JP2003329806A - Optical appliance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical system having an antireflection element using a fine structure (SWS) smaller than wavelengths, which is constituted so that cleaning is easily performed when dirt or the like deposits and it is hardly scratched by external force. <P>SOLUTION: In the optical system having a plurality of antireflection elements using a fine structure (SWS) smaller than wavelengths, an antireflection film comprising dielectric thin films is vapor deposited on the exterior part of the system without arranging a SWS. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silver salt camera and a reflection optical device used in photographic optical equipment such as a digital camera using a CCD or the like as an image pickup device, a video camera, a finder, binoculars, a telescope, a microscope and the like. It relates to the prevention function.

[0002]

2. Description of the Related Art Conventionally, in an optical system having a plurality of lenses, an antireflection film is used in order to prevent a decrease in light amount, flare and ghost due to reflection on each surface. This is a vapor deposition of a single-layer or multi-layer dielectric thin film.

On the other hand, instead of the vapor-deposited film, "moth eye" is used.
It is known that a fine structure (SWS) having a wavelength equal to or less than "e" has an antireflection function, and an antireflection element using the same is proposed.

As an example used in an actual optical system, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Publication No. 000-258607, a method of manufacturing an antireflection element using a sub-wavelength fine structure (SWS) on the surface of BOE has been proposed. Unlike ordinary spherical and aspherical systems, BOE has a stepped shape consisting of several flat layers with a step on the order of wavelength, and it is difficult to form an antireflection thin film by vapor deposition, so that the flat surface has a SWS shape. An antireflection structure is used, and a manufacturing method for the structure is proposed. The antireflection element using SWS is characterized in that the incident angle characteristic of the antireflection effect is good and the wavelength characteristic is excellent as compared with the antireflection of a thin film.

[0005]

[Problems to be Solved by the Invention] However, SWS
Since the antireflection structure has fine irregularities on its surface, it is difficult to clean it when dirt or the like is attached.

For example, a normal fiber is at most 10 μm
Even a high-grade cleaning cloth for wiping glasses has a thickness of 1, 2 μm. On the other hand, the structure of the antireflection element of the SWS is on the order of about 200 nm, and even if it is wiped off, the fiber cannot even enter the groove.

Further, a chemical immersion cleaning method such as ultrasonic cleaning is effective for single lens parts and the like, but is not possible for a product form of optical equipment having a plurality of optical surfaces.

Further, since the uneven shape has a height of about the wavelength and an interval of about half the wavelength, the aspect ratio is high and the mechanical strength against external pressure is weak, so that it is not suitable as an exterior part.

[0009]

According to the present invention, an antireflection SWS is arranged on at least a first surface on the object side in an optical system having a plurality of surfaces having an antireflection function by a fine structure (SWS) of a wavelength or less. The above-mentioned problems are overcome by a configuration that does not.

Further, in the present invention, in the eyepiece optical system having the antireflection function by the fine structure (SWS) of the wavelength or less on the plurality of surfaces, the antireflection SWS is not arranged at least on the surface closest to the eye point. There is.

Further, in an interchangeable lens having a plurality of surfaces with an antireflection function by a fine structure (SWS) of a wavelength or less, at least the lens surface closest to the image side has the antireflection SWS.
Is not placed.

Further, in an optical system having a plurality of surfaces with an antireflection function by a fine structure (SWS) of a wavelength or less,
The antireflection SWS is not arranged except for the molded lens.

