JPH0627404A - Scanning optical device and production of hybrid scanning lens to be used for this device - Google Patents

Abstract

PURPOSE:To provide the hybrid lens having good mass productivity, excellent shape accuracy, surface accuracy and environmental resistance and an axially non-symmetrical aspherical shape. CONSTITUTION:A UV curing resin 3 of a transparent org. high-polymer material having the refractive index nearly equal to the refractive index of a basic lens 5 having micro-ruggedness over the entire area of its surface or in a part thereof is applied on the surface of this basic glass lens 5 and the lens is pressed to the male mold surface 4 of a mold 2 having a toric shape in such a manner that the resin 3 fills closely between the basic lens 5 and the female mold surface 4. The resin 3 is then irradiated with UV rays through the basic lens 5 and is thereby cured. The desired hybrid lens 6 is obtd, when the basic lens 5 is pulled apart from the mold 2 having the toric shape after the above- mentioned curing. The mold 2 is worked to the aspherical female mold by controlling the spacial positional relation between a work piece and a grinding wheel spindle by a polar coordinate system, then rotating the work piece and moving the grinding wheel spindle to an arc shape within the plane orthogonal with the rotating direction thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-axisymmetric aspherical F.theta. Lens having a complicated shape, a method for manufacturing the same, and a laser beam printer using the lens.

[0002]

2. Description of the Related Art The configuration of a laser printer will be described with reference to the drawings. The laser beam printer mainly uses a scanning optical system (FIG. 21) for modulating and deflecting the laser light emitted from the light source 39 to form an optical pattern on the photoconductor 43, and a scanning optical system on the photoconductor 43. It is composed of an image forming system (FIG. 22) for making a hard copy of the light pattern formed on the substrate by an electrophotographic process.

In FIG. 21, the light source 39 is generally
A gas laser or a semiconductor laser is used. Also,
As the modulator 47, an A / O modulator using an acousto-optic (A / O) element is generally used. The A / O modulator allows ultrasonic waves to pass through the A / O element, and diffracts the incident laser beam by the synchronous change in the refractive index generated thereby to perform intensity modulation. A divergent beam emitted from a semiconductor using a beam compressor 48a for narrowing the incident beam diameter and a beam expander 48b used for obtaining a small image spot on the photosensitive member in order to increase the modulation speed by the A / O element. A collimator lens that converts the light into a parallel beam is used. A rotary polygon mirror (polygon mirror) 4 is used as a deflector for scanning the photosensitive member with laser light.
2 is used. A laser printer using a hologram has been proposed instead of the rotating polygon mirror.

Since the rotary polygon mirror 42 rotates at a constant speed,
The reflected laser light is deflected at a constant angular velocity. The image forming lens (Fθ lens) 38 has an action of forming an image of the deflected laser light on one plane on the surface of the photoconductor, and also imparts optical distortion to incident light of a constant angular velocity so that the surface of the photoconductor becomes uniform. Function to convert to scan on top (fθ characteristic)
have.

The photoconductor 43 has a two-layer structure in which a photoconductor layer is provided on a conductive support. In advance, the surface of the photoconductor was uniformly charged by the discharge of the positive corona 49 in a dark place, and when laser light was applied to this, the resistance of the photoconductor in the part exposed to the light was lowered and the charge was charged. Flow to the ground, and the surface of the photoconductor 43 has a portion where electric charge remains and a portion where electric charge does not remain.

The latent image formed on the photoconductor 43 is developed with positively or negatively charged toner.
As shown in FIG. 22, the surface of the insulating layer is discharged to the photoconductor 43 by corona discharge, and at the same time, laser light is irradiated through the imaging lens 38. In the bright portion irradiated with the laser light, the resistance of the photoconductive layer is reduced to be conductive, and the charges on the front and back surfaces of the insulating layer are rapidly attenuated. In the dark area where laser light is not applied, the electric potential of the insulating layer surface is AC corona discharge.
When exposed to 0, the potential becomes almost 0, but the electric charge formed at the interface between the insulating layer and the photoconductive layer is retained.

In this way, after the charging layer is formed at the interface between the insulating layer and the photoconductive layer by the primary charging, the surface of the insulating layer is discharged by corona discharging, and at the same time, laser light is irradiated for exposure. Next, the entire surface of the photoconductor 43 is uniformly exposed by the whole surface exposure device 51, thereby increasing the surface potential of the dark portion. The latent image formed on the photoconductor 43 is developed by the toner of the developing device 52 which is positively or negatively charged. After the developing process, the toner image on the photoconductor 43 is electrostatically transferred to the plain paper sent from the paper feeding cassette 53 through the paper feeding roller 54, and is stabilized by the fixing process by the fixing device 55. Become a statue. The transferred plain paper is
It is sent to the stacker 56. After the transfer step, the residual toner that has not been transferred to the photoconductor is removed by the cleaning step using the cleaning 57 and the cleaning blade 58 to prepare for the latent image forming process again. Regarding the laser beam printer, for example, Kitamura and Hirayama:
"Laser beam printer" (Photo Industry) 1976 2
Month, pp. 89-92.

In such a laser printer, the following proposals have been made in order to achieve high-quality printing without increasing the number of parts.

For example, in Japanese Unexamined Patent Publication No. 2-23313, an asymmetrical aspherical shape is adopted in which the radius of curvature of the Fθ lens in the plane tilt direction (sub-scanning direction) increases as the distance from the center of the optical axis increases. A configuration is disclosed.

A method of processing such a non-axisymmetric aspherical lens is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-53557. This is a method of processing a lens by grinding under NC control, and according to this method, an arbitrary aspherical surface shape can be created. However, with this method, the processing time is very long (7 pieces in 3 hours), and there is a problem in mass productivity.

Further, as an aspherical lens processing method excellent in mass productivity, a method of obtaining a plastic lens excellent in shape accuracy and surface accuracy in addition to a molding method using plastic as a material has been proposed (see, for example, Japanese Patent Laid-Open Publication No. 2000-242242). Sho 59-20
4001 publication).

