JPH11218716A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a rotary polygon mirror from being polluted by outside air by-passing the end part of an image forming lens. SOLUTION: An image forming lens 4 for forming an image of scanning light reflected from the rotary polygon mirror 2 on a photosensitive body is positioned by abutting positioning parts 4a formed on both the ends of the lens 4 upon the positioning parts 5b of an optical box 5. In order to interrupt an air flow bypassing the end parts of the lens 4 through gaps between the positioning parts 4a of the lens 4 and the positioning parts 5b of the box 5, gaps between supporting bodies 5d projected from the side wall of the box 5 and the lens 4 are filled with dust-proof members 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device used for an image forming apparatus such as a laser beam printer and a laser facsimile.

[0002]

2. Description of the Related Art A scanning optical device used in an image forming apparatus such as a laser beam printer or a laser facsimile irradiates a light beam such as a laser beam onto a reflecting surface of a rotary polygon mirror and performs deflection scanning by high-speed rotation of the rotary polygon mirror. I do. The scanning light obtained in this way is formed on a photoreceptor on a rotating drum to form an electrostatic latent image. Next, the electrostatic latent image on the photoreceptor is visualized into a toner image by a developing device, transferred to a recording medium such as recording paper, sent to a fixing device, and printed by heating and fixing the toner on the recording medium ( Print) is performed.

[0003] Figure 12 shows a scanning optical apparatus according to a conventional example, which includes a light source unit which unit of the semiconductor laser 101 and the collimator lens, for deflecting and scanning the laser beam L ₀ of the parallel light beam generated therefrom It has a rotating polygon mirror 102, an image forming lens 104 for forming an image of the scanning light on a photoreceptor on the surface of a rotating drum (not shown) via a mirror 103. The rotating polygon mirror 102 and the imaging lens 104 are housed in an optical box 105, and the light source unit is mounted on a side wall of the optical box 105.

The upper opening of the optical box 105 is
After all the necessary parts are incorporated in the inside, it is closed by the lid member 106 shown in FIG. The optical box 105
The bottom wall is provided with a window 105a for taking out the scanning light of the rotating polygon mirror 102 toward an external rotating drum.

[0005] The laser beam L _0, which is generated from the semiconductor laser 101 of the light source units are collimated by the collimator lens, is converged into a linear shape on the reflective surface of the rotary polygon mirror 102 by the cylindrical lens 101a, the motor 102a
Is deflected and scanned by the high-speed rotation of the rotary polygon mirror 102 by means of The scanning light thus obtained is transmitted to the imaging lens 1
The light is reflected downward by the folding mirror 103 via the optical disk 104, and is taken out from the window 105 a of the optical box 105 toward the rotating drum. The scanning light that forms an image on the photoreceptor on the rotating drum forms an electrostatic latent image with the main scanning by the rotating polygon mirror 102 and the sub-scanning by the rotation of the rotating drum.

A charging device for uniformly charging the surface of the photoreceptor is provided around the photoreceptor, a visualization device for visualizing an electrostatic latent image formed on the surface of the photoreceptor into a toner image, A transfer device or the like for transferring the toner image to a recording medium such as a recording paper is provided.
Is recorded on a recording sheet or the like corresponding to the light beam in which is generated.

The scanning light from the rotating polygon mirror 102 is separated at the end in the main scanning direction and introduced into a BD sensor (not shown). The scanning light detected by the BD sensor is converted into a trigger signal in a processing circuit and is introduced into the semiconductor laser 101. After receiving the trigger signal, the semiconductor laser 101 starts write modulation based on image information transmitted from the host computer.

The image forming lens 104 is a lens having a so-called fθ function for forming the scanning light of the rotary polygon mirror 102 on the photosensitive member as described above and making the scanning speed of the resulting point image uniform. After being strictly positioned as follows with respect to the optical path of the scanning light, it is fixed to the optical box 105.

