JP3063274B2 - Method of manufacturing holographic optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention enables a simple and high-speed production of extremely high-accuracy volume reflection type holographic optical elements by a contact exposure method without using a master hologram. The present invention relates to a method for manufacturing a holographic optical element.

[0002]

2. Description of the Related Art Generally, a holographic optical element is a hologram having the same performance as an optical element such as a lens, a mirror, a half mirror and a prism.
The holographic optical element, particularly the volume reflection type holographic optical element, is used for, for example, external light and information light from a display device in a head-up display, a helmet mount display, a center high mount stop lamp, etc. of an airplane or an automobile. It is considered to be used as a combiner that also serves as a display.

The following method has been adopted as a method for producing this kind of volume reflection type holographic optical element.

First, as shown in FIG. 2, for example, an optical system including a laser 1, mirrors 2, 3, 4, 5, 6, a beam splitter 7, lenses 8, 9 and a concave mirror 10 is used to sensitize with parallel light. Material (master hologram) 1
Prepare No. 1.

That is, the volume reflection type holographic optical element captures an image using a light source having good coherence such as a laser. Here, in order to obtain a volume type, the light split into two by the beam splitter 7 is converted into parallel light, which is made incident from the front and back surfaces of the photosensitive material 11 to record interference fringes in the thickness direction of the photosensitive material 11. Further, as the photosensitive material 11,
For example, a dichromated gelatin, a silver salt photosensitive material, a photopolymer, or the like is considered, and interference fringes are recorded as refractive index modulation.

Next, as shown in FIG. 3, a photosensitive material 12 is brought into close contact with the master hologram 11 produced in this way, and linearly spread light 13 is incident thereon.
In this method, the same interference fringe as that of the master hologram 11 is recorded in the photosensitive material 12 by using the light 13 transmitted through 2 as reference light and the light 14 reflected and diffracted by the master hologram 11 as object light.

However, in such a manufacturing method,
There are the following problems.

That is, in the contact exposure method, the manufactured holographic optical element greatly depends on the performance of the master hologram 11. Therefore, master hologram 1
If 1 is distorted or shrunk in its manufacturing process, or if the diffraction efficiency is low, a good holographic optical element cannot be manufactured. In particular, the volume reflection type holographic optical element has a larger amount of recorded information than a surface relief type hologram and the like, and records interference fringes in the thickness direction of the photosensitive material. And it is difficult to produce a good holographic mirror. Further, when a holographic optical element is manufactured, it is necessary that an interference fringe to be recorded is accurate, and sufficient accuracy may not be obtained by copying using a conventional contact exposure method. Further, since it is necessary to prepare the master hologram 11 which is difficult to produce as a pre-process, it takes time to produce the holographic optical element, and there is a problem in mass production.

[0009]

As described above, in the conventional method of manufacturing a holographic optical element, since a master hologram must be used, a highly accurate volume reflection type holographic optical element is manufactured. However, there is a problem that it takes a long time to manufacture, and it is difficult to manufacture a large amount.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an extremely accurate volume reflection type holographic optical element can be simply and simply formed by a contact exposure method without using a master hologram. It is an object of the present invention to provide an extremely reliable method of manufacturing a holographic optical element which can be manufactured at high speed and in large quantities.

[0011]

In order to achieve the above object, when a holographic optical element is manufactured on a photosensitive material, first, in the invention according to the first aspect, the photosensitive material is mechanically metallized. It is inscribed in a reflection type diffraction grating made by engraving the surface and evaporating the surface with a metal, light is incident on the photosensitive material, and the light transmitted through the photosensitive material and the light reflected on the surface of the diffraction grating, A volume reflection type holographic optical element is manufactured on a photosensitive material.

