JPH1048557A - Scanning optical device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent an imaging lens from being inverted. A laser beam generated from a light source unit is deflected and scanned by a rotary polygon mirror, and is imaged on a photosensitive member (not shown) by an imaging lens. The imaging lens 4 is a plastic lens integrally formed of a synthetic resin, and has a gate 42 at one end. Imaging lens 4
When an error occurs in assembling the lens to the optical box 5, the gate 42 of the imaging lens 4 is engaged with the interference pin 5 b provided on the bottom wall of the optical box 5 to prevent the assembling.

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 Generally, a scanning optical device used for an image forming apparatus such as a laser beam printer or a laser facsimile is a light source unit 1 having a semiconductor laser 101a and a collimator lens 101b as a unit as shown in FIG.
01, a rotary polygon mirror 102 for deflecting and scanning the laser beam L ₀ of the parallel light beam generated therefrom, the imaging lens is imaged on the photoconductor surface of the rotary drum (not shown) via a mirror 103 folding the scanning light 104 Etc. The rotating polygon mirror 102 and the imaging lens 104 are housed 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 photoconductor on the rotating drum forms an electrostatic latent image by 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.

The lens holder of the cylindrical lens 101c is integrated with a BD lens 107b for separating the scanning light of the rotary polygon mirror 102 at the end in the main scanning direction and introducing the scanning light to the BD sensor 107a. 101a starts the write modulation by the output of the BD sensor 107a.

The imaging lens 104 is a compound lens having a so-called fθ function for making the scanning speed of the point image formed on the photosensitive member uniform as described above, and is provided with respect to the optical path of the scanning light of the rotary polygon mirror 102. Optical box 10
5 is fixed by a known method such as bonding.

The imaging lens 104 is an inexpensive plastic lens. A positioning projection 104 a is integrally formed on the bottom of the imaging lens 104, and is formed between a pair of positioning pins 105 a provided on the bottom wall of the optical box 105. Engagement allows easy positioning in the main scanning direction. By using such a plastic lens, it is possible to realize a scanning optical device whose material cost is low and whose assembly process is simple.

[0008]

However, according to the above prior art, the imaging lens has an aspherical shape which is asymmetrical with respect to the optical axis (X axis), but is asymmetrical in appearance. It is not easy to recognize that there is, and when assembling in an optical box, assembling errors such as inverting and assembling the imaging lens upside down (reversing) frequently occur. Further, even if the imaging lens is symmetrical, if the bottom surface of the imaging lens is configured to be used as a contact surface for positioning in the height direction (Z-axis direction), an image is formed. Since the reverse mounting of the lens results in significantly impairing the positioning accuracy of the imaging lens, it is necessary to confirm the upper and lower sides of the imaging lens before assembling the same.

As described above, if the imaging lens is easily turned upside down, the assembling work of the scanning optical device is complicated, and it becomes a major obstacle to automatic assembling by a robot.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned unresolved problems of the related art, and has as its object to provide a scanning optical device which can surely prevent an assembling error due to reverse mounting of an imaging lens. It is the purpose.

[0011]

In order to achieve the above object, a scanning optical apparatus according to the present invention comprises a scanning unit, an imaging lens for forming an image of the scanning light on a photosensitive member, and a housing for supporting the imaging lens. And interference means configured to interfere with the projection of the imaging lens when an error in assembling the imaging lens to the housing occurs, wherein the projection of the imaging lens is It is a gate when the image lens is formed.

It is preferable that the projection of the imaging lens protrudes from the longitudinal end of the imaging lens.

[0013]

[Function] When the imaging lens is molded of synthetic resin or the like,
A gate is left at the end of the imaging lens in the length direction or the like. This is used to prevent assembly errors such as reverse mounting of the imaging lens without cutting it. That is, the gate is engaged with an interference pin or the like of the housing to prevent the image forming lens from being reversely mounted.

Since the gate necessary for molding the imaging lens is used as it is as the projection for preventing the reverse mounting, the reverse mounting of the imaging lens can be reliably prevented and the shape of the imaging lens becomes complicated. There is no fear. As a result, the assembly process is simple and suitable for automation of assembly.
The cost of a single component of the imaging lens is also low, so that an extremely inexpensive scanning optical device can be realized.

[0015]

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 semiconductor laser 1a and a collimator lens 1.
a light source unit 1 unitized b, or rotary polygon mirror 2 is a scanning means for deflecting and scanning the laser beam L ₁ is a light of the parallel light beam generated from the light source unit 1, thereby deflecting the scanned scanning light Has an image forming lens 4 for forming an image on a photoreceptor on the surface of a rotating drum through a mirror 3, and the rotating polygon mirror 2 and the image forming lens 4 are provided in an optical box 5 serving as a housing.
The light source unit 1 is mounted on a side wall of the optical box 5 or the like.

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 by the turning mirror 3 and is taken out of 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 imaging lens 4 has a so-called fθ function for correcting the distortion of the point image formed on the photosensitive member as described above, and is an aspherical lens asymmetrical with respect to its optical axis (X axis). Which is a plastic lens integrally formed of plastic.

