JPH0820077A - Formation of optical surface - Google Patents

Abstract

PURPOSE:To realize highly accurate non-spherical surface processing by setting off the defects of both of optical glass and optical plastic. CONSTITUTION:The reflected wave surface of the lens surface 4 of an optical lens 1 formed by coating the surface of a matrix composed of optical glass with a resin for an optical element is measured by an interferometer 5 and the lens surface 4 is scanned on the basis of the monitoring data of a computer system by short wavelength ultraviolet laser L while the reflected wave surface due to the interferometer 5 is monitored by the computer system 7 to be etched in a non-contact state by short wavelength ultraviolet laser L to be processed into a shape becoming the optimum reflected wave surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an optical surface, and more specifically, it requires an application field requiring a high performance optical lens (camera, measuring device, laser printer, etc.) and an optical element having a large diameter. The present invention relates to a method for forming an optical surface for manufacturing a lens, a mirror, and the like required for a projector, a large-sized laser device, and a lithographic apparatus with high accuracy.

[0002]

2. Description of the Related Art For example, in a precision machining laser device or the like, a highly accurate optical lens, a reflection mirror, or the like is required to focus a laser on a minute spot. Generally, an optical element of this type [hereinafter referred to as an optical lens] is roughly classified into an optical glass composition and an optical plastic composition.

In an optical lens composed of either one of them, the shape of its optical surface [hereinafter referred to as a lens surface] has a great influence on the condensing characteristics of laser light. That is, even if the laser incident on the optical lens has a parallel wavefront, if the optical lens has a wavefront aberration, the focused spot diameter of the laser light is increased, and as a result, the focused intensity is increased. descend.

Therefore, in the above-mentioned optical lens, it is necessary to form a lens surface such that the laser focused on a point has a minimum spot diameter. Therefore, the formation of this lens surface is currently performed by the following aspherical surface processing. For optical lenses with optical plastic composition, for example, aspherical surface processing is performed by cutting or in-mold molding, and for optical lenses with optical glass composition, polishing processing or glass melting is performed. Aspherical surface processing is performed by pressing.

[0005]

By the way, with an optical lens composed only of optical plastic, it is easy to perform the above-described highly accurate aspherical surface processing, but on the other hand, the optical distortion in the aspherical surface processing is large, and However, there is a problem that the focal length fluctuates due to temperature change and the effect of thermal expansion is large, and furthermore, there is a problem that the refractive index changes due to the absorption of water due to a change over time, and the focal length fluctuates, which is not preferable. .

On the other hand, an optical lens composed only of optical glass is suitable because it has a small optical distortion in aspherical surface processing and is less affected by temperature change and thermal expansion and changes over time. The processing itself was very difficult. That is, the skill level of the operator is required, and the work of inspecting the surface condition of each process must be repeated. The skill level is required and the processing work takes time, and in any case, it is high. It was difficult to realize accurate aspherical surface processing.

Therefore, the present invention has been proposed in view of the above problems, and an object of the present invention is to cancel the defects of both optical glass and optical plastic and realize highly precise aspherical surface processing. It is to provide a method for forming a lens surface.

[0008]

As a technical means for achieving the above object, the method of the present invention is an optical surface obtained by coating a surface of a matrix made of optical glass with a resin for an optical element, or optical glass or quartz. It is characterized in that the optical surface of the matrix made of glass is processed into an optimal transmission wavefront or reflection wavefront.

Further, the method of the present invention monitors the optical surface obtained by coating the surface of a matrix made of optical glass with a resin for optical element, or the transmitted wave surface or the reflected wave surface of the optical surface of a matrix made of optical glass or quartz glass. However, based on the monitoring information, the optical surface is etched in a non-contact manner by irradiation with a short-wavelength ultraviolet beam so as to be processed into an optimum shape of a transmitted wave surface or a reflected wave surface.

[0010]

In the lens surface forming method according to the present invention, an optical surface obtained by coating the surface of a base made of optical glass with a resin for an optical element, or an optical surface of a base made of optical glass or quartz glass is to be processed. Therefore, as an advantage of the optical glass, the optical distortion in the aspherical surface processing is small and the optical characteristics are good. Further, in the case of an optical surface coated with a resin for an optical element, the advantage of the resin for an optical element is that it is easy to realize highly accurate aspherical surface processing.

Further, while monitoring the transmitted wavefront or the reflected wavefront of the optical surface, the optical surface is etched in a non-contact manner by irradiation of a short wavelength ultraviolet beam based on the monitoring information, so that the optimum transmitted wavefront or reflected wavefront is obtained. Can be set as a target in real time, and as an advantage of the short-wavelength ultraviolet beam, the surface after etching can be smoothly processed to enable fine surface processing.

[0012]

EXAMPLE An example of a method for forming a lens surface according to the present invention will be described with reference to FIGS. 1 and 2 are examples of an optical surface obtained by coating the surface of a matrix made of optical glass with a resin for optical elements, and FIGS. 3 and 4 show examples of the optical surface of a matrix made of optical glass or quartz glass. This is an example. 1 and 3 show the case where the reflected wavefront of the lens surface is monitored in each embodiment, and FIGS. 2 and 4 show the case where the transmitted wavefront of the lens surface is monitored.

