Image reading device

Abstract

To obtain an image reading device in which a shadow based on a thickness of a document sheet is properly formed and a skew of the document sheet is properly detected.SOLUTION: An image sensor part 31 generates a read image by optically reading an image of a document sheet 101 at a first position in a conveyance path of a document sheet 101. A timing sensor detects the document sheet 101 at a second position on an upstream side of the image sensor part 31. The image sensor part 31 includes a first light source 51 and a second light source 52 arranged along the conveyance path. Based on a timing at which the document sheet 101 is detected by a timing sensor 32, a skew detection part 41a sets an irradiation light amount of the first light source 51 on a downstream side to be smaller than an irradiation light amount of the second light source 52 in a period in which a shadow image formed by the thickness of the document sheet is captured by the image sensor part 31.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image reading device. [Background technology]

[0002] One image reading device calculates the amount of skew of a document sheet based on a shadow image that appears at the boundary between the document portion contained in the document image read from the document sheet and the background portion, which is an image of the document transport path (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-26755 A Summary of the Invention [Problem to be solved by the invention]

[0004] Typically, a light source in the image sensor unit irradiates light, and the reflected light is detected by an image sensor (light receiving element) in the image sensor unit, thereby generating a read image.

[0005] However, as in the above-described image reading device, depending on the irradiation conditions of the light from the light source, a shadow based on the thickness of the original sheet may not be formed appropriately.

[0006] The present invention has been made in consideration of the above problems, and aims to provide an image reading device that can properly form a shadow based on the thickness of the original sheet and properly detect skew of the original sheet. [Means for solving the problem]

[0007] The image reading device according to the present invention includes a conveying device that conveys an original sheet along a conveying path; an image sensor unit that generates a read image by optically reading an image of the original sheet at a predetermined first position on the conveying path; a timing sensor that detects the original sheet at a predetermined second position on the conveying path; and a skew detection unit that detects skew of the original sheet based on the read image obtained by the image sensor unit. Here, the second position is a position upstream of the first position on the conveying path. The image sensor unit includes a first light source and a second light source arranged along the conveying path, and the second light source is arranged upstream of the first light source on the conveying path. The skew detection unit reduces the amount of light emitted by the first light source to be less than the amount of light emitted by the second light source during a period when a shadow image formed by the thickness of the original sheet is captured by the image sensor unit, based on the timing when the original sheet is detected by the timing sensor. [Effects of the Invention]

[0008] According to the present invention, an image reading device can be obtained in which a shadow based on the thickness of an original sheet is properly formed and skew of the original sheet can be properly detected.

[0009] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a side view showing the internal configuration of an image reading device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the image reading apparatus shown in FIG. [Figure 3] FIG. 3 is a diagram illustrating the capturing of a shadow image by the image sensor unit 31 in FIG. [Figure 4] FIG. 4 is a diagram showing an example of a shadow image in a read image. [Figure 5]FIG. 5 is a timing chart illustrating the operation of the image reading device shown in FIGS. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] Fig. 1 is a side view showing the internal configuration of an image reading device according to an embodiment of the present invention. The image reading device shown in Fig. 1 is a device such as a scanner, a copier, a facsimile machine, or a multifunction peripheral.

[0013] 1 includes a device body 1, contact glasses 1a and 1b arranged on the top surface of the device body 1, an image sensor unit 2, and a document cover 3. The document cover 3 includes an automatic document feeder 4.

[0014] The contact glass 1a is a transparent member on which a document is placed when image reading is performed without using the automatic document feeder 4. The contact glass 1b is a transparent member over which a document passes when image reading of the document image is performed while the automatic document feeder 4 is automatically transporting the document.

[0015] The image sensor unit 2 reads an original image from an original sheet. Specifically, when the image of an original is read while the automatic document feeder 4 is automatically transporting the original, the image sensor unit 2 is a sensor that optically reads the original image of the original as it passes through a predetermined image reading position in the original transport path. The image sensor unit 2 reads the original image line by line. The image sensor unit 2 includes a light source (such as a light-emitting diode) and a light-receiving element (such as a line sensor). The light source emits light, and the light-receiving element detects the light reflected off the original or the like via the contact glasses 1a and 1b, and outputs an electrical signal corresponding to the amount of reflected light. The controller 41, described below, receives this electrical signal and generates the original image (i.e., image data of the original image) based on this electrical signal.

