JP2012128683A - Magnetic pattern detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a magnetic pattern detection apparatus in which reduction in detection accuracy of a magnetic pattern can be avoided even if an output level of a sensor output signal of a magnetic sensor device varies due to an individual difference or a temperature.SOLUTION: A magnetic pattern detection apparatus 1 includes a first offset adjusting circuit 831 which produces a correction output signal by adding an addition signal to a rectification signal from a magnetic sensor device 20, a magnetic pattern detection section 100 which detects a magnetic pattern of a medium 2 on the basis of the correction output signal which is produced when the medium 2 passes through the magnetic sensor device 20, and an addition signal adjusting section 97 which performs offset adjustment processing for turning an output level of the correction output signal to a target output level by adjusting an output level of the addition signal each time the magnetic pattern of the medium 2 is detected. Variation in an output level of a sensor output signal caused by an individual difference or heating of a magnetic sensor element 40 is corrected by the offset adjustment processing, thereby avoiding or suppressing reduction in detection accuracy of the magnetic pattern.

Description

  The present invention relates to a magnetic pattern detection device for detecting a magnetic pattern of a medium such as an object to which a magnetic material is attached or a banknote printed with magnetic ink by a sensor output signal from a magnetic sensor.

  The magnetic pattern detection device detects a change in magnetic flux when the magnetized medium passes through the magnetic sensor, amplifies the analog sensor output signal output from the magnetic sensor by the signal processing unit, and then converts it to a digital signal. Thereafter, the type of the medium is discriminated by comparing with a pattern stored and held in advance. Such a magnetic pattern detection apparatus is described in Patent Document 1.

  Here, the output level of the sensor output signal may vary depending on the individual magnetic sensor. If the output level of the magnetic sensor varies for each individual, the detection accuracy of the magnetic pattern varies for each magnetic pattern detection device. Problem occurs. In order to solve such a problem, the signal processing unit of the magnetic pattern detection device of Patent Document 1 is equipped with an offset adjustment circuit that performs an offset adjustment process of the sensor output signal between the amplifier circuit and the A / D conversion circuit. ing.

JP 2007-241653 A

  The offset adjustment process is performed by adjusting the output level of the sensor output signal from the magnetic sensor during standby to a predetermined output level. If such an offset adjustment process is performed when the magnetic pattern detection device is turned on, the variation in the output level of the sensor output signal due to the individual difference of the magnetic sensor can be corrected. Therefore, the magnetic pattern due to the individual difference of the magnetic sensor can be corrected. Variations in detection accuracy can be avoided. However, since the output level of the sensor output signal also changes due to the heat generated by the magnetic sensor itself, when the detection of the magnetic pattern of a plurality of media is performed continuously, the time point when the magnetic pattern of the first medium is detected. There is a problem that the output level of the sensor output signal changes between the time when the magnetic pattern of the last medium is detected and the detection accuracy of the magnetic pattern is lowered.

  In view of the above problems, an object of the present invention is to reduce the detection accuracy of a magnetic pattern even when the output level of a sensor output signal varies due to individual differences of magnetic sensors and temperature conditions of the magnetic sensor. An object of the present invention is to propose an offset adjustment processing method for a magnetic pattern detection device and a magnetic pattern detection device.

In order to solve the above problems, a magnetic pattern detection apparatus of the present invention is
An output correction unit that generates a correction sensor output signal obtained by adding the addition signal to the analog sensor output signal from the magnetic sensor;
A magnetic pattern detection unit that detects a magnetic pattern of the medium based on the correction sensor output signal when the medium passes through the magnetic sensor;
The output level of the correction sensor output signal is adjusted by adjusting the output level of the addition signal after the medium has passed the magnetic sensor and before the next medium passes the magnetic sensor. And a first addition signal adjustment unit which sets a predetermined target output level.

  According to the present invention, when the magnetic patterns of a plurality of media are continuously detected, after the medium has passed a predetermined number of magnetic sensors and before the next medium passes the magnetic sensor, Offset adjustment processing for setting the output level of the correction sensor output signal to the target output level is performed. As a result, variations in the output level of the sensor output signal due to individual differences among the magnetic sensors, heat generation, etc. are corrected, so that a decrease in detection accuracy of the magnetic pattern can be avoided or suppressed.

  In the present invention, it has a second addition signal adjustment unit that adjusts the output level of the addition signal to adjust the output level of the correction sensor to the target output level at power-on and restart. The processing speed at which the 1 addition signal adjustment unit sets the output level of the correction sensor output signal as the target output level is the processing speed at which the second addition signal adjustment unit sets the output level of the correction sensor output signal as the target output level. It is desirable to be faster. In this way, when the power is turned on and restarted, offset adjustment is performed to set the output level of the correction sensor output signal to a predetermined target output level. Therefore, the sensor output signal caused by the individual difference of the magnetic sensor is adjusted. Output level variation is corrected. In addition, if the process in which the first addition signal adjustment unit sets the output level of the correction sensor output signal to the target output level is faster than that of the first addition signal adjustment unit, the process is performed after the medium has passed the predetermined number of magnetic sensors. Thus, it is easy to perform the offset adjustment process in a short time until the next medium passes through the magnetic sensor. Here, the time of restart means the time when the output level of the previous addition signal is lost and the output level of the addition signal is returned to the unadjusted state by operating the reset switch or the like of the apparatus.

  In the present invention, the output correction unit includes a D / A conversion circuit that outputs the addition signal, and an adder that adds the sensor output signal and the addition signal, and the first addition signal adjustment unit. Includes a first command value output unit that outputs a digital command value for adjusting the output level of the addition signal to the D / A conversion circuit, and the correction during standby in the dynamic range of the correction sensor output signal. Proportional relationship storage unit that stores in advance a proportional relationship established between the output level of the sensor output signal and the command value, and the difference between the output level of the correction sensor output signal and the target output level A difference calculating unit that calculates the output value of the correction sensor output signal based on the command value output by the command value output unit, the difference, and the proportional relationship. When the appropriate value is calculated and the appropriate value is calculated, the command value output from the first command value output unit is set to the appropriate value. It is desirable to include a first setting unit. That is, in the offset adjustment process that is performed after a predetermined number of media passes through the magnetic sensor and before the next medium passes through the magnetic sensor, the offset adjustment process that is performed when the power is turned on or restarted is performed. Since the output level of the correction sensor output signal is once set to the target output level, the output level of the correction sensor output signal at the start of the offset adjustment process is dynamic even if the output level of the sensor output signal subsequently changes. It is in range. In addition, since a proportional relationship is established between the command value and the correction sensor output signal within the dynamic range, the output level of the correction sensor output signal is set to the target output level based on the command value, the difference, and the proportional relationship. The appropriate value of the command value for As a result, the offset adjustment process for setting the output level of the correction sensor output signal to a predetermined target output level can be performed at high speed, so that after the medium has passed the predetermined number of magnetic sensors, Even if the time until it passes through the magnetic sensor is short, the offset adjustment process can be performed.

  In this case, the second addition signal adjustment unit outputs a digital command value for adjusting the output level of the addition signal to the D / A conversion circuit, and the command value A process for changing the command value output from the second command value output unit in accordance with a binary search method with the first search range between the upper limit value and the lower limit value, and the output level of the correction sensor output signal and the target The process of comparing the output levels is repeated in this order, and the binary search unit that acquires the command value as the appropriate value when the output level of the correction sensor output signal reaches the target output level, and the appropriate value is acquired. In this case, it is desirable to include a second setting unit that maintains the command value output from the second command value output unit at the appropriate value. That is, in the offset adjustment process performed at power-on or restart, it is unclear whether the output level of the correction sensor output signal at the start of the offset adjustment process is within the dynamic range, so the command value and the correction sensor output signal It is also unclear whether or not a proportional relationship is established. Therefore, if the command value is searched until the output level of the correction sensor output signal reaches the target output level according to the binary search method, an appropriate value of the command value can be obtained in a relatively short time.

