JPH0555848B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a hologram scanner that diffracts and scans laser light using a hologram and simultaneously focuses signal scattered light from an object to be read using the same hologram. be.

Background of the Technology Recently, barcode reading devices that read barcodes printed on the exterior of products and input them into computers have come into use in order to save labor at registers in supermarkets and the like. A hologram scanner that converges and scans laser light using a hologram as both a light focusing element and an optical deflection element is suitable for this device, so a hologram scanner is used as the light scanning unit in a barcode reading device. There is.

Prior Art and Problems Fig. 1 is a diagram for explaining the basic configuration of a barcode reading device, and in the figure, 1 is an outer casing;
2 is a He-Ne laser as a light source, 3 is a beam expander, 4 is a hologram disk with multiple holograms, 5 is its drive motor, 6 is a window opened in the operation surface of the housing, 7 is a scanning light , 8 is a signal light, 9 is a perforated mirror for separating the scanning light and the signal light, 10 is a condenser lens, 11 is a photodetector, 1
2 each shows a barcode printed on the exterior of the product. The operation of this device is as follows:
The passing light is converged and deflected by the hologram disk 4 to scan the barcode 12 on the product. The signal light 8 modulated by the barcode 12 is converged again by the hologram disk 4 and reflected by the perforated mirror 9, and then passes through the lens 10 and the photodetector 11.
It is starting to be detected in

Conventionally, in such a hologram scanner, the hologram is created by interfering a reference wave 13 and an object wave 14 as shown in FIG. Both scanning and condensing of signal light were performed by the same hologram. In this method, as shown in Fig. 1, the signal condensed light 8' travels in the same direction as the incident beam 7' but in the opposite direction, and is It is necessary to separate the incident beam 7' and the condensed light 8', which imposes restrictions on the configurations of the incident optical system and the condensing optical system, which has the drawback of hindering miniaturization of the device. Another disadvantage is that a light separation element such as a perforated mirror is essential, which is undesirable in terms of cost.

Purpose of the Invention In view of the above-mentioned conventional drawbacks, the present invention provides a hologram scanner that easily separates an incident beam and a condensed light without using an optical separation element, thereby reducing the size and cost of the device. The purpose is to provide

Structure of the Invention According to the present invention, in a hologram scanner of a type in which scanning of a laser beam and condensation of reflected light from a scanned object to be read are performed using the same hologram, the hologram is configured to: This is achieved by providing a hologram scanner whose scanning area and focusing area are created using different reference waves.

Embodiments of the Invention Examples of the present invention will be described in detail below with reference to the drawings.
FIG. 3 is a diagram for explaining the hologram scanner according to the present invention. In the figure, 20 is a laser light source, 21 is a beam expander, 22 is an incident beam, 23 is a hologram disk, 24 is a hologram, 25 is a scanning area thereof, 26 is a focusing area,
27 is a scanning light, 28 is an object to be read, 29 is a signal light, 30 is a condensed light, 31 is a lens, and 32 is a photodetector.

As shown in the figure, in this embodiment, an incident beam 22 (convergent spherical wave) passes through a scanning area 25 of a hologram 24 and converges at a point P on the central axis of the hologram disk.
A laser light source 20 and a beam expander 21 are arranged obliquely with respect to the central axis of the hologram disk 23 so as to emit signal light 29 reflected from the object to be read 28 into a condensing area 26 of the hologram 24.
A lens 31 that guides the condensed light 30 and a photodetector 32 are arranged parallel to the central axis of the hologram disk. The hologram 24 used has a scanning area 25 and a focusing area 26 created using different reference waves.

FIG. 4 is a diagram for explaining the method for creating a hologram according to the present invention, in which a shows an optical system for creating a condensing region, and FIG. 4 shows an optical system for creating a scanning region. In the figure, 24 represents a hologram, 25 represents a scanning area, and 26 represents a condensing area. In this production method, first mask the film so that the scanning area 25 is not exposed as shown in figure a, and then use a spherical wave as the object wave 33 and a vertical plane wave as the reference wave 34 to expose, develop, and focus the light. A hologram of area 26 is created. Next, as shown in figure b, the condensing area 2
6 is masked, and the same spherical wave as in figure a is used as the object wave 33, and the reference wave is a spherical wave 35 that has a divergence point at point P on the hologram disk rotation axis, unlike in figure a.
A hologram of the scanning area 25 is created using this method.

The hologram created in this way is produced by irradiating the scanning area 25 with a spherical wave 36 focused on a point P on the disk rotation axis and the converging area 26 with a vertical plane wave 37, both areas are illuminated. Since the same spherical wave is used as the object wave, the reproduced light converges on the same point P'. Furthermore, even if the disk rotates, the reference wavefronts do not change during creation and regeneration in both regions, so they still converge to the same point. This means that when reflected light from a scanned object is received by the condensing region 26, it is always converted into a vertical plane wave, and has the conventional re-imaging function.

When copying such a hologram, as shown in FIG.
26 may be used as copy light 38 to copy onto a recording medium 39.

Effects of the Invention As described above in detail, the hologram scanner of the present invention uses a hologram in which the scanning area and the focusing area are created using different reference waves, thereby incorporating a light separation element such as a perforated mirror. This makes it possible to separate the incident beam and the condensed light without using it, and has the great effect of making the device smaller and cheaper.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the basic configuration of a conventional barcode reading device, FIG. 2 is a diagram for explaining a conventional hologram, and FIG. 3 is a diagram for explaining a hologram scanner according to the present invention. , FIG. 4 is a diagram for explaining the method for creating a hologram according to the present invention, FIG. 5 is an explanatory diagram for creating a hologram created by the above-mentioned method, and FIG. 6 is a diagram for explaining a method for copying a hologram. It is. In the drawing, 20 is a laser light source, 21 is a beam expander, 22 is an incident beam, 23 is a hologram disk, 24 is a hologram, 25 is a scanning area, 26 is a condensing area, 27 is a scanning light, 28 is an object to be read, 29 is a signal light, 30 is a condensed light, 31 is a lens, and 32 is a photodetector.

Claims (1)

[Claims] 1. In a hologram scanner that uses the same hologram to scan a laser beam and collect reflected light from a scanned object to be read, the hologram uses a reference wave whose scanning area and focusing area are different. A hologram scanner characterized in that it is created using.