JPH07270703A - Optical device - Google Patents

Abstract

PURPOSE:To provide a maser exposure optical device for an image forming device which is rotatable at a high-speed and is capable of providing high resolu tion images. CONSTITUTION:This optical device has an optical deflector having a deflecting reflection mirror 33 held on a supporting member 33a having a diameter Rmin satisfying the equation where the sectional diameter in the main scanning direction on respective reflection surfaces 33i to 33n is defined as (a), the radius of a circumcircle 33c circumscribing a regular polygon regulated by the respective reflection surfaces as R, the min. value of the radius of this circumcircle as Rmin, the number of the reflection surfaces as N, the angle formed by the non-effective region at the ends of the respective reflection surfaces and the connecting points of the respective reflection surfaces to each other as alpha, the incident angle when light is made incident on the centers of the respective reflection surfaces as thetai and the effective rotating angle of the respective reflection surfaces as theta, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device for recording image information on a photoconductor, which is applicable to an image forming apparatus for forming an image on the photoconductor by an electrostatographic process.

[0002]

2. Description of the Related Art An image forming apparatus such as a laser beam printer uses an optical apparatus such as a laser exposure apparatus for providing image information to be recorded on a photosensitive member. The latent image formed on the photoconductor by the laser exposure device, that is, the optical scanning device is developed by the toner supplied from the developing device and then output on the recording paper.

A laser exposure apparatus is a laser device for generating a laser beam, a deflecting device for reflecting or deflecting the laser beam generated by the laser device toward a photosensitive member, and
It is composed of an fθ lens (imaging lens) for focusing the laser beam deflected by the deflecting device on a predetermined position of the photoconductor.

The deflecting device has a rotatable reflecting surface and a motor for rotating the reflecting surface.
One or more (generally 2, 4 or 6) are arranged along the axis of the shaft on the end surface of the thin plate-shaped support extending in the direction orthogonal to the motor shaft,
The incident laser light is reflected or deflected according to the rotation of the motor. If there are two or more reflecting surfaces, it is generally called a polygon mirror.

By the way, the size of the reflecting surface, that is, the polygon mirror, is the beam diameter of the laser beam in the main scanning direction, the effective swing angle (also called the effective rotation angle or deflection angle) of the polygon mirror, and each reflecting surface reflects the laser light. In this case, the maximum rotation angle at which the laser light can be reflected in the image area), the number of reflecting surfaces (the number of surfaces), the ineffective area of each reflecting surface, the incident angle of the incident laser light, etc. are specified.

In many cases, however, the size of the polygon mirror is dependent on the parameters associated with other optical elements, such as the distance between the laser element and the deflector, the distance between the laser element and the deflector. Number of lenses of the light source side lens group and condensing characteristics, distance between the deflecting device and the image forming position (image surface), image side lens group (imaging lens) arranged between the deflecting device and the image surface The number of lenses and the fθ characteristic of the lens, and the number and length of the folding mirrors arranged between the deflecting device and the image plane are determined in a state of being restricted.

[0007]

As described above, the size of the reflecting mirror, that is, the polygonal mirror, is determined by many restrictions as compared with other optical elements. However,
Along with the demand for higher speeds and higher resolutions of image forming apparatuses, deflection devices are also required to increase the number of scanning lines and higher speeds.

This requires the deflecting device to rotate the polygon mirror at high speed and increase the number of reflecting surfaces. However, increasing the number of reflecting surfaces has a problem of reducing the effective swing angle. Further, when the effective swing angle is reduced, there is a problem that the size of the image forming apparatus is increased because the width of an image that can be provided by one deflection operation is limited. Further, when the number of rotations of the polygon mirror is increased, there is a new problem such as an increase in noise with the upper limit of the number of rotations and an increase in the number of rotations. An object of the present invention is to provide a laser exposure optical device for an image forming apparatus which can rotate at high speed and can provide a high-definition image.

