JP3242945B2 - hologram - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram, and more particularly, to a hologram having high diffraction efficiency.

[0002]

2. Description of the Related Art The diffraction efficiency of a relief hologram in which a transparent concavo-convex pattern corresponding to interference fringes is formed on a substrate surface is as follows.
It is given by the following relational expression (1).

I _m = {sin ² (πm / 2) / (πm / 2) ² ｝ cos ² [π ｛d (n-1) / λ-m / 2｝] (1) _Im is the diffraction efficiency, m is the diffraction order, d is the depth of the relief, n is the refractive index, and λ is the wavelength. Therefore, for example, in order to obtain the maximum value of the diffraction efficiency when m = 1, n = 1.50 and λ = 0.79 μm, a depth of d = 0.79 μm is required.

By the way, a conventional relief hologram is:
The uneven relief was provided only on one surface of the substrate. As the method of providing the unevenness, a method of providing a relief pattern by wet etching on the surface of the base material, a method of providing a relief pattern by ion etching on the surface of the base material, and using a photoresist as a base material, exposing an interference pattern thereto There is a method of making the photoresist relief by developing the photoresist.

[0005]

In order to form a relief hologram having high diffraction efficiency, a relief having a depth of at least about 0.8 μm is necessary as is clear from the above numerical examples.

[0006] However, in the case of a method of forming a relief by development using a photoresist, such a deep groove cannot be formed for the following reason.

(1) The resolution of the resist is poor. (2) Light scattering inside the resist (even if light is applied locally, it spreads within the resist). (3) There is light absorption in the resist.

In the above wet etching method, there is a phenomenon called side etching.
Etching can be performed only up to about 4 μm.

[0009] In the method using ion etching, a satisfactory deep groove is possible, but an apparatus for that purpose is expensive, and it is difficult to form a large-area relief pattern. Moreover, it is difficult to form an uneven pattern uniformly,
There is a problem that the etching rate is low.

The present invention has been made in view of such a situation, and has as its object to remove a photoresist or wet etching which has not been able to produce a relief hologram with high diffraction efficiency. An object of the present invention is to provide a hologram having a high diffraction efficiency, which can be produced even when used.

[0011]

As shown in FIG. 1, a hologram according to the present invention for achieving the above object has a single relief hologram 1 made of glass, photoresist, photopolymer, etc., and the hologram 1 and relief pattern. Prepare two relief holograms of another relief hologram 2 having a mirror image relationship, and superimpose them so that their relief patterns are coincident and their relief surfaces are in contact with each other. Air or a medium 3 having a different refractive index from the material forming the hologram is interposed,
The holograms 1 and 2 are configured by fixing them with an adhesive 4 outside the effective area. By configuring the hologram in this manner, even if the reliefs of the element relief holograms 1 and 2 are shallow, the depth of the effective unevenness of the superimposed hologram is a value that maximizes the diffraction efficiency in the relational expression (1). Can be Therefore, a hologram with high diffraction efficiency can be created even if a relief hologram with low diffraction efficiency created using photoresist or wet etching is used.

In the above, the element relief holograms 1 and 2 are formed by forming a relief by developing a photoresist, and the element relief holograms 1 and 2 are formed by etching a glass substrate or the like by a lithography technique and wet etching. Therefore, the hologram with high diffraction efficiency can be easily and quickly formed by the present invention. Also, since the groove of each relief hologram is shallow, 2
Duplication by the P method, the embossing method, or the like can be accurately performed, and an accurate high diffraction efficiency hologram can be easily formed.

By the way, as shown in FIG. 1, when the ridges of the concavo-convex pattern of the element relief holograms 1 and 2 are accurately aligned and fixed, the effective groove depth becomes too large, and the diffraction efficiency is rather reduced. It may decrease. Therefore,
As shown in FIG. 2, the diffraction efficiency can be improved by fixing the ridges with some deviation. For this purpose, the holograms 1 and 2 may be overlapped and fixed at a position where the amount of diffracted light is maximized while irradiating the laser light.

As shown in FIGS. 1 and 2, the relief surface
It is desirable to bond them so that they face each other, so that the relief layer is not exposed to the outside and the need for providing a protective layer is eliminated. In this case, it is possible to fill a material having a refractive index different from that of the relief forming material (the material of the ridge) between the concave grooves. In addition, although one or both of the relief surfaces may be bonded so that they face outward, in such a case, it is preferable to provide a protective layer or the like in order to prevent the relief surface from being damaged or stained.

