JP2003149420A - Diffractive optical element and molding die for the diffractive optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diffractive optical element capable of easily and accurately measuring the grating direction and grating period of diffraction grating having various cross-sectional shapes. SOLUTION: The diffractive optical element 1 is provided with an index 3 linearly extended along the grating direction of the diffraction grating and consisting of a deformed part selected from a projected or recessed shape of which a cross section vertical to the grating direction is different from the surface shape of a diffraction grating forming face 1b, a plane shape and a shape having a level difference 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 whose grating direction and grating period can be easily measured, and a molding die for the diffractive optical element.

[0002]

2. Description of the Related Art For example, in an optical system of an image display device, a diffraction grating is generally interposed between a display element and an observer's eye in order to make displayed pixels inconspicuous. ing. In this regard, JP-A-6-294
Japanese Patent No. 955 discloses a liquid crystal display device in which moire fringes are prevented from occurring by arranging the diffraction grating with the grating direction inclined with respect to the pixel arrangement direction of the liquid crystal display element.

Further, in Japanese Patent Laid-Open No. 5-227456, a diffraction grating having a sinusoidal diffraction grating forming surface,
A liquid crystal projection viewfinder has been disclosed in which a diffraction grating having a grating pitch equal to or smaller than the pixel pitch of a liquid crystal cell is used to suppress deterioration of image contrast and image quality.

To use such a technique, it is essential to measure the grating direction or the grating period of the diffraction grating. Therefore, conventionally, a method of measuring with an optical magnifying device, a method of measuring the diffraction grating formation surface of the diffraction grating with a surface roughness measuring device using a dedicated jig, and calculating the grating direction or grating period The method of observing the interference fringes by the diffraction grating using an interferometer and measuring the grating direction or the grating period from the result has been adopted.

[0005]

However, when the conventional diffraction grating is measured by each of the above methods, there are the following problems. That is, in the method using the optical magnifying device, not only the sinusoidal shape but also the curved surface shape (R shape) in the cross section is used.
It is difficult to accurately obtain the grating direction and the grating period of the diffraction grating having

Further, in the method using the surface roughness measuring device,
The cost for producing the dedicated jig is high, and the time required for the measurement is too long. Further, the method using the interferometer has a problem that it takes time to perform the measurement and the measurement result varies.

The present invention has been made in view of the above circumstances, and a diffractive optical element and a diffractive optical element capable of easily and accurately measuring the grating direction and the grating period of a diffraction grating having various sectional shapes. An object is to provide a mold for molding an element.

[0008]

According to a first aspect of the present invention, there is provided a diffractive optical element which linearly extends along the grating direction of the diffraction grating and has a cross section perpendicular to the grating direction with respect to the diffraction grating forming surface. The surface shape is characterized by having an index composed of a deformed portion having a deformed shape.

According to a second aspect of the present invention, in the diffractive optical element according to the first aspect, the index is selected from a shape protruding or recessed with respect to a diffraction grating formation surface, a plane shape, or a shape having a step portion. It is characterized by that.

According to a third aspect of the present invention, in the diffractive optical element according to the first or second aspect, the cross section of the diffraction grating forming surface of the diffraction grating perpendicular to the grating direction has at least a curved portion. It is a thing.

According to a fourth aspect of the present invention, in the diffractive optical element according to any one of the first to third aspects, the index is
It is characterized in that the diffraction grating is provided on the diffraction grating formation surface at a period of n times the grating period (n is a natural number).

According to the diffractive optical element of the present invention, a deformed portion, that is, a portion selected from a shape protruding or recessed with respect to the diffraction grating forming surface, a plane shape, or a shape having a step portion is used as an index. Thereby, it becomes possible to easily and accurately measure the grating direction and the grating period of the diffraction grating having various sectional shapes from the direction and the interval of the index.

Further, according to the diffractive optical element of the present invention, since the cross section of the diffraction grating forming surface perpendicular to the grating direction has a curved portion and the diffraction grating forming surface is provided with an index, it has an irregular shape. It is possible to easily and accurately measure the grating direction and the grating period of the diffraction grating having various cross-sectional shapes, from the direction and the interval of the index that is the portion.

Further, according to the diffractive optical element of the present invention,
Since a plurality of irregularly shaped portions used as an index are provided with a period that is a natural multiple of the grating period, it is possible to easily and accurately measure the grating direction and the grating period of a diffraction grating having various cross-sectional shapes. .

