JP4748135B2 - Image reading device - Google Patents

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, the image quality of the image data may deteriorate due to a deviation between the reading interruption position and the reading restart position.
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 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 correct position can be known only with the accuracy corresponding to the predetermined amount δ with respect to the point where the conveyance target is present when the line start signal corresponding to the line where the reading is interrupted is input. Disappear. Therefore, a deviation occurs between the reading interruption position and the reading resumption position, and in the conventional technique, the image represented by the image data becomes a stretched or crushed image with respect to the reading target, and the image quality deteriorates. It ends up.

  The present invention has been made in view of these problems, and provides an image reading apparatus capable of generating high-quality image data corresponding to a reading target while suppressing a deviation between a reading interruption position and a reading restart position. The purpose is to do.

  In order to achieve the above object, an image reading apparatus according to the present invention (Claim 1) includes a reading unit that reads image information to be read, and either a reading unit or a reading object by a driving force of a DC motor. Through the transport mechanism that transports as a transport target, the transport speed of the transport target is controlled through the transport mechanism, the transport target is moved at a constant speed in the image reading direction, and a line start signal is periodically input to the reading unit. Thus, the reading 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 stores the generated read image data in the buffer. Read control means for executing a process of writing data into the data.

  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 restart position setting unit, a reverse control unit, and a restart determination unit. The determination unit determines whether or not the processing by the reading control unit is interrupted. When it is determined that the interruption is necessary, the stop control unit interrupts the processing by the reading control unit. The interruption determination means can be configured to determine whether or not it is necessary to interrupt the processing by the reading control means based on the free capacity of the buffer.

  Further, in this image reading apparatus, 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. The current position of the conveyance target is detected. As the event generation signal output means, the encoder described above can be used.

  In addition, the restart position setting means is configured such that the event TS has a point in time before “the line start signal corresponding to the line for which the processing by the reading control means is interrupted by the operation of the stop control means is input to the reading unit”, and past the time TS. The time TP when the event occurrence signal is last input from the generation signal output means (however, the time TP mentioned here may or may not include the time TS), and after the elapse of the time TP, Of the position XP detected by the position detecting means at the time TP and the position XF detected by the position detecting means at the time TF based on the temporal relationship with the time TF when the event occurrence signal is input to Either one is selectively set as a reading resume position.

  In addition, when the processing by the reading control unit is interrupted by the operation of the stop control unit, the retreat control unit sets the conveyance target through the conveyance mechanism in the direction opposite to the image reading direction by the resume position setting unit. Move to a position advanced from the reading resume position. The resumption determination unit determines whether or not the resumption of the processing by the reading control unit is necessary during the period when the processing by the reading control unit is interrupted.

  When it is determined by the restart determining means that the restart is necessary, the reading control means again moves the conveyance object moved by the backward control means in the image reading direction at a constant speed, and the position detecting means. The line start signal is input to the reading unit when the conveyance target reaches the reading restart position set by the restart position setting means based on the detection result of the above, and thereafter the line start signal is periodically input thereafter. Then, from the reading restart position, the reading unit is caused to execute a reading operation, and the read image data generated by the reading unit is written into the buffer.

  According to the image reading apparatus that operates in this manner, based on the temporal relationship between the time point TS and the time point TP and the time point TF that sandwich the time point TS, there was a conveyance target at the time point TS among the positions XP and XF. Since the position closer to the reading interruption position can be selected and the reading resumption position can be set, the deviation between the reading interruption position and the reading resumption position can be suppressed, and image data with good image quality can be generated.

  Specifically, the image reading apparatus measures the time length LP from the time point TP to the time point TS and the time length LF from the time point TS to the time point TF, and the measured time length LP and time length LF. Based on the relationship, the reading resumption position can be set (claim 2).

  Further, when the time length LP is shorter than the time length LF, the restart position setting means sets the position XP detected by the position detection means at the time TP as the reading resume position, and the time length LP is the time length. In the case where it is longer than LF, the position XF detected by the position detection means at the time TF can be set as the reading restart position (claim 3). As described above, according to the image reading apparatus in which the restart position setting unit is configured as described above, it is possible to suppress the deviation between the reading interruption position and the reading restart position and generate image data with good image quality.