[0016] The document cover 3 is a rotatable member that can make surface contact with the contact glass 1a, and it presses the document tightly against the contact glass 1a and prevents ambient light from entering the device through the contact glasses 1a and 1b during image reading. The automatic document feeder 4 also includes a document tray 11 on which document sheets are placed and a transport device 21 that transports the document sheets to the image sensor unit 2. The document sheets placed on the document tray 11 are passed one by one over the contact glass 1b by the transport device 21 and discharged onto the discharge tray 14. Specifically, the transport device 21 includes a paper feed roller 12 and a transport roller 13. The paper feed roller 12 feeds the document sheets, and the transport roller 13 transports the document sheets along the transport path. The paper feed roller 12 comes into contact with the document sheets on the document tray 11 and feeds the document sheets one by one.

[0017] Furthermore, the image sensor unit 2 can change its image reading position by a drive device (not shown). When image reading is performed using the automatic document feeder 4, the image reading position of the image sensor unit 2 is set to the position where the document passes on the contact glass 1b, and the image sensor unit 2 optically reads the image of the document conveyed by the automatic document feeder 4 as it passes over the contact glass 1b. Here, the image sensor unit 2 is a color image sensor that reads document images of multiple colors, such as RGB, at different image reading positions in the conveyance direction. In this embodiment, a CIS (Contact Image Sensor) is used as the image sensor unit 2, and when image reading is performed using the automatic document feeder 4, the image sensor unit 2 is positioned directly below the contact glass 1b.

[0018] The feed rollers 12 and the transport rollers 13 are driven by a drive device such as a motor to transport the originals along the transport path. The discharge tray 14 is a tray on which the original sheets dropping from the end of the transport path are stacked. The lift device 22 raises and lowers the original tray 11 using a conventional method.

[0019] Furthermore, the image reading device further includes an image sensor unit 31 and a timing sensor 32 .

[0020] The image sensor unit 31 generates a read image by optically reading an image of the original sheet at a predetermined first position on the conveyance path.

[0021] The timing sensor 32 is a sensor (such as an optical sensor) that detects the original sheet at a predetermined second position on the conveying path. Here, the second position is a position on the conveying path upstream of the first position, as shown in FIG. 1, for example.

[0022] Fig. 2 is a block diagram showing the electrical configuration of the image reading device shown in Fig. 1. As shown in Fig. 2, the image reading device further includes a controller 41. The controller 41 includes a processor that executes a program, an ASIC (Application Specific Integrated Circuit), etc., and controls the image sensor units 2, 31 and the automatic document feeder 4 (conveyor device 21, lift device 22, etc.) to read the image of the document sheet and obtain image data of the image of the document sheet (document image).

[0023] The controller 41 operates as a skew detection unit 41a and a correction processing unit 41b.

[0024] The skew detection unit 41 a detects skew of the original sheet based on the read image obtained by the image sensor unit 31 .

[0025] Fig. 3 is a diagram illustrating the capturing of a shadow image by the image sensor unit 31 in Fig. 1. Fig. 4 is a diagram illustrating an example of a shadow image in a read image. For example, as shown in Fig. 3, the image sensor unit 31 includes a first light source 51 and a second light source 52 arranged along the transport path, and further includes an image sensor 53 as a light receiving element. The second light source 52 is disposed upstream of the first light source 51 on the transport path. A shadow image 102 resulting from the thickness of the original sheet 101 is formed in front of the original sheet 101.

