JPH04250486A - Preparation of hologram - Google Patents

Abstract

PURPOSE:To offer an improved method for stably preparing the hologram which has high diffraction efficiency and no variance. CONSTITUTION:A recording material for holography after being applied to a substrate is stored in a dark room under specific environment for a specific time before an exposure process, and the recording material for holography after being stored in the dark room is irradiated with light energy having a specific level before or after the exposure to set the film of recording material optically.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for producing holograms, and more specifically, the present invention relates to a method for producing holograms, and more particularly, a series of steps such as exposure, development, and drying are carried out using a holographic recording material containing dichromate gelatin as a photosensitizer. The present invention relates to a method for manufacturing holograms.

0002

2. Description of the Related Art Recently, the number of optical devices using holograms has been increasing, and in line with this trend, high diffraction efficiency has been required for holograms. One of the photosensitizers that meets this requirement for high diffraction efficiency is dichromate gelatin (
DCG), and a holographic recording material using this DCG as a photosensitive agent is known as a so-called DCG dry plate. However, this DCG dry plate has a problem in that the reproducibility in the manufacturing process is poor, and therefore the obtained diffraction efficiency varies significantly, making it impossible to stably obtain a hologram with high diffraction efficiency.

0003

[Problem to be solved by the invention] The present inventors have discovered that DCG
As a result of investigating poor reproducibility in the manufacture of dry plates, we found that most of the causes are related to the hardening state of the gelatin film before exposure or development. Therefore, the hardening process of the gelatin film is an important point in obtaining high diffraction efficiency.

[0004] Accordingly, it is an object of the present invention to provide an improved method for stably manufacturing holograms with high and consistent diffraction efficiency.

[0005]

[Means for Solving the Problem] According to the present invention, the above-mentioned object is achieved by using a holographic recording material containing dichromate gelatin as a photosensitizer to produce a holographic image through a series of steps such as exposure, development, and drying. In manufacturing, the holographic recording material coated on the substrate is stored in a dark room for a predetermined period of time under a predetermined environment before exposure, and the holographic recording material after being stored in the dark is stored in a dark room before or after exposure. This can be achieved by a hologram manufacturing method characterized in that the recording material is photohardened by irradiating the recording material with a predetermined level of optical energy.

In the practice of the present invention, the photohardening step is usually carried out before exposure, and although it is advantageous to do so, in some cases it is possible to carry out this step even after a certain time lag before exposure, or even if this step is not carried out. It may be performed after the exposure is completed.

[0007]

[Function] In the present invention, with the aim of stably obtaining a hologram with high diffraction efficiency, a dry plate coated with dichromate gelatin is stored in a dark room under a specified environment, and then subjected to a specified photohardening process. Apply the film amount and expose using the same method as before.
I suggest developing it. Here, by storing dichromate gelatin in a dark room for a specified period of time under a specified environment, the photodural layer before exposure becomes uniform, and it is possible to obtain a stable hardened layer condition at an early stage. Become. These effects combine synergistically to bring about the effects of the present invention.

[0008]

[Examples] The present invention will be described below with reference to Examples. FIG. 1 shows a flowchart of an example of the hologram manufacturing method of the present invention including a photohardening process. A dichromate gelatin aqueous solution (usually with a gelatin concentration of 3 to 2
5%, dichromic acid concentration 5-25%) by spin coating, bar coating, dip coating, wheeler coating, etc. to a film thickness of 1 to 25% after drying.
A DCG dry plate is obtained by coating to a thickness of about 25 μm and subsequently drying. Next, this DCG dry plate is heated under a predetermined environment, for example, 20° C. to 50% RH (relative humidity).
Store in a dark room under the following conditions. Next, since the sensitivity of the DCG dry plate is high in the ultraviolet region of the spectrum, the gelatin surface of the dry plate is irradiated with light using a light source that includes wavelengths in the ultraviolet region, such as a mercury lamp or an ultraviolet lamp, to accommodate the storage time in a dark room. A predetermined photodural treatment is performed. In this way, the hardening type DC
Obtain a G dry plate.

