JP2010183231A - Image reader and method of controlling same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for obtaining white reference data at a high speed and with high accuracy even when a white reference plate is narrow. <P>SOLUTION: A read control part 120 performs the processing of acquiring the white reference data to perform shading correction. The read control part 120 outputs a shift pulse to be the start timing of charge storage corresponding to a prescribed reference color (red, for instance) to an image sensor 220 and then monitors the lapse of the prescribed time. Then, in the case where an output result from an encoder 320 is in a prescribed state when the prescribed time elapses, the shift pulse to be the start timing of the charge storage corresponding to the prescribed reference color is output to the image sensor 320. Meanwhile, in the case that the output result from the encoder 320 is not in the prescribed state when the prescribed time elapses, the shift pulse to be the start timing of the charge storage corresponding to the prescribed reference color is output to the image sensor 320 after waiting for the output result from the encoder 320 to be in the prescribed state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus and a method for controlling the image reading apparatus.

  Some image reading devices such as a scanner device perform shading correction prior to reading a document in order to prevent unevenness of a read image due to non-uniformity of light amount of a light source lamp and sensitivity variations of image reading elements ( For example, Patent Document 1). In the shading correction, a white reference plate provided in the image reading apparatus is read, and a correction formula is created for each reading element based on read data (hereinafter referred to as “white reference data”).

  In the image reading apparatus having the shading correction function as described above, the timing for reading the white reference plate by the image sensor and the position of the sensor module equipped with the image sensor so that line omission etc. do not occur when reading the white reference plate. Therefore, it is necessary to control to accurately match the above.

  By the way, in the high-speed movement of the carriage, it passes through the acceleration area, constant speed area, and deceleration area from the start to the end of movement. In such a case, it is better to read in a constant speed region for stable reading.

JP-A-7-203201

  However, if the width of the white reference plate is reduced in order to reduce the size of the apparatus, the period of the constant speed region is shortened. Therefore, accurate white reference data cannot be obtained by reading only the period of the constant speed region.

  An object of the present invention is to provide a technique for obtaining white reference data at high speed and with high accuracy even when a white reference plate is narrow.

  The present invention for solving the above-mentioned problems is an image reading apparatus that performs shading correction using white reference data, the image sensor for transferring charges accumulated in a photoelectric conversion element to a shift register by a shift pulse, and A motor for moving a carriage that carries the image sensor; an encoder that detects and outputs a rotation amount of the motor; and a shift pulse control unit that controls an output timing of the shift pulse, the shift pulse control unit In the process of obtaining the white reference data, after a shift pulse serving as a charge accumulation start timing corresponding to a predetermined reference color is output, the elapse of a predetermined time is monitored, and when the predetermined time elapses, the encoder When the output result of is a predetermined state, the charge storage corresponding to the predetermined reference color is performed. If the output result of the encoder is not in the predetermined state when the predetermined time has elapsed, after waiting for the output result of the encoder to be in the predetermined state, the predetermined pulse is output. A shift pulse serving as a charge accumulation start timing corresponding to the reference color is output.

1 is a schematic configuration diagram of an image reading apparatus according to an embodiment of the present invention. It is a timing chart of a control signal in the reading operation of white reference data. 6 is a flowchart for explaining white reference data acquisition processing performed by the image reading apparatus.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an image reading apparatus 50 to which an embodiment of the present invention is applied.

  The image reading apparatus 50 is a so-called flat bed type image reading apparatus provided with a document table (not shown) on the upper surface of a housing. The image reading device 50 scans the image sensor 220 and reads an image of a document placed on a document platen of a transparent plate.

  As shown in the figure, the image reading device 50 controls the entire carriage 200 having the LED light source 210 and the image sensor 220, the drive mechanism 300 for controlling the movement of the carriage 200, and the image reading device 50, and reads the image. And a control unit 100 that performs various processes for the purpose.