Here, the back surface (the side opposite to the photosensitive material) of the substrate holding the photosensitive material is a diffraction grating.
The diffraction grating used is like a Fresnel zone plate. Further, the shape of the diffraction grating is a sawtooth shape or a rectangular wave shape. On the other hand, the space between the photosensitive material and the diffraction grating is immersed in a liquid having a refractive index substantially equal to that of the photosensitive material. Further, a plurality of diffraction gratings of different types are arranged in parallel, and a photosensitive material is adhered to the grating so that light is incident on the photosensitive material.
Further, the incident light is uniformly applied to the entire photosensitive material. Furthermore, as incident light, a laser beam is incident on the photosensitive material, and the laser beam is two-dimensionally scanned. Also, as incident light,
Light spread linearly is incident on a photosensitive material, and linear light is scanned in a one-dimensional direction. Further, as incident light, a laser beam is incident on the photosensitive material, and the photosensitive material is irradiated with a laser beam.
It moves in the dimensional direction and enters. Furthermore, as the incident light, linearly spread light is incident on the photosensitive material to move the photosensitive material in one-dimensional direction.

According to the twelfth aspect of the present invention, the photosensitive material is brought into close contact with a reflection type surface relief hologram produced by optically recording interference fringes and vapor-depositing the surface with a metal. A holographic optical element of a volume reflection type is manufactured on a photosensitive material by light incident thereon and transmitted through the photosensitive material and light reflected by a surface relief hologram.

Here, the back surface (the side opposite to the photosensitive material) of the substrate holding the photosensitive material is a surface relief hologram. In addition, a rectangular hologram having a high diffraction efficiency is used as the surface relief type hologram. Further, the space between the photosensitive material and the surface relief hologram is immersed in a liquid having a refractive index substantially equal to that of the photosensitive material. On the other hand, the incident light is uniformly applied to the entire photosensitive material. As incident light, a laser beam is incident on the photosensitive material, and the laser beam is two-dimensionally scanned. Further, as the incident light, linearly spread light is incident on the photosensitive material, and the linear light is scanned in a one-dimensional direction.
As the incident light, a laser beam is incident on the photosensitive material, and the photosensitive material is moved in the two-dimensional direction and is incident. Further, as the incident light, light spread linearly is incident on the photosensitive material, and the photosensitive material is moved in a one-dimensional direction.

[0015]

Accordingly, in the method of manufacturing a holographic optical element according to the present invention, when the holographic optical element is manufactured on a photosensitive material, the photosensitive material is manufactured by mechanically engraving a metal or the like and evaporating the surface with a metal. The photosensitive material is exposed to light by exposing the photosensitive material to the reflective diffraction grating, or the photosensitive material is adhered to a reflective surface relief hologram made by optically recording interference fringes and vapor-depositing the surface with metal. Then, by exposing the photosensitive material, a volume reflection type holographic optical element can be manufactured on the photosensitive material by light transmitted through the photosensitive material and light reflected by the diffraction grating or the surface relief hologram. .

This eliminates the need to produce a master hologram, so that a very accurate volume reflection type holographic optical element can be produced simply, at high speed, and in large quantities.

