JPH0277782A - Formation of hologram - Google Patents

Abstract

PURPOSE:To form a hologram which is not affected by disturbance such as vibrations, air fluctuations, etc., in exposure and has sharp interference fringes and superior diffraction efficiency by transmitting coherent luminous flux through one transparent refraction body and then splitting it into two pieces of luminous flux which have different wave fronts, and making them interfere with each other on a dry plate. CONSTITUTION:The light beam from a coherent light source is passed through a collimator, etc., and one piece of luminous flux 1 which has a plane wave is incident on the 1st plane 21 of the transparent refraction body 2 at right angles while extending to the 2nd plane 22. Luminous flux 11 from the plane 21 in the incident luminous flux is not refracted and travels straight in the refraction body 2 to exit from the 3rd plane 23 to air, thereby having a plane wave front. Further, luminous flux 12 which is incident at an angle theta of incidence while the plane 22 serves as a refracting surface is projected from the plane 22 as 2nd luminous flux 12 slanting to the 1st luminous flux 1 as specified in the refraction body 2. Then the two pieces of luminous flux which are split are mode to interfere with each other on the dry plate 3 coated with a photosensitive agent.

Description

[Detailed Description of the Invention] [Summary] This relates to a method for creating a hologram, particularly a method for stably creating a hologram with high diffraction efficiency. The purpose of this project is to provide a method for creating a hologram with excellent diffraction efficiency, in which one coherent beam is divided into two beams with different wavefronts by passing through one transparent refractor, and the two beams are divided into two beams with different wavefronts. A method for creating a hologram by interfering bundles on a dry plate, wherein the transparent refractor has two surfaces, at least one of which serves as a refracting surface for the two bundles of rays, and the wavefront of the two bundles of rays forms a hologram. is passed across the two surfaces to be divided into two wavefronts, and the two divided wavefronts are caused to interfere on a dry plate placed close to the transparent refractor, thereby recording interference fringes. .

[Industrial application field]

The present invention relates to a method for creating a hologram, and particularly to a method for stably creating a hologram with high diffraction efficiency.

Holograms are widely used in barcode league laser scanners, printer laser scanners, various sensors, and optical equipment.

[Conventional technology]

FIG. 5 is a diagram showing a general method for creating a conventional hologram. In the figure, a coherent light beam from a laser light source 33 is transferred to a beam splitter 34 such as a half mirror.
The lens system 37, 38 splits the beam into two beams, reflects them by mirrors 35 and 36, and forms a wavefront after forming a predetermined angle between the two beams.
A lens system 38 forms a diverging spherical wave) into two beams, and a dry plate 31 coated with a photosensitizer is irradiated with both beams to cause interference. By developing the dry plate, a hologram in which interference fringes are recorded as a distribution of refractive index and transmittance is obtained.

In this case, the above-mentioned optical system usually has two optical paths formed by arranging each optical element in the air on a highly rigid optical surface plate or the like provided with anti-vibration measures.

[Problem to be solved by the invention]

In order to obtain a hologram duram with excellent diffraction efficiency, it is desirable that the recorded interference fringes be clear. For this purpose, it is necessary to keep the optical path difference and relative angle of the two beams constant throughout the exposure time so that the interference fringes do not change.

However, in the hologram creation method using the conventional optical system, the two beams after being split by the beam splinter pass through the air for a relatively long distance, so local fluctuations in the optical path due to fluctuations in air pressure and temperature occur. refractive index fluctuation,
The optical path length changes due to minute deformations caused by vibration of the surface plate, and it is difficult to keep the substantial optical path difference between the two beams strictly constant during the exposure time. For this reason, there was a problem in that the recorded interference fringes were not clear and the diffraction efficiency decreased.

The present invention was created in view of the above problems, and an object of the present invention is to provide a method for creating a high-performance hologram with excellent diffraction efficiency by removing disturbances such as vibrations and air fluctuations during exposure. shall be.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the hologram creation method of the present invention.

In order to solve the above-mentioned problems, the hologram creation method of the present invention, as shown in FIG. In this method, a hologram is created by interfering the two light beams on a dry plate 3, in which the transparent refractor 2 has two surfaces 21 and 22, at least one of which serves as a refraction surface for the two light beams 1. , the wavefronts of the two light ray bundles 1 are passed across the two surfaces 21 and 22 to be divided into two wavefronts, and the two divided wavefronts are arranged close to the transparent refracting body. It is characterized by recording interference fringes by causing interference on a dry plate 3.

[Effect]

Since two entrance or exit surfaces are integrally formed on the same transparent refractor, the geometric relative relationship (distance,
Since the change in angle) is extremely small, the variation in the optical path difference between the two beams is small.

When splitting at the entrance plane, most of the optical path of the two split beams until they reach the dry plate surface is within the transparent refractor, and when splitting at the output plane, the majority of the optical path is in the vicinity of the output plane. Due to the fact that a dry plate is provided in the
Since the distance that the light beam propagates through the air is extremely short, fluctuations in the optical path difference due to fluctuations in the air are small.

