JP2001108931A - Light beam scanner and image forming device using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an light beam scanner and an image forming device using this which can miniaturize the whole device and can reduce the number of parts for cost reduction by hollowing the rotary shaft of a deflector to make the hollow part to be the optical path of incident beams toward an image forming lens. SOLUTION: In order to form the image of light beams 60 on a surface to be scanned with a necessary spot diameter required for forming the image, this light beam scanner makes the beams 60 incident on the reflecting surface 3a of a pyramidal mirror block 3 of a deflector 1 by tilting with respect to its normal direction and makes the reflected beams incident on an image forming lens. In the scanner, the rotary shaft 5 of the deflector is hollowed to make the hollow part 10 to be the optical path of the beams 60 toward the image forming lens and the surface 3a of the block 3 is formed to shape the beam diameter of the main scanning direction and that of the sub-scanning direction of the beams toward the image forming lens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a laser printer,
The present invention relates to a light beam scanning device applicable to a digital copying machine, a facsimile, and the like, and an image forming apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, a rotating polygon mirror or a holographic scanner has been known as a light beam deflecting means in an optical scanning device. The rotating polygon mirror deflects a light beam a plurality of times by a plurality of mirror surfaces during one rotation of the polygon mirror. on the other hand,
The holographic scanner deflects a light beam a plurality of times by a plurality of hologram gratings while the holographic disk makes one rotation. As described above, since the rotary polygon mirror and the holographic scanner deflect the light beam a plurality of times by a plurality of mirror surfaces or a plurality of hologram gratings, there is a problem of surface tilt.

In view of such a problem, the mirror surface is inclined with respect to the rotation axis of the deflector, a light beam to be deflected is made incident along the rotation axis, reflected by the mirror surface, and the reflected beam is deflected by 360 degrees. Deflectors have been proposed. The mirror surface of this deflector is called a pyramidal mirror,
The deflection system using the pyramidal mirror is different from the above-described rotary polygon mirror or holographic scanner in which a light beam is deflected a plurality of times by a plurality of mirror surfaces or a plurality of hologram gratings, and the light beam is deflected by only one mirror surface. Therefore, there is no problem of trouble as described above.

As described above, in the deflection method using a pyramidal mirror, a light beam to be deflected is made incident along the rotation axis of the deflector and deflected and reflected by the pyramidal mirror. If the light source is arranged on a straight line along the rotation axis, or if the light source is not arranged on a straight line along the rotation axis, a reflecting mirror is provided on the straight line along the rotation axis, and the light beam emitted from the light source is The light beam is refracted and reflected by the reflection mirror and is incident along the rotation axis of the deflector.

[0005]

However, in the configuration in which the light sources for emitting the light beams are arranged on a straight line along the rotation axis, the space in which the light sources are arranged is in the sub-scanning direction which is orthogonal to the main scanning direction. Since it must be provided in the scanning direction, there is a problem that the entire apparatus becomes large in the sub-scanning direction.

On the other hand, if the light source is not arranged on a straight line along the rotation axis, the reflection mirror must be provided on the straight line along the rotation axis, so that the number of parts increases and the cost increases. Problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. The rotating shaft of the deflector has a hollow structure, and the hollow portion has an optical path of an incident beam directed to an imaging lens. Accordingly, it is an object of the present invention to provide a light beam scanning device capable of reducing the size of the entire device, reducing the number of parts and reducing the cost, and an image forming apparatus using the same.

[0008]

According to the first aspect of the present invention,
In order to form a light beam on the surface to be scanned with a required spot diameter required for image formation, the light beam is incident on the reflecting surface of the pyramidal mirror block of the deflector at an angle with respect to its normal direction, In a light beam scanning device that causes a reflected beam to be incident on an imaging lens, a rotating shaft of the deflector has a hollow structure, and the hollow portion serves as an optical path of a light beam directed to the imaging lens, and a pyramidal mirror block of the deflector is provided. The reflecting surface is shaped so as to shape the beam diameter of the light beam toward the imaging lens in the main scanning direction and the beam diameter in the sub-scanning direction.

According to a second aspect of the present invention, in the first aspect of the present invention, the diameter of the hollow portion is at least a required light spot diameter necessary for forming an image on the surface to be scanned. It is characterized by the following.

According to a third aspect of the present invention, in the first aspect of the present invention, the inner surface of the hollow portion is subjected to a process of absorbing a light beam.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the shape of the light beam incident portion or the outgoing portion of the pyramidal mirror block is a collimator lens shape for converting the divergent light beam emitted from the light source into a parallel light beam. It is characterized by having become.

According to a fifth aspect of the present invention, in the first aspect of the invention, the size of the light beam incident on the pyramidal mirror block of the deflector is set to be larger than the size of the reflection surface of the pyramidal mirror block. It is characterized by having been done.

