JPH11106901A5 - Optical thin film forming apparatus, optical thin film forming method, and optical element having a thin film formed on its surface by this method - Google Patents

Description

[0001]
[Technical Field to which the Invention Belongs]
The present invention relates to an apparatus and method for depositing an optical thin film (e.g., a reflective film, an anti-reflective film, etc.) on the surface of an optical element such as an optical lens or a mirror, and to an optical element having a thin film deposited on its surface by this method .

The film formation process is performed by evacuating the film formation chamber 101 and heating and evaporating the deposition material 102b with a heater or electron gun 102a in the deposition source 102. The deposition particles are diffused as shown by arrow A and adhere to the surface of the optical element L to form a thin film. At this time, a correction plate 105 is disposed as shown in the figure to prevent unevenness in the film thickness distribution due to factors such as the reach distance of the particles from the deposition source 102. As can be clearly seen from the figure, this correction plate limits to some extent the deposition of deposition particles in a direction close to perpendicular incidence to the optical element L (the amount of deposition at the center of the optical element) and reduces the limitation on the deposition of deposition particles in an oblique incidence direction (near the periphery of the optical element), thereby achieving a uniform film thickness distribution.

Furthermore, the optical element L is not only rotated and revolved but also swung to change the angle between the deposition source 102 and the optical element L, thereby achieving a uniform film thickness distribution. Conventionally, the correction plate 105 has been shaped so that the surface of the optical element L is flat or curved with a large radius of curvature (a curved surface with a small curvature) to prevent film thickness unevenness.

In view of these problems, the present invention aims to provide an optical thin film deposition apparatus and an optical thin film deposition method that can minimize film thickness variations even in the case of lenses with large curvatures, and an optical element having a thin film deposited on its surface by this method .

[0007]
[Means for solving the problem]
To achieve this object, in the present invention, an optical thin film deposition apparatus is configured by providing, in a deposition chamber, an element support section that supports an optical element and causes it to revolve orbitally or on its axis, and a deposition source that generates deposition particles for forming a thin film, and in this case, a plurality of deposition sources are provided. By providing a plurality of deposition sources in this manner, deposition particles are made incident on the revolving or axis-revolving optical element from a plurality of directions to form a thin film, so that even for optical elements such as lenses with large curvatures, it is possible to achieve a uniform film thickness distribution on the surface.

That is, by using the film formation apparatus of the present invention, a film is formed on the entire surface of an optical element using deposition particles diffused and emitted from a single deposition source, as in the conventional case. Here, deposition particles from a deposition source with an incident angle close to normal incidence among the multiple directions are most efficiently deposited on each part of the surface of the optical element to form a film. Even in the case of an optical element with a surface shape with a large curvature, it is possible to have a deposition source with an incident angle close to normal incidence at almost all positions on the surface, thereby achieving a uniform film thickness distribution.

It is preferable that each of these multiple evaporation sources be arranged at a different distance from the orbital axis of the element support part, which allows the evaporation particles to be incident on the optical element in different directions and at different angles of incidence, and to adhere to the surface of the optical element, thereby making the film thickness distribution more uniform.

For the same purpose, it is preferable to provide an aperture member between each of the multiple evaporation sources and the optical element supported by the element support, which limits the diffusion direction of the evaporation particles from each evaporation source. This aperture member can limit the angle of incidence of the evaporation particles reaching the optical element from each of the multiple evaporation sources, thereby controlling the film thickness distribution of the thin film formed on the surface of the optical element. By limiting the angle of incidence in the direction of oblique incidence, the film thickness distribution can be further uniformed. Furthermore, providing a correction plate (similar to a conventional correction plate that limits the amount of deposition in the portion close to perpendicular incidence) between the aperture member and the optical element supported by the element support can further uniformize the film thickness distribution. The optical thin film deposition method of the present invention includes an installation step of supporting an optical element in a sealable deposition chamber, arranging a plurality of evaporation sources for forming a thin film on the surface of the optical element, and providing an aperture member between the optical element and the plurality of evaporation sources; and a deposition step of orbiting or rotating/revolving the supported optical element, generating evaporation particles from the plurality of evaporation sources, and adjusting the adhesion of the evaporation particles to the surface of the optical element using the aperture plate to deposit a thin film on the surface of the optical element, wherein the aperture member limits the angle of incidence of the evaporation particles reaching the optical element from the plurality of evaporation sources. It is also preferable that the plurality of evaporation sources are arranged at different distances from the orbital axis of the optical element. The optical element of the present invention has a thin film deposited on its surface by the above-described optical thin film deposition method.