[0009]

The present invention has been made based on the above-mentioned problems, and a plurality of reflecting surfaces and each of the plurality of reflecting surfaces are guided by the number of the reflecting surfaces and the reflecting surfaces. A cross-sectional diameter of light, an effective reflection area of the reflection surface, and a support member provided on the circumference of a circle defined based on the angle at which the light is incident, and guides to each reflection surface. (EN) An optical device having a deflecting means for deflecting the reflected light in a predetermined direction and an image forming means for forming an image of the light deflected by the deflecting means at a predetermined position of an object.

Further, according to the present invention, the light source, the light source side optical means for giving a predetermined characteristic to the cross-sectional shape of the light from the light source, the plurality of reflecting surfaces, and the plurality of reflecting surfaces are respectively provided. And a supporting member formed on the circumference of a circle defined according to the number of reflecting surfaces, and directing the light passing through the light source side optical means guided by the reflecting surfaces toward the object. Deflection means for deflecting, and imaging means for forming an image of the light deflected by the deflection means on a predetermined position of the object,
The cross-sectional diameter of the light in the main scanning direction on each of the reflecting surfaces is defined as a [m
m], the radius of the circumscribed circle circumscribing the regular polygon defined by the reflective surface is R [mm], the minimum value of the radius of the circumscribed circle is R min [mm], the number of the reflective surfaces is N, and The angle between the ineffective region at the end of each reflecting surface and the connection point between the reflecting surfaces is α [rad], and the incident angle when the light is incident on the center of each reflecting surface is θi [rad]. ,and,
When the effective rotation angle of each reflection surface is represented by θ [rad], respectively,

[0011]

[Equation 3] There is provided an optical device including deflection means, characterized in that

Further, according to the present invention, the light source, the light source side optical means for giving a predetermined characteristic to the cross-sectional shape of the light from the light source, the plurality of reflecting surfaces, and the plurality of reflecting surfaces are respectively provided. A supporting member for holding on the circumference of a circle defined according to the number of reflecting surfaces, and deflecting the light passing through the light source side optical means guided by each reflecting surface toward an object. A deflection means and an image formation means for forming an image of the light deflected by the deflection means on a predetermined position of the object,
The cross-sectional diameter of the light in the main scanning direction on each of the reflecting surfaces is defined as a [m
m], the radius of the circumscribed circle circumscribing the regular polygon defined by the reflective surface is R [mm], the minimum value of the radius of the circumscribed circle is R min [mm], the number of the reflective surfaces is N, and The angle between the ineffective region at the end of each reflecting surface and the connection point between the reflecting surfaces is α [rad], and the incident angle when the light is incident on the center of each reflecting surface is θi [rad]. , The effective rotation angle of each reflection surface is θ [rad], and the margin ratio in consideration of the change of the cross-sectional diameter of the light is t, respectively,

[0013]

[Equation 4] And R = R min · t, 1 ≤ t ≤ 1.
There is provided an optical device including deflecting means, characterized in that

[0014]

The optical device of the present invention defines a plurality of reflecting surfaces, each of the plurality of reflecting surfaces based on the number of reflecting surfaces, the cross-sectional diameter of light guided to the reflecting surfaces, and the effective reflecting area of the reflecting surface. A deflection member having a supporting member to be held on the circumference of a circle, and the size of the supporting member is not limited by the arrangement and size of other optical elements included in the optical device. The cross-sectional diameter of the light guided to the reflecting surface, the incident angle of the light on each reflecting surface, and the number of reflecting surfaces are easily defined as variables. That is, there is provided a deflecting unit capable of high-speed rotation capable of handling high speed and high definition without changing the cross-sectional diameter of light on an object.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a laser beam printer device incorporating an optical device according to an embodiment of the present invention.

A laser beam printer apparatus (image forming apparatus) 2 includes a data processing section 4 having a control section 6 and a data storage section 8 formed therein, and a scanning exposure unit (optical apparatus) for a laser beam L corresponding to image data. 10, an image forming unit (image forming means) 50 for forming an image (latent image) corresponding to the laser beam L from the scanning exposure unit 10,
It also includes first and second sheet cassettes 61a and 61b for storing recording sheets.

