Development of non-contact detection method for recorded magnetic information using MI micro magnetic sensors and PRML signal processing

传统的公共服务自动机，如自动检票机、自动柜员机(ATM)和自动售货机，由于其紧密接触读取票券和钞票中记录的磁信息，并在头部位置去除皱巴巴的钞票，因此遭受了定期更换磨损的磁头(MR头)的一些麻烦。因此，我们尝试引入一种灵敏的微型磁性传感器(MI传感器)来实现对这些车票和钞票上记录的磁性信息的非接触读取方法，以减少故障。MI传感器由首席研究员发明，并在JST的资金支持下由爱知钢铁公司进行商业化生产。在实验中，我们重点研究了自动检票机(欧姆龙公司生产的自动检票机)。并采用爱知钢铁公司生产的非晶丝CMOSIC型高密度MI传感器，获得了如下结果：(1)稳定的…通过将直径20μm、长2 mm的非晶丝的MI传感器磁头边缘点设置在距埃德蒙森型磁票面约0.3 mm处，成功地实现了更多的非接触读取。该磁票面由128位数字图案记录，节距为100μm和200μm。票面非晶丝轴线的角度为45度。(2)MI传感器输出的波形在100μm俯仰区和200μm俯仰区都是具有相同梯度的几何(分段线性)三角形。通过在MI传感器的输出端增加无源RC差动电路，得到了在100μm螺距和200μm螺距范围内幅值几乎相同的矩形波形。在非接触读取240位记录模式的通勤通行证时，MI传感器输出脉冲串的幅度发生变化，通过在RC差动电路中增加饱和放大器来补偿这一变化。(5)利用磁票的磁偶极子模型，考虑非晶丝传感头的大小和角度，分析了MI传感器输出检测到的三角波形的来源，其中产生了粗略的三角形形状，而不是尖锐的三角形波形。由于制备了足够灵敏的MI传感器，因此PRML方法不是必须的，利用灵敏的微型磁传感器(非晶线CMOSIC MI传感器)基本成功地实现了磁票记录数字图案的非接触检测方法。所开发的非接触式检测方法将成功应用于自动取款机和自动售货机。较少

Conventional public service automatic machines such as the automatic ticket gate, the automated telling machine (ATM) and the automatic vending machine suffer from some troubles of regular replacement of worn magnetic heads (MR head) due to its close contact reading of the recorded magnetic information in the ticket and the bank note, and removing scrumpled bank note at the head position. Therefore, we have tried to introduce a sensitive micro magnetic sensor (MI sensor) for realization of non-contact reading method for recorded magnetic information in these tickets and bank notes for decrease of troubles. The MI sensor has been invented by the chief researcher and commercially produced by the Aichi Steel Co. with the financial support by the JST. In the experiment, we have focused to the automatic ticket gate (the handler made by Omron Co.) and used some amorphous wire CMOS IC type high density fabricated MI sensors made by Aichi Steel Co..Obtained results are as follows :(1) A stable … More non-contact reading was successfully carried out by setting a MI sensor head edge point of an amorphous wire with 20 μm diameter and 2 mm length at around 0.3 mm apart from an Edmonson type magnetic ticket surface recorded by 128 bits digital pattern with 100 μm pitch area and 200 μm pitch area. Angle of the amorphous wire axis for the ticket surface was 45 degree.(2) Waveform of the MI sensor output is geometric (piecewise linear) triangle shape withidentical gradient both in the 100 μm pitch area and 200 μm pitch area. Therefore, the amplitude of the triangle shape ac wave at the 100 μm pitch area is just half of that at the 200 μm pitch area.(3) Rectangular waveform with almost identical amplitude both in the 100 μm pitch area and 200 μm pitch area was obtained by adding a passive RC differential circuit to the output terminal of the MI sensor. That is, the digital output was obtained using the MI sensor without any digital processing circuit.(4) A variation of the amplitude of the MI sensor output pulse train was occurred for non-contact reading of a commuter pass with 240 bit recorded pattern, which was compensated by adding a saturable amplifier to the RC differential circuit.(5) The origin of detected triangle waveform of the MI sensor output was analyzed using a magnetic dipole model for the magnetic ticket considering the size and the angle of the amorphous wire sensor head, in which a rough tendency of triangle shape generation was resulted but not sharp triangle waveform. This is a remaining problem.The PRML method was not necessary due to preparation of sufficiently sensitive MI sensor.The purpose of realization of a non-contact detection method for recorded digital pattern of the magnetic ticket was basically succeeded using a sensitive micro magnetic sensor (amorphous wire CMOS IC MI sensor). The developed non-contact detection method would successfully be applied to the ATM and the automatic vending machines. Less