JP2005351746A - Signal detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect signals with high accuracy from a specimen, under a simple magnetic shield environment, by improving the signal-to-noise ratio. <P>SOLUTION: An object to be inspected (40) is provided with a plurality of sensors (30a-30c). Difference absolute value circuits (50a-50c) determine the absolute values of the differences between pairs of output signals of the sensors. A summing circuit (52) sums up the difference absolute values, to generate a final detection signal (S). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for detecting a signal generated from an object to be inspected, and more particularly to a configuration for reducing the influence of external environmental noise and improving signal detection accuracy. More specifically, the present invention relates to a configuration for improving the magnetic field detection accuracy of a magnetic sensor using a superconducting quantum interference device (SQUID).

  In various fields, a signal from a measurement target is detected to grasp the state of the measurement target, and various necessary processes are performed according to the grasped state.

  In such signal measurement, it is required to accurately detect a signal from an object to be measured while suppressing the influence of disturbance such as noise.

  For example, in the measurement of an electrical signal, when threshold processing (binarization processing) is performed on an electrical signal corresponding to the state of an object to be measured, a reference value is compared with the electrical signal. In this case, by differentially amplifying the electric signal and the reference value, in-phase noise is superimposed on the electric signal and the reference voltage, and the common-mode noise is removed in the differential amplifier.

  However, in the configuration that removes common-mode noise using this differential amplifier, a reference voltage is generated from a target different from the measurement target, and the difference between the signal from the measurement target and the reference voltage is amplified. Noise cannot be removed from the signal waveform itself from the measurement target.

  Further, in a differential amplifier widely used in an electronic circuit or the like, it is generally required to remove common-mode noise as a large performance parameter, and noise removal characteristics are shown as a common-mode noise rejection ratio (CMRR). It is. However, in such a differential amplifier, the signal is compared with a fixed voltage (reference voltage) and the difference is amplified or the input complementary signal is amplified. However, this common-mode noise rejection ratio is a characteristic parameter of the differential amplifier, and only removes the common-mode noise of the signal at the input section of the differential amplifier. In the signal measurement, the signal from the measurement target is detected. The noise component itself generated for the sensor is not removed, so the configuration of the differential amplifier widely used in electronic circuits is used as it is to reduce the noise of the signal generated by the measurement target. I can't.

  In addition, when a noise pattern generated in advance during signal measurement can be predicted, a configuration that generates a prediction noise pattern and subtracts the detection signal from the measurement target by the prediction noise pattern to generate a detection signal, Used in fields such as adaptive noise cancellers. However, such an adaptive noise canceller method can be applied only when a noise pattern is predicted in advance.

  As a sensor that detects a signal generated by such a measurement target, there is a magnetic sensor that detects a magnetic field from the measurement target. As this magnetic sensor, there are various types of sensors such as a gradiometer and a flux gate. As a highly sensitive magnetic sensor, there is a magnetic sensor (SQUID magnetic sensor) using a superconducting quantum interference element (SQUID). This SQUID magnetic sensor is an element having a Josephson coupling that applies a so-called tunnel effect in which an insulator is inserted in a superconducting ring. In the superconducting state, the current flowing through the superconducting ring is quantized, and the magnetic field entering the ring is quantized. This quantized magnetic field is called a magnetic flux, and the minimum magnetic flux Φ0 is 2.07 · 10 ^ (− 15) Weber. Here, the symbol ^ indicates a power.

  In this SQUID magnetic sensor, a bias current slightly exceeding the critical current value of the Josephson coupling portion is applied to the element. The output voltage of the SQUID changes according to the external magnetic field, and the external magnetic field is detected by detecting this voltage change.

  The minimum quantized magnetic flux Φ0 is an extremely small value, and the SQUID can detect a small magnetic field of several tens of femto-Tessler (10 ^ (-14) Tesla) level. Even in the case of a high-temperature SQUID magnetic sensor using a high-temperature superconductor such as an oxide superconductor, a small magnetic field of several tens of subpicotler (10 ^ (-13) Tesla) level can be detected. When such a SQUID magnetic sensor is used, a minute signal of 1 / 10,000,000 or less of the geomagnetism can be captured and used in biomagnetic field detection and the like.

