JP2008092057A - Image reader and image reading method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a processing speed by properly setting a moving speed of an image reading sensor. <P>SOLUTION: An image reader is provided with an image reading sensor for reading an image from an original document; a motor for relatively moving the image reading sensor to the original document when the image reading sensor reads the image from the original document; and a motor controller for controlling the motor so that the image reading sensor can repeat moving and stopping every time the image reading sensor reads one line of the image from the original document when it reads the image from the original document, and changing setting of the value of a current for controlling the motor on the basis of a time required for the image reading sensor to move for one line. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image reading apparatus and an image reading method.

Various image reading apparatuses such as an image scanner include an image reading sensor such as an image sensor for reading an image from a document. The image reading sensor moves relative to the document when reading an image from the document. For this reason, various image reading apparatuses are provided with a motor for moving the image reading sensor. Recently, a DC motor has been used as this motor (see Patent Document 1).
JP 2001-219613 A

  By the way, in such an image reading apparatus, when the image reading sensor is controlled to repeatedly move and stop each time an image is read from the document by the image reading sensor, the image reading sensor corresponds to one line of the image reading sensor. It may take longer than expected to move. Further, the image reading sensor sometimes goes too far from the target stop position. If the movement for one line took longer than expected, the next line could not be read even though the reading of the image for one line was finished, and the process was delayed. A problem occurred.

  The present invention has been made in view of such circumstances, and an object thereof is to appropriately set the moving speed of the image reading sensor to improve the processing speed.

The main invention for achieving the object is as follows:
(A) an image reading sensor for reading an image from a document;
(B) a motor that moves the image reading sensor relative to the document when an image is read from the document by the image reading sensor;
(C) When the image reading sensor reads an image from a document, the image reading sensor controls the motor so that the image reading sensor repeats moving and stopping each time an image is read from the document by the image reading sensor. A motor control unit that changes a setting of a current value of a current for controlling the motor based on a time required for the image reading sensor to move for one line;
An image reading apparatus comprising (D).

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  At least the following matters will become apparent from the description of the present specification and the accompanying drawings.

(A) an image reading sensor for reading an image from a document;
(B) a motor that moves the image reading sensor relative to the document when an image is read from the document by the image reading sensor;
(C) When the image reading sensor reads an image from a document, the image reading sensor controls the motor so that the image reading sensor repeats moving and stopping each time an image is read from the document by the image reading sensor. A motor control unit that changes a setting of a current value of a current for controlling the motor based on a time required for the image reading sensor to move for one line;
An image reading apparatus comprising (D).

  In such an image reading apparatus, since the setting of the current value of the current for controlling the motor is changed based on the time required for the image reading sensor to move for one line, the motor can be appropriately controlled. it can. Thereby, the moving speed of the image reading sensor can be set appropriately, and the processing speed can be improved.

  In such an image reading device, the motor control unit changes the setting of the current value of the current for controlling the motor based on the distance that the image reading sensor has gone beyond the target stop position. Also good. As described above, when the image reading sensor has exceeded the target stop position, the motor can be appropriately controlled by changing the setting of the current value of the current for controlling the motor based on the excessive distance. As a result, the processing speed can be improved while preventing the image quality from deteriorating.

  In the image reading apparatus, the motor control unit reads the image each time an image is read from the original by the image reading sensor when the image is read from the original by the image reading sensor. In order to control the motor so that the sensor repeats moving and stopping, the current value is increased with time, and the current value is decreased by a predetermined value every time the motor rotates by a predetermined amount. good. In this way, the motor control unit increases the current value with time, and decreases the current value by a predetermined value every time the motor rotates by a predetermined amount, thereby smoothing the image reading sensor at a very slow speed. Can be moved to.

  In the image reading apparatus, the motor control unit may change the setting of the initial value of the current value at the start of movement of the image reading sensor as the setting of the current value. As described above, the motor control unit can appropriately control the motor by changing the setting of the initial value of the current value at the start of movement of the image reading sensor as the setting of the current value. Thereby, the processing speed can be improved.

  In such an image reading apparatus, the motor control unit may change the setting of the increase rate of the current value with time as the setting of the current value. As described above, the motor control unit can appropriately control the motor by changing the setting of the increase rate with the lapse of time of the current value as the setting of the current value. Thereby, the processing speed can be improved.

  In such an image reading apparatus, the motor control unit may increase the current value stepwise as time elapses. Thus, the motor control unit can control the motor more appropriately by increasing the current value stepwise with time. Thereby, the processing speed can be improved.

  In such an image reading apparatus, the motor control unit may change the rate of increase of the current value over time. Thus, a motor control part can control a motor more appropriately by changing the increase rate of an electric current value with progress of time. Thereby, the processing speed can be improved.

  In the image reading apparatus, the motor control unit may set the predetermined value based on the current value before the decrease. Thus, a motor control part can control a motor more appropriately by setting a predetermined value based on a current value before reduction. Thereby, the processing speed can be improved.

