JP2013229704A - Image reading device and image forming device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading device, capable of reading a manuscript image with high accuracy without affected by external light.SOLUTION: An image reading device 2 includes: a white color LED 24 for light illuminating a manuscript read surface; an imaging lens 29 for imaging reflection light from a manuscript; and a CCD (photoelectric conversion element) 30 for converting an optical image imaged by the imaging lens 29 into a potential signal. The image reading device 2 further includes a plurality of band pass filters 28 having different wavelength bands of external light, for intercepting transmission. By the selection of and switching to a band pass filter 28 producing least transmitting external light among the plurality of the band pass filters 28, the frequency bandwidth of the while color LED 24 is varied to prevent interception by the selected band pass filter 28.

Description

  The present invention relates to an image reading apparatus for optically reading a document image and an image forming apparatus including the image reading apparatus.

  An image forming apparatus such as a copying machine that forms an image on a sheet by an electrophotographic system is provided with an image reading apparatus for optically reading a document image. An LED for illumination, an imaging lens that forms an image of reflected light from the document, and a photoelectric conversion element that converts an optical image formed by the imaging lens into a potential signal are provided.

  Incidentally, in recent years, LEDs having high luminous efficiency are being used instead of conventional xenon lamps and cold cathode tube lamps as light sources of image reading apparatuses.

  Thus, when the platen is not completely closed, such as when reading a book document, or in an environment that is susceptible to external light such as fluorescent light or sunlight, the light is emitted from the LED and reflected from the document surface. Since external light is mixed in the reflected light, the original image may not be read accurately.

  Therefore, Patent Document 1 discloses a multi-layer filter that transmits 640 nm to 660 nm and blocks 580 nm to 610 nm of the mixed reflected light, transmits 640 nm to 660 nm, and reflects 400 nm to 590 nm. An image reading device (leather scanner) that uses a highly visible semiconductor laser with a wavelength of 650 nm to prevent deterioration of reading performance due to the influence of ambient light such as a fluorescent lamp by selecting a resin filter to be blocked. Proposed.

JP 11-338958 A

  In the configuration proposed in Patent Document 1, it is possible to block light having a peak wavelength of a three-wavelength fluorescent lamp by using a filter having a short transient range and a filter having a long transient range. It is a means for avoiding laser light. For this reason, interference with the peak wavelength of the three-wavelength fluorescent lamp can be avoided only in a certain region.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image reading apparatus capable of reading a document image with high accuracy without being affected by external light, and an image forming apparatus including the image reading apparatus. It is to provide.

  In order to achieve the above object, an invention according to claim 1 is directed to an LED for illuminating an original reading surface, an imaging lens for imaging reflected light from the original, and an optical image formed by the imaging lens. Reading apparatus including a photoelectric conversion element that converts a signal into a potential signal, provided with a plurality of band pass filters having different wavelength bands of external light for blocking transmission, and transmitting the least amount of external light among the plurality of band pass filters A band pass filter is selected and switched, and the frequency range of the LED is changed so that the selected band pass filter cannot be cut off.

  An image forming apparatus according to a fifth aspect includes the image reading apparatus according to the first aspect.

  According to the present invention, among a plurality of bandpass filters having different wavelength bands of external light that blocks transmission, the bandpass filter that transmits the least amount of external light (three-wave fluorescent lamps, external light such as sunlight, etc. is the most). The bandpass filter that can be blocked well is selected and switched, and the frequency range of the LED is changed so that it cannot be blocked by the selected bandpass filter. Mixing of external light into the reflected light is suppressed. For this reason, the original image can be affected by external light even when the platen is not completely closed, such as when reading a book document, or in an environment that is susceptible to external light such as fluorescent light or sunlight. And can be read with high accuracy.

  For this reason, the original image can be affected by external light even when the platen is not completely closed, such as when reading a book document, or in an environment that is susceptible to external light such as fluorescent light or sunlight. Can be read with high accuracy, and a high-quality image can be stably obtained in the image forming apparatus.