On the other hand, unnecessary reflection light can be prevented by immersing a liquid having a refractive index substantially equal to that of the photosensitive material between the photosensitive material and the diffraction grating or the surface relief hologram. In addition, since the back surface of the substrate holding the photosensitive material (the side opposite to the photosensitive material) is a diffraction grating or a surface relief hologram, the adhesion between the photosensitive material and the diffraction grating or the surface relief hologram is improved. Can be solved. further,
By using a diffraction grating like a Fresnel zone plate, a holographic optical element having a lens function can be manufactured. On the other hand, when a plurality of different types of diffraction gratings are arranged in parallel, a photosensitive material is brought into close contact with the photosensitive material, and light is incident on the photosensitive material to produce a holographic optical element in which a plurality of functions are arranged in parallel. Or, when making a large holographic optical element, simply set the direction and angle of the diffraction grating freely without making and arranging many volume reflection holograms that are difficult to fabricate, or fabricating a large master. The holographic optical element can be manufactured simply by arranging the holographic optical elements. As the incident light, a laser beam is incident on the photosensitive material, and the laser beam is scanned two-dimensionally, or linearly spread light is incident on the photosensitive material, and the linear light is scanned one-dimensionally. Or,
Alternatively, a laser beam is incident on the photosensitive material, and the photosensitive material is moved in the two-dimensional direction and is incident. Alternatively, light that has spread linearly is incident on the photosensitive material and the photosensitive material is moved in the one-dimensional direction. The interference fringes with good contrast can be recorded on the photosensitive material without being affected by the vibration.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of the overall configuration of a method for manufacturing a holographic optical element according to the present invention. In this embodiment, a holographic optical element is manufactured as follows. That is, as shown in FIG.
1 is brought into close contact with a reflective diffraction grating 22 prepared by mechanically engraving a metal or the like and evaporating the surface with a metal such as aluminum, so that light is applied to the photosensitive material 21 so that the light uniformly strikes the entire photosensitive material 21. Is incident. Thereby, the photosensitive material 2
The light 23 passing through 1 and the light 24 reflected on the surface of the diffraction grating 22 make it possible to manufacture a volume reflection type holographic optical element on the photosensitive material 21.

Here, as the photosensitive material 21, for example, a dichromated gelatin, a silver salt photosensitive material, a photopolymer or the like is used. In addition, the diffraction grating 22 is of a reflection type because a diffraction grating must be of a reflection type in order to manufacture a volume reflection type holographic optical element. It is a reflection type. In this case, specular light is generally generated on the aluminum surface, and unnecessary interference fringes are recorded in the photosensitive material. Therefore, in the present embodiment, a diffraction grating that has a tooth-like shape as shown in the drawing and has an appropriate depth to perform 100% diffraction without regular reflection light is used as the diffraction grating 22.

As described above, there is no need to prepare a volume reflection type master hologram which is difficult to produce, and the production accuracy of the volume reflection type holographic optical element is remarkably improved.

As described above, the manufacturing method of this embodiment is as follows.
When a holographic optical element is formed on a photosensitive material, the photosensitive material 21 is brought into close contact with a reflective diffraction grating 22 formed by mechanically engraving a metal or the like and evaporating the surface with a metal such as aluminum, thereby allowing light to pass therethrough. Light is incident on the photosensitive material 21 so as to uniformly hit the entire photosensitive material 21, and the light 23 transmitted through the photosensitive material 21 and the light 24 reflected on the surface of the diffraction grating 22 cause volume reflection on the photosensitive material 21. A holographic optical element is manufactured.

Therefore, unlike the conventional case, it is not necessary to manufacture a volume reflection type master hologram, which is difficult to manufacture, so that a very accurate volume reflection type holographic optical element can be easily and simply manufactured by the contact exposure method. High-speed and mass-production is possible.

In other words, in the conventional method in which the master hologram is a volume reflection type hologram, the production of the master hologram requires skill in hologram photographing, and the volume reflection type hologram photosensitive material (bichromic acid) Gelatin, silver salt photosensitive material, and photopolymer) each have disadvantages, and it is difficult to produce a high-quality master hologram. Specifically, dichromated gelatin has poor light sensitivity, is easily affected by vibration at the time of photographing, has poor durability, and is unsuitable for use as an optical element. The photopolymer also has a problem in sensitivity, and the silver salt photosensitive material has problems in durability and a change in thickness of the photosensitive material due to development processing. In this case, if this is a so-called Lippman hologram made for the purpose of display, the difference in partial brightness and the difference in reproduction wavelength will not be a problem, but in the case of a holographic optical element, the specified wavelength Is the specified brightness,
Moreover, it is necessary to diffract evenly over the entire hologram.

