JPS631330Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a hologram creation device suitable for optical scanning, and aims to create each hologram piece under the best and the same conditions.

[Conventional technology]

To create a hologram used for optical scanning when reading barcodes etc. printed on product labels, as shown in Figure 1, a plane wave 2 is irradiated from the front as a reference wave onto the hologram recording surface 1. death,
By irradiating the spherical wave 3 as an object wave from an oblique direction, the two lights interfere on the recording surface to form interference fringes, which are developed to form a hologram. 4
is a point light source for generating spherical waves. Hologram pieces are cut out like A, B, and C from the interference fringe forming area and arranged like A, B, and C in FIG. 2 to form an optical scanning device. Then, by irradiating the laser beam 5 from one side while moving the hologram pieces A, B, and C in the arrangement direction,
Scanning light by reproducing spherical waves such as a, b, and c is obtained on the scanning surface to scan the barcode on the product label. In reality, a large number of hologram pieces are arranged in A, B, C, etc. in the circumferential direction of a rotating disk, and a large number of scanning lights are obtained by rotating the disk.

However, when creating a hologram, the center hologram piece B cut out from the optical axis position of the plane wave 2 and the spherical wave 3 is the best one, but the hologram pieces A and C away from the optical axis position are Since the intensity of the irradiated light is different from that of B, the reproducing effect is reduced. For example, for reproduction scanning, the first-order light diffracted by the hologram is used, but in reality, in addition to the first-order light, the zero light that travels straight through the hologram is used.
Secondary light is generated, which becomes noise and worsens the S/N ratio when reading barcodes.

Therefore, the applicant of the present invention previously proposed
In Publication No. 84758, a method was proposed in which the spherical wave light source was also moved. FIG. 3 is a perspective view showing the outline thereof. In this method, when creating holograms with different diffraction directions, the position of the spherical wave point light source 4 is changed as A', B', and C' for each hologram. That is, like the hologram piece B in the center of FIG.
For this purpose, the optical axis of the plane wave 2 and the optical axis of the spherical wave 3 are always made to intersect on the hologram recording surface 1, and under this condition,
Move the position of the spherical wave point light source as A', B', and C'. Then, the holograms created by irradiating spherical waves from point A', and the holograms created by irradiating spherical waves from points B' and C' are arranged as shown in FIG. 2 to form an optical scanning device.

If holograms are created using this method, all holograms will be created at the central position that includes the optical axis intersection O of the plane wave and spherical wave irradiation surfaces.
All holograms are homogeneous with no variation between holograms, and they are created at the most favorable position where there is less harmful light during optical scanning. In addition, since it is sufficient to create one hologram in each interference fringe formation process, the diameter of the collimator is smaller compared to the case where multiple holograms are created at the same time as shown in Figure 1, and the lens for generating spherical waves is A device with a large F number can be used, reducing the cost of the device.

[Problem that the invention attempts to solve]

By the way, in order to obtain a point light source for spherical waves, the laser beam is expanded into a large-diameter parallel light beam using a collimator, and then converged to a single point using a convex lens to form a point light source. If it is moved like B' and C', the optical path length from the laser light source to each point light source will change, and the hologram creation conditions will differ.

The technical problem of the present invention is to solve these problems in conventional hologram creation devices and to realize a device that can create holograms without changing the optical path length even if the spherical wave point light source moves. It is in.

[Means for solving problems]

The technical means according to the present invention taken to solve this technical problem is as shown in FIG. A first collimator 8 that converts the reflected light from the beam into a large-diameter parallel beam bundle.
and a mirror or prism M4 that irradiates the hologram recording surface 1 with the parallel light beam from the first collimator 8.

In addition, in order to form a spherical wave in which the point light source can move, a second collimator 9 converts the light passing through the beam splitter 7 into a large-diameter parallel beam bundle; It has mirrors or prisms M6 and M7 that change the direction of the mirror by 180 degrees (combination). Also, the mirror or prism M
6. A spherical wave lens 11 that focuses a light beam whose direction has been reversed by 180 degrees at M7, and a spherical wave lens 11 that is installed on the output side of the spherical wave lens 11, and that focuses the light beam that has been focused by the spherical wave lens 11. It has a spherical wave deflection mirror or prism M8 that irradiates the hologram recording surface 1 with the parallel light beam from the collimator 8.