As shown in FIG. 1 or 3, the optical lens 1 which is the object to be processed is supported and fixed while being positioned by an appropriate means. The optical lens 1 shown in FIG. 1 has an optical element resin 3 such as polymethylmethacrylate (PMMA) or polycarbonate on the surface of a base 2 made of optical glass such as BK7. It is coated so that Also, FIG.
The optical lens 1'shown in (1) is a matrix 2'itself made of optical glass or quartz glass.

An interferometer 5 is arranged so as to face the lens surfaces 4, 4'which are the surfaces to be processed of the optical lenses 1, 1 '. Further, the mirror 6 is arranged so as to face the optical lenses 1, 1 ′, behind the optical lenses 1, 1 ′, that is, on the side opposite to the interferometer 5.

The interferometer 5 is connected to a computer system 7, and for example, red light [633 nm] or green light [5
43 nm] an optical system including a light source such as a He-Ne laser and a CCD camera, and the measurement laser S emitted from the light source is reflected on the surface of the optical lens 1, 1 ′ and is a plane built in the interferometer. CC by interfering with the reflected light from the reference plate
Take an image with the D camera. The image pickup signal from the CCD camera is image-processed by the computer system 7, and the lens surface 4,
Monitor the reflected wavefront at 4 '. This monitoring can be displayed on the screen of the display device of the computer system 7.

On the other hand, a laser oscillator 8 is arranged between the optical lenses 1 and 1'and the interferometer 5, and a mirror 9 is movably arranged in front of it. This laser oscillator 8 is, for example, 11
An ultraviolet laser having a short wavelength of 0 to 220 nm is used as a light source. As the ultraviolet laser, when the resin for optical element 3 is coated as shown in FIG.
An excimer laser made of ArF having a short wavelength of 3 nm is preferable, and in the case of silica glass as shown in FIG. 3, a fluorine laser having a short wavelength of 153 nm is preferable,
In addition, a hydrogen laser or the like can be used. In addition to the laser oscillator 8, it is also possible to use a structure in which an ultraviolet lamp such as an ArF ultraviolet lamp is used as a light source to irradiate an ultraviolet beam. When using a vacuum ultraviolet light source that has a large absorption in air, the entire system is placed in a container and the gas is replaced with Ar gas or the like, or the system is evacuated to a vacuum and used.

The mirror 9 has lens surfaces 4, 4 '.
A drive source 10 is provided so as to be capable of two-dimensional XY movement on the surface facing the interferometer 5 and the drive source 10 is connected to the computer system 7 and can be controlled.

In the method of the present invention, the optical lenses 1, 1 '
While monitoring the reflected wavefronts of the lens surfaces 4, 4'of the lens surfaces 4, 4 ', based on the monitoring information,
4'is etched in a non-contact manner by the short wavelength ultraviolet lasers L, L ', and the surface is processed into a shape that provides an optimum reflected wave front.
Specifically, the monitoring of the reflected wavefronts of the lens surfaces 4 and 4'is performed by the computer system 7 by the interferometer 5 facing the lens surfaces 4 and 4 '. The surface processing of the lens surfaces 4 and 4'is performed by reflecting the short wavelength ultraviolet lasers L and L'generated from the laser oscillator 8 on the mirror 9 and irradiating the lens surfaces 4 and 4 '. The short wavelength ultraviolet laser L can be irradiated onto the entire lens surface by moving the mirror 9 arbitrarily in the XY directions by the driving source 10.

More specifically, the measurement laser S emitted from the light source of the interferometer 5 is reflected by the surfaces of the optical lenses 1 and 1 ', and the reflected light is imaged by the CCD camera of the interferometer 5. By subjecting the image pickup signal from the CCD camera to image processing by the computer system 7, the phase distribution obtained from the interference fringes generated on the lens surfaces 4 and 4 ′ is displayed on the screen of the computer system 7, and the lens surface 4 and The wavefront reflected by the measuring laser S passing through 4'is monitored.

Based on the monitoring of the reflected wavefronts of the lens surfaces 4, 4 ', the computer system 7 determines the surface state of the lens surfaces 4, 4', and the target lens surface 4, 4'is determined from the surface state. In order to form, the drive source 10 of the mirror 9 is controlled by the output from the computer system 7. On the other hand, by irradiating the lens surfaces 4 and 4 ′ with the short wavelength ultraviolet lasers L and L ′ emitted from the laser oscillator 8 by the mirror 9, the resin 3 for the optical element of the lens surface 4 or the quartz of the lens surface 4 ′. The glass is contactlessly etched.

At this time, the light source is a short wavelength ultraviolet laser L,
By using L ′, the C—C bond of the polymer material is broken near the surface of the optical element resin 3 to decompose the polymer into the monomer, and SiO ₂ is scattered on the surface of the quartz glass. , The surface after etching can be processed smoothly.

