JPH11183818A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and firmly assemble a dust-proofing member for blocking a gap below an image formation lens. SOLUTION: A gap between an image formation lens 4 and a cover member 6 and a gap between the lens 4 and the bottom wall of an optical box 5 are respectively blocked by 1st and 2nd dust-proofing members 7, 8. The member 8 is firmly fixed on the box 5 by sticking a part of the member 8 to the bottom wall of the box 5 by a pressure sensitive adhesive double coated tape having adhesiveness on both faces and inserting its inner end under a restricting member 11 projected from the side face of the lens 4.

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 14 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 turning mirror 103, and the like. 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 therein, it is closed by the lid member 106 shown in FIG. The bottom wall of the optical box 105 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 the driving of. The scanning light thus obtained is reflected downward by the turning mirror 103 through the imaging lens 104, and is extracted from the window 105a 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 with respect to the optical path of the scanning light, it is fixed to the optical box 105.

That is, the imaging lens 104 is positioned with respect to a positioning member or the like provided on the bottom surface or the partition wall of the optical box 105.
By engaging or abutting positioning portions such as abutting reference surfaces formed at both ends of the imaging lens 104,
Strictly in the length direction (Y-axis direction) or the optical axis direction (X-axis direction), and fixed by a pressing spring or the like.
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 105b to 105d provided on the bottom wall of the optical box 105, and pressed using a holding spring or the like. Alternatively, the imaging lens 104 is bonded to each of the pedestals 105b to 105d using an adhesive. In this way, the imaging lens 104 is
5 to be assembled.

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. When the rotating polygon mirror 102 rotates, an air vortex is generated at the top or the like, and when such an air flow collides with the reflecting surface, the floating dust of the dirty air adheres to the reflecting surface of the rotating polygon mirror 102 and is reflected. Lower the rate,
Inconveniences such as deterioration of the image quality of the image forming apparatus and inability to detect a trigger signal are caused.

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.

[0014]

However, according to the above-mentioned prior art, even if the space between the imaging lens and the lid member is sealed with a dustproof member, the bottom surface of the imaging lens 104 does not contact as shown in FIG. The height of the pedestals 105b to 105d in contact is generally about 0.3 to 0.5 mm, and
5 air contamination through the gap B ₀ of the bottom wall and the imaging lens 104 from entering the atmosphere A ₀ around the rotary polygon mirror 102 there is an unsolved problem that can not be avoided from being contaminated.

Therefore, as shown in FIGS. 16 and 17, the 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. This is because, before assembling the imaging lens 204 to the optical box 205, the dustproof member 20 is attached to the bottom wall thereof using a double-sided tape 209.
8 is fixed, and the imaging lens 2 is placed on the dustproof member 208.
The imaging lens 204 is fixed on the pedestals 205b to 205d by mounting the cover 04 and compressing the dustproof member 208 by a pressing spring or the like.

However, as described above, the second dustproof member 20
8 and the optical box 2 with the bottom of the imaging lens 204 in a compressed state.
When assembled between the bottom walls 05, the reaction force f of the compressive force acts upward in the figure. Overcoming this, the imaging lens 204
In order to assemble the optical lens 205 stably into the optical box 205, the pressing force F of a pressing spring or the like for pressing the imaging lens 204 against the pedestals 205b to 205d of the optical box 205 must be increased. As a result, the imaging lens 204 is distorted, deteriorating its optical characteristics and causing an image defect, and also has a disadvantage in that the efficiency of assembling the imaging lens 204 is reduced.

In addition, the optical axis direction (X
The dustproof member 208 must be formed in an elongated shape due to restrictions due to the thickness (in the axial direction), and the sealing effect tends to be insufficient. For example, when the dustproof member 308 having a large thickness as shown in FIG. 18 is used, the dustproof member 308 has a complicated shape in order to avoid interference with the pedestal 205c and the like, which leads to an increase in component costs.

In order to stably mount the dustproof member 308 on the optical box 205, it is necessary to provide a groove for fitting the dustproof member 308 on the bottom wall of the optical box 205. Is also undesirably complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and is intended to simply and firmly assemble a dustproof member for sealing a gap between an optical box and an imaging lens. It is an object of the present invention to provide a high-performance and inexpensive scanning optical device.

