JP3323726B2 - Optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical scanning device for coping with performance degradation of an anamorphic lens made of plastic used for an image forming apparatus or the like due to a change in environmental temperature.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional optical scanning device generally used in an image forming apparatus, and a laser beam L generated from a laser unit 2 disposed on an optical frame 1 is coupled. The light passes through a cylindrical lens 3 acting as an image lens and is incident on a polygon mirror 5 installed on a drive motor 4 and rotating at a constant speed in a certain direction, where it is reflected and deflected, passes through scanning lenses 6 and 7, and is illustrated. Scan on the photoreceptor that does not.

One of the scanning lenses 7 used in the optical scanning device has an aspherical shape, and has a capability of forming an image with a small diameter of a laser beam on a photosensitive member in order to obtain a high-quality image. are doing. When mass-producing such a complicated and high-precision imaging lens, productivity is increased by molding with plastic. However, when the environmental temperature changes, the image forming performance of these optical systems changes, and it becomes impossible to form a small image of the laser beam, thereby deteriorating the image quality.

[0004] In other words, due to temperature changes in the operating environment,
A lens formed of plastic causes a change in the refractive index and a change in the focal length, thereby causing a change in the spot shape of the laser light imaged on the photoreceptor. As a result, the image obtained by the image forming apparatus cannot avoid deterioration in image quality. Therefore, as already proposed in Japanese Patent Publication No. Hei 4-47803, the cylindrical lens 3 is made up of a plurality of plastic lenses having a negative refractive index and a glass lens having a positive refractive index, and is refracted by a temperature change. A method is known in which even if a rate change occurs, a change in the focal length is suppressed to perform temperature compensation.

[0005]

However, in the above-mentioned conventional example, the cylindrical lens 3 is mounted on the optical frame 1 by adjusting the position in the optical axis direction so that the laser beam forms an image in a desired shape. Therefore, a plurality of cylindrical lenses 3 are arranged one by one in the optical frame 1.
If it is fixed to, the installation work will take a lot of time. Further, the mounting surface of the optical frame 1 also needs a highly accurate reference surface over a wide range.

Therefore, a plurality of cylindrical lenses 3
It is conceivable that the plastic lens and the glass lens are attached to each other after being bonded to each other. However, since the plastic lens and the glass lens have different coefficients of thermal expansion, a deformation stress is generated in the plastic lens due to a temperature change. And the curvatures of both lenses change, making it impossible to perform desired temperature compensation.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide an optical scanning device which can perform temperature compensation in response to a temperature change, is small, and can be easily assembled.

[0008]

According to the present invention, there is provided an optical scanning apparatus comprising: a light source; a deflecting means for deflecting a light beam; and a light beam radiating from the light source. Imaging means for imaging the means, and a scanning lens for imaging the light beam deflected by the deflecting means on a medium to be scanned, wherein the imaging means comprises a plastic lens having at least a negative refractive power; A glass lens having a positive refractive power, in an optical scanning device in which the plastic lens and the glass lens are integrated with an adhesive, the plastic lens and the glass lens are in contact with each other, and the plastic lens An adhesive land portion extending toward the glass lens is provided, and the plastic lens is provided with the lens effective portion and the glass A reference surface that defines the distance between the lenses, and an adhesive is applied between a surface of the glass lens that is different from the surface on the contact side with the plastic lens and the bonding land portion of the plastic lens. It is characterized by.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a configuration diagram of the optical scanning device. The optical unit 11 has a laser unit 1
2. The drive motor 13 is fixed, and the polygon mirror 14 is mounted on the drive motor 13. Further, a first cylindrical lens 15 made of glass having a positive refractive index and a second cylindrical lens 16 made of plastic having a negative refractive index are arranged between the optical frame 11 and the polygon mirror 14. Further, a scanning lens having fθ characteristics is provided in the deflection scanning direction of the polygon mirror 14. This scanning lens is composed of a glass lens 17 obtained by processing a spherical lens into a strip shape, and a plastic lens 18 having an aspherical shape.

The laser light L emitted from the laser unit 12 is applied to first and second cylindrical lenses 15, 1
6, the laser beam is linearly imaged on the reflection surface of the polygon mirror 14 and then deflected by the polygon mirror 14.
The light passes through the plastic lens 18 and forms an image on a photosensitive member (not shown).

In this optical scanning device, the first cylindrical lens 15 and the second cylindrical lens 16 are partially bonded to each other, and the optical axis of the laser light is adjusted so that a desired laser shape can be obtained on the photosensitive member. The position is adjusted in the direction, and the adhesive is fixed to the optical frame 11. This is for correcting the change in the focal length of the plastic lens 18 caused by the change in temperature, as described above. The first and second cylindrical lenses 15 and 16 are adjusted in position as in the conventional example. It is more accurate and easier to install than the optical frame 11.

FIG. 2 shows a state before the first and second cylindrical lenses 15 and 16 are bonded together. The plastic second cylindrical lens 16 having a negative refractive index includes a cylindrical effective lens portion 16a through which laser light passes, and a second lens effective portion 16a.
And two reference surfaces 1 that are in contact with the first cylindrical lens 15 made of glass and define the distance between the first cylindrical lens 15
6b and 16c, and bonding lands 16d and 16e are provided on both sides of the lens 16 in the cylindrical axis direction. The bonding lands 16d and 16e hold both ends of the first cylindrical lens 15 in the cylindrical axis direction.

