JPH10177331A - Document position detection device - Google Patents

Abstract

(57) [Problem] To improve the original detection accuracy without lowering the original reading reproducibility even with an original pressing member using a wavelength absorber that is not colorless in the visible region. SOLUTION: A document pressing means (not shown) which presses a document to be read and has a wavelength absorbing agent applied / mixed on the document pressing surface side, and a light source (FIG. 2) for irradiating light absorbed by the wavelength absorbing agent. (Not shown), an infrared light separating filter 101 for separating reflected light having an absorption wavelength out of the reflected light from the document surface, and an optical signal passing through the infrared light separating filter 101 is received for each line and subjected to photoelectric conversion. Infrared CCD 102 and infrared CC
Detector 1 for detecting an original from an optical signal received at D102
04, and the detection unit 104 is configured to determine the first and second predetermined ranges of the light intensity of the preset infrared light absorption wavelength.
By using the threshold, the original and the non-original portion are determined based on whether or not the intensity of the optical signal output from the infrared CCD 102 is within a predetermined range, and the original is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document position detecting device for detecting the position and shape of a document in a copying machine or an image reading device (image scanner) using a prescan system.

[0002]

2. Description of the Related Art Conventionally, it has been difficult for a copying machine or an image reading apparatus to detect a white object (document) from a white background (pressing plate or document conveying belt). For this reason, pre-scanning is performed by a copying machine or the like before actual document reading,
An image is read as a digital image, and the image is processed to determine the size of the document. Hereinafter, a specific example will be described.

FIG. 13 is an explanatory diagram showing a main configuration of a conventional image reading apparatus. In the figure, 1 is a document to be read, 2 is a contact glass on which the document is set, 3
Is an optical scanning unit that optically scans along the contact glass 2, 4 is a light source having an emission wavelength including an absorption wavelength and irradiating the original 1, 5 is a scanning mirror, 6 is a reflection mirror, and 7 is image light for each line. CCD line sensor to read to the camera, 8 is CC
A condenser lens for condensing image light on the D-line sensor 7, 9
Reference numeral denotes a signal light (image light), and reference numeral 10 denotes a pressure plate on which a wavelength absorbing agent is applied on the inner side to bring the original 1 into close contact with the contact glass 2.

In the image reading apparatus constructed as described above, the light from the light source 4 is formed into an elongated slit, and the slit light is emitted in a direction substantially perpendicular to the slit direction (sub-scanning direction).
Is scanned while being moved to irradiate the original surface. Further, the irradiation light is sequentially focused on the CCD line sensor 7 via the condenser lens 8 to read an image.

[0005] Further, as a reference technical document related to the above, for example, "Document detection method and apparatus" disclosed in Japanese Patent Application Laid-Open No. 8-139848 is disclosed. More specifically, a predetermined wavelength region (for example, 750 nm to 8 nm) in the invisible region is applied to the original pressing surface of the pressure plate pressing the original on the original platen.
(50 nm) is applied. Of the reflected light obtained by irradiating the original or the original pressing surface with the scanning light, the light transmitted through the filter means that transmits light in a predetermined wavelength region is received by the light receiving element. The reflected light from the document contains light in a predetermined wavelength range and does not include the pressure plate surface, so that there is a difference in received light intensity, and the presence or absence of the document is determined based on this difference.

[0006]

However, in the prior art as described above, the wavelength absorber actually absorbed in the infrared region is not colorless in the visible region but looks green or brownish. Therefore, when reading a color image original, especially when the original is highly transparent such as OHP film or tracing paper, the color of the original is affected by the background color of the pressure plate surface and differs from the actual original color. It will be read in a different color. In addition, there has been a problem that the pressure plate portion is read in a certain color, and in a monochrome copying machine, the edge of a copy is blackened and reproduced.

The ratio of wavelength absorption by the pressure plate is 1
Because it is not 00% and is often inferior to this, in the case of a gray original that absorbs even in the infrared region, it may be determined that there is no original even though the original is present, causing a detection error. Will be lost.

For this reason, actually, the wavelength absorber is compared with the wavelength absorption in the visible region to make a judgment. This necessitates the addition of an unnecessary image reading mechanism for visible wavelengths in a monochrome digital copying machine, which leads to an increase in cost and detection errors.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and even if a document pressing member using a wavelength absorber that is not colorless in the visible region, the document reading reproducibility is not reduced and the document It is a first object to improve the detection accuracy of.

