JPH06202551A - Multiple exposure method for hologram photosensitive agent - Google Patents

Abstract

PURPOSE:To enhance and uniformalize the diffraction efficiency of each of the reconstruction wavelengths obtd. by subjecting the same hologram photosensitive agent layer to multiple exposing at the same wavelength. CONSTITUTION:The hologram photosensitive agent (gelatin) layer 2 is exposed and recorded in descending order of exposing angles (e.g. 44.9'', 30.0', 14.3') and the exposures are successively increased (200mJ/cm<2> 210mJ/cm<2> 265mJ/ cm<2>), by which the high and uniform diffraction efficiency (71.0%, 74.5%, 70.0%) is realized even at the different reconstruction wavelengths (630.6nm, 526.9nm, 480.0nm).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiple exposure method for hologram sensitizers.

[0002]

2. Description of the Related Art Recently, there has been a demand for a hologram optical element in which multiple exposures are made to the same photosensitive agent. As a conventional technique for producing this hologram optical element, there is a method of recording different reproduction wavelengths by exposing at different recording angles with the same recording wavelength. (Toshihiro Kubota, "Research on characteristics and applications of lip-run holograms", The University of Tokyo, Production Technology Research Report No. 30
Vol. 2, p. 72-74).

[0003]

However, when the hologram photosensitive material is subjected to multiple exposure by the above method, it is difficult to control the diffraction efficiency at each reproduction wavelength to a target value, and there is a problem that there is a large variation in each diffraction efficiency. It was Therefore, an object of the present invention is to provide a method of controlling the diffraction efficiency of each reproduction wavelength to be high and uniform while exposing at the same wavelength to obtain a plurality of reproduction wavelengths.

[0004]

In order to achieve the above object, the present invention provides a hologram photosensitive material in which a hologram photosensitive material layer is exposed twice or more at different exposure angles at the same wavelength to record different reproduction wavelengths. In the multiple exposure method, there is provided a multiple exposure method for a hologram photosensitive agent, characterized in that the exposure order is such that the exposure angle is changed from large to small and the exposure amount is sequentially increased.

In the present invention, the exposure angle refers to the angle of incidence on the photosensitive layer during exposure. As will be described later in detail, the exposure angle itself is basically determined by a desired reproduction wavelength and reproduction angle, but in the present invention, exposure is performed in order from the larger exposure angle to the smaller exposure angle. Interference fringes are less likely to be formed as the exposure angle is larger, and the more the exposure is repeated, the more the photosensitizer is hardened and the interference fringes are less likely to be formed. This is because

Further, in the present invention, the exposure amount is increased as the exposure is repeated. Generally, the smaller the exposure angle is, the easier the interference fringes are formed. However, in the case of the present invention, since multiple exposure is performed, although the exposure angle is sequentially reduced, the photosensitive agent is hardened and the interference fringes are formed. This is because it becomes difficult as it is repeated. However, according to the present invention, however, the diffraction efficiency of each reproduction wavelength after multiple exposure is increased by exposing in order from the larger exposure angle, increasing the exposure amount in order, and optimizing the exposure amount. And it becomes possible to control uniformly.

The composition of the hologram sensitizer used in the present invention is not particularly limited, but in the case of gelatin dichromate, it is usually composed of a photosensitive substance such as ammonium dichromate and gelatin.

[0008]

EXAMPLE FIG. 1 shows a state in which holograms are multiple-exposed on a hologram photosensitive material. The glass plate 1 is a colorless and transparent glass plate, but since both surfaces are not in contact with the air layer, no antireflection coating is applied. As the photosensitizer 2, for example, dichromated gelatin is applied to a thickness of about 25 μm. The mirror 3 may be a front surface mirror or a rear surface mirror, but it reflects incident laser light, and for example, a glass plate coated with aluminum can be used. An index matching liquid 4 is used between the prism 5 and the glass plate 1 and between the photosensitive agent 2 and the mirror 3 in order to eliminate the difference in refractive index. For example,
Silicone oil can be used.