  However, in the image reading apparatus that measures the time length LF, the conveyance target cannot be decelerated and reversed until the time length LF is measured even after the interruption of reading is confirmed. That is, based on the relationship between the time length LP and the time length LF, in order to correctly evaluate the distance relationship between the reading interruption position and the positions XP and XF, the conveyance target between them is a constant speed. If it is necessary and deceleration is started at the time TS, the distance relationship cannot be correctly evaluated.

Therefore, when the conveyance target is decelerated and reversed immediately after the elapse of time TS, the image reading apparatus may be configured as follows.
That is, the image reading apparatus includes input time interval detection means for detecting the input time interval LI of the event occurrence signal based on the event occurrence signal input from the event occurrence signal output means, It may be configured to include time length detection means for detecting a time length LP between the time point TP and the time point TS when the event occurrence signal is last input from the signal output means.

  At this time, the restart position setting means is based on the relationship between the time length LP detected by the time length detection means and the input time interval LI of the event occurrence signal detected by the input time interval detection means at the time TP. The position XP detected by the position detection means at the time TP and the position XF detected by the position detection means at the time TF when the event occurrence signal is first input after the time TP has elapsed are selectively selected. In addition, it is possible to adopt a configuration in which the reading is resumed (claim 4).

  Since the conveyance target is controlled at a constant speed until the time point TS, if the image reading apparatus is configured in this way, the time length LF from the time point TS to the time point TF is obtained from the relationship between the time interval LI and the time length LP. Can be estimated. Therefore, according to this image reading apparatus, it is possible to select a position closer to the reading interruption position where the conveyance target is located at the time TS among the positions XP and XF, and set the reading resumption position. The deviation from the reading restart position can be suppressed, and image data with good image quality can be generated.

  In the case of configuring the image reading apparatus in this way, when the time length LP is smaller than one half of the input time interval LI, the position XP detected by the position detecting means at the time TP is set as the reading resume position. When the time length LP is greater than one half of the input time interval LI, the restart position setting means is configured to set the position XF detected by the position detection means at the time TF as the reading restart position. Thus, it is possible to suppress the deviation between the reading interruption position and the reading resumption position with high accuracy and generate image data with good image quality.

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. The encoder processing unit 15 that executes the processing based on the above and an external interface 23 are configured to be communicable with an external device (such as a personal computer) via the external interface 23. An example of the external interface 23 is a USB 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. 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 activated, and reads the image under the platen 102A on which the document is placed. The image information of the original is read for each line along with the movement.

  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 on 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 a reading motor MT1 constituted by a DC motor is connected to the belt 109 via a gear. It 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 a document is not placed on the document tray 165 is 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. These sets are configured to detect the amount of rotation of the motors MT1 and MT2 in which the encoders EN1 and EN2 are installed, and consequently, the amount of movement of the conveyance target.

  Specifically, the encoder edge detection unit 31 of the encoder processing unit 15 is configured to detect rising edges of the corresponding encoders EN1 and EN2, and to output an edge detection signal each time this edge is detected. 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 51, the restart position setting unit 55, and the forced synchronization command generating unit 59 included in the reading control unit 21.

  Further, 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 and when the stationary document reading function is activated. The time is input to the time measuring unit 51 of the reading control unit 21. The value enc_cnt output from the position counter 33 for the reading encoder EN1 is also input to the forced synchronization command generation unit 59 of the reading control unit 21 when the stationary document reading function is activated.

  Further, the edge detection signal output from the encoder edge detector 31 for the read and transport encoder EN2 to which the pulse signal from the read and transport encoder EN2 is input is input to the position counter 33 and the period counter 35 for the read and transport encoder EN2. At the same time, when the automatic conveyance reading function is activated, it is input to the drive stop command generation unit 49, the time measurement unit 51, the restart position setting unit 55, and the forced synchronization command generation 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 and the automatic transporting and reading function. At the time of operation, it is input to the time measuring unit 51 of the reading control unit 21. Further, the value enc_cnt output from the position counter 33 for the reading and transporting encoder EN2 is also input to the forced synchronization command generating unit 59 of the reading control unit 21 when the automatic transporting and reading function is activated.