  In this case, the second addition signal adjustment unit outputs a digital command value for adjusting the output level of the addition signal to the D / A conversion circuit, and the second command value output unit. 2 The command value output from the second command value output unit is set until the offset command value of the command value output unit is set to an upper limit value, and then the output level of the correction sensor output signal becomes the target output level. The process of decreasing the value by a predetermined value and the process of comparing the output level of the correction sensor output signal and the target output level are repeated in this order, or the command value of the offset second command value output unit is reduced to the lower limit. After that, the command value output from the second command value output unit is a predetermined value until the output level of the correction sensor output signal becomes the target output level. The process of increasing and the process of comparing the output level of the correction sensor output signal and the target output level are repeated in this order, and the command value when the output level of the correction sensor output signal becomes the target output level is set appropriately. A sequential search unit that acquires as a value, and a second setting unit that maintains the command value output from the second command value output unit at the appropriate value when the appropriate value is acquired can do. According to such a sequential search, an appropriate value of the command value can be reliably obtained.

  In the present invention, the magnetic sensor includes a plurality of magnetic sensors, and the sensor output signal is sequentially output from the plurality of magnetic sensors by the magnetic sensor to which the sensor output signal is output at a certain timing. And the first addition signal adjustment unit and the second addition signal adjustment unit adjust the output level of the addition signal every time the magnetic sensor is switched at the predetermined timing. It is desirable to set the output level of the signal to the target output level. That is, in a multi-channel type magnetic pattern detection device equipped with a plurality of magnetic sensors, there is a problem that the detection accuracy of the magnetic pattern is lowered when the output level of the sensor output signal from each magnetic sensor varies. Therefore, if offset adjustment processing is performed to set the output level of the correction sensor output signal of each magnetic sensor to the target output level every time the channel is switched, the output level of the sensor output signal varies due to individual differences of each magnetic sensor. Thus, it is possible to avoid a decrease in magnetic pattern detection accuracy. Here, when the offset adjustment processing of a plurality of magnetic sensors is performed after the medium has passed the predetermined number of magnetic sensors and before the next medium passes the magnetic sensor, the offset adjustment of each magnetic sensor is performed. Although the process must be completed in a short time, according to the present invention, the first addition signal adjustment unit is a correction sensor in the offset adjustment performed in the middle when the magnetic patterns of a plurality of media are continuously detected. Since the appropriate value of the command value for setting the output level of the output signal as the target output level is calculated, the output level of the correction sensor output signal can be set to the target output level in a short time.

  In the present invention, the predetermined number is preferably one. In this way, offset adjustment processing is performed every time the magnetic pattern of the medium is detected, so that variations in the output level of the sensor output signal of the magnetic sensor due to individual differences and temperature conditions can be reliably corrected. Therefore, it can avoid that the detection accuracy of a magnetic pattern falls.

  According to the present invention, when the magnetic patterns of a plurality of media are detected in succession, after the medium passes a predetermined number of times, the next medium passes the magnetic sensor. In addition, the output level of the correction sensor output signal is set to the target output level. Therefore, it is possible to avoid or suppress a decrease in the detection accuracy of the magnetic pattern due to variations in the output level of the sensor output signal due to temperature or the like.

It is explanatory drawing which shows the structure of the magnetic pattern detection apparatus of this invention. It is explanatory drawing of the magnetic sensor apparatus which a magnetic pattern detection apparatus mounts. It is explanatory drawing of the magnetic sensor element used for the magnetic sensor apparatus. It is a block diagram which shows the electric constitution of a magnetic pattern detection apparatus. It is explanatory drawing of a 1st offset adjustment process. It is explanatory drawing of a 2nd offset adjustment process. It is explanatory drawing which shows the characteristic of the various magnetic inks formed on a medium. It is explanatory drawing which shows the principle which detects the presence or absence of a magnetic pattern from the medium in which the magnetic pattern from which a kind differs was formed in the magnetic pattern detection apparatus. It is explanatory drawing of the 1st offset adjustment process of a modification.

  A magnetic pattern detection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

(overall structure)
FIG. 1 is an explanatory diagram showing a configuration of a magnetic pattern detection device according to the present invention, and FIGS. 1A and 1B are an explanatory diagram schematically showing a main configuration of the magnetic pattern detection device, and a cross-sectional configuration. It is explanatory drawing shown typically.

  A magnetic pattern detection device 1 shown in FIG. 1 is a device that detects magnetism from a medium 2 such as banknotes, securities, and the like, and performs authenticity determination and type determination. A sheet is detected by a roller, a guide (not shown) or the like. And a magnetic sensor device 20 that detects magnetism from the medium 2 at an intermediate position on the medium moving path 11 by the conveying device 10. In this example, the roller and the guide are made of a nonmagnetic material such as aluminum. In this example, the magnetic sensor device (magnetic detection unit) 20 is disposed below the medium movement path 11, but may be disposed above the medium movement path 11. In any case, the magnetic sensor device 20 is arranged so that the sensor surface 21 faces the medium moving path 11.

  In the medium 2, a magnetic pattern is attached to the narrow magnetic region 2a extending in the moving direction X of the medium 2 by magnetic ink, and there are a plurality of kinds of magnetic patterns having different residual magnetic flux density Br and permeability μ. The magnetic ink is formed. For example, the medium 2 is formed with a first magnetic pattern printed with a magnetic ink containing a hard material and a second magnetic pattern printed with a magnetic ink containing a soft material. Therefore, the magnetic pattern detection device 1 of the present embodiment detects the presence / absence of each magnetic pattern in the medium 2 based on both the residual magnetic flux density level and the magnetic permeability level. In this example, the magnetic sensor device 20 for detecting the two types of magnetic patterns is common.

(Configuration of magnetic sensor device)
FIG. 2 is an explanatory view of the magnetic sensor device 20 according to the present invention. FIGS. 2A and 2B are explanatory views showing a layout of magnetic sensor elements and the like in the magnetic sensor device 20, and the magnetic sensor elements. It is explanatory drawing which shows direction.

  As shown in FIGS. 1 and 2A, the magnetic sensor device 20 includes a magnetic field applying magnet 30 that applies a magnetic field to the medium 2, and a magnetic flux in a state in which a bias magnetic field is applied to the medium 2 after the magnetic field is applied. And a nonmagnetic case 25 that covers the magnetic field applying magnet 30 and the magnetic sensor element 40. The magnetic sensor device 20 includes a sensor surface 21 that forms substantially the same plane as the medium movement path 11, and slope portions 22 and 23 that are connected to both sides of the sensor surface 21 in the moving direction of the medium 2. The shape is defined by the shape of the case 25.

  The magnetic sensor device 20 extends in a direction crossing the moving direction X of the medium 2, and a plurality of magnetic field applying magnets 30 and magnetic sensor elements 40 are arranged in a direction crossing the moving direction X of the medium 2. ing. In this example, the magnetic sensor device 20 extends in the medium 2 width direction Y orthogonal to the moving direction X among the directions intersecting the moving direction X of the medium 2, and includes the magnetic field applying magnet 30 and the magnetic sensor element. A plurality 40 is arranged in the medium 2 width direction Y orthogonal to the movement direction X.