  In the image reading apparatus, the motor control unit may set the predetermined value based on a moving speed of the image reading sensor. Thus, the motor control unit can control the motor more appropriately by setting the predetermined value based on the moving speed of the image reading sensor. Thereby, the processing speed can be improved.

  In the image reading apparatus, the motor control unit may change the predetermined value according to a difference between a moving speed of the image reading sensor and a target moving speed. Thus, the motor control unit can control the motor more appropriately by changing the predetermined value according to the difference between the moving speed of the image reading sensor and the target moving speed. Thereby, the processing speed can be improved.

  When the image reading sensor reads an image from the document, each time an image is read from the document by the image reading sensor, the motor is controlled so that the image reading sensor repeatedly moves and stops, and the image reading is performed. An image reading method comprising: changing a setting of a current value for controlling the motor based on a time required for the sensor to move for one line.

=== Overview of Image Reading Apparatus ===
Embodiments of an image reading apparatus according to the present invention will be described below. 1 to 3 illustrate an embodiment of an image reading apparatus. FIG. 1 illustrates an embodiment of an image reading apparatus. FIG. 2 is a diagram illustrating an example of the internal configuration of the image reading apparatus. FIG. 3 is a diagram illustrating an example of a block configuration of the image reading apparatus.

  As shown in FIG. 1, the image reading device 10 is connected to a computer device 20 so as to be communicable by wire or wireless. Here, as shown in FIG. 1, the image reading apparatus 10 is an apparatus generally called an image scanner, and includes a document table 12 and a document table cover 14 that opens and closes the upper surface of the document table 12. A document 15 from which an image is read is set on the document table 12. The document table cover 14 is provided at the rear end portion of the document table 12 through a hinge portion 18 so as to be freely opened and closed.

  On the other hand, as shown in FIG. 1, for example, the computer device 20 includes a computer main body 22, a display device 24, and an input device 26. The computer main body 22 includes various computers such as a personal computer. Here, the computer main body 22 includes a reading device 32 such as an FD drive device 28 or a CD-ROM drive device 30 therein. In addition, the computer main body 22 may include, for example, an MO (Magnet Optical) disk drive device or a DVD drive device. The display device 24 includes various display devices such as a CRT display, a plasma display, and a liquid crystal display. The input device 26 includes a keyboard 34, a mouse 36, and the like.

<Image reading device>
As shown in FIG. 2, the image reading apparatus 10 includes a carriage 40 and a drive mechanism that moves the carriage 40 in parallel along the direction of arrow A in the figure while maintaining a predetermined distance from the document table 12. 42 and a guide 44 for supporting the carriage 40 and guiding its movement.

  The carriage 40 has an exposure lamp 46 as a light source for irradiating light to the document 15 via the document table 12, a lens 48 on which reflected light reflected by the document 15 is incident, and the inside of the carriage 40 through the lens 48. And an image sensor 50 for receiving the reflected light taken in. The image sensor 50 includes a linear CCD sensor or the like in which photoelectric conversion elements such as photodiodes that convert optical signals into electric signals are arranged in a line. The image sensor 50 corresponds to an “image reading sensor”. The image data read by the image sensor 50 is output to the control unit 52.

  The drive mechanism 42 includes a timing belt 54 connected to the carriage 40, a pair of pulleys 55, 56 around which the timing belt 54 is stretched, and a drive motor 58 that rotationally drives one pulley 55. Yes. The drive motor 58 includes various motors including a DC motor, and is driven and controlled by a control signal from the control unit 52.

  Further, the drive mechanism 42 is provided with an encoder 90 in the vicinity of the drive motor 58. The encoder 90 is a rotary encoder, and detects the position, moving distance, moving speed, and the like of the carriage 40 by detecting the rotation amount of the drive motor 58. The encoder 90 includes an encoder code plate 92 provided integrally with the rotation shaft of the drive motor 58, and a detection unit 94 provided adjacent to the encoder code plate 92. A large number of small slits (not shown) are formed at predetermined intervals on the outer peripheral edge of the encoder code plate 92. The detection unit 94 detects a slit (not shown) provided at the outer peripheral edge of the encoder code plate 92 and outputs a pulse signal corresponding to the rotation amount of the drive motor 58.

<Control unit>
As shown in FIG. 3, the control unit 52 includes a controller 60, a motor control unit 62, a lamp control unit 64, a sensor control unit 66, an AFE (Analog Front End) unit 68, a digital processing circuit 70, And an interface circuit 72. Further, the AFE (Analog Front End) unit 68 includes an analog signal processing circuit 74 and an A / D conversion circuit 76.

  The controller 60 controls the motor control unit 62, the lamp control unit 64, the sensor control unit 66, the AFE (Analog Front End) unit 68, the digital processing circuit 70, and the interface circuit 72 based on commands from the computer main body 22. The motor control unit 62 performs drive control of the drive motor 58 for moving the carriage 40 according to a command from the controller 60. The lamp control unit 64 controls the light emission of the exposure lamp 46. The sensor control unit 66 controls the image sensor 50.

