JP2011013562A - Optical element and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element which has an optically functional surface, the normal direction of which forms a high angle with the optical axis direction of the optical element, and on the optically functional surface of which a biased distribution of the reflectances of the lights entering from various directions is alleviated.SOLUTION: In the optical element 1, a plurality of projecting parts 3a constituting a minute structure 3, which is formed in a region of a highly inclined part 2 whose normal direction 5 forms the high angle with the optical axis direction of the optical element, are formed so that a formed direction 4 of the projecting part 3a forms an inclined angle 6 with the normal direction 5 of a curved surface 1a (the optically functional surface) in a formed position of the projecting part 3a. As a result, the biased distribution of the reflectances in the highly inclined part 2 and other regions on the curved surface 1a is alleviated so that an excellent antireflection effect can be obtained in the whole region of the curved surface 1a of the optical element 1.

Description

  The present invention relates to an optical element and a method for manufacturing the optical element.

  For example, in an optical system configured using optical elements, the reflection of incident light on the optical function surface of each optical element is caused by a loss of incident light quantity or a decrease in optical performance due to unexpected scattering of reflected light. It becomes a factor and is not preferable.

Therefore, conventionally, an antireflection coating has been applied to the surface of an optical element such as a lens.
In recent years, instead of antireflection coatings, it is possible to suppress light reflection over a wide wavelength band and a wide range of incident angles, and it is possible to suppress light reflection over a wide wavelength band and a wide range of incident angles. Various materials for optical elements A surface non-reflective structure having various advantages such as being applicable to the above and being capable of being integrated with an optical element has been proposed.

This surface non-reflective structure, that is, the antireflection structure is realized by forming fine irregularities having a wavelength equal to or less than the wavelength of incident light on the optical function surface of the optical element.
For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2005-316393), Patent Document 2 (Japanese Patent Laid-Open No. 2006-171219) and Patent Document 3 (Japanese Patent Laid-Open No. 2006-053220), an optical element is used as an antireflection structure. A technique for forming a concave or convex shape with a fine structure in the normal direction of the curved surface is disclosed, and it is said that an antireflection effect can be obtained even when the incident angle of the light beam is increased with respect to the optical axis direction.

However, the following technical problems remain in the above-described conventional technology.
That is, in any of Patent Document 1, Patent Document 2, and Patent Document 3, since a concave or convex shape with a fine structure is simply formed in the normal direction of the curved surface of the optical element, light is emitted from the optical axis direction. Even when the light is incident, there is a concern that the reflectance distribution in the optical functional surface of the optical element is biased, and the antireflection effect at a specific portion in the optical functional surface is lowered.

  In particular, in an optical element having an optical functional surface whose normal direction forms a large angle with the optical axis direction, there is a greater concern that the distribution of reflectance in the optical functional surface is biased.

JP 2005-316393 A JP 2006-171219 A JP 2006-053220 A

  An object of the present invention is to provide a technique capable of reducing the uneven distribution of reflectance on an optical function surface in an optical element having an optical function surface whose normal direction forms a large angle with the optical axis direction. It is in.

A first aspect of the present invention is an optical element having an optical functional surface on which a plurality of concave or convex microstructures are formed with a period shorter than the wavelength of visible light,
Provided is an optical element in which at least a part of the microstructure is formed to be inclined with respect to a normal direction of the optical function surface.

A second aspect of the present invention is a method for manufacturing an optical element having an optical functional surface on which a plurality of concave or convex fine structures are formed with a period shorter than the wavelength of visible light,
Provided is a method for manufacturing an optical element, wherein at least a part of the microstructure is formed to be inclined with respect to a normal direction of the optical function surface.

  According to the present invention, in an optical element having an optical function surface whose normal direction forms a large angle with the optical axis direction, a technique capable of reducing the uneven distribution of reflectance on the optical function surface is provided. Can do.

It is a perspective view which shows the structural example of the optical element manufactured by the manufacturing method of the optical element which is one embodiment of this invention. It is sectional drawing along the optical axis of the optical element which is one embodiment of this invention. It is sectional drawing to which the A section cross section of the high inclination part illustrated by FIG. 1 was expanded. It is sectional drawing which expanded the A section cross section of FIG. 1 in the optical element which is other embodiment of this invention.