  In this example, the magnetic field application magnet 30 is arranged as a first magnetic field application magnet 31 and a second magnetic field application magnet 32 on both sides in the moving direction of the medium 2 with respect to the magnetic sensor element 40, and is indicated by an arrow X1. A magnetic field application first magnet 31, a magnetic sensor element 40, and a magnetic field application second magnet 32 are arranged in this order along the moving direction of the medium 2 shown. Further, the magnetic field application second magnet 32, the magnetic sensor element 40, and the magnetic field application first magnet 31 are arranged in this order along the moving direction of the medium 2 indicated by the arrow X2, and the medium 2 is indicated by the arrow X1. The magnetic characteristic of the medium 2 can be detected regardless of the direction and the direction indicated by the arrow X2. Here, the magnetic sensor element 40 is disposed at an intermediate position between the first magnetic field application magnet 31 and the second magnetic field application magnet 32, and is separated from the magnetic sensor element 40 from the first magnetic field application magnet 31. The distance is equal to the separation distance between the magnetic field application second magnet 32 and the magnetic sensor element 40. Note that the magnetic field application first magnet 31, the magnetic sensor element 40, and the magnetic field application second magnet 32 are all arranged at positions overlapping in the moving direction of the medium 2.

  In this example, the magnetic field application magnet 30 (the first magnetic field application magnet 31 and the second magnetic field application magnet 32) includes a permanent magnet 35 such as a ferrite or neodymium magnet. In both the first magnetic field application magnet 31 and the second magnetic field application magnet 32, the permanent magnet 35 has a pole on which the side located on the sensor surface 21 is different from the side opposite to the side on which the sensor surface 21 is located. Magnetized. In the permanent magnet 35, a surface located on the sensor surface 21 side functions as a magnetized surface 350 for the medium 2.

  The plurality of permanent magnets 35 used for the magnetic field applying magnet 30 are all the same in size and shape, but are arranged in the following orientations. First, in both the first magnetic field application magnet 31 and the second magnetic field application magnet 32, the permanent magnets 35 adjacent in the medium 2 width direction Y orthogonal to the moving direction X of the medium 2 are opposite to each other. Magnetized. That is, of the plurality of permanent magnets 35 arranged in the medium 2 width direction Y orthogonal to the movement direction X of the medium 2, one permanent magnet 35 has its end located on the medium movement path 11 side attached to the N pole. The end located on the side opposite to the medium moving path 11 side is magnetized to the S pole, but in the medium 2 width direction Y perpendicular to the moving direction X of the medium 2 with respect to the permanent magnet 35. The adjacent permanent magnets 35 are magnetized at the S pole at the end located on the medium moving path 11 side, and are magnetized at the N pole at the end opposite to the medium moving path 11 side. In this embodiment, the permanent magnet 35 of the first magnetic field application magnet 31 and the permanent magnet 35 of the second magnetic field application magnet 32 that face each other in the moving direction of the medium 2 have different poles across the magnetic sensor element 40. Opposite. However, the permanent magnet 35 of the magnetic field application first magnet 31 and the permanent magnet 35 of the magnetic field application second magnet 32 that face each other in the moving direction of the medium 2 are arranged so that the same poles face each other across the magnetic sensor element 40. Sometimes placed.

(Configuration of magnetic sensor element)
FIG. 3 is an explanatory diagram of the magnetic sensor element 40 used in the magnetic sensor device 20 according to the present invention. FIGS. 3A, 3B, and 3C are front views of the magnetic sensor element 40 and the magnetic FIG. 5 is an explanatory diagram of an excitation waveform for the sensor element 40 and an explanatory diagram of an output signal from the magnetic sensor element 40. FIG. 3A shows a state in which the medium 2 moves in a direction perpendicular to the drawing.

  As shown in FIG. 1B, each of the magnetic sensor elements 40 has a thin plate shape, and the size in the width direction W40 is larger than the size in the thickness direction T40. The magnetic sensor element 40 is disposed with the thickness direction T40 facing the moving direction X of the medium 2, and the width direction W40 faces the medium 2 width direction Y orthogonal to the moving direction X of the medium 2.

  The magnetic sensor element 40 is covered with a thin plate-like nonmagnetic member 47 having a thickness of about 0.3 mm to 1 mm made of ceramic or the like on both sides. The magnetic sensor element 40 may be housed in a magnetic shield case (not shown). In this case, the magnetic shield case is opened at the top where the medium 2 movement path is located, and the magnetic sensor element 40 is exposed from the magnetic shield case toward the medium movement path 11.

  As shown in FIGS. 1B, 2A, 2B, and 3A, the magnetic sensor element 40 includes a sensor core 41, an excitation coil 48 wound around the sensor core 41, and a sensor core. And a detection coil 49 wound around 41. In this example, the sensor core 41 includes a body portion 42 extending in the width direction W40 of the magnetic sensor element 40, and a magnetic flux collecting protrusion 43 that protrudes from the body portion 42 toward the medium moving path 11 side of the medium 2. It has. Here, the magnetic flux collecting protrusions 43 are configured as two magnetic flux collecting protrusions 431 and 432 that protrude from both ends of the body portion 42 in the width direction W40 toward the medium moving path 11 side of the medium 2. The two magnetic flux collecting projections 431 and 432 are separated in the width direction W40. In addition, the sensor core 41 includes a protrusion 44 that protrudes from the body portion 42 to the opposite side of the magnetic flux collection protrusion 43. In this example, the protrusion 44 is the both end portions of the body portion 42 in the width direction W 40. Are formed as two protrusions 441 and 442 that protrude toward the opposite side of the medium 2 from the medium moving path 11 side.

  With respect to the sensor core 41 configured as described above, the exciting coil 48 is wound around a portion sandwiched between the magnetic flux collecting projections 431 and 432 in the body portion 42. Further, the detection coil 49 is wound around the magnetic flux collecting projection 43, and in this example, the detection coil 49 is composed of two magnetic flux collecting projections 43 (the magnetic flux collecting projections 431 and 432) of the sensor core 41. Among them, a detection coil 491 wound around the magnetic flux collection protrusion 431 and a detection coil 492 wound around the magnetic flux collection protrusion 432 are included. Here, the two detection coils 491 and 492 are wound around the magnetic flux collecting projections 431 and 432 in opposite directions. Further, since the two detection coils 491 and 492 are formed by continuously winding one coil wire around the magnetic flux collecting projections 431 and 432, the two detection coils 491 and 492 are electrically connected in series. It is connected to the. The two detection coils 491 and 492 may be wound around the magnetic flux collecting projections 431 and 432, respectively, and then electrically connected in series.

  In the magnetic sensor element 40 configured as described above, the thickness direction T40 orthogonal to both the width direction W40 and the projecting direction (height direction V40) of the magnetic flux collecting projection 43 is directed to the moving direction X of the medium 2. In the magnetic sensor element 40, the width direction W40 in which the magnetic flux collecting projections 43 (magnetic flux collecting projections 431 and 432) and the detection coils 49 (detection coils 491 and 492) are separated from each other is The medium 2 faces in the width direction Y perpendicular to the moving direction X.

  In the magnetic sensor element 40, an excitation signal composed of an alternating current (see FIG. 3B) is applied to the excitation coil 48 from an excitation circuit 50 described later with reference to FIG. For this reason, as shown in FIG. 3A, a bias magnetic field is formed around the sensor core 41, and a detection waveform signal shown in FIG. Will be output. Here, the detected waveform shown in FIG. 3C is a temporal differential signal of the magnetic flux generated by the excitation signal, and is close to the temporal differential signal of the excitation signal.

