JPH0353398A - Magnetic bar code - Google Patents

Abstract

PURPOSE:To improve resolution and to extend a distance for detection by providing plural groove-shaped rectangular patterns on a magnetic body or a conductive metal and giving a shallower depth to a wider groove of each pattern. CONSTITUTION:When a magnetic field is applied to an imprinted bar code plate 1, the change of the magnetic field due to grooves having the same width is reduced according as grooves are shallower. Consequently, the change of the magnetic field due to wider grooves 3 is smaller because wider grooves 3 are made shallower. Since the change of the magnetic field due to wider grooves 3 is reduced, that due to narrower grooves 4 is not concealed. Thus, bar code patterns are read with a long distance for detection and a high resolution with which a conventional carved bar code plate cannot be read.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetically read barcodes.

[Conventional technology] In recent years, computers have been widely introduced for OA and FA in logistics management, and are widely used, for example, to manage product sales in large-scale retail stores and to manage the production of parts and products in manufacturing processes. . Devices that optically read printed barcodes are often used as input terminal devices, and strip patterns (optical barcodes) are printed on products and parts.
is added. Although this optical barcode has the advantage of being readable from a relatively long distance, it has the drawbacks of being susceptible to dirt (for example, adhering dust) on the reading surface and having poor durability. In particular, conventional optical barcodes cannot be used in manufacturing processes where there is a high risk of contamination.

On the other hand, in recent years, stamped barcodes having a plurality of rectangular patterns stamped in concave or convex shapes on a metal plate have become known as stain-resistant barcodes. (1986 Japanese Society of Applied Magnetics Academic Lecture Abstracts, p. 307).

The configuration of the engraved barcode is shown in FIGS. 3(a) and 3(g).

(a) is a plan view, and (b) is a sectional view. Figure 3(a)
, a rectangular pattern 2 is stamped on a barcode plate 1. The stamped barcode can be read using magnetism. That is, as shown in FIG. 3(G), a magnetic field 6 is applied to the barcode plate 1 by a permanent magnet 5. The combination of the wide grooves 3 and the narrow grooves 4 forming the rectangular pattern 2 on the barcode plate 1 distorts the applied magnetic field 6. Since the distortion can be detected by the magnetic sensor 7, the rectangular pattern 2 can be read from the output of the magnetic sensor 7. That is, barcodes can be read.

Since the magnetic field is not affected by dirt, barcodes engraved using this method can be read without being affected by dirt. Additionally, the uneven pattern on the board is more durable than optical barcodes.

[Problems to be Solved by the Invention] Although engraved barcodes are highly durable, there is a problem in that in order to reduce the resolution, the detection distance must also be reduced. That is, since the magnetic field used to read the engraved barcode does not travel in a straight line like light, it is necessary to bring the barcode plate and the magnetic sensor as close as possible in order to accurately read the groove pattern. Figure 2 (b) shows the magnetic flux density distribution near the groove when a magnetic field is applied to a conventional engraved barcode plate. In FIG. 2(B), when a magnetic field is applied to the engraved barcode plate, the change in the magnetic field caused by grooves of the same depth increases as the width of the groove increases.

Therefore, as shown in FIG. 2 (b), when the wide groove 3 and the narrow groove 4 are close to each other, the change in the magnetic field due to the wide groove 3 is suppressed by the change in the magnetic field due to the narrow groove 4. Patterns created by narrow grooves cannot be detected by magnetic sensors. This tendency is stronger as the groove width becomes smaller and the detection distance becomes larger. For example, if the width of the narrow groove 4 is 0.3 mm, reading cannot be performed even if the two are in close contact. Then, the width of the narrow groove 4 is 0. In the case of 5mr+, the distance between the magnetic sensor and the barcode plate is set to 0. It is necessary to make it 1 mm or less. However, since paint and dirt adhere to the surface of engraved barcode boards used in harsh environments, the 0.
A detection distance of about 3 degrees is required as a minimum. However,
Although it is possible to increase the detection distance by increasing the width of the bar, this attempt increases the width of the entire barcode and is not practical.

An object of the present invention is to eliminate such conventional drawbacks and to provide a magnetic barcode that can achieve high resolution and a long detection distance.

