JPS6218914B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for creating a hologram used in an optical scanning device or the like that scans a light spot in multiple directions to read a bar code.

(b) Prior Art and Problems Holograms used in barcode reading devices for POS terminals and the like are created by interference of two coherent beams of light.

That is, interference fringes are formed by making one of two light beams having different wavefronts perpendicularly enter the hologram material plate and the other obliquely. In a hologram scanner using a hologram created in this manner, if one of the created waves is a reproduction wave, it is not possible to reduce the aberration of the wavefront obtained by reproduction of the hologram.

Therefore, the inventors of the present application have previously proposed a method of creating a hologram using two beams of light having wavefronts different from those of reproduction light, with the aim of reducing the above aberrations.
A hologram created by this method has a small aberration, but there is a problem in that the light utilization efficiency of the hologram during reproduction is not uniform.

Furthermore, holograms have the characteristic that they can be easily duplicated by a contact copying method, and one of the waves of the original is usually used for this copying. Therefore, the two-dimensional distribution of interference fringes within the hologram plane and the inclination of interference fringes in the thickness direction of the hologram recording material are almost the same as those of the original, and therefore the obtained replica has almost the same characteristics as the original. You can. However, on the other hand, the above-mentioned problems of holograms are not solved at all.

Therefore, in order to solve this difficulty, the applicants of the present application have proposed a method for creating a hologram in which close copying is performed using a light beam having a wavefront (third wavefront) different from the two created waves as a copy wave.

The method for creating the hologram described above is based on the two-dimensional distribution of interference fringes of the hologram and its inclination in the thickness direction.
Since they can be controlled independently, the obtained hologram replica has small aberrations over the entire area, and the utilization efficiency of the reproduction light can be uniformly controlled to a desired value.

Although this method has the above advantages, since the incident direction of the copying light is significantly different from the above-mentioned created wave, only a small amount of diffracted light is generated during copying, so the contrast of the interference fringes is insufficient, and a high-quality hologram cannot be obtained. The problem is that it cannot be done.

(c) Object of the Invention The object of the present invention is to solve the above-mentioned problems, and to enable independent control of the two-dimensional distribution of interference fringes within the hologram plane and the inclination in the thickness direction of the hologram recording material.
Another object of the present invention is to provide a method for creating a hologram that can form interference fringes with clear contrast.

(d) Structure of the invention The feature of the present invention is that the first
A light beam having a wavefront of A method for creating a hologram in the form of a wave, the hologram comprising:
A copy consisting of a first hologram created by interference of the two created waves as an original, superimposed on a second hologram recording material different from the first hologram, and then a light beam having the third wavefront. The light is directed into a third direction different from the first and second incident directions.
In the hologram creation method of creating a replica of the first hologram by irradiating from the incident direction of the hologram, the first hologram is used as an original,
A first copy is created by irradiating the copy light from a fourth direction between the first or second incident direction and the third incident direction, and then the first copy is used as the original. creating a second copy by irradiating the copy light from a fifth direction between the fourth incident direction and the third incident direction;
Thereafter, the above operations are repeated one after another, and finally the copy light is irradiated from the third direction to create a desired copy.

(e) Examples of the invention The present invention will be explained in detail below with reference to Examples.

FIG. 1 is a sectional view of main parts for explaining the hologram creation method according to the present invention in relation to reproduction light, and FIG.
5 to 5 are sectional views of essential parts showing one embodiment of the present invention.

In FIG. 1, 1 is a hologram recording material; 2 is a hologram recording material;
and 3 are the first and second creation lights of the hologram,
2 is a plane wave, 3 is a spherical wave, 4 is an interference fringe, 5A, 5
B, 5C is the reproduction light which is the reproduction incident wave and is a plane wave, 6
A, 6B, 6C are first-order diffracted lights, 7A, 7B, 7C
is the zero-order light which is the reproduced emitted wave.

As seen in the figure, a hologram is a spherical wave 2 that diverges from a point light source with a finite height, as is well known.
Interference fringes 4 with a plane wave 3 emitted from a point at infinity are created by forming on the hologram recording material 1. To perform laser beam scanning using this hologram, reproduction light, for example, a vertically incident plane wave, which is different from any wavefront at the time of hologram creation is irradiated, and the positional relationship between the hologram and the reproduction light is moved relatively. In the figure, the reproduction light is moved in the direction of arrow A to 5A, 5B, and 5C, but the hologram is actually moved in the direction of arrow B. In this way, the reproduction light becomes the zero-order light 7A to 7 that has passed through the hologram.
First-order diffracted light 6A~ diffracted by C and interference fringes 4
6C. In addition, in the same figure, the angle θ ₀
is the intersection angle between the second created wave 2 and the reproduced beams 5A, 5B, and 5C.

An embodiment of the present invention described below uses the hologram created as described above as an original, and when performing contact copying using the 0th-order light (or 1st-order diffracted light) generated during the reproduction, the incident copy light is Close copying is performed using the first copying light whose direction is tilted toward the incident direction of one of the two created waves, for example, the first created wave (plane wave) 2, and the first hologram obtained here is The copy is used as the original again, and the incident direction of the first copy light is shifted to the zero-order light side to perform contact copying to create a second copy, and this process is repeated sequentially until the final copy. In this example, a desired duplicate hologram is created using the zero-order light as the copy light.

