JP2011193190A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new image reader capable of constantly acquiring a copied image without color shift and distortion even when inclination is generated in an original during reading. <P>SOLUTION: In the image reader of a sheet through system, variable control is performed to conveyance speed of the original and a reading position according to an inclination angle θ of the original at the reading position. The inclination angle θ of the original is derived based on an incident position of specularly reflected light of light emitted onto the original at the reading position. Width of the original to be read for every one line period is held constant and the color shift and the deviation of the copied image are prevented by defining a correction coefficient [cosθ] using the derived inclination angle θ and conveying the original at corrected speed to be calculated by multiplying default conveyance speed of the original by the correction coefficient [cosθ]. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, and more particularly, to an image reading apparatus capable of acquiring a copy image without color misregistration or distortion.

  The document reading method in a copying machine or a flat head scanner device includes a pressure plate method that moves an optical device while the document is fixed and reads an image, and a sheet that conveys the document while the optical device is fixed and reads an image. In the sheet-through method, the curling or flapping of the document may occur due to a change in the load on the document when the roller is pulled out or contacted with a roller, an edge, or the like. .

  On the other hand, as the unit has become smaller and faster in recent years, the document transport path has become shorter and the entry angle to the document reading position tends to be steeper. Color deviation and distortion of the copy image due to curling and flickering are likely to occur.

  In this regard, Japanese Patent Application Laid-Open No. 2003-333275 (Patent Document 1) switches the original reading method from the original flow reading method to the original fixed reading method when the speed unevenness occurs in the conveyance speed of the feeding belt. Thus, a configuration for preventing the image from expanding and contracting in the sub-scanning direction is disclosed. Japanese Patent Laid-Open No. 2003-259085 (Patent Document 2) discloses a conveyance speed at which the original is not vibrated when the reading position reaches the speed change target area while conveying the original at a standard speed in the normal area. Disclosed is a configuration in which the color deviation does not occur in the read image by decelerating to a low speed. However, Patent Documents 1 and 2 sacrifice the image reading efficiency in order to ensure the quality of the copied image.

  The present invention has been made in view of the above-described problems in the prior art, and the present invention always obtains a copy image without color misalignment or distortion even when the document is tilted during reading. It is an object of the present invention to provide a novel image reading apparatus capable of performing the above.

  As a result of earnestly examining a new image reading apparatus that can always obtain a copy image without color misalignment or distortion even when the document is inclined during reading, the present inventor has found that at the reading position. The inventors arrived at the present invention by conceiving a configuration in which the width of the original read per line cycle is kept constant by variably controlling the relative speed between the original and the reading position in accordance with the inclination angle of the original.

  That is, according to the present invention, an image reading apparatus that conveys an original along a reading surface and reads an image of the original at a fixed reading position, wherein the original at the reading position is inclined with respect to the reading surface. A document inclination angle deriving section for deriving an angle θ, a correction speed calculating section for deriving a correction speed by multiplying an initial set value of the document conveyance speed by a correction coefficient derived based on the inclination angle θ, and the correction An image reading apparatus is provided that includes conveyance speed control means for controlling the original conveyance means based on speed.

1 is a diagram illustrating an image reading apparatus according to a first embodiment (sheet through system). FIG. FIG. 3 is a conceptual diagram illustrating the behavior of a document in a document pressing unit. The sample figure which shows the distortion of an image. FIG. 3 is a functional block diagram of a document conveyance speed correction unit in the present embodiment. FIG. 4 is a conceptual diagram for explaining a method of calculating a document inclination angle θ. The conceptual diagram for demonstrating a correction coefficient. The figure which shows the image reading apparatus of 2nd Embodiment (pressure plate system). The figure which shows the image reading apparatus of 3rd Embodiment. FIG. 3 is a flowchart illustrating an operation of the image reading apparatus according to the present embodiment.

  Hereinafter, although this invention is demonstrated with embodiment, this invention is not limited to embodiment mentioned later. In the drawings referred to below, the same reference numerals are used for common elements, and the description thereof is omitted as appropriate.