[Means to solve the problem]

In order to achieve the above object, the magnetic barcode according to the present invention has a plurality of rectangular patterns provided in the form of grooves in a magnetic material or conductive metal, and for each pattern, the width of the groove is larger. , which is a shallower version of the full bottom.

[Function] FIG. 2(a) shows the near-full magnetic flux density distribution when a magnetic field is applied to the magnetic barcode plate of the present invention.

When a magnetic field is applied to an engraved barcode plate, the change in the magnetic field caused by grooves of the same width becomes smaller as the depth of the groove becomes shallower. Therefore, in FIG. 2(a), since the bottom of the wide groove 3 is made shallow, the change in the magnetic field due to the wide groove 3 is small. Since the magnetic field change due to the wide groove 3 is reduced, the magnetic field change due to the small width groove is not hidden. Therefore, barcode patterns can be read at a high detection distance or with high resolution, which was impossible with conventional engraved barcode plates.

[Example] Next, an example of the present invention will be described with reference to FIG. (a) is a plan view, and (b) is a sectional view. Figure 1 (
In a), the plate surface of the mild steel barcode plate 1 is shown in Figure 1 (
As shown in b), the bottom of the wide groove 3 is made shallow and the bottom of the narrow groove 4 is deep, and the wide groove 3, the small width groove 4, and the spaces between the grooves are combined to form a rectangular pattern. 2 was constructed.

The magnetic field change due to the groove is determined by the width of the groove, the depth of the groove, and the height from the barcode plate. As the depth of the groove increases, the change in the magnetic field due to the groove also increases, and when the depth of the groove becomes 50% or more of the width of the groove, the change in the magnetic field due to the groove is almost saturated. Therefore, in order to cause a sufficient change in the magnetic field with the small width groove 4, the depth of the groove is made the same as the groove width. And the wide groove 3
The depth of the groove was optimized within the range of machining accuracy so as to produce a magnetic field change comparable to that produced by the small width groove 4. Dimensions are thin bar width 0. It is a 5mm engraved barcode plate, the width of the wide groove 3 is 1.25mm, and the depth of the groove is O. Imm, the width of the small groove 4 is 0.5nvn
, the depth is 0.5Nrl, the width of the narrow bar width is 0.3+nm, and the width of the wide groove 3 is 0.7mm.
, the depth is 0.1 m, the width of the small groove 4 is 0.3 mm,
The depth is 0.3m.

In the embodiment shown in Fig.], the narrow bar width is 0.5wun, 0
．． It was possible to read the stamped patterns well with the magnetic sensor on any of the trivalent stamped barcode plates.

In the above embodiment, a magnetic iron plate was used as the barcode plate 1, and DC excitation with a permanent magnet 5 was used, but the same method can be used using a conductive barcode plate and AC excitation with a coil. Needless to say, it is effective.

[Effects of the Invention] In the case of conventional engraved barcodes, the narrow bar width of the barcode that can be read in close contact is 0. It was 5 mm or more. However, with the magnetic barcode of the present invention, the narrow bar width is 0. 3mm can now be read.

Also, the width of the thin bar is 0. 5+nm barcodes can now be read at a detection distance of 0.3M. In addition, since the magnetic field change due to the groove can be made almost constant regardless of the width,
The output of the magnetic sensor is also almost constant, which has the effect of eliminating the need for automatic gain control in the circuit.

[Brief explanation of drawings]

FIG. 1(a) is a plan view showing an embodiment of the present invention, (b) is a cross-sectional view of the same, and FIGS. 2(a) and (b) are magnetic flux density distributions and grooves for the present invention and the conventional example, respectively. FIG. 3(a) is a plan view illustrating the prior art, and FIG. 3(g) is a cross-sectional view of the same. 1... Barcode board 2... Rectangular pattern 3
...Wide groove 4...Small width groove 5.
...Permanent magnet 6...Magnetic field 7...Magnetic sensor

Claims (1)

[Claims] (1) A magnetic barcode that has a plurality of rectangular patterns provided in the form of grooves in a magnetic material or conductive metal, and for each pattern, the wider the groove, the shallower the groove bottom. .