JP2009212754A - Image reader and image reading method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve image quality by reducing the influence of turning on/off of a light source by a simple control method without increasing the number of components in an image reader. <P>SOLUTION: The image reader has the light source, and an image sensor for successively outputting charge accumulated in a photoelectric transducer as data. The timing of turning on/off the light source is set excluding an effective pixel data output period, where effective pixel data to be obtained as image data are output from the image sensor. <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 image quality of the scanned image after digital conversion 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 problems, the present invention provides:

  An image reading apparatus comprising: a light source; and an image sensor that sequentially outputs charges accumulated in the photoelectric conversion elements as data,

  There is provided lighting timing setting means for setting a switching timing of turning on and off the light source so as to avoid an effective pixel data output period in which effective pixel data to be acquired as image data is output from the image sensor.

  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 a flexible cable. 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 the image reading operation of the image sensor 12. Specifically, a clock (reading clock) for operating the image sensor 12 is supplied to the image sensor 12, and the timing of transferring the data read by the image sensor 12 to the A / D converter 31 is set. Control.

  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. In addition, the total lighting time (total time in the light emission state) in the reading period in the main scanning direction of each LED light source (R, G, B) is determined in advance.

  However, the total lighting time 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 total lighting time is the same, the photoelectrically converted output charge amounts of the respective colors are not equal. Therefore, the total lighting time is set to be different according to the luminance of the three light sources and the sensitivity of the sensor.

  In addition, the reading control unit 34 detects whether the data (effective pixel data) to be finally acquired as image data is output from the image sensor 12 to the A / D converter 31 in order to prevent noise from being mixed. Control is performed so that the switching operation of turning on / off the light source 11 is not performed. This will be specifically described below.

  For example, as shown in FIG. 2, when an L-size photograph is placed on the document table FL and a reading operation is started, any of RGB colors (for example, , R) LED light source 11 is turned on. As the total lighting time at this time, a predetermined time according to the color is secured. During this time, electric charges corresponding to the reflected light of the light of the lit color are accumulated in the photoelectric conversion element PD. Further, when the reading period for one color in the main scanning direction ends, the shift gate SG is opened, and the charge moves to the shift register. The charges moved to the shift register are sequentially transferred on the shift register and sent to the A / D converter 31 through the output unit OUT.

  Even while charges corresponding to the light of the lit color are transferred by the shift register, another color reading operation is performed. That is, switching operation of turning on / off the LED light source 11 of the next color (for example, G) is performed.

  Here, if data is output from the image sensor 12 to the A / D converter 31 and the LED light source 11 is switched on / off, noise may be mixed into the data. In the case of reading over a wide range, since the read image is large, the influence of noise occupying it is small and does not cause much problem. However, when a reading range is specified and a narrow range is read, the influence of noise becomes a problem.

  When reading an L-size photo, effective pixel data, which is data that should be finally obtained as image data, is pixel data corresponding to the range of the L-size photo. If the light source is switched on and off during the output period in which the effective pixel data is sent to the A / D converter 31, noise may be mixed into the effective pixel data.

  Therefore, in the present embodiment, the reading control unit 34 sets the lighting timing so that the switching operation of turning on and off the light source is not performed as much as possible during the effective pixel data output period.

  The reading control unit 34 and the digital data processing unit 32 include a CPU that is a main control device, a ROM that stores programs and the like, a RAM that temporarily stores data and the like as a main memory, and a host and the like. This can be achieved by a computer having an interface for controlling input / output and 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, the lighting timing control of the LED light source, which is a characteristic operation of the image reading apparatus 1 of the present embodiment, will be described with reference to FIGS.

  FIG. 3 is a flowchart of lighting timing control. FIG. 4 is a timing chart showing the lighting timing of the LED light source 11 according to the document range. Note that “TGCK” in FIG. 4 corresponds to the opening pulse of the shift gate. The LED light source 11 starts lighting when the driving pulse changes from “L” to “H”, maintains lighting in the “H” state, and turns off when the driving pulse changes to “L”.

  First, the reading control unit 34 determines the total lighting time Ta for the LED light source 11 of the color whose lighting timing is to be set (S11). As described above, the luminance of the three light sources and the sensitivity of the sensor have differences and variations depending on the colors. Therefore, the different lighting total times Ta are adjusted and set so that the photoelectric conversion output amounts of the respective colors become equal. . The total lighting time Ta for each color of the LED light source 11 is adjusted and determined by a predetermined procedure.

  Next, the reading control unit 34 determines whether or not the reading main scanning width set as the reading condition is equal to or less than a predetermined range (for example, L-size photo reading: 3.5 inches) (S12). . If it is not less than the predetermined range, a conventional lighting operation is performed (S13). Specifically, the reading controller 34 reads a predetermined color at predetermined intervals at predetermined intervals regardless of whether pixel data is being output from the image sensor 12 to the A / D converter 31 during reading in the main scanning direction. The LED light source 11 is turned on / off. However, the actual total lighting time is controlled to be the total lighting time determined in S11 (see FIG. 4).

