JPS60254111A - Hologram scanner - Google Patents

Abstract

PURPOSE:To improve light utilization efficiency by arranging a body to be read at the side oppsite to an irradiated surface about an axis of rotation so that scanning laser light emitted from a hologram is directed to the inside of a hologram disk, and increasing an angle of diffraction. CONSTITUTION:A detector 10 is provided onto the axis ax of rotation of the hologram disk 12. Incident laser light 5 from a light source which is not shown in a figure is reflected by a mirror 4 to illuminate and pass through the hologram disk 12, and diffracted scanning light 6 passes over the axis ax of the hologram disk 12 to irradiate the body 2 to be read arranged at the opposite side of the axis. Signal scattered light 7 reflected by a body 2 reaches the hologram disk surface 12a and is diffracted to strike the detector 10 as a convergent spherical wave 11. Consequently, the angle theta of diffraction is increased and a reliable read superior in light utilization efficiency is made by the simple device. The device is used suitably to read bar codes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a hologram scanner that uses a hologram disk to scan an object to be read with a laser beam, and collects and detects the reflected light.

[Prior art and its problems]

When the hologram is moved, it acts as a lens, and the -order diffracted light is deflected to draw a single scanning line. Applying this effect,
By placing a plurality of holograms on a disk and rotating it, various scanning patterns can be obtained.

This scanning principle is used as a barcode reader in POS systems. This hologram scanner has advantages over conventional devices using rotating polygon mirrors, such as a simple configuration, light weight, simple optical system, and low cost.

FIG. 3 is a side view of a hologram scanner using a laser diode as a light source. 1 is a hologram disk; 2 is an object to be read such as a bar code; and 3 is a motor for rotating the hologram disk 1. A plurality of holograms are arranged on the hologram disk 1 in the circumferential direction,
This hologram position (1a) is irradiated with a laser beam 5 reflected by a mirror 4, and the hologram disk 1 is continuously rotated by a motor 3. Then, due to the interference fringes of the hologram, it becomes a scanning beam 6 with a diffraction angle θ, which converges on and scans the object 2 to be read, such as a Parcode. The reflected signal scattered light 7 then reaches the irradiation surface la of the hologram disk 1, is diffracted toward the lower surface of the hologram disk 1, and becomes a plane wave 8. This plane wave 8 is imaged onto a detector 10 by a lens 9, and a barcode is read. A hologram in which the diffracted light is a plane wave as described above can be obtained by irradiating a diverging spherical wave and a plane wave in a layered manner using a known method to create interference fringes.

However, in order to spread the use of hologram scanners, it is necessary to further reduce costs and make them more compact, and for this purpose, it is necessary to further reduce the number of parts and simplify the configuration. In response to such demands, a configuration as shown in FIG. 4 has been attempted as a device that does not require the lens 9. In this hologram disk, when the signal scattered light 7 reflected by scanning a barcode passes through the hologram disk 1 and is diffracted, it becomes a convergent spherical wave 11 and is centered around the rotation axis ax.
An image is formed above and read by a detector 10 disposed on the rotation axis ax. So-called self-focus becomes possible,
No condensing lens is required. A hologram like this, which can focus light on the rotation axis ax without using a lens, has a divergent spherical wave A and a convergent spherical wave B, as shown in Figure 4 (b).
It is obtained by overlapping irradiation to create interference fringes. At this time, the creation light is irradiated so that the convergent spherical wave B converges on the rotation axis ax.

In this way, the signal scattered light can be focused on a single point without using a lens, which is excellent in terms of reducing the number of parts and realizing a simpler and more compact structure.

In the case of FIG. 3, as is clear from the figure, both the diffraction angle θ of the incident beam 5 and the diffraction angle of the output light 8 resulting from the diffraction of the signal scattered light 7 are large. In other words, the hologram's interference fringes have a fine pitch and a high spatial frequency, so the light usage efficiency is high.

On the other hand, in the configuration shown in FIG. 4(a), both the scanning beam 6 after passing through the hologram and the output signal light 11 have small diffraction angles. In other words, the pitch of the interference fringes of the hologram is coarse and the spatial frequency is low, so the light usage efficiency is low. If the light usage efficiency is low, the amount of light that can be detected by the detector 10 as a signal relative to the incident laser light is small, making it difficult to perform reliable readings, and although the lens is no longer necessary, the characteristics This will result in a decline.

[Technical problem of the present invention]

A technical object of the present invention is to eliminate such problems in conventional hologram scanners, and to reduce the number of parts, simplify the structure, and make it more compact without reducing the light usage efficiency.

[Technical means of invention]

The technical means of the present invention taken to solve this technical problem scans the laser beam by rotating a hologram disk and diffracting the light beam, and collects the signal scattered light from the scanned object to be read. A self-focusing hologram scanner that focuses light on the same hologram and forms an image on a detector without using an auxiliary focusing optical element such as a lens, and the scanning laser beam emitted from the hologram is The object to be read is placed on the opposite side of the hologram disk's irradiation surface with respect to the rotation axis so that it is oriented inward (toward the rotation axis), and the detector is placed on the rotation axis. ing.

