JP2009111831A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus for generating image data with high quality. <P>SOLUTION: A CCD line sensor is conveyed to an image reading direction at a fixed speed, and a line start signal specifying a reading timing in a fixed cycle is input to the sensor, and the reading operation of each line is achieved according to the input. Also, when the free capacity of a buffer becomes small, reading is temporarily interrupted, and when prescribed conditions are satisfied, reading is resumed, and the reading resumption position is set prior to resumption as follows. That is, when the absolute value ¾μ¾ of a difference between a reading length as the length of the image reading direction of reading image data from the leading line to the reading completion line and a conveyance quantity of a CCD line sensor from the reading start position corresponding to the leading line to the reading completion line is less than or equal to a threshold, the reading resumption position is set so as to be matched with a reading interruption position, and when the absolute value ¾μ¾ is beyond the threshold, the reading resumption position is set so as to be shifted to a direction where the error ¾μ¾ can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that reads an image line by line by changing a relative position between a reading unit and a reading target.

  2. Description of the Related Art Conventionally, as an image reading device, a reading unit is transported onto a reading target while the reading target (original) is stationary, and during this time, the reading unit performs a reading operation to thereby read image information on the reading target. An ADF (automatic document feeder) type that reads image information of a reading target by conveying a document as a reading target onto the reading unit in a state where the reading unit is fixed and a reading unit is fixed. An image reading apparatus is known.

  In addition, pulse motors and DC motors are known as drive sources for conveying the reading unit and the reading target. Pulse motors are widely used due to the ease of position control and the convenience of control system configuration. However, pulse motors have the disadvantages of greater noise and power consumption during driving than DC motors, and However, there is a drawback that the high-speed scanning is inferior. For this reason, in recent years, image reading apparatuses employing a DC motor as a drive source have been actively developed for the purpose of reducing noise during driving, reducing power consumption, and improving high speed.

  As an image reading apparatus, an image reading apparatus including a CCD line sensor in which a plurality of light receiving elements (photodiodes) are arranged along the line direction is known as a reading unit. In this image reading apparatus, pixel data corresponding to the electric charge accumulated in each light receiving element is generated, and line image data formed by arranging pixel data for one line is generated. Then, the image data corresponding to the reading target is generated by repeatedly executing such an operation for each line.

Specifically, a line start signal that specifies the reading start timing of the line image is input to the reading unit at a fixed period, the reading unit or the document to be read is set as a transfer target, and the transfer target is moved at a constant speed. Then, the line image data of each line is generated by the reading unit, and the line image data for a plurality of lines are combined to generate image data corresponding to the reading target. Note that the reading unit executes a reading operation each time a line start signal is input to generate line image data (see, for example, Patent Document 1).
JP-A-8-228267

  By the way, in an image reading apparatus having a high reading resolution in recent years, a data transfer speed to an external device or an image processing speed after reading such as gamma correction may be slower than an image reading speed.

  In this case, since the buffer for storing the image data output from the reading unit is full before the image reading operation for one original is completed, the conventional image reading apparatus uses a buffer. The temporary reading operation is stopped when the free space becomes less than the threshold, and the reading operation is resumed when the free space of the buffer can be secured to some extent.

  However, when the reading operation is temporarily stopped and restarted, there is a discrepancy between the size of the reading target and the size of the image data corresponding to the reading target due to a deviation between the reading interruption position and the reading restart position. Matching may occur.

  As is well known, in detecting the position of a conveyance target, a rotary encoder that outputs a pulse signal every time the motor that conveys the conveyance target rotates a predetermined amount δ, or a pulse signal is output every time the reading unit moves a predetermined amount δ. Although a linear encoder or the like is used, position information that exceeds the resolution of the encoder cannot be obtained by position detection using the encoder. That is, the position of the conveyance target can be accurately detected only with the accuracy of the distance corresponding to the predetermined amount δ.

  In addition, when a DC motor is used as the drive source, the position control of the conveyance target cannot be realized with high accuracy, and therefore, the input of the line start signal and the movement of the conveyance target are asynchronous. That is, when a DC motor is used as the drive source, the motor cannot be rotated in synchronization with the input of the line start signal, unlike when a pulse motor is used as the drive source.

  For this reason, once the reading is interrupted, the point at which the conveyance target was present when the line start signal corresponding to the line where the reading was interrupted, that is, the correct position for the reading interruption position is not known, and the reading interruption position and the reading resume position In the conventional technique, the image represented by the image data becomes an expanded image or a crushed image with respect to the reading target.

  The present invention has been made in view of these problems, and provides a technique capable of generating high-quality image data even when the reading interruption position and the reading resumption position cannot be accurately matched. Objective.

In the present invention, the above object is achieved by appropriately switching the reading restart position.
An image reading apparatus according to the present invention (Claim 1) includes a reading unit that reads image information to be read, and a conveyance mechanism that conveys either the reading unit or the reading object as a conveyance object by the driving force of a DC motor. And controlling the moving speed of the conveyance target through the conveyance mechanism, moving the conveyance target at a constant speed in the image reading direction, and periodically inputting a line start signal to the reading unit, A read operation in which a reading operation is performed for each line by specifying a reading start timing of the line image, causing the reading unit to generate read image data of each line, and writing the generated read image data to the buffer. Control means.

  The image reading apparatus further includes an interruption determination unit, a stop control unit, an event occurrence signal output unit, a position detection unit, a first reference position setting unit, an offset setting unit, a reading length detection unit, An amount detection unit, a second reference position setting unit, an operation control unit, a backward control unit, and a restart determination unit are provided, and the interruption determination unit determines whether or not the processing by the reading control unit is interrupted.

  When it is determined that the processing by the reading control unit needs to be interrupted, the stop control unit interrupts the processing by the reading control unit. The interruption determination means can be configured to determine whether or not the processing by the reading control means is interrupted based on the free capacity of the buffer.

  The event occurrence signal output means outputs an event occurrence signal every time the conveyance target moves by a predetermined amount, and the position detection means is based on the event occurrence signal input from the event occurrence signal output means. Is detected. As the event generation signal output means, the encoder described above can be used.

  In addition, the first reference position setting means includes a time point TS including a time point TS “a line start signal corresponding to a line for which processing by the reading control means is interrupted by the operation of the stop control means is input to the reading unit”. In the past, at the time TP when the event occurrence signal was last input from the event occurrence signal output means, the position XP detected by the position detection means is set as the reading restart reference position, and the offset setting means sets the time TP. The offset time is set based on the elapsed time from time to time TS. For example, the offset setting means can be configured to set the elapsed time from the time point TP to the time point TS as the offset time.

  On the other hand, the reading length detection means detects the reading length that is the length in the image reading direction of the read image data from the first line where reading is started to the reading completion line where the reading operation by the reading unit is completed at the time TS. Then, the carry amount detection means calculates the length from the position detected by the position detection means at the start of reading of the head line to the position XP detected by the position detection means at time TP from the head line to the read completion line. This is detected as the conveyance amount of the reading unit required to read the line image.

  Further, the second reference position setting unit is configured to detect the position detected by the position detection unit at a time point TP based on an error between the conveyance amount detected by the conveyance amount detection unit and the reading length detected by the reading length detection unit. After the passage of XP and time TP, either one of the positions XF detected by the position detection means at the time TF when the event occurrence signal is first input is selectively set as the reading resume reference position.

The operation control means selectively operates one of the first and second reference position setting means based on the error between the carry amount and the reading length.
In addition, when the processing by the reading control unit is interrupted by the operation of the stop control unit, the reverse control unit sets the first and second reference positions in the direction opposite to the image reading direction through the transport mechanism. It is moved to a position advanced from the reading resumption reference position set by any one of the means, and the resumption determining means determines whether or not the resumption of the processing by the reading control means is necessary during the period when the processing by the reading control means is interrupted. To do.

When the restart determining unit determines that the restart is necessary, the reading control unit again moves the conveyance target moved by the backward control unit in the image reading direction at a constant speed.
In addition, when the reading resumption reference position is set by the first reference position setting unit in advance, the reading control unit sets the offset from the time when the conveyance target reaches the reading resumption reference position based on the detection result of the position detection unit. When the offset time set by the means elapses, the line start signal is input to the reading unit, and thereafter the line start signal is periodically input, so that the position where the conveyance target was present when the offset time elapses. From the reading restart position, the reading unit performs a reading operation, and the process of writing the read image data generated by the reading unit into the buffer is restarted.

  On the other hand, when the reading restart reference position is set by the second reference position setting means, the reading control means inputs a line start signal to the reading unit when the conveyance target reaches the reading restart reference position, and thereafter When the line start signal is inputted, the reading resume reference position set by the second reference position setting means is set as the reading resume position, and the reading unit is caused to execute a reading operation from the reading resume position. The process of writing the generated read image data into the buffer is resumed.

  According to the image reading apparatus of the present invention configured as described above, a point where the conveyance target is present when the offset time has elapsed from the restart reference position set by the first reference position setting unit is set as the reading restart position. Thus, the reading operation can generally be resumed from the reading interruption position.

