JP5568526B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning device and an image forming apparatus to which the optical scanning device is applied.

  The image forming apparatus is provided with an optical scanning device for forming an electrostatic latent image on the surface of the photosensitive drum. This type of optical scanning device emits laser light from a light source toward a deflector and scans the surface of the photosensitive drum by deflecting the emitted laser light by the deflector.

  Patent Document 1 exemplifies this type of optical scanning device. In the optical scanning device, the deflector deflects the laser light emitted from the light source while rotating around the rotation axis. In the optical scanning device, in order to reduce the area of the deflecting surface of the deflector, laser light is incident on the deflecting surface from the lower part of the imaging lens and the center of the imaging lens in the main scanning direction.

  FIG. 5 is a cross-sectional view in the sub-scanning direction schematically showing the configuration of the optical scanning device in Patent Document 1. In FIG. In FIG. 5, a light source 101, a collimator lens 102, an aperture stop 108, and a cylindrical lens 103 are arranged on a plane including the center of the imaging lens 105 a and parallel to the cross section in the sub-scanning direction Z of the imaging lens 105 a. An incident optical system and a deflector 104 are arranged. X is the optical axis direction from the deflector 104 toward the scanned surface 14a of the photosensitive drum, and Y is the main scanning direction of the imaging lens 105a.

JP 2009-31317 A

  The deflected light that is the laser light deflected by the deflector 104 enters the imaging lens 105a. At this time, the deflected light has a property of curving to the side opposite to the light source 101 as it comes closer to the end of the imaging lens 105a in the main scanning direction Y (see FIG. 6). That is, as shown in FIG. 6, when the deflected light L102 at the end portion in the main scanning direction Y is incident on the imaging lens 105a, the deflected light L102 at the end in the main scanning direction Y is curved to the opposite side to the light source 101. Therefore, the incident position of the deflected light on the imaging lens 105a is shifted between the center and the end in the main scanning direction Y of the imaging lens 105a. Therefore, it is necessary to ensure a large length, that is, a thickness in the sub-scanning direction Z of the imaging lens 105a.

  Further, the curvature has a property of increasing as the incident angle of the laser beam to the deflector 104 increases. Even if the distance between the deflector 104 and the imaging lens 105a is reduced to reduce the size of the optical scanning device, interference between the incident light on the deflector 104 and the deflected light from the deflector 104 is prevented. Therefore, it is necessary to increase the incident angle of the laser beam to the deflector 104. In this case, since the curvature becomes large, it is necessary to increase the thickness of the imaging lens 105a.

  SUMMARY An advantage of some aspects of the invention is to provide an optical scanning apparatus capable of reducing the thickness of an imaging lens and an image forming apparatus to which the optical scanning apparatus is applied.

An optical scanning device according to an aspect of the present invention includes a light source that emits laser light and a rotation shaft, and deflects and scans the laser light emitted from the light source while rotating around the rotation shaft. A deflector, an imaging lens that forms an image of the laser light deflected and scanned by the deflector on a surface to be scanned, and the laser light emitted from the light source is reflected toward the deflection surface of the deflector. A first reflecting member, and the rotation axis of the deflector and the normal line of the first reflecting member include the optical axis of the imaging lens and are parallel to a cross section in the sub-scanning direction of the imaging lens. The laser is disposed on a plane, and the light source is disposed on the opposite side of the first reflecting member across the optical axis from the deflector to the scanned surface, and the laser emitted from the light source Light from the deflector to the scanned surface Via the optical path that intersects the axis, characterized in that toward the first reflecting member.

  According to this configuration, the laser light emitted from the light source travels toward the first reflecting member via the optical path intersecting the optical axis from the deflector to the scanned surface, and is reflected toward the deflector by the first reflecting member. Therefore, for example, by adjusting the direction of the reflecting surface of the first reflecting member, the incident angle of the laser beam to the deflector can be easily reduced. Thereby, the curvature of the deflected light from the deflector can be reduced, and the thickness of the imaging lens can be reduced.

  Further, since the thickness of the imaging lens can be reduced by adjusting the direction of the reflecting surface of the first reflecting member, the position and direction of the light source are adjusted so that the incident angle becomes small. Does not require a large adjustment space. For this reason, it is possible to reduce the size of the optical scanning device.