The prism 5 is used so that the laser beam can easily enter when the exposure angle is steep, and the vapor deposition mirror 6 is used to change the angle for each recording when obtaining different reproduction wavelengths. Is. The laser light 7 has a single wavelength. The glass 1 coated with the photosensitizer 2 is optically integrated with the mirror 3 by using the index matching liquid 4, and the prism 5 is optically integrated with the mirror 3 by the index matching liquid 4. to this,
Inject laser light of the same recording wavelength at different recording angles,
The reflected light from the mirror and the incident light form interference fringes having different reproduction wavelengths inside the photosensitizer to record a hologram.

Thus, in the case of multiple exposure (at least two times or more) with the same wavelength on the same photosensitizer, according to the present invention, exposure is performed from the one having a large exposure angle at which interference fringes are hard to be formed, and at that time. The exposure amount was gradually increased. The recording angle (exposure angle) was calculated according to the following formula. λ cos θ ₀ = λ ₀ · cos [sin ^-1 {(sin θ) / n}]
In the M _z formula, λ: wavelength during reproduction λ ₀ : wavelength during recording θ: reproduction angle θ ₀ : recording incident angle (exposure angle) n: refractive index of photosensitizer Mz: expansion coefficient of photosensitizer layer Mz = (film thickness of hologram photosensitive material during reproduction) /
(The film thickness of the hologram photosensitive material at the time of recording).

In this embodiment, the wavelength for reproduction is 47.
0 nm, 520 nm and 620 nm are used as the wavelengths for recording 51
4.5nm is selected, and the reproduction angle is 45 for both incident angle and output angle.
It was °. The refractive index of the photosensitizer is 1.52 and Mz is 0.96.
4 (at reproduction wavelength 620 nm), 0.989 (reproduction wavelength 52)
0 nm) and 1000 (reproduction wavelength 470 nm). By calculation, the recording angle (exposure angle) θm is 44.9 ° (at reproduction wavelength 620 nm), 30.0 ° (reproduction wavelength 520 nm).
1) and 14.3 ° (at a reproduction wavelength of 470 nm), which correspond to l, m, and n in FIG. 1, respectively.

Therefore, according to the present invention, the recording angle (exposure angle) is changed from 44.9 ° (l) to 30.0 ° (m) to 14.3.
Exposure is performed in the order of ° (n), and the exposure amount is
In 200 mJ / cm ^2, m in 210 mJ / cm ^2, n in the 2
It was set to 65 mJ / cm ² . In this way, the diffraction efficiency of each wavelength of the hologram trunk plate obtained by developing the photosensitive agent after the multiple exposure was extremely uniform as shown in FIG. The specific values are shown below.

Η _l = 71.0%, η _m = 74.4%, η
_{n = 70.0%; λ l =} 630.6nm, λ m = 526.9nm, λ n = 48
0.0 nm. All of these diffraction efficiencies easily achieved our target of 60% or more, and were 70% or more and controlled extremely uniformly.

[0014]

According to the present invention, it is possible to realize uniform and high diffraction efficiency irrespective of the reproduction wavelength by performing multiple exposure on the same hologram photosensitive material at the same wavelength.

[Brief description of drawings]

FIG. 1 shows a state of multiple exposure according to an embodiment.

FIG. 2 shows the diffraction efficiency for each reproduction wavelength of the hologram produced in the example.

[Explanation of symbols]

 1 ... Glass plate 2 ... Photosensitive agent (gelatin) layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Ando 1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd. (72) Inventor ▲ Tachi ▼ Hiroyuki Hayashi 1-1, Showa-cho, Kariya city, Aichi Within Nippon Denso Co., Ltd.

Claims (1)

[Claims] 1. In a multiple exposure method of a hologram photosensitive material, wherein the hologram photosensitive material layer is exposed twice or more by changing the exposure angle at the same wavelength to record different reproduction wavelengths, the exposure order is from large to small. A multiple exposure method of a hologram photosensitive material, which is characterized in that the exposure amount is sequentially increased.