In this regard, the manufacturing method of this embodiment makes it possible to manufacture a high-precision holographic optical element using the reflection type diffraction grating 22 without manufacturing a volume reflection type master hologram. Become. In this case, the diffraction efficiency of the diffraction grating 22 can be controlled by changing the depth and shape of the grating, and 100% diffraction efficiency can be obtained as needed. The method of producing the diffraction grating 22 is simple if a metal engraving machine is used, and is particularly sufficient for producing interference fringes having a simple shape such as a holographic optical element. In addition, since interference fringes having a more complicated shape than a simple diffraction grating can be recorded, it is most suitable for incorporating a function as an optical element.

Next, another embodiment of the present invention will be described.

In the above embodiment, the photosensitive material 21 is exposed by bringing the photosensitive material 21 into close contact with a reflective diffraction grating 22 produced by mechanically carving a metal or the like and evaporating the surface with a metal such as aluminum. Thus, the case where the volume reflection type holographic optical element is manufactured on the photosensitive material 21 has been described. However, the present invention is not limited to this, and the volume reflection type holographic optical element can be manufactured as follows. .

That is, the manufacturing method of this embodiment is as follows.
Instead of the reflective diffraction grating 22 in FIG. 1 described above,
Using a reflection type surface relief hologram prepared by optically recording interference fringes and evaporating the surface with a metal such as aluminum, the photosensitive material 21 is brought into close contact with the reflection type surface relief hologram. A holographic optical element of a volume reflection type is formed on the photosensitive material 21 by making light incident on the photosensitive material 21 and transmitting the light through the photosensitive material 21 and the light reflected by the surface relief hologram.

Here, a reflection type surface relief type hologram having a rectangular wave shape and high diffraction efficiency is used.

As described above, according to the manufacturing method of this embodiment, it is not necessary to manufacture a volume reflection type master hologram which is difficult to manufacture as in the conventional case. The holographic optical element can be manufactured simply, at high speed, and in large quantities. Also, the production of surface relief holograms usually uses a photoresist as a photosensitive material, but it is not a volume type, but it records superficial interference fringes, which is considerably more than a volume reflection type hologram. It is simple.

In each of the above embodiments, the photosensitive material 21
A liquid having a refractive index substantially equal to that of the photosensitive material 21 may be immersed between the diffraction grating 22 and the surface relief hologram. Here, for example, xylene (refractive index: 1.5) or the like can be used as the liquid. That is, the photosensitive material 21 and the diffraction grating 2
2 (or a surface relief hologram) has poor adhesion, and if there is an air layer, light is repeatedly reflected on the front and back surfaces of the photosensitive material 21 to cause unnecessary interference fringes to be recorded. There is a risk. For this reason, unnecessary reflected light is prevented by flowing a liquid having a refractive index substantially equal to that of the photosensitive material 21 and immersing the liquid between the photosensitive material 21 and the diffraction grating 22 (or the surface relief type hologram). Becomes possible.

In the above embodiment, the photosensitive material 21
The back surface (the side opposite to the photosensitive material 21) of the substrate holding the
You may make it become a diffraction grating. That is, in the manufacturing method of the above embodiment, the adhesion between the photosensitive material 21 and the diffraction grating 22 is important. If the adhesion is poor, unnecessary interference fringes will be recorded, and the performance of the holographic optical element will deteriorate. Therefore, on the opposite surface of the glass or metal on which the diffraction grating was recorded in advance,
By applying or attaching a photosensitive material for producing a holographic optical element, it becomes possible to solve the above-mentioned problem of adhesion.

Further, in the above embodiment, the photosensitive material 2
Back side of substrate holding 1 (side opposite photosensitive material 21)
However, it may be configured as a surface relief type hologram. That is, in the manufacturing method of the above embodiment, the adhesion between the photosensitive material 21 and the surface relief hologram is important. If the adhesion is poor, unnecessary interference fringes will be recorded, and the performance of the holographic optical element will deteriorate. Therefore, it is possible to solve the above-mentioned problem of adhesion by applying or attaching a photosensitive material for producing a holographic optical element to a surface opposite to glass or metal on which a relief hologram is recorded in advance. Become.