  However, when such a high-sensitivity magnetic sensor is used, the magnetic field to be detected is extremely small, and the influence of environmental magnetic field disturbances such as geomagnetism and commercial power supply is large. It is necessary to suppress and perform magnetic detection. Usually, as represented by a magnetoencephalograph, such a magnetic sensor is installed in a magnetically shielded space such as a magnetic shield room, and the object to be measured (inspected object, hereinafter referred to as the object) The magnetic field is detected by introducing the magnetically shielded space.

  In order to effectively shield such extraneous magnetic noise (environmental magnetic field), generally, a shielding space is often formed using a plurality of plate-like high permeability materials. Japanese Patent Application Laid-Open No. 2003-243874 discloses a configuration for reducing low-frequency magnetic noise in a magnetic shield room. In the configuration disclosed in Patent Document 1, one or a plurality of magnetic sensors for detecting magnetic noise for measuring the amount of magnetic fluctuation are provided on the side surface of an electromagnetic shield wall constituting a magnetic shield room. In accordance with the output signal of the magnetic sensor for detecting magnetic noise, one or a plurality of noise canceling compensating electromagnetic coils are provided for generating a compensating magnetic field by flowing current independently so as to suppress magnetic fluctuation in the magnetic shield room. In the configuration disclosed in Patent Document 1, a magnetic field is actively generated internally to compensate for fluctuations in the external magnetic field in accordance with a so-called active magnetic shield system, thereby canceling out the noise magnetic field.

  Further, when performing magnetic field detection on each subject by exchanging subjects one after another, a magnetic shielding device having an opening in at least a part is used because a closed magnetic shielding space cannot be used. The However, since an opening is provided in the magnetic shielding device, the magnetic shielding performance is deteriorated, and the influence of noise from the external environment on the magnetic sensor disposed inside cannot be completely suppressed.

  An example of the configuration of a superconducting magnetic shield device having this opening is shown in Patent Document 2 (Japanese Patent Laid-Open No. 2003-339659). In the configuration shown in Patent Document 2, superconducting rings are arranged on the entrance side and the exit side of the transport path for transporting the subject. A magnetic shield composed of a cylindrical ferromagnetic material having a surface parallel to the axial direction of the superconducting ring is disposed. A magnetic sensor is disposed in the hollow cylindrical magnetic shield, and the direction of the detection coil surface of the magnetic sensor is disposed in parallel to the axis of the superconducting ring.

This Patent Document 2 aims to realize a small and lightweight magnetic shield with high openness by providing superconducting rings at the entrance and exit of the conveyance path to prevent the intrusion of an external environmental magnetic field.
JP 2003-243874 A JP 2003-339659 A

  In the case of the configuration of the active magnetic shield shown in Patent Document 1 described above, a magnetic sensor for detecting magnetic field noise is provided on the side wall of the electromagnetic shield wall constituting the magnetic shield room, and according to the output signal of the magnetic sensor for detecting magnetic field noise. The current supplied to the magnetic coil for compensating the magnetic field noise is adjusted to cancel the noise magnetic field. However, there is a time difference between the generation of the noise magnetic field due to the phase shift in the compensation system and the cancellation of the noise magnetic field, and it is difficult to accurately detect the noise magnetic field. Further, depending on the arrangement position of the noise detection magnetic sensor and the compensation electromagnetic coil, it may not be possible to accurately generate a compensation magnetic field that cancels out the magnetic field noise internally, and these noise detection magnetic sensor and compensation electromagnetic coil may not be generated. There arises a problem that the adjustment of the mounting position is troublesome.