As an alternative to the current wavelength absorber, it has characteristics higher than that of the wavelength absorber, and improves the document detection accuracy with a simple configuration without adding a special visible wavelength image reading mechanism. This is a second object.

[0011]

According to a first aspect of the present invention, there is provided a document position detecting device for pressing a document to be read, and applying a wavelength absorbing agent to a document pressing surface side. / Mixed document pressing means, a light source for irradiating light absorbed by the wavelength absorber, and light reflected by the document surface obtained by irradiating the document with light from the light source. A light separating means for separating reflected light, a photoelectric converting means for receiving an optical signal passing through the light separating means for each line, performing photoelectric conversion and outputting the same, and a document for detecting a document from reflected light from the photoelectric converting means An optical signal output from the photoelectric conversion unit using first and second thresholds that define a predetermined range of light intensity of a preset infrared light absorption wavelength. Whether the strength of the steel is within the predetermined range Determine the more original and non-original portion,
The document detection is performed.

That is, two thresholds are set for the light intensity in the infrared region, and the characteristics of the wavelength absorbing agent are surely shown by determining whether or not the reflected infrared light is in a certain value region within the two thresholds. Since the original and the non-original portion are discriminated from each other, accurate original detection is realized.

According to a second aspect of the present invention, in the document position detecting device, the document detecting means includes a first and a second for defining a predetermined range of light intensity of a preset infrared light absorption wavelength.
And the first and second thresholds that define a predetermined range of the separated visible light intensities, the intensity of the optical signal output from the photoelectric conversion means is reduced by the first and second thresholds. And the non-document portion is discriminated based on whether or not they are within the first and second thresholds of the visible wavelength.

That is, by setting two thresholds for the light intensity in both the infrared region and the visible wavelength region, it is possible to accurately confirm that the signal being monitored reliably shows the sensitivity characteristics of the wavelength absorber. Can be detected, and more accurate document detection is realized.

According to a third aspect of the present invention, in the document position detecting device, the document detecting means is arranged such that the light intensity signal is below a certain threshold in an absorption wavelength region and the light intensity signal is in a separated visible wavelength region. If the intensity signal is equal to or higher than a certain threshold, it is determined that the document is a non-document portion.

That is, taking advantage of the fact that there is almost no substance that absorbs in the infrared region and reflects light in the visible region as much as the wavelength absorber, the light intensity signal is below a certain threshold in the absorption wavelength region. If the light intensity signal is equal to or higher than a certain threshold in the wavelength region of the visible wavelength, it is possible to easily determine that the document is a non-document portion (press plate).

According to a fourth aspect of the present invention, in the document position detecting device, when the wavelength light is applied / mixed to the original pressing surface of the original pressing means, the light source light of the light source is applied to the original pressing surface. The specific wavelength other than the color in the visible region is relatively increased.

That is, in the case of a monochrome copying machine, a specific wavelength other than the color in the visible region of the pressure plate is relatively intensified so that the portion becomes white when the portion is copied, so that the pressure plate becomes gray or black. To avoid being reproduced in
A good copy image is obtained.

Further, in the document position detecting device according to the fifth aspect, the document pressing surface of the document pressing means is coated / mixed with a wavelength absorbing agent and a dye having a protective color relationship in a visible region,
The color in the visible region of the original pressing surface is a grayish color.

That is, if the wavelength absorber alone is used, even in the visible region, there is a bias in the reflectance due to the wavelength, and the color balance at the time of copying is biased. However, in a color copying machine, the pressure plate is grayed out. The deviation between the color of the read image and the color of the actual document is reduced without increasing the light in a specific visible range during reading.

Further, in the document position detecting device according to claim 6, the document pressing surface of the document pressing means is constituted by a reflection type diffraction grating. Document position detection device.

That is, since the pressure plate diffracts only a specific wavelength of infrared light with high efficiency, providing a light receiving element such as a CCD for that wavelength can provide a simpler configuration than a case where a wavelength absorber is applied. In addition, it is possible to easily determine the original and the non-original. The method may also diffract a wavelength in the visible region without diffracting a wavelength in the infrared region. In this case as well, depending on the setting of the diffraction angle, it is possible to distinguish between a document and a non-document by detecting whether or not the diffracted light of a certain wavelength returns.