The laser beam printer 2 is warmed up to a standby state in which an image can be formed based on image data by turning on a main switch (not shown). Image data supplied from an external device such as a word processor or a host computer is sequentially stored in an image memory (data storage unit) 8.

The image data input to the image memory 8 is
After being converted into parallel data and further converted into serial data, the timing is adjusted through the control unit 6 and the data is supplied to the scanning exposure unit 10.

By inputting the image data, the photosensitive drum 51 of the image forming unit 50 is rotated at a desired rotation speed, and a desired electric potential is applied via the charging device 52. At the same time, a paper cassette 61a or 61 that contains a paper P of a size that allows an image based on the image data to be printed out.
b or the bypass feeder 68 is selected, and the paper P stored in the selected cassette or bypass is
Paper feed roller 62a corresponding to each cassette or
The sheet is taken out through 62b and conveyed to the aligning roller 67 through the conveying roller 64 (63) and the paper guide 66 (65).

The image data converted into serial data is supplied to the scanning type exposure unit 10 in accordance with a vertical synchronizing signal from a vertical synchronizing control circuit (not shown), and the semiconductor laser is supplied.
The intensity of the laser beam L generated from 21 is continuously changed according to the image data. The laser beam L whose intensity is continuously changed according to the image data is the photosensitive drum 51.
After that, it is transmitted and converted into an electrostatic latent image. The image converted into a latent image by the photosensitive drum 51 is the photosensitive drum 51.
Is moved to a developing area facing the developing device (developing means) 53, and toner is supplied through the developing device 53 to develop. The developed image is further transported as the photosensitive drum 51 rotates, and is transported to a transfer area facing the transfer device 54.

In the paper P temporarily stopped by the aligning roller 67, the leading edge of the image and the leading edge of the paper P are aligned according to a vertical synchronizing signal from a vertical synchronizing circuit (not shown),
It is fed toward the photoconductor drum 51. Therefore, the toner image on the photoconductor drum 51 and the sheet P are charged by the charge remaining on the photoconductor drum 51 at a predetermined timing.
Adsorbed (adhered) to 51. After that, charges having the same polarity as the charges already applied to the photoconductor drum 51 (for forming a latent image) are transferred to the photoconductor drum 51 and the paper P.
The toner image on the photosensitive drum 51 is transferred onto the paper P from the photosensitive drum 51.

The sheet P on which the toner image is placed is guided to the fixing device 57, where the heat-melting toner is melted and the toner image is fixed (fixed) to the sheet P. On the other hand, the photoconductor drum 51 from which the paper P and the toner image are separated is further rotated,
By the cleaning device 55 and the static eliminator 56, the charge distribution on the surface is returned to the initial state and used for the next image formation.

The paper P on which the image data is output by the above-described series of image forming processes is discharged to the outside of the apparatus 2 by the discharge roller 69. At this time, the sheet P is discharged to the first or second discharge section 71 or 74 by the operation of the switching gate 70 by the control section 6. The front and back of the paper P that is directed to the second discharge unit 74 is reversed by the transport path 72 and the discharge roller 73.

FIG. 2 shows in detail an optical device, ie, a scanning type exposure unit, which is an embodiment of the present invention.
The scanning exposure unit 10 includes a semiconductor laser device (light source) 21
And a laser beam L from the light emitting unit 20 for generating a laser beam L and an image forming unit.
A light deflecting device 30 that reflects or deflects 50 toward the photosensitive drum 51, a light emitting unit 20, a light deflecting device (deflecting means) 30, a housing 11 that holds many optical members described later, and the like. .