  Further, the image reading apparatus 50 has a mechanism for generating white reference data used for performing general shading correction. In the present embodiment, the image reading apparatus 50 includes a white reference plate that is a uniform reflecting surface with a high reflectivity (not shown) as a mechanism for generating white reference data. Note that black reference data is also used for general shading correction, but the image reading device 50 does not need to include a special mechanism for generating black reference data. When generating the black reference data, for example, the image reading device 50 reads the image data with the LED light source 210 turned off, and generates black reference data.

  The carriage 200 carries the image sensor 220 together with the LED light source 210 in the sub-scanning direction. The carriage 200 is slidably locked to a guide shaft or the like parallel to the platen surface of the document table, and is pulled by a belt rotated by a motor (for example, a DC motor) 310 of the drive mechanism 300. The amount of movement of the carriage 200 is controlled by the output value of the encoder 320 that outputs encoder pulses (A phase, B phase) according to the rotation amount of the motor 310 of the drive mechanism 300.

  The LED light source 210 includes a red LED, a green LED, and a blue LED, and generates light of three colors of RGB in a predetermined order. Specifically, the LED light source 210 emits light in the order of a red LED, a green LED, and a blue LED when reading a white reference plate for one line. Then, in order to read several lines (the width of the white reference plate), the same light emitting operation is repeated. The light emission time of each color LED is determined in advance for each color, and the light emission is stopped (extinguished) when the predetermined time elapses after the light emission (lights on).

  In the following, among the three colors of RGB, the color that emits light first in the light emission operation for one line (red in the above example) is referred to as “reference color”.

  The image sensor 220 receives the light reflected by the document, accumulates electric charges corresponding to the amount of received light, and sends the charges to the control unit 100 as image reading data (electrical signals).

  The image sensor 220 includes a plurality of sensor chips arranged in the main scanning direction. Each sensor chip has the same configuration as a normal CCD (Charge Coupled Device) image sensor. That is, each sensor chip includes a photoelectric conversion element (photodiode PD), a shift gate, and a shift register. Then, the charge accumulated in the photoelectric conversion element is transferred to the shift register by opening the shift gate, and output while sequentially moving the charge by the shift register. The opening of the shift gate (charge transfer) is performed in response to application of a shift pulse (a signal from a reading control unit 120 described later). Here, since the photoelectric conversion element always accumulates charges according to the amount of received light, the transfer timing of the charges to the shift register is the start timing of accumulating charges for the light of the next emission color. Become. Then, the charge transferred to the shift register is converted into an electrical signal (analog data) by an output unit at the end of the shift register and sent to the A / D conversion unit 110.

  The control unit 100 includes an A / D conversion unit 110 that converts analog data output from the image sensor 220 into digital data, and a data processing unit that performs various corrections on the digital data output from the A / D conversion unit 110. 130, a storage unit 140 that stores digital data for the data processing unit 130 to perform various corrections, an output unit 150 for sending data from the data processing unit 130 to a host such as a personal computer, and the like in the control unit 100 And a reading control unit 120 that controls the LED light source 210 and the image sensor 220 in the carriage 200 and the driving mechanism 300.

  Note that the A / D converter 110 may be mounted on a substrate in the carriage 200.

  The reading control unit 120 controls the movement of the carriage 200 by controlling the rotation of the motor 310 of the driving mechanism 300.

  The reading control unit 120 also controls an image reading operation, white reference data reading operation, and black reference data reading operation of the image sensor 220. Specifically, a shift pulse for the operation of the image sensor 220 is supplied to the image sensor 220, and the transfer timing of the charge accumulated in the photoelectric conversion element to the shift register (the next charge accumulation start timing). ) To control. Further, the reading control unit 120 controls the transfer timing of the data read by the image sensor 220 to the A / D conversion unit 110.

  The reading control unit 120 also controls turning on / off of the LED light source 210 in accordance with the reading operation of the image sensor 220.

  Hereinafter, reading control of white reference data performed in the reading control unit 120 will be described.