  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 detected moving time represents the speed, and the drive control unit 17 controls the motor to be controlled using this speed information.

  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.

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. The position detection can be performed using the A phase signal of the encoder, and the rotation direction can be detected using the B phase signal of the encoder.
(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.

  When the mtstop signal is switched to the value 1, a process of decelerating and stopping the motor to be controlled is performed (S350). Further, 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 reading restart position restart_cnt described later. 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 generation unit 49, a time measurement unit 51, a restart position setting unit 55, and a forced synchronization command. The generation unit 59 is provided as a constituent element, and reading control unique to the present invention is realized by 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.

  The line start trigger signal generator 41a starts outputting the line start trigger signal when the reading function is activated, and thereafter periodically outputs the line start trigger signal. In addition, 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 a state of waiting for the synchronization command from the forced synchronization command generation unit 59, and then the forced synchronization command. It waits until it receives the synchronous command from the production | generation part 59. FIG. When the synchronization command is received from the forced synchronization command generator 59, the output of the line start trigger signal is restarted at the command input timing, and thereafter the line start trigger signal is periodically output.

  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 41 a to the time measurement unit 51.
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 in the memory is output as a pixel signal, and then the output of the transfer clock signal is stopped.

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.
(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 then reaches the reading end line 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 reading end line is completed (Yes in S520), a reading end signal is output to notify each unit of the end of reading (S560), and then FIG. The process shown in FIG.

  On the other hand, when the acquisition of the line image data up to the reading end line is not completed (No in S520), it is determined whether or not the free capacity rem_buf of the buffer 45a is equal to or less 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 space 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 read end line that needs to be written is It is determined whether the total capacity rem_lin is equal to or less than the free capacity rem_buf (Yes in S540), and it is assumed that the buffer 45a does not become full by 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, and the restart position setting unit 55.

  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 generation unit 43e first sets the restart_sig signal to a value of zero (S610), and then reads the reading end line 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 up to is completed (S620). If the acquisition of the line image data up to the reading end line has been completed (Yes in S620), the process is paused.

  On the other hand, when the acquisition of the line image data up to the reading end line is not 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 changed from the value zero to the 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 line image data up to the reading end line that needs to be written in the future in the free capacity rem_buf of the buffer 45a. Whether or not the free capacity rem_buf is greater than or equal to the total amount rem_lin (Yes in S640), it is determined that the free capacity rem_buf of the buffer 45a is sufficient for restarting and restart_sig. The signal 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. While executing from S310, a reading resumption command is input to the resumption position setting unit 55 and the forced synchronization command generation unit 59 to operate the resumption position setting unit 55 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.

The motor control unit 39 decelerates the motor when the mtstop signal is switched to the value 1. However, since the mtstop signal changes its state in synchronization with the edge detection signal, the motor control unit 39 controls the motor deceleration. 12 is started when a pulse edge is input from the encoder after the stop_sig signal changes state to a value of 1, as shown in FIG. 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 Time Measurement Unit 51 Next, details of the time measurement unit 51 will be described with reference to FIG. FIG. 13A is a flowchart showing a first measurement process executed by the time measurement unit 51, and FIG. 13B is a second measurement process executed by the time measurement unit 51 in parallel with the first measurement process. It is a flowchart showing.

  The time measurement unit 51 outputs the values of the variable time_p, the variable time_f, and the variable position, which are necessary for setting the reading restart position (restart_cnt) to the restart position setting unit 55. The first and second measurement processes are started, and the values of the variable time_p, the variable time_f, and the variable position are updated.

  The time measuring unit 51 includes first and second time counters, and uses these time counters to execute the first and second measurement processes to measure time. The time measuring unit 51 is also configured to input a status signal indicating whether or not the second time counter is measuring time to the restart position setting unit 55, and the second time counter is measuring time. When the second time counter is stopped, the value 0 is output as the status signal.