That is, by bringing a pair of positioning portions 104a formed at both ends of the imaging lens 104 into contact with a pair of positioning portions 105b provided on the optical box 105, the optical axis direction of the imaging lens 104 (X axis Direction) and tilt angle (θ
(Axial direction) and the like are strictly determined, and fixed with a holding spring or an adhesive. Regarding the height direction (Z-axis direction) of the imaging lens 104, the bottom surface of the imaging lens 104 is positioned by contacting three pedestals 105c provided on the bottom wall of the optical box 105, and by a method such as bonding. Fix it. Thus, the imaging lens 104 is assembled to the optical box 105.

Although the inside of the optical box 105 is almost sealed by closing the upper opening with the lid member 106 as described above, the inside of the optical box 105 is inserted into the optical box 105 through a window 105a for taking out scanning light toward the rotating drum. There is a problem that the reflecting surface of the rotary polygon mirror 102 is contaminated by the invading outside air. In recent years, higher performance and higher speed of the image forming apparatus have been desired, and the number of rotations of the rotary polygon mirror 102 may be 30,000 rpm or more.

When the rotary polygon mirror 102 rotates at a high speed, a large negative pressure is generated inside the optical box 105, a large amount of outside air is sucked, and the atmosphere A ₀ around the rotary polygon mirror 102 becomes dirty. Become. In addition, the rotation of the rotating polygon mirror 102 generates a vortex of air at the top and the like, and when such an air flow collides with the reflecting surface, floating dust of dirty air adheres to the reflecting surface of the rotating polygon mirror 102. In addition, the reflectivity is reduced, the image quality of the image forming apparatus is degraded, and a trigger signal cannot be detected.

The air outside the optical box 105 contains a large amount of toner for visualizing the electrostatic latent image on the photoreceptor and floating dust such as paper dust generated from recording paper. Such floating dust enters the optical box 105 and the rotating polygon mirror 10
Dust prevention measures to prevent contamination of the scanning optical system 2 are extremely important in promoting high-speed scanning optical devices.

Therefore, the space between the top of the imaging lens 104 and the lid member 106 is sealed by a sponge-like dustproof member 107 such as urethane foam to prevent the atmosphere A ₀ around the rotary polygon mirror 102 from being contaminated. Has been made.

However, the imaging lens 104 and the lid member 1
06, the height of the pedestal 105c that is in contact with the bottom surface of the imaging lens 104 is generally about 0.3 to 0.5 mm (see FIG. 13) even if the space between the optical box 105 and the dustproof member 107 is sealed. air dirt from gaps B ₀ of the bottom wall and the imaging lens 104 from entering the atmosphere a ₀ around the rotary polygon mirror 102 is contaminated.

Therefore, as shown in FIGS. 14 and 15, a gap between the bottom wall of the optical box 205 and the imaging lens 204 is sealed by a sponge-like second dustproof member 208 such as urethane foam. Is being developed. That is, before assembling the imaging lens 204 to the optical box 205, the dustproof member 208 is fixed to the bottom wall using a double-sided tape, and the imaging lens 204 is placed on the dustproof member 208 and the dustproof member 208 is mounted. Is compressed, and the imaging lens 204 is fixed to the pedestal 205c by a pressing spring or the like.

In order to stably attach the dustproof member 208 to the optical box 205, the dustproof member 2
It is necessary to devise a groove 205d to which the optical box 205 is fitted, and the shape of the optical box 205 is complicated.

[0017]

However, according to the above prior art, the space between the lid member of the optical box and the top of the imaging lens is closed by the first dustproof member, and the image is formed on the bottom wall of the optical box. Even if the space between the bottoms of the lenses is closed with the second dustproof member,
As shown in FIG. 6, since a gap is formed between the positioning portion 204a for positioning the imaging lens 204 in the X-axis direction and the positioning portion 205b of the optical box 205, an air flow indicated by an arrow C is generated, and There is an unsolved problem that it cannot be avoided that dust of about 0.3 μm invades and contaminates the reflecting surface of the rotating polygon mirror 202.

