JP7433865B2 - Image reading device and image forming device - Google Patents

Description

The present invention relates to a technique for correcting image data representing an image read by an image reading device.

The image reading device reads an image of the original by irradiating the original with light and detecting the reflected light by a reading unit. 2. Description of the Related Art Some image reading devices use a reading unit to read a document conveyed by an document feeder (ADF).

In such image reading devices, variations in the nip pressure and rotational speed of the rollers that transport the original can cause skewed feeding of the original or variations in the position of the original in a direction perpendicular to the transport direction (hereinafter referred to as the main scanning direction). may occur. Patent Document 1 discloses a configuration in which the shadow of the leading edge of the document in the transport direction is detected from image data representing a reading result, and the image data is rotationally corrected based on the tilt angle of the detected shadow of the leading edge of the document with respect to the main scanning direction. is listed.

Japanese Patent Application Publication No. 2010-118911

The image data includes the shadow of the leading edge of the document and the shadow of the edge of the document in the main scanning direction. For example, when printing is performed based on read image data, shadows included in the image data will be printed. As a result, the quality of the formed image may deteriorate.

In view of the above problems, an object of the present invention is to suppress deterioration in quality of read images.

In order to solve the above problems, an image reading device according to the present invention includes: a light source that emits light; a reading section that reads an image of the original by receiving reflected light from the original that passes through a reading position; a facing member that is provided on the opposite side of the light source with respect to the conveyance path through which the document is conveyed and faces the document passing through the reading position; Based on the boundary between the area of the opposing member and the shadow area caused by the light and the edge of the leading edge of the document in the conveyance direction in which the document is conveyed, determining means for determining an inclination angle with respect to a width direction perpendicular to the width direction; and a rotation correction is performed so that the inclination angle becomes small, and the inclination angle is rotated from a leading edge of the document toward a trailing edge of the document. The present invention is characterized by comprising an output means for outputting an image obtained by reading out the read image stored in a memory in the main scanning direction with reference to a position that is a predetermined length away from the boundary in the main scanning direction .

According to the present invention, deterioration in the quality of read images can be suppressed.

FIG. 1 is a configuration diagram of an image forming apparatus in a first embodiment. FIG. 2 is a control configuration diagram of the image reading device in the first embodiment. FIG. 3 is an explanatory diagram of acquisition timing of image data stored in an image memory. FIG. 3 is an explanatory diagram of processing in an edge detection unit according to the first embodiment. FIG. 3 is an explanatory diagram of document information according to the first embodiment. FIG. 3 is an explanatory diagram of registration correction processing according to the first embodiment. 5 is a flowchart of document reading processing according to the first embodiment. FIG. 7 is a diagram showing correction values for thin paper, plain paper, and thick paper.

Preferred embodiments of the present invention will be described below with reference to the drawings. However, the shapes of the components described in this embodiment and their relative arrangement should be changed as appropriate depending on the configuration of the device to which this invention is applied and various conditions, and the scope of this invention is limited. The present invention is not intended to be limited to the following embodiments.

[First embodiment]
[Image forming device]
FIG. 1 is a sectional view showing the configuration of a monochrome electrophotographic copying machine (hereinafter referred to as an image forming apparatus) 100 used in this embodiment. Note that the image forming apparatus is not limited to a copying machine, and may be, for example, a facsimile machine, a printing machine, a printer, or the like. Further, the recording method is not limited to the electrophotographic method, and may be, for example, an inkjet method. Furthermore, the format of the image forming apparatus may be either monochrome or color.

The configuration and functions of the image forming apparatus 100 will be described below using FIG. 1. As shown in FIG. 1, the image forming apparatus 100 includes an image reading device 200 including a document feeding device 201 and a reading device 202, and an image printing device 301. The document feeding device 201 is rotatable with respect to the reading device 202.

<Image reading device>
A pickup roller 103 serving as a feeding unit feeds the document 101 stacked on a tray 102 serving as a stacking unit into the interior of the document feeding device 201 . Separation rollers 104 and 105 are provided to prevent multiple documents 101 from being fed simultaneously by pickup roller 103. The document 101 fed to the conveyance path is conveyed toward the reading position A by a conveyance roller 106 and a lead roller 107. Note that the separation rollers 104 and 105, the conveyance roller 106, and the lead roller 107 are included in the conveyance section.

