JP2002048906A - Diffraction optical device and optical system having the same, photographing device and observation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diffraction optical device to decrease the quantity of flare which degrades the optical performance, and to provide an optical system, a photographing device and an observation device having the above diffraction optical device. SOLUTION: A light-shielding means is formed which shields the light entering the edge part of a diffraction grating or the light exiting from the edge part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffractive optical element, an optical system having the diffractive optical element, a photographing device, and an observation device.

[0002]

2. Description of the Related Art As a diffractive optical element, for example, a diffractive optical element (diffractive lens) configured to have a lens function.
Is known to have features not found in conventional refractive lenses, as described below. Since an aspherical wave can be easily generated, aberration can be effectively corrected. Since it has virtually no thickness, the degree of freedom of design is high,
A compact optical system can be realized. Since the amount corresponding to the Abbe number in the refractive lens is a negative value in the diffractive lens, chromatic aberration can be effectively corrected by a combination with the refractive element.

[0003] With respect to improving the performance of an optical system by utilizing the features of such a diffractive lens, for example, Bi
nary Optics Technology; T
heTheory and Design of Mu
lti-Level Diffractive Opt
ical element, Gary J. et al. Swan
son, Technical Report 85
4, MIT Lincoln Laboratory,
August 1989. Is described in detail.

As described above, the diffractive optical element has many useful features not found in the conventional refraction element. On the other hand, since the diffraction efficiency depends on the wavelength, the following principle is required. There's a problem. For example, a diffractive optical element applied to an optical system is often used as a lens element, but in such an application, it is generally not preferable that a plurality of diffracted lights (a plurality of focal points) exist. Therefore, in a conventional diffractive optical element (specifically, a diffractive lens), a relief pattern having a sawtooth-shaped (blazed) cross section is generally formed on a transparent base material at a wavelength to be used, and a specific order is obtained. The energy is concentrated on the diffracted light.

When the cross section is processed into a sawtooth waveform as described above, the wavelength at which energy can be concentrated depending on the depth of the groove, ie, the wavelength at which the diffraction efficiency is maximized, is different. It becomes impossible to concentrate energy in a specific order of diffracted light over the entire wavelength band. Such a phenomenon, for example, like laser light,
This is not a problem for optical systems that use monochromatic light,
In an optical system that utilizes white light, such as a camera, there is a problem that if the diffraction efficiency is optimized with light of a specific wavelength, the diffraction efficiency will decrease at other wavelengths.

For this reason, the mechanism of the wavelength dependence of the diffraction efficiency as described above is examined in detail, and a new type of relief type diffractive optical element with reduced wavelength dependence of the diffraction efficiency is disclosed in Japanese Patent Application Laid-Open No. Hei 9-127321. Kaihei 9-127322
JP, JP-A-9-325203, JP-A-11-
044808, JP-A-11-044810, JP-A-11-066461, JP-A-11-0
No. 84118, JP-A-11-223717,
And so on. These diffractive optical elements are obtained by combining two or more types of optical materials having different dispersions or refractive indexes, and forming a relief pattern forming a blazed diffraction grating on the boundary surface between the different optical materials.

[0007]

However, in a diffractive optical element having a blazed diffraction grating whose cross section is processed into a saw-tooth waveform, there is a problem in processing and restrictions on the arrangement of the optical system. There is a problem that there is a light beam that does not enter in parallel, and this light beam passes through the edge portion and becomes flare light, reaches the image plane, and deteriorates the optical performance of the element and the optical system. That is, when light is incident parallel to the edge portion 41 as shown in FIG. 4, the optical performance is not deteriorated. However, as shown in FIG. In the case where the edge portion 41 does not stand vertically or the incident light is obliquely incident on the blazed diffraction grating as shown in FIG.
1 and the incident light have a certain angle, and the edge portion 4
The amount of light passing through 1 increases, which becomes flare light and deteriorates optical performance.

Therefore, the present invention provides a diffractive optical element capable of reducing the amount of flare light that deteriorates optical performance.
It is another object of the present invention to provide an optical system, a photographing device, and an observation device having the diffractive optical element.

[0009]

In order to achieve the above object, the present invention provides a diffractive optical element having the following constitutions (1) to (9), an optical system having the diffractive optical element, and a photographing apparatus. , An observation device. (1) A diffractive optical element having a light blocking means for blocking light incident on an edge of a diffraction grating or light emitted from the edge. (2) The diffractive optical element according to (1), wherein the light shielding means is provided on a light incident side of the diffraction grating, and shields light incident on the diffraction grating. (3) The diffractive optical element according to (1), wherein the light shielding unit is provided on a light exit side of the diffraction grating, and shields light emitted from the diffraction grating. (4) The diffractive optical element according to any one of (1) to (3), wherein the light shielding portion has a diffractive action. (5) The diffractive optical element according to any one of (1) to (4), wherein the light-shielding unit has a plurality of light-shielding portions arranged at substantially the same pitch as the grating pitch of the diffraction grating. (6) The diffractive optical element according to any one of (1) to (5), wherein the diffraction grating is formed by stacking a plurality of diffraction gratings made of at least two kinds of materials having different dispersions. (7) An optical system comprising the diffractive optical element according to any one of (1) to (6). (8) An imaging device comprising the optical system according to (7). (9) An observation apparatus comprising the optical system according to (7).

