JP3359223B2 - Optical scanning optical system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning optical system for preventing a change in performance of an anamorphic lens made of plastic in an optical scanning device used in an image forming apparatus or the like due to a change in environmental temperature. is there.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram of an optical scanning device generally used in a conventional image forming apparatus. Optical frame 1
The laser light L emitted from the laser unit 2 provided in the laser beam passes through a cylindrical lens 3 acting as an imaging lens, and is reflected by a polygon mirror 5 installed on a drive motor 4 and rotating at a constant speed in a certain direction. The light is deflected, passes through the scanning lenses 6 and 7, and scans a photosensitive member (not shown).

Many of the scanning lenses 6 and 7 used in this optical scanning device are aspherical lenses, and form a small spot diameter of the laser beam L on a photoreceptor to obtain a high quality image. I have to do it. In the case of mass-producing such complicated and high-precision imaging lenses, productivity is increased by molding with plastic.

However, if the environmental temperature changes in this case, the imaging performance of the optical system made of these plastics changes, and it becomes impossible to form a small image of the laser beam L, resulting in deterioration of the image quality. . That is, the scanning lenses 6 and 7 formed of plastics cause a change in the refractive index due to a change in temperature in the use environment and a change in the focal length, thereby changing the shape of the laser beam L formed on the photoreceptor. Occurs. As a result, an image obtained as an image forming apparatus cannot avoid deterioration in image quality.

[0005] Therefore, as already proposed in Japanese Patent Publication No. 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 has a temperature change. There is known a method of suppressing a change in focal length even if a refractive index change occurs due to the above, and performing temperature correction.

For example, as shown in FIG. 11, when two lenses 11 and 12 are bonded by a conventional method, as a first conventional example of a lens bonding method, first of all, only a lens 12 of a cylindrical lens is an optical frame. Then, as shown in FIG. 12, another lens 11 is slid in the X direction on the optical frame 1 to adjust the focus and adhere.

When such a method is used, if the optical axes O1 and O2 of the two lenses 11 and 12 are not aligned as shown in FIG. Since the shape of the lens collapses, a high-precision lens mounting surface is required on the optical frame 1 in a wide range, and it is necessary to mount the lenses 11 and 12 so that they do not tilt. become.

As a second conventional example of the lens bonding method, first, as shown in FIG. 14, two cylindrical lenses 1 are used.
1 and 12 are stuck together. At this time, first, in the first operation, the two lenses 11 and 12 are bonded so that the optical axes O1 and O2 match. Thereafter, the two cylindrical lenses 11 and 12 bonded to each other are placed on the optical frame 1 by X.
The focus is adjusted by sliding in the direction
When the optical axes O1 and O2 of the lenses 11 and 12 are bonded so that the optical axis shift α does not occur, the surfaces 11a and 12a of the lenses 11 and 12 contacting the optical frame 1 are slightly stepped by β. Sometimes.

In such a case, the sliding at the time of the focus adjustment cannot be performed smoothly, and even if the cylindrical lenses 11 and 12 are adhered to the optical frame 1 as shown in FIG.
Will occur.

[0010]

However, if a plurality of cylindrical lenses are attached to the optical frame 1 one by one as described above, the following problems occur.

(1) All cylindrical lenses 11, 1
Second, a high-precision surface for abutting against the optical frame 1 is required.

(2) All cylindrical lenses 11, 1
In order to bond 2, a high-precision surface is required in a wide area on the optical frame 1.

(3) The optical performance of the cylindrical lenses 11 and 12 cannot be evaluated unless they are attached to the optical frame 1.

(4) If the optical performance is found to be poor after the evaluation of the cylindrical lenses 11 and 12,
Since the optical frames 1 and 12 are bonded to the optical frame 1, the entire optical frame 1 cannot be used.

(5) A plurality of cylindrical lenses 11,
It takes time to adhere to the optical frame 1 while aligning the 12 optical axes 01 and 02.

Further, a plurality of cylindrical lenses 1
When bonding the optical lenses 1 and 12 to the optical frame 1 after bonding them to each other, the lenses 11 and 12 are precisely bonded to each other so that the optical axes of the lenses 11 and 12 do not deviate from each other. It is necessary to fix the lens while performing fine position adjustment. However, if the lenses 11 and 12 are not properly bonded to each other, the lenses 11 and 12 may be tilted and attached to the optical frame 1 or may be easily adjusted. There is also a problem that the operation cannot be performed.