A transparent glass 108 is arranged at the reading position A, and a reading section 109A is provided on the opposite side of the conveyance path with respect to the glass 108. The reading unit 109A includes an LED 110, an image sensor 111, and an optical component group 112. The image sensor 111 includes a plurality of pixels that receive R (red), G (green), and B (blue) light in the main scanning direction.

The reading unit 109A reads an image on the front surface (first side) of the original 101 in the following manner. Specifically, the LED 110 as a light source irradiates (emits) light onto the surface of the original 101 via the glass 108. Optical component group 112 guides reflected light from document 101 received via glass 108 to image sensor 111 . The image sensor 111 outputs analog image data based on the reflected light it receives. Note that the image sensor 111 simultaneously reads an image for one line in the main scanning direction. Therefore, by reading one line of image by the image sensor 111 multiple times while conveying the original 101, the image sensor 111 can output image data including the entire original 101. An A/D conversion section (not shown) of the reading section 109A converts analog image data into digital image data and outputs the digital image data to the controller 200 (FIG. 2).

A detection sensor 113 that detects the document 101 is provided upstream of the reading position A in the conveyance direction of the document 101 . The controller 200 determines the timing at which the reading unit 109A starts reading the original 101 based on the timing when the detection sensor 113 detects the original 101.

Pressing rollers 114 and 115 press original 101 toward glass 108 . Note that a white guide plate 116 as a facing member is arranged at a position directly facing the reading section 109A between the presser rollers 114 and 115, that is, on the opposite side of the reading section 109A with respect to the conveyance path along which the original is conveyed. Ru.

The document 101 that has passed the reading position A is conveyed toward the reading position B by the conveyance roller 117. A transparent glass 118 is placed at the reading position B, and a reading section 109B is provided on the opposite side of the glass 118 from the transport path. The reading unit 109B has the same configuration as the reading unit 109A, and reads an image on the back side (second side) of the document 101. The timing at which the reading unit 109B starts reading is also determined based on the timing at which the detection sensor 113 detects the document. A white guide plate 119 is arranged at a position directly facing the reading section 109B.

The document 101 that has passed through the reading position B is discharged onto a paper discharge tray 121 by a paper discharge roller 120 .

A white reference plate 122 is provided on the right side of the glass 108 as a reference reading member for acquiring shading data.

<Image printing device>
Inside the image printing apparatus 301, sheet storage trays 302 and 304 are provided. The sheet storage trays 302 and 304 can each store different types of recording media. For example, the sheet storage tray 302 stores A4 size plain paper, and the sheet storage tray 304 stores A4 size thick paper. Note that the recording medium is something on which an image is formed by an image forming apparatus, and includes, for example, paper, resin sheets, cloth, OHP sheets, labels, and the like.

The recording medium stored in the sheet storage tray 302 is fed by a pickup roller 303 and sent out to a registration roller 308 by a conveyance roller 306. Further, the recording medium stored in the sheet storage tray 304 is fed by a pickup roller 305 and sent to a registration roller 308 by conveyance rollers 307 and 306.

Image data output from the image reading device 200 is input to an optical scanning device 311 including a semiconductor laser and a polygon mirror. Further, the outer peripheral surface of the photosensitive drum 309 is charged by a charger 310. After the outer peripheral surface of the photosensitive drum 309 is charged, a laser beam corresponding to an image signal input from the document reading device 200 to the optical scanning device 311 is transmitted from the optical scanning device 311 via a polygon mirror and mirrors 312 and 313. The outer peripheral surface of the photosensitive drum 309 is irradiated with light. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 309.

Subsequently, the electrostatic latent image is developed with toner in the developing device 314, and a toner image is formed on the outer peripheral surface of the photosensitive drum 309. The toner image formed on the photosensitive drum 309 is transferred onto a recording medium by a transfer charger 315 provided at a position facing the photosensitive drum 309 (transfer position). The registration roller 308 feeds the recording medium to the transfer position in accordance with the transfer timing at which the image is transferred to the recording medium by the transfer charger 315.

