JP5195703B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus.

Conventionally, an image reading apparatus that reads an image by using an LED or the like as a light source and illuminating the original with the light source turned on has been adjusted by changing the drive current and lighting time of the LED to obtain an optimum light amount. . The image reading apparatus reads an image of a document by turning on the light source under the adjusted drive current and lighting time.
For example, the invention described in Patent Document 1 discloses a technique related to an image reading apparatus that reads an image of a document after adjusting an LED lighting current and a lighting time for each reading condition such as monochrome or color before reading the image of the document. Has been.

JP 2000-287036 A

  However, in the case of a conventional image reading apparatus, when reading an image of a document, the same light amount adjustment operation of the light source is repeatedly performed for each document. In addition, the time required for adjusting the light amount of the light source was spent.

  The present invention has been completed based on the above circumstances, and in the case where it is not necessary to adjust the light amount of the light source, it is the LED driving current and lighting time when the light amount has been adjusted before. An object of the present invention is to provide an image reading apparatus capable of shortening the time required to actually start reading because an original can be read using the adjustment parameters.

In order to achieve the above object, an image reading apparatus according to a first aspect of the present invention includes a reading unit including a light source that emits light and a plurality of light receiving elements that receive the light reflected from the light . A reference member having a predetermined reflectivity, a storage unit, and a control unit, and the control unit uses the light source to light the reading unit before the reading unit reads an image of a document. is irradiated with a maximum value of the voltage for outputting reflected light to each light receiving element receiving from said reference member, so that the predetermined value is at least one of the driving current or the lighting time of the light source adjustment a light amount adjustment process of adjusting the parameters, the by irradiating light quantity adjusting the light source using the adjustment parameter adjusted by processing with respect to the reference member, the predetermined one of the voltage output the each light-receiving element Is less than the value Running and adjusted and acquires the number of values over voltage, in the storage means, and a first storage processing for storing the number of the adjusted adjustment parameter and the threshold voltage equal to or higher than in the light amount adjusting means The control unit causes the light source to irradiate the reference member with light using the adjustment parameter stored in the storage unit when the reading unit reads the image of the document. A pre-reading control process for acquiring each voltage output for each element; a determination process for determining whether all of the voltages output by the reading unit by the pre-reading control process are equal to or less than the predetermined value; a determining process for determining whether the number of the threshold voltage higher than among the voltages which the reading means is output by the pre-reading control process is not less than the number stored in the storage unit, the determination process wherein Each voltage Determines that all is less than the predetermined value, and, when the determination process determines that more than a few that are the storage, said reading means by irradiating a light source using the adjustment parameter stored in said storage means When the document is controlled to be read and the determination process determines that at least one of the voltages exceeds the predetermined value, or when the determination process determines that the number is less than the stored number, run the light amount adjustment process, the reading unit using the adjustment parameter that is adjusted is controlled to read an original, executes image reading control process and the is characterized and this.

According to the first aspect of the invention, when the reading unit reads the image of the document, the reading unit reads the reference member under the control of the control unit . Then, the determination unit determines that all the voltages output by the reading unit are equal to or less than a predetermined value, and the number of voltages equal to or higher than the threshold among the voltages output by the reading unit reads the image of the document. When the number of voltages is equal to or greater than the threshold value previously stored in the storage unit, it is not necessary to adjust the light amount of the light source of the reading unit. Since the image reading apparatus can read the original by turning on the light source using the adjustment parameter stored in advance in the storage means, the reading means actually reads the original when reading the image of the original. The time to start can be shortened.

1 is a schematic diagram of an image scanner 1 that reads an image of a document. 2 is a block diagram showing an electrical configuration of the image scanner 1. FIG. The flowchart of the process at the time of power activation. 5 is a flowchart of light amount adjustment processing of a light source 22 of a reading device 21. The figure which showed the voltage value of the output signal which each light receiving element of the reading device 21 outputs. 10 is a flowchart of processing when the reading device 21 reads a document P. The figure which showed the voltage value of the output signal which each light receiving element of the reading device 21 before reading the original P outputs.

An embodiment of the present invention will be described with reference to FIGS.
[Configuration of MFP]

  FIG. 1 is a schematic diagram of an image scanner 1 (an example of an image reading apparatus) that reads an image of a document. The image scanner 1 is configured as a so-called flatbed scanner device, and includes an apparatus main body 3 having a platen glass 13 on which an original is placed, and an FB cover 5 provided to be openable and closable above the apparatus main body 3. It is prepared for.