According to a sixth aspect of the present invention, there is provided a light beam scanning device according to the first aspect, an imaging lens of the light beam scanning device, and a light beam imaged by the imaging lens and scanned by the light beam. And an image forming apparatus comprising

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a light beam scanning device according to the present invention and an image forming apparatus using the same will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a deflector used in a light beam scanning device. The deflector 1 mainly includes a motor 2 and a pyramidal mirror block 3 described later.

As shown in FIG. 1, the motor 2 has a rotor part and a stator part formed in a disk-shaped case 4, and both ends of a rotating shaft 5 of the rotor part are located at the center of the case 4. Projecting from. When the rotor rotates with respect to the stator, the rotating shaft 5 rotates.

The rotating shaft 5 has a hollow structure. More specifically, a hollow portion 10 extending in the axial direction is formed through the center of the rotating shaft 5, and a light beam 60 emitted from a light source (not shown) passes through the hollow portion 10. You can pass through. That is, a part of the optical path of the light beam 60 emitted from the light source and directed to the imaging lens provided on the deflection side of the deflector 1 is formed in the hollow portion 10 of the rotating shaft 5.

The diameter of the hollow portion 10 is formed so that the light beam 60 emitted from the light source is at least a light spot diameter required for forming an image on the surface to be scanned. . Also, on the inner surface of the hollow portion 10,
The processing for absorbing the light beam 60 is performed,
In order to prevent the light from being irregularly reflected within 0, the light beam 60 that has been irregularly reflected can be absorbed. As a result, it is possible to prevent a ghost from occurring on the image and obtain a good image.

A pyramidal mirror block 3 is integrally attached to the upper end of the rotating shaft 5 projecting from the center of the case 4 by bonding or press fitting. The pyramidal mirror block 3 includes a pyramidal mirror block 3
Pyramidal mirror 3a as a reflecting surface of
The light beam 60 that has passed through the inside is inclined so as to be incident on the normal direction. The pyramidal mirror 3a is a light beam 6 that travels toward the imaging lens.
The shape is such that the beam diameter in the main scanning direction and the beam diameter in the sub-scanning direction of 0 are shaped. That is, the pyramidal mirror 3a is configured such that a part of the inclined surface of the pyramidal mirror block 3 forming the pyramidal mirror 3a has a beam diameter in the main scanning direction and a beam diameter in the sub-scanning direction of the light beam 60 toward the imaging lens. Has a shape that can be shaped. In the illustrated example, the central part of the inclined surface of the pyramidal mirror block 3 is a pyramidal mirror 3a. As described above, in order to make the inclined surface of the pyramidal mirror block 3 into the pyramidal mirror 3a, it is only necessary to form a reflection film on the part of the pyramidal mirror 3a. Still better. Hereinafter, the pyramidal mirror 3a will be described more specifically.

As shown in FIGS. 1 and 2, the outer shape of the pyramidal mirror 3a is such that the beam diameter corresponding to the main scanning direction of the light beam 60 toward the imaging lens is a and the beam diameter corresponding to the sub-scanning direction is a. b, the beam is formed so as to have the same size as the beam diameter in each direction, and the center position of the pyramidal mirror 3a is the rotation center position of the deflector 1, in other words, the light passing through the hollow portion 10. It is set according to the optical axis of the beam.

In the illustrated example, the pyramidal mirror 3a is inclined by 45 degrees with respect to the incident optical axis. Therefore, the light beam 60 deflected and reflected by the pyramidal mirror 3a is
As shown in FIG. 2, the beam diameter dimension corresponding to the main scanning direction is shaped into a and the beam diameter dimension corresponding to the sub-scanning direction is shaped into b, and the beam is emitted in a direction perpendicular to the incident optical axis. . In the example shown in FIG. 2, the pyramidal mirror 3
The light beam 60 deflected and reflected by the beam diameter dimension a in the main scanning direction is larger than the beam diameter dimension b in the sub scanning direction.
Is shaped into a longer ellipse.

When the pyramidal mirror block 3 is rotated by an effective scanning angle of view (a scanning angle capable of securing an effective writing width on the photosensitive member), the size and shape of the light beam 60 incident on the pyramidal mirror block 3 Is set so as to exceed at least the size and shape of the pyramidal mirror 3a. In particular, when a semiconductor laser is used as a light source, the cross-sectional shape of the light beam emitted from the semiconductor laser is different between a direction parallel to the bonding surface and a direction perpendicular to the bonding surface. Becomes elliptical, so that even if the pyramidal mirror block 3 is rotated by the effective scanning angle of view, the cross-sectional size of the light beam 60 is set to exceed the size of the pyramidal mirror 3a at least within the range. Must have been. However, simply increasing the beam diameter reduces the light use efficiency and makes it impossible to obtain the required power. Therefore, in consideration of this, the size of the cross section of the light beam 60 reduces the size of the pyramidal mirror 3a. It is better to set to exceed.

