Magnetic field detection device, sensor system, and program

Abstract

An objective of the present invention is to detect a magnetic field within a detectable range even when a disturbance magnetic field exceeding the detectable range is applied.　A magnetic field detection device disclosed herein comprises: a magnetic sensor that detects a magnetic field; a magnetic field application unit that applies a bias magnetic field to the magnetic sensor; and a range adjustment unit that adjusts the detectable range of the magnetic sensor on the basis of the output of the magnetic sensor when the bias magnetic field is applied. The magnetic field detection device may also comprise: a bias setting unit by which the bias magnetic field applied to the magnetic sensor is set in a detectable range of the magnetic sensor on the basis of the result of the adjustment by the range adjustment unit; and a sensing execution unit for causing the magnetic sensor to execute sensing within the range set by the bias setting unit.

Description

Magnetic field detection device, sensor system, and program

[0001] The present technology relates to a magnetic field detection device, a sensor system, and a program. Specifically, the present technology relates to a magnetic field detection device, a sensor system, and a program capable of applying a bias magnetic field.

[0002] In magnetic field detection devices, there is a technique for canceling the influence of geomagnetism as the detection sensitivity is improved. For example, a technique is disclosed in which a cancellation signal is generated based on the frequency component of an output signal corresponding to a magnetic field, and a cancellation magnetic field of a magnetic field detection device is applied using the cancellation signal (see, for example, Patent Document 1).

[0003] International Publication No. 2017 / 077870

[0004] However, in the above-described conventional technology, when the range detectable by a magnetic sensor is narrower than the geomagnetism, the output signal saturates due to the geomagnetism. For this reason, it is impossible to accurately detect the geomagnetism, and there is a risk that the geomagnetism cannot be canceled.

[0005] The present technology has been created in view of such a situation, and an object thereof is to enable detection of a magnetic field within a detectable range even when an external magnetic field exceeding the detectable range is applied.

[0006] The present technology has been made to solve the above-described problems. A first aspect thereof is a magnetic field detection device including a magnetic sensor that detects a magnetic field, a magnetic field application unit that applies a bias magnetic field to the magnetic sensor, and a range adjustment unit that adjusts a detectable range of the magnetic sensor based on an output of the magnetic sensor when the bias magnetic field is applied. Thereby, even when the detectable range of the magnetic sensor is narrower than the external magnetic field, the effect that the detectable range of the magnetic sensor is adjusted is brought about.

[0007] Furthermore, in the first aspect, the system may include a bias setting unit that sets the bias magnetic field applied to the magnetic sensor to a range detectable by the magnetic sensor based on the adjustment result by the range adjustment unit, and a sensing execution unit that causes the magnetic sensor to perform sensing within the range set by the bias setting unit. This provides the effect that sensing can be performed within the range detectable by the magnetic sensor, even when the range detectable by the magnetic sensor is narrower than the disturbance magnetic field, without requiring a magnetic shield.

[0008] Furthermore, in the first aspect, the bias setting unit may set the bias magnetic field based on the adjustment result by the range adjustment unit so as to cancel out the disturbance magnetic field around the magnetic sensor. This results in the effect of canceling out the disturbance magnetic field even when the range detectable by the magnetic sensor is narrower than the disturbance magnetic field.

[0009] Furthermore, in the first aspect, the bias setting unit may set the bias magnetic field based on the output of the magnetic sensor to which the bias magnetic field is applied, so as to cancel the disturbance magnetic field. This eliminates the need for a magnetic sensor dedicated to detecting the disturbance magnetic field while still providing the effect of canceling the disturbance magnetic field.

[0010] Furthermore, in the first aspect, the system may include a gyro sensor and a prediction unit that predicts changes in the disturbance magnetic field around the magnetic sensor based on the detection results of the gyro sensor, and the range adjustment unit may control the bias magnetic field applied to the magnetic sensor based on the prediction results of the prediction unit. This results in a narrower adjustment range for the detectable range of the magnetic sensor.

[0011] Furthermore, in the first aspect, a high-pass filter may be provided to attenuate the low-frequency components of the output of the magnetic sensor. This has the effect of reducing the cancellation error of the output of the magnetic sensor.

[0012] Furthermore, in the first aspect, the magnetic sensor may detect the magnetic field based on magnetoresistance. This results in the generation of magnetic field data based on voltage signal processing.

[0013] Furthermore, in the first aspect, the range adjustment unit may adjust the detectable range of the magnetic sensor based on the change in magnetoresistance. This results in the detection range of the magnetic sensor being adjusted based on the signal processing of the voltage value.

[0014] Furthermore, in the first aspect, the range adjustment unit may adjust the saturation region of the magnetic sensor based on the change in magnetoresistance, control the bias magnetic field based on the adjustment result of the saturation region, and adjust the detectable range of the magnetic sensor. This results in the ability to adjust the detectable range of the magnetic sensor based on voltage signal processing, even when the range detectable by the magnetic sensor is narrower than the disturbance magnetic field.

[0015] Furthermore, in the first aspect, the range adjustment unit may control the bias magnetic field based on the control of the current flowing through the magnetic field application unit. This results in the bias magnetic field being controlled based on signal processing.