According to a seventh aspect of the present invention, at least the original pressing surface of the original pressing means is detachable.

That is, by making the original pressing surface of at least the original pressing means detachable, even if the original pressing surface becomes dirty and affects the image, cleaning or replacement can be easily performed. Reliability is improved.

In the document position detecting device according to the eighth aspect, the document pressing surface of the document pressing means has a fine uneven shape, and a wavelength absorber is applied / mixed in the concave portion. Things.

That is, the original pressing surface of the original pressing means, for example, the surface of the ADF transport belt, is formed into a fine irregular shape,
By applying / mixing the wavelength absorbing agent into the concave portion, the wavelength absorbing agent is prevented from coming into direct contact with an original or the like, so that peeling of the wavelength absorbing agent can be prevented and reliability is improved.

In the document position detecting apparatus according to the ninth aspect, the photoelectric conversion means may be a one-dimensional CCD without an infrared light absorption filter or a photodiode having a sensitivity up to a long wavelength of infrared light. It is composed of

That is, since there is a sensor sensitivity up to long wavelengths of infrared light, accuracy can be improved, or various wavelength absorbers can be effectively used.

According to a tenth aspect of the present invention, the photoelectric conversion means detects a wavelength separated for each color image, and detects a color signal of a red area. In this case, the color balance of the color image is matched with the color balance of the document.

That is, by adjusting the sensitivity of each CCD for detecting each separated wavelength, color development on a red copy can be suppressed, and a color image can be balanced.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a document position detecting device according to the present invention will be described with reference to the accompanying drawings, [Embodiment 1], [Embodiment 2], [Embodiment 3], [Embodiment 4]. ,
[Embodiment 5], [Embodiment 6], [Embodiment 7], [Embodiment 8], [Embodiment 9], [Embodiment 10] will be described in this order.

[Embodiment 1] In this embodiment 1,
The wavelength absorber is applied / applied to the original pressing surface of the pressure plate, and the original size and the position of the original are detected by pre-scanning. In this case, the light source of a normal image reading apparatus often cuts the wavelength of infrared light in consideration of the reading balance of a color image. Here, a light source having a wavelength that can absorb a wavelength absorber is used. .

(Configuration of the First Embodiment) FIG. 1 is an explanatory view showing the main configuration of a document position detecting apparatus according to the first embodiment, and the basic parts are the same as those of the above-described document reading apparatus of FIG. It is. In the figure, reference numeral 101 denotes an infrared light separating filter as light separating means for transmitting / reflecting light of an infrared wavelength;
Reference numeral 02 denotes a one-dimensional infrared light CCD that receives the infrared light separated by the infrared light separation filter 101 and outputs an infrared light signal corresponding to the received light.
A visible light CCD as one-dimensional photoelectric conversion means for receiving the visible light transmitted through 1 and outputting an optical signal corresponding to the light;
Reference numeral 104 denotes a detection unit as document detection means for detecting the intensity of the output of the infrared light CCD 102, that is, the position and shape of the document and the non-document surface based on a predetermined threshold area described later. Reference numeral 8 denotes the above-described condenser lens, 9 denotes signal light, 10
Reference numeral denotes a pressure plate as document pressing means.

The surface of the pressure plate 10 on the side of the original 1 is coated with a wavelength absorbing agent, and the light source 4 having a wavelength at which the wavelength absorbing agent is absorbed is used. When a halogen lamp such as a copying machine is used, the light source itself has an emission wavelength of up to several μm. FIG. 2 is a graph showing the reflectance characteristics of the infrared light wavelength absorber.

(Operation of the First Embodiment) Next, the characteristic operation of the above configuration will be described. The light of the infrared wavelength to be absorbed is separated by a transmission type or reflection type infrared light separation filter 101, and an image is formed on an infrared light CCD 102. Then, a certain threshold is provided for the infrared light signal.

It is known that the edge of the portion of the output signal of the infrared light CCD 102 which is less than a certain value and which is considered to have light absorbed by the pressure plate 10, that is, the point where a certain threshold can be obtained, is determined as the edge of the document. This is the method. However, in such a case, a black or gray document has a high infrared absorption rate in the visible region, and it cannot be distinguished from a document or a pressure plate.