  An analog signal processing circuit 74 of an AFE (Analog Front End) unit 68 performs signal processing on an analog signal of an image read by the image sensor 50. An A / D conversion circuit 76 of an AFE (Analog Front End) unit 68 performs A / D conversion on the image signal processed by the analog signal processing circuit 74 into a digital signal.

  The digital processing circuit 70 performs digital signal processing on the digital signal sent from the A / D conversion circuit 76 of the AFE (Analog Front End) unit 68. Here, specifically, various image processing and the like are performed, including correction processing such as shading correction. The digital signal subjected to the digital signal processing is output as image data (image data) read from the document 15 to the outside, that is, to the computer main body 22 to which the image reading apparatus 10 is connected in this case. The In addition to this, the interface circuit 72 receives commands (commands) and the like from the computer main body 22 to the image reading apparatus 10.

=== Exposure lamp ===
The exposure lamp 46 includes LED lamps of three colors of red (R), green (G), and blue (B). These RGB three-color LED lamps are turned on at different timings when the image sensor 50 reads an image from the document 5. That is, for example, the three color LED lamps are lit in the order of red (R) → green (G) → blue (B).

  FIG. 4 explains an example of the light emission order of the three-color LED lamps. As shown in the figure, the exposure lamps 46 are individually lit at different timings within the period of one cycle. The LED lamps of the respective colors are turned on for predetermined times Tr, Tg, and Tb set in advance within a period of one cycle. In order to turn on these three color LED lamps for predetermined times Tr, Tg, and Tb, respectively, a total exposure time Tw is required per cycle.

=== Image sensor ===
FIG. 5 illustrates an example of a photoelectric conversion element provided in the image sensor 50. As shown in the figure, the image sensor 50 according to the present embodiment includes a plurality of photodiodes 80 arranged in a line along a predetermined direction, and a charge transfer unit 82 (CCD: charge). -coupled device) and a plurality of gates 84 provided between the plurality of photodiodes 80 and the charge transfer unit 82, respectively.

  Electric charges are generated in the plurality of photodiodes 80 according to the amount of received light. In the present embodiment, each of the plurality of photodiodes 80 receives light emitted from the exposure lamp 46 and reflected from the document 15 placed on the document table 12. That is, each photodiode 80 receives light of three colors emitted from the exposure lamp 46, that is, light of each color of red (R), green (G), and blue (B). The plurality of photodiodes 80 generate charges P corresponding to the amounts of light of the three colors received.

  The charge P generated in each photodiode 80 is transferred to the charge transfer unit 82. When the charge P generated in each photodiode 80 is transferred to the charge transfer unit 82, each gate 84 (see the gray portion in the figure) is opened. The charge P generated in each photodiode 80 quickly moves to the charge transfer unit 82 due to the potential well relationship.

  The charge transfer unit 82 temporarily accumulates the charge P that has moved from each photodiode 80 and then sequentially transfers the charge P toward the detection circuit 86. The detection circuit 86 sequentially detects the amount of charge transferred by the charge transfer unit 82. Here, the charge amount of the charge P detected by the detection circuit 86 becomes data for one pixel constituting the image of the document 15 on the document table 12 read by the image sensor 50. The detection circuit 86 outputs the detection result of the charge amount of the transferred charge P to an AFE (Analog Front End) unit 68 (see FIG. 3).

=== Conventional Problems and Solutions ===
<Conventional problems>
In such an image reading apparatus, every time an image is read from the document by the image sensor 50, the carriage 40 is expected to move by one line when the carriage 40 is controlled to repeat movement and stop. Sometimes it took more time. Further, the carriage 40 sometimes goes past the target stop position. If the movement for one line took longer than expected, the next line could not be read even though the reading of the image for one line was finished, and the process was delayed. A problem occurred.

<Solution>
Therefore, in the present embodiment, the time required for the carriage 40 to move by one line is measured, and the moving speed of the carriage 40 when moving the next line is appropriately set. Thereby, the processing speed is improved.

=== Control of drive motor ===
First, a method for controlling the drive motor 58 will be described here. FIG. 6 illustrates an example of a method for controlling the drive motor 58. The motor control unit 62 sets a current value for controlling the drive motor 58 in order to control the drive motor 58. Here, as shown in the figure, the motor control unit 62 increases the current value of the current for controlling the drive motor 58 in order to move the carriage 40. As a result, the drive motor 58 rotates and the carriage 40 starts to move. When the carriage 40 moves by one line (for example, one line = 1/1200 inch when the image reading resolution is 1200 dpi), the motor control unit 62 decreases the current value of the current that controls the drive motor 58. .

  Here, the current value of the current for controlling the drive motor 58 is set to zero. As a result, the drive motor 58 stops driving, and the carriage 40 finishes moving. The motor control unit 62 repeats the operation of increasing or decreasing the current value for controlling the drive motor 58. As a result, the carriage 40 repeats moving and stopping.

