JP2007180774A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus which can provide a satisfactory read image by correcting a drop of light quantity due to the shading characteristic of a lens without increasing a scale of an illumination unit. <P>SOLUTION: In the image reading apparatus provided with lamp units 203, 210 each of which is composed of light emitting element string obtained by arraying a plurality of LEDs 401 in a straight line, a lighting control device 405 turns on/off each of the LEDs 401 in a short period of time, so that the lighting time of LEDs 401a, 401b, 401c, LEDs 401h, 401i, 401j arrayed on both the end parts E of the light emitting element string is made longer than the lighting time of LEDs 401d, 401e, 401f, 401g arrayed on the center part C of the light emitting element string. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus including a line-shaped illumination device, an image forming apparatus including the image reading apparatus, and the like.

  2. Description of the Related Art Conventionally, an original reading apparatus has been provided with an illuminating device that illuminates an original for each reading line. In this illuminating device, a light emitting element array in which light emitting elements such as a plurality of LEDs (light emitting diodes) are arranged in a straight line. Some of them use (hereinafter referred to as LED array).

  The LED arrays are arranged so that the LEDs are equally spaced, and are arranged so that each LED is constant with respect to the paper surface of the document to be read. On the other hand, the reading lens that guides the reflected light from the document to the image sensor has a shading characteristic in which the amount of light at the peripheral portion is lower than the optical axis portion. For this reason, when the original is illuminated with the LED array as described above, there arises a problem that the output of the image sensor is reduced in the vicinity of both ends of the reading line.

For this reason, conventionally, in order to make the light quantity at both ends of the LED array larger than that at the center, it is known to increase the light emission voltage of the LEDs at both ends (see, for example, Patent Document 1).
US Pat. No. 5,767,796

  However, the prior art has the following problems.

  When the conventional technology is used, it is necessary to have a plurality of power sources in order to change the light emission voltage of the LED between the central portion and both end portions, and the scale as a lighting device increases.

  The present invention has been made in view of the above-described points, and increases the amount of light at both ends of the LED array without increasing the scale of the lighting device, corrects the light amount drop at both ends due to lens characteristics, and provides a good read image. An object of the present invention is to provide an image reading apparatus capable of obtaining the above.

  In this image reading device, a light source in which a plurality of light emitting elements such as LEDs are arranged in an array is driven to blink at a constant short cycle, and the lighting times of the LEDs arranged at both ends of the LED array are arranged in the central portion. It can be provided by making it longer than the lighting time of the LED.

  In order to achieve the above object, the present invention comprises the following arrangement.

  (1) Illuminating means comprising a light emitting element array in which a plurality of light emitting elements are arranged in a straight line, a lens for condensing the reflected light of the original irradiated by the illuminating means, and the light condensed by the lens In the image reading apparatus having a photoelectric conversion element for reading the image information as image information and a lighting control means for driving the light emitting element row, the lighting control means drives the light emitting element row to blink at a constant cycle. The plurality of light emitting elements arranged at the center of the light emitting element array and the plurality of light emitting elements arranged at both ends of the light emitting element array are controlled with different lighting times. Reader.

  (2) The lighting control means is configured such that the lighting times of the plurality of light emitting elements arranged at both ends of the light emitting element row are longer than the lighting times of the plurality of light emitting elements arranged at the central portion of the light emitting element row. The image reading apparatus according to (1), wherein the image reading apparatus is lengthened.

  (3) An illuminating unit composed of a light emitting element array in which a plurality of light emitting elements are arranged in a straight line, a lens for condensing the reflected light of the original irradiated by the illuminating unit, and the light collected by the lens In the image reading apparatus having a photoelectric conversion element for reading the image information as image information and a lighting control means for driving the light emitting element row, the lighting control means drives the light emitting element row to blink at a constant cycle. An image reading apparatus that controls the lighting time of each of the light emitting elements arranged from the central portion toward both ends of the light emitting element row so as to gradually change.

  (4) The lighting control means controls the lighting time of each of the light emitting elements arranged from the central portion toward both ends of the light emitting element row so as to be sequentially increased. ) Image reading apparatus.

  According to the present invention, it is possible to increase the amount of light at both ends of the illuminating unit without increasing the scale of the illumination device, and to correct the drop in the amount of light at both ends due to lens characteristics, thereby obtaining a good read image. Become. This is because, in an image reading apparatus having an illuminating unit in which a plurality of light emitting elements are arranged in a straight line, each light emitting element is driven to blink at a constant short period, and the light emitting elements disposed at both ends of the illuminating unit are turned on. It is obtained by making the time longer than the lighting time of the light emitting element in the center.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  One embodiment of the present invention will be described below.