As described above, the light beam 60 emitted from the light source passes through the hollow portion 10 and then enters the pyramidal mirror block 3 and is deflected and reflected by the pyramidal mirror 3a, so that it is reflected in the main scanning direction. The beam is shaped into a beam diameter corresponding to the sub-scanning direction, emitted in a direction perpendicular to the direction of the incident optical axis, transmitted through an imaging lens described later, and formed on the surface to be scanned with a required spot diameter required for image formation. Imaged. Further, since the pyramidal mirror block 3 on which the pyramidal mirror 3a is formed is integrally attached to the rotating shaft 5, the pyramidal mirror 3 is formed.
The deflecting and reflecting direction of a and the shaping of the light beam 60 by the pyramidal mirror 3a can always be performed synchronously at the effective scanning angle of view.

Next, an image forming apparatus using the light beam scanning device to which the deflector 1 is applied will be described. FIG.
1, a charger 31, a developing unit 32, a transfer charger 33, and a cleaning unit 34 are arranged around the photoreceptor drum 30 in the order of rotation thereof, and at a position between the charger 31 and the developing unit 32. The above-described light beam scanning device 35 is provided so that the light beam emitted from the light source 20 is incident on the photosensitive drum 30 and is exposed.

The charger 31 and the optical writing position 36 are disposed below the photosensitive drum 30, and the light beam scanning device 35
Is provided below the photosensitive drum 30, the developing unit 32, and the cleaning unit. Further, the transfer charger 33 is disposed above the photosensitive drum 30.

A paper feed tray 37 for feeding the transfer paper to a transfer portion between the transfer charger 33 and the photosensitive drum 30 is provided below the light beam scanning device 35, and the transfer paper is provided with a feed roller 38 and a feed roller 38. Friction pad 39 pressed against
, And is largely inverted at the side of the developing unit 32, so that the position is aligned with the image formed on the photosensitive drum 30 by the pair of registration rollers 40 and 41 provided above the developing unit 32. The paper is fed to the transfer unit at the appropriate timing. A fixing unit 42 is provided in a transfer paper path after the transfer, and a paper discharge tray 43 is provided on a discharge side thereof.

The light beam emitted from the light source 22 passes through the hollow portion 10 and then enters the pyramidal mirror block 3, where it is shaped into a beam diameter corresponding to the main scanning direction and the sub-scanning direction by the pyramidal mirror 3a. Then, the light is repeatedly deflected within a certain angle range. Pyramidal mirror 3
The light beam deflected and reflected by the imaging lens (f)
θ lens) 44, the incident position 3 on the photosensitive drum 30
The image is corrected so that the image is formed on a straight line at 6 and the projection point moves at a constant speed, enters the photosensitive drum 30 via the reflection mirror 45 and the toroidal lens 46, and performs main scanning by deflection of the incident light. The sub-scanning is performed by the rotation of the photosensitive drum 30, an image corresponding to the image information signal is written, and an electrostatic latent image is formed. The light beam scanning device 35 is directly attached to the base cover 47 of the image forming apparatus.

The electrostatic latent image formed on the photosensitive drum 30 is developed by a developing unit 32 to form a toner image. The toner image is formed on a transfer sheet fed by a pair of registration rollers 40 and 41. Transcribed by action. After the transfer, the transfer paper separated from the photosensitive drum 30 is fixed by the fixing unit 42 and is discharged to the discharge tray 43. After the transfer, the toner remaining on the photosensitive drum 30 is cleaned by the cleaning unit 34.

According to the above embodiment, the rotary shaft 5 of the deflector 1 has a hollow structure, and the hollow portion 10 is used as the optical path of the incident beam toward the image forming lens. be able to. When the light source is not arranged on a straight line along the rotation axis, the reflecting mirror must be provided on the straight line along the rotation axis. In this case, it is not necessary to provide the reflection mirror, so that the number of parts can be reduced and the cost can be reduced. Furthermore, since the light beam emitted from the light source is shaped by the pyramidal mirror 3a into a beam diameter corresponding to the main scanning direction and the sub-scanning direction, there is no need to provide a slit member or the like for shaping the beam diameter, thereby reducing costs. it can.

Further, as shown in FIG. 3, the shape of the light beam incident portion 50 of the pyramidal mirror block 3 is formed into a collimator lens shape for collimating the divergent light beam emitted from the light source, so that a collimator lens or the like is formed. It is not necessary to provide the device, and the cost can be reduced. In FIG. 3, the shape of the light beam incident portion of the pyramidal mirror block 3 is a collimator lens shape, but as shown in FIG. May be formed into a collimator lens shape.