Therefore, it is possible to clearly record interference fringes, and it is possible to create a hologram with excellent diffraction efficiency.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 shows a first embodiment of the invention, FIG. 3 shows a second embodiment, and FIG. 4 shows a third embodiment.

In FIG. 2, 2 is a transparent refractive material such as glass, and has a first plane 21 and a second plane 22 that is in contact with the first plane at an obtuse angle formed on the top surface, and a plane 23 parallel to the first plane on the bottom surface. It has become.

(2) is a beam of light having a plane wavefront formed by passing a light beam from a coherent light source such as a laser through a collimator, etc., which is perpendicular to the first plane 21 of the transparent refractor 2.
The light is also made to enter the transparent refractive body 2 across the second plane. Then, among the light beams that have entered the transparent refracting body 2, the light beam 11 that has entered the plane 21 travels straight through the transparent refracting body 2 without being refracted, and exits into the air through the third plane 23, having a plane wavefront. This becomes the first luminous flux 11. Also the second plane 2
2 at an incident angle θ, the plane 22 becomes a refracting surface, and the ray bundle 12 incident on this plane forms a second ray bundle tilted at a predetermined angle with respect to the first ray bundle in the transparent refractor 2. 12
The light is emitted from the lower surface 23.

If the angles and surface sizes of the two planes 21 and 22 are appropriately determined, one beam of light incident across the two surfaces of the transparent refractor will form two beams with different wavefronts at the desired inclination angle. The beam is split into a bundle of rays, propagates through a transparent refractor, overlaps each other in the same area, and exits into the air, where the wavefronts interfere.

Reference numeral 3 denotes a dry plate coated with a photosensitizer, which is disposed close to, preferably in close contact with, the third plane 23, and is arranged so that the first beam 11 and the second beam bundle emitted from the transparent refractive body 2 12, and interference fringes corresponding to the optical path difference between the two beams are recorded.

In this case, since the transparent refracting body 2 is a solid body with high rigidity, the relative positional relationship between the incident surfaces is kept constant, and since the two ray bundles after wavefront division hardly pass through the air, fluctuations in the air, etc. Therefore, clear interference fringes are recorded with little temporal variation in optical path difference.

Furthermore, since the two-beam east interference system is formed by the integrated transparent refractor 2, there is little change over time, and when mass-producing the same hologram, it is possible to create holograms with good reproducibility and uniform characteristics.

FIG. 3 is a diagram showing a second embodiment, in which one of the two surfaces on which the light beam 1 is incident on the transparent refracting body 2 is a convex lens surface 24, so that the wavefront of the first light beam 13 after division is changed. is a spherical wave, and by making one or both of the two incident surfaces a plane, a convex lens surface, or a concave lens surface, the two beams of various wavefronts are made to interfere,
It is possible to form a hologram according to the purpose.

FIG. 4 shows a third embodiment, in which a plane wave ray bundle 1 perpendicularly enters one plane 25 on the upper surface of the transparent refractor 2.
are emitted across two plane surfaces 26 and 27 having different angles with respect to the wavefront to form two bundles of rays 14.
15, and even in this case, because the folding surfaces of both layers are integrally formed on the solid and the distance between them and the dry plate 3 is short, the time fluctuation of the optical path difference is small (compared to the conventional example). ,
A clear hologram can be obtained.

In the above, a parallel ray bundle having a plane wavefront was described as a ray bundle incident on a transparent refractor, but instead of a plane wave, a ζ convergent spherical wave or a diffuse spherical wave ray bundle may be used as necessary. can be done and the same effect can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, since it is not affected by disturbances such as vibrations and air fluctuations during exposure, it is possible to create a porogram with clear interference fringes and excellent diffraction efficiency, and a hologram application device It is remarkable that it contributes to higher performance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the hologram creation method of the present invention, FIG. 2 is a diagram showing the first embodiment, FIG. 3 is a diagram showing the second embodiment, and FIG. 4 is a diagram showing the second embodiment. FIG. 5 is a diagram showing a conventional hologram creation method. In the figure, 1-1-one ray bundle, 1L12- ray bundle after wavefront division, 2-transparent refractor, 21.2
2, 23, 24. 25 - Surface of transparent refractor, 3 - Dry plate of hologram, No. 30 2'5 I

Claims (1)

[Claims] 1. One coherent beam (1) is divided into two beams (11, 12) with different wavefronts by passing through one transparent refractor (2); A method of creating a hologram by interfering with a dry plate surface, the transparent refracting body (2) having two surfaces (21,
22 or 26, 27), and the one ray bundle (1
) on the two surfaces (21, 22 or 26, 2
7) and is split into two wavefronts, and the two split wavefronts are caused to interfere on a dry plate (3) placed close to the transparent refractor (2), thereby recording interference fringes. A hologram creation method characterized by: 2. The hologram production method according to claim 1, characterized in that a transparent refractor (2) having two refracting surfaces (21, 22) is used on the incident surface of the light beam. 3. The hologram production method according to claim 1, characterized in that a transparent refractor (2) having two refracting surfaces (26, 27) is used on the exit surface of the light beam.