  However, in this image reading apparatus, since the position of the conveyance target is accurately known only within the range of the position accuracy of the position detection means, the reading interruption position is estimated by the offset time, and the reading operation is performed from the time when the offset time has elapsed. Even if the operation is resumed, the reading operation cannot be resumed from the reading interruption position. That is, even if the conveyance target is controlled at a constant speed, there is an error between the actual speed and the target speed, and this error causes a deviation between the reading interruption position and the reading restart position.

  Therefore, in the image reading apparatus according to the present invention, the reading resumption reference position is appropriately set not by the first reference position setting means but by the second reference position setting means according to the error between the conveyance target and the reading length. Thus, an error between the conveyance amount and the reading length caused by the deviation is suppressed.

  According to the image reading apparatus configured as described above, the reading operation can be resumed by switching the reading resuming position so that no mismatch occurs between the dimension of the reading target and the dimension of the reading image. As a result, it is possible to suppress the image represented by the image data formed by combining the read image data for all lines from being stretched or crushed with respect to the image to be read. It is possible to configure an image reading apparatus that can generate high-quality image data that can be read easily.

  Specifically, the second reference position setting unit sets the position XP as the reading restart reference position when the reading length detected by the reading length detection unit is shorter than the conveyance amount detected by the conveyance amount detection unit. When the reading length detected by the reading length detection unit is longer than the conveyance amount detected by the conveyance amount detection unit, the position XF can be set as a reading resumption reference position. .

  In this way, even if the reading resumption position cannot be accurately adjusted to the reading interruption position, the reading length and the conveyance amount when the reading operation for all the lines is completed can be substantially matched. Dimensional mismatch can be suppressed.

  The operation control means selectively activates the first reference position setting means when the absolute value of the error between the conveyance target and the reading length is less than the threshold value, and the absolute value of the error is equal to or greater than the threshold value. In some cases, the second reference position setting means can be selectively activated (claim 3).

  By configuring the operation control means in this way, when the error between the reading length and the carry amount is small, the reading operation can be resumed by matching the reading resumption position with the reading interruption position by the offset time. Thus, the image quality of the read image can be improved, and if necessary, the second reference position setting means can be operated to efficiently eliminate the error between the read length and the carry amount. It is possible to avoid a mismatch between the dimension of the reading object and the dimension of the read image data corresponding to the reading object.

Embodiments of the present invention will be described below with reference to the drawings.
(1) Overall Configuration of Image Reading Apparatus 1 FIG. 1 is a block diagram showing an electrical configuration of the image reading apparatus 1 to which the present invention is applied. The image reading apparatus 1 according to the present embodiment includes a CPU 11 that executes various arithmetic processes, a ROM 12 that stores various programs and data, and a RAM 13 that is used as a work area when the CPU 11 performs calculations. Execute to control the entire device and realize the scanner function.

  The image reading apparatus 1 further includes a CCD line sensor 20, a reading control unit 21 that controls the CCD line sensor 20, a drive control unit 17 that controls the motors MT1 and MT2, and pulse signals from the encoders EN1 and EN2. An encoder processing unit 15 that executes processing based on the above and an external interface 23 are provided, and are configured to be able to communicate with an external device via the external interface 23. Examples of the external interface 23 include a USB interface and a LAN interface.

  The CCD line sensor 20 includes a light receiving element (photodiode) group 20a and a CCD analog shift register 20b arranged in a line (see FIG. 7), and is controlled by the reading control unit 21 so that a line start signal is transmitted. Each time it is input, signal charges representing pixel information accumulated in the light receiving element are input to the CCD analog shift register 20b, and during the period until the next line start signal is input, From the output end, pixel signals are sequentially output according to the transfer clock signal.

  The reading control unit 21 inputs a line start signal and a transfer clock signal to the CCD line sensor 20, controls the CCD line sensor 20, and causes the CCD line sensor 20 to read image information of a document to be read. A pixel signal as a reading result output from the CCD line sensor 20 is converted into digital pixel data. Then, each pixel data is arranged to generate line image data, which is written in the RAM 13.

  The CCD line sensor 20 is fixed at a predetermined reading position when the automatic conveyance reading function is operated, and receives an original from the reading position by the operation of the ADF device 150 (see FIG. 2) under the control of the reading control unit 21. Read. Further, the CCD line sensor 20 receives the rotational force of the reading motor MT1 controlled by the drive control unit 17 through the carriage when the stationary document reading function is operated, and performs image processing under the platen 102A on which the document is placed. The document moves in the reading direction, and along with the movement, the image information of the document is read line by line.

  More specifically, as shown in FIG. 2, an image reading window (hereinafter referred to as a stationary reading window) 102 for a stationary document reading function 102 and an image for an automatic conveyance reading function are provided in the casing of the image reading apparatus 1. A reading window (hereinafter referred to as an automatic reading window) 103 is provided. Both reading windows 102 and 103 are closed by transparent platens 102A and 103A such as glass and acrylic. FIG. 2 is a cross-sectional view showing a mechanical configuration of the image reading apparatus 1 of the present embodiment.

  In the image reading apparatus 1, a document cover 104 that covers both the reading windows 102 and 103 is swingably assembled on the upper surface side of the apparatus main body 101, and the document is read by the stationary reading window 102. In this case, the document cover 104 is manually opened by the user and the document to be read is placed on the stationary reading window 102.

  On the other hand, inside the apparatus main body 101, the CCD line sensor 20 described above receives the light reflected and reflected from the document just below the reading windows 102 and 103, and generates a pixel signal based on the received light. However, the CCD line sensor 20 has a longitudinal direction (in other words, a light receiving element arrangement direction) extending in a direction perpendicular to the moving direction of the CCD line sensor 20.

  Specifically, the CCD line sensor 20 is assembled so as to be movable in the longitudinal direction of the apparatus main body 101 (the left-right direction in FIG. 2) via the carriage 106, and the automatic reading window 103 is activated when the automatic conveyance reading function is activated. It is placed immediately below. On the other hand, when the stationary document reading function is activated, it moves at a constant speed under the control of the drive control unit 17 immediately below the stationary reading window 102.

  In this embodiment, the carriage 106 is connected to a belt 109 that is hung on a driving pulley 107 and a driven pulley 108, and the belt 109 is connected to a reading motor MT1 constituted by a DC motor via a gear. Is connected.

  That is, when the stationary document reading function is activated, the CCD line sensor 20 receives the rotational force of the reading motor MT1 through the belt 109 and is guided by the guide shaft 111 installed in parallel with the belt 109, while Move straight in the longitudinal direction. FIG. 3 is an explanatory diagram showing a movement mode of the CCD line sensor 20.

  A reading encoder EN1 is provided on the rotation shaft of the reading motor MT1, and the reading encoder EN1 outputs a pulse signal (A phase signal, B phase signal) every time the reading motor MT1 rotates by a predetermined angle. It is configured as. The image reading apparatus 1 is configured such that when the reading motor MT1 rotates by a predetermined angle, the CCD line sensor 20 moves by a predetermined distance. In this embodiment, an encoder processing unit is based on the pulse signal of the reading encoder EN1. At 15, the position and moving speed of the CCD line sensor 20 are detected, and further, the rotational direction of the motor is detected based on the A phase signal and the B phase signal.

  The image reading apparatus 1 controls the reading motor MT1 by the drive control unit 17 based on the detection result, and moves the CCD line sensor 20 at a constant speed along the guide shaft 111 while reading the control unit. At 21, the CCD line sensor 20 is controlled to realize a still image reading function.

  In addition, an ADF device 150 that conveys a document to be read to the automatic reading window 103 is provided in a portion of the document cover 104 corresponding to the automatic reading window 103, and is operated by the user when the automatic conveyance reading function is activated. The documents stacked on the document tray 165 are separated and conveyed to the automatic reading window 103 which is a reading position.

  The ADF device 150 is a separation mechanism that separates the stacked originals one by one, a separation roller 153 that applies a conveying force to the original placed on the uppermost layer, and a separation roller 153 that is disposed opposite the separation roller 153. A separation pad 154 that contacts the document from the opposite side of the roller 153 and applies a predetermined conveyance resistance, and a suction roller 155 that feeds the document to the separation roller 153 so as to suck the document stacked on the document tray 165 are provided. .

  In addition, the ADF apparatus 150 turns the direction of conveyance of the document separated and conveyed from the separation mechanism toward the automatic reading window 103 as a conveyance mechanism that conveys the document separated by the separation mechanism to the automatic reading window 103. A paper feed roller 159 that applies a conveying force while being provided, a pair of pinch rollers 160 that press the document against the paper feed roller 159, a document press 161, a paper discharge roller 162, and a document sensor actuator 164 are provided.

  Each roller constituting the ADF device 150 is rotated by receiving the rotational force of the reading and conveying motor MT2, and is configured to convey the document from the document tray 165 to the discharge tray 166. Then, when the reading and conveying motor MT2 rotates by a predetermined angle, the original to be read moves by a predetermined distance.

  The document presser 161 presses the conveyed document toward the automatic reading window 103 side. The CCD line sensor 20 reads a document passing through this point while being arranged below the document presser 161 when the automatic conveyance reading function is activated.