According to a fifth aspect of the present invention, there is provided a molding die for a diffractive optical element, which linearly extends along a lattice formation direction of a lattice formation surface and has a cross section perpendicular to the lattice formation direction on the lattice formation surface. On the other hand, it is characterized in that it is provided with a mold piece having an index forming portion composed of a deformed portion having a deformed surface shape.

According to a sixth aspect of the invention, in the molding die for the diffractive optical element according to the fifth aspect, the index forming portion is
It is characterized by being selected from a shape protruding or recessed with respect to the lattice formation surface, a plane shape, or a shape having a step portion.

According to a seventh aspect of the present invention, in the molding die for the diffractive optical element according to the fifth or sixth aspect, the cross section of the grating formation surface perpendicular to the grating formation direction has at least a curved portion. It is what

The invention according to claim 8 is the molding die for a diffractive optical element according to any one of claims 5 to 7,
The index forming part has a lattice formation period of n on the lattice formation surface.
It is characterized in that it is provided at a cycle of twice (n is a natural number).

According to the molding die of the present invention, the section extending linearly along the lattice formation direction of the lattice formation surface and the cross section perpendicular to the lattice formation direction is the surface shape with respect to the lattice formation surface. Has an index forming portion composed of an irregularly shaped part, and therefore, when a diffractive optical element having an index is molded using a molding die, the molded diffraction grating has various cross-sectional shapes. Also, it is possible to form a diffractive optical element capable of easily and accurately measuring the grating direction and the grating period from the direction and the interval of the index.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A diffractive optical element and a molding die thereof according to an embodiment of the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) (Structure) A diffractive optical element according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 10. FIG. 1 is a schematic perspective view of the diffractive optical element 1 according to the first embodiment, and FIG. 2 is a partially enlarged perspective view including a sectional shape of an index 3.

FIG. 3 is a sectional perspective view of a main part of the diffractive optical element 1 including the index 3, and FIG. 4 is a partially enlarged perspective view including the sectional shape of the index 3 shown in FIG.

5 to 8 are sectional views showing various modifications of the sectional shape of the index 3, FIG. 9 is a sectional view showing modifications of the sectional shape of the diffraction grating forming surface, and FIG. 10 is a diffractive optical element. It is explanatory drawing which shows the example of measurement of the lattice direction of 1 and a lattice period.

The diffractive optical element 1 shown in FIG. 1 is a diffraction grating forming surface 1 of a substrate 1a made of glass fiber or light-transmitting resin.
b, a diffraction grating is formed in a plane wave shape. The external dimensions of the base material 1a are, for example, the long side X is 24 mm, the short side Y is 15 mm, and the thickness t is 1 mm. A line connecting points having the same phase of the diffraction grating is referred to as a grating direction, and the grating direction of the diffractive optical element 1 has a certain angle of inclination with respect to the outer shape of the substrate 1a.

FIG. 2 is a partially enlarged perspective view of a cross section of the diffractive optical element 1 of FIG. 1 taken along a plane perpendicular to the grating direction.
The cross-sectional shape 2 of the diffraction grating formation surface 1b has an amplitude H of 0.6 μ.
It has a sine wave shape with m and a period P of 1 mm.

Further, on the diffraction grating forming surface 1b, an index 3 having a slender groove shape extending parallel to the grating direction and having a depth L and a width M recessed with respect to the sectional shape 2 of the diffraction grating forming surface 1b.
Are provided with the same period as the grating period P of the diffraction grating.

In the first embodiment, the depth L of the index 3 is 0.05 μm and the width M is 1 μm, but the depth L is 0.1.
It has been confirmed that the optical performance of the diffractive optical element 1 is not affected by the presence of the index 3 as long as the index 3 is less than μm and the width M is less than 1 μm. The amplitude H of the cross-sectional shape 2 of the diffraction grating formation surface 1b is 0.3 to 1.0 μm, and the period P is 0.5 to 1.5.
It can be selected in the range of mm.

A diffractive optical element 4 shown in FIG. 3 shows a modified example of the diffractive optical element 1 of the first embodiment, in which a diffractive grating forming surface 4b of a base material 4a made of glass fiber or light transmissive resin is formed. The diffraction grating is formed concentrically. Therefore, in the case of the diffractive optical element 4, the lattice direction is circular. FIG. 4 is a partially enlarged perspective view of a cross section of the diffractive optical element 4 of FIG. 3 taken along a plane perpendicular to the grating direction (along the radial direction). The other configurations of the diffractive optical element 4 are the same as those of the diffractive optical element 1.
Therefore, detailed description thereof will be omitted, and hereinafter, description will be made based on the diffractive optical element 1.