The combination mirror mentioned above is also a prism M.
6, M7, the spherical wave lens 11 and the spherical wave deflection mirror or prism M8 maintain the relative positions so as to keep the optical path length of the spherical wave light beam constant, and the parallel beams emitted from the second collimator 9. It is mounted on a mechanism that allows linear movement in the 10 directions of the light beam or in orthogonal directions.

In addition, the spherical wave deflecting mirror or prism M
8 is a spherical wave forming lens 11 on the mechanism.
It can be rotated around the optical axis.

Note that the reflected light from the beam splitter 7 may be used as a spherical wave light source, and the transmitted light may be used as a plane wave light source.

[Effect]

Laser light emitted from the laser light source 6 is separated by a beam splitter 7 into reflected light and transmitted light. After the reflected light is collimated by the first collimator 8, it is irradiated onto the hologram recording surface 1 by a mirror or prism M4.

The transmitted light of the beam splitter 7 is collimated by a second collimator 9, and then is reversed by 180 degrees by a combination mirror or prisms M6 and M7.
A spherical wave point light source is formed by the spherical wave forming lens 11, and is irradiated onto the recording surface 1 by a mirror or prism M8.

Furthermore, in order to keep the optical path length constant even if the spherical wave point light source moves, it has a combination mirror or prisms M6 and M7. Even if it moves linearly in a direction perpendicular to , only the path of the collimated light changes, and the overall optical path length does not change. Further, since the mirror or prism M8 for spherical wave polarization rotates around the optical axis of the spherical wave forming lens 11, the optical axis of the spherical wave is always positioned at the optical axis intersection O of the plane wave and the spherical wave.

〔Example〕

Next, how the hologram creation apparatus according to the present invention is actually implemented will be explained using examples. FIG. 4 is a plan view showing an embodiment of the hologram creation apparatus according to the present invention. 6 is a laser light source, and the light emitted from the light source is reflected by a mirror M1, enters a beam splitter 7, and is split into straight light and reflected light. The reflected light from the beam splitter 7 passes through the first collimator 8 via mirrors M2 and M3, and becomes a large-diameter parallel beam bundle, that is, a plane wave 2'. FIG. 5 is a side view of the vicinity of the hologram creation section, and as shown in this figure, the enlarged parallel light beam 2' is reflected by the mirror (or prism) M4.
It is reflected onto the hologram recording surface 1.

The light passing through the beam splitter 7 is reflected by a mirror M5 and expanded into a large-diameter parallel beam bundle 10 by a second collimator 9. This large-diameter parallel light beam is further reflected by mirrors M6 and M7, changes its direction by 180 degrees, and enters the spherical wave generating lens 11. The light is once converged by the spherical wave generation lens 11 to become a point light source for spherical waves, and then expanded again to become a spherical wave 3. This spherical wave 3 is also reflected onto the hologram recording surface 1 by a mirror (or prism) M8 as shown in FIG. At this time, mirrors M4 and M8 are set in the direction where the optical axis of the plane wave 2 and the optical axis of the spherical wave 3 intersect on the hologram recording surface 1, as at point O.

In this device, mirrors M6 and M7 are tilted at 45 degrees with respect to the incident light to each, so as to change the beam direction by 90 degrees, and both mirrors M6 and M7 and a spherical wave generating lens 11
are fixedly installed on the same stage, and move together in the direction of arrow X by the stage. Also, since the spherical wave generating lens 11 moves linearly in the X direction, no matter where the lens 11 is in the X direction, the optical axis of the spherical wave is always at the O point.
Mirror M8 rotates around the optical axis of light passing through lens 11. Therefore, this mirror M8
may also be attached to a stage and moved in the X direction together with the combined mirror or prisms M6 and M7 and the spherical wave forming lens 11. All other optical systems are fixed. In the figure, if a spherical wave is to be irradiated from position A', the stage is moved to the top of the figure and the mirrors M6 and M7 are positioned at position α. Then, the parallel ray 10 passes through both mirrors M
6 and M7, it follows a path as indicated by the chain line, passes through the lens 11, and is reflected toward the intersection point O on the hologram recording surface by the rotation of the mirror M8 at the A' position. Interference fringes are formed by the reflected spherical wave 3 and plane wave 2'.

When irradiating a spherical wave from position B', the stage is returned to the intermediate position and mirrors M6 and M7 are positioned at β. Then, the parallel ray 10 follows the path of the solid line, and due to the rotation of the mirror M8, the spherical wave moves to the intersection point O.
reflected.