  When the first measurement process is started, the time measurement unit 51 determines whether or not a reading end signal is input from the image data processing unit 43 (S910), and when the reading end signal is not input (S910). No), it is determined whether an edge detection signal is input (S920). If no edge detection signal is input (No in S920), it is determined whether a line start trigger signal is input. Judgment is made (S930).

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 S920), the time measurement by the first time counter is started (S925), and the first time counter is caused to measure the elapsed time from the input time of the edge detection signal. Prior to the start of timing, the value CN1 of the first timing counter is reset to zero. When the timing is started, the process proceeds to S930, and it is determined whether or not a line start trigger signal is input (S930). If the line start trigger signal is not input (No in S930), the process proceeds to S910. If it is input (Yes in S930), the process proceeds to S935.

  When the line start trigger signal is input (Yes in S930), the time measuring unit 51 sets the value CN1 of the first time counter to the variable time_p (S935), and finally the edge detection signal is input. Information on the time required from when the line start trigger signal is input until the line start trigger signal is input is held in the variable time_p. Thereafter, the process proceeds to S910, and waits until any of the reading end signal, the edge detection signal, and the line start trigger signal is input.

Then, when the reading end signal is input (Yes in S910), the first measurement process is ended, assuming that reading of the reading target (reading of one original) has been completed.
Similarly, when the second measurement process is started, the time measurement unit 51 determines whether or not the reading end signal is input from the image data processing unit 43 (S950), and when the reading end signal is not input. (No in S950), it is determined whether or not the line start trigger signal is input (S960). If the line start trigger signal is not input (No in S960), the edge detection signal is input. It is determined whether or not there is (S970).

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 line start trigger signal is input (Yes in S960), the time measurement by the second time counter is started (S990), and the elapsed time from the input time of the line start trigger signal is measured by the second time counter. Let Prior to the start of timing, the value CN2 of the second timing counter is reset to zero. At the same time, the status signal is switched to the value 1 (S995). Thereafter, the process proceeds to S950 and waits until any of a reading end signal, an edge detection signal, and a line start trigger signal is input.

  On the other hand, when the edge detection signal is input (Yes in S970), the time measuring unit 51 determines whether or not the status signal has a value of 1 (S980), and if the value is 1 (Yes in S980), The time counting by the second time counter is stopped (S981), and the value CN2 of the second time counter is set to the variable time_f (S983).

  At the same time, the time measuring unit 51 stores and holds the position of the conveyance target at the time of input of the edge detection signal by setting the value enc_cnt updated by the position counter 33 by the input of the edge detection signal to the variable position. (S985). Further, the status signal is switched to the value 0 (S987). Thereafter, the process proceeds to S950 and waits until any of a reading end signal, an edge detection signal, and a line start trigger signal is input. On the other hand, when the status signal is not 1 (No in S980), the time measuring unit 51 proceeds to S950 without executing the processes of S981 to S987.

Further, when the reading end signal is input from the image data processing unit 43 (Yes in S910), the time measuring unit 51 ends the second measuring process.
In this way, the time measurement unit 51 receives the edge detection signal 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, as shown in FIG. The time length time_p from when the line start trigger signal is input until the line start trigger signal is input and the time length time_f from when the line start trigger signal is input until the edge detection signal is input are measured and restarted. Output to the position setting unit 55. FIG. 14 is an explanatory diagram showing time lengths time_p and time_f.
(3.5) Details of Restart Position Setting Unit 55 Next, details of the restart position setting unit 55 will be described with reference to FIG. FIG. 15 is a flowchart showing processing executed by the restart position setting unit 55.

  When the value 1 is input as the stop command signal (stop_sig) from the image data processing unit 43, the restart position setting unit 55 sets the read restart position (restart_cnt) for the reading operation to be restarted thereafter. restart_cnt is input to the forced synchronization command generation unit 59. Specifically, the resumption position setting unit 55 starts executing the processing shown in FIG. 15 when the reading function is activated, and also performs the processing shown in FIG. 15 when a reading resumption command is input from the CPU 11. Start execution.

