JP2009088857A - Image scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image scanner for preventing a read image on a first surface of a document from deteriorating in quality in duplex scanning. <P>SOLUTION: In a scan mode using an automatic document feeder 35 for scanning, the document conveying speed in duplex scanning is set lower than in single-sided scanning. Accordingly, the quantity of light emission of an LED array 21 in the duplex scanning is reduced more than in the single-sided scanning. For example, the number of turned-on LEDs in an LED array 21, a voltage applied to the LEDs, or the lighting Duty of the LEDs in the duplex scanning is reduced more than in the single-sided scanning. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus capable of simultaneously reading both sides of a document conveyed by an automatic document feeder.

As an image reading apparatus for reading both sides of a document, as disclosed in Patent Document 1, a first surface is a charge coupled device (CCD) and a second surface is a contact image sensor (CIS: Contact). Some of them are read by Image Sensor. Usually, a cold cathode tube is used as the light source of the CCD, and an LED array is often used as the light source of the CIS. Since the LED array has a luminance lower than that of the cold cathode fluorescent lamp, the reading time for one line of the original is longer, and when performing double-sided reading, the original is conveyed in accordance with the reading speed of the CIS.
Japanese Patent Laid-Open No. 9-46484

  By the way, since the brightness of the LED array has been improved in recent years, even when the LED array is used as a light source of a reading unit on the first surface constituted by a CCD or the like, reading can be performed at high speed. However, since the reading unit on the second side of the document is required to have a compact configuration, the luminance of the LED array provided in the reading unit on the second side constituted by CIS or the like cannot be increased so much due to the limitation of the amount of heat dissipation. . For this reason, at the time of double-sided reading, it is the current situation that the document conveyance speed must be matched with the reading speed of the reading unit on the second side. In this case, the light amount of the light source may be exceeded on the first surface side, the CCD used in the reading unit on the first surface may be saturated in terms of light amount, causing blooming or the like, and image quality may deteriorate.

  Therefore, a problem to be solved by the present invention is to provide an image reading apparatus capable of preventing deterioration in image quality of a read image on the first side of a document during double-sided reading.

  In order to solve the above-described problems, the present invention includes first and second reading units that respectively read the first and second surfaces of a document conveyed on a predetermined conveyance path, and read only the first surface. In the image reading apparatus in which the conveyance speed of the document during single-side reading is higher than the conveyance speed during double-side reading for reading the first surface and the second surface, illumination is performed on the first surface of the document. A first light source; a second light source that illuminates the second surface of the document; and a control unit that controls the first and second light sources. The first light source includes an LED array. Then, the control unit reduces the light amount of the first light source at the time of the double-sided reading than the light amount at the time of the single-sided reading.

  Further, in the image reading apparatus, the control unit reduces the number of LEDs lit in the LED array constituting the first light source at the time of the double-side reading as compared with the case of the single-side reading.

  Further, in the image reading apparatus according to the present invention, the control unit lowers the voltage applied to the LED array constituting the first light source at the time of double-sided reading than at the time of single-sided reading.

  Further, in the image reading apparatus according to the present invention, the control unit lowers the lighting duty of the LED array constituting the first light source at the time of the double-sided reading from that at the time of the single-sided reading, and turns on the LED. / The off cycle is matched with the CCD line cycle.

  According to the present invention, the light amount of the first light source for the first surface of the document when reading both sides is made lower than the light amount when reading one side. Therefore, it is possible to prevent the amount of light on the first side of the document from being exceeded when reading both sides, and as a result, it is possible to prevent deterioration of the image quality of the read image on the first side when reading both sides.

  In addition, since the LED array is used as the first light source, the light quantity of the first light source can be easily adjusted.

  In addition, according to the present invention, the amount of light of the LED array can be easily reduced because the amount of light is reduced by reducing the number of LEDs lit in the LED array.

  In addition, according to the present invention, since the light amount is reduced by lowering the voltage applied to the LED array, the light amount of the LED array can be reduced using a simple circuit.

