JP2009200555A - Image reader, and image read method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve picture quality of an image reader by reducing an influence of turn-on/off switching of a light source by a simple control method without increasing the number of components. <P>SOLUTION: Disclosed is the image reader equipped with a CCD image sensor which converts electric charges accumulated in a photoelectric converting element into an electric signal and outputs it as data to an A/D converter in sequence, the output of the data from the CCD image sensor to the A/D converter being stopped in timing to turn-on/off switching of the light source. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  There is an image reading device (scanner) including a light source such as an LED (Light Emitting Diode) and an image sensor including a photoelectric conversion element. In such a scanner, noise may propagate from the light source control system to the image sensor at the switching timing of turning on / off the light source, and noise may be generated in an analog signal output from the image sensor. As a result, the quality of the scanned image is degraded. In particular, in a CIS (Contact Image Sensor) type scanner, the light source LED and the image sensor are mounted in the same module, so that they are easily affected by noise.

In this regard, Patent Document 1 discloses a technique for reducing noise by mounting a noise filter.
JP-A-9-114963

  However, the technique of Patent Document 1 is disadvantageous from the viewpoint of manufacturing cost because the number of parts increases.

  An object of the present invention is to reduce the influence of switching on / off of a light source by a simple control method without increasing the number of parts and to improve image quality.

  In order to solve the above problem, in the present invention, data transfer is stopped at the switching timing of turning on / off the light source.

  For example, the present invention is an image reading apparatus including a light source and an image sensor that converts electric charges accumulated in a photoelectric conversion element into an electrical signal and sequentially outputs the data to an A / D converter, the light source The output of data from the image sensor to the A / D converter is stopped at the switching timing of turning on / off.

  According to a second aspect of the present invention, there is provided an image reading apparatus including a light source and a CCD image sensor that converts the electric charge accumulated in the photoelectric conversion element into an electric signal and sequentially outputs the electric signal to the A / D converter. And a control device for supplying a read clock for causing the image sensor to output data. The image sensor outputs data according to a read clock supplied from the control device. The control device stops the supply of the read clock to the image sensor at the switching timing of turning on and off the light source.

  According to the present invention, it is possible to reduce the influence of switching on / off of the light source and to improve the image quality with a simple control method without increasing the number of parts.

  Hereinafter, an embodiment of the present invention will be described.

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

  The image reading apparatus 1 is a so-called flat bed type image reading apparatus having a document table on an upper surface of a housing. The image reading apparatus 1 scans a CIS (Contact Image Sensor) type image sensor 12 to read an image of a document fixed on a document table of a transparent plate.

  The image reading apparatus 1 includes a carriage 10 on which an LED light source 11 and an image sensor 12 are mounted, a drive mechanism 20 that controls reciprocation of the carriage 10, and various processes for controlling the entire image reading apparatus 1 and reading an image. And a control unit 30 for performing the above.

  The LED light source 11 sequentially generates light of three colors of RGB.

  The image sensor 12 receives the light reflected from the document, accumulates electric charges corresponding to the amount of received light, and sends the charges to the control unit 30 as an image reading signal (data).

  FIG. 2 is a diagram illustrating the configuration of the image sensor 12.

  The image sensor 12 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 (SG), and a shift register (CCD). 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 is controlled by a shift gate pulse. The shift register transfers charges in response to application of a drive pulse (“read clock” from the read control unit 34). The transferred charge is converted into an electric signal (analog data) by the output unit OUT at the end of the shift register, and sent to the A / D converter 31.

  Returning to FIG.

  The carriage 10 carries the image sensor 12 together with the LED light source 11 in the sub-scanning direction. The carriage 10 is slidably locked to a guide shaft or the like parallel to the platen surface of the document table, and is pulled and reciprocated by a belt rotated by a motor 21 of the drive mechanism 20. The movement amount of the carriage is controlled by the output value of the encoder 22 that outputs a pulse according to the rotation amount of the motor 21.

  The control unit 30 includes an A / D converter 31 that converts analog data output from the image sensor 12 into digital data, and digital data that performs various correction processes on the digital data output from the A / D converter 31. The overall control of the processing unit 32, the output unit 33 for sending data from the digital data processing unit 32 to a host such as a personal computer, and the functional units in the control unit 30, and the LED light source 11 in the carriage 10 And a reading control unit 34 for controlling the image sensor 12 and the driving mechanism 20.

  The image sensor 12 and the A / D converter 31 are connected by an FFC (flexible substrate). The A / D converter 31 may be mounted on a substrate in the carriage.