As described above, the recording medium onto which the toner image has been transferred is sent to the fixing device 318 by the conveyor belt 317, and is heated and pressurized by the fixing device 318, so that the toner image is fixed onto the recording medium. In this way, an image is formed on the recording medium by the image forming apparatus 100.

When image formation is performed in the single-sided printing mode, the recording medium that has passed through the fixing device 318 is discharged to a paper discharge tray (not shown) by paper discharge rollers 319 and 324. In addition, when image formation is performed in the double-sided printing mode, after the fixing process is performed on the first side of the recording medium by the fixing device 318, the recording medium is transferred to is transported to the reversing path 325. Thereafter, the recording medium is conveyed again to the registration roller 308 by the conveyance rollers 322 and 323, and an image is formed on the second side of the recording medium in the manner described above. Thereafter, the recording medium is discharged to a paper discharge tray (not shown) by paper discharge rollers 319 and 324.

Further, when the recording medium on which an image has been formed on the first side is discharged face-down to the outside of the image forming apparatus 100, the recording medium that has passed through the fixing device 318 passes through the paper discharge roller 319 and is transferred to the conveyance roller 320. It is transported in the direction towards. Then, just before the rear end of the recording medium passes through the nip of the conveyance roller 320, the rotation of the conveyance roller 320 is reversed, so that the recording medium is transferred to the ejection roller with the first surface of the recording medium facing downward. 324, and is discharged to the outside of the image forming apparatus 100.

The above is a description of the configuration and functions of the image forming apparatus 100.

<Control configuration>
FIG. 2 is a block diagram showing an example of a control configuration of the image forming apparatus 100. First, the control configuration of the image printing apparatus 301 will be explained.

As shown in FIG. 2, the system controller 151 includes a CPU 151a, a ROM 151b, and a RAM 151c. Further, the system controller 151 is connected to an analog/digital (A/D) converter 153, a high voltage control section 155, a motor control device 600, sensors 159, and an AC driver 160. The system controller 151 can send and receive data and commands to and from each connected unit.

The CPU 151a executes various sequences related to a predetermined image forming sequence by reading and executing various programs stored in the ROM 151b.

RAM 151c is a storage device. The RAM 151c stores various data such as setting values for the high voltage control section 155 and command values for the motor control device 600, for example.

The system controller 151 receives signals from the sensors 159 and sets the set value of the high pressure control section 155 based on the received signals.

The high voltage control section 155 supplies a necessary voltage to the high voltage unit 156 (charger 310, developer 314, transfer charger 315, etc.) according to the set value set by the system controller 151.

The motor control device 600 controls a motor 509 that drives a load provided in the image printing device 301 in accordance with a command output from the CPU 151a.

The A/D converter 153 receives the detection signal detected by the thermistor 154 for detecting the temperature of the fixing heater 161, converts the detection signal from an analog signal to a digital signal, and transmits the signal to the system controller 151. The system controller 151 controls the AC driver 160 based on the digital signal received from the A/D converter 153. The AC driver 160 controls the fixing heater 161 so that the temperature of the fixing heater 161 becomes a temperature necessary for performing fixing processing. Note that the fixing heater 161 is a heater used for fixing processing, and is included in the fixing device 318.

As described above, the system controller 151 controls the operation sequence of the image forming apparatus 100.

Next, the control configuration of the image reading device 200 will be explained. The CPU 203 controls the image reading apparatus 100 by executing programs stored in the nonvolatile memory 209.

The conveyance motor 201 is a drive source for each roller provided in the document feeding device 201, and is rotationally driven under the control of the controller 200.

The operation unit 202 provides a user interface. The CPU 203 controls the operation unit 202 so that an operation screen for the user to configure settings such as the type of recording medium to be used (hereinafter referred to as paper type) is displayed on the display unit provided on the operation unit 202. do. The CPU 203 receives information set by the user from the operation unit 202 and outputs the information set by the user to the system controller 151.