[0016] Furthermore, in the first aspect, the range adjustment unit may set the bias magnetic field to be greater than the absolute value of the Earth's magnetic field, reduce the current flowing to the magnetic field application unit when the saturation region of the magnetic sensor is detected, and adjust the detectable range of the magnetic sensor based on the change in the magnetoresistance of the magnetic sensor when the current flowing to the magnetic field application unit is reduced. This results in the ability to adjust the detectable range of the magnetic sensor based on voltage signal processing, even when the range detectable by the magnetic sensor is narrower than the disturbance magnetic field.

[0017] Furthermore, in the first aspect, the range adjustment unit may control the current flowing to the magnetic field application unit based on binary search. This results in faster adjustment of the range detectable by the magnetic sensor, even when the range detectable by the magnetic sensor is narrower than the disturbance magnetic field.

[0018] Furthermore, in the first aspect, the magnetic sensor and the range adjustment unit may be integrated into a semiconductor chip. This results in faster data processing when adjusting the detectable range of the magnetic sensor.

[0019] Furthermore, in the first aspect, the magnetic sensor may be integrated in an array on the semiconductor chip. This results in the averaged noise contained in the output of the magnetic sensor.

[0020] Furthermore, the second aspect is a sensor system comprising: a magnetic sensor for detecting biomagnetism; a magnetic field application unit for applying a bias magnetic field to the magnetic sensor; a range adjustment unit for adjusting the detectable range of the magnetic sensor based on the output of the magnetic sensor when the bias magnetic field is applied; a bias setting unit for setting the bias magnetic field applied to the magnetic sensor to a detectable range of the magnetic sensor based on the adjustment result by the range adjustment unit; and a sensing execution unit for causing the magnetic sensor to perform sensing within the range set by the bias setting unit. This results in the ability to sense biomagnetism within the detectable range of the magnetic sensor, even when biomagnetism is weak, without the need for magnetic shielding.

[0021] Furthermore, in a second aspect, the biomagnetic field may be brain magnetism or cardiac magnetism. This allows brain magnetism or cardiac magnetism to be sensed even when the range detectable by the magnetic sensor is narrower than the disturbance magnetic field, without the need for magnetic shielding.

[0022] Furthermore, the third aspect is a program that causes the computer to perform the steps of applying a bias magnetic field to the magnetic sensor and adjusting the detectable range of the magnetic sensor based on the output of the magnetic sensor when the bias magnetic field is applied. This ensures that even when the detectable range of the magnetic sensor is narrower than the disturbance magnetic field, the detectable range of the magnetic sensor is adjusted according to the application.

[0023] Furthermore, in a third aspect, the computer may be instructed to perform the steps of setting the bias magnetic field applied to the magnetic sensor to the range detectable by the magnetic sensor based on the adjustment result of the detectable range of the magnetic sensor, and causing the magnetic sensor to perform sensing within the detectable range of the magnetic sensor. This eliminates the need for magnetic shielding, even when the range detectable by the magnetic sensor is narrower than the disturbance magnetic field, and allows sensing to occur within the detectable range of the magnetic sensor based on the application.

[0024] This is a block diagram showing an example configuration of a magnetic field detection device according to the first embodiment. This is a circuit diagram showing an example configuration of a magnetic field detection device according to the first embodiment. This is a diagram showing an example of operation of a magnetic field detection device according to the first embodiment. This is a flowchart showing an example of operation of a magnetic field detection device according to the first embodiment. This is a diagram showing another example of adjusting the bias magnetic field of a magnetic field detection device according to the first embodiment. This is a block diagram showing an example configuration of a magnetic field detection device according to the second embodiment. This is a perspective view showing an example configuration of a magnetic field detection device according to the third embodiment. This is a block diagram showing an example of hardware configuration of a magnetic field detection device according to the fourth embodiment. This is a block diagram showing an example configuration of a sensor system to which a magnetic field detection device according to the fifth embodiment is applied.

[0025] The following describes embodiments for implementing this technology. The description will proceed in the following order: 1. First Embodiment (An example of adjusting the detectable range of a magnetic sensor based on the output of the magnetic sensor when a bias magnetic field is applied) 2. Second Embodiment (An example of predicting changes in the disturbance magnetic field around the magnetic sensor based on the detection result of a gyro sensor, and setting the initial value for adjusting the bias magnetic field applied to the magnetic sensor during sensing based on the predicted value) 3. Third Embodiment (An example of integrating a configuration that adjusts the detectable range of a magnetic sensor based on the output of the magnetic sensor when a bias magnetic field is applied onto a semiconductor chip) 4. Fourth Embodiment (An example of having a computer perform the process of adjusting the detectable range of a magnetic sensor based on the output of the magnetic sensor when a bias magnetic field is applied) 5. Fifth Embodiment (An example of applying a magnetic field detection device that adjusts the detectable range of a magnetic sensor based on the output of the magnetic sensor when a bias magnetic field is applied to biomagnetic detection)

[0026] <1. First Embodiment> Figure 1 is a block diagram showing an example configuration of a magnetic field detection device according to the first embodiment.

[0027] In the figure, the magnetic field detection device 100 adjusts the detectable range of the magnetic sensor 111 based on the output of the magnetic sensor 111 when a bias magnetic field BM is applied to the magnetic sensor 111 from the magnetic field application unit 116.