The light emitting unit 20 emits the laser beam L emitted from the semiconductor laser element (light source) 21 to the first lens 22.
The light is converted into focused light or parallel light by means of the diaphragm 24, and is limited to a predetermined beam spot by the diaphragm 24. The beam L shaped into a desired beam spot by the diaphragm 24 is a light deflector.
A cylindrical lens (second lens) 23 having a positive power in the direction in which the reflecting mirror (polyhedral mirror) 33 of 30 is rotated, that is, in the sub-scanning direction (equal to the rotation direction of the photoconductor drum 51) orthogonal to the main scanning direction. Through the reflecting mirror 33 of the light deflector 30.
Be led to. The first lens 22 and the second lens 23
Are each made of optical glass (eg BK7). Further, the laser beam L that has passed through the second lens 23 is reflected by a first mirror (not shown) arranged at a predetermined position of the housing 11, and is reflected by a first shield glass (for example, soda lime glass or The optical plate glass passes through a glass 29 colored with a dye such as Blue Pane (trade name) and is guided to a reflecting mirror 33.

The first lens 22, the second lens 23 and the diaphragm 24
Is, for example, aluminum die casting or plastic
It is held together with the semiconductor laser 21 by a lens barrel or a lens holder 25 manufactured by PPS or the like. The semiconductor laser 21 may be directly arranged in the lens barrel (or lens holder) 25, but may be fixed to the lens holder 25 via the laser holder 16 formed separately from the lens barrel. Further, the lens barrel 25 is formed with a positioning member (not shown) for fixing to the housing 11, and is fixed by, for example, a screw or an adhesive.

The optical deflecting device 30 is a polygonal mirror having a plurality of plane mirrors (reflecting surfaces) fixed to a rotating shaft 31a of a scanner motor 31 using a magnetic fluid bearing and rotatably at a high speed, that is, a deflecting reflecting mirror. It is composed of 33. The reflecting surfaces are arranged so as to surround the polygon mirror body, that is, the periphery of the support 33a.

More specifically, the deflective reflecting mirror 33 is placed or positioned on the rotor 32 of the motor 31, and then the shaft 31 is fixed by a spring material, a screw or an adhesive agent not shown.
It is fixed to a. Note that the direction in which the laser beam L is reflected as the deflecting / reflecting mirror 33 is rotated is the main scanning direction. Further, as the scanner motor 31, an axial gap type motor, a radial type motor using a dynamic pressure bearing, a motor using a direct bearing, or the like can be used.

Around the deflection reflector 33 of the housing 11, that is, the light deflection device 30, a light deflection device sound insulation wall 34 for preventing noise generated from the deflection reflection mirror 33 from leaking to the outside is integrally formed with the housing 11. ing. Also housing
11, the light deflector sound insulation wall 34, the first shielding glass 29, and the second shielding glass 41 are sealed by a cover 19 provided in a direction orthogonal to the axial direction of the motor 31.

The laser beam L reflected or deflected by the deflecting / reflecting surface 33 is the second shielding glass 41 and the third lens.
42, second mirror 43, fourth lens 44, third (outgoing) mirror
After passing through or being reflected by 45 and the third shielding glass 46, they are guided to the photosensitive drum 51 of the image forming unit 50. The third shielding glass 46 is used for dust prevention for preventing toner or paper dust from entering the inside of the optical device 10. In addition, the second mirror 43, the third
(Exit) The mirror 45 and the third shielding glass 46 are the prior application by the development group including the inventor of the present application, Japanese Patent Application No. 4-1.
Housing 11 by the method shown in No. 7028, etc.
On the other hand, it is fixed by adhesion. The third lens 42 and the fourth lens 44 respectively correct the distortion and field curvature of the laser beam L imaged on the photosensitive drum 51.

The second mirror 42, the fourth lens 44, and the third mirror 45 are pressed against the fixed guides 14, 15 and 16 formed integrally with the housing 11 from a predetermined direction, respectively. It is fixed by a fixing spring or the like (not shown). The third lens 42 and the fourth lens 44 are made of the same plastic material (for example, PMMA =
Manufactured by polymethylmethacryl). The optical axes O ₂ of the lenses 42 and 44 are arranged in the same plane as the optical axis O ₁ extending from the light emitting unit 20 to the light deflector 30.

