JPS63289580A - Hologram - Google Patents

Abstract

PURPOSE:To form the hologram image photographed by a Denisyuk method in such a manner that the interference fringes uncomfortable to eyes are invisible and to greatly improve image quality by reducing the interference fringes to be generated in the reconstructed image to such fineness at which said fringes are hardly visible. CONSTITUTION:The interference fringes to be generated in the reconstructed image of the hologram to be photographed by projecting the luminous flux 2 from a light source 1 as a reference luminous flux to a recording carrier 5 and using the luminous flux 12 transmitted through the recording carrier 5 as the illumination light of an object 6 to be photographed are reduced to the fineness at which the fringes are hardly visible. Namely, the visibility lowers with a decrease in the pitch of the interference fringes. There are substantially no harms for image observation if the fringes are about 2 pieces at 1mm, i.e., if the pitch decreases to <=0.5mm. The harmful interference fringes generated in the reconstructed image of the hologram photographed by the Denisyuk method are, therefore, removed by adequately selecting the thickness of a substrate and providing a suitable wedge angle thereto at the time of printing the hologram.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hologram, and particularly to a hologram in which a high-quality reflection type image is recorded on a polyvinylcarbazole recording material.

[Conventional technology]

BACKGROUND ART Conventionally, a method called the Denishk method has been known as one of the imaging techniques for recording a volumetric reflection hologram image. This photographing technique spreads a light beam from a laser light source using a microscope objective lens, etc., and irradiates it onto a hologram record carrier on a transparent substrate.The light beam is then used as a reference beam, and at the same time, the light beam that has passed through the substrate and the record carrier is used as a reference beam. This method is used as a light beam for object illumination.

This photographic technique is capable of photographing with a very simple optical system, has high luminous flux utilization efficiency and can perform exposure in a short time, and has a high quality of recorded hologram images (the hologram images can be observed). It has many characteristics such as a very large viewing area.

However, conventionally, hologram images taken using the Denischk method have unsightly interference fringes, which can significantly reduce image quality.

[Problem that the invention seeks to solve]

In particular, the applicant had previously proposed
No. 53) When a polyvinylcarbazole-based hologram record carrier is used, its refractive index is 1.6 to 1.7.
Therefore, there is a problem in that the interference fringes are more conspicuous than when conventionally used silver salt films or dichromate gelatin hologram recording carriers are used.

Specifically, for a recording material with a refractive index of 1.5, the reflectance at the interface with air is , but when the refractive index increases to 1.7, it increases significantly, and this causes visual It was doing a harmful job.

Therefore, the purpose of the present invention is to make the harmful interference fringes that occur when combining the conventional Denishk method holographic imaging method with high refractive index materials such as polyvinyl carbazole materials practically harmless, and to provide a wide viewing area for reproduced images. and moisture resistance,
The purpose of the present invention is to provide a hologram with excellent diffraction efficiency.

[Means for solving problems]

The above object is achieved by the present invention as follows.

That is, the present invention provides a hologram in which a light beam from a light source is irradiated onto a record carrier as a reference light beam, and a light beam transmitted through the record carrier is photographed as illumination light for an object to be photographed.
This hologram is characterized in that the interference fringes that occur in the reproduced image are so fine that they are difficult to see.

[For production]

The present invention will be explained in detail using a first embodiment of the present invention shown in FIG.

Monochromatic light 2 from a laser light source 1 is expanded by a microscope objective 3 into a spherical wave 10 and is incident on a record carrier 5 coated on a transparent substrate 4 . The light beam transmitted through this record carrier becomes an illumination light beam for the object 6. As a result, the light beam diffusely reflected by the object 6 enters the record carrier 5 from the right side in the figure and becomes object light, and reflection type hologram recording is performed by interference with the reference light entering from the left side.

Assume now that the substrate 4 is a parallel plate with a thickness d and a refractive index n. A part of the light beam 11 that enters the substrate 4 at an incident angle θ is reflected at the interface between the record carrier 5 and the air, and then reflected again by the surface of the substrate 4 on the incident side, becoming a light beam 12 and flowing into the air. eject into.

On the other hand, the light beam 11' enters the substrate 4 at an incident angle θ',
After passing through the record carrier 5, it becomes a light beam 12' and is emitted into the air. Since the light beams 12 and 12' generally form a small angle, interference fringes with a relatively large pitch are formed on the record carrier 5 and the object 6 due to interference between the two.

If the pitch of these interference fringes is coarse, for example 5 mm or more, it will be very unsightly, but if the pitch is fine, the visibility will decrease, and the interference fringes will have a rough pitch of about 2 per l m m, that is, a pitch of 0.5 mm.
It has been experimentally confirmed that if the diameter is less than mm, there is almost no harm to image observation.

In the embodiment shown in FIG. 1, the pitch P of the interference fringes is calculated as follows.

