JP2021093587A - Image reading device and image forming apparatus - Google Patents

Abstract

To provide an image reading device that can accurately detect a shadow of a document even if the document conveying speed is accelerated and the document approaches a background plate, and an image forming apparatus.SOLUTION: An image reading device 1 reads an image from a document D automatically conveyed along a background plate 161, and is provided with a light source 111 that illuminates the document D and the background plate 161, a CCD line sensor 131 that detects the amount of reflected light from the document D and the background plate 161 and outputs image data, and a light guide optical system, such as a mirror 113 that guides the reflected light from the document D and the background plate 161 to the CCD line sensor 131, and the image reading device detects a shadow of the document D on the background plate 161 from the image data in order to correct the read image. The light source 111 illuminates the document D and the background plate 161 from the upstream side in a document conveyance direction, and the light guide optical system guides the reflected light L directed to the downstream side in the document conveyance direction to the CCD line sensor 131.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an image reading device and an image forming device, and more particularly to a technique for accurately detecting a shadow of a document when reading an image from the document by a sheet-through method.

Conventionally, in the case of a sheet-through method in which an image reading device illuminates a document while transporting the document using an automatic document feeder (ADF) and reads an image based on the amount of reflected light, the document is read. At the same time, the size of the document is detected to cut out only the effective document part, or the skew (tilt) is detected to perform skew correction.

Therefore, for example, as shown in FIG. 5, a shadow seen between the background plate (also referred to as a white plate) 501 located on the back side of the document and the tip of the document D during scanning on the image data. A technique for detecting 502 is known. Since the shadow 502 has a lower gradation value than the document D, the tip of the document D can be detected by detecting the change in the gradation value (FIG. 5A).

Further, if the positions of the head ends of the document D are compared between one end 503r and the other end 503l in the width direction of the document D, the skew of the document D can be detected (FIG. 5B). By using such a technique, even in the case of the sheet-through method, it is possible to cut out an effective document portion and perform skew correction.

Japanese Unexamined Patent Publication No. 2006-186959

Noise is superimposed on the brightness of the light source that illuminates the document and the output of the image sensor used to read the document, and it is necessary to prevent the output fluctuation of the image sensor due to the noise from being mistakenly recognized as the shadow of the document. In addition, the shadow of the document must be detected depending on whether the output change continues over a certain number of scanning lines.

On the other hand, the demand for high speed image reading devices continues to increase, and in order to meet this demand, documents must be transported at high speed. However, since it is difficult to shorten the reading cycle of the image sensor, simply increasing the transport speed of the document reduces the number of lines for reading the shadow of the document. Therefore, there arises a problem that the shadow of the document cannot be detected with high accuracy.

Further, even if the distance between the original and the background plate is reduced due to curling of the original, the number of lines for reading the shadow of the original is reduced, so that the shadow of the original may not be detected. .. If the shadow of the original cannot be detected, the above-mentioned cropping process and skew correction cannot be performed.

The present disclosure has been made in view of the above-mentioned problems, and it is possible to accurately detect the shadow of the original even if the conveying speed of the original is increased or the original approaches the background plate. It is an object of the present invention to provide an image reading device and an image forming device capable of performing the same.

In order to achieve the above object, the image reading device according to one embodiment of the present disclosure is an image reading device that reads an image from a document conveyed along a background plate, and is a lighting means for illuminating the document and the background plate. An image pickup means that detects the amount of reflected light from the document and the background plate and outputs image data, and a light guide means that guides the reflected light from each reading position of the document and the background plate to the image pickup means. The lighting means illuminates the document and the background plate from the upstream side of any reading position in the document transport direction, and the light guide means heads downstream from each reading position in the document transport direction. It is characterized in that the reflected light is guided to the image pickup means.

In this case, in order to correct the scanned image, a detection means for detecting the shadow of the document on the background plate from the image data may be provided.

Further, the illumination means, the light guide means, and the image pickup means may form a close contact optical system or a reduction optical system.

In addition, a second imaging means that detects the amount of reflected light from the document and the background plate and outputs image data, and a second light guide that guides the reflected light from the document and the background plate to the imaging means. The second light guide means may guide the reflected light directed in a direction orthogonal to the document transport path to the second image pickup means.