  In this example, the sensor core 41 of the magnetic sensor element 40 has a magnetic material layer 41c sandwiched between a nonmagnetic first substrate 41a and a nonmagnetic second substrate 41b, as shown in FIG. It has a structure. In this example, the magnetic material layer 41c is made of a thin plate-like amorphous metal foil made of an amorphous (amorphous) metal magnetic material adhered to one surface of the first substrate 41a by an adhesive layer (not shown). The second substrate 41b is bonded to one surface of the first substrate 41a by an adhesive layer so as to sandwich the magnetic material layer 41c therebetween.

(Configuration of signal processor)
FIG. 4 is a block diagram showing an electrical configuration of the magnetic pattern detection apparatus 1 according to the present invention. The circuit unit 5 shown in FIG. 4 includes an excitation circuit 50 that applies the alternating current shown in FIG. 3B as an excitation signal to the excitation coil 48 of each magnetic sensor element 40, and a signal that is electrically connected to the detection coil 49. And a processing unit 60. The signal processing unit 60 generates a first signal S1 corresponding to the residual magnetic flux density level and a second signal S2 corresponding to the magnetic permeability level from the detection signal output from the detection coil 49. The signal processing unit 60 includes an amplification unit 70 that amplifies the detection signal output from the magnetic sensor element 40, an extraction unit 80 that extracts a peak value and a bottom value from the signal output from the amplification unit 70, and an A / D converter. And a digital signal processing unit 90 having 91. The extraction unit 80 and the digital signal processing unit 90 constitute a magnetic pattern detection unit 100 that detects the magnetic pattern of the medium 2. The amplification unit 70 and the magnetic pattern detection unit 100 are connected via an analog switch 101 and a zero clamp unit 102. It is connected.

  The excitation circuit 50 includes one excitation driver amplifier 51 that receives an excitation signal and a multiplexer 52 that is connected to the subsequent stage of the excitation driver amplifier 51. The excitation circuit 50 amplifies the single-channel excitation signal and then divides it into multi-channel time-division excitation signals that are switched at a constant timing and in a constant sequence. That is, the multiplexer 52 time-divides the amplified amplified excitation signal based on the switching signal and supplies the amplified amplified excitation signal to the excitation coil 48 of each magnetic sensor element 40 at a constant timing and a constant sequence. The switching signal is input from the digital signal processing unit 90 to the multiplexer 52 via the flip-flop 53.

  The amplifying unit 70 includes a multiplexer 71 connected to the plurality of magnetic sensor elements 40 and an amplifier 72 connected to the subsequent stage of the multiplexer 71. The amplifying unit 70 synthesizes the multi-channel detection signals output from the detection coils 49 of the magnetic sensor elements 40 of the magnetic sensor device 20 while switching them at a constant timing and in a constant order, and then amplifies the signals for simple synthesis. One channel time series detection signal is output. That is, the multiplexer 71 connects the magnetic sensor element 40 to which the detection signal is output based on the switching signal to the amplifier 72 from the plurality of magnetic sensor elements 40 at a constant timing and in a constant order. The switching signal is input from the flip-flop 53 to the multiplexer 71.

  The analog switch 101 is for cutting off the supply path 101a of the time series detection signal from the amplification unit 70 to the magnetic pattern detection unit 100 for a predetermined time. The analog switch 101 is controlled based on the switch control signal. When the excitation of the excitation coil 48 of each magnetic sensor element 40 by the time-division excitation signal is started, the analog switch 101 is switched off for a predetermined time including the excitation start time, and the supply path 101a. Is electrically shut off. Thereby, the time-series detection signal output from the amplifying unit 70 indicates a period during which there is a high possibility that noise generated due to switching of the magnetic sensor element 40 is included, that is, the excitation start time of the magnetic sensor element 40. The predetermined time is masked by the OFF state of the analog switch 101. As a result, it is possible to avoid or reduce the time-series detection signal with noise generated when switching the magnetic sensor element 40 from being input to the magnetic pattern detection unit 100, so that the magnetic pattern of the medium 2 can be detected with high accuracy. The switch switching signal is input to the analog switch 101 via the flip-flop 53 and the timing adjustment unit 54.

  The zero clamp unit 102 includes a grounded analog switch 103. The analog switch 103 is controlled based on the switch control signal, and clamps the potential of the supply path 101a to 0 for a predetermined period in which the analog switch 101 is turned off. The switch switching signal is input to the analog switch 103 via the flip-flop 53 and the timing adjustment unit 54.

  The extraction unit 80 includes a clamp circuit 82 and an offset adjustment circuit (output correction unit) 83 that performs an offset adjustment process on the rectified signal (analog sensor output signal from the magnetic sensor) output from the clamp circuit 82. More specifically, the clamp circuit 82 includes a first diode 821 that rectifies the time series detection signal output from the amplification unit 70, and a polarity inversion circuit 822 that performs polarity inversion of the time series detection signal output from the amplification unit 70. And a second diode 823 that rectifies the signal whose polarity is inverted in the polarity inverting circuit 822. Therefore, the offset adjustment circuit 83 includes a first offset adjustment circuit 831 for the rectified signal from the first diode 821 and a second offset adjustment circuit 832 for the rectified signal from the second diode 823.

  Here, the first offset adjustment circuit 831 and the second offset adjustment circuit 832 have the same configuration, and are respectively offset adjustment reference voltage generation circuits (D / A conversion circuits) 831a and 832a, and offset adjustment. Operational reference (adders) 831b and 832b connected to the subsequent stage of the reference voltage generating circuits 831a and 832a. The timer signal and the offset command value (command value) from the digital signal processing unit 90 are input to the offset adjustment reference voltage generation circuits 831a and 832a. When the offset command value is input, an analog addition signal corresponding to the offset command value is output from the offset adjustment reference voltage generation circuits 831a and 832a. The added signal is added to the rectified signal by the operational amplifiers 831b and 832b and output as a corrected output signal (corrected sensor output signal). The offset adjustment processing is to adjust the output level of the addition signal to set the output level of the correction output signal during standby to a predetermined target output level, and the magnetic sensor element 40 that outputs the detection signal This is performed each time the magnetic sensor elements 40 are switched at a constant timing and a constant sequence.

  The extraction unit 80 includes a hold circuit 84 following the offset adjustment circuit 83 and a gain setting unit 85 subsequent to the hold circuit 84. The hold circuit 84 holds the peak value of the correction output signal subjected to the offset adjustment processing from the first offset adjustment circuit 831 and the correction output subjected to the offset adjustment processing from the second offset adjustment circuit 832. And a second peak hold circuit 842 that holds the peak value of the signal. Here, the second offset adjustment circuit 832 receives a signal obtained by inverting the polarity of the signal output from the amplification unit 70 by the polarity inverting circuit 822 and then rectifying the signal by the second diode 823. For this reason, the second peak hold circuit 842 corresponds to a bottom hold circuit that holds the bottom value of the amplified signal output from the amplification unit 70.

  The gain setting unit 85 is held by the gain setting first amplifier 851 (main amplifier) and the second peak hold circuit 842 (bottom hold circuit) for setting the gain of the value held by the first peak hold circuit 841. And a gain setting second amplifier 852 (main amplifier) for setting the gain of the value. The values held by the first peak hold circuit 841 and the second peak hold circuit 842 are set to a predetermined gain and digitally set. The signal is output to the A / D converter 91 of the signal processing unit 90. The gain setting unit 85 receives the timer signal and gain command value from the digital signal processing unit 90. The gain setting unit 85 updates the gain every time the magnetic sensor element 40 is switched based on the timer signal and the gain command value.