As shown in FIG. 3, when the flat portion of the first cylindrical lens 15 and the reference surfaces 16b and 16c of the second cylindrical lens 16 are in contact with each other, ultraviolet curing is performed on the upper side of the bonding lands 16d and 16e. A mold adhesive 21 is applied. At this time, the bonding lands 16d, 16e
If an upper surface is provided with an application portion such as chamfering so that the adhesive 21 can be easily applied, workability is improved. After the application of the adhesive 21, the adhesive 21 is cured by ultraviolet rays, and the two cylindrical lenses 15 and 16 are adhered to each other so that the two lenses can be integrated with high accuracy.

Here, the reason why the bonding lands 16d and 16e are not arranged above and below the lens effective portion 16a is that the thermal expansion of the cylindrical lenses 15 and 16 differs from each other, and the expansion and contraction of the second cylindrical lens 16 causes these to expand and contract. This is to prevent an unintended change in the curvature of the lens. If the bonding lands 16d and 16e are provided in the cylindrical axis direction of the first and second cylindrical lenses 15 and 16, the first lands can be formed even if the lens 16 expands and contracts due to a temperature change.
Does not affect the lens characteristics of the cylindrical lens 15.

Further, as shown in FIG.
It is more preferable to dispose 6d and 16e at positions deviated above and below the lens effective portion 16a. This is because a deformation stress is generated in the second cylindrical lens 16 due to a difference in thermal expansion, and this stress is prevented from affecting the inside of the effective lens portion 16a.

FIG. 5 shows a second embodiment, in which the first cylindrical lens 15 made of glass and the second cylindrical lens 16 made of plastic have a temperature compensating function as in the previous embodiment. It is integrated as follows.
Land portion 16 for bonding of second cylindrical lens 16
f is disposed on the upper surface of the lens 16 so as to cover the first cylindrical lens 15. The first and second cylindrical lenses 1 are provided through the bonding land 16f.
The adhesive 22 bonding the layers 5 and 16 is made of, for example, a silicone rubber adhesive and has elasticity. The adhesive 22 temporarily bonds a plurality of lenses.

As described above, when the bonding lands 16f are provided in the direction of curvature, it is desirable to use an elastic adhesive.

Thereafter, in order to fix the bonded cylindrical lenses 15 and 16 to the optical frame 11, the cylindrical lenses 15 and 16 are firmly fixed by the adhesive 23 on the lower surface facing the adhesive surface. In this case, the cylindrical lens 16
Even if the adhesive 22 is adhered and fixed in the direction of curvature, the adhesive 22 on one side has elasticity, so that the influence of the change in the curvature of the second cylindrical lens 16 can be prevented.

With such a configuration, even if the concave surface of the second cylindrical lens 16 is bonded in the direction of curvature, the deformation stress due to the difference in the coefficient of thermal expansion can be released, so that an unintended change in curvature does not occur. Therefore, temperature compensation close to the theoretical value can be performed. The imaging lens composed of the first and second cylindrical lenses having the temperature compensation effect configured as described above uses a single scanning lens formed of plastic, and the influence of the refractive index change due to the temperature change is reduced. Since it becomes remarkable, a minute spot shape of laser light can be obtained.

[0020]

As described above, in the optical scanning device according to the present invention, when a plurality of cylindrical lenses, especially a glass lens and a plastic lens are bonded, the plastic lens is deformed due to a difference in thermal expansion. Will not be affected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical scanning device.

FIG. 2 is a perspective view of the cylindrical lens according to the first embodiment before being attached.

FIG. 3 is a perspective view of the attached cylindrical lens.

FIG. 4 is a perspective view of a modified example of a plastic cylindrical lens.

FIG. 5 is a perspective view of a cylindrical lens according to a second example.

FIG. 6 is a configuration diagram of a conventional optical scanning device.

[Explanation of symbols]

 11 Optical Frame 15 Glass Cylindrical Lens 16 Plastic Cylindrical Lens 16a Lens Effective Part 16b, 16c Reference Surface 16d, 16e, 16f Adhesive Land 17 Glass Lens 18 Plastic Lens

Claims (4)

(57) [Claims] 1. A light source and a deflecting means for deflecting a light beam.
The light beam emitted from the light source into a linear
Image forming means for forming an image on a step, and deflected by the deflecting means
A scanning lens for forming an image of the light beam on the medium to be scanned.
And the imaging means has at least a negative refractive power.
Plastic lens and glass lens with positive refractive power
Comprising the plastic lens and the glass lens
In an optical scanning device in which the
When the plastic lens and the glass lens abut,
And the plastic lens extends to the glass lens side.
The plastic lens is provided with
The lens effective portion and the contact portion on the contact side with the glass lens
A reference surface for defining the distance between the glass lenses;
The surface of the lens which is in contact with the plastic lens
Is a different surface and the land for bonding the plastic lens
An optical scanning device, wherein an adhesive is applied between the optical scanning device. 2. The method according to claim 1, wherein a bonding land portion of the plastic lens is disposed so as to face a side surface of the glass lens.
The optical scanning device according to claim 1, wherein: 3. A land for bonding the plastic lens.
The position where the adhesive is applied to the part is at the height of the plastic lens.
In the vertical direction, the lens effective of the plastic lens
3. The light according to claim 2, wherein the light is out of the range.
Scanning device. Wherein said adhesive is a photocurable adhesive, claim 1, characterized in that it has a characteristic that even after curing to stretch
3. The optical scanning device according to claim 1.