Therefore, as shown in FIG. 3, when the position and shape of the original and the non-document surface are detected by the intensity of the light intensity signal of the absorption wavelength by the pressure plate, the threshold of the light intensity signal of the absorption wavelength is changed by the infrared absorbing agent. Two values, a little smaller value and a slightly larger value, are provided for the absorptance of. Then, a case where the intensity of the signal light is between the two thresholds is determined to be an optical signal from the pressure plate 10, and the edge of the document is defined from the correlation between them. As a result, the accuracy of distinguishing the original from the pressure plate can be increased.

[Embodiment 2] In this embodiment 2,
In addition to providing two thresholds in the infrared region, the reflectance from the pressure plate in the visible region is defined in order to further increase the accuracy, thresholds corresponding to the thresholds are provided, and the edges of the document are determined from both.

(Structure of the Second Embodiment) Therefore, the structure of the second embodiment is different from the structure of FIG. 1 in that the output of the CCD 103 for visible light is given to the detector 104. The basic configuration is the same as that of FIG.

(Operation of Embodiment 2) In the above configuration, the absorption wavelength and a certain visible wavelength are separated by the transmission type or reflection type infrared light separating filter 101, and these are separated by the infrared light CCD 102 and the visible light. An image is formed on the light CCD 103. Then, as shown in FIG. 4, two thresholds are provided for the light intensity signal of the absorption wavelength and the light intensity signal of the other wavelength, respectively, and when the intensity of the signal light is between the two thresholds in the infrared region, In addition, when the optical signal intensity in the visible region is also at the two set thresholds, it is determined to be the document edge.

Thus, it is possible to accurately recognize that the signal being monitored exhibits the sensitivity characteristic of the wavelength absorber, and the accuracy of discrimination between the original and the pressure plate is improved.

[Embodiment 3] In this embodiment 3,
In the above-described first and second embodiments, a simpler determination is performed to determine the original and the pressure plate.

(Structure of Third Embodiment) Therefore, the structure of the third embodiment is the same as that of the above-described second embodiment, and a description thereof will be omitted.

(Operation of Embodiment 3) In the above configuration, as shown in FIG. 5, the light intensity signal is below the threshold in the absorption wavelength region, and the light intensity signal is in the separated visible wavelength region. If the signal is above a certain threshold, it is determined that the signal is a pressure plate. This is because, as shown in Table 1 below, the wavelength absorber is absorbed in the infrared region,
In addition, it takes advantage of the fact that there is almost no substance that reflects light in the visible region. That is, the absorption characteristics of the pressure plate are defined by these two thresholds.

[0045]

[Table 1]

It should be noted that in Table 1 above, only the infrared absorber is currently marked with a circle in both A and B. Therefore, it can be determined from Table 1 whether or not the characteristics of the pressure plate (infrared absorbing agent) are exhibited.

[Embodiment 4] By the way, the visible region on the pressure plate becomes gray or black when copied by a monochrome copying machine. Therefore, in Embodiment 4, this problem is avoided as follows. I do.

(Structure of Embodiment 4) Embodiment 4
In this method, a light source is used in which a specific wavelength of a color in the visible region of the pressure plate is relatively increased when a wavelength absorber is applied or mixed on the original pressing surface of the pressure plate. This can be realized by filtering the intensity of the wavelength not absorbed and relatively reducing the intensity. Therefore, the basic configuration of the fourth embodiment is the same as that of the second embodiment.

(Operation of the Fourth Embodiment) Next, the characteristic operation of the above configuration will be described. The specific wavelength is a wavelength at which the wavelength absorber absorbs in the visible region. Thus, even if the reflected light in the visible region is some absorption, uniform reflected light is returned to the sensor over the entire visible region. The reflected light has the same effect on the sensor as the reflected light from the white original, and the visible region on the pressure plate is not reproduced as a gray or black image in the case of a monochrome copying machine on a copy image. . This state is shown in FIG.

