JP2007233137A - Optical scanner and image forming apparatus with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner capable of forming a clear electrostatic latent image on a scan surface of a scanned body with precision. <P>SOLUTION: This laser scanner unit 8 is so configured as to deflect laser light from a laser diode 81 by a polygon mirror 84, thereafter, to guide the light to the photoreceptor drum 31 outside of a housing 80 through fθ lenses 85, 86, and to write the electrostatic latent image by performing horizontal scanning on the drum surface 31a of the photoreceptor drum 31. Also the laser scanner 8 is provided with a dust protective glass 88 to prevent foreign substances from entering the housing 80 between the fθ lenses 85, 86 and the photoreceptor drum 31. This dust protective glass 88 has a function of reducing light quantity of the laser light so that light quantity of the laser light having passed through the dust protective glass two or more times is smaller than a lower limit of the light quantity capable of writing onto the drum surface 31a. Moreover, the laser light having passed through the dust protective glass 88 is made incident to the drum surface 31a almost at a right angle thereto. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical scanning device that forms an electrostatic latent image on a scanned object by optical scanning, and an image forming apparatus including the same.

  2. Description of the Related Art Conventionally, there is known an optical scanning device that is mounted on an image forming apparatus such as a copying machine, a facsimile machine, or a printer, and writes an electrostatic latent image on a scanning surface of a scanning object by optical scanning.

  FIG. 6 is a schematic view showing an optical path of laser light in a conventional laser scanner unit. As shown in FIG. 6, the conventional laser scanner unit 108 (optical scanning device) deflects laser light from a light source (not shown) by a polygon mirror 184, and then ffo lenses 185 and 186, a reflection mirror 187, and a dust proof. Light is guided to the photosensitive drum 131 disposed outside the housing 180 through the glass 188, and horizontal scanning is executed on the drum surface 131 a of the photosensitive drum 131.

  By the way, in the laser scanner unit 108, when the laser light reflected by the reflection mirror 187 is incident on the drum surface 131a of the photosensitive drum 131 substantially perpendicularly (see the dotted line in FIG. 6), After the laser beam specularly reflected by the surface 131 a follows the reverse path, it is deflected (reflected) by the polygon mirror 184 and again enters the drum surface 131 a of the photosensitive drum 131. At this time, although the amount of laser light gradually decreases by passing through each of the members 184 to 188, the degree of decrease is relatively small, so the amount of laser light incident on the drum surface 131a again becomes photosensitive. It is difficult to be smaller than the lower limit value of the amount of light that can be written to the drum surface 131a of the body drum 131. As a result, the members 184 to 188 are regularly reflected on the drum surface 131a in addition to the laser light emitted from the light source and incident on the drum surface 131a via the members 184 to 188 on the drum surface 131a of the photosensitive drum 131. Since the electrostatic latent image is written by the laser light incident on the drum surface 131a again through a plurality of times, a ghost image is formed on the drum surface 131a of the photosensitive drum 131.

  Therefore, in order to avoid the above inconvenience, the conventional laser scanner unit 108 shifts the optical path of the laser beam reflected by the reflection mirror 187 so that the laser beam is perpendicular to the drum surface 131a of the photosensitive drum 131. The incident light is inclined at a predetermined angle (see the chain line in FIG. 6) so that the reflected light from the drum surface 131a does not return to the housing 180 through the dust-proof glass 188.

Patent Document 1 discloses a scanning optical apparatus using an overfilled optical system configured such that an antireflection film is deposited on the surface of dustproof glass so that the light quantity distribution of laser light on the drum surface of the photosensitive drum is uniform. Is disclosed.
JP 2001-75036 A

  However, in the above-described conventional laser scanner unit 108, the laser beam reflected by the reflecting mirror 187 is incident on the drum surface 131a of the photosensitive drum 131 at an angle with respect to the drum surface 131a as shown in FIG. There is an inconvenience that the projected shape S ′ of the laser light projected onto 131 a is stretched and deformed in the rotation direction (arrow C direction) of the photosensitive drum 131. As a result, the projected shape S ′ of the laser light is different from the cross-sectional shape (substantially circular) of the laser light, so that it is difficult to accurately form an electrostatic latent image on the drum surface 131a of the photosensitive drum 131. There is a problem.