  The document sensor actuator 164 is arranged upstream of the document presser 161 and detects whether or not the document has passed. That is, in this embodiment, the encoder processing is performed based on the ON / OFF signal from the document sensor actuator 164 and the pulse signal from the reading / transporting encoder EN2 installed on the rotation shaft of the reading / transporting motor MT2 formed of a DC motor. The unit 15 detects the document transport position. The reading / transporting encoder EN2 is a rotary encoder that outputs a pulse signal (A phase signal, B phase signal) every time the reading / transporting motor MT2 rotates by a predetermined angle.

  The image reading apparatus 1 controls the conveyance of the original by the drive control unit 17 based on the detection result, conveys the original to the reading position at a constant speed, and the CCD line sensor at the reading control unit 21. 20 is controlled to realize an automatic conveyance reading function.

  The stationary document reading function is such that when a document is not placed on the document tray 165, a reading key (not shown) provided in the image reading apparatus 1 is pressed or a reading command is issued through the external interface 23. When input, the operation is started by a program executed by the CPU 11. With this operation, the image reading apparatus 1 reads the document placed on the stationary reading window 102.

On the other hand, the automatic conveyance reading function starts to operate according to a program executed by the CPU 11 when a reading key is pressed or a reading command is input through the external interface 23 with a document placed on the document tray 165. To do. In the image reading apparatus 1, the automatic conveyance reading function is repeatedly operated until the document placed on the document tray 165 is empty, and each document placed on the document tray 165 is sequentially read. Whether or not a document is not placed on the document tray 165 can be determined based on a detection signal of a sensor (not shown) provided on the document tray 165.
(2) Detailed Configuration of Encoder Processing Unit 15 and Drive Control Unit 17 Subsequently, detailed configurations of the encoder processing unit 15 and the drive control unit 17 will be described with reference to FIGS. FIG. 4 is a block diagram illustrating the configuration of the encoder processing unit 15 and the drive control unit 17.
(2.1) Configuration of Encoder Processing Unit 15 The encoder processing unit 15 of the present embodiment has a set of an encoder edge detection unit 31, a position counter 33, and a period counter 35 for each of the encoders EN1 and EN2. By these sets, the amount of rotation of the motors MT1 and MT2 in which the encoders EN1 and EN2 are installed, and as a result, the amount of movement of the conveyance target is detected.

  Specifically, the encoder edge detection unit 31 of the encoder processing unit 15 detects the rising edge (for example, the rising edge of the A-phase signal) of the pulse signal input from the corresponding encoders EN1 and EN2, and detects each edge detection. In addition, an edge detection signal is output. This edge detection signal is input to a corresponding set of position counter 33 and period counter 35.

  The edge detection signal output from the encoder edge detector 31 for the read encoder EN1 to which the pulse signal (encoder signal) from the read encoder EN1 is input is input to the position counter 33 and the period counter 35 for the read encoder EN1. At the same time, when the stationary document reading function is activated, it is input to the drive stop command generating unit 49, the time measuring unit 55, and the forced synchronization command generating unit 59 included in the reading control unit 21.

  The value enc_cnt output from the position counter 33 for the reading encoder EN1 and the value enc_cyc output from the cycle counter 35 for the reading encoder EN1 are input to the drive control unit 17. The value enc_cnt output from the position counter 33 for the reading encoder EN1 is also input to the transport amount calculation unit 51 and the forced synchronization command generation unit 59 provided in the reading control unit 21 when the stationary document reading function is activated. The

  In addition, the edge detection signal output from the encoder edge detector 31 for the read / carry encoder EN2 to which the pulse signal from the read / carry encoder EN2 is input is input to the position counter 33 and the period counter 35 for the read / carry encoder EN2. At the same time, when the automatic conveyance reading function is activated, it is input to the drive stop command generating unit 49, the time measuring unit 55, and the forced synchronization command generating unit 59 provided in the reading control unit 21.

  Further, the value enc_cnt output from the position counter 33 for the reading and transporting encoder EN2 and the value enc_cyc output from the cycle counter 35 for the reading and transporting encoder EN2 are input to the drive control unit 17. Further, the value enc_cnt output from the position counter 33 for the reading and transport encoder EN2 is also input to the transport amount calculation unit 51 and the forced synchronization command generation unit 59 provided in the reading control unit 21 when the automatic transport reading function is activated. Is done.

  When the image reading apparatus 1 is turned on, the cycle counter 35 receives the edge detection signal every time an edge detection signal is input from the corresponding encoder edge detection unit 31, as shown in FIG. 5B. The time interval (the time interval between the time when the current edge detection signal is input and the time when the previous edge detection signal is input) is detected, and the detected input time interval is output as the value enc_cyc. Yes. By such an operation, the period counter 35 for the reading encoder EN1 detects the time required for the reading motor MT1 to rotate by a certain angle, and consequently the moving time per unit distance of the CCD line sensor 20. Similarly, the cycle counter 35 for the reading and transport encoder EN2 detects the movement time per unit distance of the document. The reciprocal of the moving time represents the speed, and the drive control unit 17 uses this speed information to control the motor to be controlled.

  Further, when the image reading apparatus 1 is turned on, the position counter 33 starts the processing shown in FIG. 5A, and thereafter continuously updates the value enc_cnt. FIG. 5A is a flowchart showing the process executed by the position counter 33. Here, the processing executed by the position counter 33 for the reading encoder EN1 will be described with reference to FIG. 5A. However, the position counter 33 for the reading encoder EN1 also includes the position counter 33 for the reading control encoder EN2. A similar process is performed.

  When the process shown in FIG. 5A is started, the position counter 33 first sets the variable enc_cnt to zero on the condition that the conveyance target (CCD line sensor 20) is arranged at a predetermined origin position (home position). (S110), and then waits until an edge detection signal is input from the encoder edge detector 31 for the reading encoder EN1 (S120). When the edge detection signal is input, the rotation direction of the corresponding reading motor MT1 is determined (S130). If the rotation direction of the reading motor MT1 is the forward direction, the variable enc_cnt is incremented by 1 (S140), and then , S120 is entered. On the other hand, when the rotation direction of the reading motor MT1 is the reverse direction, the variable enc_cnt is decremented by 1 (S150), and the process proceeds to S120. It is assumed that the encoder processing unit 15 is provided with a function for identifying the rotation direction of the corresponding motor based on the A phase signal and the B phase signal input from the encoder for each encoder.

In this way, the position counter 33 counts up the variable enc_cnt every time an edge detection signal is input when the motor is rotating in the forward direction, and when the motor is rotating in the reverse direction, the edge counter 33 Each time a detection signal is input, the variable enc_cnt is counted down. Accordingly, the position counter 33 for the reading encoder EN1 detects the position of the CCD line sensor 20, and the position counter 33 for the reading and conveying encoder EN2 detects the conveyance position of the document.
(2.2) Detailed Configuration of Drive Control Unit 17 Next, the configuration of the drive control unit 17 will be described. As shown in FIG. 4, the drive control unit 17 includes a motor control unit 39 that controls the reading motor MT <b> 1 and the reading conveyance motor MT <b> 2 via a driving circuit 37. The motor control unit 39 controls the motors MT1 and MT2 to be controlled based on the outputs enc_cnt and enc_cyc of the position counter 33 and the cycle counter 35 corresponding to the encoder attached to the motor to be controlled.

  More specifically, the motor control unit 39 controls the reading motor MT1 based on the values enc_cnt and enc_cyc from the position counter 33 and period counter 35 for the reading encoder EN1 included in the encoder processing unit 15, and also reads the reading transport encoder EN2. Based on the values enc_cnt and enc_cyc from the position counter 33 and the cycle counter 35, the reading and conveying motor MT2 is controlled.

  Specifically, when the reading function is activated, the motor control unit 39 receives a command from the CPU 11, selects one of the reading motor MT1 and the reading transport motor MT2 as a control target, and controls the selected control target. Therefore, the execution of the process shown in FIG. 6 is started. When the stationary document reading function is operated, the reading motor MT1 is selected as a control target, and when the automatic document reading function is operated, the reading conveyance motor MT2 is selected as a control target.

  In addition, when the process shown in FIG. 6 is completed based on the mtstop signal (detailed later) as a motor stop command signal before the reading of the reading target is completed, the motor control unit 39 receives a reading restart command from the CPU 11. Only once, the execution of the process shown in FIG. 6 is started again.

FIG. 6 is a flowchart showing processing executed by the motor control unit 39.
When the process shown in FIG. 6 is started, the motor control unit 39 performs motor drive setting, and sets the motor rotation direction to the forward direction (image reading direction) (S310). In S310, the target rotational speed of the motor is set according to the reading resolution.

  When this process is completed, the motor control unit 39 controls the motor to be controlled in accordance with the content of the drive setting performed in S310 ahead of time (S320). Specifically, in S320, the rotation of the motor is accelerated to around the set target rotation speed, and then the motor is controlled so that the rotation speed of the motor becomes the target rotation speed regardless of the conveyance load. In this embodiment, the conveyance target is moved in the image reading direction at a constant speed in this way.