  FIG. 2 is an example of a timing chart of control signals that the reading control unit 120 exchanges with each unit (the carriage 200 and the driving mechanism 300) in the white reference data reading control.

  As described above, the reading control unit 120 is configured so that the white reference plate is read by the image sensor 220 and the carriage 200 on which the image sensor 220 is mounted in order to prevent line omission or the like from occurring when reading the white reference plate. It is necessary to control to accurately match the position of. Accordingly, as illustrated (ideal shift pulse, ideal A phase), the reading control unit 120 causes the rise of the encoder pulse (for example, A phase) supplied from the encoder 320 and the shift pulse output to the image sensor 220. It is ideal to output a shift pulse for starting charge accumulation for the reference color (T0 indicated by a dotted line) so that the rising edge of the reference color is synchronized (the ideal B phase is also shown for reference). .

  In order to output the shift pulse at this ideal timing, the reading control unit 120 outputs (T0) a shift pulse for starting charge accumulation for the reference color, and then a predetermined time (cycle T shown in the figure) has elapsed. To monitor. Then, the reading control unit 120 determines the state of the encoder pulse (A phase) (the voltage value is “H” or “L”) at a timing when a predetermined time elapses. At this time, if the encoder pulse (A phase) is in a predetermined state (for example, “H” state), a shift pulse serving as a charge accumulation start timing corresponding to the reference color is output to the image sensor 220.

  In addition, the reading control unit 120 sets a fixed timing (regardless of the state of the encoder pulse) with respect to a shift pulse that is a charge accumulation start timing corresponding to a color other than the reference color (green and blue in the illustrated example). Output at T1, T2). For example, for a shift pulse that is a charge accumulation start timing corresponding to green (G), a shift pulse for starting charge accumulation for the reference color (R) is output (T0), and then “T1-T0” time Output at the timing when elapses. In addition, the shift pulse, which is the charge accumulation start timing corresponding to blue (B), is output at the timing when “T2-T0” time has elapsed after the charge accumulation for the reference color is started (T0) (T3). )

  Then, the reading control unit 120 switches on / off the LED light source 210 in accordance with the output timing of the shift pulse. In the example shown in the figure, the reading control unit 120 turns on the red LED in accordance with the output timing of the shift pulse, which is the charge accumulation start timing corresponding to red (R), and turns off the light after continuing the lighting for a predetermined time. . Similarly, the other color LEDs (green LED, blue LED) are turned on in accordance with the output timing of the shift pulse, which is the charge accumulation start timing corresponding to the other color (green, blue), and the lighting is continued for a predetermined time. Then turn off.

  The lighting duration time of each color LED varies depending on the color. This is because the luminance of the three light sources and the sensitivity of the sensor have differences and variations depending on the colors, and if the lighting duration time is the same, the photoelectrically converted output charge amounts of the respective colors are not equal. Therefore, the lighting duration time is set in advance according to the luminance of the three light sources and the sensitivity of the sensor.

  By the way, the image reading apparatus 50 of the present invention reads white reference data in the entire acceleration region, constant speed region, and deceleration region of the motor 310 in order to read the white reference plate at high speed. In view of general motor characteristics, the rotation speed of the motor 310 may not be as intended, particularly in the reading operation in the acceleration region and the deceleration region. Therefore, the encoder pulse supplied from the encoder 320 may be in an unexpected state (for example, “L” state) at the timing (dotted line T3) at which the shift pulse corresponding to the reference color is to be output. . As a result, conventionally, as shown in the figure (conventional shift pulse), the shift pulse corresponding to the reference color cannot be output at the timing to be output (dotted line T3). Even if the encoder pulse (conventional A phase) rises behind the timing (dotted line T3) at which the shift pulse corresponding to the reference color is to be output (T7), the shift pulse corresponding to the reference color should be output next. Until this timing (T6), the shift pulse could not be output. Then, charge accumulation corresponding to blue (B) is continued in a state where all the LEDs are turned off, and only white reference data with low accuracy can be obtained.