The system controller 151 transmits information indicating the status of the image forming apparatus to the operation unit 202. Note that the information indicating the state of the image forming apparatus is, for example, information regarding the number of images to be formed, the progress status of image forming operations, sheet jams and double feeding in the image printing apparatus 301 and the document feeding apparatus 201, and the like. The operation unit 202 displays information received from the system controller 151 on the display unit.

The reading units 109A and 109B output digital image data to the controller 200. This image data has a higher numerical value as the intensity of the reflected light increases. This numerical level will be expressed as a brightness level below. Furthermore, hereinafter, the image data output by the reading unit 109A will be referred to as front side image data, and the image data output by the reading unit 109B will be referred to as back side image data.

The front side image data outputted by the reading unit 109A is input to the shading circuit 204A, and the back side image data outputted by the reading unit 109B is inputted to the shading circuit 204B. The shading circuits 204A and 204B perform addition, subtraction, multiplication and division on the image data to correct the effects of non-uniformity in the light amount of the LED 110 and uneven sensitivity of each pixel of the image sensor 111 (shading correction), and Generate uniform image data in the scanning direction.

The surface image data after shading correction by the shading circuit 204A is stored in the image memory 205. On the other hand, the back side image data after shading correction by the shading circuit 204B is input to the image inversion circuit 210.

The image inversion circuit 210 inverts the main scanning direction of the back side image data. This is because in this embodiment, the reading unit 109A and the reading unit 109B have the same configuration, and the main scanning direction of the image read by the reading unit 109B is reversed with respect to the image read by the reading unit 109A. . The back side image data processed by the image inversion circuit 210 is stored in the image memory 205. That is, the image scale 205 functions as a first storage section.

FIG. 3 is an explanatory diagram of the acquisition timing of front side image data and back side image data stored in the image memory 205. After the conveyance of the original 101 is started at time t0, the detection sensor 113 detects the leading edge of the original 101 at time t1. The CPU 203 determines a time t2 before the document 101 reaches the reading position A based on the time t1, for example, based on the conveyance speed at which the document 101 is conveyed. Then, the CPU 203 stores the front surface image data output by the reading unit 109A in the image memory 205 for a predetermined period from time t2. Note that the predetermined period is at least a period until the rear end of the document 101 passes through the reading position A. This predetermined period is determined based on the conveyance speed of the document 101. Similarly, CPU 203 determines time t3 before document 101 reaches reading position B based on time t1. Then, the CPU 203 stores the back side image data output by the reading unit 109B in the image memory 205 for a predetermined period from time t3. Note that the CPU 203 may start reading by the reading unit 109A at time t2 and store the surface image data in the image memory 205, or may start reading the surface image data by the reading unit 109A from before time t2. may be stored in the image memory 205. Further, the CPU 203 may start reading by the reading unit 109B at time t3 and store the back side image data in the image memory 205, or the back side image data of the reading unit 109B that has been reading since before time t3. may be stored in the image memory 205. In the following description, the image indicated by the front image data is also referred to as the front image, and the image indicated by the back image data is also referred to as the back image.

As shown in FIG. 2, the surface image data output from the shading circuit 204A is also input to the edge detection unit 206. Further, back side image data output from the image inversion circuit 210 is also input to the edge detection section 206. Correction of the front side image data will be described below, but the back side image data is also corrected in the same manner.

FIG. 4 is an explanatory diagram of processing by the edge detection unit 206. FIG. 4 shows an image in which rows of pixels in the main scanning direction obtained by the reading unit 109A at predetermined intervals from time t2 are combined in the sub-scanning direction. As described above, the front surface image data input to the edge detection unit 206 is from time t2 before the leading edge of the document 101 in the transport direction reaches the reading position A. That is, when the reading unit 109A starts reading an image, the guide plate 116 is first read. Thereafter, as the original 101 is conveyed, the image of the original 101 is read. That is, the front surface image data input to the edge detection unit 206 includes image data indicating the guide plate 116 and image data indicating the leading edge side of the document 101.