[Fifth Embodiment] The fifth embodiment is directed to a document position detecting device of a color copying machine. In other words, when the original surface side of the pressure plate is a specific color and a certain amount of faint light is transmitted, the color tone is lost when reading a color original, and the actual color differs greatly from the read color when reading a color image. Cause. In other words, the original is more or less transparent to the illumination light, the color of the platen is fused with the actual color of the original, and an image in which the color of the platen is emphasized is actually read. For this reason, it is desirable that the pressure plate is not a specific color but a color such as white or gray.

Therefore, in a device similar to that of the above-described embodiment, a colorant having a protective color relationship in the visible region with the wavelength absorbing agent is mixed into the original side of the platen so that the color in the visible region of the platen is a gray system. So that That is, as shown in FIG. 7, a wavelength absorbing agent 702 and a dye 703 having a complementary color relationship with the wavelength absorbing agent 702 are mixed on the original side of the pressure plate plastic member 701.

Thus, the difference between the color of the read image and the color of the actual document can be obtained without increasing the light transmitted through and reflected from the document at the time of reading from the pressure plate and enhancing the light in a specific visible range. Less.

[Embodiment 6] By the way, the above-mentioned problem is caused not only by the specific absorption of specific infrared light by the wavelength absorber but also by absorption up to the wavelength in the visible region. Only reflect. This will be described below.

Therefore, in an apparatus similar to that of the above-described embodiment, instead of applying a wavelength absorbing agent to the pressing plate portion, as shown in FIG. (Diffraction grating) 801
Stick it. The reflection grating 801 reflects a specific wavelength at a specific angle with a certain wavelength width.

By adjusting the interval between the grating fringes in this constant wavelength range and reflecting a specific infrared wavelength in a specific direction, light of the above-mentioned wavelength does not return to the sensor. That is, as shown in FIG. 8, the infrared light 802 reflected and diffracted by the reflection grating 801 out of the illumination light is deflected in a specific direction and does not return to the optical scanning unit. As a result, the same operation as a pressure plate exhibiting excellent wavelength absorption characteristics that completely absorbs only a specific infrared wavelength is performed.

In this case, a certain infrared wavelength separated by a filter or the like is monitored by a CCD, and one threshold is provided for the infrared wavelength to be discriminated by binarization. it can.

[Embodiment 7] Incidentally, the reading accuracy is affected by the stain on the original pressing portion. Therefore, the dirty portion (here, the conveyor belt) is made removable. A specific example will be described below.

FIG. 9 is an explanatory diagram showing the configuration of an automatic document feeder (ADF) according to the seventh embodiment. In the figure, reference numeral 901 denotes an ADF unit; 902, a transfer belt which is detachable by hand to convey a document to a document reading position;
Reference numeral 03 denotes a belt pressing member that can be manually attached and detached, and that presses the transport belt 902. In particular, the transport belt 902 is configured to be detachable by removing the belt pressing member 903.

[Embodiment 8] By the way, when the wavelength absorbing agent is directly applied to the pressure plate, it is considered that the paint which is the wavelength absorbing agent is peeled off with time when it comes into strong and frequent contact with the document. Therefore, in the eighth embodiment, for example, the following is dealt with.

FIG. 10 is a sectional view showing the structure of an original pressure plate according to the eighth embodiment. In the figure, reference numeral 1001 denotes a pressure plate plastic member, and reference numeral 1002 denotes a wavelength absorber applied to the concave portion of the plastic plate member 1001 which has a fine irregular shape on the surface contacting the original. Further, in addition to the above-mentioned application, it may be mixed with the material of the pressure plate plastic member 1001 itself.

As a result, the wavelength absorbing agent in the concave portion remains even if it comes into strong and frequent contact with the original, and does not need to be replaced for a long time, thereby improving the reliability of the same pressure plate.

[Embodiment 9] A commercially available C
CD is not very sensitive to the infrared region. However, the wavelength absorber has less absorption in the visible region as it absorbs on the longer wavelength side, and exhibits good characteristics for the purpose of the present invention.

In the ninth embodiment, a one-dimensional CCD for detecting an image is a one-dimensional CCD without an infrared light filter.
Alternatively, a photodetector such as a photodiode which is sensitive to long wavelengths of infrared light as shown below is used.

FIG. 11 is an explanatory diagram showing a photodiode array according to the ninth embodiment. In the figure, 110
Reference numeral 1 denotes a photodiode array having an element size of about 1 to 4 mm and including 35 to 46 elements.