  The present invention has been made to solve the above-described problems, and an optical scanning device capable of accurately forming a clear electrostatic latent image on a scanning surface of an object to be scanned and an image including the same. An object is to provide a forming apparatus.

  In order to achieve the above object, an optical scanning device according to claim 1 of the present invention includes a light source capable of emitting laser light, a deflector for deflecting laser light emitted from the light source, and the deflector. An image forming means for forming an image of the deflected laser light is provided in the apparatus main body, and after the laser light from the light source is deflected by the deflector, it is disposed outside the apparatus main body through the image forming means. In an optical scanning device that guides light to a scanned object and performs horizontal scanning on the scanning surface of the scanned object to write an electrostatic latent image, the imaging means on the optical path of the laser beam and the scanned object The glass member further includes a glass member that is disposed between the body and prevents foreign matter from entering the apparatus main body, and the glass member has a light quantity of laser light that has passed through the glass member a plurality of times. Less than the lower limit of the amount of light that can be written to the scanning surface So that the have a dimming function that reduces the amount of laser light, wherein the laser light passing through the glass member is incident substantially perpendicular to the scanning plane of the scanning target.

  In the optical scanning device according to the first aspect, as described above, the laser beam that has passed through the glass member is incident on the scanning surface of the scanned body substantially perpendicularly, and is projected onto the scanning surface of the scanned body. Since the projection shape of the laser beam can be suppressed from being deformed by being stretched in a predetermined direction, for example, the projection shape of the laser beam can be substantially matched with the cross-sectional shape (substantially circular shape) of the laser beam. Thereby, an electrostatic latent image can be accurately formed on the scanning surface of the scanning object. In addition, the amount of laser light is set on the glass member for preventing foreign matter intrusion so that the amount of laser light that has passed through the glass member a plurality of times is smaller than the lower limit value of the amount of light that can be written to the scanning surface of the scanned object. By adding a dimming function to reduce, when the laser beam that has passed through the glass member is incident substantially perpendicularly on the scanning surface of the scanning object, the reflected light is regularly reflected on the scanning surface of the scanning object. Even if the laser beam follows the reverse path and is deflected (reflected) by the deflector and is incident again on the scanning surface of the scanning object, the laser beam incident on the scanning surface again passes through the glass member three times. Therefore, the light amount of the laser light can be made sufficiently smaller than the lower limit value of the light amount that can be written to the scanning surface of the scanning object. Thus, the electrostatic latent image can be written only by the laser light that has passed the glass member once and entered the scanning surface of the scanned object on the scanning surface of the scanned object. The formation of a ghost image on the scanning surface can be sufficiently suppressed. As a result, a clear electrostatic latent image can be formed on the scanning surface of the object to be scanned. As described above, in the optical scanning device according to the first aspect, a clear electrostatic latent image can be accurately formed on the scanning surface of the scanning object.

  In the optical scanning device according to claim 1, preferably, the glass member includes a neutral density filter (claim 2). If comprised in this way, the light quantity of the laser beam which passes a glass member can be reduced easily.

  According to a third aspect of the present invention, there is provided an image forming apparatus for forming an electrostatic latent image on a scanning surface of an object to be scanned by the laser beam from the optical scanning apparatus according to the first or second aspect. It is characterized by forming.

  In the image forming apparatus according to the third aspect, as described above, since the optical scanning apparatus capable of accurately forming a clear electrostatic latent image on the scanning surface of the scanned object is used, A clear image can be accurately formed on the recording medium.

  According to the optical scanning device of the present invention, the projected shape of the laser light is substantially matched to the sectional shape of the laser light by suppressing the deformation of the projected shape of the laser light projected on the scanning surface of the scanned object. On the other hand, the electrostatic latent image is written on the scanning surface of the scanned object only by the laser beam that has passed the glass member once and incident on the scanned surface of the scanned object. Since it is possible to sufficiently suppress the formation of a ghost image on the scanning surface, a clear electrostatic latent image can be accurately formed on the scanning surface of the scanning object. Further, according to the image forming apparatus of the present invention, since the optical scanning device having the above effect is used, a clear image can be accurately formed on the recording medium.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing the overall configuration of a printer according to an embodiment of the present invention. FIGS. 2 and 3 are perspective views for explaining the configuration of a laser scanner unit of the printer shown in FIG. It is a top view. 4 is a schematic view showing the optical path of the laser beam in the laser scanner unit shown in FIG. 2, and FIG. 5 is a diagram of the laser scanner unit projected on the drum surface of the photosensitive drum shown in FIG. It is the elements on larger scale which showed the projection shape of the laser beam. First, an overall configuration of a printer 1 according to an embodiment of the present invention will be described with reference to FIG. In this embodiment, an example in which the image forming apparatus of the present invention is applied to the printer 1 will be described.