[Effect of technical means]

According to this technical means, the object to be read is disposed on the opposite side of the irradiation surface of the hologram disk with respect to the rotation axis of the hologram disk, and the detector is disposed on the rotation axis. Then, the reproduction light is made to enter the irradiation surface from the optical axis of the signal light that converges on the detector from the irradiation surface of the hologram disk. Therefore, the scanning laser beam that has entered the irradiation surface and passed through the irradiation surface of the hologram disk passes on the rotation axis of the hologram disk, reaches the object to be read at the opposite position, and scans it. The signal scattered light reflected on the irradiation surface is convergently diffracted and detected by a detector on the rotation axis on the same irradiation surface.

Since the detector is thus disposed on the rotational axis of the hologram disk, an image can be formed on the detector without a lens. In addition, the detector is placed on the rotation axis, and the object to be read is placed beyond the rotation axis on the opposite side of the rotation axis to the irradiation surface, so that the diffraction angle of the laser light is It becomes larger and the efficiency of first use is greatly improved.

[Embodiments of the invention]

Next, examples will be used to explain how the hologram scanner according to the present invention is actually implemented.

FIG. 1 is a side view of an embodiment of a hologram scanner according to the invention. 12 is a hologram disk, and the detector 10 is connected to the hologram disk 12 as in the case of FIG.
It is arranged on the rotation axis ax of.

The object to be read 2 is disposed so that the scanning laser beam is guided to a position beyond the rotation axis ax from the irradiation surface 12a of the hologram disk, completely contrary to the conventional apparatus. Therefore, the scanning light 6 obtained by diffracting the incident light 5 through the hologram disk 12 passes on the rotation axis aX of the hologram disk 12, reaches the object to be read 2, and scans it. In other words, in the conventional device, the scanning light emitted from the irradiation surface is directly emitted toward the outside of the hologram disk and reaches the object to be read, but in the present invention, the scanning light is conversely directed toward the rotation axis side (inside) of the hologram disk. The beam is emitted, passes over the rotation axis, and reaches the object to be read.

As a result, the signal scattered light 7 reflected by the object 2 to be read also
The light passes over the rotation axis ax and is reflected back to the original irradiation surface 12a. The diffracted convergent spherical wave signal light 11 forms an image on a detector 10 on the rotation axis and is read.

In this way, in the present invention, the object to be read 2 also has the irradiation surface 12.
The diffraction angle θ at the irradiation surface 12a is extremely large because it is disposed on the rotation axis ax side with respect to a, like the detector 10. In order to create a hologram with such diffraction characteristics, as shown in FIG. are irradiated in layers to create interference fringes. The plurality of hologram pieces created in this way are arranged in the circumferential direction on a disk. Of course, directly on one piece of hologram material,
It is also possible to create holograms in the circumferential direction using the method shown in FIG.

A hologram with such a large diffraction angle has a dense pitch of interference fringes, a high spatial frequency, and a high first use efficiency.
By effectively guiding the incident laser beam to the object to be read and also guiding it to the detector, highly reliable reading can be performed. Further, since the detector 1o is arranged on the rotation axis ax of the bologram disk 12, self-focusing can be realized without aberrations.

[Effects of the Invention] As described above, according to the present invention, the object to be read is disposed on the side opposite to the irradiation surface with respect to the rotation axis of the hologram disk, and the scanning light is directed toward the rotation axis. , passing over the rotation axis to reach the object to be read. Therefore, it is possible to increase the diffraction angle of the hologram and perform highly reliable reading with excellent first-use efficiency. In addition, self-focusing that does not require a lens can be realized without aberrations, and an inexpensive device can be obtained that achieves a simpler and smaller hologram scanner configuration, a reduced number of parts, and a lighter weight.

[Brief explanation of the drawing]

FIG. 1 is a side view showing an embodiment of a hologram scanner according to the present invention, FIG. 2 is a side view showing a method for creating a hologram disk in the hologram scanner, FIG. 3 is a side view of a conventional hologram scanner, and FIG. 1 is a side view of a conventional self-focusing hologram scanner and a side view showing a method of creating a hologram therefor. In the figure, 1 and I2 are hologram disks, la. 12a is an irradiation surface, 2 is an object to be read, 4 is a mirror, 5 is an incident laser beam, 6 is a scanning laser beam, 7 is a signal scattered light, 1
0 indicates a detector, and 11 indicates an output signal light. Patent Applicant Fujitsu Limited Representative Patent Attorney Minoru Aoyagi Figure 3 Figure 4 (A) (Rof

Claims (1)

[Claims] The laser beam is scanned by rotating the hologram disk and diffracting the light beam, and the signal scattered light from the scanned object to be read is focused on the same hologram, and further using an auxiliary focusing optical element such as a lens. This is a self-focus type hologram scanner that forms an image on a detector without moving, and the object to be read is rotated so that the scanning laser beam emitted from the hologram is directed inside the hologram disk (toward the rotation axis). A hologram scanner characterized in that the hologram scanner is disposed on the opposite side of the irradiation surface of the hologram disk with respect to the axis, and the detector is disposed on the rotation axis.