[0028] The magnetic field detection device 100 includes a magnetic sensor 111, a resistance-to-voltage conversion circuit 112, an analog-to-digital (AD) converter 113, a high-pass filter 114, a control unit 115, and a magnetic field application unit 116.

[0029] The magnetic sensor 111 detects a magnetic field. The magnetic sensor 111 may also detect a magnetic field based on magnetoresistance. In this case, the magnetic sensor 111 may be a magnetoresistive effect element such as a GMR (Giant Magneto Resistive Effect) element or a TMR (Tunnel Magneto Resistance Effect) element. The magnetic sensor 111 may also be a Hall element. In the following explanation, the case where the magnetic sensor 111 is a magnetoresistive effect element will be used as an example.

[0030] The resistance-to-voltage conversion circuit 112 converts the resistance value, which is the output of the magnetic sensor 111, into a voltage value. At this time, the resistance-to-voltage conversion circuit 112 can detect changes in the resistance value, which is the output of the magnetic sensor 111.

[0031] The AD converter 113 digitizes the voltage value output from the resistor-to-voltage conversion circuit 112.

[0032] The high-pass filter 114 attenuates the low-frequency components of the digital value output from the AD converter 113 and outputs a sensing value SO. At this time, the high-pass filter 114 can remove cancellation errors from the output of the AD converter 113.

[0033] The control unit 115 controls the magnetic field application unit 116 based on the output of the AD converter 113. For example, the control unit 115 can process the output of the magnetic sensor 111 as a signal, or control the strength and application timing of the bias magnetic field BM generated by the magnetic field application unit 116. The control unit 115 includes a range adjustment unit 115A, a bias setting unit 115B, and a sensing execution unit 115C.

[0034] The range adjustment unit 115A adjusts the detectable range of the magnetic sensor 111 based on the output of the magnetic sensor 111 when a bias magnetic field BM is applied. At this time, the range adjustment unit 115A can apply a bias magnetic field BM with an absolute value larger than that of an external disturbance magnetic field such as the Earth's magnetic field to the magnetic sensor 111 as an initial value. Then, the range adjustment unit 115A can narrow the adjustment range of the bias magnetic field BM based on the saturation state of the magnetic sensor 111 and detect the point of change in the output of the magnetic sensor 111. Then, the range adjustment unit 115A can adjust the detectable range of the magnetic sensor 111 based on the point of change in the output of the magnetic sensor 111.

[0035] The bias setting unit 115B sets the bias magnetic field BM applied to the magnetic sensor 111 to a range detectable by the magnetic sensor 111, based on the adjustment result by the range adjustment unit 115A. For example, the bias setting unit 115B can set the bias magnetic field BM so as to cancel out disturbance magnetic fields around the magnetic sensor 111, based on the adjustment result by the range adjustment unit 115A. In this case, the bias setting unit 115B may also set the bias magnetic field BM so as to cancel out disturbance magnetic fields based on the output of the magnetic sensor 111 to which the bias magnetic field BM is applied. This makes it possible to cancel out disturbance magnetic fields such as the Earth's magnetic field without requiring a magnetic sensor dedicated to detecting disturbance magnetic fields.

[0036] The sensing execution unit 115C causes the magnetic sensor 111 to perform sensing within the range set by the bias setting unit 115B. At this time, the bias magnetic field BM set by the bias setting unit 115B is applied to the magnetic sensor 111.

[0037] The magnetic field application unit 116 applies a bias magnetic field BM to the magnetic sensor 111. The magnetic field application unit 116 can use a solenoid, a coil, or the like. The strength and application timing of the bias magnetic field BM generated by the magnetic field application unit 116 can be controlled based on the current.

[0038] The magnetic sensors 111 may be arranged in an array of multiple units. In this case, a resistor-to-voltage conversion circuit 112 and an AD converter 113 can be provided for each magnetic sensor 111. When multiple magnetic sensors 111 are arranged in an array of multiple units, the range adjustment unit 115A can average the outputs of these magnetic sensors 111 and use this to adjust the detectable range of the magnetic sensors 111. This reduces the noise contained in the output of the magnetic sensors 111 and improves the accuracy of adjusting the detectable range of the magnetic sensors 111.

[0039] Figure 2 is a circuit diagram showing an example of the configuration of a magnetic field detection device according to the first embodiment.

[0040] In the figure, a magnetoresistive resistor R1 is provided as the magnetic sensor 111.

[0041] A resistor-to-voltage conversion circuit 112 is provided, consisting of resistors R2 to R5 and an operational amplifier OP. Magnetic resistor R1 and resistor R2 are connected in series with each other. Resistors R3 and R4 are connected in series with each other. The series circuits of magnetic resistor R1 and resistor R2, and the series circuits of resistors R3 and R4 are connected between the power supply potential VDD and the ground potential GND. The connection point of magnetic resistor R1 and resistor R2 is connected to the first input terminal of the operational amplifier OP. The connection point of resistors R3 and R4 is connected to the second input terminal of the operational amplifier OP. Resistor R5 is connected between the output terminal and the first input terminal of the operational amplifier OP.