The edge detection unit 206 executes a binarization process on the surface image data, with a region of nine pixels in total, three pixels in the main scanning direction and three pixels in the sub-scanning direction, as one block. In the following, it is assumed that the number of pixels in the main scanning direction of the reading sections 109A and 109B is 7488, and that the reading sections 109A and 109B perform reading 12000 times during the predetermined period. The pixel position in the main scanning direction is expressed as n (0≦n≦7487), and the pixel position in the sub-scanning direction is expressed as m (0≦m≦11999). Further, the luminance values of nine pixels of one block are expressed as px (x=0 to 8), and the maximum and minimum values thereof are expressed as pmax and pmin.

At a location where all nine pixels are on the guide plate 116 (white) like point A in FIG. 4(A), all nine pixels are white pixels, so the difference between pmax and pmin is a small value. On the other hand, at the boundary between the guide plate 116 (white) and the shadow (gray) on the leading edge of the original 101, as shown at point B in FIG. 4A, white pixels and gray pixels coexist among the nine pixels. Therefore, the difference between pmax and pmin becomes large. Therefore, if the difference between pmax and pmin is larger than a predetermined threshold value pth, it is determined that there is a pixel (hereinafter referred to as a candidate pixel) that is a candidate for a shadow caused by the edge of the leading edge of the document 101 in the block. I can do it. In this embodiment, if the difference between pmax and pmin within a block is larger than a predetermined threshold pth, the central pixel (pixel at coordinates (n, m)) of the block is determined to be a candidate pixel. The edge detection unit 206 performs this determination process for each of n and m except n=0, n=7487, m=0, and m=11999. Note that in this embodiment, one scale on the x-axis and the y-axis corresponds to the distance between the center positions of two adjacent pixels.

FIG. 4(A) shows an image represented by 8-bit image data (luminance level: 0 to 255), and FIG. 4(B) shows the image data of the image in FIG. This is an image represented by the converted image data. White in FIG. 4B indicates pixels that are determined to be shadow candidates caused by the edge of the leading edge of the document 101 through the above processing. Among the plurality of candidate pixels shown in FIG. 4(B), the column of candidate pixels in the main scanning direction that is the most distal in the sub-scanning direction (the pixel column in the main scanning direction that is determined to be a candidate pixel first in the sub-scanning direction) ) is determined to be a shadow caused by the edge of the document 101 on the leading edge side.

As shown in FIG. 2, the binarized data output by the edge detection section 206 is input to the document information determination section 207. FIG. 5 shows an image represented by the binarized data input to the document information determination unit 207. The image indicated by the binarized data input to the document information determination unit 207 is an image in the range indicated by the dotted line in FIG. 5, and includes the document 101. The range of this dotted line is n=0 to 7487 and m=0 to 11999. Note that the shaded area shown in FIG. 5 indicates a shadow caused by the original.

The document information determination unit 207 determines front side document information (hereinafter referred to as front side document information) based on the input binary data. Further, the document information determination unit 207 determines the distance (width) W in the main scanning direction between the two leading edge side corners of the shadow caused by the document 101. Then, the document information determination unit 207 outputs the front side document information and the width W to the CPU 203. Here, the front side document information is information including the position and angle of the document in the front side image. Note that the position of the original 101 is the position (x0, y0) of the first position of the original 101 within the front surface image. In this embodiment, the first position is one of the two corners on the leading edge side of the shadow caused by the document 101 (the left side in FIG. 5). Further, the angle of the document 101 is the angle of a predetermined side of the document 101 in the front surface image with respect to the reference direction of the front surface image. In this embodiment, the predetermined side is a shadow caused by the edge on the leading edge side of the document 101, and the reference direction is the main scanning direction (predetermined direction). That is, the angle of the original 101 is θ1 in FIG. Note that if the shadow caused by the leading edge of the original 101 is tilted upstream from the position (x0, y0) in the transport direction, the angle θ1 takes a negative value, and the shadow created by the leading edge of the original 101 is tilted upstream from the position (x0, y0). When tilting downstream from the position (x0, y0), the angle θ1 assumes a positive value.