  The digital signal processing unit 90 adds the value held by the first peak hold circuit 841 and the value held by the second peak hold circuit 842 to generate the first signal S1; A subtracting circuit 93 that subtracts the value held by the peak hold circuit 841 from the value held by the second peak hold circuit 842 to generate the second signal S2. The digital signal processing unit 90 includes a control signal output unit 94, a hard timer 95 that outputs a timer signal, and addition signal adjustment units 96 and 97.

  The control signal output unit 94 outputs the gain command value to the gain setting unit 85. Further, the control signal output unit 94 outputs a switching control signal that is periodically generated by a software interrupt to the flip-flop 53. The timer signal of the hard timer 95 is input to the flip-flop 53, and the flip-flop 53 outputs this switching control signal to the multiplexer 52 and the multiplexer 71 as a switching signal synchronized with the timer signal.

  Here, the switching signal obtained by synchronizing the switching control signal with the timer signal is input to the analog switch 101 and the analog switch 103 as a switch switching signal via the timing adjustment unit 54. The timing adjustment unit 54 sets a predetermined time for maintaining the analog switch 101 in the off state and maintaining the analog switch 103 in the on state. That is, the control signal output unit 94, the hard timer 95, the flip-flop 53, and the timing adjustment unit 54 constitute a switch control unit that controls the analog switch 101 and the analog switch 103.

  The addition signal adjustment unit (second addition signal adjustment circuit) 96 outputs an offset command value to the offset adjustment reference voltage generation circuits 831a and 832a when the power is turned on or restarted, and performs an offset adjustment process. The time of restart refers to a point in time when the output level of the added signal is lost and the output level of the added signal is not adjusted by operating a reset switch or the like of the apparatus. The addition signal adjustment unit (first addition signal adjustment circuit) 97 is a reference for offset adjustment after the medium 2 passes through the magnetic sensor device 20 and before the next medium 2 passes through the magnetic sensor device 20. An offset command value is output to the voltage generation circuits 831a and 832a to perform offset adjustment processing.

  The digital signal processing unit 90 configured in this manner outputs a first signal S1 and a second signal S2 to a higher-order control unit (not shown), and the higher-order control unit outputs the first signal S1 and the second signal S2. The authenticity of the medium 2 is determined based on the two signals S2. More specifically, the upper control unit associates the first signal S1 and the second signal S2 with the relative position information between the magnetic sensor element 40 and the medium 2, and the comparison pattern recorded in advance in the recording unit. And a determination unit that determines whether the medium 2 is true or false. The determination unit is a predetermined unit based on a program recorded in advance in a recording unit (not shown) such as a ROM or a RAM. Processing is performed to determine whether the medium 2 is true or false.

(Offset adjustment process)
Next, the offset adjustment process will be described in detail with reference to FIGS. Since the offset adjustment process performed via the first offset adjustment circuit 831 and the offset adjustment process performed via the second offset adjustment circuit 832 are the same, the offset adjustment process performed via the first offset adjustment circuit 831 is performed. For the sake of explanation, the description of the offset adjustment processing performed via the second offset adjustment circuit 832 is omitted.

(Offset adjustment processing at power-on and restart)
As shown in FIG. 4, the addition signal adjustment unit 96 that performs offset adjustment processing at power-on and restart includes a command value output unit 961, a binary search unit 962, and a setting unit 963.

  The command value output unit 961 outputs a digital command value for adjusting the output level of the addition signal to the offset adjustment reference voltage generation circuit 831a. The binary search unit 962 compares the output level of the corrected output signal with the target output level, processing for changing the offset command value according to the binary search method, with the first search range between the upper limit value and the lower limit value of the offset command value. The offset command value when the output level reaches the target output level is acquired as an appropriate value. When the appropriate value is acquired by the binary search unit 962, the setting unit 963 maintains the offset command value output from the command value output unit 961 at the appropriate value.

  FIG. 5A is a flowchart of offset adjustment processing by the addition signal adjustment unit 96, and FIG. 5B is a graph showing an example of searching for an appropriate value by the binary search method. The vertical axis of the graph of FIG. 5B is the output level of the correction output signal, and the horizontal axis is the offset command value. As shown in FIG. 5A, when the magnetic pattern detection device 1 is turned on or when the magnetic pattern detection device 1 is restarted, the binary search unit 962 sets the upper limit value of the offset command value. The process of changing the offset command value according to the binary search method and the process of comparing the output level of the corrected output signal with the target output level using the range between the lower limit values as the first search range is repeated in this order (step ST11). An offset command value when the output level reaches the target output level is acquired as an appropriate value (step ST12). When the appropriate value is acquired, the setting unit 963 maintains the offset command value output from the command value output unit 961 to the offset adjustment reference voltage generation circuit 831a at the appropriate value (step ST13). Steps ST11 to ST13 are performed each time the magnetic sensor element 40 is switched at a constant timing and a constant sequence. Then, the offset adjustment processing is completed by performing these steps ST11 to ST13 for the adjustment output signals from all the magnetic sensor elements 40.

  In the example shown in FIG. 5B, when the power is turned on or restarted, the command value output unit 961 outputs the first median value C1 of the upper limit value and the lower limit value of the offset command value to the offset adjustment reference voltage generation circuit 831a. Thus, the output level V1 of the corrected output signal is compared with the target output level V0. In this example, the output level V1 of the corrected output signal is higher than the target output level V0, and in order to set the output level of the corrected output signal to the target output level V0, the output level V1 of FIG. Binary search of the area on the right side of the graph is required. Therefore, the second median value C2 between the first median value and the upper limit value is set as a new offset command value and is output from the command value output unit 961 to the offset adjustment reference voltage generation circuit 831a, and the corrected output signal The output level V2 is compared with the target output level V0.

  At this time, the output level V2 of the corrected output signal is lower than the target output level V0. Therefore, in order to set the output level of the corrected output signal to the target output level V0, the output level V2 of FIG. It is necessary to perform a binary search for the region on the right side of the graph of b) and the region on the left side of the graph of FIG. 5B rather than the second median value C2. Therefore, the third median value C3 between the first median value C1 and the second median value C2 is set as a new offset command value and is output from the command value output unit 961 to the offset adjustment reference voltage generation circuit 831a. The output level V3 of the corrected output signal is compared with the target output level V0.

  At this time, the output level V3 of the corrected output signal is higher than the target output level V0. Therefore, in order to set the output level of the corrected output signal to the target output level V0, the output level V3 of FIG. It is necessary to perform a binary search for the region on the right side of the graph of b) and the region on the left side of the graph of FIG. 5B rather than the second median value C2. Accordingly, the fourth median value C4 between the third median value C3 and the second median value C2 is set as a new offset command value, and is output from the command value output unit 961 to the offset adjustment reference voltage generation circuit 831a. The output level V4 of the correction output signal is compared with the target output level V0.

  In this example, when the fourth median value C4 is set as a new offset command value and is output from the command value output unit 961 to the offset adjustment reference voltage generation circuit 831a, the output level V4 of the correction output signal becomes the target output level V0. Become. Therefore, the offset command value C4 at this time is acquired as an appropriate value, and the offset command value from the command value output unit 961 is maintained at an appropriate value.

