JP3128975B2 - Optical deflector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical deflector for rotating a rotary polygonal mirror having a plurality of reflecting mirrors formed on its outer periphery, reflecting an incident light beam and deflecting and scanning an image carrier or a recording member.

[0002]

2. Description of the Related Art Generally, an image reading apparatus which scans an image carrier with a light beam emitted from a light source such as a laser to read the image, or scans a recording medium with a light beam modulated by an image signal or a character signal. In an image recording apparatus that records an image using a rotary polygon mirror, a rotating polygon mirror having a large number of reflecting mirror surfaces on its outer periphery is used as a means for scanning the light beam.

[0003] As this kind of optical deflector, there is provided a rotating bearing which is preferably a dynamic pressure air bearing or the like in which one of a sleeve and a shaft to be fitted to each other is a rotating member and the other is a fixed member, and is attached to the rotating member. A so-called drive motor that generates a rotating torque by a magnetic circuit formed by winding an electromagnetic coil around a permanent magnet and an annular core installed on a fixed member, and has a function of a magnetic bearing that holds a rotating body in the axial direction. An optical deflector having a magnetic circuit is known.

FIG. 4 is an explanatory view of a schematic configuration of an image recording apparatus using this type of optical deflector.
Is a collimator lens, 32 is a condensing optical system, 33 is a photosensitive member as a recording medium, 53 is a rotating polygon mirror, 53-1 is a plurality of reflecting mirror surfaces constituting a rotating polygon mirror, and 57 is a rotation drive mechanism (drive motor). Reference numeral 58 denotes a dustproof cover (hereinafter simply referred to as a cover), and 58-1 denotes an opening (input / output window) through which a light beam enters and exits.

In FIG. 1, a rotary polygon mirror 53 is rotated by a drive motor 57 in the direction of arrow A. A light beam emitted from a laser 30 such as a semiconductor laser or a gas laser is modulated by an image signal or the like by a modulator (not shown), and is incident on a reflecting mirror surface 53-1 of the rotary polygon mirror 53. The light beam (reflected light beam) reflected by the reflecting mirror surface 53-1 of the rotating polygon mirror 53 passes through the condensing optical system 32 and is exposed to the photosensitive member 33.
Is projected to

The reflected light beam is deflected in the direction of arrow B with the rotation of the rotary polygon mirror 53 in the direction of arrow A, and
3 is main-scanned. At the same time, the sub-scan is performed by the rotation of the photoconductor 33 in the direction of arrow C, and a two-dimensional image is written on the photoconductor 33. A dust cover 58 having a light beam entrance / exit window 58-1 is attached to prevent dust from adhering to the reflecting mirror surface 53-1 of the rotary polygon mirror 53.

FIG. 5 is a sectional view for explaining the structure of a conventional optical deflector, and FIG. 6 is a sectional view taken along the line A--A of FIG. 5 excluding the housing. Groove, 2 for housing, 3 for rotating sleeve, 3-1 for mirror flange,
4 is a cover, 4-1 is an entrance / exit window, 5 is a magnet yoke, 6 is a magnet, 7 is a stator core, 8 is a stud, 9 is a circuit board, 10 is a magnetic detecting element, 11 is a rotating polygon mirror, and 12 is a cap. Flanges, 13, 17, 18, 2
0 is a screw, 14 is a window glass, 15 is a gap, 16
Is a shaft flange, 19 is a collar, 21 is a balance ring,
22 is an air reservoir, 23 is a reflecting mirror surface, 24 is a toroidal electromagnetic coil, and 25 is a fine hole. This optical deflector is of a fixed shaft type in which a shaft 1 is fixed and a sleeve inserted into the shaft 1 rotates. Here, the shaft 1 will be described as a fixed shaft, and the sleeve 3 will be described as a rotating sleeve.

In FIG. 5 and FIG. 6, one end of the fixed shaft 1 is fixed to a shaft flange 16, and these are fixed to the housing 2 by screws 17. On the peripheral surface of the fixed shaft 1, there is provided a dynamic pressure generating groove 1-1 acting as a radial bearing. This radial bearing is a bearing for preventing the center of rotation from shifting from a predetermined position even when a force acts in a direction perpendicular to the rotating shaft.