With such a light detecting device, an effective wavelength absorber can be used for discriminating the original from the pressure plate.

[Embodiment 10] When reading a color original, if the CCD has sensitivity up to the infrared region, or if visible light near the infrared region or the infrared region enters the CCD, the read image is reproduced. The result is a red copy. Thus, in the tenth embodiment, the following will be dealt with.

FIG. 12 is an explanatory diagram showing the configuration of the document position detecting device according to the tenth embodiment. In the figure, a filter 1201 having a certain absorptivity in the red and infrared regions is added to the front of the one-dimensional CCD 103 in the optical system described above,
Other configurations are the same.

In the above configuration, the sensitivity of the one-dimensional CCD 103 for detecting each separated wavelength is adjusted to make the color signal of the red area relatively low, so that the color balance of the color image matches the color balance of the original. Do not shift. This makes it possible to read a color image in a natural color. This can also be achieved by electrically adjusting the amplification factor.
Alternatively, this can be realized by adding the filter 1201 having a little absorptivity in the red and infrared regions as described above.

[0069]

As described above, according to the document position detecting device of the present invention (claim 1), two thresholds are set for the light intensity in the infrared region, and the infrared reflected light has two thresholds. Since the original and the non-original portion are determined based on whether or not the characteristic of the wavelength absorbing agent is surely shown depending on whether or not the area is within a certain value range, accurate original detection is realized.

According to the document position detecting device of the present invention (claim 2), two thresholds are set for the light intensity in both the infrared region and the visible wavelength region.
It is possible to accurately detect that the signal being monitored shows the sensitivity characteristic of the wavelength absorber, and more accurate document detection is realized.

According to the document position detecting device of the present invention (claim 3), the wavelength absorbing agent is absorbed in the infrared region,
In addition, utilizing the fact that there is almost no substance that reflects light in the visible region, the light intensity signal is below a certain threshold in the absorption wavelength region, and above the certain threshold in the separated visible wavelength region. In some cases, it can be easily determined that the document is a non-document portion.

Further, according to the document position detecting device of the present invention (claim 4), in the case of a monochrome copying machine, the specific wavelength other than the color in the visible region of the pressure plate is relatively intensified, and that portion is copied. In order to make the plate white, it is possible to avoid that the platen becomes gray or black and reproduce on a copy, and a good copy image is obtained.

According to the document position detecting device of the present invention (claim 5), the color plate is grayed out in the color copying machine. The difference between the color of the read image and the color of the actual document is reduced.

According to the document position detecting device of the present invention, since the pressure plate diffracts only a specific infrared wavelength with high efficiency, a light receiving element such as a CCD for that wavelength is provided. Thus, it is possible to distinguish between a document and a non-document with a simpler configuration and more easily than when a wavelength absorber is applied.

According to the document position detecting device of the present invention, since at least the document pressing surface of the document pressing means is detachable, the document pressing surface may become dirty and affect the image. Even if it occurs, cleaning or replacement can be easily performed, and the reliability of document detection is improved.

According to the original position detecting device of the present invention, the original pressing surface of the original pressing means, for example, the surface of the transport belt of the ADF, has a fine uneven shape, and the concave portion has a wavelength absorbing agent. By coating / mixing, the wavelength absorber does not come into direct contact with the original or the like, so that the wavelength absorber can be prevented from peeling off, and the reliability is improved.

Further, according to the document position detecting device of the present invention (claim 9), the sensitivity is improved up to long wavelengths of infrared rays, so that the accuracy is improved or various wavelength absorbers are effectively used. It is possible to do.

Further, according to the document position detecting device of the present invention (claim 10), each C for detecting each separated wavelength can be used.
Since the sensitivity of the CD is adjusted, color development on a red copy can be suppressed, and a color image can be balanced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a main configuration of a document position detecting device according to a first embodiment.

FIG. 2 is a graph showing the reflectance characteristics of the infrared wavelength absorber according to the first embodiment.

FIG. 3 is a graph showing an output change and an example of a set threshold of one element of the infrared light CCD according to the first embodiment;

FIG. 4 is a graph showing a wavelength, a signal intensity, and a setting threshold example of an infrared wavelength absorber according to a second embodiment.