[0012]

However, with respect to the female mold required for the molding process, most of the optical surfaces that can be obtained at present are flat surfaces or spherical surfaces. Further, even if it is an aspherical surface, it is an axisymmetrical aspherical surface like a lens of a single-lens reflex camera, and it is impossible to process a concave surface of the axisymmetrical aspherical surface. That is, at present, although it is possible to mold an axisymmetric aspherical lens, it is not possible to mass-produce an axisymmetric aspherical lens by molding. Also,
A plastic lens is likely to be deformed due to temperature change during use, which causes aberration and optical axis shift. Also, plastic lenses are susceptible to humidity and chemical substances in the atmosphere. In this regard, a method for forming a protective film on the lens surface (for example, JP-A-56-28023) and a method for forming a lens protective film by forming an organic silicon protective film by vapor deposition (for example, JP-A-56-25701) are proposed. Has been done.
However, since these methods require control of the protective film thickness and a process of baking the deposited film, it is impossible to process a non-axisymmetric aspherical lens that can be mass-produced with high quality. Therefore, it is an important issue to be solved to develop a concave surface creation technique having an axisymmetric aspherical shape and obtain a highly accurate axisymmetric aspherical female mold.

Therefore, an object of the present invention is to solve these conventional problems, to have good mass productivity, to be excellent in shape accuracy, surface accuracy and environmental resistance, and to have a non-axisymmetric aspherical shape, and to manufacture the same. A method and a laser beam printer using the hybrid lens are provided.

Another object of the present invention is to provide a hybrid lens utilizing a concave surface having an axisymmetric aspherical shape.

Another object of the present invention is to provide a highly accurate non-axisymmetric aspherical female mold and a method for manufacturing the same, by manufacturing a concave surface having a non-axisymmetric aspherical shape with high accuracy.

[0016]

In order to achieve the above object, a transparent organic polymer material having a refractive index substantially equal to that of the basic lens is formed on the surface of a basic glass lens having minute irregularities over the entire surface of the lens or a part thereof. A resin made of is laminated in a non-axisymmetric aspherical shape to produce a scanning lens having a basic glass lens and resin integrally bonded structure. Further, an ultraviolet curable resin is used as a transparent organic polymer material having a refractive index substantially equal to that of the basic lens, and is laminated on the basic glass lens. In addition, the lens formed by laminating the ultraviolet curable resin on the surface has different curvature radii of the main axis and the sub-axis, and has an aspherical surface that asymmetrically increases as the radius of curvature of the sub-axis becomes off-axis. There is also a feature. Further, a desired lens shape is transferred to the surface of the basic glass lens by the shape transfer method. The female die used in the shape transfer method has a non-axisymmetric aspherical shape. It is characterized in that a plastic lens portion made of an ultraviolet curable resin and a basic glass lens portion are integrally joined and molded. Further, a protective film made of SiO or SiO ₂ is formed on the lens surface by using a thin film forming method such as a vacuum evaporation method.

Further, in female die machining, the spatial positional relationship between the workpiece and the grindstone spindle is controlled at high speed in a polar coordinate system, the workpiece is rotated, and the grindstone spindle is rotated in a plane orthogonal to the direction of rotation. A desired aspherical female die is machined by moving in an arc shape and changing the axial distance between the rotary shaft of the workpiece and the rotary shaft that makes the spindle of the grindstone to move in an arc according to the rotation angle of the workpiece. Is characterized by.

Further, with the arc movement of the grindstone spindle,
By controlling the spraying amount and spraying direction of the grinding fluid according to the movement of the grinding point, the surface roughness of the ground finished surface is improved and a highly accurate aspherical female mold can be obtained.

[0019]

In the present invention, on the basic lens made of glass,
A hybrid lens is manufactured by laminating resins having a refractive index substantially equal to that of the basic lens, and integrally joining and molding these. Since the resin having a refractive index almost equal to that of glass is laminated, the optical path does not change at the joint surface. Further, since it is possible to mass-produce a hybrid lens having a non-axisymmetric aspherical shape for correcting the scanning pitch unevenness due to the inclination of the reflecting surface of the rotary polygon mirror of the laser beam printer using such a hybrid lens, it is possible to mass-produce it with extremely high accuracy. An inexpensive laser beam printer can be easily realized. In order to obtain a hybrid lens having a non-axisymmetric aspherical shape, the present invention uses a female mold having a concave surface of a non-axisymmetric aspherical shape, and by this female mold, at the same time laminating a synthetic resin on a basic lens made of glass, A female non-axisymmetric aspherical shape is transferred by the replica method. Since an ultraviolet curable resin is used as the synthetic resin and is molded by the replica method, an aspherical Fθ lens for a laser beam printer having a complicated shape can be extremely easily manufactured by using a highly accurate female mold.

Further, even when the basic lens is poorly finished and the surface is not a mirror surface, the surface of the obtained hybrid lens is a mirror surface because the female transfer surface is processed into a mirror surface. Further, since the refractive index of the laminated resin is almost the same as that of the basic lens, the completed hybrid lens can obtain the same optical performance as that of the glass lens.

Regarding the bondability between the basic lens and the resin layer to be laminated, by forming minute irregularities on the surface of the basic lens and laminating the resin thereon, the optical characteristics of the lens are not impaired. The adhesiveness between the basic lens and the resin layer can be improved.

In the hybrid lens of the present invention, a non-axisymmetric aspherical thin film layer made of synthetic resin is laminated on the surface of the basic lens made of glass. The average film thickness of the plastic lens portion made of synthetic resin is 20 μm or less, which is very thin. An ultraviolet curable resin is used for the plastic lens material, and since the plastic lens is molded on the glass lens by the irradiation of the ultraviolet rays, it is not necessary to apply a high pressure to the resin when molding the lens. Therefore, as compared with the case where a non-axisymmetric aspherical lens is manufactured by molding using only plastic material, the residual stress generated in the molded plastic lens can be suppressed and the residual stress causes Almost no deformation or deterioration of optical characteristics is caused.