  In the offset adjustment process that is performed when the power is turned on or restarted, it is unknown whether the output level of the correction output signal at the start of the offset adjustment process is within the dynamic range, so there is no difference between the offset command value and the correction output signal. It is also unclear whether or not the proportional relationship is established. Therefore, if the offset command value is searched until the output level of the corrected output signal reaches the target output level in accordance with the binary search method, an appropriate value of the offset command value can be obtained in a relatively short time.

(Offset adjustment process performed each time the magnetic pattern of the medium is detected)
As shown in FIG. 4, an addition signal adjustment unit 97 that performs an offset adjustment process every time the magnetic pattern of the medium 2 is detected includes a command value output unit 971, a proportional relationship storage holding unit 972, a difference calculation unit 973, and an appropriate value calculation. Part 974 and setting part 975 are provided.

  The command value output unit 971 outputs a digital command value for adjusting the output level of the addition signal to the offset adjustment reference voltage generation circuit 831a. The proportional relationship storage / holding unit 972 stores and holds a proportional relationship established between the output level of the correction output signal during standby and the offset command value within the dynamic range of the correction output signal. The difference calculation unit 973 calculates the difference between the output level of the corrected output signal and the target output level. The appropriate value calculation unit 974 calculates an appropriate value of the offset command value for setting the output level as the target output level based on the offset command value, the difference, and the proportional relationship output from the command value output unit 971. . When the appropriate value is calculated, the setting unit 975 sets the offset command value output from the command value output unit 971 to an appropriate value. Here, since the command value output unit 971 of the addition signal adjustment unit 97 and the command value output unit 961 of the addition signal adjustment unit 96 have the same function, they are used as one command value output unit 971 as an addition signal. The adjustment unit 96 and the addition signal adjustment unit 97 may be configured to be shared.

  FIG. 6A is a flowchart of offset adjustment processing by the addition signal adjustment unit 97, and FIG. 6B is a graph showing an example of calculating appropriate values. The vertical axis of the graph of FIG. 6B is the output level of the correction output signal, and the horizontal axis is the offset command value. As shown in FIG. 6A, when the magnetic pattern of the medium 2 is detected, the difference calculation unit 973 calculates the difference between the output level of the correction output signal and the target output level (step ST21). Next, the appropriate value calculation unit 974 calculates an appropriate value based on the offset command value at this time point, the calculated difference, and the proportional relationship stored and held in the proportional relationship storage holding unit 972 (step ST22). . When the appropriate value is calculated, the setting unit 975 sets the offset command value output from the command value output unit 971 to the offset adjustment reference voltage generation circuit 831a to an appropriate value (step ST23). Steps ST21 to ST23 are performed each time the magnetic sensor element 40 is switched at a constant timing and a constant sequence. Then, the offset adjustment process is completed by performing these steps ST21 to ST23 for the adjustment output signals from all the magnetic sensor elements 40.

  In the example shown in FIG. 6B, ΔV is calculated as a difference between the output level V1 of the correction output signal and the target output level V0 when the second offset adjustment process is started. The proportionality constant of the proportional relationship is a. Therefore, the change amount ΔC of the offset command value for changing the output level by the amount corresponding to the difference ΔV is ΔV / a. Therefore, the appropriate value is calculated by adding ΔV / a to the current offset command value C1. When the appropriate value is calculated, the offset command value output from the command value output unit 971 is set to an appropriate value.

  In the offset adjustment process after the medium 2 passes through the magnetic sensor device 20 and until the next medium 2 passes through the magnetic sensor device 20, correction is performed by the offset adjustment process performed at power-on or restart. Since the output level of the output signal is once set to the target output level, the corrected output signal at the start of the offset adjustment process is within the dynamic range. Further, since a proportional relationship is established between the offset command value and the correction output signal within the dynamic range, an appropriate value of the offset command value for setting the output level of the correction output signal as the target output level can be calculated. As a result, since the output level of the correction output signal can be set to the target output level in a short time, the next medium 2 passes through the magnetic sensor device 20 after the medium 2 passes through the magnetic sensor device 20. During the short time until the adjustment, the offset adjustment processing can be performed for all of the adjustment output signals from the plurality of magnetic sensor elements 40.

(Detection principle)
FIG. 7 is an explanatory diagram showing characteristics and the like of various magnetic inks formed on the medium 2 in the magnetic pattern detection device 1 according to the present invention. FIG. 8 is an explanatory diagram showing the principle of detecting the presence / absence of a magnetic pattern from the medium 2 on which different types of magnetic patterns are formed in the magnetic pattern detection apparatus 1 according to the present invention.

  First, the principle of determining the authenticity of the medium 2 when the medium 2 moves in the direction of the arrow X1 shown in FIGS. 1 and 2 will be described. In this example, a plurality of types of magnetic patterns having different residual magnetic flux density Br and magnetic permeability μ are formed in the magnetic region 2 a of the medium 2. More specifically, the medium 2 is formed with a first magnetic pattern printed with a magnetic ink containing a hard material and a second magnetic pattern printed with a magnetic ink containing a soft material. Here, the magnetic ink containing the hard material has a high level of residual magnetic flux density Br when a magnetic field is applied, as shown in FIG. 7B1 by the hysteresis loop, such as residual magnetic flux density Br and permeability μ. The permeability μ is low. On the other hand, as shown in FIG. 7C1, the magnetic ink containing the soft material has a low residual magnetic flux density Br when the magnetic field is applied, but has a high permeability μ.

  Therefore, as will be described below, the material of the magnetic ink can be determined by measuring the residual magnetic flux density Br and the magnetic permeability μ. More specifically, since the magnetic permeability μ has a correlation with the coercive force Hc, in this embodiment, the residual magnetic flux density Br and the coercive force Hc are measured, and the residual magnetic flux density Br is measured. And the coercive force Hc differ depending on the magnetic ink (magnetic material). Therefore, the material of the magnetic ink can be determined. The measured values of the residual magnetic flux density Br and the magnetic permeability μ (coercive force Hc) vary depending on the density of the ink and the distance between the medium 2 and the magnetic sensor device 20, but in this embodiment, the magnetic sensor device 20 is the same. Since the residual magnetic flux density Br and the magnetic permeability μ (coercive force Hc) are measured at the position, the material of the magnetic ink can be reliably determined according to the ratio of the residual magnetic flux density Br and the coercive force Hc.

  In the magnetic pattern detection device 1 of the present embodiment, when the medium 2 moves in the direction indicated by the arrow X1 and passes through the magnetic sensor device 20, first, a magnetic field is applied from the first magnetic field application magnet 31 to the medium 2, and the magnetic field The medium 2 after is applied passes through the magnetic sensor element 40. Until then, the detection coil 49 of the magnetic sensor element 40 outputs a signal corresponding to the BH curve of the sensor core 41 shown in FIG. 7 (a2), as shown in FIG. 7 (a3). Accordingly, the first signal S1 output from the adder circuit 92 shown in FIG. 4 and the second signal S2 output from the subtractor circuit 93 are as shown in FIG. 7 (a4).

