JPH0534668B2 - - 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 beam in multiple directions to read a bar code.

(b) Prior Art and Problems Holograms used in barcode reading devices for POS (Point of Sales) 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 reproduced wave, it is not possible to reduce the aberration of the wavefront obtained by reproducing the hologram.

Therefore, the inventors of the present application have previously proposed a method of creating a hologram using two light beams having wavefronts different from those of reproduction light, with the aim of reducing the above aberrations.
A hologram scanner using a hologram created by this method can reduce the above-mentioned aberrations, but there is a problem 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 in the hologram plane and the slope 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 reproduction 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.

(c) Object of the Invention The object of the present invention is to solve the above problems and to create a photogram in which the two-dimensional distribution of interference fringes within the hologram plane and the inclination in the thickness direction of the hologram recording material can be independently controlled. The purpose is to provide a method.

(d) Structure of the Invention The feature of the present invention is that two light beams having first and second wavefronts are created as a created wave, and a light beam having a third wavefront different from the two light beams is reproduced as an incident wave or a reproduction wave. A method for creating a hologram as an emitted wave, the hologram comprising superimposing a first hologram created by interference of the two created waves on a second hologram recording material different from the first hologram. Then, by irradiating a light beam having the third wavefront as copy light, the two-dimensional distribution of interference fringes created on the first hologram is transferred to the second hologram recording material, and Creation of a hologram characterized in that the transferred interference fringes in the second hologram recording material are created so that the inclination in the thickness direction thereof is different from the inclination in the thickness direction of the interference fringes in the first hologram. It's in the method.

The present invention will be explained in detail below using examples.

FIG. 1 is a cross-sectional view of a main part for explaining the method for creating a hologram according to the present invention in relation to reproduction light, and FIGS. 2 to 5 are cross-sectional views of main parts showing a first embodiment of the present invention. It is.

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

As seen in the figure, a hologram is produced by forming interference fringes 4 on a hologram recording material 1 between a spherical wave 2 emitted from a point light source at a finite height and a plane wave 3 emitted from an infinite point. Created. 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 same figure, the reproduction light is 5A, 5B, 5C and the arrow A
Although the hologram is shown moved in the direction of arrow B, in reality, the hologram is moved in the direction of arrow B. In this way, the reproduction light is the 0th order light 7A that has passed through the hologram.
~7C and the first-order diffracted light 6 diffracted by the interference fringes 4
It is branched into A to 6C.

Note that even if laser beams, which are strictly spherical waves, are used as the reproduction lights 5A to 5C, the spot diameter of the reproduction light on the hologram surface is as small as approximately 2 [mm], so if the distance between the light source and the hologram is, for example,
At around 160 [mm], the divergence angle of this reproduced light is extremely small, so it can be regarded as a plane wave.

The first embodiment described below is an example in which a hologram created as described above is used as an original, and copying is performed using the zero-order light during reproduction.

As shown in FIG. 2, a hologram recording material plate 12 having a hologram recording material (photosensitive emulsion film) 1 on a glass substrate 11 is irradiated with two created waves having different wavefronts as described above, a spherical wave 2 and a plane wave 3. do. In this way, as shown in FIG.
Due to the interference, interference fringes 4 are formed on the bisector of the intersection angle α between the two.

Using the thus obtained hologram 13 as the original plate,
Copying is performed as shown in FIG. That is, the hologram original plate 13 and a new hologram recording material plate 14 are superimposed with the respective hologram recording materials 1 and 15 facing each other, and the hologram original plate 13 is exposed to copy light 16 (in this case, Irradiate with parallel light).

Then, as shown in FIG. 5, the copy light 16 is split into a first-order diffracted light 17 that is diffracted by the interference fringes of the hologram master (not shown in the figure) and a zero-order light 18 that has passed through the hologram master. , interference fringes 19 are formed on the bisector of the intersecting angle between the two, and a copy of the original hologram 13 is obtained.

The interference fringes of the hologram replica according to this example obtained as described above have the same two-dimensional distribution as the interference fringes of the hologram master, and the inclination in the thickness direction is blurred with respect to the desired reproduction light. Satisfies the conditions. Therefore, not only the aberration during reproduction is extremely small, but also the light utilization efficiency during reproduction is high and uniform over the entire hologram.

Next, as a second embodiment of the present invention, an example will be described in which the first-order diffracted light shown in FIG. 1 is used as copying light.

In this embodiment, as shown in FIG. 6, the convergent spherical wave 2
0 (corresponding to the first-order diffracted lights 6A to 6C in FIG. 1)
The above-mentioned first
By carrying out the same procedure as in the example, the 0th order light 2
Interference fringes 23 between the first-order diffracted light 22 and the first-order diffracted light 22 are formed,
A duplicate is created.

According to this embodiment, a hologram similar to that of the first embodiment can be obtained, and therefore the effects are also the same.

(f) Effects of the Invention As explained above, according to the present invention, it is possible to independently control the two-dimensional distribution of interference fringes of a hologram and the inclination in the thickness direction, and to control the two-dimensional distribution of interference fringes of a hologram and the inclination in the thickness direction thereof. Aberrations are small, and the utilization efficiency of reproduction light can be uniformly controlled to a desired value.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part for explaining the hologram creation method according to the present invention in relation to reproduction light, and FIGS. 2 to 5 are cross-sectional views of main parts showing a first embodiment of the present invention. , FIG. 6 is a sectional view of a main part showing a second embodiment of the present invention. In the figure, 1 and 15 are hologram recording materials;
2 and 3 are the hologram creation lights, 2 is a spherical wave,
3 is a plane wave, 4 is an interference fringe, 5A, 5B, 5C is a reproduction beam, 6A, 6B, 6C, 17, 22 is a first-order diffraction beam, 7A, 7B, 7C, 18, 21 is a zero-order beam, 1
2 and 14 are hologram recording material plates, 13 is a hologram original plate, and 16 and 20 are copy lights.

Claims (1)

[Scope of Claims] 1. A hologram in which two light beams having first and second wavefronts are created as a created wave, and a light beam having a third wavefront different from the two light beams is used as a reproduced incident wave or a reproduced output wave. A method for creating a hologram, wherein a first hologram created by interference of the two created waves is superimposed on a second hologram recording material different from the first hologram, and then copying light is applied to the first hologram. By irradiating a light beam having the third wavefront as described above, the two-dimensional distribution of interference fringes created on the first hologram is transferred to the second hologram recording material, and the second hologram recording material is A method for creating a hologram, characterized in that the transferred interference fringes in the material are created so that the inclination in the thickness direction thereof is different from the inclination in the thickness direction of the interference fringes in the first hologram.