[0030]

According to the first aspect of the present invention, in order to form a light beam on a surface to be scanned with a required spot diameter required for image formation, the light beam is reflected on a reflecting surface of a pyramidal mirror block of a deflector. In a light beam scanning device, which is incident on the imaging lens at an angle with respect to its normal direction, the rotating shaft of the deflector has a hollow structure, and the hollow portion is incident on the imaging lens. The reflecting surface of the pyramidal mirror block of the deflector is shaped to shape the beam diameter of the light beam going to the imaging lens in the main scanning direction and the beam diameter in the sub-scanning direction. Therefore, the entire device can be downsized. In addition, since the light source is arranged on a straight line along the rotation axis, it is not necessary to provide the above-mentioned reflection mirror, and the number of parts can be reduced and the cost can be reduced. Further, since the light beam emitted from the light source is shaped by the pyramidal mirror into a beam diameter corresponding to the main scanning direction and the sub-scanning direction, there is no need to provide a slit member or the like for shaping the beam diameter, and the cost can be reduced. .

According to a second aspect of the present invention, in the first aspect of the invention, the diameter of the hollow portion is at least a required light spot diameter necessary for forming an image on the surface to be scanned. Therefore, the diameter of the hollow portion is at least the required light spot diameter required for image formation on the surface to be scanned, so that the required spot diameter can be formed.

According to the third aspect of the present invention, in the first aspect of the present invention, the inner surface of the hollow portion is subjected to a process of absorbing a light beam, thereby preventing a ghost from occurring on an image. A good image can be obtained.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the shape of the light beam entrance or exit of the pyramidal mirror block is a collimator that converts the light beam divergent light emitted from the light source into a parallel light flux. Since it has a lens shape, there is no need to provide a collimator lens, etc.
Cost can be reduced.

According to the fifth aspect of the present invention, in the first aspect of the present invention, the size and shape of the light beam incident on the pyramidal mirror block of the deflector are the same as the size and shape of the reflection surface of the pyramidal mirror block. Since it is set so as to exceed, a required spot diameter can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a light beam scanning device according to the present invention and a deflector applicable to an image forming apparatus using the same.

FIG. 2 is a perspective view showing a part of the deflector.

FIG. 3 is a sectional view showing another light beam scanning device according to the present invention and another deflector applicable to an image forming apparatus using the same.

FIG. 4 is a sectional view showing still another deflector applicable to the light beam scanning device and the image forming apparatus using the same according to the present invention.

FIG. 5 is a cross-sectional view illustrating an image forming apparatus using the light beam scanning device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Deflector 2 Motor 3 Pyramidal mirror block 3a Pyramidal mirror 4 Case 5 Rotation axis 10 Hollow part 35 Light beam scanning device 50 Light beam incidence part 51 Light beam emission part 60 Light beam

 ────────────────────────────────────────────────── ─── Continued on front page F term (reference) 2C362 AA40 BA02 BA07 BA83 BA86 BA90 DA06 DA09 2H045 AA71 CB24 DA02 5C051 AA02 CA06 DA01 DB02 DC04 DC05 DC07 DE09 FA01 5C072 AA03 BA01 DA02 DA04 DA21 HA01 HA12 XA01 XA05

Claims (6)

[Claims] In order to form a light beam on a surface to be scanned with a required spot diameter required for image formation, the light beam is inclined with respect to a reflection surface of a pyramidal mirror block of a deflector with respect to a normal direction thereof. A light beam scanning device for causing the reflected beam to be incident on the imaging lens, wherein the rotating shaft of the deflector has a hollow structure, and the hollow portion serves as an optical path of the light beam toward the imaging lens. Wherein the reflecting surface of the pyramidal mirror block is shaped to shape the beam diameter of the light beam toward the imaging lens in the main scanning direction and the beam diameter in the sub-scanning direction. 2. The light beam scanning apparatus according to claim 1, wherein the diameter of the hollow portion is at least equal to a required light spot diameter required for forming an image on a surface to be scanned. . 3. The light beam scanning device according to claim 1, wherein the inner surface of the hollow portion is subjected to a process of absorbing a light beam. 4. The collimator lens according to claim 1, wherein the light beam incident portion or the light emitting portion of the pyramidal mirror block has a collimator lens shape for converting the divergent light beam emitted from the light source into a parallel light beam. Light beam scanning device. 5. The light according to claim 1, wherein the size of the light beam incident on the pyramidal mirror block of the deflector is set to be larger than the size of the reflection surface of the pyramidal mirror block. Beam scanning device. 6. The light beam scanning device according to claim 1, an imaging lens of the light beam scanning device, and a photoconductor on which a light beam is imaged by the imaging lens and scanned by the light beam. An image forming apparatus comprising: