JP3408070B2 - Scanning optical device - Google Patents

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 in an image forming apparatus such as a laser beam printer or 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 generally has a light source unit 1 in which a semiconductor laser 101a and a collimator lens 101b are unitized as shown in FIG.
01, a rotary polygon mirror 102 for deflecting and scanning the parallel light flux laser light L ₀ generated therefrom, and an imaging lens 104 for forming an image of the scanning light on a photoconductor on the surface of a rotary drum (not shown) via a folding mirror 103. And so on. The rotary polygon mirror 102 and the imaging lens 104 are housed in the optical box 105, and the light source unit 101 is mounted on the side wall of the optical box 105.

The upper opening of the optical box 105 is the optical box 105.
It is closed by a lid (not shown) after incorporating all the necessary parts therein. A window 106 is provided on the bottom wall of the optical box 105 to take out the scanning light of the rotary polygon mirror 102 toward an external rotary drum.

Semiconductor laser 101 of light source unit 101
The laser light L ₀ generated from a is collimator lens 10
Cylindrical lens 101 collimated by 1b
The light is linearly condensed on the reflecting surface 102a of the rotary polygon mirror 102 by c, passes through the imaging lens 104, and then the folding mirror 10 is moved.
And the window 106 of the optical box 105.
To the rotating drum. The scanning light imaged on the photoconductor on the rotary drum in this manner forms an electrostatic latent image by main scanning in the Y-axis direction by the rotary polygon mirror 102 and sub-scanning in the Z-axis direction by the rotation of the rotary 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 it into the BD sensor 107a. 101a starts write modulation by the output of the BD sensor 107a.

The image forming 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 directed 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 adhesion.

The image forming lens 104 is an inexpensive plastic lens, and a projection 104a for positioning is integrally formed on the bottom of the lens, and the projection 104a is formed between a pair of positioning pins 105a provided upright on the bottom wall of the optical box 105. By engaging with each other, the positioning in the main scanning direction can be easily performed. By using such a plastic lens, it is possible to realize a scanning optical device which has a low material cost and a simple assembly process.

[0008]

However, according to the above-mentioned conventional technique, the imaging lens has an aspherical shape which is bilaterally asymmetric with respect to its optical axis (X axis), but is asymmetric in appearance. It is not easy to recognize that there is something, and there are many assembly mistakes in which the imaging lens is turned upside down when it is mounted in the optical box (reverse mounting). Further, even if the imaging lens is bilaterally symmetric, 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), the imaging is performed. Since the reverse mounting of the lens results in a significant loss of the positioning accuracy of the imaging lens, it is still necessary to confirm the upper and lower sides of the imaging lens before assembling.

As described above, if the imaging lens is easily mounted in the opposite direction, the assembling work of the scanning optical device is complicated and becomes a major obstacle to automatic assembly by the robot.

The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and it is an object of the present invention to provide a scanning optical device capable of reliably preventing an assembly error due to the reverse mounting of the imaging lens. It is intended.

[0011]

In order to achieve the above object, a scanning optical device of the present invention comprises a scanning means, an imaging lens for forming an image of the scanning light on a photoconductor, and a casing for supporting the imaging lens. An interfering unit configured to interfere with a protruding portion of the imaging lens when an assembly error of the imaging lens with respect to the housing occurs, and the protruding portion of the imaging lens has It is a gate when the image lens is molded.

It is preferable that the projecting portion of the imaging lens projects from the end portion in the length direction of the imaging lens.

[0013]

[Function] When the imaging lens is molded with synthetic resin,
Gates are left at the ends of the imaging lens in the length direction. This is used to prevent assembly mistakes such as reverse mounting of the imaging lens without cutting it. That is, when it is attempted to reverse the imaging lens, the gate is engaged with the interference pin or the like of the housing to prevent the reverse mounting.

Since the gate necessary for molding the imaging lens is used as it is as a protrusion for preventing reverse mounting, 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 automated assembly.
The cost of the individual parts of the imaging lens is low, and therefore an extremely inexpensive scanning optical device can be realized.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a scanning optical device according to an embodiment, which includes a semiconductor laser 1a and a collimator lens 1.
The light source unit 1 in which b is united, the rotary polygonal mirror 2 which is a scanning means for deflecting and scanning the laser light L ₁ which is the light of the parallel light flux generated from the light source unit 1, and the scanning light deflected and scanned by this Has an image forming lens 4 for forming an image on the photosensitive member on the surface of the rotating drum through the folding mirror 3, and the rotating polygon mirror 2 and the image forming lens 4 are an optical box 5 which is a housing.
The light source unit 1 is mounted on the 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 incorporating all the necessary parts in the optical box 5. A window 6 is provided on the bottom wall of the optical box 5 to take 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 1a of the light source unit 1 is collimated by the collimator lens 1b and linearly condensed by the cylindrical lens 1c on the reflecting surface 2a of the rotary polygon mirror 2 to form an imaging lens. After passing through 4, the light is reflected by the folding mirror 3 and taken out from the window 6 of the optical box 5 toward the rotary drum. In this way, the scanning light imaged on the photosensitive member 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 image forming lens 4 has a so-called fθ function of correcting the distortion of the point image formed on the photosensitive member as described above, and is an aspherical lens asymmetric with respect to its optical axis (X axis). And is a plastic lens integrally molded of plastic.

As shown in FIG. 2, the bottom of the imaging lens 4 is provided with flanges 4a protruding on both side surfaces,
A similar flange 4b is provided on the top of the imaging lens 4, and the lens surface (effective portion) 4c of the imaging lens is provided between the bottom and the top flanges 4a and 4b. One of the flange portions 4a at the bottom of the imaging lens 4 has a protrusion 41 that protrudes from the center of the imaging lens 4 in the longitudinal direction along the optical axis thereof. A pair of positioning pins 5 protruding from the bottom wall of the optical box 5 during assembly
It is used to engage between a and to position the imaging lens 4 in the main scanning direction.

At one end of the imaging lens 4 in the length direction (Y-axis direction), a gate 42, which is a protruding portion left when the imaging lens 4 is integrally molded of plastic, is projected, and the optical box 5 is formed. In the assembling process of the imaging lens 4 with respect to the above, when the imaging lens 4 is lowered as shown by the arrow A without being reversely mounted and properly assembled, the gate 42 is turned on as shown in FIG. , The opposite side of the interference pin 5b, which is an interference means protruding from the bottom wall of the optical box 5, is arranged so as not to interfere with the interference pin 5b, and the imaging lens 4 is reversely attached 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 have a high flatness as a horizontal reference surface for positioning, and is brought into contact with a pair of seat surfaces 5c protruding from the bottom wall of the optical box 5 to form an imaging lens. 4 is used for positioning in the sub-scanning direction. Further, a pair of vertical reference planes 44 perpendicular to the optical axis of the imaging lens 4 are provided on both side edges of the imaging lens 4, and these are brought into contact with a positioning member 5d that is integral with the side wall of the optical box 5 to form an image. Positioning of the lens 4 in the optical axis direction is performed (see FIG. 2).

That is, the imaging lens 4 for the optical box 5
In 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 set to the seat surface 5c of the optical box. By contacting, and further 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, positioning is performed in the main scanning direction, the sub-scanning direction, and the optical axis direction, and then the bonding is performed. Alternatively, a spring or the like may be used to form the imaging lens 4
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 this way. Is extremely important to get.

As described above, the imaging lens is a plastic lens, and since it is constructed so as to prevent reverse mounting of the imaging lens by using the gate at the time of molding the plastic lens, in the assembly process of the imaging lens. In addition to being able to reliably prevent the imaging lens from being reversed, there is no need to separate the gate from the imaging lens manufacturing process, which adds the advantage of reducing the cost of individual imaging lens components. To be done.

In the case where the imaging lens is provided with a new projection for preventing reverse mounting without using the gate at the time of molding, not only a step of separating the gate is required, but also
Since the shape of the forming mold of the imaging lens becomes complicated, the cost of individual parts of the imaging lens may increase significantly.

The position of the gate of the imaging lens is preferably provided as far from the lens surface (effective portion) as possible so as not to affect the optical performance of the imaging lens. Therefore, it is optimal to provide it at one end in the length direction of the imaging lens as in the present embodiment, but it is not limited to this, and 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 be provided.

[0027]

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

In addition to being able to reliably prevent the assembly error of the imaging lens, by using the gate when molding the imaging lens on the protruding portion for preventing the assembly error, the work of separating the gate is omitted, The manufacturing process of the imaging lens can be greatly simplified. As a result, the cost of the individual components of the imaging lens can be reduced, the assembling process of the scanning optical device can be simplified and the speed can be increased, and an extremely inexpensive and high-performance scanning optical device can be realized.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing a state immediately before the imaging lens of the apparatus of FIG. 1 is assembled in an optical box.

3A and 3B are diagrams 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 the schematic plan view, (b) is a perspective view which shows only an imaging lens.

[Explanation 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 42, 52, 62 gates

Claims (3)

(57) [Claims] 1. A scanning unit, an imaging lens for forming an image of the scanning light on a photoconductor, a casing for supporting the scanning unit, and a connection of the imaging lens when an error occurs in assembling the imaging lens. A scanning optical device comprising: an interference unit configured to interfere with a protruding portion of an image lens, wherein the protruding portion of the imaging lens is a gate when the imaging lens is molded. 2. The scanning optical device according to claim 1, wherein the projection portion of the imaging lens is projected from an end portion in the length direction of the imaging lens. 3. The scanning optical device according to claim 1, wherein the imaging lens is a plastic lens.