  In the present embodiment, the motor control unit 62 further performs the following control in order to move the carriage 40 slowly at a very slow speed equal to or lower than a predetermined speed. The predetermined speed here is a limit speed at which the drive motor 58 cannot be controlled in a sufficiently stable state by another control method such as PID control. That is, the motor control unit 62 employs a control method different from other control methods in order to move the carriage 40 slowly at a very slow speed that is equal to or lower than a predetermined speed.

  FIG. 7 illustrates an example of a method for controlling the drive motor 58 for slowly moving the carriage 40 at a very slow speed equal to or lower than a predetermined speed.

  Here, as shown in the figure, the motor control unit 62 gradually increases the current value of the current for controlling the drive motor 58 with time. In the present embodiment, the motor control unit 62 increases the current value of the current for controlling the drive motor 58 sequentially from the initial current value D0 in steps of a predetermined width ΔDt at a predetermined time interval ΔTs. When the current value for controlling the drive motor 58 gradually increases and becomes sufficiently large, the drive motor starts to rotate. Thereby, the carriage 40 starts to move.

  When the carriage 40 starts to move, the amount of movement of the carriage 40 is detected by the encoder 90. Here, when the carriage 40 moves a predetermined distance, that is, here, when the drive motor 58 rotates by a predetermined amount, the motor control unit 62 decreases the current value of the current for controlling the drive motor 58 by the predetermined value Dm. Let In the present embodiment, the motor control unit 62 decreases the current value of the current that controls the drive motor 58 by a predetermined value Dm each time an edge is input from the pulse signal output from the encoder 90.

  In the present embodiment, the predetermined value Dm is set to a value obtained by multiplying the current value Dx before the decrease by a predetermined setting rate Ks. That is, here, for example, the predetermined value Dm is obtained by an arithmetic expression “Dm = Dx × Ks”. Accordingly, the predetermined value Dm may be set to a different value each time the drive motor 58 rotates by a predetermined amount.

  Thus, after reducing the current value of the current for controlling the drive motor 58 by the predetermined value Dm, the drive motor 58 is stopped again. Thereafter, the motor control unit 62 again gradually increases the current value of the current for controlling the drive motor 58 with the passage of time. As a result, the drive motor 58 starts to rotate and the carriage 40 starts to move again.

  When the rotation amount of the drive motor 58 reaches a predetermined amount again, that is, here, when an edge is input from the pulse signal output from the encoder 90, the current value of the current that controls the drive motor 58 is again set. Decrease by a predetermined value Dm. As a result, the drive motor 58 stops again. Again, the motor control unit 62 gradually increases the current value of the current for controlling the drive motor 58 with the passage of time.

  In this way, the motor control unit 62 gradually increases the current value of the current that controls the drive motor 58 with time, and the current that controls the drive motor 58 every time the drive motor 58 rotates a predetermined amount. The operation of decreasing the current value by the predetermined value Dm is repeatedly executed until the carriage 40 moves by one line. As a result, the carriage 40 moves at a very slow speed equal to or less than a predetermined speed while repeatedly moving and stopping at very fine time intervals.

=== Acquisition of elapsed time ===
In the present embodiment, the time required for the carriage 40 to move by one line is measured, and the setting of the current value for controlling the drive motor 58 is changed based on the measured time.

  The motor control unit 62 includes a timer (not shown) that measures the time required for the carriage 40 to move by one line. When the motor control unit 62 increases the current value of the current that controls the drive motor 58, the motor control unit 62 starts time measurement using a timer. Then, the motor control unit 62 ends the time measurement by the timer when the carriage 40 has finished moving for one line. Thereby, the motor control unit 62 measures the time required for the carriage 40 to move by one line.

  And the motor control part 62 changes the setting of the electric current value of the electric current which controls the drive motor 58 based on the time measured here. Specifically, when the measured time is longer than a predetermined time, the motor control unit 62 changes the setting so that the current value of the current for controlling the drive motor 58 becomes larger. That is, when the carriage 40 is moved by one line, the setting is changed so that the current value for controlling the drive motor 58 becomes a larger value.

  Here, as the predetermined time serving as a criterion for determining whether or not to change the setting of the current value for controlling the drive motor 58, a time that must be secured at least when the carriage 40 moves by one line is set. It is preferable to set the reference. That is, in the present embodiment, when the carriage 40 moves by one line, for example, the lighting time of the LED lamp of the exposure lamp 46, that is, the lighting times Tr, Tg, Tb of the LED lamps of each RGB color here, for example. At least the exposure time Tw must be secured. For this reason, it is necessary to set the predetermined time to a time exceeding the total exposure time Tw. In addition to this, the time for performing the process of moving the charge P generated in each photodiode 80 of the image sensor 50 to the charge transfer unit 82 may be considered.