  In the first aspect of the present embodiment, the normal direction of the curved surface (optical functional surface) in which a plurality of concave or convex microstructures having a period shorter than the wavelength of visible light is formed is 30 with respect to the optical axis. In an optical element having a portion (high inclination portion) having an angle of more than 0 °, an optical element in which the fine structure is inclined with respect to the normal direction of the curved surface is provided in the high inclination portion.

  In the optical element according to the first aspect, when the fine structure is formed in the highly inclined portion in which the normal direction of the curved surface forms an angle of 30 ° or more with respect to the optical axis of the optical element, the formation direction is set to the optical element. It is formed so as to be inclined with respect to the normal direction without matching the normal direction of the curved surface.

  As described above, the fine structure is formed so as to be inclined with respect to the normal direction of the curved surface of the optical element in the high inclined portion in which the normal direction of the curved surface forms an angle of 30 ° or more with respect to the optical axis of the optical element. Thus, an optical element capable of uniformly reducing the reflectance within the optical element surface with respect to incident light is obtained.

This is particularly effective in an optical element such as a hemispherical shape in which the normal direction of the curved surface at the outer peripheral portion forms a large angle with the optical axis.
According to a second aspect, there is provided the optical element according to the first aspect, wherein an inclination angle with respect to a normal direction of the fine structure is ± 5 ° or more.

  In the optical element according to the second aspect, when the fine structure is formed in the highly inclined portion where the normal direction of the curved surface forms an angle of 30 ° or more with respect to the optical axis of the optical element, the forming direction is set to the curved surface of the optical element. It is formed so as to be inclined by 5 ° or more with respect to the normal direction.

  In this way, by forming the fine structure at an angle of 5 ° or more with respect to the normal direction of the optical element in the high inclination portion where the normal direction of the curved surface forms a large angle with respect to the optical axis of the optical element, It becomes possible to reduce the reflectance in the optical element plane more uniformly.

  According to a third aspect, there is provided the optical element according to the first aspect to the second aspect, wherein an inclination angle and an inclination direction with respect to a normal direction of the plurality of fine structures are randomly formed.

  In the optical element according to the third aspect, a plurality of fine structures are formed when the fine structures are formed in the high inclined portion in which the normal direction of the curved surface forms an angle of 30 ° or more with respect to the optical axis of the optical element. Each is formed such that at least one of the tilt angle and the tilt direction is random with respect to the normal direction of the curved surface of the optical element.

  In this way, in the highly inclined portion where the normal direction of the curved surface forms a large angle with respect to the optical axis of the optical element, each of the plurality of fine structures is inclined with respect to the normal direction of the optical element curved surface. By forming at least one of them randomly, an optical element capable of reducing the reflectance in the optical element plane even more uniformly regardless of the direction of incident light with respect to the optical axis is obtained.

In a 4th aspect, the optical system provided with the optical element as described in a 1st aspect-a 3rd aspect is provided.
In the optical system according to the fourth aspect, when the fine structure is formed in the highly inclined portion in which the normal direction of the curved surface forms an angle of 30 ° or more with respect to the optical axis of the optical element, the formation direction is set to the optical element. The optical element formed so as not to coincide with the normal direction of the curved surface is inclined with respect to the normal direction.

  In this way, the fine structure is formed to be inclined with respect to the normal direction of the curved surface of the optical element in the high inclined portion where the normal direction of the curved surface forms an angle of 30 ° or more with respect to the optical axis of the optical element. Thus, even when an optical element having a portion in which the normal direction of the curved surface forms a large angle with respect to the optical axis of the optical element, the reflectance within the curved surface of the optical element is uniformly reduced with respect to the incidence of light. It is possible to manufacture an optical system that can be used.