The rotor constituting the drive motor has a fixed shaft 1
The rotary sleeve 3 is composed of a rotary sleeve 3, a magnet yoke 5, a magnet 6, and a balance ring 21 fixed to the rotary sleeve 3 by press fitting or bonding. The rotary polygon mirror 11 is attached to this rotor unit. To install the rotating polygon mirror 11, insert the center hole of the polygon mirror 11 into the rotating sleeve 3,
This is performed by applying a cap flange 12 from above and fixing the cap flange 12 to the rotating sleeve 3 with a screw 13. Between the upper end of the fixed shaft 1 and the cap flange 12, an air reservoir 2 for suppressing damping in the thrust direction (axial direction).
2, and a small hole 25 is formed in a part of the cap flange 12 to communicate the air reservoir with the outside.

On the other hand, a stator portion constituting a drive motor includes a housing 2, a fixed shaft 1 having one end fixed to a shaft flange 16 fixed to the housing 2 with screws 17 by press-fitting, and a collar 19 on the housing 2. Screw 2
Stator core 7 fixed by 0 (although not shown, an electromagnetic coil suitable for a toroidal type is wound around stator core 7), stator core 7
The circuit board 9 is supported by studs 8 mounted on the circuit board 9, and the magnetic sensing element 10 is preferably a Hall element planted on the circuit board 9.

The magnet 6 is a permanent magnet, and a magnetic attraction acts between the magnet 6 and the opposing stator core 7.
This attractive force acts to prevent the facing position between the magnet 6 and the stator core 7 from shifting in the axial direction (thrust direction) of the motor. That is, in FIG. 5, when the magnet 6 moves to the right, a component that pulls back to the left appears in the attraction force, and when it moves to the left, a component that pulls back to the right appears and pulls back. Thus, the magnet 6 and the stator core 7 are made to face each other at a predetermined position in the axial direction by the magnetic attraction force. That is, the magnet 6 and the stator core 7 constitute a magnetic thrust bearing.

As the magnetic detecting element 10, for example, a Hall element is used. This detects the leakage magnetic flux of the magnet 6 and detects whether the N pole or the S pole has passed when the magnet 6 rotates. The detection signal of the axis detection element 10 is sent to a control circuit (not shown) through a wiring printed on the circuit board 9. The control circuit determines the direction of the current flowing through the coils wound around the respective portions of the stator core 7 based on the detection signal. As a result, a force in a direction to maintain the rotation is generated by the interaction with the magnet 6.

When the rotary sleeve 3 rotates, a high pressure air layer is generated around the shaft 1 (at the gap 15) by the dynamic pressure generating groove 1-1. With this pressure, a dynamic pressure air bearing in which the rotating sleeve 3 is supported in a state of being floated from the shaft 1 is configured. Note that, in FIG.
Although the groove 1 is provided on the outer periphery of the fixed shaft 1, a groove 1-1 for generating dynamic pressure may be provided on the inner wall of the rotary sleeve 3 instead.

The air layer in the gap 15 acts to keep the center of rotation of the rotor unit constant. For example, if the rotating sleeve 3 is shifted to the left in the figure, the gap in the right gap 15 is large, and the pressure in this gap is smaller than before the gap. On the other hand, since the left gap is small, the pressure in this gap is larger than before the gap. When the magnitude relationship between the pressures is as described above, the rotating sleeve 3 is pushed rightward, and eventually returns to the original position.

FIG. 7 is an explanatory view of the rotary polygon mirror and its deflecting operation, with the upper part of the cover 4 removed. As shown in the figure, the rotating polygon mirror 11 forms a regular polygon when viewed from above in the axial direction, and has a large number of reflecting mirror surfaces 23 on its outer periphery (side surface). In the figure, a light beam such as a laser beam that has entered through a window glass 14 of an entrance window 4-1 is reflected by a reflecting mirror surface 23 of the rotating polygon mirror 11.
And is again reflected by the window glass 14 of the entrance window 4-1.
Exit through.

When the rotating polygon mirror 11 rotates when the light beam enters the reflecting mirror surface at the position of the entrance window 4-1, the reflected light beam of the light beam is gradually changed in direction and deflected. As the rotation progresses and the next reflecting mirror surface rotates, the light beam will now be incident on it. Deflection is also performed on this reflecting mirror surface in the same manner as on the preceding reflecting mirror surface. Therefore, the reflected light beam scans in a certain angle range, and the scanning speed depends on the rotation speed of the rotary polygon mirror 11.