  On the other hand, in the image reading apparatus 50 of the present invention, the reading control unit 120 includes the timer 121 shown in FIG. 1, and the encoder pulse (A phase) is in a predetermined state at an interval shorter than the edge appearance interval of the encoder pulse. It is determined whether or not it is in the “H” state. The reading control unit 120 outputs a shift pulse for starting charge accumulation for the reference color (T0), and a predetermined time (cycle T) has elapsed, and the encoder pulse (A phase) is in a predetermined state. When it is determined that it is in the “H” state, a shift pulse corresponding to the reference color is output. Thereby, even when the encoder pulse is not in a predetermined state ("L" state) at the timing (shift line dotted line T3 of the present application) at which the shift pulse corresponding to the reference color should be output, Thereafter, a shift pulse can be output at the timing (T7) when the encoder pulse (phase A of the present application) rises. In FIG. 2, the interval for determining the state of the encoder pulse is indicated by an arrow, but the interval is not limited to the illustrated interval.

  Returning to FIG. 1, the data processing unit 130 performs various corrections such as shading correction on the digital data output from the A / D conversion unit 110 and outputs the digital data to the output unit 150. For example, when performing shading correction, the data processing unit 130 stores the image data, white reference data, and black reference data output from the A / D conversion unit 110 in the storage unit 140 described later, and corresponding pixels. Each time, shading correction is performed according to a predetermined correction formula. After the correction, the data processing unit 130 outputs the corrected image data to the output unit 150.

  The storage unit 140 stores data for the data processing unit 130 to perform various correction processes. Specifically, the storage unit 140 includes a white reference data DB (database) 141 that stores white reference data. The storage unit 140 may include an image data DB (not shown) that stores image data before correction, a black reference data DB that stores black reference data, and the like.

  The output unit 150 includes an interface for performing network connection or USB connection, and transmits the digital data output from the data processing unit 130 to the host computer.

  The image reading apparatus 50 to which this embodiment is applied has the above-described configuration. However, the configuration of the image reading apparatus 50 is not limited to this. For example, the image reading device 50 may be a multi-function machine having a print function and a facsimile function.

  The main components of the control unit 100 include input / output to / from a host, etc., a CPU that is a main control device, a ROM that stores programs, a RAM that temporarily stores data as a main memory, and the like. This can be achieved by a general computer including an interface to be controlled and a system bus serving as a communication path between each component. In addition, you may be comprised by ASIC (Application Specific Integrated Circuit) designed so that each process may be performed exclusively. The A / D conversion unit 110 can be configured by an analog front end IC (Integrated Circuit).

  Each of the above-described constituent elements is classified according to the main processing contents in order to facilitate understanding of the configuration of the image reading apparatus 50. The present invention is not limited by the way of classification and names of the constituent elements. The configuration of the image reading device 50 can be classified into more components depending on the processing content. Moreover, it can also classify | categorize so that one component may perform more processes. Further, the processing of each component may be executed by one hardware or may be executed by a plurality of hardware.

  Next, a characteristic operation of the image reading apparatus 50 configured as described above will be described. FIG. 3 is a flowchart showing white reference data reading processing performed by the image reading apparatus 50.

  First, the reading control unit 120 starts the white reference data reading process prior to the image (original) reading process. When the white reference data reading process is started, the reading control unit 120 initializes various control signals and various timers.

  Thereafter, the reading control unit 120 first determines whether or not it is time to output a shift pulse for starting charge accumulation for the reference color (step S101). For example, the reading control unit 120 monitors the elapsed time after the timer is initialized or the shift pulse corresponding to the reference color is output (T0) last time. Then, it is determined whether the monitored elapsed time is equal to or longer than a predetermined time (cycle T). Here, when it is determined that the time is equal to or longer than the predetermined time (cycle T), the reading control unit 120 determines that it is time to output the shift pulse corresponding to the reference color. On the other hand, when it is determined that the time is less than the predetermined time (cycle T), it is determined that it is not the timing to output the shift pulse corresponding to the reference color.