  According to the optical elements according to the first to third aspects described above, the microstructure is formed on the curved surface of the optical element in the highly inclined portion where the normal direction of the curved surface forms an angle of 30 ° or more with respect to the optical axis of the optical element. Even if an optical element having a portion in which the normal direction of the curved surface forms a large angle with respect to the optical axis of the optical element is used, it is optical with respect to the incidence of light. The reflectance within the curved surface of the element can be reduced uniformly, and an optical element with uniform reflectance within the curved surface of the optical element can be produced without forming an antireflection film.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Embodiment 1]
Embodiment 1 of the present invention will be described with reference to FIG. 1, FIG. 2, and FIG.

(Constitution)
FIG. 1 is a perspective view showing a configuration example of an optical element manufactured by a method for manufacturing an optical element according to an embodiment of the present invention.

  As illustrated in FIG. 1, the optical element 1 of the present embodiment has a flat surface 1b as an optical functional surface at one end on the optical axis 7, and a convex curved surface 1a as an optical functional surface on the opposite side. A plano-convex lens.

  As an example, the curvature radius R of the curved surface 1a of this optical element 1 is 10 mm, and the lens diameter D is 15 mm. Has been. Note that the microstructure 3 may be provided on the flat surface 1b side as necessary.

  The range in which the angle formed by the normal direction 5 of the curved surface 1a with respect to the optical axis 7 of the optical element 1 of the present embodiment is 30 ° or more is the high slope portion 2 in FIG. That is, in the case of the optical element 1 having the specifications of the present embodiment, the highly inclined portion 2 is located on the curved surface 1a from a position where the diameter b is 10 mm to a position where the diameter a is 15 mm (in this case, equal to the lens diameter D). This is the area in the range up to (position).

FIG. 2 is a cross-sectional view along the optical axis 7 of the optical element 1 of the present embodiment.
In FIG. 2, the angle β indicates the angle between the normal direction 5 of the curved surface 1 a of the portion with the diameter b and the optical axis 7, and the angle α indicates the normal direction 5 of the curved surface 1 a with the portion of the diameter a and the optical axis 7. Indicates the angle.

  In the optical element 1 of the present embodiment, as an example, the angle β is 30 ° and the angle α is 41 °, and the range from the angle α to the angle β is a normal line of the curved surface 1 a with respect to the optical axis 7. The range in which the incident angle of light in the direction 5 is 30 ° or more, that is, the high slope portion 2.

FIG. 3 is an enlarged cross-sectional view of a section A of the high slope portion 2 illustrated in FIG.
The microstructure 3 of the optical element 1 according to the present embodiment is composed of a plurality of convex portions 3a formed with a period equal to or less than the wavelength of visible light to be antireflection, and in the region of the high slope portion 2, the microstructure The convex portion forming direction 4 of each convex portion 3a that constitutes 3 is tilted without being coincident with the normal direction 5 of the optical element curved surface.

  In addition, the convex part formation direction 4 is a convex part central axis of each convex part 3a. And as an example, the inclination angle 6 of each convex part formation direction 4 of the high inclination part 2 and the normal direction 5 of the curved surface 1a of the optical element 1 is 5 degrees or more, and the inclination direction is the direction of the surface apex 8. (Top direction).

  In addition, in FIG. 3, although the case where each convex part 3a which comprises the fine structure 3 is formed with the same period along the outline of the curved surface 1a is illustrated, the said wavelength by which the antireflection effect is maintained. Within the range, the formation period of the convex portions 3a may be random.

  Further, although not particularly illustrated, each convex portion forming direction 4 formed on the curved surface 1 a other than the high inclined portion 2 is formed with an inclination of 5 ° or less with respect to the normal direction 5 of the curved surface 1 a of the optical element 1. ing.

(Function)
According to the optical element 1 according to the present embodiment, the fine structure 3 is configured in the high inclined portion 2 in which the normal direction 5 of the curved surface 1a forms an angle of 30 ° or more with respect to the optical axis 7 of the optical element 1. Since the plurality of convex portions 3a are formed to be inclined with respect to the normal direction 5 of the curved surface 1a of the optical element 1, the antireflection effect in the curved surface 1a of the optical element 1 is made uniform over the entire curved surface 1a. be able to.