The above-mentioned optical deflector is a fixed shaft type in which the shaft 1 is fixed. However, a rotating shaft type in which a sleeve is fixed to a housing and a rotating shaft is inserted in the sleeve is also known. The prior art relating to this type of optical deflector is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-23 / 1987.
1922.

[0018]

However, in the conventional optical deflector provided with the above-described dynamic pressure air bearing, the shaft and the sleeve come into contact with each other when the rotation is started and stopped, and the bearing portion is worn, so that the life is short. There was a problem. That is, the air pressure in the bearing gap (gap 15) is small at the time of starting and stopping the rotation of the dynamic pressure air bearing, so that the shaft and the sleeve rotate while being in contact with each other. Then, as the rotation speed increases, the pressure in the gap increases and the gap becomes non-contact. Since the pressure in the bearing gap is uniform in the radial direction, when an external force in a specific direction is applied to the radial direction when starting or stopping rotation, the contact time and contact force increase, further promoting bearing wear and extending the life. descend.

Therefore, especially when the bearing is in a position other than the vertical direction (the axial direction is a non- vertical direction), the weight of the rotating body, which is an external force in a specific direction, and the magnetic unbalance force formed by the eccentricity of the magnet and the stator core. Greatly affects the life. For example, when the bearing is in a horizontal position, when the magnetic unbalance force is present vertically below, the force exerted on the bearing contact becomes the largest, being added to the weight of the rotating body.

In such a positional relationship, the life of the bearing becomes the shortest, and the magnetic unbalance force affects only the vector component (vertical component) converted in the direction of gravity even in an unspecified direction that is not vertically downward. Become. An object of the present invention is to solve the above-mentioned problems of the prior art, to reduce the influence of the weight of the rotating body and the magnetic unbalance force when the bearing is not in the vertical position, to reduce the contact force and contact time of the bearing, and to reduce the bearing time. An object of the present invention is to provide an optical deflector with reduced wear and extended life.

[0021]

In order to achieve the above object, the present invention relates to an optical deflector provided with a dynamic pressure air bearing in a bearing of a driving mechanism of a rotating member having a rotating polygon mirror. The force in the direction perpendicular to the axis acting on the rotating member due to the weight of the rotating member that rotates around the axis when other than the vertical posture, and the magnetic unbalance force generated by the eccentricity between the magnet and the stator core Are offset from the central axis XX of the rotating member by Δd in the direction perpendicular to the central axis YY of the stator core.

That is, the present invention provides a hydrodynamic air bearing in which one of the sleeve 3 and the shaft 1 fitted to each other is a rotating member and the other is a fixed member, and a plurality of reflecting mirror surfaces fixed to the rotating member and provided on the outer periphery. And a rotating polygon mirror 11 having a magnet 23, a magnet yoke 5 having a magnet 6 fixed to the rotating member, and a stator core 7 wound with an electromagnetic coil provided on the fixed member. the generating function and the rotating member and a magnetic circuit having both magnetic bearing function of holding in the direction of the shaft 1, the rotating polygonal mirror 11 installed in the axial direction of the dynamic pressure air bearing non vertical direction In the optical deflector that deflects the incident light beam by rotating it by reflecting it on the reflecting mirror surface 23 of the rotating polygon mirror 11, the light deflector rotates around the axis installed in the non-vertical direction.
Acting on the rotating member by the weight of the rotating member.
The force perpendicular to the axis, the magnet and the stator
Only the amount that offsets the magnetic unbalance force generated by eccentricity with
It is characterized in that the center axis of the stator core is eccentric in the direction perpendicular to the axis with respect to the axis 1 .

The present invention is not limited to the fixed shaft type,
It goes without saying that the present invention can also be applied to an optical deflector provided with a rotating shaft type dynamic pressure air bearing in which a rotating shaft is fixed to a rotating shaft inserted into the sleeve as a fixing member. The above-mentioned drive mechanism is a so-called inner rotor type drive mechanism in which a rotating magnet is located on the inner periphery of the stator core, whereas the above-mentioned drive mechanism has a so-called outer rotor type drive mechanism in which the rotating magnet is located on the outer periphery of the stator core. are those applicable to the optical deflector, the rotating portion by the rotation member wt case converted inclination angle of the shaft 1
Force acting on the material in a direction perpendicular to the axis 1 and the
Magnetic eccentricity generated by eccentricity between the gnet and the stator core
Stator core with respect to the shaft 1 by an amount that cancels the balance force
The center axis of the
Thereby, the object of the present invention can be achieved.