  In the above configuration, a second reflection is provided on a plane parallel to the cross section in the sub-scanning direction of the imaging lens on the side opposite to the first reflecting member across the optical axis from the deflector to the scanned surface. A member is disposed, and the second reflecting member transmits the laser beam emitted from the light source so that the laser beam intersects an optical axis from the deflector to the scanned surface. It is preferable to reflect toward the member.

  According to this configuration, the second reflecting member reflects the laser light emitted from the light source toward the first reflecting member so that the laser light intersects the optical axis from the deflector to the scanned surface. There is no need to place the light source opposite to the first reflecting member. For this reason, the degree of freedom in installing the light source is improved.

In the above configuration, the light source is disposed so that the laser light emitted from the light source is incident on the second reflecting member in parallel with an optical axis from the deflector to the scanned surface . Is preferred.

  According to this configuration, the light source is disposed so that the laser light emitted from the light source is incident on the second reflecting member in parallel with the optical axis from the deflector to the surface to be scanned. The thickness of the scanning device can be reduced.

  In the above-described configuration, the laser beam emitted from the light source is further formed with an incident optical system that linearly forms an image toward the deflector, and the incident optical system is disposed to face the second reflecting member. Preferably it is.

  According to this configuration, since the incident optical system is disposed to face the second reflecting member, the thickness of the optical scanning device can be reduced.

  In the above configuration, the deflector is preferably a MEMS mirror. According to this configuration, since the deflector is configured with a MEMS mirror, the optical scanning device can be reduced in size as compared with the case where the deflector is configured with a polygon mirror.

  An image forming apparatus according to another aspect of the present invention includes an image carrier that carries an electrostatic latent image, and the above-described optical scanning device that irradiates laser light with the circumferential surface of the image carrier as the scanned surface; Is provided.

  According to the present invention, the thickness of the imaging lens can be reduced, and as a result, the optical scanning device can be made compact.

1 is a diagram illustrating an example of a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a plan view schematically showing a configuration of an optical scanning device according to an embodiment of the present invention. 1 is a cross-sectional view schematically showing a configuration of an optical scanning device according to an embodiment of the present invention. It is sectional drawing which showed an example of the principal part structure of the optical scanning device. It is sectional drawing of the subscanning direction which showed the structure of the conventional optical scanning device. It is a figure for demonstrating the subject in the conventional optical scanning device.

  Hereinafter, an optical scanning device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus A including an optical scanning device 11 according to an embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus A includes an optical scanning device 11, a developing device 12, a charger 13, a photosensitive drum 14, a transfer roller 15, and a fixing device 16.

  The photosensitive drum 14 is a cylindrical member, and is rotated in the clockwise direction in FIG. 1 in response to a driving force from a motor (not shown). The charger 13 charges the surface of the photosensitive drum 14 substantially uniformly.

  The optical scanning device 11 includes a light source such as a laser diode, and irradiates the surface (scanned surface) of the photosensitive drum 14 that is substantially uniformly charged by the charger 13 with laser light corresponding to image data. Thus, an electrostatic latent image of the image data is formed. The developing device 12 includes a toner container that stores toner, and supplies toner to the surface of the photosensitive drum 14 on which the electrostatic latent image is formed to form a toner image. The toner image formed on the photosensitive drum 14 is transferred to a recording sheet or a transfer belt (not shown) conveyed on the conveyance path P by a transfer roller 15 described later.

  A transfer roller 15 is disposed at a position facing the photosensitive drum 14. The transfer roller 15 is made of a conductive rubber material or the like, and transfers the toner image formed on the photosensitive drum 14 onto a recording paper or transfer belt that is transported through the transport path P.

  The fixing device 16 includes a fixing roller 160 having a built-in heater and the like, and a pressure roller 161 provided at a position facing the fixing roller 160. The fixing device 16 heats and conveys the recording paper on which the toner image is formed. The formed toner image is fixed.

  Next, an image forming operation of the image forming apparatus A will be briefly described. First, the surface of the photosensitive drum 14 is charged almost uniformly by the charger 13. Then, the surface of the charged photosensitive drum 14 is exposed by the optical scanning device 11, and an electrostatic latent image of an image formed on the recording paper is formed on the surface of the photosensitive drum 14. The electrostatic latent image is visualized by attaching toner to the surface of the photosensitive drum 14 by the developing device 12, and the toner image on the surface of the photosensitive drum 14 is transferred to the recording paper by the transfer roller 15. After this operation is performed, the toner image transferred onto the recording paper by the fixing device 16 is fixed.