The etching with the short wavelength ultraviolet lasers L and L'is performed while the mirror 9 is moved over the entire lens surfaces 4 and 4'under the control of the driving source 10 by the computer system 7. At this time, as described above, by controlling the stop position of the mirror 9 based on the monitoring information of the reflected wavefronts of the lens surfaces 4, 4 ', the lens surfaces 4, 4'by irradiation with the short wavelength ultraviolet lasers L, L'.
By appropriately setting the etching position in step 1 and controlling the moving speed of the mirror 9, the irradiation light amount consisting of the pulse number and intensity of the short wavelength ultraviolet lasers L, L'is set appropriately, and the lens surface 4 , 4 ′ is set to an optimum value to correct the reflected wavefronts of the lens surfaces 4 and 4 ′ to form a lens surface having a desired reflected wavefront.

When the formation of the one lens surface 4, 4'opposed to the interferometer 5 is completed, the optical lens 1 is inverted to form the other lens surface 4, 4'in the same manner as described above. To implement.

In the above embodiments, the case of monitoring the reflected wavefronts of the lens surfaces 4 and 4'has been described, but the present invention is not limited to this, and the optical lens 1 as shown in FIG. 2 or FIG. , 1'arrange the mirror 9 behind,
The transmitted wavefronts of the lens surfaces 4 and 4'may be monitored. Further, according to the present invention, it is possible to process an optical element made of only the resin for optical elements. Also, instead of moving the mirror 9, the optical lens 1,
1'may be moved on a moving stage.

Further, the present invention can be applied to various optical lenses other than the optical lens used in a precision machining laser device or the like for converging a uniform laser.

[0026]

EFFECTS OF THE INVENTION According to the method of the present invention, an optical surface obtained by coating the surface of a base made of optical glass with a resin for optical elements, or an optical surface of a base made of optical glass or quartz glass is to be processed. , And, while monitoring the transmitted wavefront or the reflected wavefront of the optical surface, from the point that the optical surface is etched in a non-contact manner by irradiation with a short-wavelength ultraviolet beam based on the monitoring information to perform surface processing. Optimal from the advantages of short wavelength UV beam that has a small optical distortion and good optical characteristics, or has the advantage that high-precision aspherical surface processing can be easily realized and the surface after etching can be processed smoothly. It is possible to easily manufacture an optical surface having a transparent wavefront or a reflected wavefront, and its practical value is great.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an apparatus configuration in the case of monitoring a reflected wavefront of a lens surface in an example of an optical surface coated with a resin for an optical element.

FIG. 2 is a schematic diagram showing an apparatus configuration in the case of monitoring a transmitted wave front of a lens surface in an example of an optical surface coated with a resin for optical elements.

FIG. 3 is a schematic diagram showing an apparatus configuration in the case of monitoring a reflected wavefront of a lens surface in an example of an optical surface of a base made of optical glass or quartz glass.

FIG. 4 is a schematic diagram showing an apparatus configuration in the case of monitoring a transmitted wave front of a lens surface in an example of an optical surface of a base made of optical glass or quartz glass.

[Explanation of symbols]

 2 Base 2'Base [quartz glass] 3 Optical element resin 4 Optical surface [lens surface] 4'Optical surface [lens surface] L Short wavelength ultraviolet beam [short wavelength ultraviolet laser] L'Short wavelength ultraviolet beam [short wavelength ultraviolet beam] laser〕

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Nobuaki Nakajima 2-6 Yamadaoka, Suita City, Osaka Prefecture Laser Research Center for Fusion Research, Osaka University (72) Masahiro Nakatsuka 2-6 Yamadaoka, Suita City, Osaka Prefecture Osaka University Laser Fusion Research Center (72) Inventor, Keiyu Tokumura, 3-2-30 Minamieguchi, Higashiyodogawa-ku, Osaka-shi, Osaka

Claims (4)

[Claims] 1. A method of forming an optical surface, characterized in that a surface of a matrix made of optical glass is coated with a resin for an optical element, and the optical surface is processed into an optimum transmission wave surface or a reflection wave surface. 2. A method of irradiating a short-wavelength ultraviolet beam on the optical surface based on the monitoring information while monitoring a transmitted wave surface or a reflected wave surface of an optical surface obtained by coating a surface of a base body made of optical glass with a resin for an optical element. A method for forming an optical surface, characterized in that etching is performed in a non-contact manner so as to be processed into an optimum shape of a transmitted wave surface or a reflected wave surface. 3. A method of forming an optical surface, characterized in that an optical surface of a matrix made of optical glass or quartz glass is processed into an optimum shape of a transmitted wave surface or a reflected wave surface. 4. The non-contact etching of the optical surface of the matrix made of optical glass or quartz glass by irradiating a short wavelength ultraviolet beam on the basis of the monitoring information while monitoring the transmitted wave surface or the reflected wave surface of the optical surface. A method for forming an optical surface, characterized in that the optical surface is processed into an optimum transmitted wave surface or reflected wave surface.