[0024]

In the configuration in which the magnet 6 of the present invention is located on the inner periphery of the stator core, when the dynamic pressure air bearing is in a non- vertical posture in a direction other than the vertical direction, the weight of the rotating body in terms of the shaft inclination angle is reduced. The central axis Y-Y of the stator core 7 is set with respect to the central axis XX of the rotating member by an amount that cancels out the magnetic imbalance force generated by the force applied in the direction perpendicular to the axis and the eccentricity of the magnet 6 and the stator core 7. By decentering the rotating shaft vertically downward by Δd, the influence of the rotating weight and the magnetic unbalance force is eliminated, the contact force and the contact time of the bearing are reduced, and the wear of the bearing is reduced.

The magnet 6 is connected to the stator core 7
, The horizontal center axis Y of the stator core 7 with respect to the horizontal center axis XX of the rotating member.
By eccentrically moving -Y vertically upward by Δd corresponding to the amount that offsets the magnetic unbalance force, the influence of the rotating weight and the magnetic unbalance force is eliminated, and the contact force and contact time of the bearing are reduced. As a result, bearing wear is reduced.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view illustrating the structure of an optical deflector according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1 excluding a housing. Groove for pressure generation, 2 for housing, 3 for rotating sleeve, 3
-1 is a mirror flange, 4 is a cover, 4-1 is an input / output window, 5 is a magnetic yoke, 6 is a magnet, 7 is a stator core, 8 is a stud, 9 is a circuit board, 10 is a magnetic detection element, and 11 is a rotation. Polygon mirror, 12 is a cap flange,
13, 17, 18, and 20 are screws, 14 is a window glass, 15 is a gap, 16 is a shaft flange, 19 is a collar, 2
1 is a balance ring, 22 is an air reservoir, 23 is a mirror surface, 24 is a toroidal electromagnetic coil, 25 is a fine hole, X
-X is the horizontal center axis of the rotating member (rotor portion) including the rotary polygon mirror, YY is the horizontal center line of the stator core, and Δd is the vertical direction between the center axis XX and the center axis YY. It is the amount of eccentricity.

Although FIG. 2 shows a case where the magnet is magnetized in two poles, the operation is the same for a magnet having multiple poles. In this optical deflector, the shaft 1 is fixed as in FIG.
The sleeve inserted into the shaft 1 is of a type that rotates. Here, the shaft 1 will be described as a fixed shaft, and the sleeve 3 will be described as a rotating sleeve.

The basic structure and light deflecting operation of the optical deflector shown in FIGS. 1 and 2 are the same as those described with reference to FIGS. 5 and 6, and one end of the fixed shaft 1 is fixed to the shaft flange 16. And they are fixed to the housing 2 by screws 17. A groove 1-1 for generating dynamic pressure acting as a radial bearing is provided on the peripheral surface of the fixed shaft 1, so that even if a force acts in a direction perpendicular to the rotating shaft, the center of rotation does not deviate from a predetermined position. Act like so.

The rotor part constituting the drive motor is a fixed shaft 1
The rotary sleeve 3 is composed of a rotary sleeve 3, a magnet yoke 5, a magnet 6, and a balance ring 21 fixed to the rotary sleeve 3 by press fitting or bonding. To attach the rotary polygon mirror 11 to the rotor, the center hole of the polygon mirror 11 is inserted into the rotary sleeve 3 and the cap flange 1 is inserted from above.
2 and is fixed to the rotating sleeve 3 by screws 13. Between the upper end of the fixed shaft 1 and the cap flange 12, an air reservoir 22 for suppressing damping in the thrust direction (axial direction) is formed, and a part of the cap flange 12 communicates the air reservoir with the outside. Micro holes 25 are provided.

On the other hand, the stator portion constituting the drive motor includes a housing 2, a fixed shaft 1 having one end fixed to a shaft flange 16 fixed to the housing 2 with screws 17 by press fitting, and a collar 19 mounted on the housing 2. Screw 2
0, a stator core 7 (an electromagnetic coil suitable for a toroidal type is wound around the stator core 7), a circuit board 9 supported by studs 8 attached to the stator core 7, and on the circuit board 9. Detecting element 1 which is preferably a Hall element planted and installed
0 and so on.

