JPS6344816Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a hologram scanner used for reading barcodes in POS (point of sale) systems and the like.

Conventionally, there has been a device of this type as shown in FIG. In this figure, 1 is an incident beam with point O as a point light source, 2 is a perforated mirror having an aperture through which the incident beam 1 passes, 3 is a hologram lens, and 4 is an amount corresponding to the scanning line pitch to be generated. , a hologram disk in which a number of hologram lenses 3 whose centers are displaced are arranged in a number equal to the number of scanning lines; 5 is a scanning beam deflected by the hologram lens 3; 6 is a scanning surface; 7 is a scanning pattern;
Reference numeral 8 denotes scattered light scattered by a bar code or the like provided on the label, 9 a photodetector, and 10 a motor for rotating the hologram disk 4.

Next, the operation will be explained.

Laser light emitted from a laser oscillator (not shown) is converted into an incident beam 1 with point O as a point light source. The incident beam 1 passes through the aperture of the perforated mirror 2 and enters the hologram lens 3 . The incident beam 1 is then diffracted and focused by the hologram lens 3 to become a scanning beam 5, which forms a light spot at a point P on the scanning surface 6. In this state, the hologram disk 4 is rotated by the motor 10. As a result, the scanning beam 5 is shifted and deflected in the radial direction of the hologram disk 4 in accordance with the displacement of the center of each hologram lens 3, and the light spot on the scanning surface 6 follows a trajectory like the scanning pattern 7. draw. Scattered light 8 scattered by the barcode of the label placed on the scanning surface 6 follows a path opposite to that of the scanning beam 5 and enters the perforated mirror 2 .
The scattered light 8 reflected here is focused on a photodetector 9 and converted into an electrical signal. The barcode information is read by the above steps.

Since the conventional hologram scanner is configured as described above, when the incident beam 1 is incident on the hologram lens 3, the hologram lens 3
acts as a transmission type diffraction grating to generate the scanning beam 5, and at the same time acts as a reflection type diffraction grating to generate unnecessary diffracted light, that is, harmful light. This harmful light is reflected by the perforated mirror 2 and enters the photodetector 9, which has the drawback of causing noise.

This invention was made to eliminate the above-mentioned drawbacks of the conventional scanner, and aims to provide a hologram scanner that can remove harmful light by utilizing the polarization characteristics of laser light.
This idea will be explained below.

FIG. 2 is a sectional view showing an embodiment of this invention. In this figure, numerals 1 to 10 indicate the same or equivalent parts as in FIG. This is a linear polarizing plate inserted between the mirror 2 and the photodetector 9. Furthermore, the incident beam 1 is assumed to be a laser beam having a polarization direction perpendicular to the plane of the paper.

Next, the operation will be explained.

A laser beam emitted from a linearly polarized laser oscillator (not shown) is converted into an incident beam 1 having a polarization direction perpendicular to the plane of the paper and having a point O as a point light source. The incident beam 1 enters the hologram lens 3 through the aperture of the perforated mirror 2 . The hologram lens 3 functions as a transmission type diffraction grating and generates a scanning beam 5, and also functions as a reflection type diffraction grating and generates harmful light 11. Next, when the hologram disk 4 is rotated by the motor 10, the scanning beam 5 generates a scanning pattern 7 on the scanning surface 6, as in the conventional case. At this time, the polarization directions of the scanning beam 5 and the harmful light 11 are maintained perpendicular to the plane of the paper. On the other hand, the polarization direction of the scattered light 8 scattered by the label on the scanning surface 6 is not preserved and is random. Therefore, the scattered light 8 is reflected by the perforated mirror 2 and is reflected by the linear polarizing plate 12.
The light passes through and is focused on the photodetector 9. but,
Since the polarization direction of the harmful light 11 is preserved, it is blocked by the linear polarizing plate 12 whose polarization direction is within the plane of the drawing. As a result of the above, the harmful light 11 does not enter the photodetector 9.

In the above embodiment, the polarization direction of the incident beam 1 is perpendicular to the plane of the paper and the polarization direction of the linear polarizing plate 12 is within the plane of the paper, but the polarization directions of the incident beam 1 and the linear polarizing plate 12 are
May be rotated 90°.

As explained above, this invention has a structure in which a linear polarizing plate is inserted between a perforated mirror and a photodetector, so harmful light generated from the hologram disk can be removed and the electrical signal S/N can be improved. In addition, there is an effect that the amplifier system of the photodetector can be simplified.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional hologram scanner, and FIG. 2 is a sectional view of a hologram scanner according to an embodiment of the invention. In the figure, 1 is the incident beam, 2 is the perforated mirror, and 3
is a hologram lens, 4 is a hologram disk,
5 is a scanning beam, 6 is a scanning surface, 7 is a scanning pattern, 8 is a scattered light, 9 is a photodetector, 10 is a motor,
11 is harmful light, and 12 is a linear polarizing plate. In addition,
The same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] A hologram scanner that deflects and condenses a light beam to create a light spot and scans it on a scanning surface includes a laser light source that emits a linearly polarized light beam, and a laser light source that receives scattered light scattered from the scanning surface. a photodetector for converting the scattered light into an electrical signal; a plane mirror for making the scattered light incident on the photodetector; and a plane mirror and the photodetector so that the polarization direction is orthogonal to the polarization direction of the light beam. A hologram scanner characterized by comprising a linear polarizing plate inserted between.