Further, SiO or SiO _{2 is} formed on the lens surface.
Since the protective film made of is formed, the reliability of the hybrid lens including weather resistance and waterproofness can be improved. When the SiO or SiO ₂ protective film is formed on the lens surface by the vacuum deposition method, the lens is exposed to vacuum. If water remains inside the plastic lens layer, water is released from the inside of the lens during the formation of the protective film and adheres to the lens surface, which may reduce the adhesiveness between the protective film and the lens surface. Therefore, in order to improve the adhesiveness between the protective film and the lens surface, the following means are used. First, heat treatment is applied to the hybrid lens that has been molded and cured for a certain period of time to remove the water remaining inside the lens, and when the water inside the lens is completely removed, the lens surface is irradiated with ozone and subjected to a cleaning treatment. As a result, the dirt adhering to the lens surface is removed, the adhesiveness between the protective film and the lens surface is improved, and the protective film is formed on the lens surface. The lens surface produced by the above method has a very dense protective film with a small surface energy that does not allow water molecules to pass through. Therefore, the water repellency is improved and water does not penetrate into the lens from the outside. It is possible to realize a lens that has no loss and is highly reliable.

By heat-treating the molded and hardened hybrid lens, the resin can be uniformly hardened, and a hybrid lens that is homogeneous over the entire area can be obtained.

Further, in the above-mentioned female machining method, grinding is performed while changing the inter-axis distance between the rotational axis of the workpiece and the rotational axis for the arc movement of the grindstone spindle in accordance with the rotational angle of the non-machined object. Do. Furthermore, if the grindstone spindle is finely moved step by step, and each time the machining data is updated and grinding is continued, a deformed toric shape with a slight deviation from the toric shape, that is, a female die with a non-axisymmetric aspherical shape is machined. it can. Further, in the grinding apparatus for creating the female die 59 as shown in FIG. 23, the grindstone 15 performs grinding while moving around the workpiece along the curved path 300 to be created. At this time, the nozzle 60 at the grinding point
It is better to dispose the grinding fluid in parallel with the tangent line of the grindstone 15 and spray the grinding fluid, but in reality, there is a high-speed air layer on the surface of the grindstone where the nozzle interferes with the workpiece or rotates at a high speed. However, since most of the grinding liquid is repelled, the amount of the grinding liquid reaching the grinding portion is reduced. Therefore, in order to prevent the interference between the nozzle and the workpiece and to increase the efficiency of supplying the grinding liquid to the grinding point, the nozzle 60 is provided slightly tilted from the tangential direction of the grindstone 15 as shown in FIG. However, when grinding is performed while moving the grindstone 15 along a certain track 300 in this state, the jetting direction of the grinding liquid slightly changes due to the relative positional relationship between the grindstone 15 and the workpiece 59, and the grinding liquid There are subtle differences in the supply state, and the state of the finished surface differs depending on the location. In order to solve this problem, it is necessary to optimize the jet direction of the grinding fluid as the grinding point moves. Therefore, in the present invention, as shown in FIG. 25, by disposing a plurality of nozzles 35 along the trajectory in the sub-scanning direction, even if the relative grinding positions are different, the grinding liquid is always ejected to the grinding point in the same state. Therefore, it is possible to realize a uniform finished surface.

When manufacturing a hybrid lens,
By forming the female mold with the ultraviolet curable resin, it is possible to obtain the female mold of any shape with high accuracy and high mass productivity.

[0027]

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

1 and 2 are process explanatory views of a method for manufacturing a hybrid aspherical lens by a shape transfer method (replica method).

In the present invention, as shown in FIG. 2A, first, a glass lens to be molded (a non-axisymmetric aspherical lens made of glass) is prepared, and this is used as a prototype lens 1.
That is, as the original non-axisymmetric aspherical lens 1, for example, the one manufactured by the processing device described in Japanese Patent Laid-Open No. 2-53557 may be used.

Next, a female mold is produced based on this non-axisymmetric aspherical lens (original lens) 1. At this time, since the thickness of the ultraviolet curable resin layer forming the female mold surface is several tens of microns at most, the mechanical strength of the film is weak. Therefore, the opposite toric mold 2 having a value close to the radius of curvature of the original lens 1 is used as the base of the resin female mold. It is desirable that the material of the mold 2 as the base is one that is hardly deformed by heat, external force, humidity or the like. Further, since this female mold is repeatedly used, it is desired that the resin layer 4 forming the surface is a material having excellent adhesiveness to the base mold 2.
Here, brass is used as a base material. The surface of the brass mold is rough-processed in advance. This is to improve the adhesiveness between the mold surface and the resin layer 4.

For example, if rough sanding of the mold surface is performed by using No. 600 sandpaper, a surface having a maximum surface roughness of about 3 μm can be obtained. Since the average film thickness of the resin is about 30 μm, the unevenness of the mold surface does not affect the surface roughness of the completed female mold surface.

Next, the base mold 2 is thoroughly washed with an organic solvent such as acetone or isopropyl alcohol. Further, the surface of the mold 2 is subjected to ultraviolet irradiation ozone treatment for about 5 times.
After the treatment for a minute, a surface treatment agent is applied in order to promote the adhesiveness with the ultraviolet curable resin 3, and a heat treatment is performed at 80 ° C. for a sufficient time.

Next, as shown in FIG. 2 (b), an appropriate amount of the ultraviolet curable resin 3 is dropped onto the mold 2, the original lens 1 is placed thereon, and defoaming treatment is performed.

Next, as shown in FIG. 2 (c), ultraviolet rays are irradiated for 30 seconds. Here, the ultraviolet curable resin 3 is inserted between the original lens 1 and the mold 2 to form a single layer.

Next, as shown in FIG. 2D, the original lens 1 is removed from the female mold surface 4 ′ composed of the ultraviolet curable resin 3 and the mold 2.

Further, as shown in FIG. 1 (a), the same surface treatment as above is applied to the female mold surface 4'made of an ultraviolet curable resin in order to improve the adhesion, and the prototype lens 1
The resin layer 4 is laminated until there is no difference in shape between the female mold and the female mold. That is, the ultraviolet curable resin 3 is formed on the resin layer 4 on the mold 2.
Is dropped, and the original lens 1 is placed thereon to perform defoaming treatment, and ultraviolet rays are irradiated to form a number of resin layers 4. At least two resin layers are formed.

The female mold 2 is completed by the above steps.