  FIG. 2 is a plan view schematically showing the configuration of the optical scanning device 11 according to an embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing the configuration of the optical scanning device 11 according to an embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating an example of a main configuration of the optical scanning device 11.

  The optical scanning device 11 includes a semiconductor laser 101 (light source), a collimator lens 102, a cylindrical lens 103, a MEMS mirror 104 (deflector), imaging lenses 105a and 105b, a first mirror 106 (first reflecting member), and a second mirror. 107 (second reflecting member).

  These components pass along the optical axis direction X from the MEMS mirror 104 toward the photosensitive drum surface 14a on a plane passing through the center of the imaging lens 105a and parallel to the sub-scanning direction Z of the imaging lens 105a. The semiconductor laser 101, the collimator lens 102, the cylindrical lens 103, the MEMS mirror 104, the first mirror 106, the second mirror 107, the imaging lens 105a, and the imaging lens 105b are arranged in this order. On the optical axis ahead of the imaging lens 105b, a circumferential surface of the photosensitive drum 14 serving as a scanned surface is disposed.

  The MEMS mirror 104, the first mirror 106, the imaging lens 105a, and the imaging lens 105b are located above the light source 101, the collimator lens 102, the cylindrical lens 103, and the second mirror 107 with respect to the sub-scanning direction Z. Is arranged.

  Furthermore, the MEMS mirror 104, the first mirror 106, and the second mirror 107 are configured such that the rotation axis of the MEMS mirror 104, the normal line of the first mirror 106, and the normal line of the second mirror 107 are positioned on the plane. Arranged to do.

  Thereby, in this optical scanning device 11, the laser light emitted by the semiconductor laser 101 passes through the center of the imaging lens 105a and is repeatedly reflected on a plane parallel to the sub-scanning direction Z of the imaging lens 105a. To the deflection surface of the MEMS mirror 104.

  The semiconductor laser 101 emits laser light having a predetermined wavelength toward the collimator lens 102 and the cylindrical lens 103 in parallel with the optical axis direction X.

  The collimator lens 102 and the cylindrical lens 103 are disposed so as to face the semiconductor laser 101 along the optical axis direction X, and constitute an incident optical system in the present invention. The collimator lens 102 and the cylindrical lens 103 image the laser beam emitted from the semiconductor laser 101 in a linear shape.

  The MEMS mirror 104 is disposed to face the imaging lens 105a. The MEMS mirror 104 has a mirror surface and a rotation axis parallel to the sub-scanning direction Z of the imaging lens 105a. This rotating shaft is rotationally driven by a driving source (not shown). The MEMS mirror 104 deflects the laser light imaged by the collimator lens 102 and the cylindrical lens 103 while rotating around the rotation axis.

  The imaging lenses 105a and 105b are, for example, toric lenses having fθ characteristics. These lenses 105a and 105b are arranged so as to face each other, collect the laser light deflected by the MEMS mirror 104, and form an image on the photosensitive drum surface 14a (scanned body).

  The first mirror 106 is disposed above the optical axis from the MEMS mirror 104 toward the photosensitive drum surface 14a as viewed in the sub-scanning direction Z. The first mirror 106 is arranged so that the laser light reflected by the second mirror 107 is incident on the deflection surface of the MEMS mirror 104.

  The second mirror 107 is disposed below the imaging lens 105a and on the opposite side of the first mirror 106 with respect to the optical axis. The second mirror 107 is arranged so that the laser light imaged by the collimator lens 102 and the cylindrical lens 103 is incident on the first mirror 106.

  Since the first mirror 106 and the second mirror 107 are arranged on opposite sides with respect to the optical axis, the laser light reflected by the second mirror 107 toward the first mirror 106 is the optical axis. Intersect.

  According to such a configuration, the laser light emitted from the semiconductor laser 101 is imaged by the collimator lens 102 and the cylindrical lens 103 and is incident on the second mirror 107. Then, the incident laser light L 3 that is the laser light incident on the second mirror 107 is reflected by the second mirror 107 toward the first mirror 106. At this time, the incident laser beam L3 intersects the optical axis.

