JPS6324480A - Stationary type hologram scanner - Google Patents

Abstract

PURPOSE:To improve the reading accuracy of a bar code by providing a through-hole in the light beam transmission part of a prism mirror and passing one of the light beams time divided into three stages. CONSTITUTION:The light beam 2 outgoing from a laser oscillator is time divided into the light beams 2a, 2b, 2c by a beam splitter 4. The light beam 2a reflected in the beam splitter 4a is reflected by the reflecting surface 21a of the prism mirror 21, polarized by a hologram disk 7, converged to an O3 point and made incident on the bar code. Then, the light beam 2b reflected by the beam splitter 4b passes the hole part 21b disposed in the prism mirror 21 to reach the hologram disk 7, and is polarized and converged. Accordingly, the light beam is made incident on the hologram disk through air without transmitting different medium, so that a converging point is not deviated, but converged at the O3 point similarly to the light beam 2a and made incident on the bar code. The light beams 2c is converged to the O3 point in the similar path to the light beam 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stationary hologram scanner that reads barcodes printed on products at registers in supermarkets and the like.

It is a principle diagram showing a conventional stationary hologram scanner,
In the figure, 1 is a laser oscillator, 2 is a light beam emitted from this laser oscillator 1, 3 is a lens that focuses this light beam 2, 4 is a beam splitter that time-divides the light beam 2, and 5 is a beam splitter that A prism mirror that distributes the divided light beam 2 in multiple directions, 6 a mirror that reflects the divided light beam 2, 7 a hologram disk, 8 a motor, 9 a mirror, 10 a reading window, and 11 a scanning device. 12a is a part of the scattered light reflected from the barcode (not shown), 12b is a part of the scattered light collected by the hologram lens 7, 13 is a perforated mirror, and 14 is the scattered light 12b This is a photoelectric conversion device that receives light and converts it into an electrical signal.

Next, the operation will be explained. A light beam 2 emitted from a laser oscillator 1 passes through a lens 3 and heads toward a beam splinter 4, where it is time-divided into three stages. These time-divided light beams 2 are reflected by the mirror of the prism mirror 5 or transmitted through the prism, then reflected by the mirror 6, passed through the aperture 13a of the perforated mirror 13, and are directed to the hologram disk 7. The light enters the hologram lens above. The light beam 2 diffracted by the hologram lens is reflected by the mirror 9 and focused on the reading window 10.
It hits a barcode that passes over 0 and is scattered. Scattered light 12a (however, originally, scattered light is generated along the same number of optical axes as the number of light beams 2 diffracted by the hologram lens, but only the scattered light 12a is shown because the diagram would be complicated. ) The light beam follows a path opposite to that of the light beam 2, enters the hologram lens, is reflected by the perforated mirror 13, is focused on the photoelectric conversion device 14, and is converted into an electrical signal.

Next, the distribution and focusing of the light beam is performed in the fourth step. This will be explained based on FIG. FIG. 4 is a principle diagram showing the distribution of a conventional light beam, and FIG. 5 is a principle diagram of the optical system of a conventional hologram scanner. In the figure, a light beam 2 passes through a lens 3 and is focused on a point 01.

Next, when the beam splitter 4 is rotated by the motor 4d, the light beam 2 is rotated by the mirror 4a depending on the speed.
, is reflected by each stage of mirrors, sometimes mirror 4b, sometimes mirror 4c, and three stages of reflected beams 2a,
It is time-divided into 2b and 2c. These reflected beams 2a, 2b, and 2c are incident on mirror 5a, prism surface 5b, and mirror 5c of prism mirror 5, respectively. Then, the light beams 2a and 2c are mirrored by mirrors 5a and 5.
The light beam 2b is reflected by the prism and travels in the directions of arrows A, B, and C, respectively. Of the light beams 2 thus distributed, the light beams 2a and 2c are first reflected by the prism mirror 5 and then polarized onto the hologram disk 7, so that the light beams 2a become the light beams 2a.

The focal point after passing through the hologram disc of 2C is a point 0 that satisfies L2 = 1/ (1/f-1/Lt) from the formula for the focal point of a convex lens, where f is the focal length of the hologram disc 7.
It becomes 3. - The tip beam 2b is not reflected by the prism mirror 5, but passes through a prism whose medium is different from that in the air, so the apparent focal point is from 01 to 02
move forward to

Therefore, the focal point of the light beam 2b after polarization by the hologram disk 7 is a point 04 that satisfies 52=1/(1/f-1/St). As a result, a difference in focal length of Δ5=52−L2 occurs between the light beams 2a and 2c reflected by the prism mirror and the light beam 2b transmitted through the prism mirror.