  The image reading apparatus of the present invention can be mounted on a facsimile machine, a flat head scanner device, a copying machine, or a multifunction machine (MFP) having a plurality of these functions. In the following description, the image reading apparatus of the present invention will be described based on the case where it is installed in a copying machine.

  FIG. 1 shows an image reading apparatus 100 according to a first embodiment of the present invention mounted on a sheet-through type copying machine 200. The image reading apparatus 100 includes a document transport unit 10, a scanning optical system 20, and a document transport speed correction unit 30.

  The document conveying means 10 includes a sheet feeding roller 11, a sheet feeding roller 12, a conveying roller 13, a sheet discharge roller 14, and a sheet feeding motor 15, and more preferably includes a document pressing unit 16 and a document tray 17. ing. The original placed on the original tray 17 is guided to the paper supply roller 12 by the paper supply roller 11 and then sent to the reading position P on the contact glass 202 under the original pressing portion 16 by the transport roller 13. The reading position P is defined as a straight line extending in the main scanning direction (direction perpendicular to the paper surface). Each of the rollers is rotationally driven by a paper feed motor 15 connected via a gear and a belt, and the rollers cooperate to sequentially convey a document. The document that has passed the reading position P is discharged to the outside by the discharge roller 14.

  The scanning optical system 20 includes a scanning light source 21 configured by an Xe lamp, a cold cathode tube, an LED, and the like, a reflector 22 disposed at a position facing the scanning light source 21, mirrors 23 to 25, and a lens 26. It is configured to include. In the present embodiment, the irradiation light from the scanning light source 21 is directly incident on the reading position P on the contact glass 202, and the reflected light from the reflector 22 is incident on the reading position P. The incident light is reflected on the surface of the document conveyed through the reading position P. A part of the reflected light (scattered light) is reflected through the mirror 23, the mirror 24, and the mirror 25, then collected by the lens 26, and enters the light receiving element 27. The light incident on the light receiving element 27 is photoelectrically converted, accumulated for a predetermined time, and then output as an optical signal. The accumulation time for one line coincides with the line period. A CPU (not shown) generates and stores image data for each line based on the optical signal output from the light receiving element 27 to generate a copy image. In the present embodiment, the scanning optical system 20 can be configured by a line sensor. In the following description, the scanning optical system 20 including the light receiving element 27 is referred to as the line sensor 20.

  Here, the document pressing unit 16 in the document transporting unit 10 presses the document against the reading position P on the contact glass 202 serving as a reading surface with an urging force of a constant pressure, thereby suppressing the fluttering of the document. However, when the vicinity of the leading edge and the trailing edge of the original passes through the reading position P, the original is sufficiently separated from the contact glass. Can not be pressed. This point will be described with reference to FIG.

  As shown in FIG. 2A, when the leading edge of the document S is sent to the document pressing unit 16, the document S is gripped only by the transport roller 13, so that the reading position P on the contact glass 202 is reached. On the other hand, the document is not sufficiently pressed, and the document is lifted. Thereafter, as shown in FIG. 2B, while the leading edge of the document S is held by the paper discharge roller 14 and the paper feed roller 14 cooperates with the paper discharge roller 14 to execute paper feeding, the document Since S is pressed firmly against the reading position P, the document is unlikely to float. Further, after that, as shown in FIG. 2C, when the trailing edge of the document S is removed from the conveying roller 13, the document S is held only by the paper discharge roller 14, and the reading position P is not moved. The document is not pressed sufficiently, and the document is similarly lifted.

  In the present embodiment, while the line sensor 20 scans in the main scanning direction (direction perpendicular to the paper surface) with a predetermined line cycle, the document S is conveyed on the reading position P to the right side of the paper surface at a predetermined speed. Here, as shown in FIG. 2B, when the document S is conveyed while maintaining a state parallel to the contact glass 202, the width of the document S read in one line cycle is one line. This is equal to the transport distance of the document S per cycle. However, as shown in FIGS. 2A and 2C, when the document S has a predetermined inclination angle θ with respect to the contact glass 202, the width of the document S read in one line cycle is as follows. This is larger than the transport distance of the document S per one line cycle. That is, if the transport distance of the document S per line cycle = A, the width of the document S read in one line cycle = A / cos θ, and if the document S is inclined at an angle θ, it should be read in one line cycle. A wide range is read in the sub-scanning direction (paper feeding direction) with respect to the original document area.