The magnet 6, which is a permanent magnet, generates a magnetic attractive force between the magnet 6 and the opposed stator core 7. This attractive force acts to prevent the facing position between the magnet 6 and the stator core 7 from shifting in the axial direction (thrust direction) of the motor. In other words, when the magnet 6 moves rightward in the axial direction, a component that pulls back to the left appears in the attraction force, and when it moves leftward, a component that pulls back to the right appears and pulls back. Thus, the magnet 6 and the stator core 7 are made to face each other at a predetermined position in the axial direction by the magnetic attraction force. That is, the magnet 6 and the stator core 7
A magnetic thrust bearing is configured.

As the magnetic detecting element 10, for example, a Hall element is used. This detects the leakage magnetic flux of the 9 magnets 6 and detects whether the N pole or the S pole has passed when the magnet 6 rotates. The detection signal of the axis detection element 10 is sent to a control circuit (not shown) through a wiring printed on the circuit board 9. The control circuit determines the direction of the current flowing through the coils wound around the respective portions of the stator core 7 based on the detection signal. As a result, a force in a direction to maintain the rotation is generated by the interaction with the magnet 6.

When the rotary sleeve 3 rotates, a high pressure air layer is generated around the shaft 1 (at the gap 15) by the dynamic pressure generating groove 1-1. With this pressure, a dynamic pressure air bearing in which the rotating sleeve 3 is supported in a state of being floated from the shaft 1 is configured. Note that, in FIG.
Although the groove 1 is provided on the outer periphery of the fixed shaft 1, a groove 1-1 for generating dynamic pressure may be provided on the inner wall of the rotary sleeve 3 instead.

The air layer in the gap 15 serves to keep the center of rotation of the rotor (rotating member) constant. For example, in FIG.
If the rotating sleeve 3 is shifted to the left in the figure, the gap in the right gap 15 becomes large, and the pressure in the gap in this portion becomes smaller than before the gap. On the other hand, since the left gap is small, the pressure in this gap is larger than before the gap. When the magnitude relationship between the pressures is as described above, the rotating sleeve 3 is pushed rightward, and eventually returns to the original position.

In FIG. 1, one end of the fixed shaft 1 is fixed to a shaft flange 16, and these are fixed to the housing 2 by screws 17. The configuration of the present embodiment differs from the conventional optical deflector in that the stator core 7 is eccentric with respect to the magnet 6 fixed to the rotating sleeve 3 inserted with the fixed shaft 1 as a reference.

That is, the horizontal center axis XX of the rotary member including the rotary polygon mirror is decentered vertically by Δd with respect to the horizontal center line YY of the stator core. The eccentricity Δd is an amount by which the force corresponding to the weight of the rotating member including the rotating polygon mirror 11 and the magnetic unbalance force by the magnet 6 are offset. FIG. 3 is a schematic diagram for explaining the operation and effect of the present embodiment. In the two-pole magnetized rotating torque generating mechanism described with reference to FIGS. Is described by vector display when is decentered in the vertical direction.
In the figure, double characters represent vector components.

In FIG. 3, when the center axis of the stator core 7 is eccentric in the vertical direction D with respect to the center axis of the rotating magnet 6, magnetic attraction is generated only in one direction with respect to the eccentric direction. here,

[0038]

(Equation 1)

Only the width 0 when the stator core 7 is eccentric is 0.
Magnetic energy at ~ π

[0040]

(Equation 2)

The magnetic flux density in the gap between the magnet 6 and the stator core 7 is

[0042]

(Equation 3)

And the magnetic permeability is μ,

[0044]

(Equation 4)

## EQU1 ## And

[0046]

(Equation 5)

Magnetic attraction force when moving only

[0048]

(Equation 6)

Is

[0050]

(Equation 7)

Is as follows. Therefore,

[0052]

(Equation 8)

Magnetic energy at widths π to 2π in the opposite direction decentered only

[0054]

(Equation 9)

Is

[0056]

(Equation 10)

And the magnetic attraction force

[0058]

[Equation 11]

Is

[0060]

(Equation 12)

Is obtained. That is, the difference between the above magnetic attraction forces

[0062]

(Equation 13)

Will occur. When the number of magnetic poles is large, the magnetic flux density in the air gap

[0064]

[Equation 14]

May be integrated over each magnetic pole. As described above, when the bearing is in a position other than the vertical position (non-vertical position), the magnetic unbalance generated by the eccentricity between the magnet 6 and the stator core 7 and the force corresponding to the shaft tilt angle in the vertical direction of the rotating member weight. Eccentricity of the center axis of the stator core 7 in the vertical direction with respect to the center axis of the rotating member by an amount that cancels the force reduces the influence of the weight of the rotating body and the magnetic unbalance force, thereby reducing the contact force and contact time of the bearing. Bearing wear can be reduced.

