JP2009086594A - Image reading unit, document reading device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading unit that prevents stray light from entering the optical path of an image forming optical system such as a lens while maintaining a simple structure. <P>SOLUTION: A plate-shaped shield member 22 provided with a circular through hole 21 as a light transmission part in a central region is disposed in an optical path between a CCD 4 as a photoelectric conversion element and a lens 3, and an inner shape of the through hole 21 is set smaller than an outer shape of a barrel 23 of the lens 3. The shield member 22 can prevent incident stray light parallel to the optical axis from being incident on a light receiving surface of the CCD 4 to whereby suppress deteriorations due to light noise in read image quality, S/N ratio, MTF and color reproduction and enable satisfactory image reading. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading unit that collects reflected light from a reading target on a photoelectric conversion element via a lens and reads image information, and a document reading apparatus and an image forming apparatus on which the image reading unit is mounted. is there.

  In recent years, as image input means for digital copying machines, facsimile machines, electronic filing devices, etc., it consists of a lens after deflecting reflected light including image data obtained by reflecting a document from a light source with a plurality of mirrors. 2. Description of the Related Art Image reading apparatuses configured to be guided to a photoelectric conversion element (CCD: Charged Coupled Device, CMOS: Complementary Metal Oxide Semiconductor) via an imaging optical system have become mainstream.

  FIG. 9 is a schematic configuration diagram showing an example of a conventional document reading apparatus. A cylindrical xenon lamp 1 is provided as a light source for illuminating a document, and irradiation light emitted from the xenon lamp 1 is applied to the contact glass 2. Irradiation is performed on the placed document, diffuse reflected light from the document is condensed on the CCD 4 via the lens 3, and converted into an electrical signal by the CCD 4 to obtain document image information.

  In the document reading apparatus shown in FIG. 9, the first traveling body 6 including the first mirror 5 that deflects the reflected light from the document and the xenon lamp 1 and the light from the first mirror 5 receive the light from the first mirror 5 toward the lens 3. When the second traveling body 9 including the second mirror 7 and the third mirror 8 to be deflected is provided so as to be movable, and the first traveling body 6 and the second traveling body 9 travel along the contact glass 2, The document is scanned.

  In addition, in the image reading unit including the lens 3 and the CCD 4 and the substrate 10 on which the CCD 4 is mounted, an inner cover 11 is provided to cover the lens 3 and the CCD 4 in order to prevent external emission of electromagnetic waves emitted from the substrate 10. An opening 11 a for allowing the original reflected light to enter the lens 3 is formed upstream of the optical path of the original reflected light in the lens 3 of the inner cover 11.

  In the conventional document reading apparatus, an optical image obtained when light is irradiated on the document surface is formed on the light receiving surface of the CCD 4 via the lens 3, but stray light that does not pass through the lens 3 is reflected on the CCD 4. In some cases, the light-receiving surface may be intruded, which causes problems such as deterioration of a read image due to optical noise, a decrease in S / N ratio, deterioration of MTF (Modulation Transfer Function), and deterioration of color reproducibility.

For this reason, the optical system of the image reading unit is provided with a light blocking member for blocking unnecessary light around the lens, as shown in Patent Document 1, and this light blocking member allows the CCD to pass without passing through the optical system. The light that directly reaches is blocked.
JP 2004-194018 A

  However, in the prior art, a box-shaped light shielding member 12 installed between the lens 3 and the CCD 4 is installed as shown in the partial plan view of the plane for explaining stray light incidence in the image reading unit shown in FIG. By doing so, stray light incident obliquely with respect to the optical axis of the lens 3 can be blocked by the light blocking member 12, but stray light incident parallel to the optical axis of the lens 3 cannot be prevented.

  In order to cope with this, a structure in which the opening 12a of the light shielding member 12 is circular is conceivable. However, since the clearance with the lens 3 cannot be completely eliminated, a clearance such as a sponge is filled. It is necessary to install additional parts.

  The present invention has been made in view of such a background, and an image reading unit that prevents stray light from entering the optical path of an imaging optical system such as a lens while maintaining a simple configuration, and its An object of the present invention is to provide a document reading apparatus and an image forming apparatus equipped with an image reading unit.