  When this process is started, the restart position setting unit 55 first waits until the stop_sig signal transitions from the value 0 to the value 1 (S1110), and when the stop_sig signal transitions to the value 1 (Yes in S1110), at that time. Then, it is determined whether or not the second time counter is stopped by determining whether or not the status signal input from the time measurement unit 51 is 0 (S1120). If the status signal is 1 (No in S1120), the process waits until the status signal becomes 0.

  If it is determined that the status signal has a value of 0 (Yes in S1120), the process proceeds to S1130, where the value position input from the time measuring unit 51 is set to the variable X [1] and the variable X [0] is set to X [0] = position-1. Further, the value time_p input from the time measuring unit 51 is set to the variable L [0], and the value time_f is set to the variable L [1].

  When this process is completed, the restart position setting unit 55 determines whether or not the value L [0] is equal to or smaller than the value L [1] (S1140), and L [0] ≦ L [1]. (Yes in S1140), a value X [0] is set in the variable restart_cnt, and this value is input to the forced synchronization command generation unit 59 (S1150). As a result, the reading resume position restart_cnt is in the past from the time TS when the line start signal corresponding to the reading interruption line is input to the CCD line sensor 20, and the transport target exists at the time TP when the edge detection signal is last input. Set to a point. For example, when the line start signal is input to the CCD line sensor 20 at the timing shown in FIG. 16A and the stop_sig signal transitions to the value 1 at or after the input time, L [0] ≦ L [1 ], The reading restart position restart_cnt is set to the position X [0]. Then, when the processing in S1150 is finished, the processing is finished.

  On the other hand, when the restart position setting unit 55 determines that L [0]> L [1] (No in S1140), the restart position setting unit 55 sets a value X [1] to the variable restart_cnt and uses this value as the forced synchronization command generation unit. 59 (S1160), the reading restart position restart_cnt is set next to the edge detection signal last input in the past from the time TS when the line start signal corresponding to the reading interruption line is input to the CCD line sensor 20. Is set to a point where the conveyance target exists at the input time point TF of the edge detection signal input to.

For example, when the line start signal is input to the CCD line sensor 20 at the timing shown in FIG. 16B and the stop_sig signal transitions to the value 1 at or after the input time, L [0]> L [1 ], The reading restart position restart_cnt is set to the position X [1]. Then, when the process in S1160 ends, the process ends.
(3.6) 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. 17 and 18. FIG. 17 is a flowchart showing the process executed by the forced synchronization command generation unit 59. The forced synchronization command generation unit 59 is for forcibly synchronizing the line start signal when restarting the reading operation. When a reading restart command is input from the CPU 11, the processing shown in FIG. To start.

  When the forced synchronization command generation unit 59 starts the processing shown in FIG. 17, 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 coincides with a value (restart_cnt-1) immediately before the reading restart position restart_cnt (S1420). If not coincident, the above determination is repeated. Yes), 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 restart position restart_cnt, and issues a synchronization command to the line start trigger signal generation unit. The line start signal is input to the CCD line sensor 20 at that time. When the input of the synchronization command is completed, the forced synchronization command generation unit 59 pauses until the reading restart command is input again.

  FIG. 18 is a time chart showing an input mode of the synchronization command when the reading operation is interrupted and the reading restart position is set to restart_cnt = k in the mode shown in FIG.

  In this way, the forced synchronization command generation unit 59 causes the line start signal to be periodically input to the CCD line sensor 20 from the time when the conveyance target reaches the reading restart position restart_cnt, and from the reading restart position restart_cnt. The reading operation for each line is executed by the CCD line sensor 20.

Further, the forced synchronization command generation unit 59 causes the reading front end 41 to start inputting the transfer clock signal to the CCD line sensor from the time when the reading restart position restart_cnt is reached by the input of the synchronization command, and the CCD analog shift register. A pixel signal is outputted from the reading front end 41 from 20b. 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.
(4) Effects of Image Reading Device 1 The configuration of the image reading device 1 of the present embodiment has been described above. According to the image reading device 1, the time point TS, the time point TP and the time point TF sandwiching the time point TS, Based on the temporal relationship, the position XP and the position XF that are closer to the reading interruption position where the conveyance target was at the time TS are selected, and the reading resumption position is set.

