JPH09116702A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image with quality stable at all times in the read operation mode set by a user by correcting fluctuation in a luminous quantity caused by a drive state of the image reader with a configuration where a power supply for a light source is used in common for other drive components in the reader. SOLUTION: Luminous quantity correction data in response to the read operation mode set by the user are prepared based on a read operation in the reading of a density reference board and the data are stored in a ROM 27, and when image information of an original is read, a CPU 26 reads optimum correction data corresponding to the read operation mode set by the user are read out of the ROM 27 to correct a power supply voltage applied to a light source 7 thereby correcting the fluctuation in the luminous quantity due to the driven reader.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device such as an image scanner device, a digital copying machine, and a digital facsimile device for digitally reading image information on an original, and more particularly to controlling a power supply voltage supplied to a light source. The present invention relates to an image reading device that compensates for fluctuations in the light amount of a light source and stabilizes the image reading operation.

[0002]

2. Description of the Related Art In an image reading apparatus, a method of controlling a cycle of a signal (SH signal) that determines a charge storage time of a photoelectric conversion element is known as a means for correcting a variation in light quantity. Also, depending on the condition of the document to be scanned,
There is also a method of obtaining the necessary conversion characteristics by adjusting the charge storage time of the photoelectric conversion element (Japanese Patent Laid-Open No. 6-25314).
No. 9).

[0003]

However, in the above-mentioned conventional image reading apparatus, when the period of the signal (SH signal) that determines the charge accumulation time of the photoelectric conversion element is controlled, the image at the stage subsequent to the photoelectric conversion element is controlled. This S in the processing section etc.
When the H signal is shared, there is a problem that the circuit configuration becomes complicated because the cycle of the SH signal is variable. In view of the above-mentioned circumstances, the present invention corrects the fluctuation of the light amount generated by the driving state of the device in an image reading device having a configuration in which the power source of the light source is shared with other driving parts in the device, and the user sets it. It is an object of the present invention to provide an image reading apparatus that can always obtain an image of stable quality even when operating in a possible reading operation mode.

[0004]

In order to achieve the above object, the present invention according to claim 1 operates in a reading operation mode designated through a user interface to emit light from a light source and read the light. While illuminating the target document, the reflected light or transmitted light is photoelectrically converted by a photoelectric conversion element,
In an image reading device that extracts image information on the document as an electric signal, a memory in which correction data corresponding to each reading operation mode is registered, and a reading operation mode in the memory when the reading operation mode is designated through the user interface Based on the correction data reading unit that reads the correction data corresponding to the reading operation mode designated via the user interface from among the registered correction data, and the correction data read by the correction data reading unit And controlling the power supply unit to adjust the value of the power supply voltage applied to the light source to correct the fluctuation of the light amount of the light source.

According to a second aspect, in the image reading apparatus according to the first aspect, the power source unit that supplies the power source voltage to the light source that illuminates the document to be read and the power source voltage to the components of the drive system. The power supply unit is installed independently, and the value of the power supply voltage output from each power supply unit is controlled according to the reading operation mode specified via the user interface.

In the above structure, according to the first aspect of the invention, the reading operation mode designated through the user interface is operated to emit light from the light source to illuminate the document to be read while reflecting the reflected light or the reflected light. In the image reading device that photoelectrically converts the transmitted light by the photoelectric conversion element and extracts the image information on the original as an electric signal, when the reading operation mode is specified through the user interface, the correction data reading unit stores the data in the memory. Of the registered correction data, the correction data corresponding to the reading operation mode designated via the user interface is read, and the power supply unit control unit reads the correction data read by the correction data reading unit. And controlling the power supply unit to adjust the value of the power supply voltage applied to the light source. By correcting the light quantity fluctuation,
Even in an image reading device having a configuration in which the power source of the light source is shared with other driving parts in the device, the fluctuation of the light amount caused by the driving state of the device is corrected, and the reading operation mode that can be set by the user is always stable. Get quality images.