  In addition, by configuring a simple magnetic shield with this active magnetic shield alone, it eliminates the need for a magnetically shielded room that uses high-permeability materials such as expensive permalloy, and realizes a magnetic shield at low cost. Has also been proposed. However, when such an active magnetic shield alone is used, an opening can be provided in the magnetic shield, and it is possible to continuously detect the magnetic field of the subject. . Further, the compensation coil for noise cancellation generally performs magnetic field compensation in a space as large as a magnetic shield room, which increases the scale of the magnetic detection device. Further, when continuously inspecting, since the subject passes through the active magnetic shield, the magnetic field generated by the active magnetic shield itself affects the subject, and the magnetic field generated by the subject is accurately detected. The problem of being unable to do so occurs.

  In the configuration disclosed in Patent Document 2, superconducting rings are arranged on the entrance side and the exit side of the subject transport path, and the superconducting rings are used to suppress the intrusion of an external magnetic field. In this case, an opening is provided in the transport path, and it is possible to continuously detect the magnetic field by transporting the subject. However, it is necessary to dispose a superconducting ring having an inner diameter that allows the subject to pass through at each of the entrance and the exit of the transport path, and the apparatus becomes expensive. In the configuration shown in Patent Document 2, an electric current flows through the superconducting ring due to an external magnetic field, and an external magnetic shielding is realized by utilizing the complete diamagnetic characteristic of the superconductivity. Therefore, in order to arrange this superconducting ring, a cooling device is required separately from the cooling device for the SQUID magnetic sensor for measuring the magnetic field of the subject.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a signal detection device capable of accurately detecting a signal to be measured while suppressing the influence of external environmental noise with a simple configuration.

  A specific object of the present invention is to provide a magnetic detection device capable of detecting a magnetic field generated by a subject with high accuracy and suppressing the influence of a strong external magnetic field with a simple configuration.

  The signal detection device according to the present invention includes a plurality of sensors that individually detect signals from the measurement target, and a signal processing detection unit that detects the signals of the measurement target in accordance with output signals of the plurality of sensors. Prepare. The signal processing detection means includes difference means for taking at least one pair of differences between the output signals of the plurality of sensors.

  In-phase noise is commonly applied to a plurality of sensors, and therefore, the same noise component appears in each of the sensor output signals. By taking the difference between the pair of output signals of these sensors, the noise component can be removed. In particular, when the distance between the object to be inspected in the same subject and each sensor is different, the intensity of the signal from the object to be inspected to each sensor is different, and the intensity of the target detection signal of each sensor is also different accordingly. Even if it is taken, the reduction of the target detection signal is suppressed, and the signal-to-noise ratio can be improved.

  Therefore, even if a magnetic shield with a simple configuration is used, it is possible to detect a signal generated by the object to be inspected with high accuracy while suppressing the influence of environmental noise.

[Embodiment 1]
FIG. 1 schematically shows a structure of a magnetic detection device according to the first embodiment of the present invention. In FIG. 1, the magnetic detection device includes a magnetic detector body 2 disposed in a magnetic shield 1. The magnetic shield 1 has openings 3 a and 3 b for carrying the subject 10.

  The magnetic detector body 2 includes a high-temperature superconducting SQUID magnetic sensor and a vacuum heat insulating container that holds a coolant for maintaining the magnetic sensor in a superconducting state. A plurality of magnetic sensors are arranged in the magnetic detector main body 2, and each detects a magnetic field from the subject 10 (object to be inspected) individually. By disposing a plurality of magnetic sensors, as will be described later, it is possible to perform processing for removing signal components due to disturbance signals included in the magnetic sensor output signal.

  The conveyance path 4 passes through the openings 3a and 3b of the magnetic shield 1, the subject 10 is carried into the magnetic shield 1, and the subject 10 is carried out after the examination. By transporting the subject 10 through the openings 3a and 3b, for example, the subject can be continuously inspected in the product line.

  The conveyance path 4 includes a belt 5 on which the subject 10 is placed, drive wheels 6 a and 6 b that drive the belt 5, and a roller 7 that smoothly drives the belt 5.

  A cooling device 15 for supplying a coolant to the magnetic detector main body 2 is disposed inside the magnetic shield 1.