Further, in the above structure, at least one antireflection SWS is provided for the surface having the maximum incident angle of 30 ° or more, so that the ghost is more effectively generated due to the angular characteristic of the antireflection film. Can be suppressed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the S of the first embodiment of the present invention.
The WS antireflection element was used with a focal length of 50 mm FNo. It is an optical sectional view when it is used for a single focus lens of about 1.8. In FIG. 1, the first lens 1-1 is provided with an antireflection coating by a multilayer film, and the lens surfaces 1-2 to 1-6 are provided with an antireflection element by SWS. In a so-called Gauss type lens system, the difference in the angle of incidence of light rays on each surface is large, and therefore the antireflection film made of a dielectric thin film is easily affected by angular characteristics, and the ghost cannot be completely removed. In Example 1, the SW is formed on the second to sixth lens surfaces.
By arranging the antireflection element by S, good antireflection performance can be obtained regardless of the incident angle.
It is possible to prevent the generation of ghosts due to surface reflection. Further, by disposing an antireflection film made of a multilayer film on the first lens surface, it is possible to easily clean even if dirt is attached.

FIG. 2 is an optical sectional view when the SWS antireflection element of the second embodiment of the present invention is used in a viewfinder of a single-lens reflex camera. In FIG. 2, 2-1 is an imaging lens, 2-2 is a quick return mirror, 2-3 is a focusing plate (Fresnel lens), 2-4 is a focusing plate (matte surface), 2-5 is a pentaprism, 2 -6 is an eyepiece lens. An antireflection film made of a multilayer film was vapor-deposited on the lens surface of the eyepiece lens 2-6 closest to the eye point, and the other surface of the eyepiece lens was used as a SWS antireflection element.

FIG. 3 is a lens sectional view of binoculars in which the SWS antireflection according to the third embodiment of the present invention is arranged. From the left side of the paper, the configuration includes a 3-1 objective lens, a 3-2 vibration-proof variable apex prism, a 3-3 erecting prism, and a 3-4 eyepiece lens. The objective lens, the variable apex prism for image stabilization, and the erecting prism are coated with an antireflection film by vapor deposition of a dielectric thin film.
The WS antireflection element is arranged. An antireflection film, which is a dielectric thin film, is deposited on the lens closest to the eyepoint of the eyepiece. It is possible to easily remove stains from the outside, both on the objective side and the eyepoint side.

In binoculars, the angle change of the incident light on the objective lens, the variable apex prism and the erecting prism is relatively small. Therefore, even if the conventional dielectric thin film is used, the antireflection effect is large. On the other hand, in the eyepiece, since the radius of the surface is relatively small, it is likely that a ghost will occur due to the combination of the surfaces, and it is difficult to predict. The incident angle of light rays reflected by unnecessary light on the surface varies, and the antireflection thin film cannot obtain a sufficient ghost prevention effect because of its high angle dependency. Therefore, the antireflection element by SWS is arranged and the ghost is satisfactorily removed.

FIG. 4 is a sectional view of the taking lens system of the compact camera in which the SWS antireflection element of the fourth embodiment of the present invention is arranged. A glass mold is used for the fifth lens counted from the object side, and a SWS antireflection element is arranged there. This is to form the SWS structure at the same time as molding the molded lens. The other lenses are formed by spherical polishing and have an antireflection film formed of a multilayer film deposited thereon.

FIG. 5 is a sectional view of an interchangeable lens for a single-lens reflex camera in which the SWS antireflection element of the fifth embodiment of the present invention is arranged. This is a telephoto lens interchangeable lens with a focal length of 200 mm and an Fno of 1.8. SWS antireflection elements are arranged on all spherical surfaces. The most object-side surface of the taking lens is a protective lens, and a multilayer antireflection film is vapor-deposited. The surface closest to the image is a drop-in filter, which is a multi-layer antireflection film or various filters. SW for these two sides
By not disposing the antireflection element of S, cleaning can be easily performed against the adhesion of dirt. Then, it becomes possible to prevent the SWS antireflection element from being deformed by the pressure from the outside.

FIG. 6 shows a cylindrical SWS used in the present invention.
It is a schematic diagram of an antireflection element. Innumerable cylindrical projections 6-2 are arranged at substantially equal intervals on the base medium 6-1. a is the distance between each cylinder and 1 / wavelength
A size of about 2 is desirable. In addition, b indicates the thickness of the cylinder, which determines the filling rate of the fine elements. This value is preferably about 50% to 80% of a. c indicates the height of the cylinder, which is said to be preferably several times the wavelength.