[0011]
[Embodiments of the Invention]
Preferred embodiments of the present invention will now be described with reference to the drawings. Fig. 1 shows a first embodiment of an optical thin film deposition apparatus according to the present invention. This apparatus 10 is configured by disposing two vapor deposition sources 11 and 12 in a deposition chamber (not shown) similar to that shown in Fig. 4. The deposition chamber also includes a support mechanism (not shown) that supports a lens L so that it can rotate (arrow C), and aperture plates 15 and 16 are provided between the lens L and the respective vapor deposition sources 11 and 12 (installation step) .

The lens L supported by the support mechanism rotates around a vertically extending rotation axis X as indicated by arrow C. The evaporation sources 11 and 12 heat and evaporate evaporation materials 11b and 12b using electron guns 11a and 12a, respectively, to diffuse evaporation particles. The evaporation source 11 is disposed directly below the lens L (below the rotation axis X), while the evaporation source 12 is disposed diagonally below the lens L. The aperture plates 15 and 16 have circular or elliptical openings 15a and 16a, respectively, which face the center and periphery of the lower surface of the lens L when viewed from the evaporation sources 11 and 12, respectively.

To form an optical thin film on the surface of the lens L using this film forming apparatus 10, the film forming chamber is first evacuated to a vacuum, and then the electron guns 11 a, 12 a heat, evaporate, and diffuse the deposition materials 11 b, 12 b. The deposition particles diffused in this manner diffuse as indicated by arrows A1 to A4, but the deposition particles diffused in the directions indicated by arrows A2 and A4 are blocked by aperture plates 15, 16, and only the deposition particles diffused in the directions indicated by arrows A1 and A3 pass through openings 15 a, 16 a, reach and adhere to the surface of the lens L, and form an optical thin film (film forming process) .

In this example, the deposition particles diffused from the deposition source 11 in the direction of arrow A1 head toward the central portion of the lower surface of the lens L, and reach and adhere to the surface of the lens L in a state of nearly normal incidence. On the other hand, the deposition particles diffused from the deposition source 12 in the direction of arrow A3 are incident obliquely on the periphery of the lower surface of the lens L, and also reach and adhere to the periphery of the lower surface of the lens L in a state of nearly normal incidence. That is, the deposition particles from the deposition source 11 adhere to the central portion of the lower surface of the lens, and from the deposition source 12 adhere to the periphery of the lower surface of the lens in a state of nearly normal incidence, forming an optical thin film. Therefore, efficient thin film formation is achieved in both portions, and the film thickness distribution is uniform.

FIG. 2 shows a second embodiment of an optical thin-film deposition apparatus according to the present invention. This apparatus 20 also includes a deposition chamber (not shown) containing two deposition sources 21 and 22. The deposition chamber also contains a support mechanism (not shown) for supporting multiple lenses L so that they can revolve (arrow B) and rotate (arrow C). Diaphragm plates 25 and 26 are provided between the lenses L and the deposition sources 21 and 22 (installation step) . The deposition sources 21 and 22 have the same configuration as the deposition sources 11 and 12 of the first embodiment. The deposition source 21 is disposed below the orbital path of the lens L, and the deposition source 22 is disposed diagonally below the lens L. The diaphragm plates 25 and 26 have circular or elliptical openings 25a and 26a, respectively, which face the lower and peripheral sides of the lens L when viewed from the deposition sources 21 and 22.