  In order to achieve the above object, an invention according to claim 1 is an image reading unit that illuminates a reading object and collects reflected light from the reading object on a photoelectric conversion element through a lens to read image information. A light shielding member having a light transmission portion is provided in an optical path between the lens and the photoelectric conversion element, and an inner shape of the light transmission portion is set smaller than a lens barrel outer shape of the lens. Depending on the configuration, a light shielding member is provided between the lens and the photoelectric conversion element, and a light transmission part smaller than the lens barrel is formed on the light shielding member, so that stray light incident parallel to the optical axis is prevented from entering the photoelectric conversion element. Therefore, the image can be read satisfactorily without deterioration of the read image due to optical noise, S / N ratio, MTF, and color reproducibility.

  According to a second aspect of the present invention, in the image reading unit according to the first aspect, the inner shape of the light transmission part is set larger than the light flux in the light transmission part of the reflected light emitted from the lens. Therefore, the image forming light of the original reflected light is not optically kicked by the light shielding member before entering the photoelectric conversion element, so that a good image can be obtained.

  According to a third aspect of the present invention, in the image reading unit according to the first or second aspect, the light shielding portion of the light shielding member is moved from the opening of the cover member covering the image reading unit toward the photoelectric conversion element without passing through the lens. It is characterized in that it is arranged at a site that blocks incident light, and with this configuration, stray light that enters from the opening of the cover member does not enter the photoelectric conversion element, so not only stray light that enters parallel to the optical axis but also light Since stray light having an angle with respect to the axis does not enter the photoelectric conversion element, a good image without deterioration of the read image due to optical noise, deterioration of S / N ratio, deterioration of MTF, deterioration of color reproducibility, etc. can be obtained. Obtainable.

  According to a fourth aspect of the present invention, in the image reading unit according to any one of the first to third aspects, the light shielding member is positioned by abutting against a lens barrel. By striking the lens against the lens barrel, there is no incidence of stray light incident from between the lens and the light shielding member and at an angle with respect to the optical axis, and a better image can be obtained. It becomes easy to position.

  According to a fifth aspect of the present invention, in the image reading unit according to any one of the first to fourth aspects, the light shielding member is formed in a part of the housing of the image reading unit. By providing the light shielding member by using the housing of the reading unit, it is possible to obtain the above-described effects at a low cost without the necessity of providing a separate member.

  According to a sixth aspect of the present invention, there is provided a document reading apparatus including a document reading unit that illuminates a document and collects reflected light from the document on a photoelectric conversion element through a lens to read a document image. The image reading unit according to any one of claims 1 to 5 is mounted as a reading unit. With this configuration, the original reading unit deteriorates the read image, the S / N ratio decreases, the MTF deteriorates, and the color. Since deterioration of reproducibility is suppressed, a good original image is read.

  According to a seventh aspect of the present invention, in the image forming apparatus that includes an image reading unit and an image forming unit that receives the image information from the image reading unit and forms an image, the image reading unit according to the sixth aspect. The image reading apparatus is mounted, and this configuration suppresses deterioration of the read image, S / N ratio, MTF, color reproducibility, and the like in the image reading unit. Formation takes place.

  According to the image reading unit of the present invention, since the light shielding member is provided between the lens and the photoelectric conversion element, and the light transmitting portion smaller than the lens barrel is formed on the light shielding member, the stray light incident in parallel with the optical axis is photoelectrically converted. It is possible to prevent the light from entering the element, and it is possible to read an image satisfactorily without deterioration of a read image due to optical noise, a decrease in S / N ratio, deterioration of MTF, deterioration of color reproducibility, and the like.

  According to the document reading apparatus and the image forming apparatus provided with the image reading unit according to the present invention, it is possible to suppress the optical nozzles in the photoelectric conversion element, thereby realizing excellent document reading or image formation.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  Note that the image reading unit of the present embodiment is mounted on the image reading apparatus shown in FIG. 9, and in the following description, members corresponding to the members described in FIG. Detailed description is omitted.

