JPH10268222A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce manufacturing cost by using the same optical box for a kind of device having different number of lenses. SOLUTION: A laser beam L1 generated from a semiconductor laser 1a is deflected/scanned by a rotating polygon mirror 2 and forms the image on the photosensitive body of a rotating drum through an image forming lens 4 and a folding mirror 3. An optical box has a first positioning part composed of positioning pins 5a, 5b and positioning members 5c, 5d and a second positioning part composed of positioning pins 15a, 15b and positioning members 15c, 15d and the image forming lens 4 is assembled in the first positioning part when a lens system is composed of one lens. When the device is a high grade device using a lens system composed of two lenses, the lenses are assembled in the first and second positioning parts, respectively.

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.

FIG. 5 shows a scanning optical device according to a conventional example, which comprises a light source unit 101 in which a semiconductor laser 101a and a collimator lens 101b are unitized.
It has a rotating polygon mirror 102 for deflecting and scanning the laser light L ₀ of the parallel light beam generated from this, an imaging lens 104 for forming the scanning light on a photosensitive member on the surface of a rotating drum (not shown) via a folding mirror 103, and the like. . Rotating polygon mirror 10
2 and the imaging lens 104 are accommodated in an optical box 105, and the light source unit 101 is assembled 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 a lid (not shown). The bottom wall of the optical box 105 is provided with a window 106 for taking out the scanning light of the rotating polygon mirror 102 toward an external rotating drum.

The semiconductor laser 101 of the light source unit 101
The laser light L ₀ generated from the laser beam L
1b, the cylindrical lens 101
c, the light is condensed linearly on the reflection surface 102a of the rotary polygon mirror 102, passes through the imaging lens 104,
3 is reflected downward by the window 106 of the optical box 105.
From the rotating drum. The scanning light imaged on the photoreceptor on the rotating drum in this manner forms an electrostatic latent image with the main scanning in the Y-axis direction by the rotating polygon mirror 102 and the sub-scanning in the Z-axis direction by the rotation of the rotating drum. Form.

The scanning light of the rotary polygon mirror 102 is separated at the end in the main scanning direction into the lens holder of the cylindrical lens 101c, and the BD sensor 1 is used as a trigger signal.
A BD lens 107b for introducing the light into the lens 07a is integrated. The semiconductor laser 101a is a BD sensor 107a
The write modulation is started by the output of.

The imaging lens 104 is a compound 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. Then, it is fixed to the optical box 105 after being strictly positioned as follows with respect to the optical path of the scanning light.

In other words, the center projection 141 of the imaging lens 104, the reference surface 142, and the center surface 142, relative to positioning means such as positioning pins 105a and 105b and abutting members 105c and 105d provided on the bottom surface of the optical box 105 and partition walls and the like. By engaging or abutting positioning portions such as 143, positioning in the length direction (Y-axis direction) of the imaging lens 104,
The positioning in the optical axis direction (X-axis direction), the adjustment of the rotation position, and the like are strictly performed, and then the optical box 105 is fixed to the optical box 105 using a pressing spring or the like.

The incident position at which the laser light L ₀ generated from the semiconductor laser 101 a is incident on the reflecting surface 102 a of the rotary polygon mirror 102 is determined by the rotation angle of the rotating polygon mirror 102, that is, between the laser beam L ₀ and the reflecting surface 102 a. Since the angle varies with the angle, the partial magnification of the point image on the photoconductor in the main scanning direction becomes non-uniform. Therefore, magnification correction is performed by shifting the center (optical axis) P of the imaging lens 104 in the length direction from the center (image center) O of the writing width of the scanning light of the rotary polygon mirror 102 by ΔX, thereby performing image correction. Avoid distortion and the like.

[0010]

However, according to the above-mentioned conventional technology, a low-priced and widely used machine having a relatively low printing density and an advanced model having a high printing density and a high definition have been developed.
Since lens systems with different optical specifications are required, optical boxes must be manufactured individually for each model, even if the exterior of the optical box and the deflecting unit such as a rotary polygon mirror are the same. Is an unsolved problem.

In general, for a popular device having a relatively large spot image size, that is, a spot diameter formed by forming scanning light, a so-called single lens configuration using only one inexpensive plastic lens as the imaging lens is used. Although a lens system is employed, in the case of a high-end model having a small spot diameter, a two-lens lens system using two plastic lenses is required in order to realize higher-precision optical specifications. Therefore, an optical box for a popular machine configured to incorporate a single-lens lens system cannot be used as it is for a high-end model requiring a two-lens lens system. This results in increased manufacturing costs for the scanning optical device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unsolved problems of the conventional technology, and is applicable to a case where an optical box having the same structure is widely used for a model having a different required number of lenses such as an imaging lens. It is an object of the present invention to provide a scanning optical device that can significantly reduce manufacturing costs.