FIG. 5 is a graph showing a wavelength, a signal intensity, and a setting threshold example of an infrared wavelength absorber according to a third embodiment.

FIG. 6 is a graph showing document position detection according to a fourth embodiment.

FIG. 7 is an explanatory diagram showing a configuration of a plastic member of a pressure plate according to a fifth embodiment.

FIG. 8 is an explanatory diagram illustrating a main configuration of a document reading apparatus according to a sixth embodiment.

FIG. 9 illustrates an automatic document feeder (AD) according to a seventh embodiment.
It is explanatory drawing which shows the structure of F).

FIG. 10 is a cross-sectional view illustrating a configuration of a document pressure plate according to an eighth embodiment.

FIG. 11 is an explanatory diagram showing a photodiode array according to a ninth embodiment.

FIG. 12 is an explanatory diagram showing a configuration of a document position detecting device according to a tenth embodiment.

FIG. 13 is an explanatory diagram showing a main configuration of a conventional document reading apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original 4 Light source 10 Pressure plate 101 Infrared light separation filter 102 CCD for infrared light 103 CCD for visible light 104 Detector 701, 1001 Plastic member for pressure plate 702, 1002 Wavelength absorber 703 Dye 801 complementary to wavelength absorber 801 Reflection type grating 902 Conveying belt 903 Belt holding member 1101 Photodiode array 1201 Filter

Claims (10)

[Claims] 1. A document pressing means for pressing a document to be read and applying / mixing a wavelength absorbing agent to a document pressing surface side, a light source for irradiating light absorbed by the wavelength absorbing agent, and Of the reflected light from the document surface obtained by irradiating the light from the light source, a light separating means for separating reflected light having an absorption wavelength, and an optical signal passing through the light separating means is received for each line, and photoelectric conversion is performed. And a document detecting means for detecting a document based on the reflected light from the photoelectric converting means, wherein the document detecting means has a predetermined range of light intensity of a predetermined infrared light absorption wavelength. The first and second thresholds are used to determine whether a document is from a non-document portion based on whether the intensity of the optical signal output from the photoelectric conversion unit is within the predetermined range, and perform document detection. An original position detecting device, comprising: 2. The document detecting means according to claim 1, wherein said first and second thresholds defining a predetermined range of light intensity of a predetermined infrared light absorption wavelength, and a predetermined range of separated light intensity of a visible wavelength. Using the first and second thresholds defined, the intensity of the optical signal output from the photoelectric conversion means is in the range of the first and second thresholds and the first and second thresholds of the visible wavelength. 2. The document position detecting device according to claim 1, wherein a document and a non-document portion are discriminated based on whether or not the document is inside the document, and document detection is performed. 3. The non-document portion, wherein the light intensity signal is equal to or less than a certain threshold in an absorption wavelength region and is equal to or more than a certain threshold in a separated visible wavelength region. 2. The document position detecting device according to claim 1, wherein it is determined that there is a document. 4. The light source light of the light source relatively intensifies a specific wavelength other than a color in a visible region of the document pressing surface when a wavelength absorber is applied / mixed to the document pressing surface of the document pressing means. 4. The document position detecting device according to claim 1, wherein: 5. A document pressing surface of the document pressing means is coated / mixed with a dye having a protective color relationship in a visible region with a wavelength absorber, and a color of the document pressing surface in a visible region is a gray-based color. 4. The document position detecting device according to claim 1, wherein the position of the document is detected. 6. A document pressing surface of said document pressing means is constituted by a reflection type diffraction grating.
The document position detecting device according to 1. 7. The document position detecting device according to claim 1, wherein at least a document pressing surface of said document pressing means is detachable. 8. A document pressing surface of said document pressing means has a fine irregular shape, and a wavelength absorber is applied to said concave portion.
The document position detecting device according to claim 1, wherein the document position detecting device is mixed. 9. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion means comprises a one-dimensional CCD without an infrared light absorption filter or a photodiode having a sensitivity up to a long wavelength of infrared light. Document position detection device. 10. The photoelectric conversion means for detecting a wavelength separated for each color image, wherein a signal of a color in a red area is relatively lowered, and a balance between a color of a color image and a document 8. The document position detecting device according to claim 1, wherein the original position is matched with the color balance.