Further, the posture of the light guide means is the first posture for guiding the reflected light toward the downstream side in the document transport direction from the document surface to the image pickup means, and the reflected light toward the direction orthogonal to the document transport path is described. When the switching means for switching to either the posture leading to the imaging means or the switching means switches to the first posture when the detection means detects the shadow, and when the image data is used as a scanned image. May switch to the second posture.

Further, the image reading device according to one embodiment of the present disclosure is an image reading device that reads an image from a document conveyed along a background plate, and includes a lighting means for illuminating the document and the background plate, the document, and the document. The image pickup means for detecting the amount of reflected light from the background plate and outputting image data, and the light guide means for guiding the reflected light from each reading position of the document and the background plate to the image pickup means. The lighting means illuminates the document and the background plate from a downstream side of any reading position in the document transport direction, and the light guide means emits the reflected light toward the upstream side from each reading position in the document transport direction. It is characterized by leading to an imaging means.

Further, the image forming apparatus according to one form of the present disclosure is characterized by including an image reading device according to one form of the present disclosure and an image forming means for forming an image using an image read by the image reading device. And.

By doing so, the shadow of the document reflected on the background plate in the document transport direction can be enlarged, so that the number of scanning lines can be increased even if the document transport speed is high, and the shadow of the document can be detected accurately. be able to.

It is a figure which shows the main structure of the image reading apparatus which concerns on embodiment of this disclosure. (A) is a diagram showing the main configuration of the close contact type line sensor 170 according to the present embodiment, and (b) is a diagram showing the main configuration of the close contact type line sensor 270 according to the prior art. (A) is a diagram showing the main configuration of the slider 110 according to the present embodiment, and (b) is a diagram showing the main configuration of the slider 310 according to the prior art. It is a figure which compares the position of the tip of the document D in which the shadow of the document D is detected in this embodiment and the prior art, and is an enlarged view thereof. (A) is a diagram for explaining a method of detecting the tip of the document D from the shadow of the document D, and (b) is a diagram for explaining a method of detecting the skew of the document D from the shadow of the document D.

Hereinafter, embodiments of the image reading device according to the present disclosure will be described with reference to the drawings.
[1] Configuration of Image Reading Device First, the configuration of the image reading device according to the present embodiment will be described.

As shown in FIG. 1, the image reading device 1 includes a scanner unit 100 and an automatic document transporting unit 150. A reading glass 101 is arranged above the scanner unit 100, and the scanner unit 100 reads a document placed on the scanning glass 101 in the case of the platen set method and the scanning glass in the case of the sheet-through method. An image is read from a document conveyed by the automatic document transfer unit 150 along 101.

In the case of the platen set method, the scanner unit 100 rotates and drives the pulley 102 by a drive motor (not shown), and pulls the wire 103 hung on the pulley 102 in the direction of arrow A to drive the first slider 110 and the first slider 110. 2 Slider 120 slides in the direction of arrow A. In the case of the sheet-through method, the document is stationary at the home position as shown in FIG. 1 so that the document can be read directly under the background plate 161 provided in the automatic document transport unit 150.

The first slider 110 includes light sources 111 and 112 and a mirror 113. The light sources 111 and 112 are used to illuminate the document on the reading glass 101, and the reflected light L is guided to the second slider 120 by the mirror 113. .. The second slider 120 uses the mirror 121 and the mirror 122 to fold back the reflected light L and guide it to the lens 130.

The reflected light L is collected by the lens 130, incident on the line sensor 131, and the amount of light is detected for each pixel. The detection signal of the line sensor 131 is input to the control unit 140, and digital image data is generated. As the line sensor 131, a CCD (Charge Coupled Device) line sensor may be used, or another line sensor may be used. The first slider 110, the second slider 120, and the lens 130 form a light guide optical system that guides the reflected light L to the line sensor 131. Further, the first slider 110, the second slider 120, the lens 130, and the line sensor 131 constitute a reduction optical system and are used for reading the surface of the document D.

