side in the longitudinal direction of the photoelectric conversion device array. A conversion element, means for facing the shading correction photoelectric conversion element and providing a reflection surface having a constant white density at all times, and the shading correction photoelectricity obtained by photoelectrically converting light reflected from the reference white density reflection surface. An image reading apparatus comprising: a unit that corrects the density gradation value based on the output of the conversion element. 3. The image reading apparatus according to claim 1 or 2, wherein the means for correcting the density gradation value is such that the current output of the shading correction photoelectric conversion element is α times the initial value. An image reading apparatus, which is a unit for correcting the density gradation value by a constant rate according to the magnification α. 4. An original reading photoelectric conversion element for converting image information of an original to be read into an electric signal, and an analog output voltage corresponding to the original density from the original reading photoelectric conversion element, which is A / D converted to a density level. In an image reading apparatus having an image processing circuit for converting into a digital signal indicating a tonal value, a shading correction photoelectric conversion device having the same structure as the original reading photoelectric conversion device and arranged on both sides in the longitudinal direction of the photoelectric conversion device array. A conversion element, means for facing the shading correction photoelectric conversion element and providing a reflection surface having a constant white density at all times, and the shading correction photoelectricity obtained by photoelectrically converting light reflected from the reference white density reflection surface. An image reading apparatus comprising: a unit that corrects the density gradation value based on the output of the conversion element. 5. The image reading apparatus according to claim 4, wherein the means for correcting the density gradation value has an average of current outputs of the shading correction photoelectric conversion elements on both sides thereof being α times an initial value. In this case, the image reading apparatus is means for correcting the density gradation value at a constant rate according to the magnification α. 6. The image reading device according to claim 4, wherein the means for correcting the density gradation value has a current output of the shading correction photoelectric conversion elements on both sides which is α times and β times an initial value, respectively. , The density gradation value is α + (β−α) n / (N−1) depending on the pixel position, where n is the pixel number of the photoelectric conversion element, and N is the total number of pixels of the original reading photoelectric conversion element. An image reading device, which is a means for performing correction. 7. The image reading device according to claim 1, wherein the means for providing a reflection surface having the reference white density is fixed over the shading correction photoelectric conversion element. An image reading device characterized in that 8. The image reading apparatus according to claim 1, wherein the means for providing the reflection surface having the reference white density is pressed so as to cover the shading correction photoelectric conversion element. An image reading device characterized in that the surface is a white film. 9. A photoelectric conversion element for reading an original for converting image information from an original to be read into an electric signal, which has a light-shielding film on a back surface thereof for blocking light directly incident from the original illuminating light source, and the photoelectric conversion for reading the original. An image processing circuit for A / D converting an analog output voltage corresponding to the document density from the device to a digital signal indicating a density gradation value, and the photoelectric conversion device having the same structure as the document reading photoelectric conversion device. And a photoelectric conversion element for shading correction, which has a light-shielding film on the surface that blocks the incident light from the document conveying roller and is arranged near the document-conveying roller, and directly receives only the incident light from the document-illuminating light source; An image reading device comprising means for correcting the density gradation value based on the output of the shading correction photoelectric conversion element obtained by photoelectrically converting light. Place 10. A photoelectric conversion element for reading an original for converting image information from an original to be read into an electric signal, which has a light-shielding film on a back surface thereof for blocking direct incident light from the original illuminating light source, and the photoelectric conversion for reading the original. An image processing circuit for A / D converting an analog output voltage corresponding to the document density from the device to a digital signal indicating a density gradation value, and the photoelectric conversion device having the same structure as the document reading photoelectric conversion device. A photoelectric conversion element for shading correction, which is arranged on one side of the row and has a light-shielding film on the surface for blocking the incident light from the document conveying rollers, etc., for directly capturing only the incident light from the document illumination light source, and the direct light from the document illumination light source. Image reading, comprising: means for correcting the density gradation value based on the output of the shading correction photoelectric conversion element that photoelectrically converts incident light. Equipment. 11. The image reading apparatus according to claim 9 or 10, wherein the means for correcting the density gradation value is such that the current output of the shading correction photoelectric conversion element is α times the initial value. An image reading apparatus, which is a unit for correcting the density gradation value by a constant rate according to the magnification α. 12. A photoelectric conversion element for reading an original, which has a light-shielding film on a back surface thereof for blocking direct incident light from an original illumination light source and converts image information from an original to be read into an electric signal, and the photoelectric conversion for reading the original. An image processing circuit for A / D converting an analog output voltage corresponding to the document density from the device to a digital signal indicating a density gradation value, and the photoelectric conversion device having the same structure as the document reading photoelectric conversion device. A photoelectric conversion element for shading correction, which is arranged on both sides of the row and has a light-shielding film on the front surface that blocks the incident light from the original document conveyance rollers or the like, and takes in only the direct incident light from the original document illumination light source from the back surface; Means for correcting the density gradation value based on the output of the shading correction photoelectric conversion element obtained by photoelectrically converting the directly incident light of Image reader. 13. The image reading apparatus according to claim 12, wherein the means for correcting the density gradation value has an average of the current outputs of the shading correction photoelectric conversion elements on both sides thereof being α times the initial value. In this case, the image reading apparatus is means for correcting the density gradation value at a constant rate according to the magnification α. 14. The image reading apparatus according to claim 12, wherein the means for correcting the density gradation value has a current output of the shading correction photoelectric conversion elements on both sides which is α times and β times an initial value, respectively. , The density gradation value is α + (β−α) n / (N−1) depending on the pixel position, where n is the pixel number of the photoelectric conversion element, and N is the total number of pixels of the original reading photoelectric conversion element. An image reading device, which is a means for performing correction. 15. An original reading photoelectric conversion element for converting image information of an original to be read sent by an original feeding roller shorter than a reading width into an electric signal, and an original density from the original reading photoelectric conversion element. In an image reading apparatus having an image processing circuit for A / D converting an analog output voltage and converting it into a digital signal indicating a density gradation value, the image reading apparatus is opposed to a photoelectric conversion element for reading an original at a position where the original feeding roller is not provided and is always constant. A white film having a smooth surface that gives a reflective surface having a reference white density, and then based on the output of the photoelectric conversion element for reading the original, which is photoelectrically converted from the light reflected from the reference white density reflecting surface immediately before reading the original. An image reading apparatus comprising means for correcting the density gradation value of the original read in. 16. The image reading device according to claim 15, wherein the means for correcting the density gradation value, when the current output of the shading correction photoelectric conversion element is α times the initial value, An image reading apparatus comprising means for correcting the density gradation value at a constant rate according to a magnification α. 17. A facsimile device comprising the image reading device according to claim 1 and an image recording device for converting a transmitted electric signal into image information. 18. An image scanner device comprising the image reading device according to claim 1 as an image reading means.