The third and fourth lenses 42 and 44 are the rotation angles θ of the respective reflecting surfaces of the deflective reflecting mirror 33 in the main scanning direction.
And the image height h on the photoconductor drum 51, that is, the distance in the main scanning direction between the position where the photoconductor drum 51 and the optical axis O ₂ intersect and the position where the laser beam L arrives. For the focal length f between the 33 and the photoconductor drum 51, "h
= Fθ ”. Further, the third and fourth lenses 42 and 44 in the state of being combined with each other reduce the influence of the field curvature of the laser beam L reflected from the deflection mirror 33 in the main scanning direction, and also cause distortion aberration. Is set to an appropriate value, and in the sub-scanning direction, the laser beam L is formed so as to match the surface tilt correction surfaces on all the surfaces of the photosensitive drum 51.

FIG. 4 shows the relationship between the support 33a of the deflecting / reflecting mirror 33 of the optical deflecting device 30 and each reflecting surface. Referring to FIG. 4, the respective reflecting surfaces arranged on the support 33a of the deflecting reflecting mirror 33 are respectively 33i, 33j (not shown) ,.
Considering the polygon mirrors indicated by 33 n-2 (not shown), 33 n-1 and 33 n, the end portion of each reflecting surface, that is, the non-effective area is also a flat surface provided by extending. It can be seen that it is inscribed in the circumscribed circle 33c defined by the regular polygon corresponding to the number of. The radius of the circumscribed circle 33c is R [m
m = millimeter].

Here, the position where the ends of the reflecting surfaces are connected to each other, that is, the vertex of the regular polygon is j, and the end of the effective portion of each reflecting surface separated from the vertex j by a predetermined distance is k. j
Assuming that the angle between the effective portion end k and α is [rad = radian], the ineffective area at the connecting portion between the reflecting surfaces is
It is indicated by 2α. When the laser beam L is incident on the center of each reflecting surface, the incident angle is θi [rad], the effective rotation angle of each reflecting surface is θ [rad], and when the laser beam L is incident on each reflecting surface. If the beam diameter of is [mm],

[0035]

[Equation 5]

(T is a margin for the error in the optical characteristics of the entire optical device including the assembly error). here,
When formula (1) is rearranged for the circumscribed circle radius R,

[0037]

[Equation 6] Is guided. From this equation (2), the minimum value R of the circumscribed circle radius R
min [mm] is

[0038]

[Equation 7] Indicated by.

As described in the equation (1), the constant t
Is a margin ratio with respect to the variation of the beam diameter of the laser beam L guided to each reflection surface of the deflecting mirror 33 of the optical deflector 30, and is a mounting error between the laser element 21 and the light emitting unit 20, a light emitting unit. This is a case where the beam diameter of the laser beam L emitted from the laser element 21 changes due to at least one of the mounting error between the 20 and the housing 11 and the mounting error between the optical deflector 30 and the housing 11. However, it is a value that is defined so as to ensure the light intensity of the laser beam L guided to the image surface, that is, the photoconductor 51, and, for example, 1 ≤ t ≤ based on the tolerance of each component.
It is specified in 1.15. Here, k = 1 indicates the beam diameter defined by the diaphragm 24 in the light emitting unit 20.

Therefore, the circumscribed circle radius R [m of the deflecting mirror 33 is
m] is more preferably calculated by R = R min · t [mm], (1 ≤ t ≤ 1.15) (4). Next, the radius of the circumscribed circle of the deflecting mirror is determined using the angle θi at which the laser beam L is incident on the center of each reflecting surface and the number of reflecting surfaces as variables.

Here, the number of reflecting surfaces is indicated by N, and N is 1
0, 12 and 18 (the number of planes conventionally used such as 4, 6 or 8 cannot secure the linear density even when rotated at high speed), and the incident angle θi is π / 6 and π As / 4 [rad], the circumscribed circle radius R is obtained from the equations (3) and (4).