In the case of the sheet-through method, the automatic document transporting unit 150 feeds out the document D one by one from the bundle of documents placed on the document tray 151, transports the documents D one by one along the transport path 152, and then ejects the originals to the paper output tray 153. To do. In the automatic document transport unit 150, a white background plate 161 is arranged at a position illuminated by the light source 111 of the first slider stationary at the home position.

Further, a contact image sensor (CIS) 170 is arranged along the transport path 152 on the downstream side of the background plate 161 in the transport path 152 of the document D, and the contact image sensor (CIS) is arranged. A background plate 171 is also arranged so as to face the 170. As will be described later, the close contact type line sensor 170 constitutes an close contact optical system and is used for reading the back surface of the document D.
[2] Close contact type line sensor 170
Next, the configuration of the close contact type line sensor 170 will be described.

As shown in FIG. 2A, the close contact type line sensor 170 guides the emitted lights LU and LL of the light sources 201 and 211 to the document D and the background plate 171 using the light guide members 202 and 212. The light sources 201 and 211 and the light guide members 202 and 212 are supported by the support members 203 and 213, respectively, and the support members 203 and 213 are all fixed to the frame 207.

The reflected light L, which is the emitted light LU and LL reflected by the document D or the background plate 217, is guided to the line sensor 206 by the lens 205. That is, the lens 205 constitutes a light guide optical system. The lens 205 is also fixed to the frame 207. The line sensor 206 is mounted on the sensor substrate 208, and the sensor substrate 208 is fixed to the frame 207. The line sensor 206 may be a CCD line sensor or another line sensor.

As shown in FIG. 2B, in the close contact type line sensor 270 according to the prior art, the optical axis of the lens 225 is orthogonal to both the document transport direction (arrow B direction) and the main scanning direction. , The reflected light L traveling in the optical axis direction is guided to the line sensor 226. On the other hand, in the close contact type line sensor 170 according to the present embodiment, the angle θ is on the downstream side in the document transport direction with respect to the direction in which the optical axis of the lens 205 is orthogonal to both the document transport direction and the main scanning direction. The reflected light L, which is inclined by a degree and travels in the direction of the optical axis, is guided to the line sensor 206.
[3] Slider 110
Next, the configuration of the slider 110 will be described.

As shown in FIG. 3A, the slider 110 irradiates the document D and the background plate 171 with the emitted lights LU and LL of the light sources 111 and 112. The light sources 111 and 112 are fixed to the frame of the slider 110. The reflected light L, which is the emitted light LU and LL reflected by the document D or the background plate 217, is guided to the line sensor 131 by the mirror 113 or the like. The mirror 113 is also fixed to the frame of the slider 110.

The reading glass 101 is attached to the housing 301 of the optical writing device 1, and the step sheet 302 has a step between the document D and the reading glass 101 so that the reading glass 101 is not soiled by contact with the document D. Is provided. The reduction optical system including the mirror 113 or the like that guides the reflected light L to the line sensor 131 forms the reflected light L on the light receiving surface of the line sensor 131 in consideration of the step portion.

As shown in FIG. 3B, in the slider 310 according to the prior art, the reflected light L traveling in a direction orthogonal to both the document transport direction (arrow B direction) and the main scanning direction is transmitted to the line sensor 331. The reflected light L is reflected so as to be guided. On the other hand, the slider 110 according to the present embodiment is a reflected light L that travels in a direction inclined by an angle θ degree to the downstream side in the document transport direction with respect to a direction orthogonal to both the document transport direction and the main scanning direction. To the line sensor 131.

The tilt angle θ of the optical axis of the lens 205 of the close contact type line sensor 170 and the tilt angle θ of the reflected light L guided by the mirror 113 of the slider 110 to the line sensor 131 may be the same or different. You may. Considering the process of detecting the shadow of the document D, the length of the shadow of the document D in the scanned image in the sub-scanning direction (document transport direction) is set to be the same for the slider 110 and the close contact type line sensor 170. Is desirable.
[4] Shadow Length of Manuscript D Next, the shadow length of the manuscript D that can be detected by the present embodiment and the prior art is compared.