FIG. 2 is a cross-sectional view of a main part showing the process of creating a hologram original plate of this embodiment, in which a hologram recording material plate 12 having a hologram recording material (photosensitive emulsion film) 1 on a glass substrate 11 is placed on a hologram recording material plate 12 as described above. It is irradiated with two created waves, a plane wave 2 and a spherical wave 3.

In this way, as shown in FIG. 3, interference fringes 4 are formed over the entire area of the hologram recording material 1 on the bisector of the intersecting angle α between the two created waves 2 and 3.

Using the hologram 13 thus obtained as an original, contact copying is performed as shown in FIG. 4 to create a first copy of the hologram. That is, the hologram original plate 13 and the new hologram recording material plate 14 are
The hologram recording materials 1 and 15 are stacked facing each other, and the hologram original plate 13 is exposed to the copy light 1.
Irradiate at 6. Here, the copy light 16 has a relationship between the incident direction of the first created wave 2 and the incident direction of the desired copy light 17 to be used last (in this embodiment, a light beam having the same wavefront as the zero-order light). A light beam incident from the direction of angle θ ₁ , which is slightly smaller than angle θ ₀ , is used. This light beam has the same type of wavefront as the desired copy light 17 described above. In this embodiment, since the copy light 17 is a plane wave,
A plane wave is used as the copy light 16 in this step.

Next, as shown in FIG. 5, the first copy 14' obtained as described above is used as an original, and the light is incident from a direction where the angle θ ₂ formed with the desired copy light 17 is smaller than the above-mentioned angle θ ₁ . A second copy 19 is created using the second copy light 18. This second copy light 18 is also a plane wave and differs from the desired copy light 17 and the first copy light 16 only in the direction of incidence.

The copy created in the previous step is used as the original,
The operation of performing contact copying using copy light whose intersection angle with respect to the desired copy light 17 is successively smaller than that in the previous stage is repeated.

The final copy created using the desired copy light 7 in this way is the hologram that is the object of this embodiment. FIG. 6 is a sectional view of a main part showing this final step, in which the duplicate hologram 20 created in the previous step is used as an original, and the desired copy light 17 is irradiated to obtain the desired duplicate hologram 21.

The hologram creation method of this embodiment described above, like the conventional hologram creation method described above, independently controls the two-dimensional distribution of interference fringes in the hologram plane and the inclination in the thickness direction of the hologram recording material. Not only can it be obtained, but also interference fringes with good contrast can be formed.

Note that the wavefront of the copy light used in the hologram creation method of the present invention does not need to be particularly limited, and may be different from either of the two created waves of the hologram master, in short, the wavefront of the copy light used in the final stage. The light is used by changing the direction of incidence between the direction of incidence of the light and the direction of incidence of one of the created waves so that the direction of incidence of the light is sequentially approached from the direction of incidence of the created wave to the direction of incidence of the final copy light. ,
Using such a light flux as copy light, a desired duplicate hologram is created through multiple steps.

(f) Effects of the Invention As explained above, according to the present invention, it is possible to create a hologram that has small aberrations over the entire area, uniformly high utilization efficiency of reproduction light, and interference fringes with good contrast. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part for explaining the outline of a method for producing a hologram according to the present invention, and FIGS. 2 to 6 are cross-sectional views of main parts showing an embodiment of the present invention in the order of manufacturing steps. In the figure, 1 and 15 are hologram recording materials;
2 and 3 are the hologram creation lights, 2 is a plane wave,
3 is a spherical wave, 4 is an interference fringe, 5A, 5B, 5C are reproduction lights, 6A, 6B, 6C are first-order diffracted lights, 7A, 7
B, 7C are zero-order lights, 12, 14, 19 are hologram recording material plates, 13, 14', 20 are hologram original plates, 16, 17, 18 are copy lights, 21 is a finally obtained hologram, θ ₀ , θ ₁ , θ ₂ indicate the angle of intersection with the direction of incidence of the desired copy light 17.

Claims (1)

[Claims] 1 A third wavefront that is created by using a light flux having a first wavefront incident from a first direction and a light flux having a second wavefront incident from a second direction as a created wave, and which is different from the two light fluxes. A method for creating a hologram in which a light beam having by superimposing it on a second hologram recording material different from the above, and then irradiating a copy light consisting of a light beam having the third wavefront from a third incident direction different from the first and second incident directions. , in the hologram creation method of creating a copy of the first hologram, the first hologram is used as an original, and the copy light is directed between the first or second incident direction and the third incident direction. A first copy is created by irradiating from a fourth direction, and then, using the first copy as an original, the copy light is applied to a fifth direction between the fourth direction of incidence and the third direction of incidence. A hologram characterized in that a second copy is created by irradiating from the direction, the above operations are repeated sequentially, and finally a desired copy is created by irradiating the copy light from the third direction. How to make.