JPH01304589A - Bar code scanner - Google Patents

Abstract

PURPOSE:To extend the area, where a sufficient resolution required for bar code read is obtained, to read a bar code with a long depth by varying relative positions of a laser diode and a collimator lens on the optical axis at a low frequency speed. CONSTITUTION:The laser light which is emitted from a laser diode 11 and is converted to a luminous flux of parallel rays by a collimator lens 12 and passes a light condensing hologram disk 13 becomes a scanning beam B4 which has a minimum beam diameter (beam waist) BW in the position of its focal length. When the light made incident on the light condensing hologram disk 12 is somewhat diverged or converged, positions of beam waists BW of scanning beams B5 and B6 and red ranges l5 and l6 where beam diameters are small are changed from the position of an initial read range in the direction of the optical axis, namely, in the direction of the read depth. Then, the whole of read ranges is indicates by L. Thus, the position of the collimator lens 12 on the optical axis is varied by a position varying means 14 to change its relative position to the laser diode 11.

Description

[Detailed description of the invention] Industrial applications The present invention relates to barcode scanners.

2. Description of the Related Art Conventionally, there is a barcode scanner of this type as shown in FIG. This uses a laser diode 1 as a light source, and uses a hologram disk 2 to deflect and scan a laser beam onto a barcode 3 to read it. More specifically, the emitted light from the laser diode 1 is collimated by the collimating lens 4, passes through the perforated reflection mirror 5, and enters one sector 6 of the hologram disk 2 (rotationally driven by a motor not shown). It is incident. The laser beam emitted from the hologram disk 2 becomes a beam that deflects and scans the barcode 3 due to the diffraction effect of the sector 6.

At this time, generally, the hologram disk 2 is provided with a light focusing function, and the reflected light from the barcode 3 is received by the same sector 6 and guided to the reflecting mirror 5 side, and the light is sent to the focusing lens 7, the light receiving element 8, etc. The reading light receiving system 9 is configured to process the signal as a read signal.

In the case of such a combination of the laser diode 1 and the hologram disk 2, there is generally a concern that reading errors may occur due to a wavelength shift of the laser diode 1. However, this point can be solved by measures such as containing the wavelength shift by a reliable temperature fixing method of the laser diode 1, or using a wavelength-stable laser diode (for example, a laser diode with an external mirror resonator or a DFB-laser diode, etc.). , a combination that avoids wavelength shift is possible.

On the other hand, in a barcode scanner, it is necessary that the diameter of the scanning beam be small enough to obtain reading resolution for the barcode 3. In particular, PO8
When considered as a compatible scanner, the scanning beam diameter is generally required to be 0.2 marks or less.

Naturally, these must also be achieved within sufficient reading width and reading depth. However, the laser beam diameter and reading depth are uniquely determined by wave optics,
0. The reading depth for a beam diameter of 2[I+rn or less is approximately several tens of marks, and it is theoretically impossible to provide a depth greater than that.

For this reason, by changing the focal length of each sector on the hologram disk, it is possible to effectively make it multi-focal, and among the signals read multiple times, the one with good resolution can be decoded as a barcode reading signal. There is something I did. This is known as a method of arranging hologram disks or convex lenses having sectors with sequentially different focal lengths, for example from VF Publication No. 53-16446.

For example, as shown in FIG. 5, among the plurality of sectors 6 on the hologram disk 2, the focal length of the sector 6a is fo+
, the focal length of the sector 6b is fo2, the focal length of the sector 6c is fns, and f II <f' Ha < f
They are manufactured with a size relationship of ns. Then, the read g@ range by each sector 6a, 6b, 6c, that is, the range where the scanning beam diameter is 0.2M or less, is a length Q, , Q2 . Q, then the scanning beams B, , B, , B by each sector 6a, 6b, 6c
, as shown in FIG. 6, and the total reading range is L due to the overlap of each reading range. In this way, the scanning beam diameter changes in the reading depth direction, and a wide area exists that can be scanned with a small beam diameter.

Other methods include, for example, ¥1I5FI 1986-1
As shown in Japanese Patent No. 78587, there is also a device in which a concave lens or a convex lens is added in order to obtain beams with multiple focal points. In this case, these lenses etc. are simultaneously scanned and used in conjunction with electrical modulation/demodulation circuits.

Problems to be Solved by the Invention However, in the case of the method disclosed in Japanese Patent Application Laid-Open No. 53-16446 (Fifth National Power Method), a plurality of different focal length sectors 6
Generally, it is difficult to design and manufacture a hologram disk 2 having such a structure (for example, a design that includes aberration correction for each sector is required), and the optical system for exposing and producing a disk master for this purpose is complicated. Further, it cannot be applied to a scanner using a beam deflector such as a polygon mirror.

Furthermore, in the case of the latter method of adding concave and convex lenses, a plurality of optical elements such as these lenses are required to be added.

Means for Solving the Problem The position variable means for varying the relative positions of the laser diode and the collimating lens on the optical axis at a low frequency speed is eliminated.

When the relative position of the working laser diode and the collimating lens on the optical axis changes, the beam focusing ability after passing through the collimating lens changes. As a result, the condensing position of the scanning beam determined by the subsequent beam condensing and deflecting optical system also changes in the reading depth direction.

In other words, the area scanned by the tiny beam increases, and the area where sufficient resolution necessary for barcode reading can be obtained increases.
A long depth read is performed.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 and 2. The basic configuration is similar to that shown in FIG. 4, in which a laser diode 11, a collimating lens 12, and a condensing hologram disk 13 as a beam condensing and deflecting optical system are arranged in this order, and a bar code (not shown) is arranged in this order. ). Note that the perforated reflection mirror and reading/receiving system shown in FIG. 4 are omitted.