On the other hand, in the above embodiment, the diffraction grating 22 to be used may be configured as a Fresnel zone plate. That is, a diffraction grating formed by cutting a metal is generally formed by cutting a straight line in one direction, and only a simple holographic optical element can be manufactured by performing close contact exposure using this as a master. Therefore, by operating the metal engraving machine in a circular shape and engraving it like a Fresnel zone plate, a holographic optical element having a lens function can be manufactured.

In the above embodiment, the diffraction grating 22
May have a rectangular wave shape.

Further, in the above embodiment, a plurality of diffraction gratings of different types are arranged in parallel,
1 may be brought into close contact with each other so that light is incident on the photosensitive material 21. This makes it possible to manufacture a large number of volume-reflection holograms, which are difficult to manufacture, and to arrange a large master holographic optical element when a holographic optical element having a plurality of functions arranged in parallel or a large holographic optical element is manufactured. A holographic optical element can be manufactured by simply arranging the diffraction gratings with their directions and angles set freely without manufacturing the holographic optical element, and the manufacturing process is further simplified. Becomes possible.

On the other hand, in each of the above embodiments, the case where the incident light is uniformly applied to the entire photosensitive material 21 has been described, but the invention is not limited to this. That is,
For example, as the incident light, a laser beam may be incident on the photosensitive material, and the laser beam may be two-dimensionally scanned. Further, as the incident light, linearly spread light may be incident on the photosensitive material, and the linear light may be scanned in a one-dimensional direction. Further, as the incident light, a laser beam may be incident on the photosensitive material, and the photosensitive material may be moved in the two-dimensional direction and incident. Furthermore, as the incident light, light spread linearly may be incident on the photosensitive material, and the photosensitive material may be moved in a one-dimensional direction. By adopting such a method, the influence of vibration is eliminated, and interference fringes with good contrast can be recorded on the photosensitive material 21.

In each of the above embodiments, the diffraction grating 22 (or surface relief type hologram) has been described as a reflection type by depositing a metal such as aluminum on the surface, but is not limited to this. Instead, a metal other than aluminum may be used as the vapor deposition metal.

[0039]

As described above, according to the present invention, when a holographic optical element is manufactured on a photosensitive material,
The photosensitive material is mechanically carved with metal or the like, and the surface is adhered to a reflective diffraction grating made by vapor-depositing the surface with metal, and the photosensitive material is exposed, or the photosensitive material is optically recorded with interference fringes. By exposing the photosensitive material by bringing the surface into close contact with a reflective surface relief hologram produced by vapor-depositing the surface with metal, the light transmitted through the photosensitive material and the light reflected by the diffraction grating or the surface relief hologram are exposed to light. As a result, a volume reflection type holographic optical element is manufactured on a photosensitive material, and without using a master hologram, an extremely accurate volume reflection type holographic optical element can be easily and simply manufactured by a contact exposure method. An extremely reliable method for manufacturing a holographic optical element which can be manufactured at high speed and in large quantities can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a method for manufacturing a holographic optical element according to the present invention.

FIG. 2 is a schematic diagram for explaining a method of manufacturing a master hologram for manufacturing a conventional volume reflection type holographic optical element.

FIG. 3 is a schematic diagram for explaining a method of manufacturing a conventional volume reflection type holographic optical element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laser, 2,3,4,5,6 ... mirror, 7 ... beam splitter, 8,9 ... lens, 10 ... concave mirror, 11
... photosensitive material (master hologram), 12 ... photosensitive material,
13 ... incident light, 14 ... reflected light, 21 ... photosensitive material, 22 ...
Diffraction grating, 23: incident light, 24: reflected light.

