JP2002350767A - Rotary polygon mirror and light deflecting and scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record a high-quality image by removing stray light being the main cause of the deterioration of the image. SOLUTION: In the rotary polygon mirror where a prism part having mirror surface parts on its side surface and a circular cylinder part having the columnar shape of an attaching part to a driving means are integrally constituted in an axially aligned state, the outer peripheral surface of the circular cylinder part is inclined to the perpendicular direction of an attaching reference surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light deflection scanning device used in a laser beam printer, a laser facsimile, and the like, and a rotary polygon mirror used in the device.

[0002]

FIG. 6 shows a light deflecting device of a conventional laser beam printer. A rotating shaft 1 is rotatably fixed to a housing 3 via a bearing unit 2, and a pedestal 4 is provided above the rotating shaft. A rotating polygon mirror 5 serving as a deflector is pressurized by a spring 6 and fixed by a stopper 7 on the upper part of the pedestal 4, and a driving magnet 8 is provided on the inner periphery of the lower part of the pedestal 4. A yoke 9 fixed to the surface side is fixed. A coil 10 fixed to the upper part of the housing 3 is provided at a position facing the driving magnet 8. The light deflecting device fixes the housing portion to the hole of the circuit board by press fitting or the like.

In a scanning optical device used in a laser beam printer, a laser facsimile, etc.,
The rotation of the rotary polygon mirror 5 causes main scanning of the photosensitive member with a light beam, and sub-scanning is performed by rotating the photosensitive member around the axis of the cylinder. Thus, an electrostatic latent image is formed on the surface of the photoconductor. The electrostatic latent image is visualized into a toner image by a developing device, the toner image is transferred to a recording sheet, and then the toner is heated and fixed to the recording sheet after the transfer of the toner image by a fixing device. Printing is performed.

FIG. 7 is a plan view illustrating the configuration of a conventional scanning optical device used in a laser beam printer to scan a photosensitive member with a light beam.

[0005] The scanning optical device is a scanner body (optical box) 4.
0 is shown in FIG. 7, and a top view of which is shown in FIG. The scanning optical device forms a laser beam unit 20 by integrating a semiconductor laser 11, a collimator lens 12 for converting a light beam generated from the semiconductor laser into a parallel light beam, and integrating the semiconductor laser 11 and the collimator lens by a lens barrel 13. A cylindrical lens 14 for converging the parallel light beam from the laser beam unit 20 linearly in the sub-scanning direction, and a deflecting / reflecting surface 51 near a line image of the light beam condensed by the cylindrical lens 14
The rotary polygon mirror 5 having a, f, which is designed to form a spot on the photosensitive member with the deflected light beam and scan at a constant speed.
It is configured to include the θ lens 30 and the like. Deflection reflective surface 5
The light beam deflected and reflected in 1a enters the reflecting mirror 17 via the fθ lens 30, is reflected by the reflecting mirror 17, and irradiates the photosensitive member.

The fθ lens 30 is designed so that the light beam reflected by the deflecting / reflecting surface 51a is condensed so as to form a spot on the photoreceptor, and the scanning speed of the spot is constant. In order to obtain such fθ characteristics, the fθ lens 30 is connected to the first lens 15 and the second lens 15.
The lens 16 includes two lenses.

Conventionally, as shown in FIG. 4, a rotary polygon mirror 5 of this kind has a polygonal column portion 51 whose side surface is mirror-finished and an inscribed circle of a polygon on the bottom surface of the polygonal column. ,
The cylindrical portion 52, which is about a fraction of the height of the polygonal column, is processed as an integral structure from a metal material such as aluminum, and the outer peripheral surface 52a of the cylindrical portion 52 is not as large as the side surface 51a of the central polygonal portion 51. Anyway, it has high reflectance.

A reference surface 52b for attaching the rotary polygon mirror 5 to the pedestal 4 is located on the bottom surface of the cylindrical portion 52, and is mirror-finished so that there is no floating at the time of attachment and the coaxiality is high so as to ensure flatness. .

In an optical deflection scanning device using the rotary polygon mirror 5, the parallel light emitted from the laser beam unit 20 is converted to the deflection reflection surface of the rotary polygon mirror 5 in order to reduce the influence of the plurality of deflection reflection surfaces 51a. The cylindrical lens 14 is used so as to connect a focal line near 51a.

For this reason, the deflection reflecting surface 51a of the rotary polygon mirror 5
In the above, the portion used in the vertical direction is a part of the height of the rotary polygon mirror 5.