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the power source unit that supplies the power source voltage to the light source that illuminates the document to be read and the power source voltage to the components of the drive system. The power supply unit is installed independently, and the value of the power supply voltage output from each of the power supply units is controlled according to the reading operation mode specified via the user interface, so that the power supply of the light source is controlled in the apparatus. Even in the image reading apparatus having a configuration shared with other driving components, the fluctuation of the light amount caused by the driving state of the apparatus is corrected, and an image of stable quality is always obtained in the reading operation mode that can be set by the user.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a perspective view showing an example of an image reading apparatus according to the present invention. The image reading apparatus 1 shown in this figure has an automatic paper feeder 3 on the top of the apparatus main body 2.
Is rotatably attached to the apparatus main body 2 about a support shaft (not shown) provided on the front side (left side in FIG. 1) in the sheet discharge direction, and the paper discharge tray 4 is provided at the front end of the apparatus main body 2. Two types of reading are possible, that is, reading by feeding the original 5 and reading by placing the original 5 on the apparatus main body 2. FIG. 2 is a sectional view of the image reading device 1 shown in FIG. As shown in this figure, the main body 2 of the image reading apparatus 1 is provided with a document glass 6 on its upper surface. Further, inside the apparatus main body 2, a guide shaft (not shown) directed in the conveying direction of the document 5 (left and right direction in FIG. 2) and a guide rail (not shown) are parallel to the document glass 6. The two carriages are movably supported by the guide shaft and the guide rail. At this time, the light source 7 directed to the reading position A on the original glass 6 and the first mirror 8 are provided on one carriage.
And a second mirror 9 on the other carriage.
And a third mirror 10 are mounted. Also, the light source 7
(Not shown) has a replaceable configuration.
Further, a lens 11 that converges the reflected light to form an image and a photoelectric conversion element 12 that reads the image are attached to a position facing the reflecting surface of the third mirror 10. Further, the automatic paper feeding device 3 constituting the image reading device 1 is provided with a paper feeding roller 14 along the original document mounting surface 13, and from the upper surface of the original document mounting surface 13 of the apparatus main body 2. A conveyance path 15 reaching the sheet ejection tray 4 through the reading position A on the original glass 6 is provided, and the conveyance path 15 is provided with a pair of upper and lower separation rollers 16 and a feed roller 17. A transport roller 18 is provided in the front in the transport direction. Further, a conveyance roller 19 is provided on the front side of the reading position A,
A transport roller pair 20 and a paper discharge roller pair 21 are provided in front of the reading position A in the transport direction.

FIG. 3 is an enlarged view of the vicinity of the reading position A in FIG. As shown in this figure, in the vicinity of the reading position A of the apparatus main body 2, a sheet-like member (density reference plate) 22 is attached to the upper surface of the original glass 6, and the density reference plate 2
A pressing plate 24 composed of a sheet-shaped black member 23 that covers the upper side of the sheet 2 is provided, and a sensor 6 that detects whether or not the document 5 is in the conveyance path 15 is provided in front of the conveyance roller 19.
1 is provided. FIG. 4 is a block diagram showing an outline of a circuit configuration example of the image reading apparatus 1 shown in FIG. As shown in this figure, in the image reading apparatus 1, a document is read from the host computer via the interface 25 through the CP.
This is done by sending a command to U26. When the manuscript 5 is read using the automatic paper feeder 3, when a necessary command is sent from the host computer through the interface 25, the CP
U26 uses the RAM 34 as a work area based on the status of each part of the device output from the various sensor processing units 31 and the data stored in the ROM 27,
Data processing is performed, a signal is sent to the motor drive circuit 28 to drive the motor 29, and the light source lighting device 3
A signal is also sent to 0 to turn on the light source 7.

Then, the originals 5 are fed one by one to the conveying path 15 by the feeding roller 14, the separating roller 16 and the feeding roller 17 which are driven by the motor 29, and after passing the reading position A, they are conveyed by the conveying roller 19 and conveyed. The document 5 after being read by the roller pair 20 and the paper discharge roller 21 is discharged onto the paper discharge tray 4. During this time, at the reading position A,
The image reading unit 33 reads the image information on the document 5 which is being conveyed, and the image processing unit 32 processes the image information obtained by this reading operation. That is, the light from the light source 7 is emitted to the original 5 on the original glass 6 at the reading position A, and the reflected light is sequentially reflected by the first mirror 8, the second mirror 9, and the third mirror 10 and is reflected by the lens 11. An image is formed on the photoelectric conversion element 12, and the image information on the original 5 is read. When the original 5 is read without using the automatic paper feeding device 3, the automatic paper feeding device 3 is rotated upward about the spindle to place the original 5 on the original glass 6. , Light source 7 and first mirror 8
An image is read by moving a carriage on which is mounted and a carriage on which the second mirror 9 and the third mirror 10 are mounted in a direction parallel to the document surface.

FIG. 5 is a block diagram schematically showing a circuit centering on the image reading section 33 in FIG. As shown in this figure, in the image reading unit 33, the light emitted from the light source 7 is reflected on the density reference plate 22 or the original 5 and the first light is reflected.
The light enters the photoelectric conversion element 12 via the mirror 8, the second mirror 9, the third mirror 10 and the lens 11. The image information stored in the photoelectric conversion element 12 is converted into an analog signal for each even pixel and odd pixel and output. Then, the analog signal is input to the sample hold units 35 and 36 for each even-numbered pixel and odd-numbered pixel, sample-held, and then combined by the multiplex unit 37. The combined analog electric signal is amplified by the amplifying unit 38 and then amplified by the reference voltage (Vre) output from the reference voltage generating unit 39 controlled by the CPU 26.
Based on f), it is converted into a digital signal by the A / D converter 40 and output to the image processing unit 32. As is well known, the digitized read data of the density reference plate 22 is stored in a FIFO memory and is used as reference data when performing shading correction on image data obtained by reading an original.

FIG. 6 is a block diagram schematically showing a switching regulator for supplying power to the electrical system of the image reading apparatus 1 shown in FIG. As shown in this figure, in the switching regulator 41, the AC voltage supplied from the commercial power source 42 is converted into a DC voltage via the rectifying bridge 43 and the smoothing capacitor 44. This DC voltage is
The control IC 45 turns on / off the switching element 46 formed of an FET to convert it into a high-frequency AC pulse, and the transformer 47 converts the power. The transformer 47 is composed of a plurality of windings in order to generate a DC voltage necessary for operating the image reading apparatus 1. Then, the AC pulse whose power is converted by the transformer 47 is converted into a predetermined DC voltage through the secondary side rectifying / smoothing circuit 48, and is supplied to each unit of the image reading apparatus 1. In the secondary side circuit of the power supply, the voltage fluctuation of the output voltage is detected by the detection unit 49, and the result of comparison with the reference voltage is fed back to the primary side by the coupling element 50 such as a photocoupler to control the IC 45. Thus, the duty (on / off ratio) of the switching element 46 is changed to stabilize the output voltage.

Further, as shown in FIG. 6, in the switching regulator 41, the power supply unit for supplying the light source 7 is arranged independently. That is, the commercial power source 42
Is converted into a DC voltage via a rectifying bridge 51 and a smoothing capacitor 52 arranged in parallel with the rectifying bridge 43. This DC voltage is converted into an AC pulse by turning on / off the switching element 54 by the control IC 53, and is supplied to the transformer 55. Transformer 55
Converts the supplied AC pulse into electric power according to the winding ratio. The power-converted pulse is converted into a DC voltage via the secondary side rectifying / smoothing circuit 56, and the light source lighting control circuit 5
It is supplied to the motor drive circuit 28 and the like as an input voltage of 7 and a power source for driving the drive components such as the motor 29.

When the user operates the host computer to set the reading operation mode of the document 5 through the interface 25, the CPU 26 of the image reading apparatus 1 is operated.
Sends necessary data to the control IC 53 according to the reading operation mode, and the control IC 53 changes the ON / OFF duty of the switching element 54 according to this data. At this time, the data sent by the CPU 26 to the control IC 53 is the same even if the power supply voltage of the light source 7 fluctuates due to the driving of the device when the reading operation is executed in each reading operation mode that the image reading device 1 can execute. Is controlled according to the operation of the device so that the light intensity can be maintained at an appropriate level.
C53 is predetermined data necessary for changing the duty of the switching element 54, and this is R
It is stored in the OM 27.

This data is obtained at a reading speed equivalent to 400 dpi (dots per inch), for example, on the density reference plate 2
When the power supply voltage of the light source 7 at the time of performing the reading operation of No. 2 is used as the reference (in the present embodiment, the density reference plate 22
Is assumed to be always read at a reading speed equivalent to 400 dpi), the original 5 is read in the reading operation mode set by the user, and at this time, the light source lighting control circuit 57. If the power source voltage of the light source 7 input to the voltage becomes higher than the reference voltage, the off time in one cycle of the switching cycle is lengthened,
This is data for driving the control IC 53 so as to shorten the ON time. If the data input to the control IC 53 is an analog amount, the D / A converter 58 is arranged on the input side of the control IC 53 as shown in FIG.
Data sent from the ROM 27 by the CPU 26
The D / A converter 58 performs D / A conversion, and the detection unit 5
9, it is configured to be supplied to the input side of the control IC 53 via a coupling element 60 such as a photo coupler.