Therefore, in this embodiment, by connecting the position variable means 14 to the collimating lens 12, the collimating lens 12
can be freely displaced in the optical axis direction, and the laser diode 11
The relative position of the collimating lens 12 and the collimating lens 12 on the optical axis, that is, the distance between the two can be varied. Although such a position variable means 14 itself can be constructed as appropriate using a motor, a solenoid, etc., the position of the collimating lens 12 by the position variable means 14 is temporally varied at a low frequency speed.

This is to change the condensing position of the scanning beam, and the principle thereof will be explained with reference to FIG. First, Figure 2 (21)
As shown in the figure, the laser beam is extracted from the laser diode 11, converted into an I1 line beam by the collimating lens 12, and incident on the condensing hologram disk 13. After exiting the condensing hologram disk 13, the laser beam is The scanning beam B4 has the minimum beam diameter (beam waist) BW at the position f. However, this is true when a beam of light is incident on the condensing hologram disk 13, and if the light incident on the condensing hologram disk 13 becomes a little diffused or convergent, the result shown in FIG.
l]) or (C), each scanning beam I3
．． ．． The position of the beam waist BW of B and the reading range Q, , Qo with a small beam diameter change in the optical axis direction, that is, in the direction of the reading depth, with respect to the position of the initial reading range ℃4. In other words, the focal length of the collimating lens 12 is FC, and the focal length of the condensing hologram disk 13 is f'.
If H, then □ = −□ 1-1 − fT fc f.

In a system where the composite focal length fT is a constant, it is regulated only by the relative positional relationship between the laser diode 11 and the collimating lens 12 on the 10th axis,
This 1) relationship is determined. And, Fig. 2(a)-(
In case C), the entire reading range is L.

Therefore, as in this embodiment, by varying the position of the collimating lens 12 on the optical axis by the position variable means 14 and changing the relative positional relationship with the laser diode 11, the fifth
Similar to or equivalent to the multifocal hologram disk system shown in the figure, the scanning beam system can be changed in the reading depth direction, making long depth reading possible. In comparison with the fifth national power method, according to this embodiment, there is no need to use a hologram disk that is difficult to design and manufacture, and a simple condensing hologram disk 13 is sufficient, resulting in low cost.

Furthermore, there is no need to use a separate lens or the like, resulting in a compact structure.

Incidentally, although the position of the collimating lens 12 is varied over time, if the moving speed at this time is too fast, all the signals of the bar code being read will become undecipherable. In this regard, the general scanning frequency of the scanner is 100 to 5.
Assuming 00 times/sec, if the speed changes within one order of magnitude or less, there is no problem with signal processing, and instantaneous reading can be performed without any particular delay in terms of barcode reading time. Therefore, in this embodiment, the position variable means 14
When the collimating lens 12 is periodically displaced, it is operated at a relatively low frequency speed.

In this embodiment, the collimator lens 12 side is moved back and forth on the optical axis by the position variable means 14, but the laser diode 11 side may also be moved. In addition, although the initial setting example is explained in which parallel light enters the condensing hologram disk 13, the same applies to cases where the initial setting is such that the light enters the condensing hologram disk 13 in a diverging or converging state. It is sufficient that the relative positional relationship between the diode 11 and the collimating lens 12 changes (in other words, the state shown in FIG. 2(b) or (C) may be used initially instead of the state shown in FIG. 2(a)). do).

In addition, in the combination system of the laser diode 11 and the condensing hologram disk 13, the reading optical system is not limited to the retroreflective reading optical system that performs the scanning beam and the return reflected light in the same sector as in the case of FIG. The system 9 may also be located elsewhere (see, for example, the case of the variant shown in FIG. 3).

Also, as a beam focusing deflection optical system, instead of the focusing hologram disk 13, as shown in FIG.
It is also possible to use a barcode scanner using a beam condensing and deflecting optical system I7 based on the laser diode 11 in combination with the laser diode 11.

Effects of invention book 11! As mentioned above, the IJ is provided with a position variable means that changes the relative position of the laser diode and the collimating lens on the optical axis, so the beam focusing property after passing through the collimating lens is changed, and the subsequent beam focusing deflection is changed. The focusing position of the scanning beam determined by the optical system can also be changed in the direction of the reading depth, increasing the area scanned by the tiny beam and increasing the area where sufficient resolution required for barcode reading can be obtained. At this time, the position is varied at a low frequency speed, so reading can be performed reliably without becoming impossible to decipher, and there is no need to use a special lens, etc., as in the past. There is no need to add anything, and there is no need to use a multifocal hologram disk or the like that is difficult to manufacture, and it can be made compact and inexpensive.

4. Explanation of the fiiff vehicle in the drawings. Fig. 1 is a conceptual diagram showing an embodiment of the present invention, Fig. 2 is a conceptual diagram showing the operating principle, Fig. 3 is a conceptual diagram showing a modified example, and Fig. 4 is a conceptual diagram showing an embodiment of the present invention.
The figure is a conceptual diagram showing a conventional example, FIG. 5 is a plan view of a multifocal hologram disk, and FIG. 6 is a conceptual diagram showing its operating principle.

DESCRIPTION OF SYMBOLS 11... Laser diode, 12... Collimating lens, 13... Beam condensing deflection optical system, 14... Position variable means, 17... For beam condensing deflection optical system Application
People Rico Co., Ltd. - Tohoku Su Co., Ltd. JZ Figure J, 3 Figure, 3 35 Figure 2 - Dan - 1

Claims (1)

[Claims] In a barcode scanner, a laser beam from a laser diode is collimated by a collimating lens, and then a minute beam is scanned on a barcode by a beam focusing and deflecting optical system. A barcode scanner characterized by being provided with a position variable means for varying a relative position at a low frequency speed.