  The object to be inspected of the subject 10 is a magnetic foreign material, and a magnetism device 12 is provided in the vicinity of the carry-in opening 3a of the magnetic shield 1 in order to magnetize the magnetic foreign material and reliably detect the magnetic foreign material. It is done. The magnetism device 12 includes magnets 12a and 12b arranged so as to sandwich the subject 10 from above and below. These magnets 12a and 12b are composed of strong permanent magnets or electromagnets such as rare earth magnets, generate a direct-current magnetic field with a constant strength, and reliably expose the object to be examined (magnetic foreign matter) contained in the subject 10. Make it. The transport path 4 and the magnetic shield 1 are disposed on the support base 22.

  A control / display / detection device 20 is provided to control the detection operation of the magnetic sensors of the conveyance path 4 and the magnetic detector body 2. The control / display / detection device 20 processes the output signal of the magnetic sensor in the magnetic detector main body 2, displays the processing result, and detects the presence or absence of magnetic foreign matter. As the processing of the output signal of the magnetic sensor, as will be described in detail later, the influence of the disturbance signal such as the environmental magnetic field can be accurately suppressed by performing the processing of taking the difference between the output signals of the magnetic sensor.

  FIG. 2 is a diagram schematically showing the configuration of the magnetic detector main body 2 shown in FIG. The magnetic detector main body 2 includes a vacuum heat insulating container (liquid nitrogen dewar) 25 that forms a vacuum heat insulating layer 26 by maintaining a vacuum state between the outer wall and the inner wall, and the subject 10 and the bottom wall at the bottom of the vacuum heat insulating container 25. The magnetic sensor 30 arrange | positioned so that it may oppose via is included.

  In the first embodiment, the magnetic sensor 30 is a SQUID magnetic sensor that uses a high-temperature superconducting ring. The SQUID magnetic sensor 30 transmits and receives signals, bias currents, and the like to and from the drive circuit included in the control / display / detection device 20 shown in FIG.

  A plurality of SQUID magnetic sensors 30 are arranged in the vacuum heat insulating container 25. However, one magnetic sensor 30 is representatively shown in FIG. The magnetic sensor 30 detects a magnetic field H from an object to be inspected (magnetic foreign matter) 40 included in the subject 10 and transmits a voltage signal corresponding to the detected magnetic field to the drive circuit via the wiring 34.

  FIG. 3 is a diagram schematically showing an example of the arrangement of the magnetic sensors 30 in the magnetic detector main body 2 shown in FIG. In FIG. 3, as the SQUID magnetic sensor 30, three SQUID magnetic sensors 30a, 30b and 30c are arranged. These magnetic sensors 30a to 30c are arranged at a predetermined interval in alignment in a direction (Y direction) orthogonal to the transport direction (X direction) of the subject 10. When the object to be inspected (magnetic foreign matter) 40 is conveyed, for example, in the vicinity immediately below the sensor 30b, the distance between the sensor 30b and the subject to be inspected (hereinafter simply referred to as magnetic foreign matter) 40, and the sensors 30a and 30c, respectively. And the magnetic foreign matter 40 are different in distance. Using the difference in distance between each of these sensors 30a-30c and the magnetic foreign object 40, the difference between the output signals of the sensors 30a-30c is obtained, and the signal component corresponding to the magnetic field component from the magnetic foreign object 40 is canceled out. Is suppressed.

  As shown in FIG. 1, the magnetic shield 1 is provided with openings 3 a and 3 b for transporting the subject 10. The SQUID magnetic sensor can detect a minute signal of 1 / 10,000,000 or less of geomagnetism. Accordingly, an external environmental magnetic field entering from the openings 3a and 3b of the magnetic shield 1 is similarly detected, and a minute signal generated by the inspection target (magnetic foreign matter) is converted into a disturbance signal such as an external environmental magnetic field. (Hereinafter simply referred to as environmental noise) may not be distinguished.