The both ends of the imaging lens 204 are shown in FIG.
7, the following problem arises if it is configured to be fixed by the spring 206 shown in FIG. That is, the spring 206 is fixed by being locked to a protrusion of a support 205e disposed on the opposite side of the positioning portion 205b of the optical box 205, and the two contact portions 206a, 20 of the spring 206 are fixed.
6b are pressed against the top surface and the side surface of the imaging lens 204, respectively. Therefore, when the projection is integrally formed on the support 205e of the optical box 205, the hole 205 for removing the molding piece is formed.
f must be opened, and from here optical box 2
Dirty outside air invades inside 05. In addition, since the contact portion 206a of the spring 206 is configured to contact the top surface of the imaging lens 204, the dustproof member 207 must be disposed so as not to interfere with the contact portion 206a of the spring 206. However, there is an unsolved problem that outside air enters through a gap in this portion and the dustproof effect is reduced.

The present invention has been made in view of the above-mentioned unresolved problems of the prior art, and is intended to simply and effectively close a gap formed between an imaging lens and a lid member or an optical box. It is another object of the present invention to provide a high-performance and inexpensive scanning optical device capable of greatly improving a dust-proof effect for preventing contamination of a rotary polygon mirror.

[0020]

In order to achieve the above object, a scanning optical apparatus according to the present invention comprises a rotating polygonal mirror for deflecting and scanning a light beam, an imaging lens disposed on an optical path of the scanning light, and a light source. An optical box accommodating the imaging lens and the rotating polygon mirror, a lid member for closing an opening of the optical box, a top dustproof member for sealing between the lid member and a top surface of the imaging lens, It is characterized in that it has a pair of end dustproof members for sealing between a side surface opposite to the positioning portions at both ends of the imaging lens and a predetermined protrusion of the optical box.

It is preferable that a bottom dust-proof member is provided which is in contact with the side surface of the bottom of the imaging lens to seal between the bottom surface of the imaging lens and the bottom wall of the optical box.

It is preferable that the end dustproof member is press-fitted between a predetermined projection of the optical box and the imaging lens.

It is preferable that the end dust-proof member also serves as fixing means for fixing the imaging lens to the optical box.

It is preferable that the end dust-proof member is formed of a sheet metal and an elastic member.

It is preferable that the top dustproof member, the end dustproof member, and the bottom dustproof member are integrated.

[0026]

[Effect] Even if the gap formed between the lid member of the optical box and the imaging lens is closed by the top dust-proof member, dust and the like carried by the air flow bypassing both ends of the imaging lens reflect the reflection surface of the rotating polygon mirror. And contaminates the optical performance. Therefore, an end dust-proof member is inserted into a gap between the side surfaces of both ends of the imaging lens and the protruding portion of the optical box to seal the gap and enhance the dust-proof effect.

In addition, if a bottom dust-proof member is abutted below the side surface of the imaging lens to thereby seal a gap between the bottom surface of the imaging lens and the bottom wall of the optical box, the dust circumvents the imaging lens. All air flow can be shut off.

By extremely effectively preventing the dust and the like in the outside air from entering the atmosphere around the rotary polygon mirror, it is possible to realize a high-performance scanning optical device which can be operated for a long time without any maintenance and has a low running cost. .

Further, by using an elastic member or the like in which the top dustproof member, the end dustproof member, and the bottom dustproof member are integrated, if the number of assembly parts and the number of assembly steps of the apparatus are reduced, the manufacturing cost of the scanning optical apparatus can be reduced. Can be greatly reduced, which can contribute to a reduction in the price of the device.

[0030]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a scanning optical device according to a first embodiment, which comprises a light source unit in which a semiconductor laser 1 and a collimator lens are unitized, and a laser beam of a parallel light beam which is a light beam generated from the unit. a rotary polygon mirror 2 for deflecting and scanning the light L _1, the mirror 3 folding the scanning light
And an image forming lens 4 for forming an image on the photoreceptor on the surface of the rotating drum, which is an image forming position, through the image forming apparatus. The rotating polygon mirror 2 and the imaging lens 4 are housed in an optical box 5, and the light source unit is mounted on a side wall of the optical box 5.