  FIG. 1 is a schematic sectional view of an image reading apparatus according to the present invention.

  In FIG. 1, an ADF 100 that is an automatic document feeder is fed from a document stack S set on a document tray 20 with its surface facing upward by a pickup roller 1 from a top document to a separation unit 2. The separation unit 2 is provided with a separation roller on the upper side and a separation pad on the lower side, and performs separation one by one from the uppermost sheet of the document bundle S.

  When reading an image on the front side with a single-sided original, the conveyance is performed as follows. First, the separated document is subjected to skew correction during separation and conveyance by the first registration roller 3. Thereafter, the image is conveyed from the first registration roller 3 by the second registration roller 4 and the first conveyance roller 5, and the image on the surface is read while being conveyed by the reading roller 7 at the reading position R. Then, the document is sequentially discharged from the second transport roller 6 by the paper discharge roller 8 onto the paper discharge tray 21 with the document surface facing downward.

  When reading both front and back images with a double-sided document, the conveyance is performed as follows. First, the separated document is subjected to skew correction during separation and conveyance by the first registration roller 3. Thereafter, the sheet is conveyed from the second registration roller 4 by the first conveyance roller 5 and the second conveyance roller 6, and the image on the surface is read while being conveyed by the reading roller 7 at the reading position R. Then, the document conveying edge is temporarily conveyed from the second conveying roller 6 to the sheet discharging tray 8 by the sheet discharging roller 8, and the conveyance is stopped in a state where the reading rear end side is nipped by the sheet discharging roller 8.

  Thereafter, the document is switched back and conveyed, and the skew correction is performed again by the second registration roller 4. Then, the original is conveyed by the first conveyance roller 5 and the second conveyance roller 6, and again conveyed by the reading roller 7 at the reading position R. The image on the back side is read while it is being performed.

  However, if the document is discharged from the second transport roller 6 to the discharge tray 21 with the discharge roller 8 facing upward, the surface order set on the document tray 20 will be different. Therefore, the document whose back side has been read is conveyed again on the sheet discharge tray 21 by the second conveying roller 6 and the sheet discharge roller 8, and the rear end side of the reading is nipped by the sheet discharge roller 8. The transportation is stopped. After that, the document is switched back and conveyed by the second registration roller 4, the first conveyance roller 5, and the second conveyance roller 6, and then in order by the sheet discharge roller 8 with the surface facing down on the sheet discharge tray 21. To be discharged. However, even during the conveyance by the reading roller 7 at the reading position R, the document image is not read during this period.

  The reader unit 200 optically reads image information recorded on a document, photoelectrically converts it, and inputs it as image data. The reader unit 200 includes an ADF original platen glass 201 (hereinafter referred to as ADF platen) and a book original platen glass 202 (hereinafter referred to as book platen). The scanner unit 209 includes a lamp unit 203 and 210 (corresponding to illumination means), a mirror 204, mirrors 205 and 206, a lens 207, a CCD sensor 208 (corresponding to a photoelectric conversion element), and the like.

  When reading a document image conveyed from the ADF 100, the reader unit 200 moves the scanner unit 209 below the ADF platen 201 and stops it, and the document is conveyed on the reading position R by the reading roller 7. While reading the image information.

  When reading an image of a document placed on the book platen 202, the scanner unit 209 is moved in the sub-scanning direction from a document set reference (not shown) to read the image information of the document (pressure plate mode scan).

  For reading image information, the lamp units 203 and 210 are turned on to irradiate the original. Reflected light from the document is input to the CCD sensor 208 via mirrors 204, 205, 206 and a lens 207. Then, the reflected light from the document input to the CCD sensor 208 is subjected to electrical processing such as photoelectric conversion, and is subjected to normal digital processing.

  The present invention is also applicable as an image reading apparatus in which the reader unit 200 and the automatic document feeder 100 are integrated.

  FIG. 2 is a control block diagram of the ADF 100 of the image reading apparatus according to the present invention. The ADF 100 includes a control unit (hereinafter referred to as CPU) 800, a read only memory (hereinafter referred to as ROM) 801, and a random access memory (hereinafter referred to as RAM) 802, which are central processing units. In addition, an output port and an input port described later are provided. The ROM 801 stores a control program, and the RAM 802 stores input data and work data. In addition, a separation motor M1, a paper feed motor M2, a paper discharge motor M3, a separation solenoid SL, and a paper feed clutch CL are connected to the output port. A post-separation sensor 10, a registration sensor 11, a lead sensor 12, a paper discharge sensor 13, a document detection sensor 14, a document length detection sensor 15, and a document width detection sensor 810 (not shown in FIG. 1) are connected to the input port. ing.