  However, as shown in FIG. 3, by arranging a plurality of SQUID magnetic sensors 30a-30c and obtaining the difference between the output signals of these sensors 30a-30c, the influence of environmental noise can be offset. That is, environmental noise such as noise from the earth's magnetic field, elevator and vehicle, and noise from the commercial power source is generated from a signal source at a distance sufficiently wider than the distance between the sensors 30a-30c. The environmental noise detected by each 30c has almost the same intensity. Therefore, this environmental noise component can be reduced by taking a difference between the signals detected by these sensors 30a-30c.

  FIG. 4 is a diagram schematically showing a configuration of a drive circuit (signal processing detection unit) included in the control / display / detection device 20 shown in FIG. In FIG. 4, the control / display / detection circuit 20 includes, as signal detection processing units, differential absolute value circuits 50a-50c provided corresponding to the pairs of magnetic sensors 30a-30c, and the differential absolute value circuit 50a. A summation circuit 52 that generates the final detection signal S by obtaining the sum of the output signals of −50c is included.

  The difference absolute value circuit 50a obtains the difference absolute value | S1-S2 | of the output signals S1 and S2 of the magnetic sensors 30a and 30b. The difference absolute value circuit 50b obtains the difference absolute value | S2-S1 | of the output signals S2 and S3 of the magnetic sensors 30b and 30c. The difference absolute value circuit 50c obtains the difference absolute value | S3-S1 | of the output signals S1 and S3 of the magnetic sensors 30a and 30c.

  The summing circuit 52 adds the output signals of these difference absolute value circuits 50a-50c to generate the final detection signal S. Therefore, the final detection signal S is expressed by the following equation.

S = | S1-S2 | + | S2-S3 | + | S3-S1 |
Here, the magnetic field detected by the magnetic sensors 30a-30c is a very small magnetic field, and the sensor output voltage is very small. Therefore, the output voltages S1-S3 are generated by integrating and amplifying the output voltages of these magnetic sensors 30a-30c. However, although the configuration of the integrating circuit and the amplifying circuit for preprocessing these signal voltages is not shown, a voltage signal corresponding to the detected magnetic field is generated using a normal FLL circuit (flux-locked loop circuit). The

  Now, as shown in FIG. 4, a state is considered in which magnetic fields H1, H2, and H3 are respectively applied to the magnetic sensors 30a to 30c from the test object 40 of the subject. Magnetic field strength is inversely proportional to the cube of distance. Accordingly, the distances from the object 40 to be inspected to the magnetic sensors 30a-30c are different, and therefore the magnetic fields H1, H2, and H3 detected by the magnetic sensors 30a-30c have different intensities.

  On the other hand, the disturbance signal NZ caused by the environmental noise is given from the outside of the magnetic shield 1, and the distance from the signal generation source is longer than the interval between the magnetic sensors 30a-30c. Therefore, the disturbance signal NZ is supplied to the magnetic sensors 30a to 30c with a substantially uniform intensity within the magnetic shield. Therefore, the output signals S1, S2 and S3 of these magnetic sensors 30a-30c include noise components corresponding to the disturbance signal NZ having the same magnitude. The output signals S1-S3 of these magnetic sensors 30a-30c include signal components corresponding to the strengths of the magnetic fields H1, H2, and H3, respectively, and each target detection signal component (excluding noise components from the output signal). Signal component) is different in size.

  Therefore, by performing the difference absolute value processing in each of the difference absolute value circuits 50a-50c, the noise component corresponding to the disturbance signal NZ is canceled out, and the difference between the magnetic fields H1, H2, and H3 supplied from the inspection target 40, respectively. A signal component corresponding to is generated.

  In these difference absolute value circuits 50a-50c, the absolute value of the difference value is obtained, whereby the signal component can be amplified by the addition process in the next stage, and the detection accuracy can be improved. Further, by obtaining the absolute difference value, it is possible to prevent the state where the reverse sign signal is added regardless of the position of the object 40 to be inspected and the difference method in each of the magnetic sensors 30a-30c. Thus, an equivalent amplification operation can be realized.