The upper opening of the optical box 5 has all necessary components incorporated in the optical box 5, and as shown in FIG.
It is closed by the lid member 6. The bottom wall of the optical box 5 is provided with a window 5a for taking out the scanning light of the rotary polygon mirror 2 toward an external rotary drum.

The laser beam L ₁ generated from the semiconductor laser 1 of the light source unit is collimated by the collimator lens, is converged into a linear shape on the reflective surface of the rotary polygon mirror 2 by the cylindrical lens 1a, the rotation caused by the driving of the motor 2a Deflection scanning is performed by the high-speed rotation of the polygon mirror 2. The scanning light obtained in this way is reflected downward by the turning mirror 3 via the imaging lens 4, and is reflected by the window 5 a of the optical box 5.
From the rotating drum. The scanning light that forms an image on the photoreceptor on the rotating drum forms an electrostatic latent image with the main scanning by the rotating polygon mirror 2 and the sub-scanning by the rotation of the rotating drum.

A part of the scanning light is separated at the end in the main scanning direction and introduced into a BD sensor (not shown).
The signal is converted into a trigger signal in the processing circuit and sent to the semiconductor laser 1. After receiving the trigger signal, the semiconductor laser 1 starts write modulation based on image information transmitted from the host computer.

The imaging lens 4 has a so-called fθ function for forming the scanning light of the rotating polygon mirror 2 on the photosensitive member and making the scanning speed of the resulting point image uniform. On the other hand, it is fixed to the optical box 5 after being strictly positioned as described below.

That is, by bringing a pair of positioning portions 4a formed at both ends of the imaging lens 4 into contact with a pair of positioning portions 5b provided on the optical box 5, the optical axis direction of the imaging lens 4 (X-axis direction) Direction) and the inclination angle (θ-axis direction) are strictly determined, and the height direction of the imaging lens 4 (Z-axis direction)
With respect to the above, the bottom surface of the imaging lens 4 is positioned in contact with three pedestals 5c provided on the bottom wall of the optical box 5, and fixed using an adhesive or the like. Thus, the imaging lens 4 is assembled to the optical box 5.

Although the inside of the optical box 5 is almost sealed by closing the upper opening with the lid member 6 as described above, the inside of the optical box 5 is intruded into the optical box 5 from the window 5a for taking out scanning light. In addition, there is a problem that the reflection surface of the rotary polygon mirror 2 is contaminated. In recent years, higher performance and higher speed of the image forming apparatus have been desired, and the rotation speed of the rotary polygon mirror 2 may be 30,000 rpm or more.

[0038] When the rotary polygon mirror 2 is rotated at a high speed, whereby a large negative pressure is generated inside of the optical box 5, is a large amount of outside air intake, and a state in which the atmosphere A ₁ around the rotary polygon mirror 2 is soiled Become. In addition, the rotation of the rotary polygon mirror 2 generates a vortex of air at the top and the like, and when such an air flow collides with the reflection surface, the floating dust of dirty air adheres to the reflection surface of the rotary polygon mirror 2. In addition, the reflectivity is reduced, the image quality of the image forming apparatus is degraded, and a trigger signal cannot be detected.

The air outside the optical box 5 contains a large amount of toner for visualizing the electrostatic latent image on the photoconductor and floating dust such as paper dust generated from recording paper. Dust prevention measures for preventing such floating dust from entering the optical box 5 and contaminating the rotary polygon mirror 2 are extremely important in promoting a high-speed scanning optical apparatus.

Therefore, as shown in FIG.
Devised that between the top and the lid member 6 is sealed by the first dust guard 7 is a spongy top dustproof member of urethane foam, preventing the atmosphere A ₁ around the rotary polygon mirror 2 is contamination of the It has been done.