To manufacture the diffractive optical element 1, there are a cutting method and an etching method. In the method by cutting, as shown in FIG.
When a normal diffraction grating is formed by cutting in b, the index 3 is formed simultaneously by instantaneously cutting the blade deeper by 0.05 μm for each grating period P.

Further, in the etching method, as shown in FIG. 6, when a normal diffraction grating is formed on the diffraction grating formation surface 1b by etching, the etching depth becomes 0.05 μm deeper for each grating period P. By doing so, the index 3 is simultaneously formed (the depth L of the index 3 is 0.0
5 μm, width M is 1 μm).

The cross-sectional shape 2 of the index 3 is not limited to the shape depressed into the diffraction grating forming surface 1b as shown in FIGS. 5 and 6, but also the diffraction grating forming as shown in FIGS. Surface 1b
The shape may be a mountain shape or a step shape protruding outward from.

In the first embodiment, the sectional shape 2 of the diffraction grating forming surface 1b has a sine wave shape, but as shown in FIG. 9, only the corner 14 having the trapezoidal sectional shape 13 has a curved shape. The diffraction grating forming surface 1b can also be used. The index 3 similar to that shown in FIG. 6 is also provided on the diffraction grating formation surface 1b shown in FIG.

(Operation) The operation of the first embodiment will be described below. As shown in FIG. 10, when measuring the grating direction and the grating period, the diffraction grating forming surface 1b of the diffractive optical element 1 is used.
Is magnified by an optical magnifying device 20 such as a microscope and visually detected. The lattice direction and the lattice period are measured from the index 3 visually observed. At this time, as shown in FIG. 10, when the illumination light 22 is emitted from the lighting fixture 21 from a direction perpendicular to the grating direction and oblique to the diffraction grating formation surface 1b, the index 3 is observed by the optical magnifying apparatus 20. Can be performed more easily.

(Effect) According to the first embodiment, the diffractive optical element 1 can be obtained by a simple means such as the optical magnifying device 20.
It is possible to easily and accurately measure the grating direction and the grating period. Therefore, when the diffractive optical element 1 is used in an image display device, the generation of moire fringes is prevented by tilting the grating direction of the diffraction grating with respect to the arrangement direction of the pixels of the display element, and the grating period is a liquid crystal. By using a diffraction grating having a pixel pitch of the cell or less, it is possible to suppress deterioration of image contrast and image quality. Further, even in the case of the diffractive optical element 1 in which the front surface is the diffraction grating forming surface 1b and the back surface is the mirror surface, the diffraction grating forming surface 1
There is also an advantage that it is possible to easily visually judge that b is the surface by the presence or absence of the index 3.

In the first embodiment, the diffractive optical element 1
Although a plurality of indexes 3 are provided on the diffraction grating formation surface 1b at intervals of the grating cycle P, one index 3 may be provided, or a plurality of indexes 3 may be provided at a cycle of a natural number n times the grating cycle P. In the former case, the grating period P cannot be measured, but the grating direction can be known. In the latter case, the grating period P can be quickly obtained by dividing the measured period of the index 3 by n, and the lattice direction is more accurate than in the case where the number of the index 3 is one. You can know

(Embodiment 2) (Structure) With reference to FIGS. 11 to 17, a molding die for a diffractive optical element and a method for molding a diffractive optical element using the same according to Embodiment 2 of the present invention will be described. Explain. 11 is a schematic perspective view of the mold piece 30 of the molding die, FIG. 12 is a cross-sectional view of the mold piece 30, FIG. 13 is a cross-sectional view of a modified example thereof, and FIG. 14 is a detail of the cut mold piece 30. A cross-sectional view, FIG. 15 is a schematic cross-sectional view of an injection molding die 40 using this mold piece 30, and FIG. 16 is a schematic of a diffractive optical element 45 including an index 46 molded using the injection molding die 40. FIG. 17 is a cross-sectional perspective view of the main part of the diffractive optical element 45 including the index 46.

The mold piece 30 shown in FIG. 11 is formed by forming a diffraction grating in a plane wave shape on a grating forming surface 31 of a base material made of nickel or the like. The cross-sectional shape 32 of the mold piece 30 is shown in FIG.
As shown in FIG. 2, it has a sinusoidal shape with an amplitude H and a period P, or as shown in FIG. 13, it has a shape in which only the corner 34 of the trapezoidal sectional shape 33 is curved, but in either case. It has the same shape as the diffractive optical element 45 to be molded.