  Specifically, the time length L [0] from the time point TP to the time point TS and the time length L [1] from the time point TS to the time point TF are measured, and the time length L [0] is the time length. If it is less than or equal to L [1], the position X [0] detected by the position counter 33 at the time TP is set as the reading restart position, and the time length L [0] is greater than the time length L [1]. If larger, the position X [1] detected by the position counter 33 at the time TF is set as the reading restart position.

Therefore, according to the image reading apparatus 1, it is possible to suppress the deviation between the reading interruption position and the reading resumption position and to generate image data with good image quality.
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 detecting means is realized by the position counter 33, the time measuring means is realized by the time measuring section 51, the restart position setting means is realized by the restart position setting section 55, and the reverse control means is This is realized by the processing of S350 to S370 of the motor control unit 39.
(5) Modified Example Next, the configuration of the image reading apparatus 1 according to a modified example will be described. However, in the image reading apparatus 1 of the modification, the time measurement unit 51 is configured to execute the measurement process shown in FIG. 19 instead of the first and second measurement processes shown in FIG. However, instead of the process shown in FIG. 15, the process is configured to execute the process shown in FIG. 20, and in the following, as a description of the image reading apparatus 1 of the modification, FIGS. 19 to 21 will be used. A configuration different from the above embodiment will be described selectively.
(5.1) Details of Time Measurement Unit 51 FIG. 19 is a flowchart showing measurement processing executed by the time measurement unit 51 in the modification.

  The time measuring unit 51 in the image reading apparatus 1 according to the modification outputs values of the variable time_p, the variable position, and the variable interval to the restart position setting unit 55, and starts the measurement process when the reading function is activated. The values of the variable time_p, the variable position, and the variable interval are updated. The time measuring unit 51 has a built-in time counter, and uses these time counters to execute a measurement process and measure time.

  When this measurement process is started, the time measurement unit 51 determines whether or not a reading end signal is input from the image data processing unit 43 (S1510). If the reading end signal is not input (S1510). No), it is determined whether an edge detection signal is input (S1520). If no edge detection signal is input (No in S1520), it is determined whether a line start trigger signal is input. (S1530).

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 S1520), the time counter starts counting (S1525), 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 S1530, 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 S1530), the process proceeds to S1510. If the line start trigger signal is input (Yes in S1530), the process proceeds to S1540.

  When the line start trigger signal is input (Yes in S1530), the time measurement unit 51 sets the value CN of the time counter to the variable time_p (S1540), and finally the edge detection signal is input. Is stored in the variable time_p, and the value enc_cnt input from the position counter 33 is set in the variable position to set the value of the edge detection signal. The position of the conveyance target at the time of input is stored and held (S1550).

  Furthermore, by setting the value enc_cyc input from the period counter 35 to the variable interval, the input time interval of the edge detection signal immediately before the line start signal input time is stored and held (S1560).

In addition, when the processing up to S1560 is completed in this way, the time measurement unit 51 proceeds to S1510 and again receives any of the reading end signal, the edge detection signal, and the line start trigger signal. stand by. Then, when the reading end signal is input from the image data processing unit 43 (Yes in S1510), the measurement process is ended.
(5.2) Details of Restart Position Setting Unit 55 Next, details of the restart position setting unit 55 of the modification will be described with reference to FIG. FIG. 20 is a flowchart showing the process executed by the resume position setting unit 55.

  When the process shown in FIG. 20 is started, the restart position setting unit 55 first waits until the stop_sig signal transitions from the value 0 to the value 1 (S1610), and when the stop_sig signal transitions to the value 1 (Yes in S1610), At that time, the value position input from the time measuring unit 51 is set to the variable X [0], and the variable X [1] is set to X [1] = position + 1. Further, the value time_p input from the time measuring unit 51 is set to the variable L [0], and the value interval is set to the variable LI (S1620).