(effect)
Thereby, even in the optical element 1 having the curved surface 1a having a small curvature radius, it is possible to obtain a good and uniform antireflection effect from the entire curved surface 1a of the high inclined portion 2. Moreover, since the convex part 3a of the fine structure 3 is formed also on the curved surface 1a other than the high inclination part 2, the reflection of the light which injects into the whole surface of the curved surface 1a of the optical element 1 can be suppressed uniformly.

  In the optical system, the optical element 1 of the first embodiment is arranged particularly on the incident side, such as the first surface on the incident side, so that the reflectance distribution is less biased in the curved surface 1a of the optical element 1. Since an antireflection effect can be obtained, an optical system having a good antireflection performance can be obtained.

[Embodiment 2]
A second embodiment of the present invention will be described with reference to FIG. 1 and FIG.
(Constitution)
The radius of curvature R and the lens diameter D of the optical element 21 of the second embodiment have the same specifications as those of the first embodiment, and the high slope portion 2 is also formed in the same range of the curved surface 1a.

FIG. 4 is an enlarged cross-sectional view of a portion A of the high slope portion 2 of FIG. 1 in the optical element 21 of the second embodiment.
As illustrated in FIG. 4, in the case of the optical element 21 of the present embodiment, the inclination of each convex portion 23 a constituting the microstructure 23 within the range of the high inclined portion 2 with respect to the normal direction 25 of the optical element. The angle 26 and the convex forming direction 24 are randomly different within a range in which the antireflection effect is maintained.

The inclination angle 26 of the convex portion 23 a in the high inclination portion 2 is 5 ° or more with respect to the normal direction 25 of the curved surface 1 a of the optical element 21.
Note that the convex formation direction 24 may be any of the direction toward the surface apex 8 (surface apex direction), the direction toward the flat surface 1b (plane direction), and the circumferential direction around the optical axis 7. The direction may be a combination of directions.

  In addition, each convex part 23a formed in the area | regions other than the high inclination part 2 in the curved surface 1a is formed in the inclination within 5 degrees with respect to the normal line direction 25 of the curved surface 1a of the optical element 21, for example.

(Function)
According to the optical element 21 according to the second embodiment, the fine structure 23 is formed in the highly inclined portion 2 where the normal direction 25 of the curved surface 1a forms an angle of 30 ° or more with respect to the optical axis 7 of the optical element 21. Since each convex part 23a which comprises is formed inclining with respect to the normal line direction 25 of the curved surface 1a of the optical element 21, the antireflection effect in the curved surface 1a of the optical element 21 can be made uniform at a high level. it can.

(effect)
As a result, for example, even in the optical element 21 having the curved surface 1a having a small radius of curvature R, the entire antireflection effect of the curved surface 1a of the high inclined portion 2 can be obtained uniformly at a high level.

In addition, since the fine structure 23 is formed on the curved surface 1a other than the high-inclined portion 2, light reflection on the entire surface of the curved surface 1a of the optical element 21 can be suppressed uniformly.
In the optical system, the optical element 21 according to the second embodiment is arranged particularly on the light incident side such as the first surface on the incident side, whereby the reflectance distribution is less uneven in the curved surface 1a of the optical element 21. Since the antireflection effect can be obtained, an optical system having a good antireflection ability can be obtained.

In the first and second embodiments, the fine structure has a convex shape, but the fine structure may have a concave shape.
Further, the convex shape and the concave shape can be made into a cone shape such as a cone or a bell shape as long as the antireflection effect is maintained.

Furthermore, although the central axis of the convex portion is a straight line, it may not be a straight line such as curved.
In FIG. 3 described above, the inclination angle 6 and the inclination direction (convex portion forming direction 4) of each convex portion 3a are the same, and the inclination direction (convex portion forming direction 4) is the direction (surface) toward the surface apex 8. However, as shown in FIG. 4, the inclination angle 26 of each convex portion 23a with respect to the normal direction 25 of the curved surface 1a and the convex formation direction 24 are different within the range in which the antireflection effect is maintained. May be. Regarding the forming direction of the convex portion 3a and the convex portion 23a, any direction of the direction toward the surface top 8 (surface top direction), the direction toward the flat surface 1b (plane direction), and the circumferential direction around the optical axis 7 may be used. A direction in which each direction is combined may be used.