A method for transferring the surface shape of the completed female mold (FIG. 1A) to the basic lens 5 is shown in FIGS.
It shows in (d). As a pre-process for moving to FIG. 1B, a basic lens 5 as a base of the hybrid lens is prepared. In order to improve the adhesiveness between the ultraviolet curable resin 3 and the basic lens 5, the basic lens 5 is surface-treated in the same manner as in the production of the female mold. Examples of the method for roughening the surface include a method of obtaining a predetermined surface roughness using fixed abrasive grains, a method of performing plasma asher, and a method of etching using hydrofluoric acid.
Furthermore, in order to improve the mold releasability between the female mold and the completed hybrid lens 6, after applying a mold release agent to the female mold surface,
As shown in FIG. 1B, an appropriate amount of the ultraviolet curable resin 3 is dropped on the basic lens 5 that is the base.

Next, as shown in FIG. 1 (c), this is pressed against the female mold surface 4 and then irradiated with ultraviolet rays for about 30 seconds to cure the resin 3.

Then, as shown in FIG. 1D, the hybrid lens 6 to which the non-axisymmetric aspherical surface layer has been transferred is released from the female mold. That is, the ultraviolet curable resin 3 is adhered to the basic lens 5, and the surface of the resin is numerically controlled to be the original shape 1 of the glass non-axisymmetric aspherical lens.
A hybrid lens 6 in which an ultraviolet curable resin layer having the same surface as that is laminated is obtained.

It is preferable that the ultraviolet curable resin constituting the surface of the female mold has a low hardness after curing and is easily adapted to the shape of the prototype lens 1. For example, STM4 (manufactured by Dainippon Ink and Chemicals, Inc.) or R6602 (manufactured by Nippon Synthetic Rubber Co., Ltd.)
Is preferred. Further, it is desirable that the ultraviolet curable resin for the hybrid lens 6 is a resin that is extremely close to the refractive index of the base glass lens 5 that is the base and has excellent environmental resistance.

A non-axisymmetric aspherical lens 1 used as a prototype for producing the female mold and the completed hybrid lens 6
And the result of measuring the shape of the basic lens 5 using a three-dimensional shape measuring machine is shown in FIG. The radius of curvature X ₁ of the original lens 1 is 45.251mm at the center of the lens, the maximum surface roughness of the surface was 0.152Myuemu. On the other hand, FIG.
As shown in (b), the radius of curvature X ₂ of the hybrid lens 6 manufactured according to the present invention is 45.2 at the center of the lens.
The surface roughness was 53 mm and the maximum surface roughness was 0.139 μm.
The basic lens 5 that is the base of the hybrid lens 6
Has a radius of curvature X ₃ of 44.115 mm at the center of the lens,
The maximum surface roughness was 3.426 μm. This proves that the lens manufacturing method of the present invention has very good transfer accuracy. In addition, 1mm by using a cutter on the resin layer surface
When 11 crosshatch-like scratches were made at intervals, and the crosshatch scratches were to be peeled off using cellophane tape, no single piece was peeled off. On the other hand, when this experiment was carried out using a hybrid lens in which resin was laminated on the surface of the basic lens that was finished to be extremely smooth, four out of 100 pieces composed of 11 cross-hatch scratches in the vertical and horizontal directions were used. Ten pieces were peeled off with cellophane tape.

In the above embodiment, the female mold was manufactured by the replica method. However, by manufacturing this female mold using glass of the same quality as that of the lens, the shape accuracy and surface accuracy of the female mold are the same as those of the glass lens. It is possible to maintain the same level.

Next, an embodiment of a method and apparatus for directly producing a female mold from concave glass by grinding will be described.
FIG. 4 shows the configuration of a processing apparatus based on the processing method for an axisymmetric aspherical object according to the present invention. The work (concave glass that is a workpiece) 7 is mounted on a rotary table 8 that is rotated by a DC servo motor.

The rotary table 8 is supported by angular contact ball bearings and rotates with a rotational runout accuracy of 0.1 μm. A rotary encoder 9 is directly connected to the shaft of the rotary table 8 to detect the rotation angle. Further, the rotary table 8 is provided on the linear table 10 using a cross roller guide. The linear table 10 is attached to a base 12 via a guide 11. This straight going table 10
A piezo actuator 13 is used to drive the. In order to numerically control the rectilinear table 10 with an accuracy of 0.01 μm, a capacitance type displacement detector 14 is used as a table position detector, and closed loop control is performed.

On the other hand, in order to process the work 7, the grindstone 1
5 is used, and this grindstone 15 is attached to an air spindle 16 with a built-in high frequency motor,
It rotates with high accuracy at a rotation speed of about 0000 rpm. Further, the air spindle 16 is centered on the air spindle holding shaft 17 installed so as to be orthogonal to the rotation axis thereof.
The worm 18 and the worm wheel 19 are configured to swing in an arc shape. Both ends of the air spindle holding shaft 17 are fixed by supporting members 20a and 20b. In order to improve the processing accuracy of the work 7, it is necessary to make the rotational runout of the rocking motion bearing 21 of the air spindle 16 almost zero. Therefore, the shake of the rotary shaft can be detected by using the capacitance type displacement detector 14, and the support member 20a that supports the rolling bearing (bearing 21) can be elastically deformed by the piezo actuator 13 to suppress the shake of the shaft to a small extent. It incorporates a possible controlled rotation mechanism.

Next, the aspherical surface processing will be described. Similar to the case of processing the toric surface described above, the grindstone 15 is moved in advance to the lower end of the work 7 which is the grinding start point. Here, the rotary table 8 is rotated, but in the case of aspherical surface processing, the grindstone 15 needs to accurately detect the grinding position on the surface of the work 7. To this end, the rotary encoder 9 directly connected to the rotary shaft of the rotary table 8
Then, the rotation angle θ of the rotary table 8 is measured with high accuracy. On the other hand, the air spindle 16 is step-fed for each revolution of the rotary table 8 and changes its position as in the case of the toric surface processing. That is, the contact position between the grindstone 15 and the work 7 changes. So, in advance,
The machining data calculated by using the rotation angle θ at each position of the air spindle 16 as a parameter is called from the memory, the pulse from the rotary encoder 9 is detected, and the machining data is obtained based on the pulse.
3, and the straight advance table 10 is continuously controlled. Then, when the rotary table 8 makes one rotation, the air spindle 16 is moved stepwise to bring the grindstone 15 to a new surface of the work 7. At the same time, the new machining data corresponding to the position is called from the memory, and when the grindstone 15 has moved to the upper end of the work 7 while repeating the above-mentioned operation, it means that the surface of the work 7 is all ground. The surface is an aspherical surface whose radius r in the sub-axis direction differs depending on the location, and is a deformed toric surface having a deviation d from the toric surface (that is, an axisymmetric aspherical surface).
The processing data is that the lens surface is decomposed into a lattice shape for each step of the swing of the air spindle 16 for the radius of the lens in the sub-axis direction, and for each pulse of the rotary encoder 9 for the radius of the main axis. , Numerical control data obtained by calculating the deviation amount at each point by a computer.