  Here, when the first magnetic pattern is formed on the medium 2 by the magnetic ink containing a hard material such as ferrite powder, the first magnetic pattern has a high level as shown in FIG. 7 (b1). It has a residual magnetic flux density Br. For this reason, as shown in FIG. 8A 1, when the medium 2 passes through the magnetic field application magnet 30, the first magnetic pattern becomes a magnet by the magnetic field from the magnetic field application magnet 30. For this reason, the signal output from the detection coil 49 of the magnetic sensor element 40 receives a DC bias from the first magnetic pattern as shown in FIG. 7 (b2), and FIG. 7 (b3) and FIG. The waveform changes to (a2). That is, the peak voltage and the bottom voltage of the signal S0 are shifted in the same direction as indicated by arrows A1 and A2, and the shift amount of the peak voltage and the shift amount of the bottom voltage are different. Moreover, the signal S0 changes as the medium 2 moves. Therefore, the first signal S1 output from the subtraction circuit 93 shown in FIG. 4 is as shown in FIG. 7B4, and fluctuates every time the first magnetic pattern of the medium 2 passes through the magnetic sensor element 40. . Here, since the magnetic permeability μ is low in the first magnetic pattern formed by the magnetic ink containing the hard material, the first magnetic pattern has an influence on the shift of the peak voltage and the bottom voltage of the signal S0. It can be considered that only the residual magnetic flux density Br. Therefore, the second signal S2 output from the adder circuit 92 shown in FIG. 4 does not change even when the first magnetic pattern of the medium 2 passes through the magnetic sensor element 40, and the signal shown in FIG. 7 (b4). It is the same.

  On the other hand, when the second magnetic pattern is formed on the medium 2 with magnetic ink containing a soft material such as soft magnetic stainless steel powder, the hysteresis loop of the second magnetic pattern is shown in FIG. As shown, the level of the residual magnetic flux density Br is low through the inside of the hysteresis curve of the first magnetic pattern by the magnetic ink containing the hard material shown in FIG. 7 (b1). For this reason, even after the medium 2 passes through the magnetic field applying magnet 30, the second magnetic pattern has a low residual magnetic flux density Br. However, since the magnetic permeability μ is high, the second magnetic pattern functions as a magnetic material as shown in FIG. Therefore, as shown in FIG. 7C2, the signal output from the detection coil 49 of the magnetic sensor element 40 has an increase in the permeability μ due to the presence of the second magnetic pattern. ) And the waveform shown in FIG. 8 (b2). That is, the peak voltage of the signal S0 is shifted to the higher side as indicated by the arrow A3, while the bottom voltage is shifted to the lower side as indicated by the arrow A4. At that time, the absolute value of the shift amount of the peak voltage and the shift amount of the bottom voltage are substantially equal. Moreover, the signal S0 changes as the medium 2 moves. Therefore, the second signal S2 output from the adder circuit 92 shown in FIG. 4 is as shown in FIG. 7C4, and fluctuates every time the second magnetic pattern of the medium 2 passes through the magnetic sensor element 40. . Here, since the second magnetic pattern formed by the magnetic ink containing the soft material has a low residual magnetic flux density Br, it is the second magnetic pattern that affects the shift of the peak voltage and the bottom voltage of the signal. It can be considered that only the magnetic permeability μ of. Therefore, the first signal S1 output from the subtraction circuit 93 shown in FIG. 4 does not change even when the second magnetic pattern of the medium 2 passes through the magnetic sensor element 40, and the signal shown in FIG. 7 (c4). It is the same.

  Thus, in the magnetic pattern detection device 1 of the present embodiment, the first signal S1 obtained by subtracting the peak value and the bottom value of the signal output from the magnetic sensor element 40 in the subtraction circuit 93 is the residual magnetic flux density level of the magnetic pattern. By monitoring the first signal S1, it is possible to detect the presence and position of the first magnetic pattern formed by the magnetic ink containing the hard material. The second signal S2 obtained by adding the peak value and the bottom value of the signal output from the magnetic sensor element 40 in the adder circuit 92 is a signal corresponding to the magnetic permeability μ of the magnetic pattern. If monitored, it is possible to detect the presence and position of the second magnetic pattern formed by the magnetic ink containing the soft material. Therefore, the presence / absence and formation position of each of the magnetic patterns in the medium 2 having a plurality of types of magnetic patterns having different residual magnetic flux density Br and magnetic permeability μ when a magnetic field is applied are based on both the residual magnetic flux density level and the magnetic permeability level. Can be identified.

  As for the magnetic pattern whose magnetic characteristics are located between the first magnetic pattern and the second magnetic pattern, as shown in FIG. 7 (d1), the hysteresis loop has a hard loop as shown in FIG. 7 (b1). 7 is located in the middle between the hysteresis loop of the magnetic pattern of the material and the hysteresis loop of the magnetic pattern of the soft material shown in FIG. 7C1, so that the signal pattern shown in FIG. 7D4 can be obtained. In addition, the presence or absence and the formation position can be detected.

(Function and effect)
According to this example, the variation in the output level of the correction output signal due to the individual difference of the magnetic sensor device 20 is corrected by the offset adjustment process at the time of power-on and restart. In addition, when detecting the magnetic patterns of a plurality of media 2 in succession, offset adjustment processing is performed every time the magnetic pattern of the media 2 is detected. Therefore, it is possible to avoid or suppress a decrease in the detection accuracy of the magnetic pattern.

  Further, in the multi-channel type magnetic pattern detection device 1 equipped with a plurality of magnetic sensor elements 40, there is a problem that the detection accuracy of the magnetic pattern is lowered when the output level of the detection signal from each magnetic sensor element 40 varies. However, according to this example, every time the channel is switched, the output level of the correction output signal from each magnetic sensor element 40 is set to the target output level. It can be avoided that the magnetic pattern detection accuracy is lowered due to variations in the output level of the output signal.

(Other embodiments)
In the above example, the offset adjustment process is performed every time the magnetic pattern of the medium 2 is detected. However, the offset adjustment process may be performed every time the magnetic patterns of a plurality of media 2 are detected.

  In the above example, the addition signal adjustment unit 96 that performs the offset adjustment process at the time of power-on and restarting searches for an appropriate value of the offset command value using the binary search method. You may search for the appropriate value. FIG. 9A is a flowchart of an offset adjustment process for sequentially searching for offset command values, and FIG. 9B is a graph showing an example of searching for an appropriate value by sequential search. The vertical axis of the graph of FIG. 9B is the output level of the correction output signal, and the horizontal axis is the offset command value. The addition signal adjustment unit 96A of this example includes a sequential search unit 962A instead of the binary search unit 962.

  Here, the sequential search unit 962A sets the offset command value output from the command value output unit 961 to the offset adjustment reference voltage generation circuit 831a to the upper limit value, and thereafter, until the output level reaches the target output level. The process of reducing the offset command value from the command value output unit 961 by a predetermined value and the process of comparing the output level of the corrected output signal with the target output level are repeated in this order, and the output level becomes the target output level. The offset command value can be acquired as an appropriate value. Alternatively, the sequential search unit 962A sets the offset command value output from the command value output unit 961 to the offset adjustment reference voltage generation circuit 831a to the lower limit value, and then commands until the output level reaches the target output level. The process of increasing the offset command value from the value output unit 961 by a predetermined value and the process of comparing the output level of the corrected output signal with the target output level are repeated in this order, and the offset when the output level reaches the target output level. The command value can be acquired as an appropriate value.

  In this example, the sequential search unit 962A sets the offset command value output from the command value output unit 961 to the offset adjustment reference voltage generation circuit 831a as the lower limit value of the offset command value when the power is turned on or restarted. (Step ST31). Next, the process of adding and increasing the offset command value by a predetermined value and the process of comparing the output level of the corrected output signal with the target output level are repeated in this order (step ST32), and the output level becomes the target output level. The offset command value at that time is acquired as an appropriate value (step ST33). When the appropriate value is acquired, the offset command value output from the command value output unit 961 is maintained at the appropriate value (step ST34). Steps ST31 to ST34 are performed each time the magnetic sensor element 40 is switched at a constant timing and a constant sequence. The offset adjustment processing is completed by performing these steps ST31 to ST34 for the adjustment output signals from all the magnetic sensor elements 40.