[0042] Here, a reference voltage is generated based on the voltage drops of resistors R3 and R4 and applied to the second input terminal of the operational amplifier OP. When the magnetic resistor R1 changes when the bias magnetic field BM applied to the magnetic sensor 111 changes, the voltage applied to the first input terminal of the operational amplifier OP changes. Then, based on the change in the voltage applied to the first input terminal of the operational amplifier OP, the output of the operational amplifier OP changes, is digitized by the AD converter 113, and then input to the control unit 115. And the range adjustment unit 115A can detect the saturation state of the magnetic resistor R1 based on the change in the output of the operational amplifier OP. Here, when the magnetic resistor R1 is in the saturation state, even if the bias magnetic field BM applied to the magnetic sensor 111 changes, the output of the operational amplifier OP does not change. Alternatively, when the magnetic resistor R1 is in the saturation state, the output of the operational amplifier OP is set according to the saturation state. Therefore, the range adjustment unit 115A can determine whether the magnetic resistor R1 is in the saturation state based on the output of the operational amplifier OP when the bias magnetic field BM is applied to the magnetic sensor 111. And when the magnetic resistor R1 is in the saturation state, the range adjustment unit 115A can narrow the adjustment range of the bias magnetic field BM based on current control and detect the change point of the output of the operational amplifier OP. And the range adjustment unit 115A can adjust the detectable range of the magnetic sensor 111 based on the change point of the output of the operational amplifier OP.

[0043] As the magnetic field application unit 116, a solenoid 116A and a current control circuit 116B are provided. The solenoid 116A applies a bias magnetic field BM to the magnetic sensor 111. The solenoid 116A may be provided with an iron core. The current control circuit 116B controls the current flowing through the solenoid 116A based on the control of the control unit 115.

[0044] FIG. 3 is a diagram showing an operation example of the magnetic field detection device according to the first embodiment.

[0045] In a in the figure, the detectable range RDE of the magnetic sensor 111 is made narrower than the geomagnetism EG. At this time, the geomagnetism EG is located in the saturation region of the magnetic sensor 111. Therefore, when the bias magnetic field BM is not applied to the magnetic sensor 111, the magnetic sensor 111 operates in the saturation region during sensing of the magnetic sensor 111, and the magnetic sensor 111 cannot be sensed.

[0046] Here, the range adjustment unit 115A applies a bias magnetic field BM having an absolute value larger than that of an external disturbance magnetic field such as geomagnetism to the magnetic sensor 111 as an initial value. Then, when the magnetic sensor 111 is in a saturated state, the range adjustment unit 115A narrows the adjustment range of the bias magnetic field BM and detects the change point of the output of the magnetic sensor 111. When narrowing the adjustment range of the bias magnetic field BM, a binary search may be used in order to reduce the number of adjustments. In the binary search, the absolute value of the magnetic flux density of the bias magnetic field BM can be alternately changed between positive and negative while decreasing by half. Then, the range adjustment unit 115A adjusts the detectable range RDE of the magnetic sensor 111 based on the change point of the output of the magnetic sensor 111.

[0047] Next, in b in the figure, when the range adjustment unit 115A detects the change point of the output of the magnetic sensor 111, the lower limit LB and the upper limit UB of the magnetic flux density when the magnetic sensor 111 is saturated are detected. Then, the bias setting unit 115B sets the average value DB of the lower limit and the upper limit of the magnetic flux density as the bias magnetic field BM during sensing.

[0048] Next, in c in the figure, the sensing execution unit 115C executes sensing of the detection target when the bias magnetic field BM set by the bias setting unit 115B is applied to the magnetic sensor 111. At this time, the magnetoresistance R1 of the magnetic sensor 111 changes within the detectable range RDE of the magnetic sensor 111. Therefore, even when the detectable range RDE of the magnetic sensor 111 is narrower than the geomagnetism EM, the sensing of the magnetic sensor 111 can be realized.

[0049] FIG. 4 is a flowchart showing an operation example of the magnetic field detection device according to the first embodiment.

[0050] In the figure, the range adjustment unit 115A applies a bias magnetic field BM to the magnetic sensor 111 (S101) and calculates the magnetoresistance value of the magnetic sensor 111 (S102).

[0051] Next, the range adjustment unit 115A determines whether the magnetic resistance value is saturated at the upper end (S103). If the magnetic resistance value is saturated at the upper end, the range adjustment unit 115A reduces the bias magnetic field BM (S104) and returns to S101.

[0052] Meanwhile, the range adjustment unit 115A determines whether the magnetic resistance value is saturated at the lower end if it is not saturated at the upper end (S105). If the magnetic resistance value is saturated at the lower end, the range adjustment unit 115A increases the bias magnetic field BM (S106) and returns to S101.

[0053] On the other hand, if the magnetoresistance value is not saturated at the lower end, the bias setting unit 115B determines the bias magnetic field BM based on the upper and lower limits of the magnetoresistance value at saturation (S107), and applies the determined bias magnetic field BM to the magnetic sensor 111 (S108).

[0054] Next, the sensing execution unit 115C performs sensing of the target to be detected when the bias magnetic field BM determined by the bias setting unit 115B is applied to the magnetic sensor 111 (S109). At this time, the magnetic resistance R1 of the magnetic sensor 111 can be changed within the detectable range RDE of the magnetic sensor 111.

[0055] Figure 5 shows another example of adjusting the bias magnetic field of the magnetic field detection device according to the first embodiment.