[0020]

In order to achieve the above object, a scanning optical apparatus according to the present invention comprises scanning means for deflecting and scanning a light beam to convert the light beam into scanning light, and provided in an optical path of the scanning light. An imaging box containing the imaging lens, the imaging lens and the scanning unit, and a dustproof member for closing a gap between the bottom wall of the optical box and the imaging lens. However, the present invention is characterized in that a restricting member for restricting one end of the dustproof member to a bottom wall of the optical box is provided.

It is preferable that the optical box includes a guide member which engages with the other end of the dustproof member.

Preferably, the guide member of the optical box includes a second restricting member for restricting the other end of the dustproof member to the bottom wall of the optical box.

A scanning means for deflecting and scanning the light beam to convert the light beam into scanning light; an imaging lens disposed on an optical path of the scanning light; and an optical box accommodating the imaging lens and the scanning means. A dustproof member for closing a gap between the bottom wall of the optical box and the imaging lens, the dustproof member being in contact with a side surface of the imaging lens to seal an opening end of the gap. A scanning optical device characterized by having such a configuration may be used.

[0024]

When there is a gap between the bottom wall of the optical box and the imaging lens, dirty air enters the atmosphere around the rotary polygon mirror and contaminates the reflection surface of the rotary polygon mirror.

Therefore, the restricting member is protruded from the side surface of the imaging lens, and the end of the dustproof member is buried under the restricting member.

As described above, by sandwiching one end of the dustproof member between the restraining member of the imaging lens and the bottom wall of the optical box and restraining it, the sealing effect of the dustproof member can be greatly improved. . In addition, the efficiency of the operation of assembling the dustproof member can be improved.

Furthermore, if a guide member is provided on the bottom wall of the optical box and a second restraining member for restraining the other end of the dust-proof member is provided on the guide member, the dust-proof member can be fixed to the bottom wall of the optical box. Since both ends can be firmly fixed, the number of assembled parts can be reduced and the assembling process can be simplified.

A scanning means for deflecting and scanning the light beam to convert the light beam into scanning light; an imaging lens disposed in an optical path of the scanning light; and an optical box accommodating the imaging lens and the scanning means. A dustproof member for closing a gap between the bottom wall of the optical box and the imaging lens, the dustproof member being in contact with a side surface of the imaging lens to seal an opening end of the gap. In the case of a scanning optical device characterized in that it is configured as described above, the dustproof member is brought into contact with the bottom wall of the optical box and the side surface of the imaging lens, and is elastically pressed against the side surface, thereby forming the imaging lens. The opening end of the gap between the optical box and the bottom wall of the optical box can be completely sealed. As described above, the sealing effect is high, and the assembling work of the dustproof member is extremely simple, so that it can greatly contribute to high performance and low cost of the device.

In addition, the pressing force when pressing the dustproof member against the side surface of the imaging lens acts on the positioning portion provided on the opposite side surface of the imaging lens, thereby stabilizing the positioning of the imaging lens. There is also an effect that can be made to. There is also an advantage that a dustproof member can be used for temporarily fixing the imaging lens in the positioning operation.

[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. having a rotary polygon mirror 2 is a scanning means for deflecting and scanning the light L _1, the image forming lens 4 for imaging the photoreceptor surface of the rotary drum is imaging position via the mirror 3 folding the scanning light. 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 opening in the upper part 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. Then, it is fixed to the optical box 5 after being strictly positioned.

That is, the positioning members such as the abutting reference surfaces formed at both ends of the imaging lens 4 engage with or come into contact with the positioning members provided on the bottom surface of the optical box 5 and the partition walls, respectively. In this way, positioning in the length direction (Y-axis direction) and the optical axis direction (X-axis direction) of the imaging lens 4 is strictly performed, and the height direction (Z-axis direction) of the imaging lens 4 is adjusted. The bottom surface of the image lens 4 is positioned in contact with three pedestals 5b provided on the bottom wall of the optical box 5, and pressed using a holding spring or the like. Alternatively, the imaging lens 4 is bonded to each pedestal 5b using an adhesive. 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. When the rotating polygon mirror 2 rotates, an air vortex is generated at the top or the like, and when such an air flow collides with the reflecting surface, floating air dust adheres to the reflecting surface,
The reflectance is reduced, and the image quality of the image forming apparatus is degraded, and inconveniences such as a failure to detect a trigger signal are caused.