Further, the air spindle 16 is the support arm 2
2 and the distance between the air spindle shaft and the air spindle holding shaft 17 can be changed. Therefore, the relationship between the work 7 and the grindstone 15 is the radius r ′ of the grindstone 15 in FIG.
Is reduced by dressing or the like, the rotary table 8 with R-r = 1 (constant) is attached to the air spindle holding shaft 17
It is always positioned at a position distant from the center of rotation of 1 by 1 and the reference gauge of length R is brought out to the grindstone side with that position as the origin, and the air spindle 16 is fixed to the air spindle holding shaft 17
If the grindstone 15 is brought into contact with the reference gauge by moving the grindstone 15 toward, the relationship between the work 7 and the grindstone 15 (l = constant) is always satisfied. Actually, the radius r ′ due to the wear of the grindstone 15
There is a grinding allowance ε on the work 7 in addition to the decrease of This grinding amount also differs depending on the preprocessing and the like. In this case, when the work 7 is installed on the rotary table 8, the tip of the reference gauge is used as a stylus of an electric micrometer, and the distance from the reference position to the surface of the work 7 is measured to obtain the grinding allowance ε in advance. I ask for it. Then, the rotary table 8 is ground by ε.
The workpiece 7 and the grindstone 15 can be easily positioned in consideration of the grinding amount by setting the position of the grindstone 15 by setting the gauge to R + ε and setting the gauge to R + ε.

In addition to the above-mentioned basic functions, an embodiment of a processing force correction function, a rotary shake correction function of a rotary table, a grindstone height variable function, and a polishing function will be described. As shown in FIG. 7, the rotary shaft 23 of the rotary table 8 is held by the piezo actuator 13 in the xy directions via rolling bearings 24. Rotational runout of the rotary shaft 23 can be detected by using the capacitance type displacement detector 14, and the rotary shaft 23 held by the rolling bearing 24 can be slightly moved by the piezo actuator 13 to suppress the rotary runout small. It incorporates a controllable circuit mechanism.

On the other hand, as shown in FIG. 8, an air spindle 16 for rotating the grindstone 15 is provided on the linear table 25. This straight table 25 is a guide 26
It is attached to the support arm 22 via. The linear movement table 25 can finely adjust the linear movement using the piezo actuator 13. As a result, the air spindle 16 can move in the vertical direction with respect to the mounting surface of the support arm 22, and the vertical mounting height of the grindstone 15 with respect to the work 7 can be adjusted. The grindstone 15 used in the processing machine shown in this embodiment has a convex curved surface as shown in FIG. Therefore, when the grindstone 15 is replaced with another grindstone 15 ′, the machining point on the surface of the grindstone 15 ′ may change to the machining point 29 as shown in FIG. 9 depending on how the grindstone 27 is attached to the air spindle 16. If machining is continued in this state, the wound molding shape in the sub-axis direction changes, so that the machining accuracy of the work 7 is significantly reduced.

If the apparatus of the present invention has the function of adjusting the mounting height of the grindstone, it is possible to prevent the deterioration of the machining accuracy that occurs when the grindstone is replaced.

Further, FIG. 10 shows an example in which the air spindle 16 is held by the mounting member 32 from four directions via the machining force measuring piezo actuator 30 and the machining force controlling piezo actuator 31. FIG. 11 shows the force f applied to the piezo actuator 30 used for measuring the processing force.
The following is an example of the results of the investigation of the relationship between the generated voltage and the generated voltage.
The piezo actuator has a property of generating a voltage by a piezoelectric effect when a force is applied. As shown in FIG. 11, since there is linearity between the applied force f and the generated voltage V, the force applied to the piezoactuator can be known by detecting the generated voltage. The machining force f is detected by the machining force measuring piezo actuator 30, the generated voltage V at this time is compared with the machining force command voltage V ₀ , and the machining force controlling piezo actuator 31 is displaced so that the difference becomes zero.
As a result, if the machining force command value is kept constant even if the machining force fluctuates during grinding, the grinding force can be controlled to be constant. By performing the processing while keeping the processing force constant, it is possible to suppress the disturbance phenomenon such as the vibration of the device and the elastic deformation of the work caused by the variation of the processing force.

Further, in this apparatus, as shown in FIG. 12, a polisher 33 is attached in parallel with the grindstone 15. Although felt is used as the material of the polisher 33, this may be appropriately changed depending on the material of the work 7. Besides a fiber material such as felt, a chemical resin such as Teflon or a soft metal material such as tin may be used. As described above, since the present apparatus has a grindstone mounting height adjusting function, during polishing, the air spindle 16 is moved in the vertical direction and polishing is performed with the polisher 33 applied to the work 7. During polishing, the polishing liquid containing free abrasive grains such as diamond paste is applied to the work instead of the polishing liquid. Since this device has an aspherical surface generating function and a processing force control function, polishing can be performed without damaging the shape of the work 7.

In this embodiment, the case where the grindstone spindle shaft 34 is perpendicular to the surface of the support arm 22 has been described. However, as shown in FIG. Even if the angle is set only by ξ, processing is possible. In this case, since the contact portion between the grindstone 15 and the work 7 becomes large, the number of processing marks can be reduced.