  When the stop_sig signal is switched to the value 1 at the same time as the line start trigger signal is generated, the value time_p updated by the time measuring unit 51 by the line start trigger signal (line start trigger signal corresponding to the reading interruption line). , Position, interval values, variables X [0], X [1], and LI are set.

  When this process is finished, the restart position setting unit 55 determines whether or not the value L [0] is equal to or less than the value (LI−L [0]) (S1630), and L [0] ≦ (LI -L [0]) (Yes in S1630), the value X [0] is set in the variable restart_cnt, and this value is input to the forced synchronization command generation unit 59 (S1640), and the reading resume position The restart_cnt is set to a point where the conveyance target exists at the time TP when the edge detection signal is last input before the time TS when the line start signal corresponding to the reading interruption line is input to the CCD line sensor 20.

  For example, when the line start signal is input to the CCD line sensor 20 at the timing shown in FIG. 21A and the stop_sig signal transitions to the value 1 at or after the input time, L [0] ≦ LI−L Since it is [0], the reading restart position restart_cnt is set to the position X [0]. Then, when the processing in S1640 is finished, the processing is finished.

  On the other hand, when the restart position setting unit 55 determines that L [0]> (LI−L [0]) (No in S1630), the restart position setting unit 55 sets a value X [1] to the variable restart_cnt and forces this value. Input to the synchronization command generation unit 59 (S1650), the resumption position restart_cnt is set as the edge detection signal last input in the past from the time TS when the line start signal corresponding to the reading interruption line is input to the CCD line sensor 20. , The edge detection signal input next to is set at the point where the conveyance target exists at the input time point TF.

For example, when the line start signal is input to the CCD line sensor 20 at the timing shown in FIG. 21B and the stop_sig signal transitions to the value 1 at or after the input time, L [0]> L (LI -L [0]), the reading restart position restart_cnt is set to the position X [1]. Then, when the processing in S1650 is finished, the processing is finished.
(5.3) Summary of Modifications The image reading apparatus 1 of the modification has been described above. According to the image reading apparatus 1 of the modification, the speed of the conveyance target is substantially constant, Based on the time length L [0] from the time point TP to the time point TS and the input time interval interval of the edge detection signal at the time point TP, the time length L [1] from the time point TS to the time point TF is set to L [ 1] = LI−L [0], and based on these L [0] and L [1], the reading restart position restart_cnt is set by the same method as in the first embodiment.

Therefore, similarly to the above-described embodiment, it is possible to suppress the deviation between the reading interruption position and the reading restart position and generate image data with good image quality.
In the present embodiment, the time length time_f need not be measured, so there is no need to wait for the motor to decelerate until time_f is measured. Therefore, the drive stop command generation unit 49 can set the mtstop signal to the value 1 without waiting for the input of the edge detection signal (S860) when the stop_sig signal transits to the value 1 (S840). As described above, if the image reading apparatus 1 is configured, the motor can be quickly decelerated and the conveyance target can be stopped.

  In the modification, it is determined whether or not L [0] ≦ (LI−L [0]) in S1630. However, in S1630, L [0] ≦ (LI / 2). It may be determined whether or not. Even in this case, the same operation can be realized, and the deviation between the reading interruption position and the reading resumption position can be suppressed, and image data with good image quality can be generated.

In the modification, the time length detection means of the present invention is realized by the processing of S1620 executed by the time measurement unit 51 and the restart position setting unit 55, and the input time interval detection means is realized by the period counter 35. Has been.
(6) 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 the flowchart (a) showing the 1st measurement process which the time measurement part 51 performs, and the flowchart (b) showing the 2nd measurement process. It is explanatory drawing showing time length time_p and time_f. It is a flowchart showing the process which the restart position setting part 55 performs. 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. It is a flowchart showing the measurement process which the time measurement part 51 of a modification performs. It is a flowchart showing the process which the restart position setting part 55 of a modification performs. It is explanatory drawing regarding the setting method of the reading restart position in a modification.