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, the top of the imaging lens 4 and the lid member 6
Between and sealed by sponge-like dustproof member 7 of urethane foam, an atmosphere A ₁ around the rotary polygon mirror 2 have been made to devise prevented from being contaminated.

The height of each pedestal 5b which 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 air entering the dirty from the clearance portion, since the atmosphere a ₁ around the rotary polygon mirror 2 may be contaminated, for closing the gap between the bottom wall and the imaging lens 4 of the optical box 5 A second dustproof member 8 is provided. The dustproof member 8 is an elastic member made of a sponge-like material such as urethane foam similarly to the first dustproof member 7, and is provided with a double-sided tape 9 adhered to a part of the lower surface and having adhesive properties on both surfaces. The dustproof member 8 is fixed to the bottom wall of the optical box 5, and the inner end of the dustproof member 8 is in contact with the side surface of the imaging lens 4 below the effective lens surface 4 a of the imaging lens 4.
Thus, the dustproof member 8 is provided with the imaging lens 4 and the optical box 5.
Are sealed from the side surfaces of the imaging lens 4 between the bottom walls of the imaging lens 4.

On the bottom wall of the optical box 5, a guide member 10 which engages with the outer end of the dustproof member 8 is provided upright, and on the side surface of the imaging lens 4, a restraining member 11 projects. This is configured so that the inner end of the dustproof member 8 is sandwiched between the dustproof member 8 and the bottom wall of the optical box 5 so as to be restrained.

The procedure for assembling the imaging lens 4 to the optical box 5 is as follows. First, the bottom surface of the imaging lens 4 is brought into contact with the pedestal 5b of the optical box 5, and is fixed using a pressing spring or an adhesive. Subsequently, the outer end of the dustproof member 8 is engaged with the guide member 10, and the bottom adjacent thereto is fixed to the bottom wall of the optical box 5 with double-sided tape 9, and then the inner end of the dustproof member 8 is compressed. Restraining member 11 protruding from imaging lens 4
Dive below. Thus, the dustproof member 8 is sandwiched between the bottom wall of the optical box 5 and the restraining member 11.

As shown in FIG. 3, the dustproof member 8 is a long member extending in the length direction of the imaging lens 4, and is made of a sponge-like elastic material as described above. It is easy to compress this and dive under the restraint member 11.

In addition, since the imaging lens 4 is fixed to the optical box 5 and then the dustproof member 8 is assembled, the dustproof member is fixed to the optical box before the imaging lens is assembled as in the conventional example. The work of assembling the imaging lens is simpler than that of the first embodiment.

Further, since the outer end of the dustproof member 8 is in contact with the guide 10 and the inner end is sunk under the restraining member 11, both ends of the dustproof member 8 are firmly fixed, and the dustproof member 8 is fixed.
The trouble that the edge of the end is turned up or twisted can be avoided. Further, in the step of transporting the scanning optical device after assembly, even if the end of the dustproof member 8 is slightly turned up as shown in FIG. There is no possibility that a gap is formed below the imaging lens 4 and the sealing effect is reduced.

According to this embodiment, a part of the dustproof member for sealing between the imaging lens and the bottom wall of the optical box is fixed to the bottom wall of the optical box with double-sided tape, and the restraining member protrudes from the imaging lens. With this configuration, the end of the dustproof member is restrained, so that the dustproof member can be firmly adhered to the bottom wall of the optical box. As a result, the sealing effect of the dustproof member is greatly improved, and there is no fear that the end of the dustproof member is turned or twisted during the transportation of the apparatus. Also,
Since the dust-proof member can be stably and firmly attached to the bottom wall of the optical box while being in close contact with the bottom wall of the optical box, the efficiency of assembling the dust-proof member is greatly improved.

As a result, the atmosphere around the rotary polygon mirror is maintained in a clean state, high-performance, long-term maintenance-free operation is possible, and an inexpensive, high-quality scanning optical device with low assembly costs is realized.