  Note that the differences (S1-S2) and (S1-S3) may be obtained, and the sum of these difference values may be obtained by an adding circuit. Similarly, the disturbance signal NZ component can be canceled and the signal from the object to be inspected can be amplified. In this case, the final detection signal S is expressed by the following equation.

S = (S1-S2) + (S1-S3) = 2 · S1- (S2 + S3)
However, also in this case, depending on the position of the object to be inspected, the sign of the difference values (S1-S2) and (S1-S3) may be reversed, and a state where the signal component is reduced may occur. Accordingly, by deriving and adding the difference absolute values | S1-S2 | and | S1-S3 |, it is possible to prevent the target signal component from being reduced regardless of the position of the inspection target and the difference generation method. And the signal-to-noise ratio can be improved.

  Note that the differential absolute value circuits 50a-50c are configured to use an operational amplifier in order to perform processing in an analog manner, and similarly to the summing circuit 52, use an operational amplifier. Can do.

  Further, when the control / display / detection circuit is configured by a computer terminal or the like, the signal is processed digitally, and the difference absolute value processing and the addition (summation) processing are performed by software or software in the computer terminal. It may be executed digitally using an arithmetic processor.

  In the above configuration, as the magnetic sensor 30, three magnetic sensors 30a to 30c are arranged in alignment in a direction orthogonal to the transport direction of the subject. However, the number of the magnetic sensors 30 may be four or more, and a configuration in which a difference absolute value is obtained and added for each pair of magnetic sensors or for at least two pairs may be used. In this case, it is not particularly required to obtain absolute difference values for all pairs.

  FIG. 5 shows an example of the detection result of the magnetic detection device according to the first embodiment of the present invention. In FIG. 5, the horizontal axis represents time (seconds), and the vertical axis represents detected magnetic field strength (Tesla). In FIG. 5, a magnetic field intensity detection signal of actual data (for example, output signal S2 of sensor 30b) before performing the difference process is shown as an example.

  Regarding the detection result of FIG. 5, the measurement condition indicates the detection result of a 1.2 mmφ stainless steel (SUS304) piece present in the subject. Stainless steel pieces of 5 mm, 4 mm, 3 mm, and 2 mm in length are used as objects to be inspected, and three SQUID magnetic sensors 30a, 30b, and 30c (see FIG. 4) are used as sensors. These magnetic sensors 30a, 30b, and 30c are arranged at a distance of 200 mm from each other and aligned in a direction perpendicular to the subject transport direction. An object to be inspected (magnetic foreign matter) 40 is detected at a position 240 mm away from the position of the sensor 30b immediately below the central magnetic sensor 30b. The stainless steel piece is magnetized by the magnetizing device shown in FIG.

  In FIG. 5, the peak at the time point of 10 seconds corresponds to the detection of a stainless steel piece having a length of 5 mm. For the detection signal of stainless steel pieces with a length of 4 mm or less, the magnitude of the disturbance signal and the detection signal intensity of each stainless steel piece are of the same level, and noise and detection signals cannot be distinguished, and their presence should be detected. I can't.

  FIG. 6 is a diagram illustrating a result of deriving a final detection signal by performing a process of obtaining a difference value and an absolute value thereof based on the measurement result illustrated in FIG. In FIG. 6 as well, the horizontal axis represents time (seconds), and the vertical axis represents magnetic field strength (Tesla). Since the difference is an absolute value, both the positive peak and the negative peak of the actual data appear as positive peaks, and the detected magnetic field intensity is also amplified by the summation process.

  As shown in FIG. 6, the disturbance signal component caused by the environmental noise is reduced, and the stainless steel piece having a length of 2 mm is detected more clearly than the disturbance signal caused by the environmental noise. The small peak 40 seconds before this time is an unintended magnetic foreign substance contained in the conveyor. Such a minute magnetic field can be detected with a high signal-to-noise ratio, and a highly accurate magnetic field can be detected.

  Therefore, as shown in FIG. 6, by obtaining the magnetic field of the sum of absolute differences and using it as the final detection signal S, it is possible to reliably suppress the influence of external noise such as an environmental magnetic field and accurately The signal from the object to be inspected can be detected.