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 ... Time measurement unit, 55 ... Restart position setting unit, 59 ... Forced synchronization command generation unit, 63 ... Memory controller, 101 ... Main unit, 102 ... Static reading Window, 102A, 103A ... Platen, 103 ... Automatic reading window, 104 ... Document cover, 106 ... Carriage, 107, 108 ... Pulley, 109 ... Belt, 111 ... Guide shaft, 150 ... ADF device, 153 ... Separation roller, 154 ... Separation pad, 155... Suction roller, 159 .. feed roller, 160... Pinch roller, 161 .. document press, 162 .. discharge roller, 164 .. document sensor actuator, 165. Encoder, EN2 ... Reading transport encoder, MT1 ... Reading motor, MT2 ... Reading transport motor

Claims (6)

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 time TS when the line start signal corresponding to the line for which the processing by the reading control means is interrupted by the operation of the stop control means is input to the reading unit, and the event occurrence signal output means before the time TS Based on the temporal relationship between the time point TP when the event occurrence signal was last input and the time point TF when the event occurrence signal was first input after the elapse of the time point TP, the position at the time point TP A restart position setting means for selectively setting any one of the position detected by the detection means and the position detected by the position detection means at the time TF to the reading restart position;
When the processing by the reading control unit is interrupted by the operation of the stop control unit, the reading target set by the resume position setting unit is set in the direction opposite to the image reading direction through the transport mechanism. Retreat control means for moving to a position advanced from the position;
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 Based on the detection result of the position detection means, when the conveyance object reaches the reading restart position set by the restart position setting means, a line start signal is input to the reading unit. Inputting a start signal causes the reading unit to execute a reading operation from the reading restart position, and executes processing for writing the read image data generated by the reading unit into a buffer. Reader. A time measuring means for measuring a time length LP from the time point TP to the time point TS and a time length LF from the time point TS to the time point TF;
The restart position setting means is configured to set the reading restart position based on the relationship between the time length LP and the time length LF measured by the time measuring means. The image reading apparatus according to claim 1. When the time length LP is shorter than the time length LF, the resumption position setting means sets the position detected by the position detection means at the time TP as the reading resumption position, and the time length LP 3. The image reading apparatus according to claim 2, wherein when the time length LF is longer than the time length LF, the position detected by the position detection unit at the time point TF is set as the reading restart position. . 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 time TS when the line start signal corresponding to the line for which the processing by the reading control means is interrupted by the operation of the stop control means is input to the reading unit, and the event occurrence signal output means before the time TS A time length detecting means for detecting a time length LP from the time point TP when the event occurrence signal is last input to
Input time interval detection means for detecting an input time interval LI of the event occurrence signal based on an event occurrence signal input from the event occurrence signal output means;
Based on the relationship between the time length LP detected by the time length detection means and the input time interval LI of the event occurrence signal detected by the input time interval detection means at the time TP, the time point Select one of the position detected by the position detecting means at TP and the position detected by the position detecting means at the time TF when the event occurrence signal is first input after the time TP has elapsed. In particular, restart position setting means for setting the reading restart position,
When the processing by the reading control unit is interrupted by the operation of the stop control unit, the reading target set by the resume position setting unit is set in the direction opposite to the image reading direction through the transport mechanism. Retreat control means for moving to a position advanced from the position;
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 Based on the detection result of the position detection means, when the conveyance object reaches the reading restart position set by the restart position setting means, a line start signal is input to the reading unit. Inputting a start signal causes the reading unit to execute a reading operation from the reading restart position, and executes processing for writing the read image data generated by the reading unit into a buffer. Reader. The restart position setting means sets the position detected by the position detection means at the time TP as the reading restart position when the time length LP is smaller than one half of the input time interval LI, When the time length LP is larger than one half of the input time interval LI, the position detected by the position detection means at the time point TF is set as the reading restart position. The image reading apparatus according to claim 4.   6. The interrupt determination unit according to claim 1, wherein the interrupt determination unit is configured to determine whether or not the processing by the reading control unit is interrupted based on a free space of the buffer. Image reading device.