  When the reading range is not specified, the reading control unit 34 may perform the process of S13 on the assumption that reading of the entire range is specified.

  On the other hand, when the set reading main scanning width is reading within a predetermined narrow range (for example, reading of L size photo: 3.5 inches) (Y in S12), the reading control unit 34 performs the processing after S14. I do.

  First, the reading control unit 34 calculates an effective pixel data output period from the designated reading main scanning width (S14).

  As shown in FIG. 2, the effective pixel data output period differs depending on which part of the original table FL area the reading main scanning range is set to. For example, the closer the reading main scanning range is to the output unit OUT side, the earlier the start timing of the effective pixel data output period. Further, the wider the reading range, the longer the effective pixel data output period.

  FIG. 4 shows an example of the operation corresponding to the main scanning range in which the L size photo is arranged when the L size photo is read by a general A4 size scanner. That is, the user does not enter the output period of the effective pixel data at any main scanning position of the L size photograph (3.5 inch width) at any main scanning position.

  Here, the time required for outputting 0.1 inch of pixel data is 1T. The shift cycle of one reading line is shown as 92T that is equal to or longer than the time during which all the pixel data for one line (maximum effective pixel 8.5 inches = 85T) is output.

  The document range (1) indicates the control when the L-size photograph is in the range of 0 to 4.6 inches from the output unit OUT side in the scanner effective reading range.

  Document range (2) indicates control when an L-size photograph is placed within a range of 1.1 to 5.7 inches from the output unit OUT side.

  Similarly, the document ranges (3), (4), and (5) are 2.2 to 6.8, 3.3 to 7.9, and 4.4 to 8.5 inches from the output unit OUT side, respectively. The control when an L size photograph is placed within the range of is shown.

  In the document range (1), the output start timing of the effective pixel data (data in the range of the L size photograph) to the A / D converter 31 is the earliest. In the document ranges (2), (3), (4), and (5), the output start timing of the effective pixel data to the A / D converter 31 is delayed in this order.

  Further, since the adjacent document ranges overlap each other by 3.5 inches, control of any document range can be performed regardless of the location of the L-size photograph. This document range control pattern is registered in advance as a table together with the corresponding document width value.

  Using the table, the reading control unit 34 acquires the effective pixel data output period (start time, end time) from the set read main scanning range.

  Next, the reading control unit 34 sets a period (Tp−Tout) in which the LED lighting total time Ta acquired in S11 is not the effective pixel data output period Tout acquired in S14 as the reading period Tp for one cycle in the main scanning direction. It is determined whether or not (S15). That is, it is determined whether Ta> Tp−Tout is satisfied.

  4A shows a case where Ta> Tp−Tout is not satisfied (that is, Ta ≦ Tp−Tout), and FIG. 4B shows a case where Ta> Tp−Tout.

  When Ta> Tp−Tout is not satisfied (N in S15), the reading control unit 34 sets the lighting timing of the LED light source 11 according to such a case (S16).

  Specifically, the reading control unit 34 holds the LED light source 11 in the off state during the effective pixel data output period. On the other hand, during a period other than the valid data output period, the LED light source 11 is turned on and the actual total lighting time is set to be the total lighting time Ta determined in S11.

  When the effective pixel data output period starts from almost the beginning of the reading cycle as in the document range (1) in FIG. 4, the effective pixel data cannot be turned on before the start of the effective pixel data output period. After the output period has elapsed, the lighting timing of the LED light source 11 is set.

  Image reading is performed while moving the carriage 10 in the sub-scanning direction. Therefore, in order to avoid unevenness in the sub-scanning direction, it is better not to unevenly distribute the lighting period. Therefore, the reading control unit 34 performs “intermittent lighting” that repeats lighting and extinguishing a plurality of times at predetermined intervals for a predetermined time, and sets the lighting timing so that the total lighting time Ta determined in S11 is ensured. Set. That is, the intermittent lighting period is assigned according to the document range pattern so that the LED lighting period is not sparse.

  In the example of FIG. 4, in the case of the document range (1), the period other than the effective pixel data output period is 46T after the effective pixel data output period. Accordingly, if the lighting is equally divided into four times, the reading control unit 34 sets the lighting timing so that the lighting is performed four times at 11.5T intervals after the effective pixel data output period.

  In the case of the document range (2), there are 11T before the effective pixel data output period and 35T after the effective pixel data output period. Therefore, if the lighting is divided into four times, the reading control unit 34 is turned on once before the effective pixel data output period, and is turned on three times at an interval of 35 T / 3 after the effective pixel data output period. Set the lighting timing.

  In the case of the document range (3), there are 22T before the effective pixel data output period and 22T after the effective pixel data output period. Therefore, if the lighting is divided into four times, the reading control unit 34 lights twice at an interval of 11T before the effective pixel data output period, and lights twice at an interval of 12T after the effective pixel data output period. In this way, the lighting timing is set.