The amount of eccentricity is from several μm to several hundred μm. In the embodiment, the number of magnet poles has been described as 2. However, the same applies to a multipole having two or more poles.

[0067]

As described above, according to the present invention,
When the dynamic pressure air bearing is in a position other than the vertical position, the force generated in the direction perpendicular to the shaft acting on the rotating member due to the weight of the rotating member rotating around the axis, and the magnetic force generated by the eccentricity between the magnet and the stator core The influence of the weight of the rotating body and the magnetic unbalance force is reduced by offsetting the center axis of the stator core vertically downward with respect to the axis by an amount that cancels the unbalance force and vertically upward in the case of the outer rotor type. It is possible to provide an optical deflector that reduces the contact force and the contact time of the bearing, reduces the wear of the bearing, and greatly extends the life.

[Brief description of the drawings]

FIG. 1 is a sectional view illustrating the structure of an optical deflector according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the optical deflector according to the embodiment of the present invention, taken along the line AA in FIG.

FIG. 3 is a schematic diagram illustrating the operation and effect of an embodiment of the optical deflector according to the present invention.

FIG. 4 is an explanatory diagram of a schematic configuration of an image recording apparatus using an optical deflector.

FIG. 5 is a cross-sectional view illustrating the structure of a conventional optical deflector.

FIG. 6 is a cross-sectional view of the conventional optical deflector, taken along the line AA in FIG. 5, excluding the housing of FIG. 5;

FIG. 7 is an explanatory view of a rotary polygon mirror and its deflection operation.

[Explanation of symbols]

1 ··· Fixed shaft 1-1 ··· Groove for generating dynamic pressure 2 ·
... Housing 3 ... Rotating sleeve 3-1
... Mirror flange 4 ... Cover 4-1 ...
..Incoming / outgoing window 5 ... Magnet yoke 6 ...
· Magnet 7 · · · Stator core 8 · · · Stud 9 · · · Circuit board 10 · · · Magnetic detection element 11 · · · Rotating polygon mirror 12 · · · Cap flanges 13, 17, 18, 20 ... screw 14 ...
・ Window glass 15 ・ ・ ・ ・ Gap 16 ・ ・ ・ ・
Shaft flange 19 ··· Collar 21 ··· Balance ring 22 ··· Air pool 23 ··· Reflecting mirror surface 24 ··· Toroidal electromagnetic coil 25 ···
··· Micro holes XX ···· Horizontal center axis of rotating member (rotor portion) including rotating polygon mirror YY ··· Horizontal center line of stator core Δd ··· Center axis X −
The amount of eccentricity in the vertical direction between X and the central axis YY.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 26/10 102 F16C 17/00 H02K 21/00

Claims (1)

(57) [Claims] 1. A hydrodynamic air bearing in which one of a sleeve and a shaft inserted into one another is a rotating member and the other is a fixed member, and a rotating polygon mirror fixed to the rotating member and having a plurality of reflecting mirror surfaces formed on an outer periphery thereof. And a magnet yoke having a magnet and fixed to the rotating member, and a rotating torque generating function constituted by a stator core wound with an electromagnetic coil provided on the fixing member, and the rotating member is moved in the axial direction of the shaft. A magnetic circuit having a function of holding a magnetic bearing, and by setting the axial direction of the dynamic pressure air bearing in a non- vertical direction and rotating the rotary polygon mirror, the incident light beam is rotated by the rotary polygon. In an optical deflector that deflects light by reflecting it on a reflecting mirror surface of a mirror, the rotation that rotates around the axis installed in a non-vertical direction
Perpendicular to the axis acting on the rotating member due to the weight of the member
Direction force and eccentricity between the magnet and the stator core
Of the shaft by an amount that cancels out the magnetic unbalance force generated by
An optical deflector characterized in that the center axis of the stator core is decentered in a direction perpendicular to the axis .