An object of the present invention is to provide an optical scanning optical system capable of accurately disposing a plurality of cylindrical lenses, which are imaging lenses, on an optical frame in order to solve the above-mentioned problems.

[0018]

According to a first aspect of the present invention, there is provided an optical scanning optical system comprising at least one imaging lens for imaging a laser beam emitted from a light source on a deflection unit.
A pair of a cylindrical lens having a negative refractive power and a cylindrical lens having a positive refractive power, the laser light after passing through the imaging lens is deflected by the deflecting means,
A scanning lens that scans the deflected laser light on the medium to be scanned is an anamorphic lens made of at least one plastic lens, and is disposed such that an image forming point of the image forming lens is located at an object point of the scanning lens. In the optical system having the temperature compensation effect described above, one of the imaging lenses has a reference surface for bonding an optical frame serving as a reference when being arranged on an optical frame, and the other cylindrical lens has a reference surface for bonding. A reference surface for lens adhesion is provided as a reference, and the other cylindrical lens is provided with a reference surface for lens adhesion as a reference when bonding to the one lens, and the other cylindrical lens is connected to the one cylindrical lens. Do not protrude below the reference frame for bonding the optical frame of the lens, A pair of said cylindrical lens adhered based on's adhesive reference surface, characterized by being bonded with the optical frame adhering reference plane relative to the optical frame. Further, the optical scanning optical system according to the present invention,
At least one set of a cylindrical lens having a negative refractive power and a cylindrical lens having a positive refractive power is formed as an imaging lens for imaging the laser light emitted from the light source on the deflecting means. A scanning lens for deflecting the laser beam by the deflecting means and scanning the deflected laser light on the medium to be scanned is an anamorphic lens made of at least one plastic lens, and an image forming point of the imaging lens is an object of the scanning lens. In an optical system having a temperature compensation effect disposed so as to be located at a point,
The one cylindrical lens of the imaging lenses has an optical frame bonding reference surface serving as a reference when placed on the optical frame, and a lens bonding reference surface serving as a reference when bonding with the other cylindrical lens. The other cylindrical lens is provided with a lens bonding reference surface that serves as a reference when bonding with the one lens, and the other cylindrical lens is provided on the optical frame with the lens bonding reference surface of the optical frame. A relief portion is provided so as not to come into contact, and one set of the cylindrical lenses previously bonded based on the two lens bonding reference surfaces is bonded to the optical frame using the optical frame bonding reference surface. Features. Further, in the optical scanning optical system according to the present invention, at least one set of a cylindrical lens having a negative refractive power and a cylindrical lens having a positive refractive power are used as an imaging lens for forming an image of a laser beam emitted from a light source on a deflection unit. A scanning lens that deflects the laser light after passing through the imaging lens by the deflecting unit and scans the deflected laser light on a medium to be scanned;
An anamorphic lens composed of two plastic lenses, and in an optical system having a temperature compensation effect disposed so that the image forming point of the image forming lens is located at the object point of the scanning lens, one of the image forming lenses The cylindrical lens is provided with an optical frame bonding reference surface serving as a reference when placed on the optical frame, and a lens bonding reference surface serving as a reference when bonding with the other cylindrical lens, and the other cylindrical lens is provided with the other cylindrical lens. A lens bonding reference surface serving as a reference when bonding with the one lens is provided, and one set of the cylindrical lenses previously bonded based on the two lens bonding reference surfaces is attached to the optical frame with respect to the optical frame. Adhesion is performed using an adhesion reference surface, and at least one of the cylindrical lenses is a plastic lens. The plastic lens is characterized in that formed using the same mold with the part forming the optical frame adhering reference plane and the lens bonding reference surface.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIGS. 1 and 2 show the cylindrical lenses 21 and 22 of the first embodiment.
1 is made of glass and has a positive refractive power and has a flat surface on the lens 22 side. The lens 22 is made of plastic and has a negative refractive power and has a concave surface on the lens 21 side. An overhang 23 for mounting the lens 21 is provided below the plastic lens 22. The upper surface of the overhang 23 is a lens bonding reference surface 22 a for the lens 21, and the lower surface is for the optical frame 1. The reference surface 22b is used for bonding the optical frame.