Subsequently, the dry plate is exposed. As an example of this exposure, exposure of a transmission type hologram is shown in FIG. Glass substrate 101 and DCG film 1 coated on the substrate
02, a reference beam 2 separated from a single coherent light source (not shown) and a point P
1. Inject the object light 3 which is more divergent at a certain angle,
Interference fringes are recorded on the DCG film 102. After this exposure step, the photohardening step performed before exposure may be performed, as already mentioned.

Next, the exposed DCG dry plate is developed and dried in a conventional manner. Development is carried out, for example, by removing unreacted chromium from the DCG film by washing with water under stirring for about 3 minutes at 20°C, and at the same time swelling the DCG gelatin film itself. This is done by immersing it in the liquid for about 3 minutes while stirring. Next, the dry plate was immersed in a 100% isopropyl alcohol solution at 20°C for about 3 minutes with stirring.
Rapid drying is performed in a high temperature oven at 80-120°C. A hologram is obtained through a series of steps like this. The mechanism for the formation of this hologram is thought to be that the tension in the gelatin caused by rapid dehydration as described above causes cracks in the unexposed areas, and a phase hologram is formed due to the difference in the refractive index of air gelatin. .

The hologram obtained as described above is
It can be reproduced as shown in FIG. exposed D
When the same light 12 as the reference beam 2 is incident on the hologram dry plate 11 obtained by developing and drying the CG dry plate 1 (FIG. 2) from the opposite direction, the incident light 12 is diffracted and converged by the hologram dry plate 11. The light 13 is converged to the same point (here, point P2) as the divergence point P1 (FIG. 2) during recording. The ratio of the diffracted light power to the incident light power at this time is called diffraction efficiency. In a hologram using DCG as a photosensitizer as in the present invention, a high diffraction efficiency of around 80% can be stably obtained.

According to the findings of the present inventors, a predetermined amount of photohardening exists in order to obtain the maximum diffraction efficiency for the storage time in a dark room after manufacturing the DCG dry plate. If the dry plate is exposed immediately after irradiation with the corresponding photohardening energy, a high diffraction efficiency of about 80% can always be stably obtained. FIG. 4 shows the relationship between storage time T and photodural energy K for obtaining a diffraction efficiency of about 80%. The optimal optical hardening energy K to obtain the maximum diffraction efficiency changes with the storage time T. Immediately after the dry plate is produced, the optimal hardening film amount is unstable and a stable and high diffraction efficiency cannot be obtained. After T0, a diffraction efficiency of around 80% can be stably obtained, and furthermore, after the storage time T1, the temporal change in photodural energy becomes smaller.
Diffraction efficiency of around 80% can be obtained very stably for a long period of time.

[0013] Furthermore, the film thickness of the DCG film and the photodural energy are almost proportional, and when the film thickness is thin, the photodural energy shifts to a smaller direction (changes from K1 to K2 in the figure). There is a similar tendency when the applied gelatin has a high jelly strength and a low concentration. However, if the manufacturing method of the DCG dry plate, film thickness, etc. are controlled, the characteristics will always be stable and a diffraction efficiency of around 80% can always be obtained.

In the above embodiment, a so-called transmission hologram was shown, but a reflection hologram may also be used. In this case, the substrate does not have to be light-transmissive.

[0015]

As explained above, in the present invention, a DCG dry plate coated with dichromate gelatin is stored in a dark room for a predetermined period of time under a predetermined environment, and the photohardening energy is adjusted according to the storage time. By performing exposure after or before irradiation, a hologram with high diffraction efficiency can always be obtained stably over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing a method for manufacturing a hologram according to the present invention in order.

FIG. 2 is a schematic diagram showing the exposure of a hologram according to the invention.

FIG. 3 is a schematic diagram showing the reproduction of a hologram according to the invention.

FIG. 4 is a graph showing the effect of storing a dry plate in a dark room on diffraction efficiency.

[Explanation of symbols]

1...DCG dry plate 2...Reference light 3...Object light 101...Glass substrate 102...CDG film

Claims (1)

[Claims] Claim 1: When producing a hologram through a series of steps such as exposure, development, and drying using a holographic recording material containing dichromate gelatin as a photosensitizer, the holographic recording material after being coated on a substrate. Before exposure, the material is stored in a dark room for a predetermined period of time under a predetermined environment, and before or after exposure, the holographic recording material stored in the dark room is irradiated with light energy at a predetermined level to produce the recording material. A method for producing a hologram, characterized by photohardening.