[0056] In Figure 3a, the detectable range RDE of the magnetic sensor 111 was adjusted based on binary search. Alternatively, as shown in Figure 5, the detectable range RDE of the magnetic sensor 111 may be adjusted based on sequential search. In sequential search, the magnetic flux density of the bias magnetic field BM can be changed in predetermined steps to adjust the saturation region and change point of the output of the magnetic sensor 111.

[0057] As described above, in the first embodiment, the detectable range of the magnetic sensor 111 is adjusted based on the output of the magnetic sensor 111 when a bias magnetic field BM is applied. This allows the magnetic field detection device 100 to adjust the detectable range RDE of the magnetic sensor 111 and perform sensing with the magnetic sensor 111, even when the detectable range RDE of the magnetic sensor 111 is narrower than the geomagnetic field EM. Therefore, it is possible to eliminate the need for magnetic sensors dedicated to detecting magnetic shielding and disturbance magnetic fields, and to accommodate increased sensitivity of the magnetic sensor 111 while miniaturizing the magnetic field detection device 100.

[0058] <2. Second Embodiment> In the first embodiment described above, the detectable range of the magnetic sensor 111 was adjusted based on the output of the magnetic sensor 111 when a bias magnetic field BM was applied. In this second embodiment, the change in the disturbance magnetic field around the magnetic sensor 111 is predicted based on the detection result of the gyro sensor, and the initial value for adjusting the bias magnetic field BM applied to the magnetic sensor 111 during sensing is set based on the predicted value.

[0059] Figure 6 is a block diagram showing an example configuration of a magnetic field detection device according to the second embodiment.

[0060] In the figure, the magnetic field detection device 200 includes a control unit 215 instead of the control unit 115 of the first embodiment described above. Furthermore, the magnetic field detection device 200 has a gyro sensor 117 added to the magnetic field detection device 100 of the first embodiment described above. The other configurations of the magnetic field detection device 200 of the second embodiment are the same as those of the magnetic field detection device 100 of the first embodiment described above.

[0061] The gyro sensor 117 detects the angle (attitude), angular velocity, and angular acceleration of the magnetic sensor 111. The gyro sensor 117 may also be an angle sensor, an angular velocity sensor, and an angular acceleration sensor.

[0062] The control unit 215 is an additional unit, prediction unit 115D, to the control unit 115 of the first embodiment described above. The prediction unit 115D predicts changes in the disturbance magnetic field around the magnetic sensor 111 based on the detection results of the gyro sensor 117. At this time, the range adjustment unit 115A can control the bias magnetic field BM applied to the magnetic sensor 111 based on the prediction results from the prediction unit 115D. For example, when the orientation of the magnetic sensor 111 changes, the orientation of the geomagnetic field EM applied to the magnetic sensor 111 changes, and the components of the geomagnetic field EM applied to the magnetic sensor 111 change. Therefore, the prediction unit 115D can detect the components of the geomagnetic field EM applied to the magnetic sensor 111 based on the detection results of the gyro sensor 117. The range adjustment unit 115A can then set the initial value of the bias magnetic field BM when adjusting the detectable range RDE of the magnetic sensor 111 based on the components of the geomagnetic field EM.

[0063] As described above, in the second embodiment, the change in the disturbance magnetic field around the magnetic sensor 111 is predicted based on the detection result of the gyro sensor 117, and the initial value for adjusting the bias magnetic field BM applied to the magnetic sensor 111 is set based on the predicted value. This makes it possible to narrow the adjustment range of the detectable range RDE of the magnetic sensor 111 and improve the adjustment efficiency.

[0064] <3. Third Embodiment> In the first embodiment described above, the detectable range of the magnetic sensor 111 was adjusted based on the output of the magnetic sensor 111 when a bias magnetic field BM was applied. In this third embodiment, the configuration for adjusting the detectable range of the magnetic sensor 111 based on the output of the magnetic sensor 111 when a bias magnetic field BM was applied is integrated into a semiconductor chip.

[0065] Figure 7 is a perspective view showing an example of the configuration of a magnetic field detection device according to the third embodiment.

[0066] In the figure, the magnetic field detection device 300 includes a semiconductor chip CP. The semiconductor chip CP has a magnetic sensor 111, a resistor-to-voltage conversion circuit 112, an AD converter 113, a high-pass filter 114, and a control unit 115. The magnetic field application unit 116 may be formed on the semiconductor chip CP or it may be externally attached. In this case, the magnetic field application unit 116 may have a coil formed near the magnetic sensor 111, or the magnetic sensor 111 may be stacked on top of the coil. The magnetic sensor 111 may be arranged in an array on the semiconductor chip CP. The semiconductor material of the semiconductor chip CP may be Si, GaAs, SiC, GaN, InGaAs, InP, or InGaAsP, etc.

[0067] Thus, in the third embodiment described above, the configuration for adjusting the detectable range of the magnetic sensor 111 based on the output of the magnetic sensor 111 when a bias magnetic field BM is applied is integrated into the semiconductor chip CP. This makes it possible to miniaturize the magnetic field detection device 300 and speed up data processing when adjusting the detectable range of the magnetic sensor 111.