  FIG. 1 is a perspective view showing a configuration of an image reading unit according to a first embodiment of the present invention, and FIG. 2 is a partial plan view of the plane of the first embodiment.

  In FIG. 1, a plate-shaped light shielding member 22 having a circular through-hole 21 as a light transmitting portion formed in the center is disposed in the optical path between the CCD 4 of the photoelectric conversion element and the lens 3. The inner shape (inner diameter) of the through hole 21 is set smaller than the outer shape (outer diameter) of the lens barrel 23 of the lens 3.

  For this reason, as shown in FIG. 2, the stray light incident in parallel to the optical axis is formed so that the inner diameter A of the through hole 21 of the light shielding member 22 and the outer diameter L of the lens barrel 23 satisfy A <L. It is possible to prevent the light from entering the light receiving surface of the CCD 4, and it is possible to suppress the deterioration of the read image, the S / N ratio, the MTF, the color reproducibility, and the like as optical noise, and a good image reading is performed. .

  FIG. 3 is a partial cross-sectional plan view showing the optical path of the imaging light of the original reflected light in the present embodiment, and the alternate long and short dash line shows the optical path of the imaging light of the original reflecting light emitted from the lens 3. The inner diameter A of the through hole 21 is set to be larger than the light beam diameter B in the through hole 21 of the reflected document light emitted from the lens 3. For this reason, the light imaged on the CCD 4 by the lens 3 is not optically kicked.

  FIG. 4 is an explanatory diagram when the light shielding member is installed in the conventional document reading apparatus shown in FIG. 9, and the inner cover 11 which is a cover member for covering the image reading unit in the conventional document reading apparatus includes the lens 3 or In addition to preventing stray light incident on the CCD 4, it has a function of blocking electromagnetic waves generated from the substrate 10 on which the CCD 4 is mounted from being released to the outside.

  Here, as shown in FIG. 4, depending on the installation position of the light shielding member 22 in the optical axis direction, a light beam incident from the opening 11a of the inner cover 11 may enter the CCD 4 as stray light.

  Therefore, as shown in the partial plan view of the plane of the configuration of the second embodiment according to the present invention shown in FIG. 5, the light shielding member 22 is brought close to the lens 3, and the light incident from the opening 11 a of the inner cover 11 is caused by the light shielding member 22. If the light shielding member 22 and the through hole 21 are arranged at a position where light is shielded, stray light having an angle with respect to the optical axis can be shielded.

  FIG. 6 is a partial cross-sectional plan view showing the configuration of the image reading unit according to the third embodiment of the present invention. The light shielding member 22 is positioned by abutting against the end of the lens barrel 23 of the lens 3.

  With this configuration, stray light having an angle with respect to the optical axis can be shielded, and the light shielding member 22 can be easily positioned. In this case, if the light shielding member 22 is provided with a mechanism for moving the light shielding member 22 in parallel with the optical axis, the positioning of the lens barrel 23 can be easily set.

  FIG. 7 is a perspective view showing the configuration of the image reading unit according to the fourth embodiment of the present invention. The light shielding member 22 and the through hole 21 are formed in a part of the housing 25 for holding the constituent members of the image reading unit. By providing the same function as the light shielding member 22 using the housing 25, there is no need to provide a separate member, and the effects of the above embodiments can be obtained at low cost. .

  FIG. 8 is a block diagram of a laser printer which is an embodiment of an image forming apparatus equipped with an image reading unit according to the present invention, and the same members as those corresponding to the components of the document reading apparatus described in FIG. A detailed description will be omitted with reference numerals.

  The image forming unit 30 of this laser printer is basically a known configuration, and includes a photoreceptor 31, a charging roller 32, a developing device 33, a transfer roller 34, a cleaning device 35, a fixing device 36, an optical scanning device 37, and a paper feed. The cassette 38, a registration roller pair 39, a paper feed roller 40, a paper transport path 41, a paper discharge roller 42, a paper discharge tray 43, and the like.