By optimizing these three variables, it is possible to increase the antireflection efficiency for a desired wavelength.

FIG. 7 shows a conical SWS used in the present invention.
It is a schematic diagram of an antireflection element. The conical protrusions 7-2 are arranged innumerably at substantially equal intervals on the base medium 7-1. a is the distance between each cone and 1 / wavelength
A size of about 2 is desirable. In addition, b indicates the size of the bottom surface of the cone, which determines the filling rate of the fine elements. This value is preferably about 50 to 100% of a. c indicates the height of the cylinder, which is preferably several times the wavelength.

By optimizing these three variables, it is possible to improve the antireflection efficiency for a desired wavelength. By using either or both of these two types as the SWS antireflection element of the above optical system, ghosts and the like can be satisfactorily removed, and at the time of attachment of dirt and the like,
It is possible to easily perform maintenance such as cleaning, and it is possible to provide an optical system that is unlikely to be scratched by external force. The SWS antireflection element is not limited to the above two types and can be applied.

[0024]

According to the present invention, as described above, the SWS
Regarding an optical system using multiple antireflection elements, it is possible to prevent dirt from adhering to the element surface and prevent mechanical damage to the element surface.
There is an effect that an antireflection effect is maintained with a relatively simple structure, and an optical device in which the angle dependence of an incident light beam is good can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a taking lens having an antireflection element arrangement according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a single-lens reflex finder having an antireflection element arrangement according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a binocular lens with an antireflection element arrangement according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a compact camera taking lens having an antireflection element arrangement according to a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a telephoto lens with an antireflection element arrangement according to a fifth embodiment of the present invention.

FIG. 6 is a schematic view of a cylindrical SWS antireflection element arranged in the present invention.

FIG. 7 is a schematic diagram of a conical SWS antireflection element arranged in the present invention.

[Explanation of symbols]

1-1: First lens, 1-2: Second lens, 1-
3: 3rd lens, 1-4: 4th lens, 1-5: 5th
Lens, 1-6: sixth lens, 2-1: imaging lens,
2-2: Quick Return Mirror, 2-3: Focus Plate (Fresnel), 2-4: Focus Plate (Mat Surface), 2-
5: Penta prism, 2-6: Eyepiece lens 3-1: Objective lens, 3-2: Variable apex angle prism, 3-
3: Erect prism, 3-4: Eyepiece lens, 6-1: Base medium 6-2: Cylindrical protrusion 7-1: Base medium 7-2: Conical protrusion

Claims (9)

[Claims] 1. An optical system having an antireflection function of a sub-wavelength fine structure (SWS) on a plurality of surfaces, wherein the antireflection SWS is not arranged at least on the first surface on the object side. . 2. The optical device according to claim 1, wherein an antireflection thin film is provided on the first surface on the object side. 3. An eyepiece optical system having a plurality of surfaces having an antireflection function by a fine structure (SWS) of a wavelength or less, wherein at least the eyepoint side surface is not provided with the antireflection SWS. machine. 4. The optical device according to claim 3, wherein an antireflection thin film is provided on the surface closest to the eyepoint. 5. An interchangeable lens having a plurality of surfaces with an antireflection function by a sub-wavelength fine structure (SWS), wherein the antireflection SWS is not arranged at least on the lens surface closest to the image side. machine. 6. The optical apparatus according to claim 5, wherein an antireflection thin film is provided on the lens surface closest to the image side. 7. An optical device having an antireflection function by a fine structure (SWS) of a wavelength or less on a plurality of surfaces, wherein an antireflection SWS is not arranged other than a mold lens. 8. The optical device according to claim 7, wherein at least one of the surfaces on which the antireflection SWS is not arranged is provided with an antireflection film. 9. A surface having a maximum incident angle of 30 ° or more,
9. The optical device according to claim 1, wherein at least one surface of the antireflection SWS is provided.