  As shown in FIG. 1, the printer 1 includes a box-shaped housing 1 a, and a paper (recording medium) is transported along a transport path L provided in the housing 1 a while being not illustrated. An image is formed on the paper based on image data transmitted from a terminal or the like. The conveyance path L includes a horizontal portion L1 extending substantially horizontally from the front to the rear of the printer 1 (from right to left in FIG. 1), and a vertical portion L2 rising substantially vertically from the rear end portion of the horizontal portion L1. It is configured to be substantially L-shaped when viewed from the side.

  The printer 1 stores a sheet and supplies the sheet to the image forming unit 3 described below, an image forming unit 3 that forms an image on the sheet supplied from the sheet feeding unit 2, and image formation And a fixing unit 4 for fixing the toner image transferred to the sheet by the unit 3 to the sheet.

  The paper feeding unit 2 includes a paper feeding cassette 21 that is attached to the paper feeding unit 2 so as to be able to be drawn forward and is disposed below the horizontal part L1 of the transport path L in the mounted state. The paper feeding unit 2 takes out the paper in the paper feeding cassette 21 one by one by the pickup roller 22, and sends the paper to the horizontal portion L1 of the transport path L by the paper feeding rollers 23, 24, 25 and 26. The image forming apparatus 3 is configured to supply the image forming unit 3 with a predetermined timing after temporarily waiting by the registration roller 27.

  The paper feed unit 2 has a manual feed tray 28 attached to the front surface of the housing 1a. The paper placed on the manual feed tray 28 is taken out by a pickup roller 29, and the paper is taken out by the paper feed roller 24 and 26, it is possible to feed one sheet at a time to the horizontal portion L1 of the transport path L.

  The paper feed cassette 21 has a substantially rectangular parallelepiped shape with an open upper surface, and is configured to be able to stack and store paper.

  The image forming unit 3 is configured to transfer a toner image to a sheet after forming the toner image on the drum surface 31 a of the photosensitive drum 31. In other words, the image forming unit 3 includes a photosensitive drum 31 disposed substantially at the center in the front-rear direction of the horizontal portion L1 of the conveyance path L, a charging unit 32 disposed above the photosensitive drum 31, and a photosensitive member. The developing unit 33 disposed in front of the photosensitive drum 31, the transfer unit 34 disposed below the photosensitive drum 31, the cleaning unit 35 disposed behind the photosensitive drum 31, and the image formation. And a laser scanner unit (LSU) 8 disposed above the fixing unit 4. The photosensitive drum 31 and the drum surface 31a are examples of the “scanned body” and “scanning surface” of the present invention, and the laser scanner unit 8 is an example of the “optical scanning device” of the present invention.

  The photosensitive drum 31 rotates clockwise in FIG. 1, and the drum surface 31 a is uniformly charged by the charging unit 32 on the drum surface 31 a, and then the image is detected by the laser scanner unit 8. An electrostatic latent image is formed by irradiating laser light based on the data from between the charging unit 32 and the developing unit 33, and toner from the developing unit 33 is further formed on the drum surface 31a on which the electrostatic latent image is formed. By being supplied, a toner image is formed.

  The paper supplied from the paper supply unit 2 is conveyed while being pressed against the photosensitive drum 31 by the transfer roller 34a of the transfer unit 34, thereby forming on the drum surface 31a of the photosensitive drum 31 on the surface of the paper. The transferred toner image is transferred to the fixing unit 4 after that. The toner and residual charge remaining on the drum surface 31a of the photosensitive drum 31 after transfer are removed by the cleaning unit 35.