1 is a side sectional view of an image forming apparatus according to the present invention. 3 is a cross-sectional view in the sub-scanning direction of the image reading apparatus according to the present invention. FIG. 3 is a flowchart showing a reading operation procedure of the image reading apparatus according to the present invention. It is a figure which shows the interruption | blocking image of the external light by the band pass filter in the image reader which concerns on this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

[Image forming apparatus]
FIG. 1 is a side sectional view of an image forming apparatus according to the present invention. The illustrated image forming apparatus 1 is a monochrome copying machine, and includes an image reading device 2 according to the present invention at the upper part of the apparatus main body 1A. A discharge tray 3 is provided below the discharge tray 3. An image forming unit 4 is disposed inside the apparatus main body 1A, and a paper feeding unit 5 is disposed below the image forming unit 4.

  The image forming unit 4 forms an image by an electrophotographic method. The image forming unit 4 is a photosensitive drum 6 as an image carrier arranged rotatably, a charger 7 arranged around the photosensitive drum 6, and a laser scanner unit ( LSU) 8, a developing device 9, a transfer roller 10, and a cleaning device 11.

  The paper feed unit 5 includes a detachable paper feed cassette 12 and a pick roller 13 and a paper feed roller 14 disposed in the vicinity thereof. Here, a plurality of sheets S are stacked and accommodated in the sheet cassette 12, and the sheets S in the sheet cassette 12 are sequentially picked up from the upper one by the pick roller 13, and are fed by the sheet feed roller 14. It is sent out to the paper conveyance path P.

  The paper transport path P extends upward from the paper supply unit 5 to the paper discharge tray 3, and the registration roller 15, the transfer roller 10, the fixing device 16, and the transport of the paper transport path P from below. A roller 17 and a paper discharge roller 18 are sequentially arranged.

  Next, an image forming operation of the image forming apparatus 1 configured as described above will be described.

  When the image forming operation is started, in the image forming unit 4, the photosensitive drum 6 is rotationally driven in the arrow direction (clockwise) in FIG. 1 by a driving unit (not shown), and the surface thereof is set to a predetermined potential by the charger 7. Uniformly charged. In the image reading device 2, the original image is read as described later, and a laser beam based on an electric signal transmitted from the image reading device 2 is output from the laser scanner unit 8 to expose the surface of the photosensitive drum 6. When scanned, an electrostatic latent image corresponding to image information is formed on the photosensitive drum 6. Then, the electrostatic latent image formed on the photosensitive drum 6 is developed by the developing device 9 using toner as a developer to be visualized as a toner image.

  Further, the paper S accommodated in the paper feed cassette 12 of the paper feed unit 5 is picked up from the uppermost one by the pick roller 13 and sent out to the paper transport path P by the paper feed roller 14. Then, the sheet S sent out to the sheet conveyance path P in this way is conveyed to the registration roller 15 through the sheet conveyance path P and is temporarily put in the registration roller 15, and then the toner on the photosensitive drum 6. The image is supplied to the image forming unit 4 at a predetermined timing synchronized with the image.

  In the image forming unit 4, the sheet S supplied to the transfer nip between the photosensitive drum 6 and the transfer roller 10 is conveyed while being pressed against the photosensitive drum 6 by the transfer roller 10, so that the surface thereof is exposed to light. The toner image on the drum 6 is transferred. Then, the sheet S on which the toner image is transferred is conveyed to the fixing device 16 and is heated and pressurized in the process of passing through the fixing nip of the fixing device 16 to receive the toner image. The toner remaining on the surface of the photosensitive drum 6 (transfer residual toner) after the transfer of the toner image onto the paper S is removed by the cleaning device 11, and the photosensitive drum 6 whose surface is cleaned is prepared for the next image forming operation. .

Thus, the sheet S having the toner image fixed on the surface thereof by the fixing device 16 is conveyed by the conveying roller 17 along the sheet conveying path P to the sheet discharging roller 18, and the sheet discharging tray 18 by the sheet discharging roller 18. 3 to complete the series of image forming operations.
[Image reading device]
Next, a characteristic configuration of the image reading apparatus 2 according to the present invention will be described with reference to FIG.