  In the case of the document range (4), there are 33T before the effective pixel data output period and 13T after the effective pixel data output period. Therefore, if the lighting is divided into four times, the reading control unit 34 is lit so that it is lit three times at an interval of 11T before the effective pixel data output period and is lit once after the effective pixel data output period. Set the timing.

  In the case of the document range (5), the period other than the effective pixel data output period is 44T before the effective pixel data output period. Accordingly, if the lighting is divided into four times, the reading control unit 34 sets the lighting timing so that the lighting is performed four times at an interval of 11T before the effective pixel data output period.

  On the other hand, when Ta> Tp−Tout (Y in S15), the reading control unit 34 sets the lighting timing of the LED light source 11 according to such a case (S17).

  Specifically, the reading control unit 34 holds the LED light source 11 in a lighting state during the effective pixel data output period. On the other hand, even during a period other than the valid data output period, the LED light source 11 is turned on, and the lighting timing is set so that the actual total lighting time becomes the total lighting time Ta acquired in S11.

  When the effective pixel data output period starts from almost the beginning of the reading cycle as in the document range (1) in FIG. 4, the LED light source 11 is simultaneously with (or before) the start of the effective pixel data output period. Lights up. The lighting state is maintained during the effective pixel data output period, and the light is turned off after the effective pixel data output period ends. Further, after the effective pixel data output period elapses, the reading control unit 34 repeats lighting / extinguishing a plurality of times at a predetermined interval so that the actual total lighting time becomes the total lighting time Ta determined in S11. Set the lighting timing.

  In the case of the document range (1), if the lighting is divided into four times, the reading control unit 34 sets the lighting timing so that the lighting is performed three times at 11.5T intervals after the effective pixel data output period.

  Similarly, in the case of the document ranges (2) to (5), the lighting timing is set so that the lighting is repeated at predetermined intervals so that the lighting time is not unevenly distributed before or after the effective pixel data output period.

  In any case, the reading control unit 34 sets the lighting timing so that the actual total lighting time is equal to the predetermined total lighting time acquired in S12.

  In this way, when the lighting timing is set, the reading control unit 34 ends the process of FIG.

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

  According to the above embodiment, when the reading range is narrow and the influence of noise becomes a problem, the switching operation of turning on / off the light source is performed avoiding the data output period from the image sensor 12. Therefore, with a simple control method, it is possible to reduce the mixing of noise into the scanned image when the light source is switched on / off.

  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. The flowchart of the lighting timing control process of a LED light source. The timing chart for demonstrating the lighting timing of a LED light source.

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 comprising: a light source; and an image sensor that sequentially outputs charges accumulated in the photoelectric conversion elements as data,
An image reading comprising: a lighting timing setting means for setting a switching timing of turning on and off the light source while avoiding an effective pixel data output period in which effective pixel data to be acquired as image data is output from the image sensor apparatus. The image reading apparatus according to claim 1,
A total lighting time acquisition unit for acquiring a total lighting time of the light source in a reading cycle in the main scanning direction;
The lighting timing setting means includes
During the effective pixel data output period, the light source is held off,
In a period that is not the effective pixel data output period, the light source is turned on,
An image reading apparatus characterized by controlling so that a total time of an actual lighting state becomes a total time acquired by the total lighting time acquisition unit. The image reading apparatus according to claim 1,
A total lighting time acquisition unit for acquiring a total lighting time of the light source in a reading cycle in the main scanning direction;
The lighting timing setting means includes
During the effective pixel data output period, the light source is kept in a lighting state,
In a period that is not the effective pixel data output period, the light source is turned on,
An image reading apparatus characterized by controlling so that a total time of an actual lighting state becomes a total time acquired by the total lighting time acquisition unit. The image reading apparatus according to claim 1,
A total lighting time acquisition unit for acquiring a total lighting time of the light source in a reading cycle in the main scanning direction;
The lighting timing setting means includes
When the total time of the predetermined lighting time does not exceed a period that is not the effective pixel data output period in the reading cycle in the main scanning direction,
During the effective pixel data output period, the light source is held off,
In a period that is not the effective pixel data output period, the light source is turned on, and the total time of the actual lighting state is controlled to be the total time acquired by the total lighting time acquisition unit,
When the total time of the predetermined lighting time exceeds a period that is not the effective pixel data output period in the reading cycle in the main scanning direction,
During the effective pixel data output period, the light source is kept in a lighting state,
The image reading is characterized in that the light source is turned on during a period that is not the effective pixel data output period, and the total time of the actual lighting state is controlled to be the total time acquired by the total lighting time acquisition unit. apparatus. The image reading apparatus according to any one of claims 1 to 4,
The lighting timing setting means intermittently lights the light source. An image reading method of an image reading apparatus comprising: a light source; and an image sensor that sequentially outputs charges accumulated in photoelectric conversion elements as data,
An image reading method for an image reading apparatus, wherein a switching timing for turning on and off the light source is set so as to avoid an effective pixel data output period in which effective pixel data to be acquired as image data is output from the image sensor. .

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