[0013]

In order to achieve the above object, a scanning optical apparatus according to the present invention comprises a scanning means for deflecting and scanning a light beam generated from a light source and an image of the scanning light on a photosensitive member. A lens system, and an optical box that houses the lens system and the scanning unit, wherein the optical box includes a lens assembling unit capable of assembling lenses equal to or more than the number of lenses of the lens system. I do.

Preferably, the lens assembling means is capable of assembling the respective lenses so that the imaging positions of the lens systems are the same even if the number of lenses is different.

[0015]

The optical box having the same configuration can be used in a wide range even if the number of lenses in the lens system is different from each other, as long as the number is smaller than the number that can be assembled in the lens assembling means. For example,
A relatively inexpensive spreader having a single-lens lens system;
By using the same optical box in a high-definition high-end machine that requires a lens system having a single lens configuration, the cost of parts of the optical box can be reduced, and the manufacturing cost of the scanning optical device can be significantly reduced.

[0016]

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

FIG. 1 shows a scanning optical device according to one embodiment, which comprises a light source unit 1 in which a semiconductor laser 1a and a collimator lens 1b are unitized as a light source, and a parallel light beam which is a light beam generated from the unit. Laser light L
_A rotary polygon mirror 2 which is a scanning means for deflecting and scanning ₁ and an imaging lens 4 which is a lens for forming an image of the scanning light on a photoreceptor on the surface S ₁ of a rotary drum which is an image forming position via a return mirror 3. Lens system. The rotating polygon mirror 2 and the imaging lens 4 are housed in an optical box 5, and the light source unit 1 is assembled on a side wall of the optical box 5.

The upper opening of the optical box 5 is closed by a lid (not shown) after all necessary parts are incorporated in the optical box 5. The bottom wall of the optical box 5 is provided with a window 6 for taking out the scanning light of the rotary polygon mirror 2 toward an external rotary drum.

The light source unit laser beam L ₁ generated from the semiconductor laser 1a of 1 is collimated by the collimator lens 1b, it is linearly condensed on the reflecting surface 2a of the rotary polygon mirror 2 by the cylindrical lens 1c, an imaging lens 4, the light is reflected downward by the turning mirror 3 and taken out from the window 6 of the optical box 5 toward the rotating drum. The scanning light imaged on the photoreceptor on the rotating drum forms an electrostatic latent image by the main scanning in the Y-axis direction by the rotating polygon mirror 2 and the sub-scanning in the Z-axis direction by the rotation of the rotating drum.

The lens holder of the cylindrical lens 1c is integrated with a BD lens 7b for separating the scanning light of the rotary polygon mirror 2 at the end in the main scanning direction and introducing it to the BD sensor 7a as a trigger signal. . The semiconductor laser 1a starts writing modulation by the output of the BD sensor 7a.

The imaging lens 4 is a composite lens having a so-called fθ function for forming the scanning light of the rotary polygon mirror 2 on the photosensitive member as described above and making the scanning speed of the resulting point image uniform. Then, it is fixed to the optical box 5 after being strictly positioned as follows with respect to the optical path of the scanning light.

As shown in FIGS. 2 and 3, the bottom of the imaging lens 4 is provided with flanges 4a projecting from both sides, and the top of the imaging lens 4 is also provided with a similar flange 4b.
Is provided, and a lens surface (effective portion) 4c of the imaging lens is disposed between the bottom and top flanges 4a and 4b.
One of the bottom flanges 4a of the imaging lens 4 has a central projection 41 protruding from the longitudinal center of the imaging lens 4 along its optical axis. At this time, it is used for positioning the imaging lens 4 in the main scanning direction (Y-axis direction) by engaging between a pair of positioning pins 5a and 5b protruding from the bottom wall of the optical box 5.

The bottom surface of the imaging lens 4 is finished to a high flatness as a horizontal reference surface for positioning, and is brought into contact with a seating surface provided on the bottom wall of the optical box 5 to form the imaging lens. 4 is used for positioning in the height direction (Z-axis direction).
Further, on both side edges of the imaging lens 4, a pair of reference surfaces 42 and 43 perpendicular to the optical axis are provided,
The positioning of the imaging lens 4 in the optical axis direction (X-axis direction) and the adjustment of the rotational position are performed by contacting the positioning members 5c and 5d integral with the side wall of the imaging lens 4.