The CPU 203 outputs the front side document information, that is, the position (x0, y0) and the angle θ1 to the correction unit 208.

The correction unit 208 reads the front surface image data stored in the image memory based on the position (x0, y0) and the angle θ1 and outputs it to the system controller 151. Specifically, the correction unit 208 reads the image data along a direction parallel to the shadow created by the edge of the leading edge of the original document 101, starting from the reading start position (x1, y1). Note that the position (x1, y1) is expressed by the following equation.
x1=x0+Δx (1)
y1=y0+Δy (2)

Here, Δx is a value corresponding to the width of the shadow produced at the left end of the surface image, and Δy is a value corresponding to the width of the shadow produced at the tip of the surface image. Δx and Δy are, for example, values calculated from the average value of the left end shadow and the leading edge shadow included in image data obtained when a plain paper document is read multiple times, and are stored in advance in the nonvolatile memory 209. ing.

When the correction unit 208 reads an amount corresponding to the width W from the position (x1, y1) along the direction parallel to the shadow, the correction unit 208 reads an amount corresponding to the width W from the position (x2, y2) along the direction parallel to the shadow. Read only the amount. Note that x2 and y2 are expressed, for example, by the following formula.
x2=x1-tanθ1 (3)
y2=y1+1 (4)

Note that in this embodiment, x2 and y2 are determined based on equations (3) and (4), but this is not the only option.

The correction unit 208 reads the front side image data stored in the image memory up to the trailing edge of the document as described above. That is, the correction section 208 functions as a reading section.

FIG. 6 is a diagram showing an image read out by the correction unit 208. As shown in FIG. 6, the image data is read in an amount corresponding to the width W along the direction parallel to the shadow, so that the shadow caused by the leading edge of the document becomes parallel to the main scanning direction. Further, by reading the image data from the position (x1, y1), the shadow area on the leading edge side and the left edge side of the document in the image data is reduced. Note that similar processing is also performed on the back side image data.

In this way, by reading the image data from the position (x1, y1) that is shifted by Δx and Δy from one of the two corners on the leading edge side of the shadow caused by the original, the leading edge side of the original in the image data is read out. and the leftmost shadow area are reduced.

The system controller 151 cuts out an image area to be printed from the image data output from the correction unit 208. Specifically, for example, the system controller 151 adjusts the position (0, 0) of the image data shown in FIG. Cut out the image data based on. More specifically, for example, if the document shown in FIG. 6 is A4 size and the size of the recording medium set by the user using the operation unit 202 is A4 size, the system controller 151 may It is possible to crop the image of the document excluding shadows and trailing edge shadows. The system controller 151 controls the image printing apparatus 301 to perform printing based on the cropped image data. That is, the system controller 151 functions as an external device. Note that external devices include not only the system controller 151 provided in the image forming apparatus 100 but also smartphones, tablets, PCs, and the like.

FIG. 7 is a flowchart of image reading processing according to this embodiment. The processing of the flowchart shown in FIG. 7 is executed by the controller 200.

When an instruction to start reading the original is input, the controller 200 starts feeding and transporting the original 101 on the tray 102 in S10.

In S11, the controller 200 waits until the detection sensor 113 detects the original. When the detection sensor 113 detects the document, the controller 200 determines the times t2 and t3 described in FIG. 3.

Then, the controller 200 starts storing the front surface image data in the image memory 205 from S12, which is time t2. Note that in S12, output of the surface image data to the edge detection unit 206 is also started. The edge detection unit 206 performs detection processing to detect a shadow caused by the leading edge of the document.

Then, in S13, the document information determining unit 207 determines the front side document information based on the leading edge detection result by the edge detecting unit 206.

When the document information determination unit 207 completes the determination of the front side document information, the correction unit 208 starts reading out the front side image data stored in the image memory 205 in S14.

In S15, the controller 200 waits until the correction unit 208 outputs the front surface image data stored in the image memory 205.

When the correction unit 208 outputs the corrected image data, the controller 200 determines in S16 whether the next document whose image is to be read is on the tray 102. If there is a next document, the controller 200 repeats the process from S10. On the other hand, if there is no next document, the controller 200 ends the process of FIG.