  A copy image formed when the document S is read with an inclination with respect to the contact glass 202 is distorted compared to a copy image formed when the document S is read with no inclination. FIG. 3 shows a copy image formed when an obliquely drawn document is read with a tilt and a copy image formed when read with no tilt. As shown in FIG. 3, when a document is read with an inclination, the document area read by the light receiving element 27 is enlarged by one line, so that the oblique line of the formed copy image is bent. In this regard, the image reading apparatus 100 according to the present embodiment includes a document conveyance speed correction unit 30 that is a unit for forming a copy image without color misregistration or distortion.

  FIG. 4 is a functional block diagram of the document conveyance speed correction unit 30 in the present embodiment. The document conveyance speed correction unit 30 includes a document inclination angle deriving unit 35, a correction speed calculation unit 38, and a conveyance speed control unit 39. The document inclination angle deriving unit 35 includes a correction light source 32 and a position detection unit 34. And a document inclination angle calculation unit 36. The correction light source 32 includes a light source having high linearity such as an LED and an appropriate optical system (not shown), and reads a spot light for detecting an inclination angle θ of the document S with respect to the contact glass 202 at a reading position P. Irradiate toward. On the other hand, the position detection means 34 receives spot light that collides with the document S and is regularly reflected, and detects the incident position of the spot light (the position of the center of gravity of the spot light), preferably by a PSD element. Can be configured. Hereinafter, the position detector 34 is referred to as a PSD element 34. As shown in FIG. 4, when the document S is not inclined with respect to the contact glass 202 at the reading position P (document S indicated by a broken line in the figure) and when it is inclined (document S indicated by a thick solid line in the figure). The position information detected by the PSD element 34 is different. In the present embodiment, using the position information of the incident light detected by the PSD element 34, the document tilt angle calculation unit 36 calculates the tilt angle θ of the document S at the reading position P with respect to the contact glass 202.

FIG. 5 is a conceptual diagram for explaining a method of calculating the tilt angle θ. In FIG. 5, at the reading position P, the incident position of the regular reflection light L1 of the document S that is not inclined with respect to the contact glass 202 is S1, and the regular reflection of the document S that is inclined with respect to the contact glass 202 with an inclination angle θ. The incident position of the light L2 is S2, and a line passing through the reading position P and extending in the vertical direction is H. Here, if the angle formed between the line connecting S1 and P and the line H is θ1, and the angle formed between the line connecting S2 and P and the line H is θ2, the inclination angle θ of the document S is θ = θ1−θ2. Here, the length of the perpendicular line from S1 to the line H is Y, the length of the perpendicular line from S2 to the line H is X, and the intersection of the plane including the light receiving surface of the PSD element 34 and the line H and P When the separation distance is Z, θ1 = Tan ⁻¹ (Z / Y) and θ2 = Tan ⁻¹ (Z / X).

  Here, the document inclination angle calculation unit 36 calculates X from the position information of S2 detected by the PSD element 34, and uses this to obtain θ2. On the other hand, the document inclination angle calculation unit 36 stores θ1 as a reference value (θ1 is calculated from preset Z and Y), and the inclination angle of the document S is subtracted from θ2 obtained from the reference value θ1. θ (= θ1−θ2) is obtained.

The correction speed calculation unit 38 receives the calculation result of the document tilt angle calculation unit 36 and calculates a correction speed (V) for transporting the document S. As shown in FIG. 6A, when the paper feed amount per line period = A at the default transport speed (V _{θ = 0} ), the document S at the reading position P is inclined with respect to the contact glass 202. If not, the width of the document S read in one line cycle is equal to the paper feed amount (= A). On the other hand, when the document S is inclined with respect to the contact glass 202 at an inclination angle θ, assuming that the paper feed amount per line cycle = A, the document S read in one line as shown in FIG. Is A / cos θ, which is larger than when the original S is not tilted, and this causes color deviation and distortion of the copied image.

  Therefore, the correction speed calculation unit 38 defines “cos θ” as a correction coefficient using the document inclination angle θ calculated by the document inclination angle calculation unit 36, and obtains the correction speed (V) by the following formula 1.