  The fixing unit 4 includes a heat roller 41 and a pressure roller 42, and the toner image is fixed to the paper by heat and pressure by sandwiching the paper on which the toner image is transferred by the rollers 41 and 42. It is supposed to be.

  Then, the sheet on which the toner image is fixed is discharged by a discharge roller 51 to a discharge unit 5 formed on the upper surface of the housing 1a.

  In the printer 1 of this embodiment, the switchback unit 6 is provided between the horizontal part L1 of the transport path L and the paper feed cassette 21 so that images can be formed on both sides of the paper. Further, a conveying roller 7 is disposed at an appropriate position between the fixing unit 4 and the discharge roller 51 and in the conveying path L ′ of the switchback unit 6.

  Next, the configuration of the laser scanner unit 8 will be described with reference to FIGS.

  As shown in FIGS. 2 and 3, the laser scanner unit 8 includes a laser diode 81, lens portions 82 and 83, a polygon mirror 84, fθ lenses 85 and 86, a folding mirror 87, and a dust proof in a housing 80. Glass 88 is provided. The housing 80 is an example of the “apparatus main body” of the present invention, and the polygon mirror 84 is an example of the “deflector” of the present invention. The fθ lenses 85 and 86 are examples of the “imaging unit” of the present invention, and the dust-proof glass 88 is an example of the “glass member” of the present invention. The laser scanner unit 8 is actually configured with a light-shielding cover (not shown) attached, but FIG. 2 shows a state where the cover is removed for convenience of explanation.

  The laser diode 81 has a function as a “light source” of the present invention that modulates and emits an image data signal generated and output by an image memory (not shown) into a laser beam. The laser diode 81 is electrically connected to a circuit board 89 that controls the laser light emission timing and the like. The lens portions 82 and 83 are configured by, for example, a collimator lens or a prism, and have a function of converting incident laser light into parallel light.

  The polygon mirror 84 is formed in a regular hexagonal flat plate shape in plan view, and is rotated from the lens unit 83 while rotating at a constant speed in a predetermined direction (counterclockwise direction in FIG. 3) by driving a motor (not shown). The laser beam is configured to be deflected toward the fθ lens 85. The fθ lenses 85 and 86 are arranged at appropriate positions in the housing 80 so that their arch portions face each other, and have a function of scanning the laser light deflected by the polygon mirror 84 on the photosensitive drum 31 at a constant speed. Have. The folding mirror 87 is provided to reflect the laser light from the fθ lens 86 and guide it to the photosensitive drum 31.

  Further, the dust-proof glass 88 has a foreign matter intrusion preventing function for preventing foreign matter such as dust from entering the housing 80, and corresponds to the optical path of the laser light between the folding mirror 87 and the photosensitive drum 31. The housing 80 is attached to the housing 80 by being fitted into an opening 80 a provided on the bottom surface of the housing 80.

  In the laser scanner unit 8, the laser light emitted from the laser diode 81 is guided to the polygon mirror 84 via the lens portions 82 and 83. The laser light incident on the rotating polygon mirror 84 is reflected and deflected by the mirror surface of the polygon mirror 84, is reflected by the folding mirror 87 through the fθ lenses 85 and 86, and passes through the dust-proof glass 88. Thus, exposure of the drum surface 31a of the photosensitive drum 31 that rotates around the axis (in the direction of arrow B in FIG. 2) orthogonal to the scanning direction while being horizontally scanned in the predetermined scanning direction (in the direction of arrow A in FIG. 2). It is guided to the position.

  Here, in the present embodiment, the laser beam that has been reflected by the folding mirror 87 and then passed through the dust-proof glass 88 is configured to enter the drum surface 31a of the photosensitive drum 31 substantially perpendicularly (see FIG. 4). . Thereby, the projection shape S (see FIG. 5) of the laser light projected onto the drum surface 31a of the photosensitive drum 31 is suppressed from being deformed by being stretched in the rotational direction (arrow B direction) of the photosensitive drum 31, for example. Therefore, the projected shape S of the laser beam can be made to substantially match the sectional shape (substantially circular shape) of the laser beam.