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention,
By applying the above configuration, for example, in a blazed diffractive optical element whose cross section is processed into a sawtooth waveform, parallel to the edge of the relief pattern forming the blazed diffraction grating due to processing problems and restrictions on the arrangement of the optical system. Even when light does not enter the diffractive optical element, it is possible to realize a diffractive optical element in which light directed to the edge portion does not become flare light and optical performance deteriorates to a degree that cannot be ignored.

[0011]

Embodiments of the present invention will be described below. [Embodiment 1] FIG. 1 is a sectional view showing the structure of Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes a glass member serving as a base of the diffractive optical element, 2 denotes a synthetic resin member forming a blazed diffraction grating, 3 denotes a relief pattern surface (diffraction surface) of the diffraction grating 2, and 4 denotes an edge portion of the diffraction grating. 5 is the incident light,
Reference numeral 6 denotes an emission light, and reference numeral 7 denotes a light shielding unit. The light-shielding portion 7 is formed of a light-absorbing material such as chromium plating or a light-reflecting material such as chromium plating on the glass member 1 of the base (substrate) by photolithography or the like. (Pitch), and functions as a diffraction element by itself. Further, the light shielding portion may be formed by a method such as printing or vapor deposition. The width of the light-shielding portion was a width obtained by projecting light incident on the edge onto the glass member 1 as it was. The relief pattern may be formed by injection molding using a mold or replica molding.

As shown in FIG. 1, the incident light 5 is emitted from the relief surface 3 at a desired angle, but the light transmitted through the edge portion 4 is blocked by the light shielding portion 7 and does not reach the image forming surface. Deterioration can be prevented.

Embodiment 2 FIG. 2 is a cross-sectional view showing a structure according to Embodiment 2 of the present invention. Since the light shielding portion 7 is arranged on the incident light side from the relief surface and shields the light before the light is diffused at the edge portion, the light can be more effectively shielded.

Third Embodiment FIG. 3 is a sectional view showing the structure of a third embodiment of the present invention. In the laminated relief type diffractive optical element using two different synthetic resin materials, the light shielding portion 7 is arranged on the incident light side from the relief surface, and the light is shielded before the light is diffused at the edge portion. It is possible to do.

[Embodiment 4] In Embodiments 1 to 3, the plurality of light shielding portions 7 serving as light shielding means are formed of a base (diffraction grating substrate).
In the fourth embodiment, each light-shielding portion is formed on each edge portion 4 of the diffraction grating 2. The material of the light-shielding portion is the same as in the first to third embodiments.

The embodiment described above is directed to a wide band visible light (for example, 400 nm to 700 nm) as light incident on a diffractive optical element and an optical system having the same. A diffractive optical element to which visible light, a narrow band or a wide band of infrared light or ultraviolet light enters, and an optical system having the same can also be implemented. Further, the cross-sectional shape of the blazed diffraction grating is not limited to a sawtooth shape, but is a shape obtained by approximating the sawtooth with steps. The present invention relates to an optical element (binary optics) having such a stepwise cross-sectional shape. ) Is also applicable. Further, the present invention can be applied to both transmission type and reflection type optical elements. Further, the optical elements of the various forms described above can be used in various optical systems of photographing devices such as cameras, various optical systems of observation devices such as binoculars and microscopes, and various optical systems of projection devices such as liquid crystal projectors and steppers. .

[0017]

As described above, according to the present invention, there is provided a diffractive optical element in which light passing through the edge of a diffraction grating does not significantly deteriorate optical performance due to flare.
An optical system, a photographing device, and an observation device having the diffractive optical element can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a second embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of a third embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of a conventional example.

FIG. 5 is a sectional view showing a configuration of a conventional example.

FIG. 6 is a sectional view showing a configuration of a conventional example.

[Explanation of symbols]

 1: a glass member serving as a base of a blazed diffraction grating 2: a synthetic resin member forming a blazed diffraction grating 3: a relief pattern surface 4: an edge portion 5: incident light 6: emission light 7: light shielding portion

Claims (9)

[Claims] 1. A diffractive optical element comprising a light shielding means for shielding light incident on an edge of a diffraction grating or light emitted from the edge. 2. The diffractive optical element according to claim 1, wherein the light shielding means is provided on a light incident side of the diffraction grating, and shields light incident on the diffraction grating. 3. The diffractive optical element according to claim 1, wherein the light shielding means is provided on a light exit side of the diffraction grating, and shields light emitted from the diffraction grating. 4. The diffractive optical element according to claim 1, wherein the light shielding portion has a diffractive action. 5. The diffractive optical element according to claim 1, wherein said light shielding means has a plurality of light shielding portions arranged at substantially the same pitch as the grating pitch of said diffraction grating. . 6. The diffractive optical element according to claim 1, wherein the diffraction grating is formed by laminating a plurality of diffraction gratings made of at least two kinds of materials having different dispersions. 7. An optical system comprising the diffractive optical element according to claim 1. 8. An imaging apparatus comprising the optical system according to claim 7. 9. An observation apparatus comprising the optical system according to claim 7.