As described above, in the present embodiment, the correction unit 208 corrects the shadow from the position (x1, y1) that is shifted by Δx and Δy from one of the two corners on the leading edge side of the shadow caused by the document. Image data is read out in an amount corresponding to the width W along the parallel direction. As a result, the inclination of the image of the document with respect to the main scanning direction is reduced, and the shadow area on the leading edge side and the left edge of the document in the image data is reduced. That is, it is possible to suppress deterioration in the quality of the read image.

Furthermore, the system controller 151 can cut out the image based on a position that does not include the leading edge and left edge of the document. As a result, the image printing apparatus 301 can print an image that does not include shadows caused by the original. That is, it is possible to suppress deterioration in the quality of the formed image.

Note that in the present embodiment, the document information determination unit 207 determines the inclination angle θ1 of the shadow caused by the leading edge side of the document 101 with respect to the main scanning direction, but this is not the case. For example, the document information determination unit 207 may be configured to determine the inclination angle θ2 of the shadow caused by the side edge (for example, the left edge) of the document 101 with respect to the sub-scanning direction. The correction unit 208 reads image data based on the angle θ2.

Note that in this embodiment, the correction unit 208 reads the image data so that one corner of the two corners on the leading edge side of the image of the document approaches the reference position (0,0). However, this is not the case. For example, the correction unit 208 may read the image data so that the other corner (on the right side in FIG. 5) of the two corners on the leading edge side of the document approaches the reference position (7487, 0). . As a result, the shadow areas on the leading edge side and the right edge side of the document in the image data are reduced. In such a configuration, the system controller 151 adjusts the position of the image data output from the correction unit 208, as shown in FIG. Cut out the image data based on (7487, 0).

Further, for example, the correction unit 208 may translate the image data so that the center position of the leading edge side of the document in the main scanning direction approaches the reference position (3743, 0). As a result, the shadow on the leading edge side of the document in the image data is reduced. In such a configuration, the system controller 151 adjusts the position of the image data output from the correction unit 208, as shown in FIG. Cut out the image data based on (3743, 0). Specifically, the system controller 151 cuts out the image data in the main scanning direction so that the left and right lengths are symmetrical based on the x coordinate 3743, and cuts out the image data in the sub-scanning direction so that the left and right lengths are symmetrical. Cut out the image data using the y coordinate of 0 as a reference.

Note that in this embodiment, the correction unit 208 sets the position and reading direction from which to start reading out the image data stored in the image memory 205, and reads out the image data based on the set position and direction. However, it is not limited to this. For example, the correction unit 208 may be configured to correct the image data by rotating and translating the image of the document represented by the phase data through transformation such as affine transformation. Specifically, for example, the correction unit 208 rotates the original image so that the angle θ1 becomes smaller, and rotates the original image so that the position (x1, y1) becomes the reference position (0, 0). It may be configured to move in parallel.

The image printing apparatus 301 may have the configuration of the edge detection unit 206, document information determination unit 207, correction unit 208, etc. in this embodiment.

[Second embodiment]
Descriptions of parts of the image forming apparatus 100 that are similar to those in the first embodiment will be omitted.

The width of the shadow caused by a document varies depending on the thickness of the document. For example, the width of the shadow caused by thick paper is greater than the width of the shadow caused by plain paper, and the width of the shadow caused by plain paper is greater than the width of the shadow caused by thin paper. In this embodiment, the image reading device 200 sets the correction values Δx and Δy according to the type (for example, basis weight) of the document to be transported. Note that the type of document to be transported is set by the user from the operation unit 202.

FIG. 8 is a diagram showing correction values Δx and Δy for thin paper, plain paper, and thick paper. Note that the correction values Δx and Δy for thin paper are values calculated from the average value of the left end shadow and the leading edge shadow included in the image data obtained when the thin paper document is read multiple times, and are stored in the nonvolatile memory 209. is stored in advance. In addition, the correction values Δx and Δy for plain paper are values calculated from the average value of the left edge shadow and tip shadow included in the image data obtained when a plain paper document is read multiple times, and are nonvolatile. It is stored in memory 209 in advance. Further, the correction values Δx and Δy for thick paper are values calculated from the average value of the left edge shadow and the leading edge shadow included in the image data obtained when reading the thick paper document multiple times, and is stored in advance.

