Magnetic Barcode Research Articles

Robots, Radio, and Patron Self-Service

ABSTRACT The annual conference of the International Federation of Library Associations and Institutions was held in Glasgow, Scotland in August, 2002. Among the products and services on display in the vendor exhibit hall were several new systems which combine radio frequency identification (RFID) to facilitate the lending, return, and inventory of library materials. Unlike magnetic theft detection systems and barcode label systems, RFID allows each item to be identified fully by means of a computer chip. Also on display were robotic sorters which can be used with RFID or conventional labeling systems. In this Roundup, we describe systems built by several vendors, and suggest future applications of RFID and robotics in libraries and archives.

Passive wirelessly requestable sensors for magnetic field measurements

A direction-sensitive micro-magnetic field sensor is developed using the giant magneto-impedance (GMI) effect in a 30-μm diameter amorphous FeCoSiBNd wire. Consisting of a micro-sized zero-magnetostrictive amorphous wire of about 70-μm length, the GMI sensor was connected to a self-oscillating Colpitts oscillator circuit by laser welding. It shows a high sensitivity with a resolution of 100 nT for DC fields, quick response, and a high temperature stability. Reproducible measurements of a surface-flux distribution of mechanically 100 μm structured magnetic bar codes were carried out. Surface Acoustic Wave (SAW) devices are shown as passive, radio-requestable sensor devices. A new type employs the electrical load of the SAW device by the impedance of conventional sensors. In order to develop a wirelessly interrogable magnetic field sensor, the combination of the GMI sensors and SAW transponders is discussed and the results are shown.

A new high density magnetic bar code system

Magnetic bar codes can be used in dirty environments instead of optical bar codes or as invisible codes in order to enhance the security of prepaid cards. In this article, we propose a high density magnetic bar code system in which the existence or nonexistence of a bar element is detected by a magnetic bridge. A micro head constituting a magnetic bridge is fabricated with thin amorphous cores and thin copper wire coils. The magnetic bar elements are printed with magnetic ink. The basic characteristics, such as signal separation from neighboring bar elements, are discussed in terms of the element width and the space between two adjacent elements.

Readout Characteristics of Magnetic-Ink-Printed Bar Codes with Anisotropic Permeabilities

Invisible bar codes such as magnetic ones play an important role in systems requiring security. The magnetic bar code system described in this paper uses magnetic anisotropy as a carrier of information. Three kinds of magnetic ink were used, containing iron base alloy, Mn-Zn ferrite powder, and carbonyl iron powder. Although the level of the output voltage needs subsequent amplification, all of these magnetic ink can be used for making magnetic bar codes, especially the one containing iron base alloy. We explain a possible mechanism for two sub-peaks occurring berfore and after the main peak.

A new magnetic bar code system based on a magnetic anisotropy detection (abstract)

Magnetic bar codes can be used in unclean environments, where widely used optical bar code systems cannot be applied. Readout system for magnetic bar codes can also be made much simpler than optical ones. A new magnetic bar code system is proposed, in which binary information is coded in the sign of tilted angles of magnetic strips from a given standard direction. This scheme is unique compared to the conventional optical bar code, where width or space of the parallel pattern carries information, or an already reported magnetic bar code, where cross sectional shapes of pattern engraved in a ferromagnetic body carries information. Each of the magnetic strips brings about magnetic anisotropy due to its shape effect, hence angular dependent permeability in the proximity of the strip. The sign of the tilted angle of each magnetic strip is detected inductively through the angular dependent permeability by using a magnetic pickup head with a pair of cross-coupled figure-eight coils, where the sign of mutual inductance between the primary and the secondary figure-eight coil has one to one relationship to the sign of the tilted angle. Because the detection of the tilted angle is independent of scanning speed, variation in the scanning speed of the readout head does not affect the performance. In our preliminary study, the proposed magnetic bar code system was examined using pickup head consisting of a pair of cross-coupled 10-turn figure-eight coils which was embedded in a rectangular ferrite rod with cross-shape groove on the top surface of 6.5×3 mm dimension. The head was made thinner in the scanning direction to allow dense alignment of the pattern. Two kinds of pattern were made: the one was by aligning short amorphous wires (5 mm in length and 120 μm in diameter) on the plastic film and the other by using a thin (10 μm in thickness) copper film with tilted slits backed by an amorphous ribbon. These samples of magnetic bar code patterns were scanned with lift-off of 1 mm under the operating condition of 120 kHz and 200 mA. Amplitudes of the positive and the negative peak of the output voltage well exceeded 10 mV. Density of the pattern in the preliminary study was 7 bits for the bar code length of 2.6 cm. We will discuss several factors to make density of the pattern higher. Because the pickup coils can be assembled with planar coils and because the magnetic bar code itself is thin, the total system of this bar code scheme can be realized in thin form.

新しい磁気バーコードの試み

A new magnetic bar code system is proposed, in which information is coded in a series of anisotropic perrneabilities introduced by, for example, slightly canted magnetic strips. The principal direction of anisotropy with respect to a given direction as a reference can be coded as 1 or 0. This principal direction is detected inductively by using crosscoupled figure-of-eight coils, in which the sign of the mutual inductance changes according to the sign of the angle between the principal direction and the given direction. The readout is not affected by the scanning speed in this system.