The optical axis O2 of the lens 22, the reference surface 22a for adhering the lens, and the reference surface 22b for adhering the optical frame must be accurately arranged, so that they are on the same mold during molding. In addition, a parting line PL is formed. Furthermore, the lens bonding reference surface 21 which has been accurately processed so that the optical axis O1 of the lens 21 coincides with the optical axis O2 of the lens 22 is also provided on the glass lens 21.
a is provided.

The two cylindrical lenses 21 and 2
As the bonding method of the present embodiment using the lens 2, the lens bonding reference surface 21a of the lens 21 and the lens bonding reference surface 22a of the lens 22 are brought into contact with each other and bonded using an adhesive. The optical axes O1 and O2 between the optical fibers 22 can be stuck together without any deviation.

In this case, the adhesive is dropped on the lens bonding reference surface 22a. Since the two cylindrical lenses 21 and 22 are already integrated by bonding, the reference surface 22b for bonding the optical frame of the lens 22 as shown in FIG.
Is moved in the X direction while abutting against the bonding reference surface 1a on the optical frame 1 side, focus adjustment is performed, and an adhesive is dropped and bonded at a desired position. By using such a method, the cylindrical lenses 21 and 22 can be accurately and easily disposed without causing a shift between the optical axes O1 and O2.

In this embodiment, there is a possibility that the surface having high precision may be loose due to uneven application of the adhesive to the bonding reference surface. When the two cylindrical lenses 21 and 22 are bonded together, and when the adhesive is dropped onto the optical frame 1, the positions of the adhesives to be dropped are not directly on the bonding reference planes, but on the periphery of the respective reference planes. When applied, it can be attached while maintaining accuracy.

FIGS. 3 and 4 show the cylindrical lenses 31 and 32 of the second embodiment.
Each of the lenses 1 and 32 has a two-piece configuration. The lens 31 is made of glass, and the lens 32 is made of plastic. Lens bonding reference surfaces 31a and 32a are provided above these two lenses 31 and 32, respectively.

In FIG. 3, reference surfaces 31 a, 32 a for lens bonding are respectively moved from optical axes O 1, O 2 of lenses 31, 32.
The heights ha1 and hb1 are ha1 = hb1. On the other hand, the relationship between the heights ha2 and hb2 from the optical axes O1 and O2 to the lower surfaces of the respective lenses 31 and 32 is represented by ha2 ≠ hb2, that is,
Make sure either ha2 or hb2 is clearly larger.
In this embodiment, ha2 <hb2, and the reference surface 3 for bonding the optical frame is provided below the lens 32 having the higher ha2.
2b is provided.

In the bonding method according to the present embodiment, the two lenses 31 and 32 are bonded by bonding the lenses 31 and 32 together with the bonding surface S while the reference surfaces 31a and 32a for bonding the lenses are arranged in a plane having high flatness accuracy. , 32 are integrated so that the optical axes O1 and O2 do not shift. Thereafter, focus adjustment is performed while sliding in the X direction on the reference surface 1a on the optical frame 1 as shown in FIG. 4, and the optical frame bonding reference surface 32b is moved to a desired position.
Are the same as those in the first embodiment.

At this time, the lens 32 bonded to the optical frame 1 has a large optical frame bonding reference surface 32b.
In addition, it is preferable that the integrated lenses 31 and 32 have a large shape so as to be easily slid, and a plastic lens is less expensive.

In this method as well, a plurality of cylindrical lenses 31 and 32 can be bonded without shifting the optical axis, and a reference surface 32a for bonding to the optical frame 1 can be formed.
Is provided only on one lens 32, so that the lenses 31 and 32 can be bonded to the optical frame 1 with high accuracy and easily.

FIGS. 5 to 7 show the case of the cylindrical lenses 41 and 42 according to the third embodiment. The lenses 41 and 42 have a two-element configuration. The lens 41 is made of glass and the lens 42 is made of plastic. Yes, these two lenses 4
Reference surfaces 41a, 42 for bonding the lenses are provided on the lower surfaces of 1, 42, respectively.
a is provided.