The height of each pedestal 5c that contacts the bottom surface of the imaging lens 4 is generally about 0.3 to 0.5 mm, and is formed between the imaging lens 4 and the bottom wall of the optical box 5. and invades the air contaminated from the gap is, the atmosphere a ₁ around the rotary polygon mirror 2 is likely to be contaminated. Therefore, optical box 5
A second dustproof member 8 is provided as a bottom dustproof member for closing the gap between the bottom wall and the imaging lens 4 (see FIG. 3). The second dustproof member 8 is an elastic member made of a sponge-like material such as urethane foam, similarly to the first dustproof member 7,
It is inserted between the bottom of the imaging lens 4 and the bottom wall of the optical box 5.

Next, a third dustproof member 9 as an end dustproof member is filled between the support 5d, which is a protruding portion projecting from the side wall of the optical box 5, and both ends of the imaging lens 4. Positioning section 5b of optical box 5 and positioning section 4 of imaging lens 4
blocking the air flow entering the space A ₁ surrounding the rotating polygon mirror 2 and diverted from between a. Like the first and second dustproof members 7, 8, the third dustproof member 9 is also a sponge-like elastic member such as urethane foam, and as shown in FIG. What was pasted on 9b,
Although it is most preferable from the viewpoint of assembling workability, it is also possible to integrally mold only urethane foam or the like.

A total of two third dustproof members 9 are provided, one at each end of the imaging lens 4, and the abutting position of the third dustproof member 9 is the position of the positioning portion 4 a of the imaging lens 4 in the X-axis direction. It is desirable to have the side of the opposite side on the opposite side. Further, a groove 5e may be provided in each support 5d of the optical box 5, and each dustproof member 9 may be dropped into the groove 5e.

When assembling the imaging lens 4, the second dustproof member 8 is attached to the bottom surface of the optical box 5,
The positioning portion 4a of the optical box 5 is brought into contact with the positioning portion 5b of the optical box 5, and the bottom surface of the imaging lens 4 is adhered to the pedestal 5c of the optical box 5. Then, as shown in FIG. The third dust-proof member 9 is inserted between the optical box 4 and the lower end thereof is brought into close contact with the bottom surface of the optical box 5. After assembling all necessary parts in the optical box 5, as shown in FIG.
The first dustproof member 7 is placed on the top surface of the device, and the lid member 6 is attached.

According to the present embodiment, the airflow bypassing both ends of the imaging lens is blocked by the third dustproof member, so that the atmosphere around the rotary polygon mirror together with the first and second dustproof members can be prevented. Is completely sealed, and contamination of the rotary polygon mirror by dust and the like in the outside air can be prevented very effectively.

As a result, the reflecting surface of the rotary polygon mirror is kept in a clean state for a long time, and a long-life scanning optical device with high performance and low maintenance cost can be realized.

FIG. 4 shows a first modification. In this case, a second dustproof member 18 for sealing between the imaging lens 14 and the bottom wall of the optical box 15 is in contact with the side surface of the bottom of the imaging lens 14. In this case, the lower end of the third dustproof member 19 is brought into close contact with the top of the second dustproof member 18.

FIG. 5 shows a second modification. This is the third
The dustproof member 29 is inserted between the support 25d of the optical box 25 and the imaging lens 24 while being compressed in the thickness direction. Support 25d and imaging lens 2
The imaging lens 24 can be pressed against the positioning portion 25b of the optical box 25 by the third dustproof member 29 press-fitted between the four and fixed thereto. That is, since the third dustproof member 29 also functions as the fixing means of the imaging lens 24, there is an advantage that it is not necessary to use a method such as adhesion for fixing the imaging lens 24.

More specifically, the support 2 of the optical box 25 will be described.
The difference between the width T1 between the bottom of the 5d groove 25e and the imaging lens 24 and the thickness T2 of the dustproof member 29, that is, the crushing amount T3 of the dustproof member 29 is T3 = T2−T1 If the value of T3 is large, the dustproof member 29 The crushing amount increases, and the fixing force for fixing the imaging lens 24 to the optical box 25 increases.
Assuming that a spring constant K indicates the elasticity of the dustproof member 29, the pressing force F1 of the dustproof member 29 pressing the imaging lens 24 is F1 = KT3. F1 such that the imaging lens 24 does not move due to impact or the like
The material of the dustproof member 29, that is, the spring constant K, is set so that the load setting is about 0.5 kg to 1.0 kg on one side.
1, T2 may be set.