  In the present embodiment, the dust-proof glass 88 has a dimming function for reducing the amount of laser light passing through the dust-proof glass 88 in addition to the above-described foreign matter intrusion prevention function. That is, the dustproof glass 88 passes the dustproof glass 88 only once and the amount of laser light incident on the drum surface 31a of the photosensitive drum 31 is equal to or greater than the lower limit of the amount of light that can be written to the drum surface 31a. On the other hand, the light amount of the laser light is decreased so that the light amount of the laser light that has passed through the dust-proof glass 88 and entered the drum surface 31a is less than the lower limit value of the light amount that can be written to the drum surface 31a. It is configured.

  Although not shown, the dustproof glass 88 is configured by attaching a film-like neutral density (ND) filter to the surface of the glass body. As such a neutral density filter, it is preferable to use a filter capable of reducing the amount of laser light after passing through the neutral density filter to about 20% compared to the amount of laser light before passage. Note that a comparatively thick neutral density (ND) filter itself may be used as the dust-proof glass 88.

  According to the dustproof glass 88 having the above configuration, when the laser light reflected by the folding mirror 87 and passed through the dustproof glass 88 is incident on the drum surface 31a of the photosensitive drum 31 substantially perpendicularly, the drum surface 31a out of the incident light. Even if the laser beam specularly reflected in step 1 follows the reverse path and is deflected (reflected) by the polygon mirror 84 and is incident on the drum surface 31a of the photosensitive drum 31 again, the laser beam incident on the drum surface 31a again is dust-proof glass 88. Therefore, the amount of the laser light can be made sufficiently smaller than the lower limit of the amount of light that can be written to the drum surface 31a. Therefore, it is possible to write an electrostatic latent image on the drum surface 31a of the photosensitive drum 31 only by the laser light that passes through the dust-proof glass 88 once and enters the drum surface 31a. The formation of a ghost image on the drum surface 31a can be sufficiently suppressed.

  The laser scanner unit 8 detects the horizontal synchronization signal and adjusts the laser beam emission timing based on this signal, thereby controlling the writing timing to the photosensitive drum 31.

  That is, the laser scanner unit 8 further includes a reflecting mirror 90, a sensor member 91, a sensor circuit board 92, and a condenser lens 93 in the housing 80.

  In FIG. 3, the reflecting mirror 90 is disposed at the front left end of the fθ lens 86, and after being deflected by the polygon mirror 84, passes through the fθ lens 85 and enters the vicinity of the scanning start end (left end) of the fθ lens 86. The laser beam is configured to be reflected toward the sensor member 91.

  The sensor member 91 is disposed at a position where the laser light from the reflecting mirror 90 can be received via the condenser lens 93, and the light receiving surface receives the laser light so that the sensor circuit board 92 is horizontal. A synchronization signal is acquired.

  The condensing lens 93 is disposed between the reflecting mirror 90 and the sensor member 91, and condenses the laser light from the reflecting mirror 90 in order to cause the sensor circuit board 92 to accurately acquire the horizontal synchronization signal. The sensor member 92 has a function of being incident.

  In the present embodiment, as described above, the laser light that has passed through the dust-proof glass 88 is incident on the drum surface 31a of the photosensitive drum 31 substantially perpendicularly, whereby the projection shape S of the laser light projected onto the drum surface 31a is obtained. For example, it is possible to prevent the photosensitive drum 31 from being stretched and deformed in the rotation direction (arrow B direction), so that the projection shape S of the laser light substantially matches the cross-sectional shape (substantially circular shape) of the laser light. be able to. Thereby, an electrostatic latent image can be accurately formed on the drum surface 31 a of the photosensitive drum 31. Further, the laser beam is applied to the dust-proof glass 88 for preventing the entry of foreign matter so that the amount of laser light that has passed through the dust-proof glass 88 a plurality of times is smaller than the lower limit of the amount of light that can be written to the drum surface 31a of the photosensitive drum 31. By adding a dimming function that reduces the amount of light, when the laser light that has passed through the dust-proof glass 88 is incident on the drum surface 31a of the photosensitive drum 31 substantially perpendicularly, the drum surface 31a out of the incident light. Even if the laser beam specularly reflected in step 1 follows the reverse path and is deflected (reflected) by the polygon mirror 84 and is incident on the drum surface 31a of the photosensitive drum 31 again, the laser beam incident on the drum surface 31a again is dust-proof glass 88. Since the laser beam passes through 3 degrees, the amount of the laser light can be made sufficiently smaller than the lower limit of the amount of light that can be written to the drum surface 31a.Thereby, it is possible to write an electrostatic latent image on the drum surface 31a of the photosensitive drum 31 only by the laser light that passes through the dust-proof glass 88 once and enters the drum surface 31a. The formation of a ghost image can be sufficiently suppressed. As a result, a clear electrostatic latent image can be formed on the drum surface 31 a of the photosensitive drum 31. From the above, the laser scanner unit 8 according to the present embodiment can form a clear electrostatic latent image on the drum surface 31 a of the photosensitive drum 31 with high accuracy.