Claims (20)

(57) [Claims] 1. A method for producing a holographic optical element on a photosensitive material, wherein the photosensitive material is brought into close contact with a reflection type diffraction grating produced by mechanically engraving a metal or the like and evaporating the surface with a metal. Light is incident on the photosensitive material, and light transmitted through the photosensitive material and light reflected on the surface of the diffraction grating are used to produce a volume reflection type holographic optical element on the photosensitive material. A method for producing a holographic optical element. 2. The method for manufacturing a holographic optical element according to claim 1, wherein the back surface (the side opposite to the photosensitive material) of the substrate holding the photosensitive material is a diffraction grating. . 3. The method of manufacturing a holographic optical element according to claim 1, wherein the diffraction grating used is a Fresnel zone plate. 4. The method of manufacturing a holographic optical element according to claim 1, wherein said diffraction grating has a saw-tooth shape or a rectangular wave shape. 5. The holographic optical element according to claim 1, wherein a liquid having a refractive index substantially equal to that of the photosensitive material is immersed between the photosensitive material and the diffraction grating. Method of manufacturing. 6. The holographic apparatus according to claim 1, wherein a plurality of diffraction gratings of different types are arranged in parallel and a light-sensitive material is brought into close contact with the light-sensitive material so that light is incident on the light-sensitive material. Method for manufacturing optical element. 7. The method for manufacturing a holographic optical element according to claim 1, wherein the incident light is uniformly applied to the entire photosensitive material. 8. The holographic optical element according to claim 1, wherein a laser beam is incident on the photosensitive material as the incident light, and the laser beam is two-dimensionally scanned. Method. 9. The holo according to claim 1, wherein, as the incident light, linearly spread light is incident on a photosensitive material, and the linear light is scanned in a one-dimensional direction. A method for manufacturing a graphic optical element. 10. The holographic optical system according to claim 1, wherein a laser beam is incident on the photosensitive material as the incident light, and the photosensitive material is moved in a two-dimensional direction and is incident. Method for manufacturing element. 11. The holographic apparatus according to claim 1, wherein, as the incident light, linearly spread light is incident on a photosensitive material, and the photosensitive material is moved in a one-dimensional direction. Method for manufacturing optical element. 12. A method for producing a holographic optical element on a photosensitive material, wherein the photosensitive material is in close contact with a reflection type surface relief hologram produced by optically recording interference fringes and vapor-depositing the surface with metal. Light is incident on the photosensitive material, and light transmitted through the photosensitive material and light reflected by the surface relief hologram are used to produce a volume reflection holographic optical element on the photosensitive material. A method for producing a holographic optical element. 13. The holographic optical element according to claim 12, wherein the back surface (the side opposite to the photosensitive material) of the substrate holding the photosensitive material is a surface relief hologram. Production method. 14. The method of manufacturing a holographic optical element according to claim 12, wherein a holographic optical element having a rectangular wave shape and high diffraction efficiency is used as the surface relief hologram. 15. The liquid crystal display device according to claim 12, wherein the space between the photosensitive material and the surface relief hologram is immersed in a liquid having a refractive index substantially equal to that of the photosensitive material.
3. The method for producing a holographic optical element according to 1., 16. The method of manufacturing a holographic optical element according to claim 12, wherein the incident light is uniformly applied to the entire photosensitive material. 17. The holographic optical element according to claim 12, wherein a laser beam is incident on the photosensitive material as the incident light, and the laser beam is two-dimensionally scanned. Method. 18. The holo according to claim 12, wherein, as the incident light, linearly spread light is incident on a photosensitive material, and the linear light is scanned in a one-dimensional direction. A method for manufacturing a graphic optical element. 19. The holographic optical system according to claim 12, wherein a laser beam is incident on the photosensitive material as the incident light, and the photosensitive material is moved in a two-dimensional direction and is incident. Method for manufacturing element. 20. The holographic apparatus according to claim 12, wherein, as the incident light, linearly spread light is incident on the photosensitive material, and the photosensitive material is moved in a one-dimensional direction. Method for manufacturing optical element.