As described above, if the imaging lens is fixed by using the dustproof member, and the spring or the like as in the conventional example is eliminated, the number of assembled parts and the assembly cost can be greatly reduced.

FIG. 6 shows a scanning optical device according to a second embodiment, which comprises a light source unit in which a semiconductor laser 31 and a collimator lens are unitized, and a laser beam of a parallel light beam which is a light beam generated from the light source unit. A rotary polygon mirror 32 deflects and scans the light L _2, and an image forming lens 34 for forming an image of the scanning light on a photoreceptor on the surface of a rotating drum, which is an image forming position, via a return mirror 33. Rotating polygon mirror 32
The imaging lens 34 is housed in an optical box 35, and the light source unit is assembled on a side wall of the optical box 35.

The upper opening of the optical box 35 is closed by a lid member 36 as shown in FIG. 7 after all necessary components are incorporated in the optical box 35. The optical box 3
A window 35a for taking out the scanning light of the rotary polygon mirror 32 toward an external rotary drum is provided on the bottom wall of the fifth mirror.

The laser beam L ₂ generated from the semiconductor laser 31 of the light source unit is collimated by a collimator lens, condensed linearly on a reflecting surface of a rotary polygon mirror 32 by a cylindrical lens 31a, and rotated by driving a motor 32a. Deflection scanning is performed by the high-speed rotation of the polygon mirror 32. The scanning light obtained in this manner is applied to the imaging lens 34.
Is reflected downward by the turning mirror 33,
It is taken out from the window 35a of the optical box 35 toward the rotating drum. The scanning light that forms an image on the photoreceptor on the rotating drum forms an electrostatic latent image with the main scanning by the rotating polygon mirror 32 and the sub-scanning by the rotation of the rotating drum.

A part of the scanning light is separated at the end in the main scanning direction, and introduced into a BD sensor (not shown).
The signal is converted into a trigger signal in the processing circuit and sent to the semiconductor laser 31. After receiving the trigger signal, the semiconductor laser 31 starts write modulation based on image information transmitted from the host computer.

The imaging lens 34 has a so-called fθ function for forming the scanning light of the rotary polygon mirror 32 on the photosensitive member and making the scanning speed of the resulting point image uniform. On the other hand, it is fixed to the optical box 35 after being strictly positioned as described below.

That is, the pair of positioning portions 34a formed at both ends of the imaging lens 34 are brought into contact with the pair of positioning portions 35b provided in the optical box 35, so that the optical axis direction of the imaging lens 34 (X-axis direction), tilt angle (θ-axis direction), etc., are strictly determined. In the height direction (Z-axis direction) of the imaging lens 34, the bottom surface of the imaging lens 34 is Three pedestals 35c provided in
(See FIG. 7).

The inside of the optical box 35 is almost sealed by closing the upper opening with the lid member 36 as described above. However, since the outside air that enters the optical box 35 through the window 35a for taking out the scanning light or the like, In addition, there is a problem that the reflection surface of the rotary polygon mirror 32 is contaminated. In recent years, higher performance and higher speed of the image forming apparatus have been desired, and the number of rotations of the rotary polygon mirror 32 may be 30,000 rpm or more.

When the rotary polygon mirror 32 rotates at a high speed, a large negative pressure is generated inside the optical box 35, a large amount of outside air is sucked, and the atmosphere A ₂ around the rotary polygon mirror 32 is rotated.
Becomes dirty. In addition, the rotation of the rotary polygon mirror 32 generates a vortex of air at the top and the like, and when such an air flow collides with the reflection surface, the floating dust of dirty air adheres to the reflection surface of the rotary polygon mirror 32. In addition, the reflectivity is reduced, the image quality of the image forming apparatus is degraded, and a trigger signal cannot be detected.