  When the measured time is shorter than the predetermined time, the setting may be changed so that the current value of the current for controlling the drive motor 58 becomes a small value.

=== Specific setting change method ===
The motor control unit 62 changes the setting so that the current value of the current for controlling the drive motor 58 becomes a larger value when the measured time is longer than the predetermined time. Here, a setting change method executed by the motor control unit 62 will be described with a specific example.

(A) Change of initial current value D0 Here, the set value of the initial current value D0 is changed. If the setting is changed so that the initial current value D0 is increased, the current value can be increased at an earlier stage when the motor control unit 62 gradually increases the current value of the current for controlling the drive motor 58. it can. Thereby, the timing at which the drive motor 58 begins to rotate can be advanced. Thus, the time from when the motor control unit 62 sets the current value of the current for controlling the drive motor 58 to the initial current value D0 until the drive motor 58 starts to rotate can be shortened. Improvements can be made.

(B) Change of increase rate of current value Here, the setting of at least one of the predetermined time interval ΔTs and the predetermined width ΔDt is changed. When the setting is changed so that the predetermined time interval ΔTs is shortened, the increase rate of the current value of the current for controlling the drive motor 58 can be increased. That is, the current value can be increased in a short time. Thus, the time until the drive motor 58 starts to rotate can be shortened, and the processing efficiency can be improved.

  Further, when the setting is changed so that the predetermined width ΔDt becomes a larger value, the increase rate of the current value of the current for controlling the drive motor 58 can be increased. That is, the current value can be increased in a short time. Thus, the time until the drive motor 58 starts to rotate can be shortened, and the processing efficiency can be improved.

(C) Change of Predetermined Value Dm that Decreases Current Value Here, the setting of the predetermined value Dm that decreases the current value is changed. If the predetermined value Dm is set to be small, after the current value of the current for controlling the drive motor 58 is decreased by the motor control unit 62, the motor control unit 62 starts again when the current value is gradually increased again. The current value can be increased. As a result, the current value can be increased in a short time when the next current value is increased. Thus, the time until the drive motor 58 starts to rotate can be shortened, and the processing efficiency can be improved.

(D) Supplementary Note When the time measured by the motor control unit 62 is longer than the predetermined time, the initial current value D0, the predetermined time interval ΔTs, the predetermined width ΔDt, or the The setting of the predetermined value Dm may be changed. That is, as the time measured by the motor control unit 62 is longer than the predetermined time, the initial current value D0, the predetermined time interval ΔTs, the predetermined width ΔDt, or the predetermined value Dm may be greatly changed. good.

  FIG. 8A illustrates an example in which the setting of the initial current value D0 is changed according to the time when the time T measured by the motor control unit 62 exceeds a predetermined time. Here, the predetermined time is set to “9 (ms)”. When the time measured by the motor control unit 62 exceeds “9 (ms)”, the setting of the initial current value D0 is changed according to the exceeded time.

=== If the carriage goes too far ===
In this way, when the time measured by the motor control unit 62 is longer than the predetermined time, when the setting is changed so that the current value of the current for controlling the drive motor 58 becomes a larger value, the drive motor 58 As a result, the current value for controlling the current becomes too large, and even if the carriage 40 reaches the target stop position, it may not be able to stop smoothly at the target stop position.

  Therefore, when the carriage 40 has passed the target stop position in this way, it is preferable to change the setting so that the current value of the current for controlling the drive motor 58 becomes a smaller value. In this case, it is preferable that a large change is made to the current value of the current for controlling the drive motor 58 based on the distance that the carriage 40 has passed the target stop position.

  FIG. 8B illustrates an example in which the setting of the initial current value D0 is changed according to the distance M that the carriage 40 has passed the target stop position. Here, the current value of the current for controlling the drive motor 58 is changed only when the distance M over traveled by the carriage 40 exceeds a predetermined distance. Here, when the distance for one line is exceeded as a predetermined distance (specifically, when the image reading resolution is 1200 dpi, 1 line = 1, 1200 inches, here, “12”), The current value of the current that controls the drive motor 58 is changed. This is because when the distance that the carriage 40 has traveled is shorter than the distance of one line, there is no significant effect when the next line is read. This is because if the distance M that the carriage 40 has traveled exceeds the distance of one line, the image is skipped by one line from the document, and thus there is a possibility of adversely affecting the read image quality.

  Here, when the overtravel distance M of the carriage 40 exceeds the distance of one line, the amount of change in the setting of the initial current value D0 changes according to the distance of the excess. As described above, since the amount of change in the setting of the initial current value D0 varies depending on the distance over which the carriage 40 has exceeded the distance for one line, the drive motor 58 can be controlled more appropriately. Can be implemented.