  Further, during execution of the control, it is determined whether or not a reading end signal (details will be described later) is input (S330). If the reading end signal is not input (No in S330), the drive is stopped. It is determined whether or not the mtstop signal input from the command generator 49 is a value 1 (S340). If the reading end signal is not input (No in S330) and the mtstop signal is not 1 (No in S340), the motor control is continuously executed while making the determinations in S330 and S340. To do.

  On the other hand, when the mtstop signal is switched to the value 1, processing for decelerating and stopping the motor to be controlled is performed (S350). After the motor stops, the motor drive setting is performed, the motor rotation direction is set to the opposite direction to the image reading direction, and the target rotation speed and rotation time of the motor are set to predetermined predetermined values. (S360). In S360, the target rotation speed and rotation time of the motor are set as “the motor necessary and sufficient to converge the motor to the target rotation speed in S320 to the maximum rotation amount required until the motor decelerates and stops in S350. A value necessary for “the motor rotates” is set by adding the rotation amount. This predetermined value is assumed to be predetermined in the design stage in this embodiment.

  When this process is completed, the motor control unit 39 rotates the motor in the reverse direction for a predetermined time according to the setting content at the time of drive setting (S370). By this operation, the conveyance target (CCD line sensor 20 or the original to be read) conveyed by the rotational force of the motor is located at a point sufficiently before acceleration (at the point where the mtstop signal is switched to the value 1). More specifically, the conveyance target is moved backward to a point where it can travel at a constant speed before reaching a later-described reading restart reference position restart_cnt. Then, once the rotation / stop of the motor in S370 is completed, the motor is paused.

  On the other hand, when the reading end signal is input (Yes in S330), the motor control unit 39 determines whether or not the operating reading function is a stationary document reading function (S380). If it is a stationary document reading function (Yes in S380), a process of decelerating and stopping the motor to be controlled is performed (S390). After the motor is stopped, the motor drive setting is performed and the motor rotation direction is set. Is set in the direction opposite to the image reading direction (S400).

  When this process is completed, the motor control unit 39 drives the motor to be controlled (reading motor MT1) and transports the transport target (CCD line sensor 20) to the home position (S410). Then, when the CCD line sensor 20 is transported to the home position, it temporarily stops. In the present embodiment, the home position of the CCD line sensor 20 is set to a fixed position of the CCD line sensor 20 when the automatic document reading function is activated.

In addition, when the reading function in operation is the automatic conveyance reading function (No in S380), the motor control unit 39 discharges the motor to be controlled (the reading conveyance motor MT2), and the document being conveyed is discharged to the discharge tray 166. Until the document is completely discharged, the motor stops rotating (S420) and pauses.
(3) Detailed Configuration of Reading Control Unit 21 Subsequently, a detailed configuration of the reading control unit 21 will be described. FIG. 7 is a block diagram illustrating a detailed configuration of the reading control unit 21.

As shown in FIG. 7, the reading control unit 21 includes a reading front end 41, an image data processing unit 43, a local RAM 45, a drive stop command generating unit 49, a carry amount calculating unit 51, a reading length calculating unit 53, and a time measuring unit 55. The restart position setting unit 57 and the forced synchronization command generation unit 59 are provided as components, and the reading control unique to the present invention is realized using these units. Hereinafter, details of each part will be described individually.
(3.1) Details of Reading Front End 41 The reading front end 41 provided in the reading control unit 21 of the present embodiment is connected to the CCD line sensor 20 and inputs a control signal to the CCD line sensor 20, and the CCD line sensor. The pixel signal as a reading result input from 20 is received and processed.

  The reading front end 41 includes a line start trigger signal generation unit 41a, a line start signal generation unit 41b, and a transfer clock signal generation unit 41c. The line start trigger signal generation unit 41a periodically performs a line start trigger (l_start_trg). ) Signal is generated, and a line start signal for designating the reading timing of the line image is input to the CCD line sensor 20 based on the line start trigger signal.

  The line start trigger signal is a signal that defines the output timing of the line start signal. The line start trigger signal is generated by the line start trigger signal generation unit 41a at the input cycle of the line start signal to be input to the CCD line sensor 20, and the line start signal The data is input to the generation unit 41b.

  When the reading function is activated, the line start trigger signal generation unit 41a stands by until a synchronization command is received from the forced synchronization command generation unit 59. When the synchronization command is received from the forced synchronization command generation unit 59, the command input At this timing, a line start trigger signal is output, and thereafter, the line start trigger signal is output periodically (see FIG. 20A). Thereby, in this embodiment, the reading operation by the CCD line sensor 20 is started from a predetermined reading start position init_pos.

  The line start signal generation unit 41b inputs a line start signal having a prescribed pulse width suitable for the CCD line sensor 20 to the CCD line sensor 20 at the input timing of the line start trigger signal. When this line start signal is input, in the CCD line sensor 20, the signal charge accumulated in the light receiving element is input to the CCD analog shift register 20b, and the image information read before the input of the line start signal is the CCD analog shift register. 20b is stored and held. At this timing, the signal charge is reset in the light receiving element, and a new reading operation using the photoelectric effect is performed.

  The transfer clock signal generation unit 41 c generates a transfer clock signal for causing the CCD analog shift register 20 b to output a pixel signal, and this transfer clock signal is input to the CCD line sensor 20.

  The image information for one line stored in the CCD analog shift register 20b by the input of the transfer clock signal is received from the CCD analog shift register 20b until the next line start signal is input as a pixel signal. Is output.

  The pixel signal input from the CCD analog shift register 20b to the reading front end 41 is converted into digital pixel data by an A / D (analog / digital) converter 41d (see FIG. 8) of the reading front end 41. Each pixel data is serially arranged for one line and transferred to the image data processing unit 43 as line image data.

  The reading front end 41 configured in this manner also inputs the line start trigger signal output from the line start trigger signal generation unit 41a to the carry amount calculation unit 51, the read length calculation unit 53, and the time measurement unit 55. To do.

  Further, the reading front end 41 stops outputting the line start trigger signal and the line start signal when the stop_sig signal as the stop command signal is switched from the value 0 to the value 1, and at this time, the CCD analog shift register 20b. The output of the transfer clock signal is continued until the image information stored and held in the memory is output as a pixel signal, and then the output of the transfer clock signal is stopped when the pixel signal is output. In other words, when the stop_sig signal transitions from the value 0 to the value 1, the reading front end 41 reads the line image data of the line whose image information is stored and held in the CCD analog shift register 20b at that time to the image data processing unit 43. And this line is set as a read completion line.

  Thereafter, the reading front end 41 waits until the synchronization command is input from the forced synchronization command generation unit 59. When the synchronization command is input, the line start trigger signal, the line start signal, and the transfer are started again from that point. Resume clock signal output.

That is, when the line start trigger signal generation unit 41a pauses the output of the line start trigger signal before the reading of the reading target is completed, the line start trigger signal generation unit 41a transits to the state of waiting for the synchronization command from the forced synchronization command generation unit 59 and generates the forced synchronization command generation. Wait until a synchronization command is received from the unit 59. When the synchronization command is received from the forced synchronization command generator 59, the output of the line start trigger signal is resumed at the command input timing, and thereafter the line start trigger signal is output periodically (FIG. 20 ( a) (b)).
(3.2) Details of Image Data Processing Unit 43 Next, details of the image data processing unit 43 will be described with reference to FIGS.

  The image data processing unit 43 sequentially writes the line image data input from the reading front end 41 into a buffer 45a as a FIFO memory provided in the local RAM 45, and for each line image data stored in the buffer 45a. And a data processing function for performing image processing such as shading correction and gamma correction, and writing each line image data after the image processing to the RAM 13 through the memory controller 63.

  Further, the image data processing unit 43 outputs a stop command signal (stop_sig signal) for temporarily stopping the transfer of the line image data from the reading front end 41 based on the free space of the buffer 45a, and the line image data. Has a stop / restart control function for outputting a restart command signal (restart_sig signal) for restarting the transfer.

FIG. 8 is an explanatory diagram relating to the data processing function realized by the image data processing unit 43.
The image data processing unit 43 includes a data writing unit 43a, an image processing unit 43b, and a data transfer unit 43c as a configuration for realizing a data processing function, and image data for one line from the reading front end 41. When the line image data is input, the data writing unit 43a writes the line image data into the buffer 45a.

  The image data processing unit 43 reads the line image data recorded at the reading position of the buffer 45a in the image processing unit 43b, performs image processing such as shading correction and gamma correction on the line image data, The line image data after the image processing is temporarily stored in the processing data storage unit 45b in the local RAM 45. The image data processing unit 43 writes each line image data stored in the processing data storage unit 45b to the RAM 13 through the data transfer unit 43c, and generates image data representing the read image on the RAM 13.

Also, the functional blocks in the image data processing unit 43 shown in FIG. 7 are functional blocks related to the stop / resume control function.
As shown in FIG. 7, the image data processing unit 43 includes a stop signal generation unit 43d that outputs a stop_sig signal as a stop command signal, and a restart signal generation unit 43e that outputs a restart_sig signal as a restart command signal. .

  Specifically, the stop signal generation unit 43d executes the processing illustrated in FIG. 9 and switches the state of the output stop_sig signal. FIG. 9 is a flowchart showing the process executed by the stop signal generator 43d when the reading function is activated.