FIG. 4 is a diagram illustrating the positional relationship between the light sources 111 and 201, the document D, the background plates 161 and 171 and the line sensors 131, 206, 226 and 331 as viewed from the main scanning direction. In FIG. 4, the light sources 111, 201, 221, and 311 have an outer diameter of 10 mm and a long cylindrical shape in the main scanning direction. The angle between the alternate long and short dash line 401 from the center of the light sources 221 and 311 toward the reading position in the prior art on the background plates 161 and 171 and the alternate long and short dash line 402 orthogonal to the document transport direction (arrow B direction) is 30 degrees. is there.

The centers of the light sources 111, 201, 221 and 311 are located 10 mm upstream from the alternate long and short dash line 402 in the document transport direction. Therefore, the light sources 111 and 201 illuminate the document D and the background plates 161 and 171 from the upstream side of the reading position 421 on the document D and the reading position 423 on the background plates 161 and 171 in the document transport direction. The distance from the point where the alternate long and short dash line 401 intersects the background plates 161 and 171 to the center of the light sources 111, 201, 221 and 311 is 20 mm. The distance from the background plates 161 and 171 to the centers of the light sources 111, 201, 221, and 311 is about 17.3 mm.

The alternate long and short dash line 402 corresponds to the reflected light L1 in the close contact type line sensor 270 and the slider 310 according to the prior art, and is finally incident on the line sensors 226 and 331. On the other hand, the angle at which the reflected light L2 (solid line 404) reflected by the background plates 161 and 171 from the emitted light LL (solid line 403) from the light sources 111 and 201 forms the one-point chain line 402 orthogonal to the document transport direction (arrow B direction). Is 10 degrees. Therefore, the reflected light L2 goes from the reading positions 421 and 423 to the downstream side in the document transport direction. The reflected light L2 finally enters the line sensors 131 and 206.

An enlarged view of the area 411 surrounded by the broken line is the broken line area 412. In the enlarged view, the line sensors 226 and 331 according to the prior art detect the reflected light L1 of the document D at the reading position 421, and the line sensors 131 and 206 according to the present embodiment detect the reflected light L2 of the document D at the reading position 421. Is detected. Further, on the background plates 161 and 171 the reflected light L1 at the reading position 422 is detected by the line sensors 226 and 331 according to the prior art, and the reflected light L2 at the reading position 423 is detected by the line sensors 131 and 206 according to the present embodiment. Detects.

In the process of transporting the document D in the direction of arrow B, before the tip of the document D reaches the transport position 431, the light sources 111, 201, 221 are placed on both the reading positions 422 and 423 on the background plates 161 and 171. Illumination light from 311 arrives. Therefore, both the amount of detected light of the line sensors 226 and 331 according to the prior art and the amount of detected light of the line sensors 131 and 206 according to the present embodiment are large.

Next, from the time when the tip of the document D reaches the transport position 431 to the time before it reaches the transport position 432, the document D blocks the illumination light of the light sources 111 and 201, thereby forming the background plates 161 and 171. The reading position 423 becomes dark. Therefore, the amount of detected light of the line sensors 131 and 206 according to the present embodiment is reduced. That is, when the head of the document D is within this section, the shadow of the document D is detected in the present embodiment.

On the other hand, since the document D does not block the illumination light of the light sources 221 and 311, the reading position 422 on the background plates 161 and 171 is maintained in a bright state. Therefore, the amount of detected light of the line sensors 226 and 331 according to the prior art remains high. That is, when the head of the document D is within this section, the shadow of the document D is not detected by the prior art.

Further, from the time when the tip of the document D reaches the transport position 432 to the time before the tip of the document D reaches the transport position 421, the document D blocks the illumination light of the light sources 111 and 201, so that the document D is on the background plates 161 and 171. Both reading positions 422 and 423 become dark. Therefore, both the amount of detected light of the line sensors 226 and 331 according to the prior art and the amount of detected light of the line sensors 131 and 206 according to the present embodiment are reduced. Therefore, when the head of the document D is within this section, the shadow of the document D is detected in both the present embodiment and the prior art.