  If the reading control unit 120 determines in step S101 that it is time to output the shift pulse corresponding to the reference color (step S101; Yes), the process proceeds to step S102. On the other hand, if it is determined that it is not time to output the shift pulse corresponding to the reference color (step S101; No), the process proceeds to step S104.

  When the process proceeds to step S102, the reading control unit 120 determines whether or not the encoder pulse supplied from the encoder 320 is in a predetermined state (step S102). For example, the reading control unit 120 determines that the encoder pulse is in a predetermined state when the encoder pulse is in the “H” state, and determines that the encoder pulse is not in the predetermined state when the encoder pulse is in the “L” state.

  When it is determined that the encoder pulse is in a predetermined state (step S102; Yes), the reading control unit 120 outputs a shift pulse for starting charge accumulation for the reference color to the image sensor 220 (step S103). At the same time, the reading control unit 120 controls to turn on the LED corresponding to the reference color, turn on the LED for a predetermined time, and then turn off the LED. Further, the reading control unit 120 resets a timer for monitoring the elapsed time after outputting (T0) the shift pulse corresponding to the reference color, and starts monitoring the elapsed time again. Then, the process proceeds to step S104.

  On the other hand, when the reading control unit 120 determines that the encoder pulse is not in a predetermined state (step S102; No), the reading control unit 120 determines that there is a delay before the edge (rising edge) of the encoder pulse appears, and the encoder Wait until the pulse is in the predetermined state.

  In step S102, while waiting for the encoder pulse to be in a predetermined state, the reading control unit 120 uses the timer 121 to set the encoder pulse to a predetermined interval at an interval shorter than the edge appearance interval of the encoder pulse. The determination as to whether or not it is in a state is repeated.

  When the process proceeds to step S104, the reading control unit 120 determines whether it is time to output a shift pulse for starting charge accumulation for colors other than the reference color (step S104). For example, the reading control unit 120 initializes a timer or outputs a shift pulse corresponding to the reference color last time (T0), and monitors the elapsed time for a predetermined time (T1-T0, T2). -T0) is determined. Here, when it is determined that the predetermined time (T1-T0, T2-T0) coincides, the reading control unit 120 determines that it is timing to output a shift pulse corresponding to a color other than the reference color. On the other hand, if it is determined that the predetermined time (T1-T0, T2-T0) does not coincide, it is determined that it is not the timing to output a shift pulse corresponding to a color other than the reference color.

  If the reading control unit 120 determines in step S104 that it is time to output a shift pulse corresponding to a color other than the reference color (step S104; Yes), the process proceeds to step S105. On the other hand, if it is determined that it is not time to output a shift pulse corresponding to a color other than the reference color (step S104; No), the process returns to step S101.

  When the process proceeds to step S105, the reading control unit 120 outputs to the image sensor 220 a shift pulse for starting charge accumulation for colors other than the reference color (step S105). At the same time, the reading control unit 120 controls to turn on an LED corresponding to a color other than the reference color, and to turn off the LED after continuing lighting for a predetermined time. Then, the process proceeds to step S106.

  Next, the reading control unit 120 determines whether reading (acquisition) of the white reference data has been completed (step S106). For example, the reading control unit 120 determines that reading of the white reference data is completed when reading of the white reference data for a predetermined line is completed. On the other hand, if the number of lines that have been read is less than the predetermined number of lines, it is determined that reading of the white reference data has not been completed.

  If the reading control unit 120 determines in step S106 that reading of the white reference data has been completed (step S106; Yes), the reading process of white reference data (this flow) ends. On the other hand, when it is determined that the reading of the white reference data is not completed (step S106; No), the process returns to step S101.