  The apparatus body 3 includes a platen glass 13 that constitutes a first reading surface 11 and a second reading surface 12, a housing 20 that supports the platen glass 13, and a document placed on the first reading surface 11. , A white reference plate 19 having a predetermined reflectance, a reading device 21 (an example of a reading unit), an FB motor 23 and a belt mechanism unit 25 that move the reading device 21, It has.

  The surface of the platen glass 13 is divided into a first reading surface 11 and a second reading surface 12 by a positioning member 17 that is detachably attached to the housing 20. The first reading surface 11 is an area for a user to read a document placed on the surface, and is covered with the FB cover 5 with the FB cover 5 closed. The second reading surface 12 is an area for reading the document P conveyed by the document conveying device 40 provided on the FB cover 5.

  The reading device 21 is accommodated on the back surface of the platen glass 13 so as to be movable in the sub-scanning direction (D direction in the drawing) parallel to the surface of the platen glass 13. The reading device 21 is fixed to a belt 25b wound around a pair of rollers 25a provided in the belt mechanism unit 25, and moves in the sub-scanning direction together with the belt 25b that is rotated by the power generated by the FB motor 23.

  The white reference plate 19 (an example of a reference member) is disposed between the positioning member 17 and the platen glass 13 in a posture extending in the main scanning direction perpendicular to the paper surface. The white reference plate 19 is a white member having a high reflectance, and is used to generate a white reference value for light amount adjustment and shading correction of the light source 22 (see FIG. 2).

  When reading the document P conveyed on the second reading surface 12 by the operation of the document conveying device 40 provided on the FB cover 5, the reading device 21 is moved below the second reading surface 12 and stopped. Further, when reading a document on the first reading surface 11, the reading device 21 is conveyed in the sub-scanning direction on the back side of the first reading surface 11 by operations of the FB motor 23 and the belt mechanism unit 25.

  The FB cover 5 includes the document conveying device 40 as described above, and conveys the document P placed on the paper feed tray 41 onto the second reading surface 12 as described below, and The document read by the reading device 21 on the reading surface 12 is discharged to a discharge tray 42.

The document transport device 40 includes paper feed rollers 44 and 45 at the start point of the transport path, and the document placed on the paper feed tray 41 is transported downstream of the transport path by the paper feed rollers 44 and 45. The original P conveyed by the paper feed rollers 44 and 45 is further conveyed downstream of the conveyance path by the first conveyance rollers 47 and 48.
An upper plate 49 that opposes the second reading surface 12 is provided downstream of the first conveying rollers 47 and 48 in the conveying path with a predetermined gap from the second reading surface 12. . The document P transported by the first transport rollers 47 and 48 passes between the upper plate 49 and the second reading surface 12 and is further paired with a second second path provided downstream of the transport path. The paper is transported by transport rollers 51 and 52, and is then discharged to the paper discharge tray 42 by a pair of third paper discharge rollers 53 and 54.

[Electrical configuration of image scanner]
FIG. 2 is a block diagram showing an electrical configuration of the image scanner 1. The image scanner 1 includes an ASIC 100, a CPU 101 (an example of a control unit) , a ROM 102, a RAM 103, an EEPROM 104 (an example of a registered unit and a storage unit) , an FB motor 23, an FB motor drive circuit 105, an ADF motor 110, an ADF motor drive circuit 106, A reading device 21, a current control circuit 121, an A / D conversion circuit 123, and the like are provided.

As shown in the figure, an FB motor drive circuit 105, an ADF motor drive circuit 106, a current control circuit 121, an A / D conversion circuit 123 (an example of A / D conversion means), and the like are connected to the ASIC 100. The ASIC 100 controls these under the control of the CPU 101 and generates image data by performing gamma correction, shading correction, and other various image processing on the output value output from the A / D conversion circuit 123.
Note that gamma correction, shading correction, and other various types of image processing may be performed by the CPU 101 instead of the ASIC 100.

  The reading device 21 includes a light source 22R in which a plurality of LEDs emitting red (R) light are arranged in one row in the extending direction of the line sensor 26, and a plurality of LEDs emitting green (G) light in one row. And a light source 22 configured by a light source 22B in which a plurality of LEDs emitting blue (B) light are arranged in a line. The light sources 22R, 22G, and 22B are turned on according to the magnitude of the drive current supplied from the current control circuit 121.

  A light source 22 of the reading device 21 is connected to the current control circuit 121. The current control circuit 121 supplies current to the light source 22 based on the PWM signal output as a pulse signal from the ASIC 100.