Although the hologram disk 7 is depicted in three places in FIG. 4, in reality, it is reflected by three mirrors 13 as shown in FIG. 3, so there is only one hologram disk 7. be.

[Problem that the invention seeks to solve]

Conventional stationary hologram scanners are configured as described above, so the light beam that has passed through the prism mirror has a longer focal point distance from the hologram disk than the other two light beams, making it difficult to read. There was a problem in that the spot diameter on the window could not be narrowed down sufficiently, and as a result, the spot diameter was larger than the minimum barcode diameter, resulting in poor barcode reading accuracy.

This invention was made to solve the above problems, and it provides a stationary hologram scanner that can sufficiently narrow the spot diameter of the three light beams on the reading window and has high barcode reading accuracy. The purpose is to obtain.

[Means for solving problems]

In the stationary hologram scanner according to the present invention, a through hole is formed in the light beam transmission part of the prism mirror that distributes the time-divided light beam in three directions, and one of the light beams passes through this hole. This allows it to pass through the air like the other two tubes.

[Effect]

In this invention, one of the three time-divided light beams passes through a snow hole provided in the light beam transmission part of the prism mirror, so that this light beam enters a medium different from air. The focal point distance from the hologram disk is the same as that of the other two light beams.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 2 is a light beam emitted from a laser oscillation '15 (not shown), 3 is a convex lens, 4 is a beam splitter that time-divides the light beam 2, and 21 is a light beam 2 split by this beam splitter 4. 21a and 21c are reflective surfaces, and 21b is a hole through which the light beam passes. Furthermore, 7 is a hologram disk on which the light beam 2 is incident (three hologram disks are shown in the figure, but this is to show the principle of the leaf tip; in reality, there is only one hologram disk). be.

Next, the operation will be explained. A light beam 2 emitted from a laser oscillator is time-divided into light beams 2a, 2b, and 2C by a beam splinter 4 as in the prior art. First, the light beam 2a reflected at the beam splinter 4a
is reflected by the reflective surface 21a of the prism mirror 21, polarized by the hologram disk 7, focused at the 03 point, and reflected by the 0-order beam splinter 4b, which enters the barcode (not shown). The light passes through the hole 21b provided in the mirror 21 and reaches the hologram disk 7, where it is polarized and focused. Therefore, the light beam does not pass through a different medium (it passes through the air and enters the holographic disk 9), so the light beam is focused at point 03 in the same way as the light beam 2a without shifting the focus point, and is incident on the barcode. The light beam 2C is focused at point 03 along the same path as the light beam 2a.

In the above embodiment, the prism mirror is integrally molded with a hole, but as shown in FIG. It is also possible to create an integral structure by gluing or fixing with metal fittings, etc.

〔Effect of the invention〕

As described above, according to the present invention, a through hole is provided in the light beam transmitting part of the prism mirror, and one of the light beams divided in three stages passes through the hole, so that this light beam cannot pass through a medium different from air (,
The distance of the focal point from the hologram disk is equal to that of the other two beams, thereby making it possible to sufficiently narrow down the spot diameters of the three light beams on the reading window.
This has the effect of providing a stationary hologram scanner with high accuracy in reading barcodes and the like.

[Brief explanation of drawings]

FIG. 1 is a principle diagram showing light beam distribution according to an embodiment of the invention, FIG. 2 is a perspective view of a prism mirror showing another embodiment of the invention, and FIG. 3 is a principle diagram of a hologram scanner device. Figure 4 is a principle diagram showing conventional light beam distribution, and Figure 5
The figure is a principle diagram showing the position of the leaf tip of a conventional light beam. 2 is a light beam, 4 is a beam splitter, 21 is a prism mirror, and 21b is a hole for passing the light beam. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a stationary hologram scanner that reads information on an object using a light beam, two of the above light beams are time-divided into three stages by a beam splitter and reflected into the air by the reflecting surface, and the other A stationary hologram scanner comprising a prism mirror that allows one of the prisms to pass through the through hole.