The correction unit 208 sets correction values Δx and Δy according to the type of document set by the user, and reads image data based on the set correction values Δx and Δy.

As described above, in this embodiment, image data is read out based on the correction values Δx and Δy set according to the type of document. As a result, the inclination of the image of the original with respect to the main scanning direction is reduced, and the shadow area on the leading edge and left end of the original in the image data is reduced, that is, deterioration in the quality of the read image is suppressed. be able to.

Furthermore, the system controller 151 can cut out the image based on a position that does not include the leading edge and left edge of the document. As a result, the image printing apparatus 301 can print an image that does not include shadows caused by the original. That is, it is possible to suppress deterioration in the quality of the formed image.

[Third embodiment]
Descriptions of parts of the image forming apparatus 100 that are similar to those in the first embodiment will be omitted.

In this embodiment, the document information determination unit 207 detects the width of the leading edge shadow and left edge shadow caused by the document based on the input binary data. Then, the document information determination unit 207 outputs information regarding the width of the detected shadow to the CPU 203.

The CPU 203 outputs front side document information and information regarding the width of the shadow to the correction unit 208. The correction unit 208 reads image data stored in the image memory based on the input information.

With this configuration, the inclination of the image of the document with respect to the main scanning direction is reduced, and the shadow area on the leading edge side and the left edge of the document in the image data is reduced. That is, it is possible to suppress deterioration in the quality of the read image.

Furthermore, the system controller 151 can cut out the image based on a position that does not include the leading edge and left edge of the document. As a result, the image printing apparatus 301 can print an image that does not include shadows caused by the original. That is, it is possible to suppress deterioration in the quality of the formed image.

Note that in the first embodiment, the second embodiment, and the third embodiment, the correction unit 208 read out the image data based on the values Δx and Δy, but the present invention is not limited to this. For example, the correction unit 208 may set y1 based on the value Δy, and set x1 based on the detected width of the left end. Further, for example, the correction unit 208 may set x1 based on the value Δx, and set y1 based on the detected width of the tip.

102 Tray 103 Pickup roller 104, 105 Separation roller 106 Conveyance roller 107 Lead roller 110 LED
111 Image sensor 116 Guide plate 200 Controller 203 CPU
206 Edge detection section 207 Original information judgment section 208 Correction section

Claims (4)

a light source that emits light;
a reading unit that reads an image of the original by receiving reflected light from the original that passes through a reading position;
an opposing member that is provided on the opposite side of the light source with respect to a conveyance path along which the document is conveyed, and that faces the document passing through the reading position;
In the read image obtained by the reading unit, a shadow area formed on the opposing member by the light emitted from the light source and the edge of the leading edge of the original in the conveyance direction in which the original is conveyed, and a shadow area of the opposing member. determining means for determining an inclination angle of the tip end side with respect to a width direction perpendicular to the conveyance direction, based on a boundary with the region;
Rotation correction is performed so that the tilt angle is small, and the position is a predetermined length away from the boundary in a direction from the leading edge of the original to the trailing edge of the original. output means for outputting an image read out in the main scanning direction from the read image stored in the memory ;
An image reading device comprising: The output means is configured to undergo rotational correction so that the inclination angle is small, and is spaced a predetermined length from the boundary in a direction from a leading edge of the document to a trailing edge of the document. An image obtained by reading out the read image stored in the memory in the main scanning direction with reference to a position separated by a second predetermined length from one end of the document in a direction corresponding to the width direction is output. The image reading device according to claim 1. The image reading device according to claim 1 or 2 , wherein the opposing member is white. An image reading device according to any one of claims 1 to 3 ;
an image forming section that forms an image on a recording medium based on the image output from the output means;
An image forming apparatus comprising:

Images