However, as the number of surfaces increases and the diameter of the rotary polygon mirror 5 increases, the mounting reference surface 52b also increases, so that the rotary polygon mirror 5 and its processing surface are not deformed during processing. Rigidity is required. That is, the height of the rotary polygon mirror 5 itself is required. Further, in order to prevent deformation of the reflecting surface due to an increase in centrifugal force due to an increase in the number of rotations of the motor in recent years, it is necessary to increase rigidity, that is, the height of the rotary polygon mirror 5 is required. Therefore, it is not practical to reduce the thickness of the rotary polygon mirror 5 to the beam diameter in the sub-scanning direction from a practical viewpoint.

However, when the thickness of the rotary polygon mirror 5 is increased, there is a problem that the wind noise increases and the speed decreases due to air resistance. There was also a problem that it was desired to reduce the inertia.

As means for solving these problems, Japanese Patent Laid-Open No.
As described in JP-A-289012, the height of the rotary polygon mirror 5 is not changed, and conical tapered surfaces are formed on the upper and lower peripheral portions of the deflecting reflecting surface 51a.
Has been proposed in which only the height of the rotary polygon mirror 5 is made smaller than the thickness of the rotary polygon mirror 5 itself.

[0014]

However, as shown in FIG. 3, the main beam L from the laser beam unit (not shown) enters and reflects substantially perpendicularly to the deflecting / reflecting surface 51a of the rotary polygon mirror 5, and is driven by driving means (not shown). B from A direction
While scanning in the direction, the laser beam unit 20 may generate stray light L ′ due to various factors such as internal reflection. The intensity of the stray light L 'is weaker than that of the main beam L, and its traveling direction is almost the same as that of the main beam L, but is not accurately determined.

For this reason, there is a case where the stray light L 'is directed toward the cylindrical portion 52 located below the polygonal column portion 51 of the rotary polygon mirror 5, and a conical taper surface is formed particularly on the upper and lower peripheral portions of the deflecting / reflecting surface 51a. In this case, the stray light L 'easily reaches the cylindrical portion outer peripheral surface 52a.

The stray light incident on the outer peripheral surface 52a of the cylindrical portion is reflected in a certain direction C. Therefore, even if the intensity of the stray light L 'is weaker than that of the main beam L and the reflectivity of the outer peripheral surface 52a of the cylindrical portion is inferior to that of the polygon mirror reflecting surface 51a, the stray light L' is transmitted through the f.theta. , The stray light L ′ keeps resting on the photoreceptor, so that an electrostatic latent image is always formed at a certain point on the photoreceptor. There was a problem that the quality deteriorated.

An object of the present invention is to solve the above problems and to provide a rotary polygon mirror and an optical deflection scanning device capable of recording a high quality image.

[0018]

In order to achieve the above object, the rotary polygon mirror of the present invention has an installation surface which rotates together with the rotation axis, coincides with the rotation axis of the drive motor, and is perpendicular to the rotation axis. A rotating polygon mirror having a unitary structure including a cylindrical portion having a bottom surface processed to be horizontally mounted on a pedestal and a polygonal column portion having a plurality of mirror surfaces for deflecting a light beam to an outer periphery immediately above the cylindrical portion; The outer peripheral surface that is in contact with the bottom surface of the portion is inclined with respect to the vertical direction of the bottom surface. Here, the outer peripheral surface is desirably a conical surface.

According to another aspect of the present invention, there is provided an optical deflection scanning apparatus comprising: a rotary polygon mirror for deflecting and scanning a light beam; and a drive motor for rotating the rotary polygon mirror.

As described above, the rotary polygon mirror 5 according to the present invention is used.
Is a mounting reference surface 5 for mounting a cylindrical portion 52 integrally formed with a polygonal column portion 51 to a pedestal 4 which rotates together with the rotation axis 1 of the optical deflector.
The outer peripheral surface 52a in contact with 2b is inclined α with respect to the vertical direction.
It is characterized by having attached.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the shape of a rotary polygon mirror 5 of the present invention, and FIG. 4 shows the shape of a general rotary polygon mirror conventionally used for comparison.