As shown in FIG. 2, the bottom of the imaging lens 4 is provided with flanges 4a projecting from both sides thereof.
A similar flange 4b is provided at the top of the imaging lens 4, 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 flange portions 4a at the bottom of the imaging lens 4 has a projection 41 projecting from the longitudinal center of the imaging lens 4 along the optical axis thereof. A pair of positioning pins 5 protruding from the bottom wall of the optical box 5 during assembly
a for engaging the imaging lens 4 in the main scanning direction.

At one end in the length direction (Y-axis direction) of the imaging lens 4, a gate 42, which is a protrusion left when the imaging lens 4 is integrally formed of plastic, protrudes. In the process of assembling the imaging lens 4 with respect to the above, when the imaging lens 4 is properly lowered and assembled as shown by the arrow A without being reversed, as shown in FIG. On the other side of the interference pin 5b, which is interference means protruding from the bottom wall of the optical box 5, and without interfering with the interference pin 5b, the image forming lens 4 is reversed as shown in FIG. Sometimes gate 4
2 engages with the interference pin 5b to prevent the imaging lens 4 from being assembled.

The bottom surface 43 of the imaging lens 4 is finished to a high degree of flatness as a horizontal reference surface for positioning, and is brought into contact with a pair of seating surfaces 5c protruding from the bottom wall of the optical box 5 to form the imaging lens. 4 is used for positioning in the sub-scanning direction. Further, a pair of vertical reference surfaces 44 perpendicular to the optical axis are provided on both side edges of the imaging lens 4, and these are brought into contact with a positioning member 5 d integral with the side wall of the optical box 5 to form an image. The positioning of the lens 4 in the optical axis direction is performed (see FIG. 2).

That is, the imaging lens 4 with respect to the optical box 5
In the assembling, the projection 41 of the imaging lens 4 is engaged between the positioning pins 5a on the bottom wall of the optical box 5, and the horizontal reference plane of the bottom surface 43 of the imaging lens 4 is attached to the seating surface 5c of the optical box. By contacting the vertical reference surface 44 of the imaging lens 4 with the positioning member 5d on the side wall of the optical box 5, the positioning is performed in the main scanning direction, the sub-scanning direction, and the optical axis direction. Alternatively, an imaging lens 4 using a spring or the like
Is fixed to the bottom wall of the optical box 5. In the process of assembling the scanning optical device, it is preferable to strictly control the positions of the imaging lens 4 in the main scanning direction, the sub-scanning direction, and the optical axis direction with respect to the scanning light of the rotary polygon mirror 2 in order to obtain a good image. It is extremely important to get.

As described above, the image forming lens is a plastic lens, and is configured to prevent the image forming lens from being inverted by using a gate when the image forming lens is molded. In addition to being able to reliably prevent the imaging lens from being inverted, the addition of the advantage of reducing the cost of individual imaging lens components is unnecessary, since there is no need to cut off the gate during the imaging lens manufacturing process. Is done.

In the case where a projection for preventing reverse attachment is newly provided on the imaging lens without using the gate at the time of molding, not only a step of separating the gate is required, but also a step of separating the gate is required.
Since the shape of the forming mold of the imaging lens becomes complicated, there is a possibility that the cost of a single component of the imaging lens will increase significantly.

It is desirable that the gate position of the imaging lens is provided as far as possible from the lens surface (effective portion) so as not to affect the optical performance of the imaging lens. Therefore, it is optimal to provide at one end in the length direction of the imaging lens as in the present embodiment. However, without being limited to this, for example, as shown in FIG. A gate 52 may be provided on the flange 14a,
As shown in FIG. 5, a gate 62 is provided on the top of the imaging lens 24.
Can also be provided.

[0027]

Since the present invention is configured as described above, the following effects can be obtained.

The assembling error of the imaging lens can be surely prevented, and the operation of separating the gate can be omitted by using a gate for forming the imaging lens in the protrusion for preventing the assembling error. The manufacturing process of the imaging lens can be greatly simplified. As a result, the cost of a single component of the imaging lens can be reduced, the simplification and speeding up of the assembly process of the scanning optical device can be promoted, and an extremely inexpensive and high-performance scanning optical device can be realized.

[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 a state immediately before assembling an imaging lens of the apparatus of FIG. 1 into an optical box.

FIG. 3 is a diagram illustrating a case where the imaging lens of the apparatus of FIG. 1 is properly assembled and a case where the imaging lens is reversed.

FIG. 4 is a perspective view showing an imaging lens according to a modification.

FIG. 5 is a perspective view showing an imaging lens according to another modification.

FIG. 6 shows a scanning optical device according to a conventional example,
(A) is a schematic plan view, (b) is a perspective view showing only an imaging lens.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source unit 2 Rotating polygon mirror 3 Folding mirror 4,14,24 Imaging lens 5 Optical box 5b Interference pin 41 Projection part 42,52,62 Gate

Claims (3)

[Claims] An imaging lens for forming an image of the scanning light on a photoreceptor; a housing for supporting the imaging means; and an imaging lens when an error in assembling the imaging lens to the housing occurs. A scanning optical apparatus, comprising: an interference unit configured to interfere with a projection of an image lens, wherein the projection of the imaging lens is a gate when the imaging lens is molded. 2. The scanning optical device according to claim 1, wherein a projection of the imaging lens projects from an end in a longitudinal direction of the imaging lens. 3. The scanning optical device according to claim 1, wherein the imaging lens is a plastic lens.