Further, on the grid forming surface 31 of the mold piece 30,
As shown in FIG. 14, the index forming portion 36 having a planar shape with a width M extending parallel to the grating direction is provided at the same period as the grating period P of the diffraction grating.

In the second embodiment, the width M is 1 μm, but it is confirmed that if the width M is 1 μm or less, the optical performance of the molded diffractive optical element 45 is not affected even if the index molding portion 36 is provided. Has been done.

As shown in FIG. 15, the injection molding die 40 is composed of a fixed die 41 and a movable die 42.
The fixed mold 41 is provided with the above-mentioned mold piece 30 on the grid forming surface 3
1 is arranged so as to face the movable mold 42. In the movable mold 42, a mold piece 43 has a mirror-finished surface fixed to the fixed mold 41.
It is placed in a state of facing.

(Operation) In the second embodiment, the diffraction grating is formed on the grating forming surface 31 of the mold piece 30 by cutting or etching. In the method by cutting, as shown in FIG. 14, at the time of forming a normal diffraction grating, the blade 35 of the diamond bite is moved in the XY direction while being in contact with the grating forming surface 31, so that every grating period P. By moving the blade 35 by 1 μm only in the X direction, the index forming portion 36 having a planar shape is simultaneously formed.

The diffractive optical element 4 is formed by the injection molding die 40.
To mold 5, the fixed mold 41 and the movable mold 42 are closed, the melted light-transmitting resin is injected into the cavity 44 between the mold piece 30 and the mold piece 43, and then cooled. Thus, the diffractive optical element 45 having the index 46 as shown in FIGS. 16 and 17 is formed in the cavity 44.

That is, the diffractive optical element 45 has a mold piece 30.
At the same time that the diffraction grating formed on the grating forming surface 31 of the
Is formed.

(Effect) According to the second embodiment, a mold piece 30 having a grating molding surface 31 having a shape corresponding to the required diffraction grating shape of the diffractive optical element 45 is prepared, and injection is performed by disposing the mold piece 30. Since injection molding is performed using the molding die 40,
It is possible to easily create a large number of diffractive optical elements 45 having the index 46 without secondary processing.

(Embodiment 3) (Structure) FIGS. 18 and 1 show a molding die of Embodiment 3 and a method of molding a diffractive optical element using the molding die.
This will be described with reference to FIG. FIG. 18 is a cross-sectional view showing a state of cutting the mold piece 48 of the third embodiment, and FIG. 19 is a schematic perspective view of the cut mold piece 48.

The mold piece 48 shown in FIG. 19 has a diffraction grating formed in a plane wave shape on a grating formation surface 49 formed on a base material made of nickel or the like. Cross-sectional shape 52 of mold piece 48
Is the same amplitude H as the sectional shape of the diffractive optical element to be molded,
It has a sine wave shape with a period P. Further, on the grating formation surface 49, an index forming portion 54 having a step of depth L extending parallel to the grating direction is provided with a blade 50 at the same cycle as the grating cycle P of the diffraction grating as shown in FIGS. Is formed by using. Since other configurations are the same as those in the second embodiment, description thereof will be omitted.

(Operation) According to the third embodiment, the diffraction grating is formed on the grating forming surface 49 of the mold piece 48 by cutting or etching. In the cutting method, as shown in FIG.
The diffraction grating is formed by moving the blade 50 in the X-Y directions in accordance with a preset machining program while contacting with 9. In this case, the blade 50 is programmed to move along a sine wave shape, but since it actually moves with a low resolution digital value, it starts from the origin G (0, 0) shown in FIG. 18 and G ′. 1 up to (P, 0)
Even if it is attempted to move by one cycle, one cycle actually ends at (P ', L) shown in FIG. 18 (where,
P ′ ≦ P, L> 0). At this point, the blade 50 is forcibly moved to (P ', 0) and the next one cycle is cut. By repeating this, the mold piece 48 having the index forming portion 54 as shown in FIG. 19 can be produced.

When a diffractive optical element is molded by the injection molding mold 40 using the mold piece 48 in the same manner as in the second embodiment, a diffractive optical element having an index corresponding to the index molding section 54 is obtained. can get.

(Effect) According to the third embodiment, the cutting is performed by utilizing the processing error naturally generated by the resolution, so that the complicated movement control of the cutting tool 50 is not required, and the diffractive optical element A mold piece 48 having a grating molding surface 49 having a shape corresponding to the diffraction grating shape can be created.