  When the processing shown in FIG. 9 is started, the stop signal generation unit 43d sets the stop_sig signal to a value of zero (S510), and thereafter, based on the number of lines of image data input from the reading front end 41, It is determined whether or not the acquisition of the line image data is completed (S520). If the acquisition of the line image data up to the final line has been completed (Yes in S520), a reading end signal is output to notify each unit of the end of reading (S560). The processing shown in FIG.

  On the other hand, if the acquisition of line image data up to the last line has not been completed (No in S520), it is determined whether or not the free capacity rem_buf of the buffer 45a is equal to or smaller than a predetermined threshold B_lim (S530). ). If the free capacity rem_buf of the buffer 45a is larger than the threshold value B_lim (No in S530), it is determined that there is sufficient free capacity for writing line image data, and the process proceeds to S510, and the stop_sig signal is set to zero. .

  On the other hand, when the free capacity rem_buf of the buffer 45a is equal to or smaller than the threshold B_lim (Yes in S530), the stop signal generation unit 43d determines that the total amount rem_lin of the line image data up to the last line that needs to be written in the future is the buffer 45a. It is determined whether or not the free space is rem_buf or less (S540). If the total amount rem_lin is less than or equal to the free space rem_buf (Yes in S540), the buffer 45a is not filled until the end of reading. The process proceeds to S510, the stop_sig signal is set to zero, and control is performed so that the output of line image data from the reading front end 41 does not stop.

  On the other hand, when the total amount rem_lin is larger than the free space rem_buf (No in S540), the stop signal generation unit 43d changes the setting of the stop_sig signal from the value zero to the value 1, and outputs the line image data from the reading front end 41. Is stopped (S550). Thereafter, the process proceeds to S520. The stop_sig signal whose state is switched in this way is input to the reading front end 41, the drive stop command generation unit 49, the reading length calculation unit 53, and the restart position setting unit 57.

  In addition, the restart signal generation unit 43e executes the process illustrated in FIG. 10 to switch the state of the restart_sig signal. FIG. 10 is a flowchart showing processing executed by the restart signal generation unit 43e when the reading function is activated.

  When the process shown in FIG. 10 is started, the restart signal generating unit 43e first sets the restart_sig signal to a value of zero (S610), and thereafter, based on the number of lines of image data input from the reading front end 41, It is determined whether or not the acquisition of the line image data is completed (S620). If the acquisition of the line image data up to the last line is completed (Yes in S620), the process is paused.

  On the other hand, if the acquisition of the line image data up to the last line has not been completed (No in S620), it is determined whether or not the free capacity rem_buf of the buffer 45a is equal to or larger than a predetermined threshold B_th (S630). ). If the free capacity rem_buf is equal to or greater than the threshold B_th (Yes in S630), the restart_sig signal is set to a value 1 assuming that the free capacity rem_buf of the buffer 45a is sufficient for restarting (S650). Thereafter, the process proceeds to S620. Note that the threshold B_th is set to a value larger than the threshold B_lim (B_th> B_lim).

  In addition, when the free capacity rem_buf of the buffer 45a is less than the threshold B_th (No in S630), the restart signal generation unit 43e stores the free space capacity rem_buf of the line image data up to the final line that needs to be written in the future. It is determined whether or not the total amount rem_lin is equal to or larger than the total amount rem_lin (S640), and if the free space rem_buf is equal to or larger than the total amount rem_lin (Yes in S640), Is changed from value zero to value 1 (S650). Thereafter, the process proceeds to S620.

  On the other hand, when the free capacity rem_buf of the buffer 45a is not equal to or greater than the threshold value B_th and not equal to or greater than the total amount rem_lin, the restart signal generator 43e proceeds to S610, assuming that the free capacity rem_buf of the buffer 45a is not sufficient for restart. And set the restart_sig signal to the value zero. Thereafter, the process proceeds to S620.

A restart_sig signal whose state is switched in this way is input to the CPU 11. Further, the CPU 11 constantly monitors the restart_sig signal. When the restart_sig signal is switched from the value 0 to 1, the CPU 11 inputs a reading restart command to the motor control unit 39, and performs the processing shown in FIG. In addition to the execution from S310, a reading restart command is input to the reading length calculation unit 53, the restart position setting unit 57, and the forced synchronization command generation unit 59.
(3.3) Details of Drive Stop Command Generating Unit 49 Next, details of the drive stop command generating unit 49 will be described with reference to FIG. FIG. 11 is a flowchart showing the process executed by the drive stop command generation unit 49.

  The drive stop command generation unit 49 outputs an mtstop signal as a motor stop command signal to the motor control unit 39. When the reading function is activated, the drive stop command generation unit 49 starts the processing shown in FIG. Based on the inputted stop_sig signal, the state of the mtstop signal is switched.

  When this process is started, the drive stop command generation unit 49 sets the mtstop signal to zero (S810), and determines whether or not a reading end signal is input from the image data processing unit 43, thereby reading. It is determined whether or not the target reading (reading of one original document) has been completed (S820). If the reading has been completed (Yes in S820), the mtstop signal is set to zero again (S830) and then paused.

  On the other hand, if the reading has not ended (No in S820), the drive stop command generation unit 49 outputs the mtstop signal until the reading ends or the stop_sig signal input from the image data processing unit 43 becomes 1. Keep the value zero. When the stop_sig signal transitions to the value 1 (Yes in S840), after that, when the edge detection signal is input (Yes in S850), the mtstop signal is changed to the value 1 (S860). Thereafter, the process proceeds to S820, where the mtstop signal is held at the value 1 during the period in which the stop_sig signal has the value 1, and when the stop_sig signal transitions to the value 0, the mtstop signal is switched to the value 0.

Thus, when the mtstop signal is switched to the value 1, the motor control unit 39 starts the deceleration of the motor as described above. FIG. 12 is a time chart showing the states of various signals before and after the mtstop signal switches to the value 1.
(3.4) Details of Conveyance Amount Calculation Unit 51 Next, details of the conveyance amount calculation unit 51 will be described with reference to FIG. FIG. 13 is a flowchart showing processing executed by the carry amount calculation unit 51.

  The carry amount calculation unit 51 outputs to the restart position setting unit 57 the values of the variable position and the variable q_trans necessary to set the reading restart reference position restart_cnt. This variable q_trans represents the transport amount to be transported from the reading start position init_pos to the present. When the reading function is activated, the carry amount calculation unit 51 starts the process illustrated in FIG. 13 and updates the values of the variable q_trans and the variable position every time a line start trigger signal is input from the reading front end 41.

  When the processing shown in FIG. 13 is started, the carry amount calculation unit 51 determines whether or not a reading end signal is input (S910). If the reading end signal is not input (No in S910), It is determined whether or not a line start trigger signal is input (S920).

When neither the reading end signal nor the line start trigger signal is input, the process waits until either of these signals is input.
When the line start trigger signal is input (Yes in S920), the output value enc_cnt of the position counter 33 at that time is set to the variable position, so that the line start trigger signal is input before and finally at the end. The position of the conveyance target at the time when the edge detection signal is input is stored and held (S930). When the edge detection signal is input simultaneously with the line start trigger signal, the value enc_cnt updated by the edge detection signal is set in the variable position.

  Further, the carry amount calculation unit 51 updates the value of the variable q_trans using the updated value of the variable position. Specifically, before the reading function is activated, the pulse distance δ set in the register RG1 and the reading start position init_pos set in the register RG2 and the value of the current variable position are used in advance by the operation of the CPU 11. The transport amount q_trans is calculated as follows (S940).

q_trans = (position−init_pos) · δ
The pulse distance δ here is a moving distance of the conveyance target corresponding to one pulse period of the encoder. When the edge detection signal is output from the encoder edge detection unit 31 every time the conveyance target moves by a predetermined amount A, the pulse distance δ = A.

In addition, when the carry amount q_trans is updated in this way, the carry amount calculation unit 51 proceeds to S910 and updates the values of the variable q_trans and the variable position every time a line start trigger signal is input. Then, when the reading end signal is input (Yes in S910), the reading is stopped.
(3.5) Details of Reading Length Calculation Unit 53 Next, details of the reading length calculation unit 53 will be described with reference to FIG. FIG. 14 is a flowchart showing processing executed by the reading length calculation unit 53 when the reading function is activated.

  When the stop_sig signal transitions from the value 0 to the value 1 and the processing related to the reading function is interrupted, the reading length calculation unit 53 includes information on the number of lines that have been read up to that point (the number of lines that have been read) fn_line. Based on this, the reading length read_l is calculated, and this value is output to the restart position setting unit 57. The reading length here refers to the length in the image reading direction of the read image data from the first line to the reading completion line.

  For example, when the first line is the first and the read completion line is the Mth line, the read length read_l can be calculated by read_l = M · line_d using the line distance line_d. The line distance line_d means the length in the image reading direction for one line to be read. For example, the line start signal is input to the CCD line sensor 20 at a cycle Z, and the conveyance target is set at the speed V. When traveling at a constant speed and causing the CCD line sensor 20 to execute the reading operation for each line, the line distance line_d is line_d = V · Z.