[0026] Based on the timing when the timing sensor 32 detects the original sheet 101, the skew detection unit 41a reduces the amount of light emitted by the first light source 51 to be less than the amount of light emitted by the second light source 52 during the period when the image sensor unit 31 captures the shadow image 102 formed by the thickness of the original sheet 101. As a result, the amount of light emitted by the first light source 51 from in front of the leading edge of the original sheet 101 is less than the amount of light emitted by the second light source 52 from behind the leading edge of the original sheet 101, so that the shadow image 102 is reliably formed. Therefore, for example, as shown in FIG. 4 , when the original sheet 101 is skewed at an skew angle A, the image 201 and shadow image 202 of the original sheet 101 appear skewed at the skew angle A in the read image.

[0027] 5 is a timing chart illustrating the operation of the image reading device shown in FIGS. 1 and 2. In this embodiment, as shown in FIG. 5, for example, the skew detection unit 41a determines the timing T2 at which image data acquisition from the image sensor 53 begins, the timing T3 at which the first light source 51 begins to turn on, and the timing T1 at which the second light source 52 begins to turn on, based on the timing T0 at which the original sheet 101 is detected by the timing sensor 32. Here, the timings T1, T2, and T3 are each a predetermined time after the timing T0, and, for example, as shown in FIG. 5, in the time series, T3≧T2>T1>T0. Note that this predetermined time is set in advance based on the linear velocity of the original sheet 101.

[0028] As a result, during the period in which the shadow image 102 is captured, the skew detection unit 41a turns on the second light source 52 but does not turn on the first light source 51. Specifically, the timing T1 at which the second light source 52 starts to turn on is the time before the leading edge of the original sheet 101 passes the first position (the image reading position of the image sensor unit 31), and the timing T2 at which the first light source 51 starts to turn on is the time at which the leading edge of the original sheet 101 passes the first position.

[0029] That is, during the period in which the image of the original sheet 101 is read, the skew detection unit 41a sets the amount of light emitted by the first light source 51 and the amount of light emitted by the second light source 52 to be the same.

[0030] The oblique detection unit 41a may start turning on the first light source 51 at a lighting start timing T1 with an amount of light emitted therefrom that is smaller than that of the second light source 52, and may make the amount of light emitted therefrom the same at lighting start timing T2. Additionally, the oblique detection unit 41a may start turning on the second light source 52 at timing T0 with an amount of light emitted therefrom that is greater than that at lighting start timing T2 and thereafter, and may make the amount of light emitted therefrom the same as that of the first light source 51 at lighting start timing T2. Alternatively, the amount of light emitted by the second light source 52 may be greater at timing T0 than that at lighting start timing T2 and thereafter, and may be gradually attenuated until it becomes the same as the amount of light emitted by the first light source 51 at lighting start timing T2 and thereafter.

[0031] The skew detection unit 41a also identifies the skew angle A of the original sheet 101 based on the above-described read image. Specifically, for example, as shown in Fig. 4, the angle between the direction in which the shadow image 202 in the read image extends (the direction of the long edge of the shadow image 202) and the main scanning direction is identified as the skew angle A. Then, the correction processing unit 41b corrects the image of the original sheet by rotating the image of the original sheet in the read image by the skew angle A in the direction opposite to the skew direction.

[0032] Next, the operation of the image reading device will be described.

[0033] When an original sheet 101 is placed on the original tray 11 and a predetermined user operation is detected, the controller 41 starts an image reading operation (scan job) of the original sheet. When the image reading operation starts, the controller 41 causes the conveying device 21 to convey the original sheets 101 on the original tray 11 one by one to the discharge tray 14, and executes image reading with the image sensor units 2 and 31.

[0034] At this time, after the transport of the original sheet 101 has started, when the original sheet 101 is detected by the timing sensor 32, the skew detection unit 41a, based on that timing, as described above, reduces the amount of light emitted by the first light source 51 to be less than the amount of light emitted by the second light source 52 during the period when the shadow image 102 formed by the thickness of the original sheet 101 is captured by the image sensor unit 31.

[0035] The skew detection unit 41a starts acquiring the read image from the image sensor 53 before the period in which the shadow image 102 is captured, identifies the shadow image 202 included in the read image, and determines whether or not there is skew. At this time, the skew detection unit 41a derives the skew angle A from the shadow image 202.