  In the example shown in FIG. 9B, when the power is turned on or restarted, the lower limit value C1 is output from the command value output unit 961 to the offset adjustment reference voltage generation circuit 831a as the offset command value, and the output level of the correction output signal V1 is compared with the target output level V0. Since the output level V1 of the corrected output signal is different from the target output level V0 at this point, C2 obtained by adding a predetermined value to C1 is set as a new offset command value from the command value output unit 961 and the offset adjustment reference. The voltage is output to the voltage generation circuit 831a, and the output level V2 of the correction output signal is compared with the target output level V0.

  In this example, such a sequential search is performed 11 times, and the output level V12 of the correction output signal when C12 is output as the offset command value from the command value output unit 961 to the offset adjustment reference voltage generation circuit 831a is the target. The output level is V0. Therefore, the offset command value C12 at this time is acquired as an appropriate value, and the offset command value from the command value output unit 961 is maintained at an appropriate value. According to such a sequential search, an appropriate value of the offset command value can be reliably obtained.

1. Magnetic pattern detector, 2. Medium, 2a, magnetic region, 5. Circuit unit, 10. Transport device, 11. Media movement path, 20. Magnetic sensor device, 21. Sensor surface, 22. Slope, 25. Case: 30-Magnetic field application magnet, 31-Magnetic field application first magnet, 32-Magnetic field application second magnet, 35-Permanent magnet, 40-Magnetic sensor element, 41-Sensor core, 41 a-First substrate, 41 b- 2nd board | substrate, 41c * magnetic material layer, 42 * trunk | drum, 43 * magnetic projection part, 44 * protrusion part, 47 * nonmagnetic member, 48 * excitation coil, 49 * detection coil, 50 * excitation circuit, 51・ Excitation driver amplifier, 52 ・ Multiplexer, 53 ・ Flip-flop, 54 ・ Timing adjustment unit, 60 ・ Signal processing unit, 70 ・ Amplification unit, 71 ・ Multiplexer, 72 ・ Amplifier, 80 ・ Extraction unit, 82 ・ Clamp circuit, 83 Offset adjustment circuit, 84 hold circuit, 85 gain setting unit, 90 digital signal processing unit, 91 converter, 92 addition circuit, 93 subtraction circuit, 94 control signal output unit, 95 hard timer, 96 Addition signal adjustment unit (second addition signal adjustment unit), 96A / addition signal adjustment unit, 97 / addition signal adjustment unit (first addition signal adjustment unit), 100 / magnetic pattern detection unit, 101 / analog switch, 101a / supply Road, 102, Zero clamp, 103, Analog switch, 350, Magnetized surface, 431, 432, Protrusion for magnetism, 441, 442, Projection, 491, Detection coil, 492, Detection coil, 821, First Diode, 822, polarity inversion circuit, 823, second diode, 831, first offset adjustment circuit, 831a, 832a, offset adjustment reference voltage Circuit (D / A conversion circuit), 831b, 832b, operational amplifier (adder), 832, second offset adjustment circuit, 841, first peak hold circuit, 842, second peak hold circuit, 851, gain setting first 1 amplifier, 852-second amplifier for gain setting, 961-command value output unit, 962-binary search unit, 962A-sequential search unit, 963-setting unit, 971-command value output unit, 972-proportional relationship memory holding unit 973-Difference calculation unit, 974-Appropriate value calculation unit, 975-Setting unit

Claims (7)

An output correction unit that generates a correction sensor output signal obtained by adding the addition signal to the analog sensor output signal from the magnetic sensor;
A magnetic pattern detection unit that detects a magnetic pattern of the medium based on the correction sensor output signal when the medium passes through the magnetic sensor;
The output level of the correction sensor output signal is adjusted by adjusting the output level of the addition signal after the medium has passed the magnetic sensor and before the next medium passes the magnetic sensor. And a first addition signal adjustment unit that sets a predetermined target output level. In claim 1,
A second addition signal adjustment unit that sets the output level of the correction sensor output signal as the target output level by adjusting the output level of the addition signal at power-on and restart;
The processing speed at which the first addition signal adjustment unit sets the output level of the correction sensor output signal as the target output level is the processing speed at which the second addition signal adjustment unit sets the output level of the correction sensor output signal as the target output level. A magnetic pattern detection apparatus characterized by being faster than a processing speed. In claim 2,
The output correction unit includes a D / A conversion circuit that outputs the addition signal, and an adder that adds the sensor output signal and the addition signal,
The first addition signal adjustment unit includes:
A first command value output unit for outputting a digital command value for adjusting the output level of the addition signal to the D / A conversion circuit;
A proportional relationship storage holding unit that stores in advance a proportional relationship established between the output level of the correction sensor output signal and the command value during standby within the dynamic range of the correction sensor output signal;
A difference calculation unit for calculating a difference between the output level of the correction sensor output signal and the target output level;
Based on the command value output by the command value output unit, the difference, and the proportional relationship, an appropriate value of the command value for setting the output level of the correction sensor output signal as the target output level is determined. An appropriate value calculation unit for calculating,
A magnetic pattern detection device comprising: a first setting unit that sets the command value output from the first command value output unit to the proper value when the appropriate value is calculated. In claim 3,
The second addition signal adjustment unit includes:
A second command value output unit for outputting a digital command value for adjusting the output level of the addition signal to the D / A conversion circuit;
A process for changing the command value output from the second command value output unit in accordance with a binary search method, with the first search range between the upper limit value and the lower limit value of the command value, and output of the correction sensor output signal A binary search unit that repeats the process of comparing the level and the target output level in this order, and acquires the command value when the output level of the correction sensor output signal becomes the target output level, as the appropriate value;
A magnetic pattern detection device comprising: a second setting unit that maintains the command value output from the second command value output unit at the proper value when the proper value is acquired. In claim 3,
The second addition signal adjustment unit includes:
A second command value output unit for outputting a digital command value for adjusting the output level of the addition signal to the D / A conversion circuit;
The offset command value of the second command value output unit is set to an upper limit value, and then output from the second command value output unit until the output level of the correction sensor output signal reaches the target output level. The process of reducing the command value by a predetermined value and the process of comparing the output level of the correction sensor output signal and the target output level are repeated in this order, or the command value of the offset second command value output unit A process of increasing the command value output from the second command value output unit by a predetermined value until the output level of the correction sensor output signal reaches the target output level. The process of comparing the output level of the correction sensor output signal and the target output level is repeated in this order, and the output level of the correction sensor output signal is the target level. A sequential search unit that acquires the instruction value when a force level as an appropriate value,
A magnetic pattern detection device comprising: a second setting unit that maintains the command value output from the second command value output unit at the proper value when the proper value is acquired. In any one of claims 3 to 5,
The magnetic sensor comprises a plurality of magnetic sensors,
The sensor output signal is a signal in which the magnetic sensor to which the sensor output signal is output is sequentially switched at a constant timing from the plurality of magnetic sensors,
The first addition signal adjustment unit and the second addition signal adjustment unit adjust an output level of the correction sensor output signal by adjusting an output level of the addition signal each time the magnetic sensor is switched at the predetermined timing. The magnetic pattern detection device is set to the target output level. In any one of claims 1 to 6,
The magnetic pattern detection apparatus according to claim 1, wherein the predetermined number is one.

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