FIG. 2 is a diagram for explaining the operation. The main beam L emitted from a laser beam unit (not shown) enters and reflects substantially perpendicularly to the deflecting / reflecting surface 51a of the rotary polygon mirror 5.
Scan over the photoreceptor. Here, the laser beam unit 20
When the stray light is generated in the above case, the stray light L 'may be incident on the cylindrical outer peripheral surface 52a in the downward direction of the deflection reflecting surface 51a of the rotary polygon mirror 5. In this case, since the outer peripheral surface 52a of the cylindrical portion has an inclination α with respect to the vertical direction of the mounting reference surface 52b, the stray light L ′ does not enter and reflect substantially perpendicularly to the outer peripheral surface 52a. For this reason, the stray light L 'is generated by the main beam L on the outer peripheral surface 52a.
The light is reflected in a direction different from that of the photoreceptor, enters a harmless area deviating from the photoreceptor, and only the main beam L is incident on the photoreceptor.

As described above, in the embodiment, since the outer peripheral surface 52a of the cylindrical portion below the rotary polygon mirror 5 is formed as a conical surface, even if stray light L 'exists, the cylindrical column in the downward direction of the deflecting / reflecting surface 51a of the rotary polygon mirror. The stray light L ′ incident on the outer peripheral surface 52b can be reflected in a direction largely different from that of the main beam. Therefore, a high-quality image can be recorded without generating an unnecessary image such as a vertical stripe on the photoconductor.

In this embodiment, the cylindrical outer peripheral surface 52a at the lower part of the rotary polygon mirror is a conical surface having an apex below.
It may be a conical surface having a vertex at the top. If the shape is such that the stray light L ′ can be reflected in a direction largely different from that of the main beam L, the outer peripheral surface 52a of the cylindrical portion below the rotary polygon mirror can be used.
Need not be limited to a conical shape.

[0025]

As described above, in the rotary polygon mirror 5 according to the present invention, the outer peripheral surface 52a of the cylindrical portion 52 below the deflecting / reflecting surface 51a of the rotary polygon mirror 5 is perpendicular to the mounting reference surface 52b. The stray light L ′ incident on the cylindrical portion 52 is reflected by the deflection reflecting surface 51 of the rotating polygon mirror.
Since the stray light L ′, which is a cause of image deterioration, does not reach the photoconductor, a high-quality image can be formed without causing vertical streaks or the like in the image. A scanning optical device capable of recording can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a rotary polygon mirror according to an embodiment of the present invention.

FIG. 2 is an operation explanatory view of an optical deflection scanning device using a rotary polygon mirror of the present invention.

FIG. 3 shows a main beam L when a conventional rotary polygon mirror is used.
FIG. 4 is an explanatory diagram of an optical path of stray light L ′.

FIG. 4 is a diagram illustrating a configuration of an example of a conventional rotary polygon mirror.

FIG. 5 is an operation explanatory view of a conventional light deflection scanning device using a rotary polygon mirror.

FIG. 6 is a diagram illustrating the configuration of a conventional scanning optical device using a rotating polygon mirror.

FIG. 7 is a diagram illustrating a configuration of a scanning optical device using a conventional rotating polygon mirror.

[Explanation of symbols]

 5 Rotating Polygonal Mirror 51 Rotating Polygonal Mirror Polygonal Column 52 52 Rotating Polygonal Mirror Cylindrical 51a Rotating Polygonal Mirror Deflection / Reflection Surface 52a Rotating Polygonal Mirror Cylindrical Column Outer Surface 52b Rotating Polygonal Mirror Mounting Reference Surface L Main Beam L 'Stray Light α Slope

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeru Kurosawa 1248 Shimokage Mori, Chichibu City, Saitama Prefecture Inside Canon Electronics Co., Ltd. Term (reference) 2C362 BA05 2H042 DD03 2H045 AA03 CB63

Claims (3)

[Claims] 1. A cylindrical portion having a bottom surface processed for horizontal mounting on a pedestal which rotates together with a rotating shaft, has a mounting surface coinciding with the rotating shaft of the drive motor and has a mounting surface perpendicular to the rotating shaft, and a cylindrical portion directly above the cylindrical portion. In a rotary polygonal mirror in which a polygonal prism portion having a plurality of mirror surfaces for deflecting a light beam on the outer periphery has an integral structure, an outer peripheral surface in contact with a bottom surface of the cylindrical portion has an inclination with respect to a vertical direction of the bottom surface. A rotating polygon mirror characterized by being attached. 2. The rotary polygon mirror according to claim 1, wherein said outer peripheral surface is a conical surface. 3. The method according to claim 1, wherein the light beam is deflected and scanned.
An optical deflection scanning device comprising: the rotary polygon mirror according to claim 1; and a drive motor configured to rotate the rotary polygon mirror.