Next, the above glass was ground by a grinding machine in which the nozzle portion was fixed, and the appearance of the finished surface was examined. In other grinding apparatus, since the nozzle is fixed, the supply of the grinding liquid to the grinding section becomes insufficient as the grindstone moves away from the center of the work. As a result, grinding failure occurs and the surface roughness of the finished surface decreases. FIG. 14 shows the results of observing the appearance of the surface near the end surface of the finished surface.
As can be seen from FIG. 14, even if the supply of the grinding fluid is insufficient, a smooth finished surface can be obtained when the work material is soft, but the greater the hardness of the material, the greater the influence of the supply state of the grinding fluid. The surface roughness of the receiving and finishing surface becomes large.

In the present invention, a method for supplying a grinding fluid as described below is used. FIG. 15 shows the configuration of a processing apparatus for grinding a non-axisymmetric aspherical female mold by NC control. Twenty nozzles 35 with an inner diameter of 1.5 mm are arranged along the trajectory of the circular arc motion of the grinding point, and the operating nozzles 35 are sequentially changed according to the movement of the grinding point to constantly apply the same amount of grinding fluid at the grinding point. I was in a state. The result of grinding by this method is shown in FIG. According to this method, since the grinding liquid is sufficiently applied to any surface of the work, it becomes possible to grind hard glass having poor grindability to a mirror surface.

As another example, if the controller for supplying the grinding fluid is not provided in order to simplify the equipment, the nozzle shape is made the same as the swing locus of the grinding point. In this way, the grinding fluid is sprayed along the swing locus of the grinding point, so that the way the grinding fluid is applied at the grinding point is always constant.

Next, a lens was actually prototyped by the replica method, and the waterproof property of the SiO protective film used in the present invention was confirmed.
The configuration of the lens manufactured in this example is shown in FIG. In this drawing, various dimensions such as a radius of curvature are emphasized in order to clearly show the lens shape. The present lens is a hybrid aspherical lens having a structure in which an ultraviolet curable resin layer 36 is laminated on the surface of a basic lens 5 having a toric shape to form an aspherical surface, and a protective film 37 made of SiO is further formed on the aspherical surface. FIG. 18 shows the manufacturing process of the present lens.
A fluorine-containing azide lubricant is applied as a release agent to the aspherical surface 4 of the female mold. The film thickness of the release agent may be about 1000Å or more. Next, the ultraviolet curable resin 3 is uniformly applied to the female mold surface 4, and the glass toric lens 5 is pressed thereon with a constant load W. Next, after irradiating ultraviolet rays for several minutes to cure the resin and transfer the aspherical shape to the glass lens surface, the lens 6 is pulled out from the female mold 59. Finally, a protective film 37 made of SiO 2 is formed on the surface of the aspherical lens 6 by a sputtering method. The film thickness at this time is 10Å. If the film thickness is up to about 1000Å, the influence on the optical characteristics of the lens can be ignored. When this lens was left in 100% humidity for 100 hours and the water absorption was evaluated by measuring the weight change, the water absorption rate was 0%, and a lens with extremely excellent weather resistance could be realized. It was The following experiment was conducted to confirm the effect of the protective film in the present invention.

The experiment was carried out on a 50 mm square glass substrate for 20
A basic sample was prepared by placing 0 mg of an ultraviolet curable resin and curing the resin. Next, in order to obtain a waterproof effect, a basic sample surface coated with a fluorine-based water repellent agent, and a basic sample surface coated with a SiO 2 protective film with a thickness of 50 Å by sputtering were prepared. Next, the water absorption was evaluated by measuring the weight change of the samples after leaving the samples in 100% humidity for a long time. The standing time was 65 hours and 90 hours. The results are shown in Table 1.

[0060]

[Table 1]

As a result of the experiment, both the basic sample containing only the resin and the sample obtained by coating the surface of the resin with the fluorine-based water repellent treatment, when left in high humidity for a long time, penetrates into the resin, but the SiO protective film is formed on the surface of the resin. It was found that no water intrusion was observed in the formed sample. However, the sample in which the resin surface is coated with the fluorine-based water repellent treatment has a surface energy smaller than that of the basic sample containing only the resin, and thus the sample is superior in water repellency to the basic sample.
That is, the surface is such that water droplets and dirt are unlikely to adhere.
Therefore, further adhering the water repellent treatment agent on the SiO protective film is an effective means for improving the waterproof property and the water repellent property. As the water repellent treatment agent used here, a silicone water repellent treatment agent is also effective in addition to the fluorine water repellent treatment agent.

FIG. 19 is a block diagram of the essential parts of a laser beam printer showing another embodiment of the present invention. In FIG. 19, 38 is an Fθ lens including a hybrid scanning lens according to the present invention, 39 is a laser light source, 40 is a collimator lens, 41 is a cylinder lens, 42 is a rotary polygon mirror, and 43.
Is the photosensitive drum surface.

Laser light 1 emitted from the laser light source 39
00 passes through the collimator lens 40 and becomes a parallel light flux. The cylinder lens 41 is arranged so as to act only in the sub-scanning direction. Here, the main scanning direction is the x direction (horizontal direction to the paper surface), and the sub scanning direction is the y direction (vertical direction to the paper surface). As a result, the laser light is focused on the reflecting surface 200 of the rotary polygon mirror 42 in the sub-scanning direction. In the sub-scanning direction, the rotary polygon mirror 42
The reflecting surface 200 and the photosensitive drum 43 are arranged, and these surfaces 200 and 43 are geometrically and optically conjugate with each other.

A scanning lens (Fθ lens) 38 for scanning a laser beam is a first lens having lens surfaces 44 and 45 on both sides, which have a rotational symmetry axis formed of a spherical surface or a plane.
It is composed of a second lens (a hybrid lens manufactured according to the present invention) having a lens surface 46 asymmetric about the rotation axis at one end. The scanning lens (Fθ lens) 38 has a function of narrowing a parallel light flux onto the photosensitive drum surface 43 for image formation in the main scanning direction (x direction). In the present embodiment, the radius of the rotary polygon mirror 42 is 32 mm and the number of surfaces is 8,
The incident angle of the incident laser light is 66 °.

FIG. 20 is a diagram showing the image forming characteristics of the Fθ lens in FIG.