That is, the imaging lens 4 with respect to the optical box 5
In the assembling, the central projection 41 of the imaging lens 4 is engaged between the positioning pins 5a and 5b on the bottom wall of the optical box 5, the bottom surface of the imaging lens 4 is brought into contact with the seating surface of the optical box, and By contacting the reference surfaces 42 and 43 of the imaging lens 4 with the positioning members 5c and 5d on the side wall of the optical box 5, positioning in each direction is performed, and then the imaging lens 4 is pressed using a pressing spring or the like. It is fixed to the optical box 5. In the assembling process of the scanning optical device, the positioning unit 5
Strict control of the relative position of the imaging lens 4 with respect to the scanning light of the rotating polygon mirror 2 using a to 5d is extremely important for obtaining a good image.

The incident position at which the laser beam L ₁ generated from the semiconductor laser 1 a enters the reflecting surface 2 a of the rotary polygon mirror 2 depends on the rotation angle of the rotary polygon mirror 2, that is, the laser beam L _1.
Of the point image on the photosensitive member in the main scanning direction becomes non-uniform. Thus, as shown in FIG. 3, the center (optical axis) P in the length direction of the imaging lens 4 is shifted by ΔX from the center (image center) O of the writing width of the scanning light of the rotary polygon mirror 2. Perform magnification correction to avoid image distortion and the like.

On the bottom wall of the optical box 5, second positioning pins 15a and 15b are provided upright along the optical path of the scanning light of the rotary polygon mirror 2, and on the side wall of the optical box 5, the second positioning pins 15a and 15b are provided. Positioning members 15c and 15d are provided. The second positioning pins 15a, 15b and the second positioning members 15c,
Reference numeral 15d denotes a second imaging lens 24 similar to the first positioning pins 5a and 5b and the first positioning members 5c and 5d.
(See FIG. 4) are second positioning portions for positioning and assembling the optical box 5 with the first positioning portions 5a-5.
Together with d, they constitute lens assembling means.
Since the apparatus shown in FIG. 1 uses a single lens system, the second positioning pins 15a and 15b and the second positioning members 15c and 15d are not used.

In a general-purpose machine having a relatively low printing density equipped with a single-lens lens system, the remaining optical components are placed in an optical box while the positioning pins and positioning members of the second lens are not used. To complete the assembly of the scanning optical device.

When a high-definition high-end model requires a two-lens lens system, as shown in FIG.
The first imaging lens 14 is positioned using the first positioning portions 5a to 5d of the same optical box 5 as described above and fixed by a pressing spring or the like, and similarly, the second positioning portion 15a
15d, the second imaging lens 24 is positioned and fixed.

The effective part of the first imaging lens 14 in the two-lens lens system has a different shape from the effective part of the imaging lens 4 in the one-lens lens system shown in FIG. Fourteen central projections 51, reference surfaces 52, 53, etc.
Needless to say, when these are positioned at the first positioning portions 5a to 5d, the imaging position of the imaging lens 14 is the same as that of the imaging lens 4.

[0030]

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

By using the optical box having the same configuration for a wide range of models having different numbers of lenses such as imaging lenses, the cost of parts of the optical box can be reduced. As a result, the manufacturing cost of the scanning optical device can be greatly reduced, and the cost of the image forming apparatus can be greatly reduced.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing only an imaging lens of the apparatus of FIG. 1;

FIG. 3 is a plan view showing the imaging lens of FIG. 2;

FIG. 4 is a schematic plan view showing a case where two imaging lenses are assembled to the apparatus of FIG. 1;

FIG. 5 is a schematic plan view showing a scanning optical device according to a conventional example.

[Explanation of symbols]

 Reference Signs List 1 light source unit 2 rotating polygon mirror 3 folding mirror 4, 14, 24 imaging lens 5 optical box 5a, 5b, 15a, 15b positioning pin 5c, 5d, 15c, 15d positioning member

Claims (4)

[Claims] A scanning unit that deflects and scans a light beam generated from a light source, a lens system that forms an image of the scanning light on a photoconductor, and an optical box that houses the lens system and the scanning unit. A scanning optical apparatus, wherein the optical box is provided with lens assembling means capable of assembling more than the number of lenses of the lens system. 2. The lens assembling means as claimed in claim 1, wherein said lens assembling means is capable of assembling each lens so that the imaging position of the lens system is the same even when the number of lenses is different.
The scanning optical device according to claim 1. 3. The optical box is applicable to both a model having a two-lens system having two lenses and a model having a single-lens system having one lens. The scanning optical device according to claim 1, wherein the scanning optical device is provided. 4. The lens assembling means according to claim 1, wherein said lens assembling means is configured to assemble said lenses with the optical axis of each lens shifted by a predetermined amount from the center of the image. The scanning optical device according to claim 1.