In FIG. 5, each lens 41, 4
From the optical axes O1 and O2 of the second lens reference surfaces 41a and 42a.
The lengths ha1 and hb1 are ha1 = hb1. The lens bonding reference surface 41a is also used as an optical frame bonding reference surface. At the center of the lens bonding reference surface 42a of the lens 42, a concave portion 42b is provided as shown in FIG. Then, on the optical frame 1, the bonding reference surface 4 of the lens 42 is provided.
Two escape grooves 1b and 1c are provided so that 2a does not touch. This is because the lenses 41 and 42 are bonded and integrated.
If the lens bonding reference surfaces 41a and 42a have a slight step, they are used as optical frame bonding reference surfaces as they are, and do not move smoothly during focus adjustment or bonding as described above, or can be attached at an angle. This is because there is a fear.

In this embodiment, the bonding method of the lens 4
When the bonding surfaces S are bonded to each other by aligning the reference surfaces 41a and 42a for lens bonding of the lenses 1 and 42 with planes having high flatness, there is no displacement of the optical axes O1 and O2 of the two lenses 41 and 42. Can be integrated. Thereafter, using the reference surface for bonding the optical frame, that is, the reference surface for lens bonding 41a, the focus adjustment and bonding are performed by moving the reference surface 1a on the optical frame 1 in the X direction. With such a configuration, the reference surfaces for bonding the optical frames of the cylindrical lenses 41 and 42 need only be set on one surface, so that the lenses can be mounted on the optical frame with higher accuracy and the processing cost can be reduced. Is preferred.

FIGS. 8 and 9 show the case of the cylindrical lenses 51 and 52 according to the fourth embodiment. The cylindrical lenses 51 and 52 are composed of two lenses. The lens 51 is made of plastic and the lens 52 is made of plastic. Or it is made of glass. The lens 51 is vertically held by holding plates 53 and 54.
Is projected toward the lens 52, and a spring portion 5
3a and 54a are bent inward. The surface of the lens 51 facing the lens 52 side is the lens bonding reference surface 51.
a. The lens 52 is provided with two reference surfaces 52a for bonding the lens at two positions above and below the deformed surface. Further, in order to eliminate the displacement of the lens 51 in the Z direction, a lens bonding reference surface 51b is provided inside the holding plate 54 of the lens 51, and a lens bonding reference surface 52b is provided on the lower surface of the lens 52. When the lenses 51 and 52 are joined, the two lens bonding reference surfaces 51a and
52a are pressed against each other. Further, the lower surface of the lens 51 is an optical frame bonding reference surface 51c.

These two lens bonding reference surfaces 51
a, 51b, 52a, 52b, two lenses 5
The optical axes O1 and O2 of 1, 52 can be aligned. When fitting the two lenses 51 and 52, the lens bonding reference surface 52b of the lens 52 is placed on the lens bonding reference surface 51b of the lens 51, and the lens 52 is slid from the Y direction in FIG. While fitting into the lens 51. When the fitting portion is finished with high precision, no adhesive is required, and the lens 51,
52 can be integrated, leading to cost reduction, and furthermore, there is no fear that an adhesive will adhere to the lens effective surface. In this embodiment, the holding plates 53 and 54 of the cylindrical lens 51
Since the method of sandwiching the other lens 52 is adopted, there is an advantage that the deviation of the tilt angle of the lens does not occur.

In each of the embodiments described above, the description has been made of the cylindrical lens having a two-element structure. However, the present invention can be applied to three or more lenses.

[0035]

As described above, according to the optical scanning optical system of the present invention, a plurality of cylindrical lenses constituting an image forming lens are provided with a lens bonding reference surface so that the optical axes can be stably aligned. Can be integrated together. Also,
Since the contact surface of the cylindrical lens with the optical frame at the time of focus adjustment, that is, the reference surface for bonding the optical frame is provided on only one lens, there is no tilt of the optical axis when mounting on the optical frame. Can be easily performed.

[Brief description of the drawings]

FIG. 1 is a perspective view of a cylindrical lens according to a first embodiment.

FIG. 2 is a perspective view of a state in which they are bonded.

FIG. 3 is an example of a state in which a cylindrical lens according to a second embodiment is bonded.

FIG. 4 is a perspective view of a bonded state.

FIG. 5 is a side view showing a state where a cylindrical lens according to a third embodiment is bonded.

FIG. 6 is a rear view.

FIG. 7 is a perspective view.

FIG. 8 is a perspective view of a cylindrical lens that is a fourth example.