[0068] <4. Fourth Embodiment> In the first embodiment described above, the detectable range of the magnetic sensor 111 was adjusted based on the output of the magnetic sensor 111 when the bias magnetic field BM was applied. In this fourth embodiment, the computer is made to perform the process of adjusting the detectable range of the magnetic sensor 111 based on the output of the magnetic sensor 111 when the bias magnetic field BM was applied.

[0069] Figure 8 is a block diagram showing an example of the hardware configuration of a magnetic field detection device according to the fourth embodiment.

[0070] In the figure, the magnetic field detection device 400 includes a control unit 200. The control unit 200 includes a processor 211, a communication control unit 212, a communication interface 213, a main memory unit 214, an auxiliary memory unit 215, and an input / output interface 216. The processor 211, the communication control unit 212, the communication interface 213, the main memory unit 214, the auxiliary memory unit 215, and the input / output interface 216 are interconnected via an internal bus 317. The main memory unit 214 and the auxiliary memory unit 215 are accessible from the processor 211.

[0071] Furthermore, an input device 201, an output device 202, a magnetic sensor 111, a magnetic field application unit 116, and a gyro sensor 117 are provided outside the control unit 200. The input device 201 and the output device 202 are connected to the internal bus 317 via an input / output interface 216. The input device 201 and the output device 202 can be used as a human interface. For example, the input device 201 may be a keyboard, mouse, touch panel, card reader, voice input device, etc. For example, the output device 202 may be a screen display device (liquid crystal monitor, organic EL (Electro Luminescence) display, graphics card, etc.), a voice output device (speaker, etc.), a printing device, etc.

[0072] The processor 211 is hardware that controls the operation of the entire control unit 200. The processor 211 may be a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The processor 211 may be a single-core processor or a multi-core processor. The processor 211 may include hardware circuits (for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit)) that perform some or all of the processing. The processor 211 may include a neural network.

[0073] The main memory unit 214 can be composed of, for example, semiconductor memory such as SRAM (Static Random Access Memory) or DRAM (Dynamic Random Access Memory). The main memory unit 214 can store the program being executed by the processor 211, and can also provide a work area for the processor 211 to execute the program.

[0074] The auxiliary storage unit 215 is a storage device with a large storage capacity, such as a hard disk drive or an SSD (Solid State Drive). The auxiliary storage unit 215 can hold executable files of various programs and data used to execute programs. The auxiliary storage unit 215 can store the adjustment program 215A. The adjustment program 215A may be software that can be installed on the control unit 200, or it may be incorporated into the control unit 200 as firmware. The adjustment program 215A may also be an application program that can be downloaded to the control unit 200 via the network 206.

[0075] The communication control unit 212 is hardware that has a function to control communication with the outside world. The communication control unit 212 is connected to the network 206 via the communication interface 213. The network 206 may be a WAN (Wide Area Network) such as the Internet, a LAN (Local Area Network) such as Wi-Fi or Ethernet®, or a mixture of WAN and LAN. The network 206 may also include an in-vehicle network such as a CAN (Controller Area Network) or a LIN (Local Interconnect Network).

[0076] The input / output interface 216 converts data input from the input device 201 into a data format that can be processed by the processor 211, and converts data output from the processor 211 into a data format that can be processed by the output device 202. The input / output interface 216 may also include a resistor-to-voltage converter 112, an AD converter 113, and a high-pass filter 114.

[0077] The processor 211 reads the adjustment program 215A into the main memory 214 and executes the adjustment program 215A, thereby adjusting the detectable range of the magnetic sensor 111 based on the output of the magnetic sensor 111 when the bias magnetic field BM is applied. Furthermore, based on the adjustment result of the detectable range of the magnetic sensor 111, the processor 211 sets the bias magnetic field BM applied to the magnetic sensor 111 to the detectable range of the magnetic sensor 111, and causes the magnetic sensor 111 to perform sensing.

[0078] The execution of the adjustment program 215A may be divided among multiple processors or computers. Alternatively, the processor 211 may instruct a cloud computer or the like to execute all or part of the adjustment program 215A via the network 206 and receive the execution results.

[0079] Thus, in the fourth embodiment described above, the computer is made to perform a process to adjust the detectable range of the magnetic sensor 111 based on the output of the magnetic sensor 111 when the bias magnetic field BM is applied. This makes it possible to generalize the process of adjusting the detectable range of the magnetic sensor 111 based on the output of the magnetic sensor 111 when the bias magnetic field BM is applied, and also makes updates easier.

[0080] <5. Fifth Embodiment> In the first embodiment described above, the detectable range of the magnetic sensor 111 was adjusted based on the output of the magnetic sensor 111 when a bias magnetic field BM was applied. In this fifth embodiment, a magnetic field detection device 100 that adjusts the detectable range of the magnetic sensor 111 based on the output of the magnetic sensor 111 when a bias magnetic field BM was applied is applied is applied to biomagnetic detection.

[0081] Figure 9 is a block diagram showing an example configuration of a sensor system to which the magnetic field detection device according to the fifth embodiment is applied.

[0082] In the figure, the sensor system 500 includes a biomagnetic sensor 511 as the magnetic sensor 111. Furthermore, the sensor system 500 has a mounting device 512, an image processing device 513, and a display device 514 added to the magnetic field detection device 100 of the first embodiment described above. The other configurations of the sensor system 500 of the fifth embodiment are the same as those of the magnetic field detection device 100 of the first embodiment described above.