  When the original S is conveyed at the correction speed (V), as shown in FIG. 6B, the paper feed amount per line cycle = A × cos θ, and the width of the original read per line = A. Become. That is, by sequentially correcting the conveyance speed using “cos θ” as a correction coefficient, the width of the document S read per line is always kept constant regardless of the state of the document S at the reading position P. Color shift and distortion of copied images are prevented.

  The transport speed control unit 39 performs speed control of the transport unit so as to transport the document S at the correction speed (V) obtained by the correction speed calculation unit 38. In the present embodiment, the control of the rotation speed of the paper feed motor 15 corresponds to this. When the paper feed motor 15 is configured by a DC motor, the conveyance speed control unit 39 sets the correction speed (V) as a target speed for the motor driver 19, and the motor driver 19 sets the target speed based on the target speed. The paper feed motor 15 is feedback controlled. When the paper feed motor 15 is configured by a stepping motor, the transport speed control unit 39 generates a drive signal for realizing the correction speed (V), and the paper feed motor 15 is transported by the transport speed control unit 39. Rotation drive based on the drive signal supplied from

  In the present embodiment, the processing load of the CPU can be reduced by synchronizing the execution timing of the arithmetic processing for deriving the correction speed (V) with the line period. Further, in the present embodiment, the processing load of the CPU can be reduced by limiting the target area for correcting the conveyance speed in the document. For example, in the sheet-through method, the document is inclined mainly in the leading edge region and the trailing edge region of the document, so that the conveyance speed correction process is executed only during the period in which the corresponding region width passes the reading position P. Then, control is performed so that the correction process is not executed during a period in which the other region passes the reading position P.

  In this case, the leading edge area of the document is at the reading position P until the first time elapses (or until the first number of lines is scanned) after the original is first detected at the reading position P. After the first time has passed (or after scanning the first number of lines) and until the second time has passed (or the second number of lines is Until the scanning position), the correction processing is interrupted because it is determined that there is no correction target area at the reading position P, and the document is started after the second time has elapsed (or after the second number of lines is scanned). Until no longer detected, it may be determined that the trailing edge area of the document exists at the reading position P and the correction process may be executed.

  As described above, the first embodiment in which the image reading apparatus of the present invention is mounted on a sheet-through type copying machine has been described. However, the image reading apparatus of the present invention can also be mounted on a pressure plate type copying machine. As shown in FIG. 7, when the bookbinding document 56 is read by the pressure plate method, the vicinity of the binding opening of the document is lifted from the contact glass 302 of the copying machine 300. If the original is read at a constant speed in this state, the read width per line becomes larger in the floating area than in other areas, resulting in color shift and distortion in the copied image.

  FIG. 7 shows an image reading apparatus 400 mounted on a pressure plate type copying machine 300 according to the second embodiment of the present invention. The image reading apparatus 400 includes a carriage 52 and a carriage transfer motor 54 for transferring the carriage 52 in the sub-scanning direction along the back surface of the contact glass 302 of the copying machine 300. The carriage 52 is mounted with a carriage transfer speed correction unit 50 and a line sensor 20 (not shown) having the same configuration as the document conveyance speed correction unit 30 described with reference to FIG. Note that reference numeral 39 in FIG. 7 should be read as the carriage transfer speed control unit. In the pressure plate type copying machine 300, the line sensor 20 (reading position) is moved with respect to the bookbinding document 56 placed on the contact glass 302 by moving the carriage 52 along the contact glass 302 (reading surface). To read the image.

  In the image reading apparatus 400, the carriage transfer speed correction unit 50 calculates the correction coefficient = cos θ by the same method as described above for the first embodiment, and based on this, the correction speed (V) of the carriage transfer motor 54 is calculated. Define The correction speed (V) can be obtained by the following equation 2.

  The carriage transfer speed correction unit 50 drives and controls a carriage transfer motor so as to transfer the carriage 52 in the sub-scanning direction at a correction speed (V). As shown in FIGS. 7A to 7C, the correction speed (V) is sequentially changed according to the inclination of the original at the reading position P, so that the width of the original read per line is always constant. Thus, it is possible to obtain a copy image without color misalignment or distortion near the binding opening of the bookbinding document 56.