  In the present embodiment, as described above, the reading start position init_pos set in the register RG2 is handled as the starting position of the reading operation of the first line, and the line starts from the time when the conveyance target passes through the reading start position init_pos. The start trigger signal is output, the line start signal is input to the CCD line sensor 20, and the output of the line start trigger signal is temporarily stopped when the stop_sig signal transitions to the value 1. The reading length is calculated with the processing content shown in FIG.

  When the process shown in FIG. 14 is started, the reading length calculation unit 53 resets the flag (flag) to a value of 0, sets the number of read completion lines fn_line to a value of 0 (S1010), and then inputs a reading end signal. It is determined whether it has been performed (S1020). If no reading end signal is input (No in S1020), it is determined whether a line start trigger signal is input (S1030).

  If a line start trigger signal is input (Yes in S1030), the number of read completion lines fn_line is updated to a value obtained by adding 1 (S1035), and the process proceeds to S1040. On the other hand, when the line start trigger signal is not input (No in S1030), the process of S1035 is not executed and the process proceeds to S1040. In this way, the reading length calculation unit 53 updates the value of the variable fn_line every time a line start trigger signal is input.

In S1040, it is determined whether or not the stop_sig signal input from the image data processing unit 43 is set to a value of 1.
Here, when the stop_sig signal is set to the value 0 (No in S1040), the reading length calculation unit 53 determines whether or not a reading restart command is input from the CPU 11 (S1050), and the reading restart command is received. If it has not been input (No in S1050), the process proceeds to S1020 without executing the process of S1055, but if a reading resumption command has been input (Yes in S1050), a flag (flag) is set. After resetting to 0, the process proceeds to S1020.

  On the other hand, when the stop_sig signal is set to the value 1 (Yes in S1040), the reading length calculation unit 53 determines whether or not the flag (flag) is the value 0 (S1060), and the flag (flag) is set. When the value is 1 (No in S1060), the process proceeds to S1020 without executing the processes after S1070.

  On the other hand, when the flag is 0 (Yes in S1060), the read completion line number fn_line is decremented by 1 (S1070), and the read completion line at the time when the stop_sig signal transitions to the value 1 The number fn_line is determined. In this way, the number of read completion lines fn_line is decremented by 1, the line start trigger signal input immediately before the stop_sig signal transitions to the value 1 is a line start trigger signal corresponding to the read interruption line, This is because the reading operation of the reading interruption line is performed again after the reading is resumed.

  When the read completion line number fn_line is determined in this way, information on the read completion line number fn_line and information on the line distance line_d set in the register RG3 in advance by the operation of the CPU 11 before the reading function is activated. Based on the above, the reading length read_l is calculated as follows (S1080), and the calculated value is output to the restart position setting unit 57.

read_l = fn_line · line_d
At the same time, the read length calculation unit 53 sets a flag (flag) to a value 1 (S1090). When this process ends, the read length calculation unit 53 proceeds to S1020.

In this embodiment, the number of read completion lines fn_line is detected in this way, and this value is input to the restart position setting unit 57. Then, when the reading end signal is input (Yes in S1020), the processing shown in FIG.
(3.6) Details of Time Measuring Unit 55 Next, details of the time measuring unit 55 will be described with reference to FIG. FIG. 15 is a flowchart showing processing executed by the time measuring unit 55 when the reading function is activated.

  The time measuring unit 55 outputs the value of the variable time_p necessary for setting the reading resume reference position (restart_cnt) to the resume position setting unit 57. The time measuring unit 55 has a built-in time counter, and measures time using the time counter.

  When the processing shown in FIG. 15 is started, the time measuring unit 55 determines whether or not a reading end signal is input from the image data processing unit 43 (S1110), and when the reading end signal is not input (S1110). In S1110, it is determined whether or not an edge detection signal is input (S1120). If no edge detection signal is input (No in S1120), whether or not a line start trigger signal is input. Is determined (S1130).

When none of the reading end signal, the edge detection signal, and the line start trigger signal is input, the process waits until any of these signals is input.
When the edge detection signal is input (Yes in S1120), the time counter starts counting (S1125), and causes the time counter to measure the elapsed time from the input time of the edge detection signal. Prior to the start of timing, the time counter value CN is reset to zero. When the timing is started, the process proceeds to S1130, and it is determined whether or not a line start trigger signal is input. If the line start trigger signal is not input (No in S1130), the process proceeds to S1110. If the line start trigger signal is input (Yes in S1130), the process proceeds to S1140.

  When the line start trigger signal is input (Yes in S1130), the time measurement unit 55 sets the value CN of the time counter to the variable time_p (S1140), and finally the edge detection signal is input. Is set to a variable time_p, and this value is output to the restart position setting unit 57. Thereafter, the process proceeds to S1110, and waits until any of a reading end signal, an edge detection signal, and a line start trigger signal is input.

Then, when a reading end signal is input (Yes in S1110), it is determined that reading of a reading target (reading of one original) has been completed, and the processing illustrated in FIG.
In this way, the time measuring unit 55 performs the line start trigger after the edge detection signal is input based on the edge detection signal input from the encoder processing unit 15 and the line start trigger signal input from the reading front end 41. The time length time_p until the signal is input is measured and output to the restart position setting unit 57.
(3.7) Details of Restart Position Setting Unit 57 Next, details of the restart position setting unit 57 will be described with reference to FIG. FIG. 16 is a flowchart showing the process executed by the restart position setting unit 57.

  When the stop_sig signal output from the image data processing unit 43 transitions to a value of 1 and the processing related to the reading function is interrupted, the restart position setting unit 57 performs a reading restart reference for a reading operation that is restarted thereafter. A position (restart_cnt) and an offset time (offset) are set, and the values restart_cnt and offset are input to the forced synchronization command generation unit 59, thereby setting a reading resume position for the forced synchronization command generation unit 59. It is.

  Specifically, the restart position setting unit 57 starts executing the process shown in FIG. 16 when the reading function is activated. Further, even when a reading restart command is input from the CPU 11, execution of the processing shown in FIG. 16 is started.

  When the process shown in FIG. 16 is started, the restart position setting unit 57 waits until the stop_sig signal output from the image data processing unit 43 transitions from the value 0 to the value 1 (S1210), and the stop_sig signal transitions to the value 1. Then (Yes in S1210), the process proceeds to S1220.

  In S1220, the process waits for the end of the processing of S1080 executed by the reading length calculation unit 53 in accordance with the transition of the stop_sig signal, acquires the value of the reading length read_l calculated in S1080, and calculates the carry amount. The value of the carry amount q_trans output from the unit 51 is acquired, and an error μ between the reading length read_l and the carry amount q_trans at the time when the line start trigger signal is last input is calculated based on these acquired values. .

μ = read_l-q_trans
At the same time, the value position updated by the carry amount calculation unit 51 when the line start trigger signal is last input is set to the variable X [0], and the variable X [1] is larger than the value position by one. A value (position + 1) is set (S1220).

Then, it is determined whether or not the absolute value | μ | of the error μ is equal to or smaller than a predetermined threshold value (S1230).
If it is determined that the absolute value | μ | of the error μ is equal to or smaller than a predetermined threshold (Yes in S1230), the restart position setting unit 57 sets a value X [0] to the variable restart_cnt. The value is input to the forced synchronization command generation unit 59 (S1240), and the value time_p input from the time measurement unit 55 is set in the variable offset, and this value is input to the forced synchronization command generation unit 59 (S1250). As a result, the reading restart reference position is set to X [0] and the offset time is set to the value time_p for the forced synchronization command generation unit 59. Thereafter, the process shown in FIG. 16 ends.

  FIG. 17 is an explanatory diagram visualizing the setting method of the reading resume reference position and the offset time when the value | μ | is equal to or smaller than the threshold value. In the present embodiment, when the value | μ | is equal to or smaller than the threshold value, the edge detection signal is the last in the past from the time TS including the time TS when the line start signal corresponding to the reading interruption line is input to the CCD line sensor 20. The point X [0] at which the conveyance target exists at the time TP when the “” is input is set as the reading restart reference position restart_cnt, and the elapsed time time_p from the time TP to the time TS is set as the offset time offset.

  In response to this setting, when the conveyance target reaches the reading restart reference position restart_cnt when the reading is resumed, the forced synchronization command generating unit 59 sends the synchronization command to the line start trigger signal when the offset time offset has elapsed from that point. The data is input to the generation unit 41a, and the reading operation is restarted by the CCD line sensor 20 from this point (details will be described later).

  That is, here, for the forced synchronization command generator 59, the reading resumption reference position is set to X [0] and the offset time is set to the value time_p, thereby setting the reading interruption position to the reading resumption position. .

  However, since the reading restart position is determined by the offset time with reference to the point X [0] as described above, the conveyance target is traveling at the same speed when reading is interrupted and when reading is restarted. In this case, the reading resume position exactly coincides with the reading interruption position. However, in practice, even if the motor is controlled at a constant speed, the conveyance target is set at each of the reading interruption and reading resumption due to a control error. Since they do not travel at the same speed, there will be a gap between the reading restart position and the reading interruption position.