[0083] The biomagnetic sensor 511 detects biomagnetic fields such as brain magnetism or cardiac magnetism. The biomagnetic sensor 511 can, for example, have an observation frequency range set from 0 to 50 Hz. At this time, the magnetic field application unit 116 applies a bias magnetic field BM to the biomagnetic sensor 511. The range adjustment unit 115A adjusts the detectable range of the biomagnetic sensor 511 based on the output of the biomagnetic sensor 511 when the bias magnetic field BM is applied.

[0084] The attachment device 512 attaches the biomagnetic sensor 511 to the human body. At this time, the attachment device 512 can support the biomagnetic sensor 511 around the brain or around the chest. The biomagnetic sensor 511 may also be embedded in the attachment device 512.

[0085] The image processing device 513 visualizes the sensing value SO output via the high-pass filter 114. At this time, the image processing device 513 may create a color image of the intensity of the sensing value SO for each part of the human body, such as the brain or chest.

[0086] The display device 514 displays the sensing value SO output via the image processing device 513. The display device 514 may be a liquid crystal monitor or an organic EL display.

[0087] Thus, in the fifth embodiment described above, the detectable range of the biomagnetic sensor 511 is adjusted based on the output of the biomagnetic sensor 511 when a bias magnetic field BM is applied. This eliminates the need for magnetic shielding and magnetic sensors dedicated to detecting disturbance magnetic fields, making it possible to miniaturize the sensor system 500 while increasing the sensitivity of the biomagnetic sensor 511.

[0088] The embodiments described above are merely examples for realizing the present technology, and there is a corresponding relationship between the matters in the embodiments and the inventive features in the claims. Similarly, there is a corresponding relationship between the inventive features in the claims and the matters in the embodiments of the present technology bearing the same name. However, the present technology is not limited to the embodiments and can be realized by making various modifications to the embodiments without departing from the gist of the technology. Furthermore, the effects described herein are merely examples and are not limiting, and other effects may also exist.

[0089] Furthermore, this technology can also be configured as follows: (1) A magnetic field detection device comprising: a magnetic sensor for detecting a magnetic field; a magnetic field application unit for applying a bias magnetic field to the magnetic sensor; and a range adjustment unit for adjusting the detectable range of the magnetic sensor based on the output of the magnetic sensor when the bias magnetic field is applied. (2) The magnetic field detection device according to (1), comprising: a bias setting unit for setting the bias magnetic field applied to the magnetic sensor to a detectable range of the magnetic sensor based on the adjustment result of the range adjustment unit; and a sensing execution unit for causing the magnetic sensor to perform sensing within the range set by the bias setting unit. (3) The magnetic field detection device according to (1), wherein the bias setting unit sets the bias magnetic field so as to cancel out disturbance magnetic fields around the magnetic sensor based on the adjustment result of the range adjustment unit. (4) The magnetic field detection device according to (3), wherein the bias setting unit sets the bias magnetic field so as to cancel out disturbance magnetic fields based on the output of the magnetic sensor to which the bias magnetic field is applied. (5) A magnetic field detection device according to any one of (1) to (4), comprising a gyro sensor and a prediction unit that predicts changes in the disturbance magnetic field around the magnetic sensor based on the detection result of the gyro sensor, wherein the range adjustment unit controls the bias magnetic field applied to the magnetic sensor based on the prediction result of the prediction unit. (6) A magnetic field detection device according to any one of (1) to (5), comprising a high-pass filter that attenuates the low-frequency component of the output of the magnetic sensor. (7) A magnetic field detection device according to any one of (1) to (6), wherein the magnetic sensor detects the magnetic field based on magnetoresistance. (8) A magnetic field detection device according to any one of (1) to (7), wherein the range adjustment unit adjusts the detectable range of the magnetic sensor based on the change in magnetoresistance. (9) A magnetic field detection device according to (8), wherein the range adjustment unit adjusts the saturation region of the magnetic sensor based on the change in magnetoresistance, controls the bias magnetic field based on the adjustment result of the saturation region, and adjusts the detectable range of the magnetic sensor. (10) The magnetic field detection device according to (9) above, wherein the range adjustment unit controls the bias magnetic field based on the control of the current flowing through the magnetic field application unit.(11) The magnetic field detection device according to (10), wherein the range adjustment unit sets the bias magnetic field to be greater than the absolute value of the Earth's magnetic field, reduces the current flowing to the magnetic field application unit when the saturation region of the magnetic sensor is detected, and adjusts the detectable range of the magnetic sensor based on the change in the magnetic resistance of the magnetic sensor when the current flowing to the magnetic field application unit is reduced. (12) The magnetic field detection device according to (11), wherein the range adjustment unit controls the current flowing to the magnetic field application unit based on binary search. (13) The magnetic field detection device according to any one of (1) to (12), comprising a semiconductor chip on which the magnetic sensor and the range adjustment unit are integrated. (14) The magnetic field detection device according to (13), wherein the magnetic sensor is integrated in an array on the semiconductor chip. (15) A sensor system comprising: a magnetic sensor for detecting biomagnetism; a magnetic field application unit for applying a bias magnetic field to the magnetic sensor; a range adjustment unit for adjusting the detectable range of the magnetic sensor based on the output of the magnetic sensor when the bias magnetic field is applied; a bias setting unit for setting the bias magnetic field applied to the magnetic sensor to the detectable range of the magnetic sensor based on the adjustment result by the range adjustment unit; and a sensing execution unit for causing the magnetic sensor to perform sensing within the range set by the bias setting unit. (16) The sensor system according to (15), wherein the biomagnetism is brain magnetism or cardiac magnetism. (17) A program for causing a computer to perform the steps of: applying a bias magnetic field to the magnetic sensor; and adjusting the detectable range of the magnetic sensor based on the output of the magnetic sensor when the bias magnetic field is applied. (18) The program according to (17) for causing a computer to perform the steps of: setting the bias magnetic field applied to the magnetic sensor to the detectable range of the magnetic sensor based on the adjustment result of the detectable range of the magnetic sensor; and causing the magnetic sensor to perform sensing within the detectable range of the magnetic sensor.