  Further, in the present embodiment, as described above, a dimming function for reducing the amount of laser light is added to the dust-proof glass 88 having a foreign matter intrusion preventing function for preventing foreign matter such as dust from entering the housing 80. Therefore, unlike the case where a dimming member having only a dimming function is separately provided, an increase in the number of parts can be suppressed.

  Further, in the present embodiment, as described above, the dust-proof glass 88 is configured by attaching a dimming (ND) film to the surface of the glass body, so that the amount of laser light that passes through the dust-proof glass 88 can be easily increased. Can be reduced.

  In the present embodiment, as described above, the laser scanner unit 8 capable of accurately forming a sharp electrostatic latent image on the drum surface 31a of the photosensitive drum 31 is used. A clear image can be formed with high accuracy.

  In the above-described embodiment, an example in which the present invention is applied to a printer as an example of an image forming apparatus has been described. However, the present invention is not limited to this, and can also be applied to a copying machine other than a printer, a facsimile machine, or a multifunction machine thereof. It is.

  In the above-described embodiment, an example in which one laser diode 81 is provided as a light source has been described. However, the present invention is not limited thereto, and a light source including two or more laser diodes may be used.

1 is a cross-sectional view illustrating an overall configuration of a printer according to an embodiment of the present invention. It is a perspective view for demonstrating the structure of the laser scanner unit of the printer shown in FIG. FIG. 3 is a plan view of the laser scanner unit shown in FIG. 2. It is the schematic which showed the optical path of the laser beam in the laser scanner unit shown in FIG. FIG. 5 is a partially enlarged view showing a projected shape of laser light of a laser scanner unit projected onto the drum surface of the photosensitive drum shown in FIG. 4. It is the schematic which showed the optical path of the laser beam in the conventional laser scanner unit. It is the elements on larger scale which showed the projection shape of the laser beam of the laser scanner unit projected on the drum surface of the photosensitive drum shown in FIG.

Explanation of symbols

1 Printer (image forming device)
8 Laser scanner unit (optical scanning device)
31 Photosensitive drum (scanned body)
31a Drum surface (scanning surface)
80 Housing (device main body)
81 Laser diode (light source)
84 Polygon mirror (deflector)
85,86 fθ lens (imaging means)
88 Dust-proof glass (glass member)

Claims (3)

A light source capable of emitting a laser beam, a deflector for deflecting the laser beam emitted from the light source, and an image forming means for imaging the laser beam deflected by the deflector are provided in the apparatus body, and the light source After the laser beam from the beam is deflected by the deflector, the laser beam is guided to the scanning object disposed outside the apparatus main body through the imaging unit, and horizontal scanning is performed on the scanning surface of the scanning object. In an optical scanning device for writing an electrostatic latent image,
A glass member that is disposed between the imaging means on the optical path of the laser beam and the scanned body, and that prevents foreign matter from entering the apparatus main body;
The glass member is a dimming that reduces the light amount of the laser light so that the light amount of the laser light that has passed through the glass member a plurality of times is smaller than a lower limit value of the light amount that can be written to the scanning surface of the scanned object. Has a function,
An optical scanning device characterized in that a laser beam that has passed through the glass member is incident substantially perpendicularly on a scanning surface of the scanning object.   The optical scanning device according to claim 1, wherein the glass member includes a neutral density filter.   An image forming apparatus, wherein an electrostatic latent image is formed on a scanning surface of a scanning object by a laser beam from the optical scanning apparatus according to claim 1 to form an image on a recording medium.

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