  The image reading unit 45 has the same configuration as that of the document reading apparatus described with reference to FIG. 9, and adopts the improved structure of the image reading unit according to the present invention as in the configuration of each of the embodiments. is there.

  In the image reading unit 45, the first traveling body 6 and the second traveling body 9 are moved, a document (not shown) on the contact glass 2 is scanned, and a reflected light image from the document is formed on the CCD 4. In the CCD 4, the reflected light image of the original is photoelectrically converted into an analog image signal, and the original is read. Then, after the reading of the document is completed, the first traveling body 6 and the second traveling body 9 return to the home position.

  The analog image signal output from the CCD 4 is converted into a digital image signal by an analog / digital converter (not shown), and each image processing (binarization, multi-value conversion, Gradation processing, scaling processing, editing processing, etc.).

  The image processing signal is output to the optical scanning device 37, and a latent image is formed on the surface of the photosensitive member 31 by optical scanning of the photosensitive member 31 by the optical scanning device 37. The latent image on the photoreceptor 31 is developed with toner by the developing device 33, and the toner image is transferred onto the paper by the transfer roller 34. The transferred paper is subjected to a fixing process by the fixing device 36 and then discharged to a paper discharge tray 43 by a paper discharge roller 42.

  As described above, in this image forming apparatus, by adopting the improved structure of the image reading unit in each of the above embodiments, the read image is deteriorated, the S / N ratio is lowered, the MTF is deteriorated, and the color reproducibility in the original reading unit. Therefore, it is possible to form a good and high-quality image.

  The present invention is applied as an image reading unit or an image reading apparatus for illuminating a document in an image forming apparatus such as a copying machine, a facsimile, or a scanner.

1 is a perspective view illustrating a configuration of an image reading unit according to a first embodiment of the present invention. Plane partial sectional view of Embodiment 1 Plane partial cross-sectional view showing an optical path of imaging light of document reflected light in the present embodiment Explanatory drawing when a light shielding member is installed in the conventional document reading apparatus shown in FIG. Plane partial sectional view showing the configuration of Embodiment 2 according to the present invention Plane partial sectional view showing the configuration of Embodiment 3 of the image reading unit according to the present invention. The perspective view which shows the structure of Embodiment 4 of the image reading unit which concerns on this invention. 1 is a configuration diagram of a laser printer that is an embodiment of an image forming apparatus equipped with an image reading unit according to the present invention. Schematic configuration diagram showing an example of a conventional document reading apparatus Plane partial cross-sectional view for explaining stray light incidence in a conventional image reading unit

Explanation of symbols

3 Lens 4 CCD
11 Inner cover 11a Inner cover opening 21 Light-shielding member through-hole (light transmission part)
22 light shielding member 23 lens barrel 25 housing 30 image forming unit 45 image reading unit

Claims (7)

In an image reading unit that illuminates a reading target, collects reflected light from the reading target on a photoelectric conversion element via a lens, and reads image information,
An image reading device comprising: a light-shielding member having a light transmission portion in an optical path between the lens and the photoelectric conversion element, wherein an inner shape of the light transmission portion is set smaller than a lens barrel outer shape of the lens. unit.   The image reading unit according to claim 1, wherein an inner shape of the light transmission part is set to be larger than a light flux of the reflected light emitted from the lens in the light transmission part.   The light-shielding portion of the light-shielding member is disposed at a portion that shields light incident in the direction of the photoelectric conversion element from the opening of the cover member that covers the image reading unit without passing through the lens. 3. The image reading unit according to 1 or 2.   The image reading unit according to claim 1, wherein the light shielding member is positioned by abutting against a lens barrel of the lens.   The image reading unit according to claim 1, wherein the light shielding member is formed in a part of a housing of the image reading unit. In a document reading apparatus provided with a document reading unit that illuminates a document and collects reflected light from the document on a photoelectric conversion element via a lens to read a document image.
6. A document reading apparatus comprising the image reading unit according to claim 1 mounted as the document reading unit. An image forming apparatus including an image reading unit and an image forming unit that receives image information from the image reading unit and forms an image.
An image forming apparatus comprising the image reading device according to claim 6 as the image reading unit.

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