FIG. 9 is a perspective view of a bonded state.

FIG. 10 is a configuration diagram of an optical scanning device.

FIG. 11 is an explanatory view in the case of bonding a cylindrical lens which is a first conventional example.

FIG. 12 is an explanatory diagram in the case of bonding a cylindrical lens which is a first conventional example.

FIG. 13 is an explanatory diagram in the case of bonding a cylindrical lens as a first conventional example.

FIG. 14 is an explanatory diagram in the case of bonding a cylindrical lens as a second conventional example.

FIG. 15 is an explanatory diagram in the case of bonding a cylindrical lens as a second conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical frame 1a Optical frame bonding reference surface 1b, 1c Escape groove 21, 22, 31, 32, 41, 42, 51, 52 Cylindrical lens 21a, 22a, 31a, 32a, 41a, 42a, 42a, 5
1a, 51b, 52a Reference surface for bonding lens 22b, 32b, 41a, 51c Reference surface for bonding optical frame

Claims (3)

(57) [Claims] An imaging lens for imaging a laser beam emitted from a light source on a deflecting means is at least one set of a cylindrical lens having a negative refractive power and a cylindrical lens having a positive refractive power. The scanning lens that deflects the laser light after passing by the deflecting unit and scans the deflected laser light on the medium to be scanned is an anamorphic lens made of at least one plastic lens, and the imaging point of the imaging lens is In an optical system having a temperature compensation effect disposed so as to be located at an object point of the scanning lens, one of the imaging lenses has an optical frame bonded as a reference when being disposed on an optical frame. A reference surface for lens bonding, and a reference surface for lens bonding as a reference when bonding to the other cylindrical lens. The cylindrical lens is provided with a lens bonding reference surface serving as a reference when bonding with the one lens, and the other cylindrical lens is provided with a front surface.
For bonding one cylindrical lens to an optical frame
A set of the cylindrical lenses previously bonded based on the two lens bonding reference surfaces was bonded to the optical frame using the optical frame bonding reference surface so as not to protrude below the reference surface. An optical scanning optical system, comprising: 2. An imaging lens for imaging a laser beam emitted from a light source on a deflecting unit includes at least one set of a cylindrical lens having a negative refractive power and a cylindrical lens having a positive refractive power. The scanning lens that deflects the laser light after passing by the deflecting unit and scans the deflected laser light on the medium to be scanned is an anamorphic lens made of at least one plastic lens, and the imaging point of the imaging lens is In an optical system having a temperature compensation effect disposed so as to be located at an object point of the scanning lens, one of the imaging lenses has an optical frame bonded as a reference when being disposed on an optical frame. A reference surface for lens bonding, and a reference surface for lens bonding as a reference when bonding to the other cylindrical lens. The cylindrical lens is provided with a lens bonding reference surface that serves as a reference when bonding with the one lens, and the other frame is provided on the optical frame.
Lens contacts the lens bonding reference surface of the optical frame.
A relief portion is provided so as not to touch, and one set of the cylindrical lenses previously bonded based on the two lens bonding reference surfaces is bonded to the optical frame using the optical frame bonding reference surface. Optical scanning optical system characterized. 3. An imaging lens for imaging a laser beam emitted from a light source on a deflecting unit includes at least one set of a cylindrical lens having a negative refractive power and a cylindrical lens having a positive refractive power. The scanning lens that deflects the laser light after passing by the deflecting unit and scans the deflected laser light on the medium to be scanned is an anamorphic lens made of at least one plastic lens, and the imaging point of the imaging lens is In an optical system having a temperature compensation effect disposed so as to be located at an object point of the scanning lens, one of the imaging lenses has an optical frame bonded as a reference when being disposed on an optical frame. A reference surface for lens bonding, and a reference surface for lens bonding as a reference when bonding to the other cylindrical lens. The cylindrical lens is provided with a lens bonding reference surface serving as a reference when bonding with the one lens, and a set of the cylindrical lenses previously bonded based on the two lens bonding reference surfaces is attached to the optical frame. Bonding using the optical frame bonding reference surface
And at least one of the cylindrical lenses is
A plastic lens, wherein the plastic lens is
The reference surface for bonding the lens and the reference surface for bonding the optical frame
An optical scanning optical system formed using the same mold having a portion to be formed .