Here, an example of the manufacturing method of the optical element of each embodiment described above will be described.
Since both the optical element 1 and the optical element 21 described above are substantially the same, the optical element 1 will be described as an example.

An example of a method for forming the fine structure 3 in the optical element 1 of the present embodiment having an antireflection function will be described.
In the optical element 1 of the present embodiment, the microstructure 3 may be formed on the curved surface 1a using any method.

As a method for forming the fine structure 3, for example, the following method can be used.
For example, it is possible to use a method of forming the microstructure 3 on the curved surface 1a of the optical element 1 at the same time that the optical element 1 is molded using a mold having a shape opposite to that of the microstructure 3 to be formed. .

  In addition, after forming the curable material on the curved surface 1a of the optical element 1, the concavo-convex shape is transferred to the curable material using a mold having the concavo-convex shape opposite to the microstructure 3 to be formed, and curable. A method of curing the material can be used.

Moreover, the method of drawing the uneven | corrugated shape of the fine structure 3 by irradiating an electron beam directly to the curved surface 1a of the optical element 1 can be used.
Any of these methods may be used.

Note that any method may be used as a method of manufacturing a mold having an uneven shape opposite to the microstructure 3 to be formed.
For example, a method of producing a prototype by forming a fine structure having an uneven shape opposite to the fine structure 3 to be formed on a mold base using a lithography technique such as electron beam drawing or ion etching of a semiconductor process. Can be used.

Moreover, after forming the microstructure 3 to be formed on the mold base, a method of producing an inverted mold by electroforming using a metal such as Ni can be used.
Needless to say, the present invention is not limited to the configuration exemplified in the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, the shape of the high inclination portion 2 in the optical element 1 or the optical element 21 may be a conical surface or a plane inclined with respect to the optical axis 7.

DESCRIPTION OF SYMBOLS 1 Optical element 1a Curved surface 1b Flat surface 2 Highly inclined part 3 Fine structure 3a Convex part 4 Convex part forming direction 5 Normal direction 6 of the curved surface 1a Inclination angle 7 Optical axis 8 Surface top 21 Optical element 23 Fine structure 23a Convex part 24 Convex part forming direction 25 Normal direction of curved surface 1a 26 Inclination angle

Claims (8)

An optical element having an optical functional surface on which a plurality of concave or convex fine structures are formed with a period shorter than the wavelength of visible light,
At least a part of the fine structure is formed to be inclined with respect to a normal direction of the optical function surface. The optical element according to claim 1, wherein
The optical element has a high slope portion in which the normal direction of the optical function surface forms an angle of 30 ° or more with respect to the optical axis of the optical element,
In the high inclination portion, the fine structure is formed to be inclined with respect to a normal direction of the optical function surface. The optical element according to claim 1 or 2,
An optical element, wherein an inclination angle of the fine structure with respect to the normal direction is ± 5 ° or more. The optical element according to any one of claims 1 to 3,
An optical element, wherein at least one of an inclination angle and an inclination direction with respect to the normal direction of the plurality of fine structures is randomly formed. A method of manufacturing an optical element having an optical functional surface on which a plurality of concave or convex microstructures are formed with a period shorter than the wavelength of visible light,
At least a part of the fine structure is formed to be inclined with respect to a normal direction of the optical function surface. In the manufacturing method of the optical element according to claim 5,
The optical element has a high slope portion in which the normal direction of the optical function surface forms an angle of 30 ° or more with respect to the optical axis of the optical element,
In the high inclined portion, the microstructure is formed to be inclined with respect to the normal direction of the optical function surface. In the manufacturing method of the optical element of Claim 5 or Claim 6,
The method of manufacturing an optical element, wherein an inclination angle of the fine structure with respect to the normal direction is ± 5 ° or more. In the manufacturing method of the optical element of any one of Claims 5-7,
A manufacturing method of an optical element, wherein at least one of an inclination angle and an inclination direction with respect to the normal direction of the plurality of fine structures is randomly formed.

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