[0050]

According to the present invention, by using the deformed portion provided on the diffraction grating formation surface as an index, the grating direction and the grating period of the diffraction grating having various cross-sectional shapes can be easily and accurately measured. It is possible to provide a diffractive optical element capable of

Further, according to the present invention, since the index forming portion which is a deformed portion is provided on the lattice formation surface, various portions can be obtained by using the portion of the diffractive optical element obtained by transferring this as an index. A mold for molding a diffractive optical element capable of easily and accurately measuring the grating direction and grating period of a diffraction grating having a cross-sectional shape can be provided.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a diffractive optical element according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged perspective view including a cross-sectional shape of the index according to the first embodiment.

FIG. 3 is a sectional perspective view of a main part of the diffractive optical element including the index according to the first embodiment.

4 is a partially enlarged perspective view including a cross-sectional shape of the index shown in FIG.

FIG. 5 is a sectional view showing a modified example of the sectional shape of the index according to the first embodiment.

FIG. 6 is a sectional view showing a modified example of the sectional shape of the index according to the first embodiment.

FIG. 7 is a cross-sectional view showing a modified example of the cross-sectional shape of the index according to the first embodiment.

FIG. 8 is a sectional view showing a modified example of the sectional shape of the index according to the first embodiment.

FIG. 9 is a cross-sectional view showing a modified example of the lattice formation surface of the first embodiment.

FIG. 10 is the grating direction of the diffractive optical element according to the first embodiment,
It is explanatory drawing which shows the measurement example of a grating period.

FIG. 11 is a schematic perspective view of a mold piece of the molding die according to the second embodiment of the present invention.

FIG. 12 is a cross-sectional view of a mold piece according to the second embodiment.

FIG. 13 is a cross-sectional view of a modified example of the mold piece according to the second embodiment.

FIG. 14 is a detailed cross-sectional view of a die piece that has been subjected to cutting processing according to the second embodiment.

FIG. 15 is a schematic cross-sectional view of an injection-molding die using the die piece according to the second embodiment.

FIG. 16 is a schematic perspective view of a diffractive optical element molded by using the injection molding die of the second embodiment.

FIG. 17 is a cross-sectional perspective view of a main part of the diffractive optical element including the index according to the second embodiment.

FIG. 18 is a cross-sectional view showing a manner of cutting a mold piece according to Embodiment 3 of the present invention.

FIG. 19 is a schematic cross-sectional perspective view of a die piece that has been cut according to the third embodiment.

[Explanation of symbols]

1 Diffractive optical element 1a Base material 1b Diffraction grating formation surface 2 cross-sectional shape 3 indicators 4 Diffractive optical element 4a base material 4b Diffraction grating formation surface 13 Cross-sectional shape 14 corners 20 Optical magnifying device 21 Lighting equipment 22 Illumination light 30 mold pieces 31 Lattice formation surface 32 cross-sectional shape 34 corners 35 cutlery 36 Index forming part 40 Injection Mold 41 Fixed mold 42 Movable mold 43 mold pieces 44 cavities 45 diffractive optical element 46 indicators 48 mold pieces 49 Lattice formation surface 50 cutlery 52 Cross-sectional shape 54 Index forming unit

Claims (8)

[Claims] 1. An index, which extends linearly along the grating direction of the diffraction grating and has a deformed portion whose cross section perpendicular to the grating direction is different from the surface shape of the diffraction grating forming surface, is provided. A diffractive optical element characterized by the above. 2. The diffractive optical element according to claim 1, wherein the index is selected from a shape protruding or recessed with respect to the diffraction grating formation surface, a planar shape, or a shape having a step portion. 3. The diffractive optical element according to claim 1, wherein a cross section of the diffraction grating forming surface of the diffraction grating perpendicular to the grating direction has at least a curved portion. 4. The index is provided on the diffraction grating formation surface of the diffraction grating at a period of n times the grating period (n is a natural number), according to any one of claims 1 to 3. Diffractive optical element. 5. An index comprising a deformed portion that extends linearly along the lattice formation direction of the lattice formation surface and has a cross section perpendicular to the lattice formation direction that is different from the surface shape of the lattice formation surface. A mold for molding a diffractive optical element, comprising a mold piece having a forming portion. 6. The diffractive optical element according to claim 5, wherein the index forming portion is selected from a shape protruding or recessed with respect to the grating formation surface, a planar shape, or a shape having a step portion. Mold for molding. 7. The mold for molding a diffractive optical element according to claim 5, wherein a cross section of the grating formation surface perpendicular to the grating formation direction has at least a curved portion. 8. The index forming portion is provided on the lattice formation surface at a period n times as long as a lattice formation period (n is a natural number), according to any one of claims 5 to 7. Mold for molding diffractive optical element.