  In the above description, a high temperature superconducting SQUID using an oxide superconductor is used as the magnetic sensor. However, even if other magnetic sensors such as a fluxgate and a cladometer are used as this magnetic sensor, signals generated from the same inspection object are detected by a plurality of sensors, and By obtaining the difference absolute value of the output signal, the detection operation can be performed while suppressing the influence of the disturbance signal.

  Therefore, when inspecting meat and other food products in the product line, an opening is provided in the magnetic shield for transporting the subject, and even when the magnetic shield is incomplete, accurate magnetic field detection can be performed. High-precision magnetic field detection can be performed using a simple magnetic shield.

  In the magnetic shield, two openings are provided at the front and rear along the transfer direction in order to load and unload the subject into the magnetic shield using the transfer path. However, only one opening portion of the magnetic shield may be provided, and the subject may be carried in and out through the one opening portion.

  Further, more generally, a sensor that detects a signal generated by the inspection target object is also used to obtain the sum of absolute differences by using the same technique, thereby obtaining the S of the signal from the inspection target object. The signal ratio can be accurately detected by improving the / N ratio.

  Further, the magnetic field detection target may not be an inspection target such as detection of a magnetic foreign substance, but may be a biomagnetic field.

  The sensor may generally be a sensor that detects the state of the measurement target using the sensor. Therefore, the target is not an inspection target in which normality / abnormality is detected, For example, it may be a measurement object whose state is measured, such as heat.

  In general, the present invention can be applied to a signal detection device that detects a signal generated by an object to be measured. In particular, the present invention can be applied to a magnetic detection device that detects a weak signal using a SQUID magnetic sensor, and a magnetic detection device that can perform product inspection on the spot in a product line or the like is realized. be able to.

It is a figure which shows roughly the whole structure of the magnetic detection apparatus according to Embodiment 1 of this invention. It is a figure which shows schematically the structure of the magnetic detector main body shown in FIG. It is a figure which shows roughly an example of arrangement | positioning of the sensor contained in the magnetic detector main body shown in FIG. It is a figure which shows roughly the structure of the signal processing part in the control / display / detection apparatus shown in FIG. It is a figure which shows the actual data detection result of the magnetic detection apparatus in Embodiment 1 of this invention. It is a figure which shows the result of the difference absolute value process of the magnetic detection apparatus in Embodiment 1 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Magnetic shield, 2 Magnetic detector main body, 20 Control, display, detection apparatus, 30, 30a, 30b, 30c Magnetic sensor, 40 to-be-inspected object, 50a, 50b, 50c Difference absolute value circuit, 52 Sum total circuit.

Claims (6)

Each includes a plurality of sensors that individually detect signals from the measurement target, and a signal processing detection unit that detects the signals of the measurement target in accordance with output signals of the plurality of sensors. A signal detection apparatus comprising difference means for taking at least one pair of differences of output signals of the plurality of sensors. The plurality of sensors includes three or more sensors,
The difference means includes means for determining a difference between at least two possible output signals of the plurality of sensors,
The signal detection apparatus according to claim 1, wherein the signal processing detection unit further includes a summation unit for obtaining a sum of output signals of the difference unit.   The signal detection device according to claim 2, wherein the difference means derives an absolute value of a difference between a pair of output signals of the plurality of sensors.   The signal detection device according to claim 1, wherein each of the sensors detects a magnetic field from the measurement target. Each of the sensors is a magnetic sensor using a high-temperature superconducting quantum interference element,
The signal detection device according to claim 1, wherein each of the sensors is disposed in a magnetic shield for shielding from an environmental magnetic field, and the measurement target is disposed in the magnetic shield at the time of detection.   Each of the sensors is a magnetic sensor using a high-temperature superconducting quantum interference element, and has an opening for carrying the object to be inspected, and shields the sensor and the object to be measured at the time of inspection from an environmental magnetic field. The signal detection device according to claim 1, wherein the signal detection device is disposed in a magnetic shield for performing the operation.

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