After the tip of the document D reaches the reading position 421, the illumination light reflected by the document D is detected in both the present embodiment and the prior art, so that the amount of detected light increases and the shadow of the document D is not detected.

In FIG. 4, in the prior art, the shadow of the document D is detected when the tip of the document D is between the transport position 432 and the scanning position 421, the distance is 0.55 mm, and the resolution is high. In the case of 600 dpi (dot per inch), the number of scanning lines read while the tip of the document D moves over this distance is 12.90.

On the other hand, in the present embodiment, the shadow of the document D is detected when the tip of the document D is between the transport position 431 and the scanning position 421, the distance is 0.73 mm, and the resolution is high. When it is 600 dpi, the number of scanning lines read while the tip of the document D moves over this distance is 17.17.

Therefore, in the present embodiment, the moving distance of the tip of the document D in which the shadow of the document D is detected is 0.18 mm longer than that in the prior art, and the number of scanning lines that can be read during that period is 4.28. Only increase. Therefore, even if the transport speed of the document D is increased or the document D approaches the background plates 161 and 171, the shadow of the document can be detected with high accuracy.
[2] Modified Examples Although the present disclosure has been described above based on the embodiments, it goes without saying that the present disclosure is not limited to the above-described embodiments, and the following modified examples can be implemented. ..
(2-1) In the above embodiment, the case where the tilt angle of the reflected light guided by the light guide optical system to the line sensor is 10 degrees has been described as an example, but it goes without saying that the present disclosure is not limited to this. Instead of this, other angles may be used, and it is desirable that the tilt angle is increased as the document transport speed is faster.

Regarding the light sources 111, 201, 221, and 311, the angle at which the illumination light incident on the line sensors 131, 206, 226, and 331 is emitted is 30 degrees with respect to the perpendicular to the background plates 161 and 171. The case where the distance from the center to the center is 10 mm has been described as an example, but it goes without saying that other angles and dimensions may be used.
(2-2) In the above embodiment, the case where the inclination angle of the reflected light guided by the light guide optical system to the line sensor is constant has been described as an example, but it goes without saying that the present disclosure is not limited to this. Instead of this, the following may be used.

That is, the inclination angle of the reflected light L guided by the light guide optical system to the line sensor may be switched. For example, when detecting the shadow of the document D, if the reflected light L directed in the direction inclined with respect to the direction orthogonal to the document transport direction and the main scanning direction is detected, the document D can be detected in the same manner as in the above embodiment. Since the shadow can be enlarged, the detection accuracy of the shadow can be improved. After the tip of the document D reaches the reading position, the document D can be read with high resolution by detecting the reflected light L in the direction orthogonal to the document transport direction and the main scanning direction.

In this case, a well-known swing translation mechanism may be used to swing and translate the sensor substrate 208 on which the line sensor 206 is mounted and the lens 205 integrally in the close contact type line sensor 170, or the mirror in the slider 110. Only 113 may be oscillated and translated. In this way, the inclination angle of the reflected light L leading to the line sensors 131 and 206 can be switched.
(2-3) In the above modified example, the case where the light guide optical system switches the inclination angle of the reflected light guided to the line sensor has been described as an example, but it goes without saying that the present disclosure is not limited to this. You may also do the following.

That is, the light guide optical system that guides the reflected light L in the direction orthogonal to the document transport direction and the main scanning direction to the line sensor and the reflected light L in the direction inclined with respect to the orthogonal direction are guided to another line sensor. Both the light guide optical system and the light guide optical system may be provided. Even in this way, the shadow of the document D can be enlarged to improve the detection accuracy of the shadow, and the document D can be read with a high resolution.
(2-4) In the above embodiment, the case where the shadow of the document D read prior to the tip of the document D is detected has been described as an example, but it goes without saying that the present disclosure is not limited to this. By detecting the shadow of the document D that is continuously read at the rear end, an effective portion of the document may be cut out or skew may be corrected.

In this case, if the light guide optical system is tilted so as to guide the reflected light L toward the upstream side with respect to the direction orthogonal to the document transport direction and the main scanning direction to the line sensor, the document D Since the number of shadow scanning lines of the document D that can be detected after the rear end has passed the scanning position can be increased, the same effect as that of the above embodiment can be obtained.