Since the air outside the optical box 35 contains a large amount of toner for visualizing the electrostatic latent image on the photoconductor and floating dust such as paper dust generated from recording paper, etc. Dust prevention measures to prevent such floating dust from entering the optical box 35 and contaminating the rotary polygon mirror 32 are extremely important in promoting a high-speed scanning optical apparatus. In particular, the rotating polygon mirror 32 is inserted through a gap between the imaging lens 34 and the lid member 36.
Air entering the atmosphere A ₂ around the
Significantly contaminates the reflective surface of

The height of each pedestal 35c that contacts the bottom surface of the imaging lens 34 is generally about 0.3 to 0.5 mm, and is formed between the imaging lens 34 and the bottom wall of the optical box 35. Dirty air penetrates through the gap, and the rotating polygon mirror 32
There is a risk that the atmosphere A ₂ surrounding of contamination.

In addition, the atmosphere A ₂ around the rotary polygon mirror 32 is generated by the air flow bypassing both ends of the imaging lens 34.
May be contaminated.

Therefore, a first dust-proof portion 37a, which is a top dust-proof member for sealing between the top of the imaging lens 34 and the lid member 36, and a portion between the bottom of the imaging lens 34 and the bottom wall of the optical box 35. A second dust-proof portion 37b, which is a bottom dust-proof member for sealing the gap between the bottom and the side of the imaging lens 34, and a support 35d, which is a protrusion of the optical box 35, at both ends of the imaging lens 34. A dustproof member 37 which is an elastic member integrated with a third dustproof portion 37c which is an end dustproof member for sealing.
Is attached, the atmosphere A ₂ around the rotary polygon mirror 32 is
From the outside air completely.

The first to third dustproof portions 37a of the dustproof member 37
The thickness of ~ 37c is set as follows.

First, as shown in FIG. 8 and FIG.
Is in contact with the side surface of the imaging lens 34 opposite to the positioning portion 34a, and the support 35d and the imaging lens 3
The difference T6 between the distance T4 and the thickness T5 of the dustproof portion 37c.
Becomes T6 = T5−T4. If the value of T6 is large, the amount of crushing of the dustproof portion 37c increases, and the fixing force for fixing the imaging lens 34 to the optical box 35 increases. Assuming that a spring constant K indicates the elasticity of the dustproof portion 37c, the pressing force F2 of the imaging lens 34 is F2 = K · T6. The material of the dustproof member 37, that is, the spring constant K, T4 and T4 is set so that the load is set so that the imaging lens 34 does not move due to impact or the like (about 0.5 kg to 1.0 kg on one side).
5 may be set.

As shown in FIG. 10, the first dustproof portion 37a is in contact with the top surface of the imaging lens 34, and
6 is compressed when assembled. The difference T9 between the distance T7 between the top surface of the imaging lens 34 and the lid member 36 and the thickness T8 of the dustproof portion 37a is T9 = T8−T7. If the value of T9 is large, the crushing amount of the dustproof portion 37a increases. The load applied to the imaging lens 34 increases. Dustproof part 3
The pressing force F3 of the imaging lens 34 by 7a is F3 = KT9. The load (0. 0) that does not cause the inclination of the imaging lens 34 or the deterioration of the performance due to the load of the imaging lens 34 being too large.
T7, T8, etc. may be set so as to be about 1 kg).

As shown in FIG. 11, the second dustproof portion 37b
Is press-fitted between a bottom side surface of the imaging lens 34 and a restraining member 35f provided upright on the bottom wall of the optical box 35. The difference T12 between the distance T10 between the side surface of the imaging lens 34 and the restraint member 35f and the thickness T11 of the dustproof portion 37b is T12 = T11−T10. If the value of T12 is large, the amount of crushing of the dustproof portion 37b increases, The hermeticity between the imaging lens 34 and the optical box 35 is improved. Pressing force F4 of the imaging lens 34 by the dustproof part 37b
Is F4 = K · T12. A load setting (0.1 kg) that does not impair the performance of the imaging lens 34 even when the load F4 is applied to the imaging lens 34
T10, T11, etc. may be set so that

As described above, by using a dust-proof member in which three dust-proof portions that respectively block the air flow bypassing the top, bottom, and end of the rotary polygon mirror are integrated, the number of assembly parts and the number of assembly steps of the apparatus are increased. Can be greatly reduced, and the cost of the scanning optical device can be reduced. The other points are the same as in the first embodiment.