The laser beam scanned by the rotary polygon mirror 42 shown in FIG. 19 is converted into a scanning lens (Fθ
As for the image forming characteristics when an image is formed by the lens 38, as shown by the solid line in FIG. 20, the field curvature can be suppressed within 2 mm within the range of the scanning angle of view ± 29 °. In the experiment, 60 × 1
It was possible to obtain a uniform focused spot of 00 μm. The broken line in FIG. 20 represents the image plane position in the sub-scanning direction when an asymmetric surface shape is not added, that is, when the symmetrical cylinder lens deflects and scans the laser light onto the photosensitive drum. As can be seen from FIG. 20, when the asymmetrical surface shape is not added, the image plane curvature spreads to nearly 20 mm within the scanning angle of view of 29 °. From the above results, it can be seen that the image plane curvature of the laser light according to the present invention is minute.

[0067]

As described above, according to the present invention, it is possible to create a concave surface having an axisymmetric aspherical surface shape with high accuracy and mass productivity. In the processing apparatus of the present invention, a non-axisymmetric aspherical concave lens can be directly ground by using optical glass as the material of the work. Further, if hard ceramics is selected for the work, the female mold for molding can be processed, and it becomes possible to mass-produce the non-axisymmetric aspherical lens having excellent optical characteristics at low cost by molding. Furthermore, by using the non-axisymmetric aspherical lens of the present invention in a laser beam printer, it is possible to perform high-quality printing with little image plane distortion. Further, the non-axisymmetric aspherical lens of the present invention can be used as a lens for a laser fax, a digital copying machine, an image reader, a camera or the like.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing a manufacturing method of an axisymmetric aspherical hybrid lens showing an embodiment of the present invention.

FIG. 2 is a process explanatory view showing a method for manufacturing a non-axisymmetric aspherical female mold showing one embodiment of the present invention.

FIG. 3 is a diagram showing shapes of an original glass lens and a hybrid lens having an axisymmetric aspherical surface.

FIG. 4 is a configuration diagram of a non-axisymmetric aspherical female processing apparatus.

FIG. 5 is a view showing the shape of a non-axisymmetric aspherical female mold.

FIG. 6 is a view showing a relationship between a grindstone, a work, a swing center, and a rotation center.

FIG. 7 is a diagram showing a rotational shake correction mechanism of a rotary table showing an embodiment of the present invention.

FIG. 8 is a diagram showing an air spindle moving mechanism showing an embodiment of the present invention.

FIG. 9 is a diagram showing a mounting error when the grindstone is mounted.

FIG. 10 is a diagram showing a processing force control mechanism showing an embodiment of the present invention.

FIG. 11 shows the relationship between the force and the generated voltage of the machining force detecting piezo actuator applied to the present invention.

FIG. 12 is a view showing a polishing mechanism showing one embodiment of the present invention.

FIG. 13 is a configuration diagram showing a non-axisymmetric aspherical female processing device when a grinding shaft is tilted according to an embodiment of the present invention.

FIG. 14 shows the relationship between the surface roughness of the ground finished surface and the material hardness.

FIG. 15 is a configuration diagram showing a non-axisymmetric aspherical female machining apparatus having an injection control nozzle according to an embodiment of the present invention.

FIG. 16 shows the relationship between the surface roughness of the ground finished surface and the material hardness.

FIG. 17 is a diagram showing the structure of a lens with a protective film.

FIG. 18 is a diagram showing the manufacturing process of the lens with the protective film.

FIG. 19 is a configuration diagram of a main part of a laser beam printer showing an embodiment of the present invention.

FIG. 20 is a diagram showing the imaging characteristics of an Fθ lens.

FIG. 21 is a diagram showing a scanning optical system of a general laser beam printer.

FIG. 22 is a diagram showing an image forming system of a general laser beam printer.

FIG. 23 is a diagram showing a positional relationship between a work and a nozzle in the female processing apparatus.

FIG. 24 is a diagram showing a positional relationship between a workpiece and a nozzle in the female processing apparatus.

FIG. 25 is a view showing a positional relationship between a work and a nozzle in the female processing apparatus.

[Explanation of symbols]

1 ... Axisymmetric aspherical lens (original lens), 2 ... Toric mold, 3 ... UV curable resin, 4 ... Female surface, 5
... Basic lens, 6 ... Hybrid lens, 7 ... Work (concave glass), 8 ... Rotating table, 9 ... Rotary encoder, 10 ... Linear table, 11 ... Guide, 12 ...
Base, 13 ... Piezo actuator, 14 ... Capacitive displacement detector, 15 ... Grinding stone, 16 ... Air spindle, 1
7 ... Air spindle holding shaft, 18 ... Worm, 19 ... Worm wheel, 20a ... Support member, 20b ... Support member, 21 ... Oscillating motion bearing, 22 ... Support arm, 23 ...
Rotating shaft, 24 ... Rolling bearing, 25 ... Linear table, 26
… Guide, 27… Whetstone, 28… Machining point, 29… Machining point,
30 ... Piezo actuator for measuring processing force, 31 ... Piezo actuator for controlling processing force, 32 ... Mounting member, 3
3 ... Polisher, 34 ... Whetstone spindle shaft, 35 ... Plural nozzles, 36 ... UV curable resin, 37 ... Protective film, 3
8 ... Imaging lens (Fθ lens), 39 ... Light source, 40 ... Collimator lens, 41 ... Cylinder lens, 42 ... Rotating polygon mirror (polygon mirror), 43 ... Photoconductor, 44 ... Lens surface, 45 ... Lens surface, 46 … Lens surface, 47… Modulator,
48a ... Beam compressor, 48b ... Beam expander, 49 ... Plus corona, 50 ... AC corona current, 5
DESCRIPTION OF SYMBOLS 1 ... Exposure device, 52 ... Developing device, 53 ... Paper feed cassette, 54
... Paper feed roller, 55 ... Fixing device, 56 ... Stacker, 57 ...
Cleaning, 58 ... Cleaning blade, 59 ... Female type, 60 ... Nozzle, 100 ... Laser light, 200 ... Reflecting surface, 300 ... Orbit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fumihiko Uchida 1-280 Higashi Koikekubo, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Inventor Shigeo Moriyama 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. Central Research Laboratory (72) Inventor Akira Arimoto 1-280, Higashi Koigokubo, Kokubunji, Tokyo Hitachi Research Laboratory, Central Research Laboratory

Claims (25)