  In addition, according to the present invention, since the light amount is reduced by lowering the lighting duty of the LED array, the light amount of the LED array can be reduced while maintaining the light emission efficiency with respect to the power supplied to the LED array. In addition, since the on / off period of the LED is matched with the line period of the CCD, the amount of light for each line can be made uniform, and the image quality of reading can be maintained.

  FIG. 1 is a block diagram of a facsimile composite apparatus (hereinafter simply referred to as “composite apparatus”) as an image reading apparatus according to an embodiment of the present invention, and FIG. 2 schematically illustrates a configuration around a reading unit of the composite apparatus. FIG. The composite apparatus 1 is connected to a public switched telephone network (PSTN) 5 and is connected to other information terminals and the Internet via a LAN (Local Area Network) 6. The multifunction apparatus 1 has functions of a copy mode, a printer mode, and a facsimile mode, and also has a function of sending and receiving mail.

  As shown in FIG. 1, the multifunction device 1 includes an MPU (Micro Processing Unit) 11 as a control unit, a flash memory 12, a RAM (Random Access Memory) 13, a memory controller 14, an image memory 15, a codec 16, a modem 17, NCU (Network Control Unit) 18, operation panel 19, reading mechanism control circuit 20, LED arrays 21 and 22 as first and second light sources, CCDs 23 and 24 as first and second reading units, read image signals Processing circuits 25 and 26, a print image signal processing circuit 27, a printer 28, a LAN interface (I / F) 29, and the like are provided. These units are connected via a bus 30.

  The MPU 11 controls each part of the hardware of the composite apparatus 1 via the bus 30 and executes various programs based on the program stored in the flash memory 12. The flash memory 12 stores various programs and data necessary for the operation of the composite apparatus 1. The RAM 13 stores temporary data generated when the program is executed.

  The memory controller 14 controls writing and reading of image data with respect to the image memory 15. The image memory 15 is configured using SDRAM (Synchronous Dynamic Random Access Memory) or the like, and stores image data to be transmitted, received image data, and read image data. The codec 16 performs encoding and decoding according to a predetermined protocol. As processing of this codec 16, MH (Modified Huffman), MR (Modified READ), MMR (Modified Modified READ) method, TIFF (Tagged Image File Format) or JPEG (Joint Photographic Experts Group) method for image data of the read original Encoding and decoding of image data received by facsimile, e-mail or the like.

  The modem 17 is connected to the bus 30 and has a function for facsimile communication. Similarly, the modem 17 is connected to the NCU 18 connected to the bus 30. The NCU 18 is hardware for connecting to the public switched telephone network 5 and connects the modem 17 to the public switched telephone network 5 as necessary.

  The operation panel 19 receives an operation on the multifunction apparatus 1 and displays information necessary for the operation, and includes a display unit configured by a plurality of operation keys, a liquid crystal display device, and the like. The reading mechanism control circuit 20 controls the document placing table 31 (see FIG. 2) and the like. The document placing table 31 is provided on the upper surface of the multifunction device 1 and reads an image from the set document.

  Here, the configuration of the document table 31 will be described with reference to FIG. As shown in FIG. 2, the document table 31 includes a main body portion 33 including a flat bed scanner 32 and a cover body 34 that is opened and closed with respect to the upper surface of the main body portion 33. The cover body 34 includes an automatic document feeder 35 and a reading unit 36. The automatic document feeder 35 includes a document tray (not shown), a discharge tray (not shown), a conveyance path 37 for conveying a document, and a conveyance mechanism 38 including a conveyance roller for conveying the document. . The flat bed scanner 32 includes a reading unit 39, an LED array 21, and a driving mechanism (not shown). The reading unit 39 and the LED array 21 are moved in the sub-scanning direction by the drive mechanism in a first reading mode to be described later.

  The reading unit 39 of the flat bed scanner 32 includes a CCD 23, a lens system 391, and a plurality of mirrors 392. The light from the first surface of the document is reflected by the plurality of mirrors 392 and then enters the CCD 23 through the lens system 391, whereby the image on the first surface of the document is read by the CCD 23. The LED array 21 includes a plurality of LEDs arranged along the main scanning direction, and illuminates the first surface of the document.