The CPU 101 is lit for each of the light sources 22R, 22G, and 22B by adjusting the duty ratio between the period in which the PWM signal is output and the period in which the PWM signal is not output in each line cycle via the ASIC 100 for each of the light sources 22R, 22G, and 22B. The time can be adjusted.
The drive current and lighting time of the light source 22 may be adjusted by the ASIC 100 instead of the CPU 101.

  The reading device 21 further includes a line sensor 26 in which 10122 light receiving elements from 0 to 10121 are arranged one-dimensionally in the main scanning direction in order to read 1200 dpi with an A4 width. The line sensor 26 composed of a plurality of light receiving elements emits light from the light source 22 for each light receiving element, and as an analog output signal according to the amount of reflected light from the document or the white reference plate 19. Each voltage value is output.

  The A / D conversion circuit 123 is a circuit that converts each voltage (analog) output from each light receiving element 26 into an output value (pixel value) that is a digital signal. The A / D conversion circuit 123 of the present embodiment has a resolution that decomposes the voltage range into 8 bits (0 to 255).

[Light intensity adjustment at power-on]
FIG. 3 shows a flowchart of processing when the image scanner 1 is powered on. In the present embodiment, when the image scanner 1 is powered on, the process of FIG. 3 is executed.

  As shown in FIG. 3, in this process, first, in S101 (S represents a step: the same applies hereinafter), the motor driving unit 105 drives the FB motor 23, whereby the reading device 21 is moved to the white reference plate 19 as shown in FIG. Is moved to the opposite position.

  Next, in S102, the light amount of the light source 22 is one of the adjustment parameters that can adjust the light amount by the light amount adjustment process described later (lighting time of each light source 22R, 22G, 22B within one line period). ). In S103, in a state where the light source 22 is turned on using the lighting time adjusted in S102, the reflected light of the white reference plate 19 is read using the reading device 21, and the reading device 21 outputs each light receiving element. The voltage is converted by the A / D conversion circuit 123, and the CPU 101 acquires the maximum value of each output value as a so-called white reference value.

  Next, in S104, the reading device 21 performs reading with the light source 22 extinguished, and the CPU 101 converts the output voltage output from the reading device 21 for each light receiving element by the A / D conversion circuit 123. The minimum value of the output value is acquired as a so-called black reference value.

  In step S105, the CPU 101 functioning as a shading correction data generation unit obtains shading correction data for correcting the variation between the light receiving elements from the difference between the white reference value and the black reference value for each light receiving element. In the process of S314 in FIG. 6 to be described later, the output value for each light receiving element from which the reading device 21 has read the document P is corrected by using this shading correction data, so that the output variation between the light receiving elements is varied. It can be prevented from occurring.

In S106, the shading correction data acquired in S105 is stored in the EEPROM 104. Then, the process of FIG. 3 ends.

[Flow chart of light intensity adjustment processing]
FIG. 4 is a flowchart when the CPU 101 executes the light amount adjustment process of the light source 22 of the reading device 21 in S102 of FIG. In the present embodiment, a lighting time, which is one of adjustment parameters for adjusting the light amount of each light source 22 by adjusting how much each light source is turned on within one line cycle, will be described.

  In S <b> 201, as an initial setting, the CPU 101 acquires a value for lighting the light source 22 over the entire one-line cycle as an initial value of the lighting time stored in the ROM 102.

  In S202, the CPU 101 controls the reading device 21 to read the white reference plate 19 for one line period using the lighting time acquired in S201, and the reading device 21 outputs the voltage of the output signal for each light receiving element. Is output.

  Then, the output voltage of the output signal of each light receiving element is converted into a digital output value by the A / D conversion circuit 123, respectively. In S203, the A / D conversion circuit 123 outputs even one signal exceeding the maximum voltage level that the A / D conversion circuit 123 can convert, such as “255” (an example of a predetermined value when 8 bits). If so, the CPU 101 determines that there is an overflowing light receiving element (S203: YES). When no signal exceeding the maximum voltage level that can be converted by the A / D conversion circuit 123 is output, it is determined that there is no light receiving element that overflows (S203: NO).

  If YES is obtained in S203, the CPU 101 decreases the lighting time of the light source 22 by one step.

  When S204 ends, the process returns to S202 again, and the light source 22 is turned on using the lighting time reduced by one step in S204. The CPU 101 controls the reading device 21 to read the white reference plate 19, and the reading device 21 receives each light. The voltage of the output signal is output for each element.

In S203, the maximum value among the voltage values output by the respective light receiving elements of the reading device 21 is equal to or lower than the maximum voltage level that can be converted by the A / D conversion circuit 123, and there is no overflowing light receiving element, that is, the CPU 101 overflows. The process of S202, S203, and S204 is repeated until it is determined that it has not been made (S203: NO). Then, in S205, the value of the lighting time adjusted by the processing Ru stored in the EEPROM 104.