  When this deviation is accumulated, the reading length when the image reading operation for all lines is completed, that is, the image reading operation for all lines is completed, rather than the actual size of the reading area to be read. The length of the read image for all lines becomes longer or shorter in the image reading direction, and the image quality of the image data deteriorates.

  Therefore, in this embodiment, when the value | μ | exceeds the threshold value, the reading resume position is corrected in a direction in which the error μ converges to zero, assuming that a deviation occurs between the reading resume position and the reading interruption position. Like to do. That is, when the value | μ | exceeds the threshold value (No in S1230), the restart position setting unit 57 determines whether or not the error μ is equal to or less than zero, whereby the read length is equal to or less than the carry amount. It is determined whether or not (S1260).

  If the error μ is less than or equal to zero (Yes in S1260), a value X [0] is set to the variable restart_cnt, and this value is input to the forced synchronization command generation unit 59 (S1270), and the variable offset is set. Is set to 0, and this value is input to the forced synchronization command generation unit 59 (S1290), thereby setting the reading resume reference position to X [0] for the forced synchronization command generation unit 59 and the offset time. Is set to the value 0. Thereafter, the process shown in FIG. 16 ends.

  As a result, when the reading length is equal to or less than the carry amount, the restart position setting unit 57 lasts from the time TS including the time TS when the line start signal corresponding to the reading interruption line is input to the CCD line sensor 20. The point X [0] where the conveyance target exists at the time TP when the edge detection signal is input is set as the reading restart position, and the reading operation by the CCD line sensor 20 is restarted from this point (FIG. 18). (See (a)).

  On the other hand, when the reading length is larger than the carry amount and the error μ is larger than zero (No in S1260), the variable restart_cnt is set to the value X [1], and this value is input to the forced synchronization command generation unit 59. (S1280), a value 0 is set in the variable offset, and this value is input to the forced synchronization command generation unit 59 (S1290), so that the reading resumption reference position is set to X for the forced synchronization command generation unit 59. Set to [1] and set the offset time to value 0. Thereafter, the process shown in FIG. 16 ends.

  As a result, when the read length exceeds the carry amount, the restart position setting unit 57 starts the time when the edge detection signal is first input after the time TP when the edge detection signal is input last in the past from the time TS. The point X [1] where the conveyance target exists at TF is set as the reading resume position, and the reading operation by the CCD line sensor 20 is resumed from this point, and the reading is resumed in the direction in which the error μ converges to zero. The position is corrected (see FIG. 18B).

In this way, when the value | μ | exceeds the threshold value, the restart position setting unit 57 corrects the read restart position in a direction in which the error μ converges to zero.
For example, as shown in FIG. 18A, when the reading length read_l is shorter than the carry amount q_trans and the reading restart position is set to X [0], the reading restart position is before the true reading interruption position. It becomes.

  Similarly, as shown in FIG. 18B, when the reading length read_l is longer than the carry amount q_trans, if the reading resumption position is set to X [1], the reading resumption position is more than the true reading interruption position. The position advances in the image reading direction. Therefore, the error μ converges to zero.

Based on this principle, in this embodiment, when the error | μ | is small, the reading resume position is set so that the reading operation is resumed from the reading interruption position. When the error | μ | The reading restart position is set so as to converge to zero so that the image quality of the image data completed when the reading operation for all the lines is completed is not deteriorated by repeating the reading interruption operation.
(3.8) Details of Forced Synchronization Command Generation Unit 59 Next, details of the forced synchronization command generation unit 59 will be described with reference to FIGS. 19 and 20. FIG. 19 is a flowchart showing the processing executed by the forced synchronization command generation unit 59. The forced synchronization command generator 59 is for forcibly synchronizing the line start signal. When the reading function is activated, execution of the processing shown in FIG. 19 is started.

  When the forced synchronization command generation unit 59 starts the process shown in FIG. 19, every time an edge detection signal is input (Yes in S1410), the output value enc_cnt of the position counter 33 updated by the input of the edge detection signal is It is determined whether or not it matches the value (init_pos-1) immediately before the reading start position init_pos set in the register RG2 (S1420). If they do not match, the above determination is repeated and if they match (enc_cnt = init_pos-1: Yes in S1420), the process proceeds to S1430.

  Thereafter, when the edge detection signal is newly input (Yes in S1430), the forced synchronization command generation unit 59 determines that the conveyance target has reached the reading start position init_pos, and outputs a synchronization command to the line start trigger signal generation unit. 41a (S1440), and a line start signal is input to the CCD line sensor 20 at that time.

  20A and 20B are time charts showing the input mode of the synchronization command. When the reading start position init_pos = k is set, a synchronization command is sent to the line start trigger signal generation unit 41a when enc_cnt = k as shown in FIG. 20A by the processing of S1410 to S1440. And the input of the line start signal and the transfer clock signal to the CCD line sensor 20 is started by the reading front end 41 from the time when the conveyance target reaches the reading start position init_pos. In this way, the reading operation for each line is executed by the CCD line sensor 20 from the reading start position init_pos.

  However, the pixel signal output from the CCD analog shift register 20b during the period from when the line start signal is input to the CCD line sensor 20 until the next line start signal is input in response to the input of the synchronization command. Are discarded by the reading front end 41.

  When the input of the synchronization command is completed, the forced synchronization command generation unit 59 waits until a reading end signal or a reading restart command is input (S1450, S1455). When the reading end signal is input (Yes in S1450). ), The process ends.

  On the other hand, when the stop_sig signal transitions from the value 0 to the value 1, the process related to the reading function is interrupted, and when a reading restart command is input from the CPU 11 (Yes in S1455), the process proceeds to S1460.

  Each time the edge detection signal is input (Yes in S1460), the output value enc_cnt of the position counter 33 updated by the input of the edge detection signal is obtained from the reading restart reference position restart_cnt set by the restart position setting unit 57. It is determined whether or not the value matches the previous value (restart_cnt-1) (S1470). If the values do not match, the above determination is repeated, and if they match (enc_cnt = restart_cnt-1: Yes in S1470), the process proceeds to S1475. Transition.

  In S1475, the forced synchronization command generation unit 59 determines whether or not the offset time offset set by the resume position setting unit 57 is 0. If the offset time offset is 0 (Yes in S1475). ), The process proceeds to S1480. If the value is not 0 (No in S1475), the process proceeds to S1500.

  In S1480, the forced synchronization command generation unit 59 waits until a new edge detection signal is input. When a new edge detection signal is input (Yes in S1480), the conveyance target is read. Assuming that the start position (= reading resumption reference position restart_cnt) has been reached, a synchronization command is input to the line start trigger signal generation unit 41a, and a line start signal is input to the CCD line sensor 20 at that time (S1490). ).

  For example, when the reading restart reference position restart_cnt = k is set, the synchronization command is sent to the line start trigger signal when enc_cnt = k as shown in FIG. The input to the generation unit 41 a and the input of the line start signal and the transfer clock signal to the CCD line sensor 20 are started by the reading front end 41 from the time when the conveyance target reaches the reading restart reference position restart_cnt = k. .

  In this way, when the offset time is set to the value 0, the forced synchronization command generation unit 59 sends the line start signal to the CCD line sensor 20 from the time when the conveyance target reaches the reading restart reference position restart_cnt. Thus, the CCD line sensor 20 performs the reading operation for each line from the reading restart reference position restart_cnt.

When the input of the synchronization command is completed, the forced synchronization command generation unit 59 proceeds to S1450 and waits again until the reading resume command is input.
On the other hand, when the process proceeds to S1500, the forced synchronization command generation unit 59 waits until a new edge detection signal is input, and when a new edge detection signal is input (Yes in S1500), the elapsed time from that time point. Is started, and the system waits until the offset time offset set in advance by the restart position setting unit 57 has elapsed (S1510).

  When the offset time offset has passed (Yes in S1510), assuming that the conveyance target has reached the reading restart position, a synchronization command is input to the line start trigger signal generation unit 41a, and at that time, the CCD line sensor 20 A line start signal is input to the (S1520). When the input of the synchronization command is completed, the forced synchronization command generation unit 59 proceeds to S1450 and waits again until the reading resume command is input.

In this way, when the offset time is set to a value greater than 0, the forced synchronization command generation unit 59, after the conveyance target has reached the reading resume reference position restart_cnt, as shown in FIG. When the offset time offset has elapsed, a synchronization command is input so that the line start signal is periodically input to the CCD line sensor 20 from that point, and the CCD line sensor 20 starts from the reading interruption position. The reading operation for each line is executed. In response to the input of the synchronization command, the input of the transfer clock signal to the CCD line sensor 20 is started by the reading front end 41, and the pixel signal is output from the CCD analog shift register 20b to the reading front end 41.
(4) Effects of Image Reading Apparatus 1 The configuration of the image reading apparatus 1 of the present embodiment has been described above. According to the image reading apparatus 1, the error | μ | between the reading length and the carry amount is reduced. Thus, while the reading resume position is set, the offset time is set so that the reading is resumed from the reading interruption position while the error | μ | between the reading length and the carry amount is small. It is possible to generate high-quality read image data by matching the dimensions with the dimensions to be read. Therefore, according to the present embodiment, it is possible to provide the user with the image reading apparatus 1 that can generate high-quality image data that can be read at high speed.