Further, when there are restrictions on the size and shape of the space in which the light guide optical system can be provided inside the image reading device 1, only the light guide optical system that detects shadows on the rear end side of the document D can be selected. Is valid for the configuration of this modification.
(2-5) In order to increase the length of the document D in the document transport direction, it is effective if the reflected light L guided by the light guide optical system to the line sensor is inclined as much as possible. However, in consideration of the object of the present disclosure of accurately detecting the shadow of the document D, scanning for reading the shadow of the document D under the conditions that the document transport speed is the same and the reading cycle of the line sensor is also the same. It is desirable to guide the reflected light L at an inclination angle such that the number of lines increases by one or more lines as compared with the case where the reflected light L is not inclined with respect to the document transport direction to the line sensor.
(2-6) Although not particularly mentioned in the above embodiment, the reading positions 421, 422, and 423 are determined by the angle of the reflected light L guided by the light guide optical system to the line sensor.
(2-7) In the above embodiment, an image reading device has been described as an example, but it goes without saying that the present disclosure is not limited to this, and a single-function device such as a copying device or a facsimile machine provided with an image reading device. Alternatively, the present disclosure may be applied to a multi-function peripheral (MFP) having these functions, and the same effect as that of the above embodiment can be obtained.

The image reading device and the image forming device according to the present disclosure are particularly useful as devices capable of accurately detecting shadows on a document when reading an image from the document by a sheet-through method.

1 …………………… Image reader 100 ……………… Scanner unit 110 ……………… Slider 111, 201… Light source 113 ……………… Mirror 131, 206… Line sensor 150 ……………… Automatic document transfer section 161 and 171 ... Background plate 170 ……………… Adhesion type line sensor (CIS)
205 ……………… Lens D …………………… Original L, L1, L2… Reflected light

Claims (8)

An image reading device that reads an image from a document conveyed along a background plate.
Lighting means for illuminating the manuscript and the background plate, and
An imaging means that detects the amount of reflected light from the document and the background plate and outputs image data.
It is provided with a light guide means for guiding the reflected light from each reading position of the document and the background plate to the image pickup means.
The lighting means illuminates the document and the background plate from the upstream side of any reading position in the document transport direction.
The light guide means is an image reading device characterized in that the reflected light heading downstream from each reading position in the document transport direction is guided to the image pickup means. The image scanning apparatus according to claim 1, further comprising a detecting means for detecting a shadow of a document on the background plate from image data in order to correct the scanned image. The image reading device according to claim 1 or 2, wherein the lighting means, the light guide means, and the imaging means form a close contact optical system. The image reading device according to claim 1 or 2, wherein the lighting means, the light guide means, and the imaging means constitute a reduction optical system. A second imaging means that detects the amount of reflected light from the document and the background plate and outputs image data,
A second light guide means for guiding the reflected light from the document and the background plate to the imaging means is provided.
The image reading device according to claim 1 or 4, wherein the second light guide means guides the reflected light directed in a direction orthogonal to the document transport path to the second image pickup means. The first posture that guides the posture of the light guide means toward the image pickup means toward the downstream side in the document transport direction from the document surface, and the image pickup means that the reflected light that faces the direction orthogonal to the document transport path is taken. A switching means to switch to either the posture leading to
Claims 1 to 4 are characterized in that the switching means switches to the first posture when the detection means detects the shadow, and switches to the second posture when the image data is used as a read image. The image reading device according to any one of. An image reading device that reads an image from a document conveyed along a background plate.
Lighting means for illuminating the manuscript and the background plate, and
An imaging means that detects the amount of reflected light from the document and the background plate and outputs image data.
It is provided with a light guide means for guiding the reflected light from each reading position of the document and the background plate to the image pickup means.
The lighting means illuminates the document and the background plate from the downstream side of any reading position in the document transport direction.
The light guide means is an image reading device characterized in that the reflected light heading upstream from each reading position in the document transport direction is guided to the image pickup means. The image reading device according to any one of claims 1 to 7.
An image forming apparatus comprising: an image forming means for forming an image using an image read by the image reading apparatus.

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