FIG. 7 is a timing chart showing the outline of the waveform output by the control IC 53 in order to drive the above-mentioned switching element 54. As shown in this figure, the interval of the ON time T _ON and the OFF time T _{OFF in} the cycle T (T _ON + T _OFF ) is controlled to correct the power supply voltage fluctuation when driving the load components of the drive system. The processing flow at the time of reading the density reference and reading the original will be described below. <First Step> First, when the CPU 26 receives a document reading command from the user via the interface 25,
The ROM 27 is accessed and the data (data indicating the value D1) corresponding to the original reading command is transferred to the D / A converter 5.
Set to 8. In this case, the range that value D1 can take is
If the D / A converter 58 used has a resolution of 8 bits, it is 0 to 255. Also, this value D
The value 1 is a reference value for the fluctuation of the power source voltage of the light source 7, and is always a constant value. <Second Step> Then, the D / A converter 58 D / A converts the value D1 and outputs the output value D2 to the control IC 53.
Send. The control IC 53 applies a pulse signal corresponding to the value D2 to the switching element 54 in order to change the duty of the switching element 54 based on the value D2.

<Third Step> After that, the image reading apparatus 1
Starts reading the density reference plate 22 prior to reading the document 5. The reading of the density reference plate 22 is
Regardless of the reading operation mode at the time of reading the original set by the user, the operation is always performed in a constant manner. <Fourth Step> Then, the read data of the density reference plate 22 obtained by this reading operation is A / D converted by the A / D converter 40 based on a predetermined reference voltage, and is used as the density reference data in the FIFO memory. Stored in. <Fifth Step> Thereafter, the CPU 26 stores in the ROM 27 the data concerning the power supply voltage control of the light source 7 corresponding to the reading operation mode set by the user via the interface 25.
And outputs this data to the D / A converter 58. The D / A converter 58 D / A converts this data and sends it to the control IC 53. The control IC 53 controls the duty of the switching element 54 based on the data D / A converted by the D / A converter 58.
The pulse signal is sent to the switching element 54.

<Sixth Step> As a result, the light source lighting control circuit 57 lights the light source 7 by the input voltage of the light source 7 obtained by the switching element 54 described above. At the same time, the CPU 26 causes the motor drive circuit 2 to start the reading operation of the document 5 via the interface 25 in accordance with the reading operation mode set by the user.
8 is sent to drive the motor 29 to perform the reading operation. <Seventh Step> At this time, during the document reading operation, the CPU 2
Light source 7 turned on by the power supply voltage controlled by 6
The original document 5 to be read is illuminated by, and the reflected light or transmitted light is converted by the photoelectric conversion element 12.
It is converted into an analog electric signal. The analog electric signal passes through the sample hold units 35 and 36 and the multiplexer unit 37, is amplified by the amplification unit 38 with a predetermined amplification degree, and is A / D converted by the A / D converter 40.
The image information converted into a digital signal by the A / D converter 40 is subjected to processing such as shading correction based on the density reference data stored in advance in the FIFO or the like.

<Eighth Step> After that, the image data after the shading correction is stored in the ROM 27 by γ.
According to the correction characteristic pattern, γ correction is performed, and the image is passed to the image processing unit 32 in the next stage, where various image processing such as scaling processing and MTF correction is performed.

As described above, in this embodiment, the light amount correction data corresponding to the reading operation mode that can be set by the user is prepared and set based on the reading operation when reading the density reference plate 22. Since the correction data corresponding to the read operation mode is used to correct the light amount variation due to the drive of the apparatus, it is possible to correct the light amount variation due to the load condition in each reading operation mode,
As a result, an image with stable quality can be obtained.
Furthermore, in this embodiment, the light amount correction data is controlled by the CPU 26 via the D / A converter 58, so that the data corresponding to the resolution of the D / A converter 58 to be used,
You can make detailed corrections. In the present embodiment, the photoelectric conversion element 12 is assumed to be a 2-channel output type, but the photoelectric conversion element 12 is a 1-channel output type photoelectric conversion element. In this case, the sample hold units 35, 3
The number 6 may be one, and the multiplexer unit 37 is unnecessary.
Further, in this example of the embodiment, the data regarding the correction of the light source 7 (the value D2 in the above-described processing flow) set by the CPU 26 for the control IC 53 with respect to the reading operation mode set by the user via the interface 25 is: Although it is constant in the sub-scanning direction, considering the fluctuation of the light amount in one scanning, necessary data is prepared so that the correction data changes in time series within one scanning, and the D / A converter 58 is sequentially provided. You may make it comprise the firmware set to.