  FIG. 2 is a cross-sectional view of the image reading apparatus according to the present invention in the sub-scanning direction. The illustrated image reading apparatus 2 includes an optical frame 19 that is a box-like structure constituting a housing. A contact glass 20 is provided on the upper surface of the substrate. A white reference plate 21 is provided at the end of the contact glass 20 for determining the white reference of the reading density.

  The optical frame 19 accommodates first and second movable carriages 22 and 23 that are movable in the sub-scanning direction. Here, the first moving carriage 22 includes a white LED 24 that illuminates a document placed on the contact glass 20, and a first reflection mirror that reflects reading light (reflected light) reflected by the document in a 90 ° direction. The second carriage 23 is provided with a second reflection mirror 26 that reflects the reflected light reflected by the first reflection mirror 25 in the 90 ° direction, and the reflection reflected by the second reflection mirror 26. A third reflecting mirror 27 is further provided for reflecting light in the 90 ° direction. These first and second movable carriages 22 and 23 are arranged along a guide rail (not shown) in the sub-scanning direction (left and right in FIG. 2). Direction).

  Further, inside the optical frame 19, a plurality of bandpass filters 28 having different wavelength bands of external light (light from a three-wavelength fluorescent lamp, sunlight, etc.) that blocks transmission, an imaging lens 29, and photoelectric conversion The CCD 30 as an element is coaxially arranged and accommodated, and the reading light (reflected light) from the document reflected by the third reflecting mirror 27 and the external light mixed therewith reach the bandpass filter 28. As will be described later, external light is blocked by the bandpass filter 28, and only the reading light (reflected light) passes through the bandpass filter 28. Then, the reading light (reflected light) transmitted through the band pass filter 28 is converged by the imaging lens 29 and then enters the CCD 30 and forms an image on the CCD 30.

  Next, the image reading operation of the document reading apparatus 2 configured as described above will be described below with reference to FIGS. 3 is a flowchart showing a reading operation procedure of the image reading apparatus, and FIG. 4 is a view showing an image of blocking external light by a bandpass filter in the image reading apparatus.

  When a document is placed on the contact glass 20 of the image reading device 2 and a not-shown pressure plate (DP) is closed (step S1 in FIG. 3), external light passes through the plurality of bandpass filters 28 and is transmitted therethrough. A band-pass filter 28 (a band-pass filter and a filter selector that can best block external light such as a three-wavelength fluorescent lamp or sunlight) 28 is selected and switched (step S2). The band pass filter 28 is switched by a filter circuit (not shown).

  Next, the frequency band of the white LED 24 is changed so that the selected bandpass filter 28 cannot block the reading light (reflected light), and the original is detected at that frequency (step S3). The frequency range of the white LED 24 changes by switching the clock cycle of the white LED 24 in a software manner.

  That is, the light emitted from the white LED 24 toward the document is reflected by the document surface, and the reflected light is reflected in the 90 ° direction by the first reflecting mirror 25 of the first moving carriage 22 and then the second movement. Reflected in the 90 ° direction by the second reflecting mirror 26 and the third reflecting mirror 27 of the carriage 23, transmitted through the band-pass filter 28 to the imaging lens 29, and converged by passing through the imaging lens 29. Then, the image is formed on the CCD 30, read by the CCD 30, and converted into an electrical signal. At this time, the external light is blocked from being transmitted by the band pass filter 28, and only the reading light (reflected light) is transmitted through the band pass filter 28. That is, as shown in an image in FIG. 4, since external light is blocked by the band pass filter 28, only reading light (reflected light) passes through the band pass filter 28 and reaches the CCD 30.

  The document detection is thus completed (step S4), the band pass filter 28 is switched to the selected one, and the reading light (reflected light) can be blocked by the band pass filter 28 selected by the frequency range of the white LED 24. It is changed so that it cannot be done.