FIGS. 5 and 6 show a modification. This is because, in the molding process of the imaging lens 4, the dustproof member 8 is provided by using the ejector pin contact portion 4b provided to receive the ejector pin when the product is removed from the mold.
Are configured to restrain the ends of the. The ejector pin contact portion 4b is generally constituted by small projections arranged in a line in the length direction on the bottom of the imaging lens 4.

When the inner end of the dustproof member 8 is constrained to the bottom wall of the optical box 5 by utilizing the protrusions provided for another purpose as described above, when the constraining member is added to the imaging lens 4 There is an advantage that the design and the like of the imaging lens 4 are simplified as compared with the above.

FIGS. 7 and 8 show a scanning optical device according to the second embodiment. In this embodiment, in addition to a restricting member 31 protruding from the imaging lens 24, a second restricting member 32 is provided at an upper end of a guide member 30 erected on the bottom wall of the optical box 25. Both ends of the dustproof member 28 are sunk under the first and second restraining members 31 and 32, and these are placed in the optical box 2.
5, the dustproof member 28 can be assembled without using a double-sided tape or the like for fixing the dustproof member 28 to the bottom wall of the optical box 25. Since the semiconductor laser 1, the rotary polygon mirror 2, the folding mirror 3, and the like are the same as those in the first embodiment, they are denoted by the same reference numerals, and description thereof is omitted.

The dustproof member 28 is assembled by using a pressing spring or an adhesive in the same manner as in the first embodiment.
Is fixed to the pedestal 25b of the optical box 25, the outer end of the dustproof member 28 is sunk under the second restraint member 32, and the inner end of the dustproof member 28 is sunk under the first restraint member 31. This is done by letting

The advantage that the assembling process of the dustproof member is further simplified, and the assembling cost and the like can be greatly reduced is added.

FIG. 9 shows a scanning optical device according to a third embodiment, which comprises a light source unit in which a semiconductor laser 41 and a collimator lens are unitized, and a laser beam of a parallel light beam which is a light beam generated from the unit. It has a rotating polygon mirror 42 as scanning means for deflecting and scanning the light L _2, and an image forming lens 44 for forming the scanning light via a folding mirror 43 onto a photosensitive member on the surface of a rotating drum at an image forming position.
The rotating polygon mirror 42 and the imaging lens 44 are housed in an optical box 45, and the light source unit is assembled on a side wall of the optical box 45.

The upper opening of the optical box 45 is closed by a lid member 46 after all necessary components are incorporated in the optical box 45, as shown in FIG. The bottom wall of the optical box 45 is provided with a window 45a for taking out the scanning light of the rotating polygon mirror 42 toward an external rotating drum.

The laser light L ₂ generated from the semiconductor laser 41 of the light source unit is collimated by a collimator lens, condensed linearly on a reflection surface of a rotary polygon mirror 42 by a cylindrical lens 41 a, and rotated by driving a motor 42 a. Deflection scanning is performed by the high-speed rotation of the polygon mirror 42. The scanning light obtained in this manner is applied to the imaging lens 44.
Is reflected downward by the turning mirror 43,
It is taken out from the window 45a of the optical box 45 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 42 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 41. After receiving the trigger signal, the semiconductor laser 41 starts write modulation based on image information transmitted from the host computer.

The image forming lens 44 has a so-called fθ function for forming the scanning light of the rotary polygon mirror 42 on the photosensitive member and making the scanning speed of the point image obtained as a result uniform. Optical box 45
Fixed to

That is, with respect to a pair of positioning members 45 b provided in the optical box 45, the butting reference surface 4, which is a pair of positioning portions formed at both ends of the imaging lens 44, is provided.
4a, the direction of the optical axis of the imaging lens 44 (X
In the height direction (Z-axis direction) of the imaging lens 44, the bottom surface of the imaging lens 44 is provided on the bottom wall of the optical box 45. The three pedestals 45c are brought into contact with each other and positioned, and pressed using a holding spring or the like. Alternatively, the imaging lens 44 is bonded to each pedestal 45c using an adhesive. In this manner, the imaging lens 44 is assembled to the optical box 45.