[0021]

As described above, according to the present invention, in the image reading apparatus having the constitution in which the power source of the light source is shared with other driving parts in the apparatus, the driving state of the apparatus is It is possible to always obtain a stable quality image even when operating in the reading operation mode that can be set by the user, by correcting the fluctuation of the light amount generated by.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one example of an image reading apparatus according to the present invention.

FIG. 2 is a sectional view of the image reading apparatus shown in FIG.

3 is an enlarged view of the vicinity of a reading position A in FIG.

FIG. 4 is a block diagram showing an outline of a circuit configuration example of the image reading apparatus shown in FIG.

5 is a block diagram schematically showing a circuit centering on the image reading unit in FIG.

6 is a block diagram schematically showing a switching regulator that supplies power to an electrical system of the image reading apparatus shown in FIG.

FIG. 7 is a timing chart showing an outline of waveforms output from a control IC for driving the switching element shown in FIG.

[Explanation of symbols]

1 image reading device, 2 device body, 3 automatic paper feeder,
4 output tray, 5 originals, 6 original glass, 7 light source,
8 first mirror, 9 second mirror, 10 third mirror,
11 lens, 12 photoelectric conversion element, 13 document mounting surface, 14 paper feed roller, 15 transport path, 16 separation roller,
17 feed rollers, 18 transport rollers, 19 transport rollers, 20 transport roller pairs, 21 paper discharge roller pairs, 22
Concentration reference plate, 23 Black member, 24 Holding plate, 25
Interface (User Interface), 26 CP
U (correction data reading unit, power supply unit control unit), 2
7 ROM (memory), 28 motor drive circuit, 29 motor, 30 light source lighting device, 31 various sensor processing units, 32 image processing unit, 33 image reading unit, 34 RA
M, 35, 36 Sample-and-hold section, 37 Multiplex section, 38 Amplifying section, 39 Reference voltage generating section, 40
A / D converter, 41 switching regulator, 42 commercial power supply, 43 rectifying bridge (power supply unit), 44 smoothing capacitor (power supply unit), 45
Control IC (power supply unit), 46 switching element (power supply unit), 47 transformer (power supply unit),
48 Secondary side rectifying / smoothing circuit (power supply unit), 49
Detector (power supply unit), 50 coupling element (power supply unit), 51 rectifying bridge (power supply unit),
52 smoothing capacitor (power supply unit), 53 control IC
(Power supply unit), 54 switching element (power supply unit), 55 transformer (power supply unit), 56 secondary side rectification / smoothing circuit (power supply unit), 57 light source lighting control circuit, 58 D / A converter, 59 detection unit (power supply) Unit), 60 coupling element (power supply unit), 61 sensor

Claims (2)

[Claims] 1. A reading operation mode designated via a user interface is operated to emit light from a light source to illuminate a document to be read while reflecting or transmitting the reflected light with a photoelectric conversion element. In the image reading apparatus that converts the image information on the original document as an electric signal, a memory in which correction data corresponding to each reading operation mode is registered, and a reading operation mode is specified via the user interface. Of the correction data registered in the memory, a correction data reading unit that reads the correction data corresponding to the reading operation mode designated through the user interface, and a correction data reading unit that reads the correction data Based on the correction data, the power supply unit is controlled to adjust the value of the power supply voltage applied to the light source, An image reading apparatus comprising: a power supply unit control unit that corrects a light amount variation of a light source. 2. The image reading apparatus according to claim 1, wherein a power supply unit that supplies a power supply voltage to a light source that illuminates a document to be read and a power supply unit that supplies a power supply voltage to components of a drive system are independent of each other. And an image reading apparatus that controls the value of the power supply voltage output from each of the power supply units according to the reading operation mode specified via the user interface.