[Claims] 1. A scanning optical device comprising a light source, a scanning means for scanning the light emitted from the light source, and a scanning lens for narrowing the light scanned by the scanning means onto a medium, wherein the scanning lens is a basic glass. A scanning optical device, wherein a resin made of a transparent organic polymer material having a refractive index substantially equal to that of the basic glass lens is laminated on the lens to form an integrally bonded structure. 2. A laser beam printer comprising a laser light source, a rotary polygon mirror for scanning light from the laser light source, and a scanning lens for narrowing the light scanned by the rotary polygon mirror onto a photosensitive drum surface. A laser beam printer, wherein a surface of the scanning lens on the side of the photosensitive drum is formed of at least a resin made of an organic polymer material. 3. The scanning lens is formed by laminating the resin on a basic glass lens, the resin having substantially the same refractive index as the basic glass, and the surface of the basic glass laminating the resin is The laser beam printer according to claim 2, wherein the laser beam printer is roughened by minute irregularities, and the irregularities have a maximum surface roughness of 0 μm to 20 μm. 4. The aspherical shape of the scanning lens, wherein the main layer and the sub-axis of the resin layer of the resin layer have different radii of curvature, and asymmetrically increases as the radius of curvature of the sub-axis becomes off-axis. The laser beam printer according to claim 1, further comprising: 5. SiO or SiO _{2 is} formed on the surface of the lens layer.
The laser beam printer according to claim 4, wherein a protective film made of is provided. 6. The laser beam printer according to claim 5, wherein the protective film thickness is 1000 Å or less. 7. The resin according to claim 2, which is an ultraviolet curable resin.
7. The laser beam printer according to any one of 6 to 6. 8. A glass lens having minute irregularities on the surface and a female mold having a predetermined lens shape are prepared, and a resin of an organic polymer material having a refractive index substantially equal to that of the glass lens is dropped on the female mold. Then, the glass lens is pressed against the female mold, the resin is processed into a lens shape, and the lens portion and the glass lens portion are integrally joined and molded, thereby producing a hybrid scanning lens. 9. The resin is an ultraviolet curable resin.
A method of manufacturing the hybrid scanning lens according to 1. 10. The method for manufacturing a hybrid scanning lens according to claim 8, wherein a protective film made of SiO or SiO ₂ is formed on the resin. 11. A method of manufacturing a lens, which comprises a resin made of an organic polymer material or a resin made of an organic polymer material in a part of a lens body, is heat-treated, and the lens surface is irradiated with ozone for a certain period of time and then protected. A method for manufacturing a lens, which comprises forming a film. 12. A method for processing a non-axisymmetric aspherical female die used for transferring the shape of a non-axisymmetric aspherical scanning lens, in which a workpiece is rotated and a rotation axis of a grindstone spindle for machining the workpiece. In the method of processing a workpiece by circularly moving a grinding stone spindle axis in a plane including the rotation axis of the workpiece, the grinding stone spindle having a predetermined angle with the plane including the rotation axis of the workpiece. An axis, the grindstone spindle axis is located between the center of rotation of the workpiece and the workpiece, and the grindstone spindle axis and the workpiece are associated with the rotation angle position of the workpiece. A method for processing an aspherical female die, which is controlled so that a spatial positional relationship with an object changes. 13. The method for machining an aspherical female die according to claim 12, wherein the rotation center axis position of the workpiece is controlled so as to change corresponding to the rotation angle position. 14. The predetermined angles are parallel to each other.
Or the processing method for an aspherical female die according to item 13. 15. The machining of an aspherical female die according to claim 12, wherein a plurality of grinding fluid injection nozzles are provided along a movement locus of a grinding point where the workpiece and the grindstone spindle are in contact with each other. Method. 16. A rotating means for rotating a workpiece, a grindstone spindle equipped with a grindstone for machining the workpiece, a means for circularly moving the grindstone spindle axis, and a rotation angle of the workpiece. And a means for changing the distance between the rotation axis of the work piece and the center axis of the circular arc movement of the grindstone spindle, and the cause of rotation of the grindstone spindle is the rotation center of the work piece and the work piece. An aspherical female machining device characterized by being arranged between them. 17. The aspherical surface female machining apparatus according to claim 16, further comprising a nozzle for ejecting a grinding fluid at a contact point between the workpiece and the grindstone, and a means for controlling a jetting position of the grinding fluid. 18. The aspherical surface female machining apparatus according to claim 17, further comprising means for making an arc motion of the grindstone spindle axis in the sub-axis direction of the workpiece and means for correcting the locus of the arc motion. 19. A means for moving said grindstone spindle in a direction perpendicular to a plane of its supporting member.
8. The aspherical female processing device according to item 8. 20. A means for detecting a processing force applied to the grindstone,
The grinding wheel position moving means is provided, and the grinding wheel position is controlled by the position moving means so as to eliminate a difference between a preset machining force signal and a signal of the machining force detecting means. The aspherical female processing device described. 21. The aspherical female machining apparatus according to claim 18, further comprising a rotational shake detecting means of the rotating device of the workpiece and a rotational shake correcting means of the rotating device. 22. The aspherical surface female machining apparatus according to claim 18, 20 or 21, wherein a polishing polisher is arranged coaxially with said grindstone spindle to perform polishing. 23. A rotating device for a workpiece, a grindstone spindle having a grindstone for machining the workpiece, means for moving the axis of the grindstone spindle in an arc, a rotary shaft for the workpiece and the grindstone. A means for changing the distance between the central axes of the circular arc movements of the spindle, a detector for detecting the rotational angular position of the work piece, a means for detecting the angular position of the circular arc movements of the grindstone spindle, and these detected The grindstone spindle includes a control device configured to change the inter-axis distance and the injection position of the grinding fluid based on the control data stored in advance in the storage means in correspondence with the two angular position signals. A processing device for an aspherical object, which is arranged between the center of rotation of a workpiece and the workpiece. 24. A plastic female part made of a resin of an organic polymer material and a basic female part are integrally joined and molded by a shape transfer method using a lens having a predetermined lens shape on the surface of the basic female mold having minute irregularities. A method for manufacturing a hybrid scanning lens using a female die processed by a processing method characterized by: 25. A scanning lens, wherein at least a curved surface having an axisymmetric aspherical shape is formed of plastic.