=== Other setting methods ===
(A) Other Setting Method of Current Value Increase Rate The current value increase rate of the current for controlling the drive motor 58 may be set as follows. FIG. 9 illustrates an example of another method for setting the current value increase rate. Here, the rate of increase of the current value for controlling the drive motor 58 gradually increases with the elapsed time. That is, the predetermined width ΔDt in which the current value increases at the predetermined time interval ΔTs gradually increases with the elapsed time. Here, the predetermined width ΔDt is set to increase by “+6” every time it is added to the current value five times, with “+20” as an initial value. That is, the increase amount of the predetermined width ΔDt is set to “+6”. As a result, the predetermined width ΔDt gradually increases in the order of “+20” → “+26” → “+32” → “38” → “+44”. After the edge is input to the pulse signal output from the encoder 90 and the current value decreases, the predetermined width ΔDt gradually increases again with “+20” as an initial value.

  As described above, the predetermined width ΔDt gradually increases with the passage of time, whereby the time until the drive motor 58 starts to rotate can be further shortened. As a result, the processing efficiency can be further improved.

(B) Another setting method for decreasing the current value The predetermined value Dm for decreasing the current value may be set as follows. FIG. 10 illustrates an example of another setting method of the predetermined value Dm for decreasing the current value. Here, the setting of the predetermined value Dm is changed based on the current rotation speed of the drive motor 58 (current movement speed of the carriage 40). Specifically, the setting of the predetermined value Dm is changed based on the difference between the current rotation speed of the drive motor 58 and the target rotation speed.

  First, a method for obtaining the current rotation speed of the drive motor 58 (current movement speed of the carriage 40) will be described. The current rotation speed of the drive motor 58 (current movement speed of the carriage 40) can be obtained based on the pulse signal output from the encoder 90. Here, a method of acquiring the current rotation speed of the drive motor 58 (current movement speed of the carriage 40) based on the two types of pulse signals ENC-A and ENC-B output from the encoder 90 will be described.

  The current rotation speed of the drive motor 58 (current movement speed of the carriage 40) can be acquired based on the phase difference between the edges of these two types of pulse signals ENC-A and ENC-B output from the encoder 90. . That is, assuming that one cycle of these two types of pulse signals ENC-A and ENC-B is “T”, the phase difference between these two types of pulse signals ENC-A and ENC-B is ¼. The period is “1 / 4T”. When the current timing is “Nw”, the current rotation speed of the drive motor 58 (current movement speed of the carriage 40) is equal to the phase difference Td between the two previous pulse signals ENC-A and ENC-B. It can be easily obtained based on this. That is, it can be obtained by “1 period T = 4 × Td”.

  Based on the current rotation speed of the drive motor 58 thus obtained (current movement speed of the carriage 40), the setting of the predetermined value Dm for decreasing the current value is changed. In the present embodiment, the predetermined value Dm is set to a value obtained by multiplying the current value Dx before decreasing by a predetermined setting rate Ks. Therefore, here, when the setting of the predetermined value Dm is changed, the predetermined setting rate Ks is changed.

  If the predetermined set rate Ks is set to be divided into “fixed value” and “correction value” as shown in the following formula (1), that is, the “correction value” is changed. become. Then, it is assumed that the “correction value” is set as shown in the following equation (2).

Predetermined set rate Ks = fixed value + correction value (1)
Correction value = Coefficient x (Current rotation speed-Target rotation speed) (2)
Assuming that the coefficient is a positive number, when the relationship of current rotational speed <target rotational speed is satisfied, the correction value <0, and the predetermined setting rate Ks is changed in a decreasing direction. Therefore, the current value of the current for controlling the drive motor 58 is corrected in the increasing direction. On the other hand, when the relationship of current rotational speed> target rotational speed is satisfied, the correction value> 0, and the predetermined set rate Ks is changed in the increasing direction. Therefore, the current value of the current that controls the drive motor 58 is corrected in a decreasing direction.

  The predetermined value Dm for decreasing the current value in this way is changed based on the current rotation speed of the drive motor 58 (current movement speed of the carriage 40) until the drive motor 58 starts rotating. Time can be shortened and processing efficiency can be improved.

=== Actual procedure ===
FIG. 11 illustrates an example of a control procedure of the drive motor 58 that is actually performed by the motor control unit 62.

  Here, the motor control unit 62 first checks whether or not the line to be read is the first line (S102). If the line to be read is the first line, step S104 is skipped and the process proceeds to step S106. On the other hand, if the line to be read is not the first line, in step S104, the distance M that the carriage 40 has traveled too far from the target stop position is acquired when reading the previous one line image (S104). Thereafter, the process proceeds to step S106.

  In step S106, the motor control unit 62 starts time measurement (S106). This time measurement is for measuring the time required for the carriage 40 to move by one line. After starting the time measurement, an initial current value D0 is set as a current value for controlling the drive motor 58, and the current value is sequentially increased from the initial current value D0 by a predetermined width ΔDt at a predetermined time interval ΔTs. (S108).

  Next, the motor control unit 62 checks whether or not the drive motor 58 has rotated a predetermined amount (S110). Here, if the drive motor 58 has been rotated by a predetermined amount, the motor control unit 62 proceeds to step S114.