  The reading control unit 34 controls the drive mechanism 20, controls the rotation of the motor 21, and controls the movement of the carriage 10.

  The reading control unit 34 also controls turning on / off of the LED light source 11. The LED light source 11 includes R, G, and B LEDs, which are sequentially turned on and off for a predetermined time. Note that the lighting time (the duration of the light emission state) in the reading period in the main scanning direction of each LED light source (R, G, B) is not uniform. 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 times are the same, the photoelectrically converted output charge amounts of the respective colors are not equal. Accordingly, the lighting duration time is set to be different according to the luminance of the three light sources and the sensitivity of the sensor.

  The reading control unit 34 also controls the image reading operation of the image sensor 12. Specifically, the timing of transferring the data read by the image sensor 12 to the A / D converter 31 is controlled. Specifically, a clock (read clock) for operating the image sensor 12 is supplied to the image sensor 12. However, the supply of the reading clock is stopped at the timing of switching on / off of the LED light source 11. Thereby, the analog data transfer from the image sensor 12 to the A / D converter 31 is stopped at the switching timing of turning on / off the LED light source 11. In the FFC (flexible substrate) that is a transfer path from the image sensor 12 to the A / D converter 31, there is a high possibility that noise will be mixed, but by temporarily stopping data transfer during this period, noise will be mixed Can be reduced.

  Such a control unit 30 includes a CPU that is a main control device, a ROM in which programs and the like are recorded, a RAM that temporarily stores data and the like as a main memory, and an interface that controls input and output with a host and the like. This can be achieved by a computer provided with a system bus serving as a communication path between the devices. In addition, you may be comprised by ASIC (Application Specific Integrated Circuit) designed so that each process may be performed exclusively.

  Next, a read clock supply operation, which is a characteristic operation of the image reading apparatus 1 of the present embodiment, will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a flowchart of the read clock supply process. FIG. 4A is a timing chart for explaining the timing of stopping the read clock for data transfer. In the lower part (B) of FIG. 4, an example of the case where the reading clock is not stopped (conventional) is also shown for reference.

  The reading control unit 34 starts the flow of FIG. 3 at the opening timing of the shift gate.

  First, the reading control unit 34 determines whether or not the current time is the switching timing of turning on / off the LED (S11).

  As shown in FIG. 4, in the reading cycle (shift gate opening cycle) in the main scanning direction, the turn-on / off timing of each color LED is determined. Further, as described above, since the luminance of the three light sources and the sensitivity of the sensor have differences and variations depending on the colors, the lighting durations of the light sources of the respective colors are different so that the photoelectric conversion output amounts of the respective colors become equal. Is set to

  The reading control unit 34 determines whether the current time is the switching timing of turning on or off the LED light source 11 of any color (S11).

  If it is not the timing for switching on or off the LED light source 11 of any color (N in S11), the reading control unit 34 supplies a reading clock to the image sensor 12 (S12).

  On the other hand, when it is the switching timing of turning on or off the LED light source 11 of any color (Y in S11), the reading control unit 34 stops supplying the reading clock to the image sensor 12 (S13).

  The reading control unit 34 repeats the processes of S11 to S13 until the output of the shift register data is completed (S14). When the data output is completed (Y in S14), the read clock supply process is terminated.

  As described above, the reading control unit 34 starts the reading clock supply process every time the shift gate is opened.

  This will be specifically described with reference to FIG.

  The “shift signal” in FIG. 4 indicates a shift gate opening pulse. The LED of each color starts to light when the drive pulse changes from “L” to “H”, maintains the light in the “H” state, and turns off the light in “L”.

  As shown in FIG. 4, the LED light source 11 is repeatedly turned on and off in a predetermined cycle in the order of R, G, and B.

  First, the R LED starts to light up, continues to light for a predetermined time, and then turns off. Then, a read clock is supplied from the read control unit 34, the shift gate is opened, charges are transferred to the shift register, the shift registers sequentially transfer charges, and data output to the A / D converter 31 is started. .

  During the data output, the lighting start time of the G LED comes. Conventionally, even in such a case, since the supply of the read clock never stopped, data output to the A / D converter 31 was continued. As a result, noise is mixed into the analog signal. Eventually, the scan image, which is a digital signal, also contains noise (see FIG. 4B).

  On the other hand, in this embodiment, the supply of the read clock is stopped at the switching timing of turning on / off the LED by S13 in FIG. Therefore, the data transfer to the A / D converter 31 is interrupted at the timing that is most easily affected by the switching of turning on / off of the LED.

  Thereby, it can reduce that noise mixes in the data which A / D converter 31 receives.