In order to form the element relief holograms 1 and 2 having relief patterns which are mirror images of each other from one original hologram, several methods are conceivable. For example, the original relief hologram is copied a plurality of times. Is repeated, since the relief pattern has a mirror image relationship between the odd-numbered duplicate hologram and the even-numbered duplicate hologram, these may be used. Further, an amplitude hologram in which interference fringes are formed in a light and shade pattern is used as a mask, and one relief hologram is formed by exposing the amplitude hologram to a dry plate in close contact, and the other relief hologram has a mirror image relationship with the amplitude hologram. An amplitude hologram may be created, and this may be exposed and created by closely contacting it with a dry plate. In the case where a device having an accurate repetitive pattern such as a relief diffraction grating is formed, all of the element relief holograms 1 and 2 may be the same.

That is, in the hologram of the present invention, two relief holograms having the same interference fringe pattern or an element hologram composed of a relief diffraction grating are formed such that the ridges and grooves of the interference fringe pattern face each other. It is characterized by being fixed so as to overlap.

[0017]

Further, the relief of the element hologram is generally constituted by the unevenness of the resist, the unevenness of the glass, and the like.

Further, a transparent medium such as a liquid having a refractive index different from that of the ridge may be filled between the concave grooves of the element hologram.

When the element hologram is a phase diffraction grating, a phase diffraction grating with high diffraction efficiency can be realized.

As an alignment in the production process, two relief holograms having the same interference fringe pattern or element holograms composed of relief diffraction gratings are superimposed on each other. It is desirable to fix to.

[0022]

In the present invention, two interference fringe patterns are the same.
The element hologram consisting of a single relief hologram or relief diffraction grating is fixed and configured so that the ridges and grooves of the interference fringe pattern face each other and overlap each other, so that the effective Since the depth of irregularities can be the value that maximizes diffraction efficiency, it is possible to create holograms with high diffraction efficiency even when using relief holograms with low diffraction efficiency created using photoresist or wet etching. it can.

[0023]

Next, embodiments of the present invention will be described with reference to the drawings. As the photoresist 7, OFR800 manufactured by Tokyo Ohka Co., Ltd. was used, and two glass substrates 5 were used.
6 was coated at 1500 rpm using a spinner to obtain two relief hologram dry plates.

On the other hand, a chrome mask composed of an amplitude hologram formed by binarizing interference fringes is prepared, and the back side of the mask is brought into close contact with one of the dry plates to emit ultraviolet rays of 40 mJ.
Irradiated.

After that, as a developing solution, N
The exposed dry plate was developed using MD-3, and FIG.
The element relief hologram 8 having one section shown in FIG.

Next, the chrome mask is turned over,
The front side was brought into close contact with the other dry plate, irradiated with ultraviolet rays at 40 mJ, and developed with the same developer as above to obtain another relief hologram 9 whose relief pattern had a mirror image relationship with the element relief hologram 8 described above. .

The two element relief holograms 8 and 9 formed in this way are opposed to each other on the relief surface, and the outside of the effective area is bonded and integrated with a cyanoacrylic acid adhesive 10 to obtain a hologram with high diffraction efficiency. Could be obtained.

The positioning of the two 8 and 9 was performed by irradiating a laser beam so as to maximize the amount of diffracted light.

[0029]

As described above, according to the hologram of the present invention, two relief holograms having the same interference fringe pattern or an element hologram composed of the relief diffraction grating are formed by the ridges and the grooves of the interference fringe pattern. Since they are fixed so that they face each other and overlap, the depth of the effective unevenness of the superimposed hologram is
Since the diffraction efficiency can be maximized, a hologram with high diffraction efficiency can be created even if a relief hologram with low diffraction efficiency created by using photoresist or wet etching is used.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a basic configuration of a hologram of the present invention.

FIG. 2 is a sectional view of a hologram in which convex stripes of an element relief hologram are slightly shifted from each other.

FIG. 3 is a view for explaining one embodiment of a hologram manufacturing process according to the present invention.

[Explanation of symbols]

 1, 2 ... relief hologram 3 ... air or filling medium 4, 10 ... adhesive 5, 6 ... glass substrate 7 ... photoresist 8, 9 ... element relief hologram

Claims (5)

(57) [Claims] An element hologram composed of two relief holograms or relief diffraction gratings having the same interference fringe pattern is fixed so that the ridges and grooves of the interference fringe pattern face each other and overlap each other. A hologram characterized by becoming. 2. The hologram according to claim 1, wherein a relief of the element hologram is formed by a concave and convex of a resist. 3. The hologram according to claim 1, wherein the relief of the element hologram is made of glass irregularities. 4. The hologram according to claim 1, wherein a transparent medium having a refractive index different from that of the ridge is filled between the concave grooves of the element hologram. 5. A method in which two relief holograms having the same interference fringe pattern or element holograms composed of relief diffraction gratings are overlapped and fixed to each other at a position where the amount of diffracted light is maximized while irradiating light. The hologram creation method according to any one of claims 1 to 4, wherein