[0036] When the skew detection unit 41a determines that the original sheet 101 is skewed, the correction processing unit 41b performs rotation correction on the original image (the image of the original sheet 101 itself) in the read image based on the derived skew angle A.

[0037] As described above, according to the above embodiment, the image sensor unit 31 generates a read image by optically reading an image of the original sheet 101 at a first position on the transport path of the original sheet 101. The timing sensor 32 detects the original sheet 101 at a second position upstream of the image sensor unit 31. The image sensor unit 31 includes a first light source 51 and a second light source 52 arranged along the transport path. The skew detection unit 41a reduces the amount of light emitted by the first light source 51 compared to the amount of light emitted by the second light source 52 during a period when the image sensor unit 31 captures a shadow image formed by the thickness of the original sheet, based on the timing when the timing sensor 32 detects the original sheet 101. Note that in this embodiment, the skew angle of the original sheet is determined based on a shadow image of the leading edge of the original sheet, but this is merely an example. It goes without saying that the skew angle can also be determined from a shadow image of the edge of the original sheet. In addition to the leading edge in this embodiment, the skew angle can also be determined from shadow images of the trailing edge, left and right edges. When the skew angle is determined from the shadow image of the trailing edge of the original sheet, the timing to turn off the second light source or reduce the amount of light is the time when the trailing edge of the original sheet passes the first position.

[0038] As a result, when capturing a shadow image, the amount of light emitted by the first light source 51 downstream of the image reading position is low, so that a shadow based on the thickness of the original sheet is formed appropriately, and the skew of the original sheet 101 is detected properly.

[0039] It should be noted that various changes and modifications to the above-described embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the subject matter and without diminishing its intended advantages. In other words, it is intended that such changes and modifications be included within the scope of the claims. [Industrial Applicability]

[0040] The present invention is applicable to, for example, an image reading device, including a device equipped with a photosensitive drum, a fixing roller, and the like. [Explanation of symbols]

[0041] 2,31 Image sensor section 21 Conveyor equipment 32 Timing sensor 41a Oblique detection unit 41b Correction processing unit 51 1st light source 52 Second light source 53 Image Sensor

Claims

1. a conveying device that conveys the original sheet along a conveying path; an image sensor unit that generates a read image by optically reading an image of the original sheet at a predetermined first position on the conveyance path; a timing sensor for detecting the original sheet at a predetermined second position on the conveying path; a skew detection unit that detects skew of the original sheet based on the read image obtained by the image sensor unit, the second position is a position on the transport path upstream of the first position, the image sensor unit includes a first light source and a second light source arranged along the transport path, the second light source is disposed upstream of the first light source on the transport path, the skew detection unit reduces the amount of light emitted by the first light source to be less than the amount of light emitted by the second light source during a period in which a shadow image formed by a thickness of the original sheet is captured by the image sensor unit, based on the timing at which the original sheet is detected by the timing sensor; An image reading device characterized by:

2. the skew detection unit determines a timing at which the first light source and the second light source start to turn on based on a timing at which the timing sensor detects the document sheet; the second light source starts to be turned on before the leading edge of the document sheet passes through the first position; the timing at which the first light source starts to light is when the leading edge of the document sheet passes through the first position; 2. The image reading device according to claim 1, wherein:

3. the skew detection unit determines a timing to turn off the second light source or a timing to reduce the amount of light based on a timing at which the timing sensor detects the document sheet; the timing of turning off the second light source or reducing the amount of light is the time when the trailing edge of the document sheet passes through the first position; 2. The image reading device according to claim 1, wherein:

4. 2. The image reading device according to claim 1, wherein the skew detection unit sets the amount of light emitted by the first light source and the amount of light emitted by the second light source to be equal to each other during the image reading period of the document sheet.

5. Further comprising a correction processing unit, the skew detection unit specifies a skew angle of the original sheet based on the read image; the correction processing unit corrects the image of the original sheet by rotating the image of the original sheet in the read image by the skew angle in a direction opposite to the skew direction; 5. The image reading device according to claim 1, wherein:

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