  On the other hand, if the drive motor 58 has not rotated by a predetermined amount in step S110, the motor control unit 62 proceeds to step S112 and proceeds to a predetermined width ΔDt at a predetermined time interval ΔTs with respect to the current value. It is checked whether or not the number of times added has reached a predetermined number (here, “5 times”, for example). Here, if the number of times the predetermined width ΔDt is added to the current value has not reached the predetermined number, the motor control unit 62 then returns to step S110 and determines whether the drive motor 58 has rotated a predetermined amount again. Is checked (S110).

  On the other hand, if the number of times that the predetermined width ΔDt is added to the current value has reached the predetermined number, the motor control unit 62 then proceeds to step S118 and adds to the current value at a predetermined time interval ΔTs. Setting is made to add a predetermined increase amount (here, “+6”) to the width ΔDt. As a result, the predetermined width ΔDt added to the current value increases from the next time. After performing the setting for adding the predetermined increase amount (here, “+6”) to the predetermined width ΔDt in this way, the motor control unit 62 then returns to step S110, and the drive motor 58 is again set to the predetermined amount. It is checked whether or not it has been rotated (S110).

  When it is determined in step S110 that the drive motor 58 has rotated by a predetermined amount and the process proceeds to step S114, the motor control unit 62 determines whether the carriage 40 has finished moving for one line. Is checked (S114). If the carriage 40 has not finished moving for one line, the motor control unit 62 proceeds to step S116 and sets the current value for controlling the drive motor 58 by a predetermined value Dm. Decrease (S116). After reducing the current value by the predetermined value Dm in this way, the motor control unit 62 proceeds to step S112, and the number of times the predetermined width ΔDt is added to the current value at the predetermined time interval ΔTs is obtained. It is checked whether or not a predetermined number of times (for example, “5 times”) has been reached.

  On the other hand, if the carriage 40 has finished moving for one line, the motor control unit 62 proceeds to step S120 and stops the drive motor 58. Thereafter, the motor control unit 62 proceeds to step S122, and ends the time measurement started in step S106 (S122). Thereby, the motor control unit 62 can acquire the time required for the carriage 40 to move by one line.

  Thereafter, the motor control unit 62 proceeds to step S124, and checks whether or not the accumulation of electric charge in each photodiode 80 of the image sensor 50 is completed (S124). That is, here, for example, it is checked whether or not the total exposure time Tw for turning on the LED lamps of the RGB colors of the exposure lamp 46 has elapsed. When the accumulation of electric charges in each photodiode 80 of the image sensor 50 is completed, the motor control unit 62 proceeds to step S126 and checks whether image reading is completed (S126). ). Here, when the reading of the image is completed, the motor control unit 62 ends the processing promptly. On the other hand, if the image reading has not been completed, the motor control unit 62 returns to step S102 and restarts the process to read the next line again.

=== Summary ===
As described above, in this embodiment, each time an image is read from the document by the image sensor 50, when the carriage 40 is controlled to repeat the movement and the stop, the time required for the carriage 40 to move by one line is measured. Based on the measured time, the setting of the current value of the current for controlling the drive motor 58 is changed. From this, when the time required for the carriage 40 to move by one line is long, the setting can be changed so that the current value of the current for controlling the drive motor 58 becomes larger. As a result, the time required for the carriage 40 to move by one line can be shortened, and the processing speed can be improved.

  Furthermore, as a result of changing the setting so that the current value for controlling the drive motor 58 becomes a larger value, the current value for controlling the drive motor 58 becomes too large, and the stop position of the carriage 40 becomes the target stop position. Even if it has passed, since the setting is changed so that the current value of the current for controlling the drive motor 58 is reduced based on the distance that has passed, it is possible to prevent image quality deterioration from occurring. be able to.

=== Other Embodiments ===
As described above, the embodiment has been described. However, the above-described embodiment is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed or improved without departing from the gist thereof, and needless to say, the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About image reading sensor>
In the above-described embodiment, the image sensor 50 provided in the carriage 40 has been described as an example of the “image reading sensor”. However, in the “image reading sensor” here, such a carriage 40 is not necessarily used. It is not restricted to the sensor provided in. That is, any type of sensor may be used as long as the sensor moves relative to the document 15 and reads an image from the document. That is, a sensor that reads an image from a document by moving the document relative to the “image reading sensor” may be included.

  In the “image reading sensor” here, the image sensor 50 including a plurality of photodiodes 80 is described as an example of the photoelectric conversion element. However, in the “image reading sensor” herein, Is not necessarily limited to a sensor having a plurality of such photodiodes 80. That is, any type of sensor may be used as long as it reads an image from a document. That is, any method for reading an image from the document 15 may be used.