  FIG. 5 is a supplementary explanation of the light amount adjustment described above, using a diagram schematically showing the voltage value of the output signal output from each light receiving element of the reading device 21. In FIG. 5, the horizontal axis indicates each light receiving element, and the vertical axis indicates the voltage value output by the light receiving element, which is an output value obtained by digital conversion. RefH indicates the maximum voltage level that can be converted by the A / D conversion circuit 123. Specifically, the digitally converted value converted by the A / D conversion circuit 123 is “255”. In FIG. 5, only 14 light receiving elements are shown for the sake of illustration, but in actuality, there are 10122 light receiving elements.

  5 schematically shows the voltage value of the output signal before the light amount adjustment. In the thin line, the eighth to thirteenth light receiving elements exceed RefH (255). That is, this corresponds to the case where it is assumed that there is an overflowing light receiving element in S203 of FIG.

  The thick line in FIG. 5 schematically shows the voltage value of the output signal after the light amount adjustment. In the thick line, there is no light receiving element exceeding RefH (255), and the maximum value (11th light receiving element) among the voltages of the output signal output from the reading device 21 matches RefH (255). It is like that.

  When the voltage output by the eighth to thirteenth light receiving elements before light amount adjustment in FIG. 5 is converted using the A / D conversion circuit 123, the maximum voltage level that the A / D conversion circuit 123 can convert is exceeded. . Therefore, the A / D conversion circuit 123 outputs all the values “255” as the converted voltage values of the eighth to thirteenth light receiving elements. In that case, the output value output for each light receiving element from the A / D conversion circuit 123 cannot appropriately represent the gradation level of 0 to 255 as image data. Therefore, the drive current of the light source 22 is adjusted so that there is no light receiving element exceeding RefH (255) as shown by the thick line in FIG.

Next, in S <b> 206, the CPU 101 acquires the number of light receiving elements that output the voltage value of the output signal equal to or higher than the threshold A among the voltage values of the output signals output by the light receiving elements of the reading device 21. .

  In the present embodiment, a value “230” is stored in the ROM 102 as the threshold A. This value corresponds to RefA in FIG. The threshold A is a value less than RefH (255).

  S206 will be described in detail. The CPU 101 compares the value of the threshold A “230” with the voltage value converted by the A / D conversion circuit 123 for each light receiving element, and the light receiving element exceeding the threshold A “230”. Count the number of

  In S207, the number of light receiving elements exceeding the threshold A “230” obtained in S206 is stored in the EEPROM 104. In the example of FIG. 5, since the seventh to thirteenth light receiving elements exceed the threshold value A “230”, the value of seven light receiving elements that output the voltage value of the output signal equal to or higher than the threshold value A is 7. It is stored in the EEPROM 104. Then, the process of FIG. 4 ends.

  In the present embodiment, the lighting time is exemplified as the adjustment parameter for adjusting the light amount of the light source 22, but the present invention is not limited to this. For example, instead of the lighting time of FIG. 4, the driving current of the light source 22 may be used as an adjustment parameter. Alternatively, the light amount of the light source 22 may be adjusted in such a manner that the lighting time is adjusted again after adjusting the drive current.

[Image reading process]
Next, a flowchart of processing when the reading device 21 reads the document P will be described with reference to FIG. First, in S301, similarly to S101, the motor driving unit 105 drives the FB motor 23, whereby the reading device 21 is moved to a position facing the white reference plate 19.

EEPROM 10 4 The value of the driving current is adjusted parameter adjusted is stored in, CPU 101 acquires (S302).

The CPU 101 controls the reading device 21 to read the reflected light from the white reference plate 19 using the lighting time stored in S205, and the reading device 21 outputs the voltage of the output signal for each light receiving element. (S303).

  In S304, whether the maximum value among the voltage values output by each light receiving element of the reading device 21 exceeds the maximum voltage level that can be converted by the A / D conversion circuit 123, that is, whether there is an overflowing light receiving element. The CPU 101 that functions as a determination unit determines whether or not. In S304, when there is an overflowing light receiving element (S304: YES), the above-described light amount adjustment processing of FIG. 4 is performed to adjust the lighting time as an adjustment parameter of the light source 22 (S308).

  When there is no overflowing light receiving element (S304: NO), the CPU 101 compares the value of the threshold A “230” with the voltage value converted by the A / D conversion circuit 123 for each light receiving element. The number of light receiving elements exceeding the threshold A “230” is counted.