  In the above-described embodiment, the aspect of variably controlling the conveyance speed with respect to the original or the movement speed of the reading position has been described. That is, in the above-described embodiment, the reading width of the document per line is kept constant by sequentially correcting the reading position (line sensor 20) and the relative speed of the document according to the inclination angle θ of the document. Although shown, the present invention is not limited to the above-described embodiment. By correcting the line period by sequentially correcting the line period according to the inclination angle θ of the original, the original reading width per line is corrected. Including a configuration that keeps constant.

  FIG. 8A shows an image reading apparatus 500 according to the third embodiment of the present invention. The image reading apparatus 500 includes the same document inclination angle deriving unit 35 as the first and second embodiments, a correction accumulation time calculating unit 62, a line cycle control unit 63, and a line sensor 20. Yes. Note that the copying machine on which the image reading apparatus 500 is mounted may be either a sheet-through method or a pressure plate method.

  In the image reading apparatus 500, the correction accumulation time calculation unit 62 defines the correction coefficient = cos θ using the output (tilt angle θ) from the document tilt angle deriving unit 35, and based on this, the light receiving element of the line sensor 20. The correction accumulation time (T) is calculated. In this case, the correction accumulation time (T) can be obtained by the following equation 3.

  The line cycle control unit 63 corrects the line cycle so that the accumulation time of the light receiving elements of the line sensor 20 becomes the correction accumulation time (T). FIG. 8B shows a mode in which the line cycle (= accumulation time) is changed. The line sensor driver 64 outputs the pixel data acquired from the line sensor 20 in accordance with the corrected line cycle. In the present embodiment, it is possible to prevent color deviation and distortion of an image by sequentially correcting the line period (that is, the accumulation time of the light receiving elements of the line sensor 20) according to the inclination angle θ of the document.

  FIG. 9A is an operation flowchart of the image reading apparatus 100 according to the first embodiment. When the process is started, it is determined in step 1001 whether or not a document is detected. If a document is not detected (S1001, No), the process is terminated as it is. This determination can be made based on the presence or absence of output from the PSD element 34. If a document is detected (S1001, Yes), the process proceeds to step 1002, and it is determined whether or not the region on the document reading position P is a correction target region. If it is not the correction target area (S1002, No), the process is terminated as it is. If it is the correction target area (S1002, Yes), the document tilt angle calculation process is executed in step 1003. In the document tilt angle calculation process, the document tilt angle θ is derived based on the output from the PSD element 34, and the process proceeds to step 1004.

  In step 1004, a correction speed calculation process is executed. In the correction speed calculation process, a correction coefficient [cos θ] is defined from the document inclination angle θ, the correction speed is calculated by multiplying the initial setting value of the document conveyance speed by the correction coefficient [cos θ], and the process proceeds to step 1005. . In step 1005, a conveyance speed control process is executed. In the conveyance speed control process, the rotation speed of the paper feed motor is controlled so that the document is conveyed at the calculated correction speed. In the present embodiment, the processing flow described above is repeated in synchronization with the line cycle. Although the operation flow of the first embodiment has been described above, the operation flow of the image reading apparatus 400 of the second embodiment is substantially equivalent to this, and thus further description is omitted.

  FIG. 9B is an operation flowchart of the image reading apparatus 500 according to the third embodiment. From step 2001 to 2003, the same processing as described with reference to FIG. Subsequently, in step 2004, a correction accumulation time calculation process is executed. In the correction accumulation time calculation process, a correction coefficient [cos θ] is defined from the document inclination angle θ, and the correction accumulation time is calculated by multiplying the initial setting value of the accumulation time of the light receiving element by the correction coefficient [cos θ]. Proceed to 2005. In step 2005, a line cycle control process is executed. In the line cycle control process, the light detection signal from the line sensor is converted into pixel data and output at a line cycle corresponding to the calculated correction accumulation time.