FIG. 5 is a graph showing the circumscribed circle radius R obtained by the equations (3) and (4) with the minimum effective rotation angle defined by the number of reflecting surfaces as the axis. According to FIG. 5, the horizontal axis is the minimum value effective rotation angle, and the rotation angle between the ends k and k of the effective portion of each reflection surface shown in FIG. (Corresponding to the length), the angle θ is obtained by removing the rotation angle occupied by the incident angle θi of the incident laser beam having the diameter indicated by a. The axis scale is logarithmic.

As is clear from FIG. 5, the circumscribed circle radius R takes the minimum value regardless of the number N of the reflecting surfaces.
Assuming that the circumscribed circle radius R is constant, the length of the effective area of each reflecting surface, that is, the effective rotation angle decreases as the number of reflecting surfaces increases. Therefore, in FIG. As the number increases, the circumscribed circle radius R also gradually increases. Further, from FIG. 5, the beam diameter a of the incident laser beam is
It is easily understood that each graph is shifted upward (in a direction in which R is increased) when is increased, and is shifted downward (in a direction in which R is decreased) when the beam diameter a is decreased.

This is because the optimum size of the deflecting mirror 33 can be determined by considering the circle inscribed by the regular polygons defined by all the reflecting surfaces, that is, the circumscribed circle of the regular polygons, from the equation (3). Indicates that can be specified.

Therefore, the number of faces N is maximized, and
In order to make the circumscribed circle radius R of the deflection rotating mirror 33 as small as possible, the minimum value R min obtained by the equation (3) and 1 ≤ k
By determining the size of the deflecting / reflecting mirror 33 according to the margin ratio shown by ≦ 1.15, the deflecting / reflecting mirror 33 is provided which is not restricted by other optical elements in the optical device.

[0046]

As described above, according to the present invention, regardless of the arrangement and size of each optical element in the optical device which gives various restrictions to the size of the deflecting reflecting mirror, the high speed and the high speed can be achieved. It is possible to easily define the size of the polygonal mirror, that is, the deflecting reflecting mirror of the optical deflecting device capable of high-speed rotation capable of fine definition.

Therefore, the beam diameter of the laser beam guided to each reflecting surface, the angle of incidence of the laser beam on each reflecting surface, and the number of reflecting surfaces need only be defined as variables to guide the laser beam onto the photosensitive member. It is possible to provide, without trial and error, a deflecting mirror that does not change the beam diameter of a certain laser beam.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an image forming apparatus in which an optical device of the present invention is incorporated.

2 is a plan view showing in detail an optical device incorporated in the image forming apparatus shown in FIG. 1 and a cross-sectional view at a position including a rotation axis of a light deflecting device.

FIG. 3 is a plan view, a front view and a side view showing a light emitting unit incorporated in the optical device shown in FIG.

4 is a schematic diagram showing the relationship between the number of reflecting surfaces of the deflecting mirror of the optical deflecting device incorporated in the optical device shown in FIG. 2 and the effective rotation angle (deflection angle).

FIG. 5 is a graph showing a change in size of a reflecting mirror that is an example of the present invention.

[Explanation of symbols]