  Theoretically, it is only necessary to stop the data transfer only at the timing when any one of the LEDs is actually turned on / off.

  However, the turn-off timing is not uniform because the lighting durations of the RGB LEDs are different. If it is determined which LED is actually turned on / off in the reading cycle in the main scanning direction and the timing for stopping the data transfer is changed every time, the processing becomes complicated.

  Therefore, in the present embodiment, regardless of whether or not to actually switch on / off at the timing corresponding to the switching timing of turning on / off the LED of any color in the reading cycle in the main scanning direction, Stop data transfer.

  For example, as shown in FIG. 4, it is assumed that the lighting start time Ts is the same timing from the generation of the “shift signal” for any color LED. In the R, G, and B LEDs, the periods from the start of lighting to the extinguishing are assumed to be Tr, Tg, and Tb, respectively.

  In such a case, the reading control unit 34, when any one of Ts, Tr, Tg, and Tb comes from the generation of the “shift signal” regardless of which LED is turned on, for a predetermined time, Stop supplying.

  Of course, the reading clock may be stopped and data transfer may be stopped only at the switching timing of turning on / off the LED that is actually switched on / off.

  FIG. 5 shows a timing chart of the LED control signal, the read clock, and the analog output.

  As shown in the figure, during a period when the LED is not switched on / off (when the LED is continuously lit or when the LED is lit continuously), a read clock is supplied at a predetermined cycle, and an analog output is generated in the image sensor 12 accordingly. To do. On the other hand, at the switching timing of turning on / off the LED, the reading clock is stopped and the analog output is also stopped.

  The image reading apparatus according to the present embodiment has been described above.

  According to the above-described embodiment, it is possible to reduce mixing of noise into the scanned image when the light source is switched on / off with a simple control method.

  The present invention is not limited to a CIS image reading apparatus. The present invention can also be applied to a reduction optical type image reading apparatus.

1 is a schematic configuration diagram of an image reading apparatus. The block diagram of an image sensor. 6 is a timing chart of supply processing of a read clock supplied to the image sensor. (A) is a timing chart for explaining the stop timing of the read clock in the present embodiment. (B) is a conventional example for comparison. The timing chart of an LED control signal, a reading clock, and an analog output.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image reading apparatus, 10 ... Carriage, 11 ... LED light source, 12 ... Image sensor, 20 ... Drive mechanism, 21 ... Motor, 22 ... Encoder,
DESCRIPTION OF SYMBOLS 30 ... Control part, 31 ... A / D converter, 32 ... Digital data processing part, 33 ... Output part, 34 ... Reading control part

Claims (6)

An image reading apparatus including a light source and an image sensor that converts electric charges accumulated in a photoelectric conversion element into an electrical signal and sequentially outputs the data to an A / D converter,
An image reading apparatus, wherein output of data from the image sensor to an A / D converter is stopped at a switching timing of turning on / off the light source. An image reading apparatus including a light source and an image sensor that converts electric charges accumulated in a photoelectric conversion element into an electrical signal and sequentially outputs the data to an A / D converter,
A controller for supplying a read clock for causing the image sensor to perform data output operation;
The image sensor outputs data according to a read clock supplied from the control device,
The controller is
An image reading apparatus, wherein supply of a reading clock to the image sensor is stopped at a switching timing of turning on and off the light source. The image reading apparatus according to claim 2,
With multiple color light sources,
The controller is
An image reading apparatus, wherein supply of a reading clock to the image sensor is stopped at a switching timing of turning on / off each light source. The image reading apparatus according to claim 2,
The controller is
An image reading apparatus, wherein supply of a reading clock to the image sensor is stopped at a timing corresponding to a switching timing of turning on / off each light source in a reading period in the main scanning direction. An image reading method for an image reading apparatus comprising: a light source; and an image sensor that converts electric charges accumulated in a photoelectric conversion element into an electrical signal and sequentially outputs the data to an A / D converter,
An image reading method for an image reading apparatus, wherein output of data from the image sensor to an A / D converter is stopped at a switching timing of turning on / off the light source. An image reading method for an image reading apparatus comprising: a light source; and an image sensor that converts electric charges accumulated in a photoelectric conversion element into an electrical signal and sequentially outputs the data to an A / D converter,
A controller for supplying a read clock for causing the image sensor to perform data output operation;
The image sensor outputs data according to a read clock supplied from the control device,
The controller is
An image reading method for an image reading apparatus, wherein supply of a read clock to the image sensor is stopped at a switching timing of turning on and off the light source.

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