Similarly, when irradiating a spherical wave from the C′ position,
Move the stage to the top of the diagram, and mirror M6・M
When point 7 is located at γ, the light follows the optical path indicated by the broken line and reaches point O.

According to this configuration using two mirrors with a reflection angle of 45 degrees, in the range on the right side of the figure from lines A and I', the optical path length of the dashed-dotted line and the optical path length of the solid line are both the same as the optical path length of the solid line. and the optical path lengths indicated by the broken lines are all equal. Therefore, no matter where the spherical wave is irradiated from A', B', or C', the optical path length of the spherical wave light beam is always constant, and the optical path length can be changed by moving the spherical wave point light source. This also eliminates the fear that the hologram creation conditions will differ.

[Effect of idea]

As described above, according to the present invention, the irradiation direction of the spherical wave is changed under the condition that the optical axis of the plane wave and the optical axis of the spherical wave always intersect on the hologram recording surface. When moving the spherical wave light source to cut out from the central portion 1c that includes the intersection of the axis and the spherical wave optical axis, the spherical wave light source can be moved without changing the optical path length. Therefore, the conditions for creating each hologram piece are uniform, making it possible to create holograms with uniform characteristics. In addition, the point light source for spherical waves at each position uses the same laser light source, and the point light source position is
Even if the angle of incidence is changed to A', B', C', etc., the mirror with an incident angle of 45 degrees is M6 or M7, the point light source lens 11, and the mirror or prism that rotates around the optical axis M8.
is attached to a stage that moves linearly in the X direction,
By having a configuration that moves as one, the optical path length can always be maintained constant, and the device configuration is simple, and the exposure amount and R/O during hologram creation can be easily maintained.
The fluctuation of the ratio becomes smaller. Furthermore, since the spherical wave deflection mirror M8 rotates around the optical axis of the lens 11, the optical axis of the spherical wave can always be positioned at point O, no matter where the lens 11 is in the X direction.
A highly accurate hologram creation device can be obtained.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing a conventional hologram creation method, Figure 2 is a perspective view showing an overview of an optical scanning device using a hologram, and Figure 3 is a perspective view showing a hologram creation method previously proposed by the applicant of the present invention. FIG. 4 is a plan view showing an embodiment of the hologram creation apparatus of the present invention, and FIG. 5 is a side view of the hologram creation light irradiation section of the same apparatus. In the figure, 1 is the hologram recording surface, 2, 2'
is a plane wave, 3 is a spherical wave, 4 is a point light source for spherical waves,
A', B', and C' are point light source positions, O is the intersection of the plane wave optical axis and the spherical wave optical axis, 1c is the hologram creation area, 6
is a laser light source, 7 is a beam splitter, and 8 is a first
9 is a second collimator, 11 is a spherical wave forming lens, M4 is a plane wave deflecting mirror or prism, M6 and M7 are combined mirrors or prisms, and M8 is a spherical wave deflecting mirror or prism, respectively.

Claims (1)

[Scope of utility model registration request] In an apparatus for creating holograms with different diffraction directions by irradiating spherical waves from different directions under conditions where a plane wave optical axis and a spherical wave optical axis intersect on a hologram recording surface, a laser light source;
a beam splitter; a first collimator that converts reflected (or transmitted) light from the beam splitter into a large-diameter parallel beam; and a mirror that irradiates the parallel beam from the first collimator onto a hologram recording surface. Or a prism, a second collimator that converts the transmitted (or reflected) light from the beam splitter into a large-diameter parallel beam, and a mirror that changes the direction of the parallel beam from the second collimator by 180 degrees. Alternatively, a prism, a spherical wave lens that focuses the light flux whose direction has changed by 180 degrees from the mirror or prism, and a light flux that is installed on the exit side of the spherical wave lens and is focused by the spherical wave lens, A spherical wave deflecting mirror or prism that irradiates the hologram recording surface with the parallel beam from the first collimator, the above (combination) mirror or prism, a spherical wave lens, and a spherical wave deflecting mirror or prism. a mechanism capable of linear movement in the direction of the parallel light emitted from the second collimator or in the orthogonal direction while maintaining the relative position so that the optical path length of the spherical wave light beam is constant;
A hologram creation apparatus characterized in that the mechanism includes means for rotating the spherical wave deflecting mirror or prism about the optical axis of the spherical wave forming lens.