  The reading unit of the present invention corresponds to the CCD line sensor 20, and the transport mechanism receives the rotational force of the reading motor MT1 and moves the CCD line sensor 20, and the rotational force of the read transport motor MT2. This corresponds to the ADF device 150 that moves the document to be read. The event generation signal output means corresponds to the reading encoder EN1 and the reading transport encoder EN2.

  Further, the reading control means is realized by the processing of S320 in the motor control section 39 and the reading control section 21, the interruption determining means is realized by the processing of S530 and S540 in the stop signal generating section 43d, and the stop control means is This is realized by the processing of S550 in the stop signal generation unit 43d.

  In addition, the position detection means is realized by the position counter 33, the first reference position setting means is realized by the process of S1240 in the restart position setting unit 57, and the offset setting means is realized by the process of S1250. Yes.

  The reading length detection unit is realized by the reading length calculation unit 53, the conveyance amount detection unit is realized by the conveyance amount calculation unit 51, and the second reference position setting unit is S1260 in the restart position setting unit 57. This is realized by the processing of S1280. In addition, the operation control means is realized by the processing of S1230.

Further, the backward control means is realized by the processing of S350 to S370 of the motor control unit 39, and the restart determination means is realized by the restart signal generation unit 43e.
(5) Others Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can take various forms.

  For example, in the above embodiment, the CCD line sensor 20 is used as the reading unit, but a contact image sensor (CIS: Contact Image Sensor) may be used as the reading unit. In addition, in this embodiment, a rotary encoder is used as the encoder EN1, but a linear encoder may be used instead of the rotary encoder.

  In addition, the image reading apparatus 1 of the above embodiment may be configured as a copying machine, a facsimile apparatus, or a multifunction machine having a scanner function.

2 is a block diagram illustrating an electrical configuration of the image reading apparatus 1. FIG. 2 is a cross-sectional view showing a mechanical configuration of the image reading apparatus 1. FIG. 4 is an explanatory diagram relating to a movement mode of the CCD line sensor 20. FIG. 3 is a block diagram illustrating configurations of an encoder processing unit 15 and a drive control unit 17. FIG. FIG. 6 is a flowchart (a) showing processing executed by the position counter 33 and an explanatory diagram (b) showing an operation mode of the period counter 35. FIG. 4 is a flowchart illustrating processing executed by a motor control unit 39. 3 is a block diagram illustrating a configuration of a reading control unit 21. FIG. 6 is an explanatory diagram relating to a data processing function realized by an image data processing unit 43. FIG. It is a flowchart showing the process which the stop signal production | generation part 43d performs. It is a flowchart showing the process which the restart signal production | generation part 43e performs. It is a flowchart showing the process which the drive stop command generation part 49 performs. It is a time chart showing the state of various signals before and after the time when the mtstop signal switches to the value 1. It is a flowchart showing the process which the conveyance amount calculation part 51 performs. 5 is a flowchart showing processing executed by a read length calculation unit 53. It is a flowchart showing the process which the time measurement part 55 performs. It is a flowchart showing the process which the restart position setting part 57 performs. It is explanatory drawing regarding the setting method of a reading resumption position. It is explanatory drawing regarding the setting method of a reading resumption position. It is a flowchart showing the process which the forced synchronous command generation part 59 performs. It is a time chart showing the input timing of a synchronous command.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image reading device, 11 ... CPU, 12 ... ROM, 13 ... RAM, 15 ... Encoder processing part, 17 ... Drive control part, 20 ... CCD line sensor, 20a ... Light receiving element group, 20b ... CCD analog shift register, 21 ... Reading control unit, 23 ... External interface, 31 ... Encoder edge detection unit, 33 ... Position counter, 35 ... Period counter, 37 ... Drive circuit, 39 ... Motor control unit, 41 ... Reading front end, 41a ... Line start trigger signal Generation unit 41b Line start signal generation unit 41c Transfer clock signal generation unit 41d A / D converter 43 Image data processing unit 43a Data writing unit 43b Image processing unit 43c Data Transfer unit, 43d ... stop signal generation unit, 43e ... restart signal generation unit, 45 ... local RAM, 45a ... buffer, 4 b ... processing data storage unit, 49 ... drive stop command generation unit, 51 ... transport amount calculation unit, 53 ... reading length calculation unit, 55 ... time measurement unit, 57 ... restart position setting unit, 59 ... forced synchronization command generation unit, 63: Memory controller, 101: Main body, 102: Stationary reading window, 102A, 103A ... Platen, 103 ... Automatic reading window, 104 ... Document cover, 106 ... Carriage, 107, 108 ... Pulley, 109 ... Belt, 111 ... Guide Axis 150 ... ADF device 153 ... separation roller 154 ... separation pad 155 ... suction roller 159 ... feed roller 160 ... pinch roller 161 ... document presser 162 ... discharge roller 164 ... document sensor actuator, 165 ... Document tray, 166 ... Discharge tray, EN1 ... Read encoder, EN2 ... Read transport encoder, MT1 ... Read Motor, MT2 ... reading transport motor, RG1~RG3 ... register

Claims (5)

A reading unit for reading image information to be read; and
A transport mechanism that includes a DC motor, and transports one of the reading unit and the reading target as a transport target by the driving force of the DC motor;
By controlling the moving speed of the conveyance object through the conveyance mechanism, moving the conveyance object at a constant speed in the image reading direction, and periodically inputting a line start signal to the reading unit. The unit designates the reading start timing of the line image, performs the reading operation for each line, causes the reading unit to generate the read image data of each line, and writes the generated read image data to the buffer Reading control means for executing processing;
Interruption determination means for determining whether or not the processing by the reading control means is interrupted;
When it is determined by the interruption determination unit that the processing by the reading control unit needs to be interrupted, a stop control unit that interrupts the processing by the reading control unit;
An event occurrence signal output means for outputting an event occurrence signal each time the transport object moves by a predetermined amount;
Based on the event occurrence signal input from the event occurrence signal output means, position detection means for detecting the current position of the conveyance target;
The event occurred last in the past from the time TS including the time TS at which the line start signal corresponding to the line for which the processing by the reading control means was interrupted by the operation of the stop control means was input to the reading unit. First reference position setting means for setting the position XP detected by the position detection means at the time point TP when the event occurrence signal is input from the signal output means as a reading restart reference position;
An offset setting means for setting an offset time based on an elapsed time from the time TP to the time TS;
A reading length detecting means for detecting a reading length which is a length in the image reading direction of the read image data from a leading line to a reading completion line where the reading operation by the reading unit is completed at the time TS;
The length from the position detected by the position detection means at the start of reading the head line to the position XP detected by the position detection means at the time TP is the line from the head line to the read completion line. As a conveyance amount of the reading unit required for reading an image, a conveyance amount detection means for detecting,
Based on an error between the transport amount detected by the transport amount detection unit and the read length detected by the read length detection unit, a position XP detected by the position detection unit at the time TP, and A second reference that selectively sets any one of the positions XF detected by the position detecting means at the time TF when the event occurrence signal is first input after the time TP has elapsed, as a reading resume reference position Position setting means;
Based on the error, an operation control means for selectively operating one of the first and second reference position setting means;
When the processing by the reading control unit is interrupted by the operation of the stop control unit, the conveyance target is moved in the direction opposite to the image reading direction through the conveyance mechanism to a position advanced from the reading resumption reference position. Retreat control means to move,
Resumption determination means for determining whether or not resumption of the processing by the reading control means is required during a period when the processing by the reading control means is suspended;
With
When the reading control unit determines that the restart determination unit needs to restart, the reading control unit moves the conveyance object moved by the retreat control unit again in the image reading direction at a constant speed, and When the reading resumption reference position is set by the first reference position setting means based on the detection result of the position detection means, the offset setting means starts from the time when the conveyance target reaches the reading resumption reference position. When the set offset time has elapsed, a line start signal is input to the reading unit, and when the reading resumption reference position is set by the second reference position setting means, the conveyance target is resumed reading. When the reference position is reached, a line start signal is input to the reading unit, and after the line start signal is input, the line start signal is periodically input. By inputting the emission start signal, the image reading apparatus characterized by being the read image data generated, to resume configuration process to write to the buffer by the reading unit.   The second reference position setting means sets the position XP as the reading restart reference position when the reading length detected by the reading length detection means is shorter than the conveyance amount detected by the conveyance amount detection means. When the reading length detected by the reading length detection unit is longer than the conveyance amount detected by the conveyance amount detection unit, the position XF is set as the reading restart reference position. The image reading apparatus according to claim 1, wherein:   The operation control means selectively activates the first reference position setting means when the absolute value of the error is less than a threshold value, and when the absolute value of the error is equal to or greater than the threshold value, 3. The image reading apparatus according to claim 1, wherein the second reference position setting means is selectively operated.   4. The image reading according to claim 1, wherein the offset setting unit is configured to set an elapsed time from the time point TP to the time point TS as the offset time. 5. apparatus.   The said interruption determination means is comprised by the structure which determines the necessity of interruption of the process by the said reading control means based on the free capacity of the said buffer. Image reading device.