  Then, a copying operation becomes possible, and when the user operates the start switch (step S5), a predetermined image reading operation is started. That is, the document placed on the contact glass 20 while the first moving carriage 22 and the second moving carriage 23 shown in FIG. 2 move along the guide rail (not shown) in the sub-scanning direction (left and right direction in FIG. 2). , The light emitted from the white LED 24 of the first moving carriage 22 is directed to the original, and the original is illuminated by this light. The light that illuminates the original is reflected by the original, and the reflected light is reflected by the first reflecting mirror 25 of the first moving carriage 22 in the 90 ° direction, and then the second reflecting mirror of the second moving carriage 23. 26 and the third reflecting mirror 27 are respectively reflected in the 90 ° direction, pass through the band-pass filter 28, reach the imaging lens 29, converge by passing through the imaging lens 29, and form an image on the CCD 30. Then, it is read by the CCD 30 and converted into an electrical signal.

  When the document image is optically read by the image reading apparatus 2 as described above, the electric signal is transmitted to the laser scanner unit 8 shown in FIG. 1, and the laser scanner unit 8 transmits laser light based on the electric signal. And the above-described image forming operation is performed in the image forming apparatus 1 shown in FIG. 1 to obtain a desired copy image.

  after that. If the pressure plate (DP) is opened (step S6) and the original is taken out, a series of image forming operations (copying operations) is completed.

  As described above, according to the image reading apparatus 2 of the present invention, among the plurality of bandpass filters 28 having different wavelength bands of external light that blocks transmission, the bandpass filter (three wavelengths) that transmits the least amount of external light. The bandpass filter that can best block external light such as a fluorescent lamp or sunlight) 28 is selected and switched, and the frequency range of the white LED 24 is set so that the selected bandpass filter 28 cannot block it. Since it is made to change, mixing of the external light to the reflected light emitted from the white LED 24 and reflected from the document surface is suppressed. For this reason, the original image can be affected by external light even when the platen is not completely closed, such as when reading a book document, or in an environment that is susceptible to external light such as fluorescent light or sunlight. And can be read with high accuracy.

  Since the document image can be read with high accuracy by the image reading apparatus 2 as described above, a high quality image can be stably obtained in the image forming apparatus 1 shown in FIG.

  In this embodiment, the embodiment in which the present invention is applied to a monochrome copying machine and an image reading apparatus provided in the monochrome copying machine has been described. However, the present invention is not limited to a monochrome or color facsimile machine other than a copying machine. Needless to say, the present invention can be similarly applied to any other image forming apparatus such as a multifunction peripheral and an image reading apparatus provided therein.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1A Image forming apparatus main body 2 Image reading apparatus 3 Paper discharge tray 4 Image forming part 5 Paper feeding part 6 Photosensitive drum 7 Charger 8 Laser scanner unit (LSU)
DESCRIPTION OF SYMBOLS 9 Developing device 10 Transfer roller 11 Cleaning device 12 Paper feed cassette 13 Pick roller 14 Paper feed roller 15 Registration roller 16 Fixing device 17 Transport roller 18 Paper discharge roller 19 Optical frame 20 Contact glass 21 White reference plate 22 First moving carriage 23 2 moving carriage 24 white LED
25 First Reflection Mirror 26 Second Reflection Mirror 27 Third Reflection Mirror 28 Band Pass Filter 29 Imaging Lens 30 CCD (Photoelectric Conversion Element)
P Paper transport path S Paper

Claims (2)

In an image reading apparatus comprising: an LED that illuminates a document reading surface; an imaging lens that forms an image of reflected light from the document; and a photoelectric conversion element that converts an optical image formed by the imaging lens into a potential signal ,
Provide multiple bandpass filters with different wavelength bands of external light to block transmission, select and switch the bandpass filter with the least amount of external light to transmit among the multiple bandpass filters, and block with the selected bandpass filter An image reading apparatus, wherein the frequency range of the LED is changed so that it cannot be performed. An image forming apparatus comprising the image reading apparatus according to claim 1.

Images