The inside of the optical box 45 is almost sealed by closing the upper opening with the lid member 46 as described above. However, since the outside air entering the optical box 45 from the window 45a for taking out the scanning light or the like is used. In addition, there is a problem that the reflection surface of the rotary polygon mirror 42 is contaminated. In recent years, higher performance and higher speed of the image forming apparatus have been desired, and the rotational speed of the rotary polygon mirror 42 may be 30,000 rpm or more.

When the rotary polygon mirror 42 rotates at a high speed, a large negative pressure is generated inside the optical box 45, and a large amount of outside air is sucked into the atmosphere A ₂ around the rotary polygon mirror 42.
Becomes dirty. When the rotating polygon mirror 42 rotates, an air vortex is generated at the top and the like, and when such an air flow collides with the reflecting surface, the floating dust of air adheres to the reflecting surface and lowers the reflectance. This causes inconveniences such as deterioration of the image quality of the image forming apparatus and inability to detect a trigger signal.

The air outside the optical box 45 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 45 and contaminating the rotary polygon mirror 42 are extremely important in promoting a high-speed scanning optical apparatus.

Therefore, a sponge-like dustproof member 47 such as urethane foam is provided between the top of the imaging lens 44 and the lid member 46.
Sealed by devising to prevent the atmosphere A ₂ surrounding from being contaminated of the rotary polygonal mirror 42 is made.

The height of each pedestal 45c that contacts the bottom surface of the imaging lens 44 is generally about 0.3 to 0.5 mm, and is formed between the imaging lens 44 and the bottom wall of the optical box 45. and air entering the dirty from the clearance portion, since the atmosphere a ₂ around the rotary polygonal mirror 42 may be contaminated, for closing the gap between the bottom wall and the imaging lens 44 of the optical box 45 A second dustproof member 48 is provided. The dustproof member 48 is an elastic member made of a sponge-like material such as urethane foam similarly to the first dustproof member 47, and is provided with a double-sided tape 49 having adhesive properties on both surfaces attached to a part of the lower surface thereof. The inner end of the dustproof member 48 is fixed to the bottom wall of the optical box 45,
The elastically compressed state is brought into contact with the side surface of the imaging lens 44 below the effective lens surface of the imaging lens 44.
Since this side surface is located on the opposite side of the abutting reference surface 44a, the compression force of the dustproof member 48 presses the imaging lens 44 against the positioning member 45b of the optical box 45, and the imaging lens 44 is useful for positioning in the optical axis direction and the θ axis direction. The dustproof member 48 is thus constructed
The opening end of the gap between the imaging lens 44 and the bottom wall of the optical box 45 is sealed from the side surface of the imaging lens 44.

The procedure for assembling the imaging lens 44 to the optical box 45 is as follows. The abutment reference surface 44a of the imaging lens 44 contacts the positioning member 45b, and the bottom surface of the imaging lens 44 contacts the pedestal 45c of the optical box 45, and is fixed using a pressing spring or an adhesive. Subsequently, the dustproof member 48
Is fixed to the bottom wall of the optical box 45 with a double-sided tape 49, and the dustproof member 48 is pressed against the side surface of the imaging lens 44 while being compressed. Thus, the dustproof member 4
8 is assembled in the optical box 45.

As shown in FIG. 11, the dustproof member 48 is a long member extending in the length direction of the imaging lens 44, and is made of a sponge-like elastic material as described above. It is easy to compress this and bring it into close contact with the side surface of the imaging lens 44. Further, the compressive force of the dustproof member 48 causes the imaging lens 44 to move the positioning member 4 of the optical box 45.
Since it acts in the direction of pressing on 5b, it functions to stabilize the positioning of the imaging lens 44.

Instead of fixing the imaging lens 44 to the optical box 45 and attaching the dustproof member 48, the dustproof member 48 is attached to the optical box 45 before attaching the imaging lens 44.
May be employed. In this case, the imaging lens 44 is moved to the optical box 45 by using the compression force of the dustproof member 48.
Since it is possible to temporarily fix, a tool and a trouble for temporary holding can be omitted.

FIG. 12 shows a modification of the third embodiment. On the bottom wall of the optical box 45, a restraining member 50, which is a restraining means for engaging with and restraining the outer end of the dustproof member 48, is provided upright. The dust-proof member 48 is sandwiched between the image forming lens 44 and the image-forming lens 44 so as to be restrained.