To form an optical thin film on the surface of the lens L using such a film forming apparatus 20, first the film forming chamber is evacuated to a vacuum, and then vapor deposition particles are diffused from each of the vapor deposition sources 21, 22. The vapor deposition particles diffused in this manner diffuse as indicated by arrows A1 to A4, but the vapor deposition particles diffused in the directions indicated by arrows A2 and A4 are blocked by the aperture plates 25, 26, and only the vapor deposition particles diffused in the directions indicated by arrows A1 and A3 pass through the openings 25 a, 26 a, reach and adhere to the surface of the lens L, and form an optical thin film (film forming process) .

In this example, the deposition particles diffused from the deposition source 21 in the direction of arrow A1 head vertically upward relative to the lower surface of the revolving lens L, and arrive at and adhere to the central portion of the lower surface of the lens L in a state of nearly normal incidence. On the other hand, the deposition particles diffused from the deposition source 22 in the direction of arrow A3 are incident on the revolving lens L at an oblique angle, and arrive at and adhere to the peripheral portion of the lens in a state of nearly normal incidence. Here, the deposition efficiency and deposition density of the deposition particles that are perpendicularly incident are highest, so that an optical thin film is formed at the central portion of the lower surface of the lens mainly by the deposition particles from the deposition source 21, and at the peripheral portion of the lower surface of the lens mainly by the deposition particles from the deposition source 22. Thus, efficient thin film formation is achieved in both portions, and the film thickness distribution is uniform.

Figure 3 shows a third embodiment of an optical thin film deposition apparatus according to the present invention. This apparatus 30 is obtained by adding a correction plate 31 to the deposition apparatus shown in Figure 2, and the same components as those shown in Figure 2 are designated by the same numbers and their description will be omitted. The correction plate 31 has a plurality of blades 32 that restrict incident particles near normal incidence, in consideration of the fact that deposition efficiency is highest when deposition particles from the deposition source are perpendicularly incident on the surface of the lens L and that the deposition efficiency decreases as the angle of incidence increases toward oblique incidence.

To form an optical thin film on the surface of the lens L using such a film formation apparatus 30, first the film formation chamber is evacuated to a vacuum, and then vapor deposition particles are diffused from each of the vapor deposition sources 21 and 22. The vapor deposition particles diffused in this manner diffuse as indicated by arrows A1 to A4, and the vapor deposition particles diffused in the directions indicated by arrows A2 and A4 are blocked by the aperture plates 25 and 26, while only the vapor deposition particles diffused in the directions indicated by arrows A1 and A3 pass through the openings 25 a and 26 a.

The deposition particles that have passed through the openings 25 a and 26 a in this way then pass through the corrector plate 31, and after the passing particles are partially restricted by the blades 32, they reach and adhere to the surface of the lens L, forming an optical thin film. The restriction of the passing particles by the blades 32 is greatest for the portion that is perpendicularly incident on the surface of the lens L and becomes smaller toward the oblique incidence side, thereby making the film thickness distribution of the optical thin film that is formed even more uniform.

As can be seen from the above explanation, the aperture plate prevents the obliquely incident component of the deposition particles diffused from each deposition source from entering, and uses only the normally incident component, which has good deposition efficiency, to achieve a uniform film thickness distribution. For this reason, multiple deposition sources are provided so that the central and peripheral portions of the lens (optical element) can be subjected to film formation processing (processes) using deposition particles from different deposition sources. On the other hand, the correction plate is used to limit the incidence of the normally incident component to some extent in order to eliminate the difference between the normally incident component and the obliquely incident component in the deposition of deposition particles from a specified deposition source. The aperture plate and the correction plate have the same purpose of achieving a uniform film thickness distribution, but their methods are significantly different.