  In S305, the CPU 101 functioning as a determination unit determines whether the number of light receiving elements exceeding the threshold A “230” stored in S207 and the number of light receiving elements exceeding the threshold A “230” are exceeded. Determine. If the CPU 101 determines that it has exceeded, the process proceeds to S306. If it has not exceeded, the light amount adjustment processing of FIG. 4 is performed, and the lighting time as the adjustment parameter of the light source 22 is readjusted ( S308).

  FIG. 7 illustrates a case where YES is determined in S305. The reading device 21 before reading the original P reads the reflected light from the white reference plate 19, and the output signals output from the respective light receiving elements are illustrated. It is the figure which showed the voltage value typically. In FIG. 5, a value of 7 is stored in the EEPROM 104 as the number of light receiving elements exceeding the threshold A “230”. In FIG. 7, the number of light receiving elements exceeding the threshold A “230” is nine, and the number of light receiving elements exceeding the threshold A “230” stored in S207 of FIG.

  In the case as shown in FIG. 7, there is little change compared to the light amount adjustment in S207 in advance, and the image scanner 1 turns on the light source 22 using the drive current that is the adjustment parameter obtained in S207, and the document. Even if an image of P is read, a result comparable to that can be obtained.

Therefore, in step S <b> 306, the CPU 101 controls to turn on the light source 22 and read the image of the document P using the lighting time value that is an adjustment parameter stored in the EEPROM 104.

Further , the CPU 101 performs shading correction on the output value converted by the reading device 21 by the reading A / D conversion circuit 123 using the shading correction data stored in the EEPROM 104 (S307).

On the other hand, the processing of S308 to S311 is equivalent to the processing of S102 to S105 of FIG. 3, and the light amount adjustment processing of S308 and the shading correction data of S311 are recreated. In step S312, the shading correction data created in step S311 is updated from the previously stored data and stored in the EEPROM 104. And
The original P is read by turning on the light source 22 using the adjustment parameter adjusted in S308 (S313), and the result of the reading is subjected to shading correction using the shading correction data created in S311.

Comparing the case where S305 is YES and the case where NO is obtained, if YES is obtained in S305, it is not necessary to execute the light amount adjustment processing in S308 and to recreate the shading correction data in S311. It is possible to shorten the time until the actual reading is started.

P Document 1 Image scanner 3 Device body 5 FB cover 11 First reading surface 12 Second reading surface 13 Platen glass 17 Positioning member 19 White reference plate (an example of a reference member)
20 Housing 21 Reading device (an example of reading means)
22 Light source (an example of a light source)
26 Line sensor (an example of a light receiving element)
101 CPU (an example of control means)
104 EEPROM ( an example of storage means)
121 current control circuit 123 A / D conversion circuits

Claims (1)

Reading means comprising a light source for irradiating light, and a plurality of light receiving elements for receiving the light reflected from the light ;
A reference member having a predetermined reflectance;
Storage means;
Control means;
With
The control means includes
Before the reading means reads the image of the document,
Wherein by irradiating light to the reference member by using the light source, so that the maximum value of the output voltage of the reflected light to each light receiving element receiving from said reference member becomes the predetermined value, the light source A light amount adjustment process for adjusting an adjustment parameter that is at least one of the driving current or the lighting time of
The light source irradiates the reference member with light using the adjustment parameter adjusted by the light amount adjustment processing , and a voltage equal to or higher than a threshold value that is less than the predetermined value among the voltages output for each light receiving element . Post-adjustment processing to get the number,
A first storage process for storing, in the storage unit, the adjustment parameter adjusted by the light amount adjustment unit and the number of voltages equal to or greater than the threshold;
Run
The control means includes
When the reading unit reads an image of a document,
A pre-reading control process in which the light source irradiates the reference member with light using the adjustment parameter stored in the storage unit, and each voltage output for each light receiving element is acquired;
A determination process for determining whether all of the voltages output by the reading unit by the pre-reading control process are less than or equal to the predetermined value;
A determination process for determining whether or not the number of voltages equal to or greater than the threshold value among the voltages output by the reading unit by the pre-reading control process is equal to or greater than the number stored in the storage unit ;
When the determination process determines that all of the voltages are less than or equal to the predetermined value, and the determination process determines that the number is greater than or equal to the stored number, a light source is used using the adjustment parameter stored in the storage means. controlled to read the reading means by irradiating the document and when the determination process but wherein at least one of the voltage is determined to exceed the predetermined value, or the number of the determination processing is the storage Executing the light amount adjustment process when it is determined that the reading means is less than, and performing the image reading control process for controlling the reading unit to read the document using the adjusted adjustment parameter,
Image reading device comprising a call.