  The reading unit 36 of the cover body 34 includes a CCD 24, a lens system 361, a plurality of mirrors 362, and the LED array 22. The light from the second surface of the document is reflected by the plurality of mirrors 362 and then enters the CCD 24 through the lens system 361, whereby the image on the second surface of the document is read by the CCD 24. The LED array 22 includes a plurality of LEDs arranged along the main scanning direction, and illuminates the second surface of the document. Since the LED array 22 is housed in a smaller area than the LED array 21 on the first surface side, the heat generation amount is severely limited, and the maximum output (maximum light emission amount) is kept lower than the LED array 21. It has been.

  In the document placing table 31, a first reading mode for reading a document while being set on the platen glass 40 of the flat bed scanner 32 and a second reading mode for reading using the automatic document feeder 35 are provided. Is provided. In the mode using the automatic document feeder 35, a single-sided reading mode for reading only the first side of the original and a double-sided reading mode for reading the first and second sides of the original in parallel are provided. ing.

  In the first reading mode, the document is set on the platen glass 40. Then, while the reading unit 39 and the LED array 21 are moved in the sub-scanning direction by the driving mechanism, illumination of the first surface of the document by the LED array 21 and reading of the first surface by the reading unit 39 are performed.

  In the single-sided reading mode of the second reading mode, the document set on the document tray is introduced into the conveyance path 37 by the conveyance mechanism 38, conveyed along the conveyance path 37, and then discharged to the discharge tray. The Reading in this case is performed when the document passes the first reading position 371 on the conveyance path 37, and the first surface of the document is read. The illumination of the document is performed by the LED array 21, and the reading is performed by the reading unit 39.

  In the double-sided reading mode of the second reading mode, the document set on the document tray is introduced into the conveyance path 37 by the conveyance mechanism 38, conveyed along the conveyance path 37, and then discharged to the discharge tray. The The reading in this case is performed when the document passes through the first reading position 371 and the second reading position 372 on the conveyance path 37. The first side of the original is read at the first reading position 371, and the second side of the original is read at the second reading position 372. Illumination of the first surface of the document is performed by the LED array 21, and reading is performed by the reading unit 39. Further, the reading unit 36 illuminates and reads the second surface of the document.

  The read image signal processing circuits 25 and 26 generate digital image data based on the image signals given from the CCDs 23 and 24, and execute various image processing such as shading correction. The image data generated by the read image signal processing circuits 25 and 26 is stored in the image memory 15 via the memory controller 14.

  The print image signal processing circuit 27 processes the print image signal and inputs it to the printer 27. The printer 27 is a printer apparatus such as an electrophotographic system, and prints received data, copy original data, and print data given from an external information terminal. The LAN interface is connected to the LAN 6, receives signals and data from the LAN 6 and the Internet, and transmits signals and data to the LAN 6 and the Internet.

  In the composite apparatus 1 configured in this way, the reading speed of the reading unit 36 that reads the second side of the document is the reading unit that reads the first side due to the limitation of the heat generation amount of the LED array 22 described above. It is set to be slower than the reading speed of 39. For this reason, in the second reading mode in which reading is performed using the automatic document feeder 35, the document conveyance speed at the time of duplex reading is set to be lower than the document conveyance speed at the time of single-sided reading. This is because both the reading units 36 and 39 are used at the time of double-sided reading, so that the reading speed of the reading unit 39 needs to be lowered in accordance with the reading speed of the reading unit 36.

  Corresponding to this, in the present embodiment, the light emission amount of the LED array 21 at the time of double-sided reading is lower than the light emission amount at the time of single-sided reading by control of the MPU 11. In this case, the amount of light emission suppression is set according to the ratio of the document conveyance speed (reading speed) during single-sided reading and double-sided reading.

  As a result, it is possible to prevent the amount of light on the first side of the document from being exceeded during double-sided reading, and as a result, it is possible to prevent deterioration in image quality of the read image on the first side of the document during double-sided reading.