The procedure for assembling the imaging lens 44 to the optical box 45 is as follows. The bottom surface of the imaging lens 44 abuts against the pedestal 45c of the optical box 45, and is fixed using a pressing spring or an adhesive.
, And a portion adjacent thereto is fixed to the bottom wall of the optical box 45 by the double-sided tape 49. Next, the dustproof member 4
8 comes into contact with the side surface of the imaging lens 44 while compressing the inner end. Thus, the dustproof member 48 is fixed to the bottom wall of the optical box 45.

[0070]

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

The work of assembling the dustproof member for sealing the gap between the bottom wall of the optical box and the imaging lens can be simplified and the sealing effect can be improved. Also, the dustproof member can be firmly adhered to the bottom wall of the optical box so as to be firmly fixed so that the dustproof member after the assembly is not turned or twisted.

As a result, a dustproof effect for preventing contamination of the rotary polygon mirror is greatly improved, and a high-performance and low-cost scanning optical device which 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]

FIG. 1 is a schematic plan view showing a scanning optical device according to a first embodiment.

FIG. 2 is a sectional view showing the apparatus of FIG. 1;

FIG. 3 is a plan view showing only a second dustproof member of the apparatus of FIG. 1;

FIG. 4 is a sectional view showing only an imaging lens and a second dustproof member of the apparatus of FIG. 1;

FIG. 5 is a partial plan view showing a modification of the first embodiment.

FIG. 6 is a partial sectional view showing the apparatus of FIG. 5;

FIG. 7 is a schematic plan view showing a scanning optical device according to a second embodiment.

FIG. 8 is a sectional view showing the apparatus of FIG. 7;

FIG. 9 is a schematic plan view showing a scanning optical device according to a third embodiment.

FIG. 10 is a sectional view showing the apparatus of FIG. 9;

FIG. 11 is a plan view showing only a dustproof member of the apparatus of FIG. 9;

FIG. 12 is a schematic plan view showing a modification of the third embodiment.

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

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

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

FIG. 16 is a schematic plan view showing another conventional example.

FIG. 17 is a sectional view showing the device of FIG. 16;

FIG. 18 is a schematic plan view showing still another conventional example.

[Explanation of symbols]

 1,41 Semiconductor laser 2,42 Rotating polygon mirror 3,43 Folding mirror 4,24,44 Imaging lens 5,25,45 Optical box 7,8,28,47,48 Dustproof member 9,49 Double-sided tape 10,30 Guide member 11, 31, 32, 50 Restraint member

Claims (8)

[Claims] A scanning means for deflecting and scanning a light beam to convert the light beam into scanning light; an imaging lens disposed in an optical path of the scanning light; and an optical box accommodating the imaging lens and the scanning means. A dustproof member for closing a gap between the bottom wall of the optical box and the imaging lens, wherein the imaging lens restrains one end of the dustproof member to the bottom wall of the optical box. A scanning optical device comprising a restraining member. 2. The scanning optical device according to claim 1, wherein the optical box includes a guide member that engages with the other end of the dustproof member. 3. The scanning optical system according to claim 2, wherein the guide member of the optical box includes a second restricting member for restricting the other end of the dustproof member to the bottom wall of the optical box. apparatus. 4. A scanning means for deflecting and scanning a light beam to convert it into scanning light, an imaging lens provided in an optical path of the scanning light, and an optical box for housing the imaging lens and the scanning means. A dustproof member for closing a gap between the bottom wall of the optical box and the imaging lens, the dustproof member being in contact with a side surface of the imaging lens to seal an opening end of the gap. A scanning optical device characterized by being configured as described above. 5. The scanning device according to claim 4, wherein a positioning portion for positioning the imaging lens with respect to the optical box is provided on a side surface opposite to a side surface on which the dustproof member contacts. Optical device. 6. The scanning optical device according to claim 4, wherein the dustproof member is in contact with a lower portion of the effective lens surface of the imaging lens. 7. The dustproof member according to claim 4, wherein the dustproof member is an elastic member elastically pressed against a side surface of the imaging lens.
7. The scanning optical device according to any one of claims 6 to 6. 8. The scanning optical device according to claim 4, wherein the optical box includes a restraining means for restraining the dust-proof member abutting on the imaging lens.