  When the above-described white reference data reading process is performed by the image reading apparatus 50, the encoder pulse is not in a predetermined state ("L" state) at the timing (dotted line T0) at which the shift pulse corresponding to the reference color should be output. Even then, the shift pulse can be output at the timing (T7) when the encoder pulse (phase A) rises thereafter. As a result, even when the white reference plate is narrow and reading is performed in the acceleration region or deceleration region of the motor 310, white reference data can be obtained at high speed and with high accuracy.

  In addition, this invention is not limited to said each embodiment, A various deformation | transformation and application are possible.

  For example, in the above embodiment, the image reading apparatus 50 determines whether the encoder pulse (A phase) is in a predetermined state (“H” state) at an interval shorter than the edge appearance interval of the encoder pulse. , A timer 121 is provided. As shown in FIG. 2, the timer 121 constantly notifies the reading control unit 120 of the determination timing for the state of the encoder pulse during the white reference data reading operation. However, the present invention is not limited to this. For example, the timer 121 determines only during a period in which the shift pulse corresponding to the reference color should be output (T3, T6) and has not yet output the shift pulse (step S102; No). You may make it notify a timing.

  DESCRIPTION OF SYMBOLS 50 ... Image reading apparatus, 100 ... Control part, 110 ... A / D conversion part, 120 ... Reading control part, 121 ... Timer, 130 ... Data processing part, 140 ... Storage unit 141 White reference data DB 150 Output unit 200 Carriage 210 LED light source 220 Image sensor 300 Drive mechanism 310 -Motor, 320 ... encoder.

Claims (4)

An image reading apparatus that performs shading correction using white reference data,
An image sensor that transfers the charge accumulated in the photoelectric conversion element to the shift register by a shift pulse;
A motor for moving a carriage carrying the image sensor;
An encoder for detecting and outputting the rotation amount of the motor;
Shift pulse control means for controlling the output timing of the shift pulse,
The shift pulse control means includes
In the process of acquiring the white reference data,
After outputting a shift pulse that is a charge accumulation start timing corresponding to a predetermined reference color, the elapse of a predetermined time is monitored,
When the output result of the encoder is in a predetermined state when the predetermined time has elapsed, a shift pulse that is a charge accumulation start timing corresponding to the predetermined reference color is output,
If the output result of the encoder is not in the predetermined state when the predetermined time elapses, after waiting until the output result of the encoder reaches the predetermined state, the charge accumulation start timing corresponding to the predetermined reference color Output a shift pulse
An image reading apparatus. The image reading apparatus according to claim 1,
The shift pulse control means includes
Determining whether the encoder pulse is in the predetermined state at an interval shorter than an edge appearance interval of the encoder pulse;
An image reading apparatus. The image reading apparatus according to claim 1, wherein
The shift pulse control means includes
The shift pulse output timing that is the charge accumulation start timing corresponding to a color other than the predetermined reference color is determined according to each color with reference to the charge accumulation start timing corresponding to the predetermined reference color. Decide over time,
An image reading apparatus. A control method of an image reading apparatus that performs shading correction using white reference data,
The image reading device includes:
An image sensor that transfers the charge accumulated in the photoelectric conversion element to the shift register by a shift pulse;
A motor for moving a carriage carrying the image sensor;
An encoder for detecting and outputting the rotation amount of the motor;
Shift pulse control means for controlling the output timing of the shift pulse,
The shift pulse control means comprises:
In the process of acquiring the white reference data,
Monitoring the passage of a predetermined time after outputting a shift pulse that is a charge accumulation start timing corresponding to a predetermined reference color;
If the output result of the encoder is in a predetermined state when the predetermined time has elapsed, a shift pulse serving as a charge accumulation start timing corresponding to the predetermined reference color is output,
If the output result of the encoder is not in the predetermined state at the elapse of the predetermined time, after waiting until the output result of the encoder reaches the predetermined state, the charge accumulation start timing corresponding to the predetermined reference color And outputting a shift pulse that becomes
A control method for an image reading apparatus.

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