  Further, since the LED array 21 is used as the first light source that illuminates the first surface of the document, the amount of light that illuminates the first surface can be easily adjusted.

  As a technique for reducing the light emission amount of the LED array 21, the following configuration may be mentioned. As a first configuration, there is a configuration in which the number of LEDs lit in the LED array 21 at the time of double-sided reading is reduced from that at the time of single-sided reading. For example, when the LED array 21 is provided with a plurality of LED rows arranged along the main scanning direction, all the LED rows are turned on when reading one side, and only some of the LED rows are turned on when reading both sides. May be.

  In the first configuration, the amount of light of the LED array can be easily reduced because the amount of light is reduced by reducing the number of LEDs lit in the LED array 21.

  As a second configuration, there is a configuration in which the voltage applied to the LED array 21 at the time of double-sided reading is lower than that at the time of single-sided reading. In the case of this second configuration, the light quantity of the LED array 21 can be reduced using a simple circuit.

  Further, as a third configuration, when the LED array 21 is driven by a PWM (Pulse-Width Modulation) method, there is a configuration in which the lighting duty of the LED array 21 is adjusted. In the PWM method, each LED in the LED array 21 is periodically turned on and off as shown in FIG. The amount of light emission per unit time of each LED can be adjusted by changing the ratio (lighting duty) of the on period 52 in the period (one cycle) 51 in which the on / off is performed once. Specifically, the lighting duty of the LED array 21 at the time of double-sided reading is lowered than that at the time of single-sided reading, and thereby the light emission amount of the LED array 21 at the time of double-sided reading is lowered than that at the time of single-sided reading. In the case of this third configuration, the light amount is reduced by lowering the lighting duty of the LED array 21, so that the light amount of the LED array 21 can be reduced while maintaining the light emission efficiency with respect to the power supplied to the LED array 21. Further, by matching the on / off period of the LED with the one-line reading period of the CCD, the light quantity for any line can be made equal.

  In the above-described embodiment, the reading units 36 and 39 are configured using the CCDs 23 and 24. However, either one or both of the reading units 36 and 39 are configured using a contact image sensor instead of the CCDs 23 and 24. May be.

1 is a block diagram of a facsimile composite apparatus as an image reading apparatus according to an embodiment of the present invention. FIG. 2 is a diagram schematically illustrating a configuration around a reading unit of the facsimile multifunction device of FIG. 1. It is explanatory drawing of the PWM drive of an LED array.

Explanation of symbols

1 Facsimile compound machine 21, 22 LED array 23, 24 CCD
31 Document Placement Table 32 Flat Bed Scanner 35 Automatic Document Feeder 37 Conveying Path 36 Reading Unit 38 Conveying Mechanism 39 Reading Unit 11 MPU

Claims (4)

The first and second reading sections that respectively read the first surface and the second surface of the document conveyed on a predetermined conveyance path are provided, and the conveyance speed of the document at the time of single-sided reading that reads only the first surface is In the image reading apparatus that is faster than the conveyance speed at the time of double-sided reading for reading the first surface and the second surface,
A first light source that illuminates the first surface of the document; a second light source that illuminates the second surface of the document; and a control unit that controls the first and second light sources. ,
The first light source is constituted by an LED array;
The image reading apparatus according to claim 1, wherein the control unit reduces a light amount of the first light source at the time of double-sided reading from a light amount at the time of single-sided reading. The image reading apparatus according to claim 1,
The image reading apparatus, wherein the control unit reduces the number of lighted LEDs in the LED array constituting the first light source at the time of double-sided reading than at the time of single-sided reading. The image reading apparatus according to claim 1,
The image reading apparatus, wherein the control unit lowers a voltage applied to the LED array constituting the first light source at the time of double-sided reading as compared to at the time of single-sided reading. The image reading apparatus according to claim 1,
The control unit lowers the lighting duty of the LED array constituting the first light source at the time of double-sided reading from that at the time of single-sided reading, and matches the LED on / off cycle with the CCD line cycle. An image reading apparatus.

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