[0090] 100 Magnetic field detection device 111 Magnetic sensor 112 Resistance-to-voltage conversion circuit 113 AD converter 114 High-pass filter 115 Control unit 115A Range adjustment unit 115B Bias setting unit 115C Sensing execution unit 116 Magnetic field application unit

Claims

1. A magnetic field detection device comprising: a magnetic sensor for detecting a magnetic field; a magnetic field application unit for applying a bias magnetic field to the magnetic sensor; and a range adjustment unit for adjusting the detectable range of the magnetic sensor based on the output of the magnetic sensor when the bias magnetic field is applied.

2. A magnetic field detection device according to claim 1, comprising: a bias setting unit that sets the bias magnetic field applied to the magnetic sensor to a range detectable by the magnetic sensor based on the adjustment result by the range adjustment unit; and a sensing execution unit that causes the magnetic sensor to perform sensing within the range set by the bias setting unit.

3. The magnetic field detection device according to claim 2, wherein the bias setting unit sets the bias magnetic field so as to cancel out the disturbance magnetic field around the magnetic sensor, based on the adjustment result by the range adjustment unit.

4. The magnetic field detection device according to claim 3, wherein the bias setting unit sets the bias magnetic field based on the output of the magnetic sensor to which the bias magnetic field is applied, so as to cancel out the disturbance magnetic field.

5. A magnetic field detection device according to claim 1, comprising a gyro sensor and a prediction unit that predicts changes in the disturbance magnetic field around the magnetic sensor based on the detection result of the gyro sensor, wherein the range adjustment unit controls the bias magnetic field applied to the magnetic sensor based on the prediction result of the prediction unit.

6. The magnetic field detection device according to claim 1, further comprising a high-pass filter for attenuating the low-frequency components of the output of the magnetic sensor.

7. The magnetic field detection device according to claim 1, wherein the magnetic sensor detects the magnetic field based on magnetoresistance.

8. The magnetic field detection device according to claim 1, wherein the range adjustment unit adjusts the detectable range of the magnetic sensor based on the change in magnetoresistance.

9. The magnetic field detection device according to claim 8, wherein the range adjustment unit adjusts the saturation region of the magnetic sensor based on the change in magnetoresistance, controls the bias magnetic field based on the adjustment result of the saturation region, and adjusts the detectable range of the magnetic sensor.

10. The magnetic field detection device according to claim 9, wherein the range adjustment unit controls the bias magnetic field based on the control of the current flowing through the magnetic field application unit.

11. The magnetic field detection device according to claim 10, wherein the range adjustment unit sets the bias magnetic field to be greater than the absolute value of the Earth's magnetic field, reduces the current flowing to the magnetic field application unit when the saturation region of the magnetic sensor is detected, and adjusts the detectable range of the magnetic sensor based on the change in the magnetic resistance of the magnetic sensor when the current flowing to the magnetic field application unit is reduced.

12. The magnetic field detection device according to claim 11, wherein the range adjustment unit controls the current flowing to the magnetic field application unit based on binary search.

13. The magnetic field detection device according to claim 1, comprising a semiconductor chip in which the magnetic sensor and the range adjustment unit are integrated.

14. The magnetic field detection device according to claim 13, wherein the magnetic sensor is integrated in an array on the semiconductor chip.

15. A sensor system comprising: a magnetic sensor for detecting biomagnetism; a magnetic field application unit for applying a bias magnetic field to the magnetic sensor; a range adjustment unit for adjusting the detectable range of the magnetic sensor based on the output of the magnetic sensor when the bias magnetic field is applied; a bias setting unit for setting the bias magnetic field applied to the magnetic sensor to a detectable range of the magnetic sensor based on the adjustment result by the range adjustment unit; and a sensing execution unit for causing the magnetic sensor to perform sensing within the range set by the bias setting unit.

16. The sensor system according to claim 15, wherein the biomagnetic field is brain magnetism or cardiac magnetism.

17. A program that causes a computer to perform the steps of applying a bias magnetic field to a magnetic sensor and adjusting the detectable range of the magnetic sensor based on the output of the magnetic sensor when the bias magnetic field is applied.

18. The program according to claim 17, which causes a computer to perform the steps of: setting the bias magnetic field applied to the magnetic sensor to the detectable range of the magnetic sensor based on the result of adjusting the detectable range of the magnetic sensor; and causing the magnetic sensor to perform sensing within the detectable range of the magnetic sensor.

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