2 ... Laser beam printer (image forming apparatus), 4 ...
Data processing unit, 6 ... Control unit, 8 ... Image memory (data storage unit), 10 ... Scanning exposure unit (optical device), 11 ... Housing, 12 ... Side wall, 13, 14, 15, 16 ... Fixed guide, 19
... Cover, 20 ... Light emitting unit, 21 ... Semiconductor laser device
(Light source), 22 ... First lens, 23 ... Cylindrical lens
(Second lens), 24 ... Aperture, 25 ... Lens barrel (or lens holder), 26 ... Laser holder, 29 ... Shielding glass, 30 ... Optical deflecting device (deflecting means), 31 ... Scanner motor, 32 ... Rotating shaft, 33 ... Reflecting mirror, 33c ... Circular circumscribing a regular polygon by the reflecting surface of the reflecting mirror, 34 ... Light deflection m device sound insulation wall, 36 ... Cooling fan, 37a, 37b ... Fixed part, 41 ... Shielding glass, 42 ... 3 lenses, 42a, 42b ... Fixed leg portion, 43 ... Second mirror, 44
... 4th lens, 45 ... 3rd (emission) mirror, 46 ... Shielding glass, N ... Number of reflecting surfaces, R ... Radius of circumscribing circle, a ... Beam diameter of incident laser beam, .theta.i ... Incident angle of incident laser beam , Θ: effective rotation angle, α: angle formed by the end k of the effective portion of each reflecting surface and the joint between the reflecting surfaces, 50 ... Image forming unit (image forming means), 51 ... Photoconductor, 52 ... Charging device, 53 ...
Developing device (developing means), 54 ..., 55 ... Cleaning device,
56 ... Static eliminator, 57 ... Fixing device, 61a, 61b ... Paper cassette, 62a, 62b ... Paper feeding roller, 63, 64 ... Conveying roller, 6
5, 66 ... Paper guide, 67 ... Aligning roller, 68 ... Bypass feeder, 69 ... Discharge roller, 70 ... Switching gate,
71 ... Ejection section, 72 ... Conveyance path, 73 ... Ejection roller, 74 ... Ejection section, paper ... P.

Claims (3)

[Claims] 1. A plurality of reflecting surfaces, each of the plurality of reflecting surfaces, the number of the reflecting surfaces, the cross-sectional diameter of light guided to the reflecting surfaces, the effective reflection area of the reflecting surfaces, and the light incident thereon. And a supporting member formed on the circumference of a circle defined based on the angle, and deflecting means for deflecting the light guided to each of the reflecting surfaces in a predetermined direction, and the deflecting means. An image forming means for forming an image of the deflected light on a predetermined position of the object. 2. A light source, a light source side optical means for imparting a predetermined characteristic to a cross-sectional shape of light from the light source, a plurality of reflecting surfaces, and each of the plurality of reflecting surfaces according to the number of the reflecting surfaces. A supporting member provided on the circumference of a circle defined by, and deflecting light passing through the light source side optical means guided by each reflecting surface toward an object, Image forming means for forming an image of the light deflected by the deflecting means on a predetermined position of the object, and the cross-sectional diameter of the light in the main scanning direction on each of the reflecting surfaces is a [m
m], the radius of the circumscribed circle circumscribing the regular polygon defined by the reflective surface is R [mm], the minimum value of the radius of the circumscribed circle is R min [mm], the number of the reflective surfaces is N, and The angle formed by the ineffective region at the end of each reflecting surface and the connection point between the reflecting surfaces is α [rad], and the incident angle when the light is incident on the center of each reflecting surface is θi [rad]. , And when the effective rotation angle of each reflection surface is represented by θ [rad], respectively, An optical device including a deflection means, wherein: 3. A light source, a light source side optical means for imparting a predetermined characteristic to a cross-sectional shape of light from the light source, a plurality of reflecting surfaces, and each of the plurality of reflecting surfaces according to the number of the reflecting surfaces. And a supporting member for holding the light on the circumference of a circle defined by the above, and deflecting the light passing through the light source side optical means guided by each reflecting surface toward the object, and the deflecting means. Image forming means for forming an image of the light deflected by the means on a predetermined position of the object, and the cross-sectional diameter of the light in the main scanning direction on each of the reflecting surfaces is a [m
m], the radius of the circumscribed circle circumscribing the regular polygon defined by the reflective surface is R [mm], the minimum value of the radius of the circumscribed circle is R min [mm], the number of the reflective surfaces is N, and The angle formed by the ineffective region at the end of each reflecting surface and the connection point between the reflecting surfaces is α [rad], and the incident angle when the light is incident on the center of each reflecting surface is θi [rad]. , The effective rotation angle of each of the reflecting surfaces is θ [rad], and the margin ratio in consideration of the fact that the cross-sectional diameter of the light is changed is t
And, when showing, respectively, And R = R min · t, 1 ≤ t ≤ 1.
15. An optical device including deflecting means, characterized in that