  The CPU 800 controls the separation motor M1, the paper feed motor M2, the paper discharge motor M3, the separation solenoid SL, and the paper feed clutch CL in accordance with a control program stored in the ROM 801. The CPU 800 performs serial communication with a central processing unit (CPU 900) (see FIG. 3) of the reader unit 200, and exchanges control data with the reader unit 200.

  Note that when the present invention is also applied as an image reading apparatus in which the reader unit 200 and the ADF 100 are integrated, it may be configured by one CPU without performing communication.

  FIG. 3 is a functional block diagram of the reader unit 200 of the image reading apparatus according to the present invention. Reference numeral 301 denotes a document illuminating unit composed of lamp units 203 and 210, 302 an optical system moving unit for moving the scanner unit 209, and 303 an image reading unit composed of a CCD sensor 208. Reference numeral 304 denotes an image processing unit that performs correction of analog signals from the image reading unit 303, A / D conversion, and the like. Reference numeral 305 denotes an illumination control unit that performs lighting control of the lamp units 203 and 210 included in the document illumination unit 301. Equivalent to control means). Further, the reader unit 200 is divided into functions such as a CPU 900, a ROM 901, and a RAM 902, and each is optimally controlled by the CPU 900. Further, the lamp units 203 and 210 included in the document illumination unit 301 may be controlled directly by the CPU 900 without configuring the illumination control unit 305.

  FIG. 4 is an external perspective view of the lamp units 203 and 210 of the leader unit. The lamp units 203 and 210 constitute a light-emitting element array in which LEDs 401 (corresponding to light-emitting elements) are arranged in a line at equal intervals, and the light from the LED 401 is reflected and diffused by the reflectors 402 and 403 to be reflected on the document surface. Irradiate. In this figure, the LED 401 represents an LED chip, but a discrete type LED may be used. Further, in order to obtain an image reading apparatus capable of reading a color original, it is desirable to use a white LED as the LED 401.

  FIG. 5 is a control block diagram of the lamp units 203 and 210 of the leader unit. The lighting control device 405 serving as the illumination control unit 305 performs blinking driving of the LED 401 at a constant short period in accordance with a command from the CPU 900. By performing blinking driving at a constant short cycle, it is possible to achieve power saving and increase the life of the LED 401 while maintaining the same amount of light as that during continuous lighting. Further, when the blinking driving cycle is delayed, it can be realized by synchronizing with the reading cycle of the CCD sensor 208.

  The lighting control device 405 includes an LED 401a, b, c, LED 401h, i, j at both ends E (hereinafter simply referred to as both ends E) of the light emitting element row, and a central portion C (hereinafter simply referred to as the center portion) of the light emitting element row. C)) 401d, e, f, and g can be controlled separately. The LEDs 401d, e, f, and g at the center C are driven to blink by a driving pulse P, and the LEDs 401a, b, c, and LEDs 401h, i, and j at both ends E are driven to blink by a driving pulse Q. At this time, control is performed such that the lighting time per cycle of the drive pulse Q is longer than the drive pulse P. The drive pulse waveform of the LED 401 at that time is shown in FIG.

  FIG. 6 is an internal block diagram of the lighting control device 405. The CPU 900 accesses the registers 501 and 502 and sets a pulse pattern for driving the LED 401. Counters 504 and 505 having a built-in flip-flop function output drive patterns according to the settings of the registers 501 and 502 in synchronization with the clock from the clock generator 503. The AND gates 506 and 507 output drive patterns from the counters 504 and 505 while the output permission signal from the CPU 900 is input. Drivers 508 and 509 drive the LED 401 in accordance with outputs from the AND gates 506 and 507.

  As a result, as shown in FIG. 8, an illuminance distribution is obtained such that the amount of light at both ends E of the lamp units 203 and 210 is large.

  On the other hand, as shown in FIG. 9, the lens 207 that condenses the reflected light from the document onto the CCD sensor 208 has a characteristic that the amount of transmitted light is large in the central part and small in the peripheral part due to shading characteristics.