  The incident laser light L3 reflected toward the first mirror 106 is reflected toward the MEMS mirror 104 by the first mirror 106. The incident laser light L3 reflected toward the MEMS mirror 104 is deflected in the main scanning direction Y by the MEMS mirror 104. As a result, the deflected light beams L1 and L2, which are the incident laser beams L3 deflected by the MEMS mirror 104, are irradiated onto the photosensitive drum surface 14a.

  The deflected light L1 is a laser beam centered in the main scanning direction Y of the imaging lens 105a, and the deflected light L2 is a laser light at the end portion in the main scanning direction Y.

  As described above, the incident laser light L3 is reflected by the second mirror 107 toward the first mirror 106 so as to intersect the optical axis, and then reflected by the first mirror 106 toward the MEMS mirror 104. The

  Further, as the angle formed between the incident surface of the incident laser light L3 incident on the MEMS mirror 104 and the optical axis becomes smaller, the deflected light L1 and the deflected light L1 at the time when the deflected light L2 and the deflected light L2 enter the imaging lens 105a. The deviation in the sub-scanning direction Z from the deflected light L2 is reduced, and the curve (curve C) is reduced.

  Thereby, for example, the direction of the reflecting surfaces of the first mirror 106 and the second mirror 107 is set so that the angle formed by the incident laser light L3 from the first mirror 106 toward the MEMS mirror 104 with the optical axis becomes small. By adjusting the thickness, the thickness of the imaging lens 105a can be easily reduced. As a result, the position and direction of the semiconductor laser 101, the collimator lens 102, and the cylindrical lens 103 are set so that the angle formed between the laser beam imaged by the collimator lens 102 and the cylindrical lens 103 and the optical axis becomes small. Since an adjustment space as in the case of adjustment is not required, the optical scanning device 11 can be reduced in size.

  In the present embodiment, the laser light imaged by the collimator lens 102 and the cylindrical lens 103 is reflected by the second mirror 107, but the present invention is not limited to this example. For example, without providing the second mirror 107, the semiconductor laser 101, the collimator lens 102, and the cylindrical lens so that the focused laser beam is emitted toward the first mirror 106 from below the optical axis. 103 may be arranged.

DESCRIPTION OF SYMBOLS 11 Optical scanning device 14a Photosensitive drum surface 101 Semiconductor laser 102 Collimator lens 103 Cylindrical lens 104 MEMS mirror 105a Imaging lens 106 1st mirror 107 2nd mirror

Claims (6)

A light source that emits laser light;
A deflector having a rotation axis and deflecting and scanning the laser light emitted from the light source while rotating around the axis of the rotation axis;
An imaging lens for imaging the laser beam deflected and scanned by the deflector on a scanned surface;
A first reflecting member that reflects the laser light emitted from the light source toward a deflecting surface of the deflector;
The rotation axis of the deflector and the normal line of the first reflecting member are arranged on a plane including the optical axis of the imaging lens and parallel to the sub-scanning direction cross section of the imaging lens,
The light source is disposed on the opposite side of the first reflecting member across the optical axis from the deflector to the scanned surface;
The laser beam emitted from the light source travels toward the first reflecting member through an optical path intersecting with an optical axis from the deflector to the scanned surface. On the plane parallel to the cross section in the sub-scanning direction of the imaging lens, a second reflecting member is disposed on the opposite side of the first reflecting member across the optical axis from the deflector to the scanned surface. And
The second reflecting member reflects the laser light emitted from the light source toward the first reflecting member so that the laser light intersects an optical axis from the deflector to the scanned surface. The optical scanning device according to claim 1. The light source is arranged so that the laser light emitted by the light source is incident on the second reflecting member in parallel with an optical axis from the deflector to the scanned surface. The optical scanning device according to claim 2. An incident optical system that linearly forms an image of the laser beam emitted from the light source and directs it toward the deflector;
The optical scanning device according to claim 2, wherein the incident optical system is disposed to face the second reflecting member.   5. The optical scanning device according to claim 1, wherein the deflector is a MEMS mirror. 6. An image carrier for carrying an electrostatic latent image;
Irradiating a laser beam to the peripheral surface of the image bearing member as the surface to be scanned, the optical scanning device according to any one of claims 1 to 5,
An image forming apparatus comprising:

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