In the above examples, two evaporation sources are used, but three or more may be arranged (in the installation process) . In this case, three or more diaphragm plates are also used. The arrangement positions of the evaporation sources can also be appropriately set according to the surface shape of the optical element. Furthermore, although an electron gun is used as a means for heating the evaporation material in the evaporation source, a resistance heating or induction heating method may also be used. Furthermore, gases such as oxygen and argon may be introduced into the deposition chamber during film formation.

[0023]
[Effects of the Invention]
As described above, according to the present invention, since a plurality of deposition sources are arranged in a film formation chamber, deposition particles are incident from a plurality of directions onto a revolving or rotating/revolving optical element to form a thin film, and it is possible to make the film thickness distribution uniform on the surface of even optical elements with large curvatures, such as lenses. In other words, since film formation is performed by deposition particles that are diffused and incident from a plurality of directions, it is possible to have deposition sources with an incidence angle close to normal incidence at almost all positions on the surface, even in the case of optical elements with large curvatures. Therefore, it is possible to form an optical thin film with a uniform film thickness distribution on the surface of an optical element with large curvatures.

It is preferable to arrange each of these multiple evaporation sources at different distances from the orbital axis of the element support part, which allows the evaporation particles to be incident on the optical element in different directions and at different angles of incidence, and to adhere to the surface of the optical element, thereby making the film thickness distribution more uniform.

For the same purpose, it is preferable to provide an aperture member between each of the multiple evaporation sources and the optical element supported by the element support member to limit the diffusion direction of the evaporation particles from each of the multiple evaporation sources. This aperture member can limit the angle of incidence of the evaporation particles reaching the optical element from each of the multiple evaporation sources, thereby controlling the thickness distribution of the thin film formed on the surface of the optical element. The thickness distribution can be further uniformed by, for example, limiting the angle of incidence in the direction of oblique incidence. Furthermore, if a correction plate is provided between the aperture member and the optical element supported by the element support member to adjust the uneven adhesion of the evaporation particles to the surface of the optical element, the thickness distribution can be further uniformed.

[Explanation of symbols]
10, 20, 30 Film forming apparatus 11, 12, 21, 22 Vapor deposition source 15, 16, 25, 26 Aperture plate 31 Correction plate

Claims (7)

An optical thin film deposition apparatus characterized by comprising: an element support section that supports an optical element and causes the optical element to revolve or rotate around its axis, and a plurality of deposition sources that generate deposition particles for forming a thin film on the surface of the optical element, arranged in a sealable deposition chamber. 2. The optical thin film deposition apparatus according to claim 1, wherein each of the plurality of evaporation sources is disposed at a different distance from the revolution axis of the element support. 3. The optical thin film deposition apparatus according to claim 1, wherein a throttle member is provided between each of the plurality of evaporation sources and the optical element supported on the element support portion to limit the diffusion direction of evaporation particles from the plurality of evaporation sources, thereby limiting the angle of incidence of the evaporation particles reaching the optical element from the plurality of evaporation sources. 4. The optical thin film deposition apparatus according to claim 3, further comprising a correction plate provided between the diaphragm member and the optical element supported by the element support portion. an installation step of supporting an optical element in a sealably formed film formation chamber, arranging a plurality of evaporation sources for forming a thin film on a surface of the optical element, and providing a diaphragm member between the optical element and the plurality of evaporation sources;
a film formation step of causing the supported optical element to perform an orbital motion or a rotational/revolutional motion, generating deposition particles from the plurality of deposition sources, and adjusting adhesion of the deposition particles to the surface of the optical element by the diaphragm plate, thereby forming a thin film on the surface of the optical element,
The optical thin film forming method, wherein the aperture member limits the angle of incidence of deposition particles reaching the optical element from the plurality of deposition sources. 6. The optical thin film deposition method according to claim 5, wherein the plurality of evaporation sources are arranged at different distances from the axis of revolution of the optical element. 7. An optical element having a surface on which a thin film is formed by the optical thin film forming method according to claim 5 or 6.