  The functions of the above-described embodiments are as follows: assembly language, C, Visual C, C ++, Visual C ++, Java (registered trademark), Java (registered trademark) Beans, Java (registered trademark) Applet, Java (registered trademark) Script, Perl , Ruby, and the like, which can be realized by a device-executable program written in a legacy programming language, an object-oriented programming language, or the like, and can be stored and distributed in a device-readable recording medium.

  As described above, the present invention has been described with the embodiment. However, the present invention is not limited to the above-described embodiment, and as long as the operations and effects of the present invention are exhibited within the scope of embodiments that can be considered by those skilled in the art. It is included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Document conveyance means 11 ... Paper feed roller 12 ... Paper feed roller 13 ... Conveyance roller 14 ... Paper discharge roller 15 ... Paper feed motor 16 ... Document press part 17 ... Document tray 18 ... Paper feed motor drive control part 19 ... Motor Driver 20: Scanning optical system (line sensor)
DESCRIPTION OF SYMBOLS 21 ... Scanning light source 22 ... Reflector 23-25 ... Mirror 26 ... Lens 27 ... Light receiving element 30 ... Original conveyance speed correction part 32 ... Correction light source 34 ... Position detection means (PSD element)
35: Document tilt angle deriving unit 36 ... Document tilt angle calculating unit 38 ... Correction speed calculating unit 39 ... Conveying speed control unit 50 ... Carriage transfer speed correcting unit 52 ... Carriage 54 ... Carriage transfer motor 56 ... Bookbinding document 62 ... Correction accumulation time Calculation unit 63 ... Line cycle control unit 64 ... Line sensor driver 100, 400, 500 ... Image reading device 200, 300 ... Copier 202, 302 ... Contact glass

JP 2003-333275 A JP 2003-259085 A

Claims (9)

An image reading apparatus that conveys an original along a reading surface and reads an image of the original at a fixed reading position,
A document inclination angle deriving unit for deriving an inclination angle θ of the document at the reading position with respect to the reading surface;
A correction speed calculation unit for deriving a correction speed by multiplying an initial setting value of the document conveyance speed by a correction coefficient derived based on the inclination angle θ;
A transport speed control means for controlling the transport means of the document based on the correction speed;
Including an image reading apparatus. The document inclination angle deriving unit
A light source for irradiating light on the document at the reading position;
Position detection means for receiving light regularly reflected on the original at the reading position and detecting the incident position of the light;
A document tilt angle calculator that calculates the tilt angle θ based on the incident position;
The image reading apparatus according to claim 1, comprising:   The image reading apparatus according to claim 1, wherein the correction coefficient is cos θ.   The image reading apparatus according to claim 1, wherein the correction speed calculation unit derives the correction speed in synchronization with a line cycle. A correction target area determination unit for determining whether or not the designated area of the document is at the reading position;
The image reading apparatus according to claim 1, wherein the correction speed calculation unit derives the correction speed only when it is determined that the designated area is at the reading position.   6. The conveyance device according to claim 1, wherein the conveyance unit is driven by a stepping motor, and the conveyance speed control unit corrects a cycle of a driving clock of the stepping motor so that the document is conveyed at the correction speed. The image reading apparatus according to one item.   The image reading apparatus according to claim 1, wherein the transport unit is driven by a DC motor, and the transport speed control unit sets the correction speed to a target speed of the DC motor. An image reading apparatus that moves a reading position along a reading surface and reads an image of a document placed on the reading surface,
A document inclination angle deriving unit for deriving an inclination angle θ of the document at the reading position with respect to the reading surface;
A correction speed calculation unit for deriving a correction speed by multiplying an initial set value of the moving speed of the reading position by a correction coefficient derived based on the tilt angle θ;
Reading position movement speed control means for controlling means for moving the reading position based on the correction speed;
Including an image reading apparatus. An image reading apparatus that reads an image of a document on a reading surface at a reading position,
A document inclination angle deriving unit for deriving an inclination angle θ of the document at the reading position with respect to the reading surface;
A correction accumulation time calculation unit for deriving a correction accumulation time by multiplying an initial setting value of the accumulation time of the light receiving element by a correction coefficient derived based on the inclination angle θ;
Line cycle control means for controlling the line cycle based on the correction accumulation time;
Including an image reading apparatus.