  Therefore, since the reflected light of the illuminance distribution shown in FIG. 8 and the combined light of the shading characteristics shown in FIG. 9 are incident on the CCD sensor 208, the light receiving surface of the CCD sensor 208 is corrected almost uniformly. Light of illuminance distribution will arrive. For this reason, the problem that the sensor output at the end of the CCD sensor 208 decreases does not occur.

  In addition, according to the present embodiment, it is not necessary to have a plurality of power sources, and the scale of the lighting device can be reduced compared to the configuration realized by increasing the light emitting element driving voltage at both ends in the line-shaped light emitting element row. It doesn't get bigger.

  As another embodiment of the present invention, a control block diagram is shown in FIG. In FIG. 10, the same components as those in FIG. As shown in FIG. 10, the lighting control device 405 may be configured to individually control lighting of the respective LEDs 401 constituting the lamp units 203 and 210. In this case, the lighting time of the LEDs 401 arranged from the central portion C toward both end portions E is controlled so as to become longer sequentially. This makes it possible to create a finer illuminance distribution.

  As described above, in the present invention, each LED constituting the light emitting element array is driven to blink at a constant short cycle, and the lighting time of the LEDs arranged at both ends is set to the lighting time of the LEDs arranged at the center portion. Longer than that. As a result, it is possible to increase the amount of light at both ends of the illuminating means without correcting the scale of the illumination device, and to correct the drop in the amount of light at the ends due to lens characteristics, thereby obtaining a good read image.

Schematic sectional view of an image reading apparatus according to the present invention Control block diagram of ADF of image reading apparatus in the present invention Functional block diagram of the reader unit of the image reading apparatus in the present invention The external perspective view of the lamp unit of the leader part in this invention Control block diagram of the lamp unit of the leader unit in the present invention Internal block diagram of lighting control device in the present invention The figure which shows the drive pulse waveform of LED in this invention Illuminance distribution diagram of lamp unit of leader unit in the present invention Optical characteristics diagram showing lens shading characteristics The control block diagram of the lamp unit of the leader part in the other Example of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pickup roller 2 Separation part 3 1st registration roller 4 2nd registration roller 5 1st conveyance roller 6 2nd conveyance roller 7 Reading roller 8 Paper discharge roller 10 Separation sensor 11 Registration sensor 12 Lead sensor 13 Paper discharge sensor 14 Document detection Sensor 15 Document length detection sensor 20 Document tray 21 Paper discharge tray 100 Automatic document feeder (ADF)
200 Reader unit 201 ADF original platen glass 202 Book original platen glass 203, 210 Lamp unit (corresponding to illumination means)
204, 205, 206 Mirror 207 Lens 208 CCD sensor (equivalent to photoelectric conversion element)
209 Scanner unit 301 Document illumination means 302 Optical system moving means 303 Image reading means 304 Image processing means 305 Illumination control means (corresponding to lighting control means)
401 LED (equivalent to light emitting element)
402, 403 Reflector 405 Lighting control device (corresponding to lighting control means)
900 CPU
901 ROM
902 RAM
R Reading position

Claims (4)

An illumination means comprising a light emitting element array in which a plurality of light emitting elements are arranged in a straight line;
A lens for condensing the reflected light of the original illuminated by the illumination means;
A photoelectric conversion element for reading the light collected by the lens as image information;
In an image reading apparatus having a lighting control means for driving the light emitting element row,
The lighting control means drives the light emitting element row to blink at a constant cycle,
Image reading, wherein the plurality of light emitting elements arranged at a central portion of the light emitting element array and the plurality of light emitting elements arranged at both ends of the light emitting element array are controlled with different lighting times. apparatus. The lighting control means includes
The lighting time of the plurality of light emitting elements arranged at both ends of the light emitting element row is made longer than the lighting time of the plurality of light emitting elements arranged in the central portion of the light emitting element row. Item 2. The image reading apparatus according to Item 1. An illumination means comprising a light emitting element array in which a plurality of light emitting elements are arranged in a straight line;
A lens for condensing the reflected light of the original illuminated by the illumination means;
A photoelectric conversion element for reading the light collected by the lens as image information;
In an image reading apparatus having a lighting control means for driving the light emitting element row,
The lighting control means drives the light emitting element row to blink at a constant cycle,
An image reading apparatus, wherein the lighting time of each of the light emitting elements arranged from the center of the light emitting element array toward both ends is controlled to gradually change. The lighting control means includes
4. The image reading apparatus according to claim 3, wherein the lighting time of each of the light emitting elements arranged from the central part to both ends of the light emitting element row is controlled so as to be sequentially increased.

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