[0068]

Since the present invention is configured as described above, it has the following effects.

By simply and effectively closing all the gaps formed between the imaging lens and the lid member or the optical box, the dust-proof effect for preventing contamination of the rotary polygon mirror can be greatly enhanced. As a result, a high-performance and inexpensive scanning optical device that can be operated for a long time without any maintenance can be realized. By mounting such a scanning optical device, it is possible to greatly contribute to higher performance and lower cost of the image forming apparatus.

[Brief description of the drawings]

FIGS. 1A and 1B show a scanning optical device according to a first embodiment, wherein FIG. 1A is a schematic plan view thereof, and FIG. 1B is a perspective view showing only a third dustproof member.

FIG. 2 is a schematic plan view showing a state in which a first dustproof member is mounted on the apparatus of FIG.

FIG. 3 is a sectional view showing the apparatus of FIG. 2;

FIG. 4 is a cross-sectional view showing a modification of the first embodiment.

FIG. 5 is a sectional view showing another modification of the first embodiment.

FIG. 6 is a schematic plan view showing a scanning optical device according to a second embodiment.

FIG. 7 is a sectional view showing the device of FIG. 6;

FIG. 8 is a perspective view showing only an imaging lens and a dustproof member of the apparatus of FIG. 7;

9 is a diagram showing a thickness of a third dustproof portion of the dustproof member of FIG.

FIG. 10 is a diagram illustrating the thickness of a first dustproof portion of the dustproof member of FIG. 8;

FIG. 11 is a diagram illustrating the thickness of a second dustproof portion of the dustproof member in FIG. 8;

FIG. 12 is a schematic plan view showing a conventional example.

FIG. 13 is a sectional view showing the device of FIG.

FIG. 14 is a schematic plan view showing another conventional example.

FIG. 15 is a sectional view showing the apparatus of FIG. 14;

FIG. 16 is a diagram illustrating an airflow flowing around an end of the imaging lens.

FIG. 17 is a view showing a spring for fixing an end of the imaging lens.

18 is a sectional view showing the device of FIG.

[Explanation of symbols]

 1,31 semiconductor laser 2,32 rotating polygon mirror 3,33 folding mirror 4,14,24,34 imaging lens 5,15,25,35 optical box 6,36 lid member 7,8,9,18,19, 29, 37 Dustproof member 37a, 37b, 37c Dustproof part

Claims (6)

[Claims] A rotary polygon mirror for deflecting and scanning a light beam;
An imaging lens disposed on the optical path of the scanning light, an optical box for housing the imaging lens and the rotating polygon mirror, a lid member for closing an opening of the optical box, the lid member and the imaging lens A top dustproof member for sealing between the top surfaces of the optical lens, and a pair of end dustproof members for sealing between a side surface opposite to the positioning portion at both ends of the imaging lens and a predetermined protrusion of the optical box. Scanning optical device having. 2. The apparatus according to claim 1, further comprising a bottom dust-proof member abutting on a side surface of a bottom portion of the imaging lens to seal between a bottom surface of the imaging lens and a bottom wall of the optical box. Scanning optics. 3. The scanning optical device according to claim 1, wherein the end dust-proof member is press-fitted between a predetermined protrusion of the optical box and the imaging lens. 4. The scanning optical apparatus according to claim 3, wherein the end dust-proof member also serves as fixing means for fixing the imaging lens to the optical box. 5. The scanning optical device according to claim 1, wherein the end dust-proof member is constituted by a sheet metal and an elastic member. 6. The scanning optical device according to claim 2, wherein the top dustproof member, the end dustproof member, and the bottom dustproof member are integrated.