<About motor>
In the above-described embodiment, the drive motor 58 that moves the carriage 40 on which the image sensor 50 (image reading sensor) is mounted has been described as an example of the “motor”. However, the “motor” described here is not necessarily the same. It is not limited to such a motor. That is, any type of motor may be used as long as the image reading sensor (image sensor 50) moves the image reading sensor (image sensor 50) relative to the original when the image is read from the original by the image reading sensor (image sensor 50). In other words, the “motor” mentioned here may include a motor for moving the document relative to the “image reading sensor”.

<About image reader>
In the above-described embodiment, the “image reading device” has been described by taking an example of an image reading device provided on a carriage in which an image reading sensor moves relative to a document set on a document table. The “image reading device” here is not necessarily limited to this type of “image reading device”. That is, any type of image reading apparatus may be used as long as the image reading apparatus includes an image reading sensor that moves relative to the document 15 and reads an image from the document. That is, the “image reading apparatus” here includes an image reading apparatus in which an original is moved relative to an “image reading sensor” and an image is read from the original.

1 is an explanatory diagram of an embodiment of an image reading system. FIG. FIG. 3 is an explanatory diagram illustrating an example of an internal configuration of an image reading apparatus. 1 is an explanatory diagram illustrating an example of a system configuration of an image reading apparatus. FIG. Explanatory drawing of an example of the light-emission method of an exposure lamp. Explanatory drawing of the transfer method of the electric charge which generate | occur | produced in the photoelectric conversion element. Explanatory drawing of an example of the control method of a drive motor. Explanatory drawing of the method of moving a carriage below predetermined speed. Explanatory drawing of an example of the change method of the setting of the electric current value of the electric current which controls a drive motor. Explanatory drawing of an example of the change method of a setting when a carriage passes the target stop position too much. Explanatory drawing of an example of the other setting method of the increase rate of an electric current value. Explanatory drawing of an example of the other setting method of the predetermined value which decreases an electric current value. The flowchart explaining the process sequence of an example of an actual process.

Explanation of symbols

10 image reading device, 12 document table, 14 document table cover, 15 document,
18 hinge part, 20 computer apparatus, 22 computer main body,
24 display device, 26 input device, 28 FD drive device,
30 CD-ROM drive, 32 reader, 34 keyboard,
36 mouse, 40 carriage, 42 drive mechanism, 44 guide,
46 exposure lamp, 48 lens, 50 image sensor,
52 control unit, 54 timing belt,
55 pulley, 56 pulley, 58 drive motor, 60 controller,
62 motor control unit, 64 lamp control unit, 66 sensor control unit,
68 AFE (Analog Front End) part, 70 Digital processing circuit,
72 interface circuit, 74 analog signal processing circuit,
76 A / D conversion circuit, 80 photodiode, 82 charge transfer unit,
84 gate, 90 encoder, 92 encoder code plate, 94 detector

Claims (12)

(A) an image reading sensor for reading an image from a document;
(B) a motor that moves the image reading sensor relative to the document when an image is read from the document by the image reading sensor;
(C) When the image reading sensor reads an image from a document, the image reading sensor controls the motor so that the image reading sensor repeats moving and stopping each time an image is read from the document by the image reading sensor. A motor control unit that changes a setting of a current value of a current for controlling the motor based on a time required for the image reading sensor to move for one line;
An image reading apparatus comprising (D).   The said motor control part changes the setting of the electric current value of the electric current which controls the said motor, when the said image reading sensor goes over the target stop position too much based on the distance which went too much. Image reading device.   When the image reading sensor reads an image from a document, the motor control unit causes the motor reading unit to repeatedly move and stop each time an image is read from the document by the image reading sensor. 3. The method according to claim 1, wherein the current value is increased with time to control the current value, and the current value is decreased by a predetermined value every time the motor rotates a predetermined amount. Image reading device.   The image reading apparatus according to claim 3, wherein the motor control unit changes the setting of the initial value of the current value at the start of movement of the image reading sensor as the setting of the current value.   5. The image reading apparatus according to claim 3, wherein the motor control unit changes the setting of an increase rate with the passage of time of the current value as the setting of the current value. 6.   The said motor control part changes the setting of the said predetermined value which decreases the said current value, whenever the said motor rotates predetermined amount as a setting of the said current value. The image reading apparatus according to item.   The image reading apparatus according to claim 3, wherein the motor control unit increases the current value stepwise as time elapses.   The image reading apparatus according to claim 3, wherein the motor control unit changes the rate of increase of the current value over time.   The image reading apparatus according to claim 3, wherein the motor control unit sets the predetermined value based on the current value before the decrease.   The image reading apparatus according to claim 3, wherein the motor control unit sets the predetermined value based on a moving speed of the image reading sensor.   The image reading apparatus according to claim 3, wherein the motor control unit changes the predetermined value in accordance with a difference between a moving speed of the image reading sensor and a target moving speed. .   When the image reading sensor reads an image from the document, each time an image is read from the document by the image reading sensor, the motor is controlled so that the image reading sensor repeatedly moves and stops, and the image reading is performed. An image reading method comprising: changing a setting of a current value for controlling the motor based on a time required for the sensor to move for one line.