Refraction angle θ1: n5inθ1=sinθ (1)
Incident angle θ': Rcosθtanθ'=Rsin
θ+2dtanθ1 (2) Pitch P:P(sinθ
'-5inθ)=λ (3) From equation (1), sinθ1=
-sinθ Substituting this into equation (2) and rearranging it gives the following equation.

Assuming d<<R, the following relationship is obtained.

Pcos (θ'-θ)=λ (5) (5
) and (4), the following equation is obtained.

Therefore, the conditions for producing interference fringes finer than the visibility limit pitch Px are as follows.

From equation (7), in order to obtain a pitch that is difficult to visually recognize, it is achieved by decreasing R (IR1≦1000 mm), increasing d, and adjusting θ (θ≧5°).

Specifically, the wavelength λ=0.488 μm, the refractive index n of the substrate
=1.5. If the light source distance R = 300 mm, the incident angle θ = 15', and the substrate thickness d = 5, 0 mm, then P = 0.09 mm, which means that sufficiently fine interference fringes can be obtained. Even if the thickness d is reduced to 1.1 mm, P=0.41 mm, and sufficiently fine interference fringes can be obtained.

Next, the present invention will be explained with reference to a second embodiment.

In the first embodiment, the illumination light flux is made to be a diverging or converging light from an appropriate distance (IRI≦1000).
mm) and by setting the illumination direction at an appropriate angle (θ≧5°), fine interference fringes were obtained. However, as is clear from equation (6), when the illumination light is a parallel light flux (R = (X)) or when the illumination is perpendicular to the substrate (θ = 0), how to calculate the other values? Even if it is set to , it is impossible to make the pitch of interference fringes finer.

The second embodiment of the present invention, which is also effective in such cases, will be explained in the second embodiment.
This will be explained using figures.

In the figure, a light beam 2 from a laser light source 1 is transmitted through a microscope objective lens 3. The collimator lens 9 converts the light into a parallel light beam, which enters the recording medium 5 on the substrate 4 to become reference light, and at the same time becomes illumination light for the object 6.

Assuming that the substrate 4 with the refractive index n has a rust angle φ, the pitch P of the interference fringes created by the light beams 12 and 12' is given by the following equation.

Therefore, the light beam is incident perpendicularly (θ=0), and the refractive index n=1
．． 5. When the wavelength of laser light is λ=0.488 μm,
To satisfy P≦0, 55 mm, φ≧3.25
It is sufficient if X 10-' (rad) φ≧1,1'.

In this example, the case where the incident light is a parallel beam is shown, but this method of adding a wedge to the substrate is equally effective when the incident light is diverging or converging, and can be performed at the same time as selecting the substrate thickness. It is possible.

' A third embodiment of the present invention will be described using FIG. 3.

A light beam from a laser light source 1 is combined with a diverging light 10. As a result, sufficiently fine interference fringes occur in the illumination light for the object 6, which cannot be seen with the naked eye.

The size of this unevenness may be about 1 to 10 μm, and it can be easily processed by mechanical or chemical methods. Further, since it requires extremely small diffusivity compared to a diffuser plate, there is no risk of blurring the image of the object 6.

The present invention has been explained above, but as the constituent material of the record carrier used in the present invention, any of the materials described in JP-A-53-15153 can be suitably used. By using a vinylcarbazole polymer, a hologram with excellent moisture resistance and diffraction efficiency can be obtained.

Furthermore, as for the method of developing a recording carrier to obtain a hologram, the hologram of the present invention can be obtained by performing swelling and shrinking steps as described in Japanese Patent Application Laid-Open No. 53-15153.

〔Effect of the invention〕

As described above, in the present invention, it is possible to remove harmful interference fringes that occur in the reproduced image of a hologram photographed by the Denishk method by a simple method of appropriately selecting the substrate thickness during hologram printing and adding an appropriate rust angle. It has become possible.

In particular, in the present invention, there is no need to use expensive polished glass, and it is now possible to obtain a reproduced hologram image with a wide viewing range and high image quality even when using inexpensive float glass or template glass. Therefore, it has great advantages in terms of cost reduction and mass production.

[Brief explanation of drawings]

Fig. 1 is an optical system layout diagram showing a first embodiment of the invention, Fig. 2 is a diagram showing a second embodiment of the invention, and Fig. 3 is a diagram showing a third embodiment of the invention. This is a hail diagram.

Claims (3)

[Claims] (1) Interference fringes that occur in a reproduced image in a hologram in which a light beam from a light source is irradiated onto a record carrier to serve as a reference beam, and the light beam transmitted through the record carrier is photographed as illumination light for an object to be photographed. A hologram characterized by a detail that is difficult to see. (2) The hologram according to claim 1, wherein the pitch of the interference fringes is 0.5 mm or less. (3) The hologram according to claim 1, wherein the recording carrier is mainly composed of a polyvinylcarbazole material.