JP4593440B2 - Direction measuring device and direction measuring method - Google Patents

Description

  The present invention relates to an azimuth measuring apparatus and an azimuth measuring method.

  Conventionally, the electronic device is suitable for an electronic device such as a mobile phone provided with a magnetic sensor that detects peripheral magnetism in a biaxial or triaxial direction and outputs magnetic field information based on the magnetic field based on the magnetic field information. There are provided an electronic compass mode for displaying the current direction and a navigation mode for displaying the direction superimposed on a map image or the like.

As a method for providing magnetic field information, an azimuth measurement method has been devised in which an offset correction value is calculated and the magnetic field information is corrected using the offset correction value. As an example, the value (magnetic field information) output from the magnetic sensor is acquired every elapse of a predetermined time, the offset correction value is calculated from the average value of the output (magnetic field information) from the magnetic sensor at that time, and the offset An azimuth measuring method for correcting using a correction value is known (see, for example, Patent Document 1).
JP 2003-156335 A

  However, in the technique of Patent Document 1, although a quick measurement result can be obtained by shortening the measurement cycle, the change or movement of the attitude of the electronic device becomes minute, the variation in magnetic field information data is reduced, and offset correction is performed. There is a problem that the calculation accuracy of the value is lowered. Therefore, it is not possible to output a variety of outputs, such as outputting azimuth measurement results according to the measurement accuracy required in the electronic compass mode, while outputting azimuth measurement results corresponding to the measurement accuracy required in the navigation mode. It was possible. In addition, the power consumed by driving the magnetic sensor is the same regardless of the output of the azimuth measurement result in any display mode, and there is a problem that power saving is hindered.

  This invention is made | formed in view of such a subject, and it aims at providing the azimuth | direction measuring apparatus and the azimuth | direction measuring method which can perform azimuth | direction measurement with the measurement precision according to a use.

In order to solve the above problems, an azimuth measuring device according to claim 1
Magnetic detection means for detecting the surrounding magnetism and outputting as magnetic field information;
Correction value calculation means for calculating a correction value based on magnetic field information output when the magnetic detection means is driven;
Based on the correction value calculated by the correction value calculation means, the azimuth calculation means for correcting the magnetic field information output from the magnetic detection means and performing azimuth calculation;
Display means for displaying a calculation result by the azimuth calculation means;
Setting means for setting the display mode of the calculation result displayed on the display means;
And a control means for controlling the drive cycle of the magnetic detection means based on the setting contents of the setting means.

The invention according to claim 2 is the invention according to claim 1,
The display mode set by the setting means includes a numerical display of the azimuth calculated by the azimuth calculating means and a schematic display of the azimuth.
The control means is characterized in that when the numerical display is set by the setting means, the drive period of the magnetic detection means is made shorter than when the schematic display is set.

The direction measuring method according to claim 3 is:
A correction value calculating step for calculating a correction value based on magnetic field information output when the magnetic detection unit is driven;
Based on the correction value calculated in the correction value calculation step, the azimuth calculation step for correcting the output magnetic field information and performing the azimuth calculation;
A display step for displaying a calculation result in the azimuth calculation step;
A setting step for setting a display mode of the calculation result displayed in this display step;
And a control step for controlling the drive period of the magnetic detection unit based on the setting contents in the setting step.

The program according to claim 4 is stored in a computer.
A correction value calculation function for calculating a correction value based on magnetic field information output when the magnetic detection unit is driven;
Based on the correction value calculated by the correction value calculation function, the azimuth calculation function for correcting the output magnetic field information and performing the azimuth calculation;
A display function to display the calculation result by this azimuth calculation function;
A setting function for setting a display mode of a calculation result displayed by the display function;
And a control function for controlling the drive cycle of the magnetic detection unit based on the setting contents of the setting function.

  According to the first, third, and fourth aspects of the invention, the correction necessary for correcting the magnetic information is performed by controlling the driving cycle of the magnetic detection unit based on the setting content of the display mode of the direction calculation result by the setting unit. Since the value is acquired, the azimuth measurement can be performed with the measurement accuracy according to the application, and the power consumption for driving the magnetic detection means can be saved.

Embodiment
Hereinafter, an embodiment when the azimuth measuring device of the present invention is applied to a mobile phone 100 which is one of electronic devices will be described in detail with reference to the drawings.

  First, FIG. 1 is an example of a front view and a rear view of a mobile phone 100. As shown in FIG. 1, the mobile phone 100 is configured such that a lid portion 101 and a main body portion 102 can be folded by a hinge 103. The lid 101 is provided with a reception speaker 1, a main display 2, a sub display 5, an imaging lens 6, and an LED (Light Emitting Diode) flash 10, and the main body 102 has an input 3 and a transmission microphone 4. A detachable rechargeable battery 7 having a power connection terminal 12 and an external interface 13 are provided.

  The input unit 3 includes operation keys such as a numeric key, a clear key, a menu key, an off-hook key, and an on-hook key in addition to the enter key 31, the cursor key 32, the camera key 33, the first direction measurement key 34, and the second direction measurement key 35. Composed of groups.

  The cursor key 32 is a key for scrolling the screen and performing a selection operation, and is configured to be able to detect four directions, up, down, left, and right. The user, for example, selects a function from the menu list displayed by pressing the menu key or changes the setting contents by pressing the cursor key 32, and further determines / determines by pressing the enter key 31. Set up. The camera key 33 is a key for starting shooting by the camera unit 70. The user presses the camera key 33 to turn on the LED flash 10 and presses the enter key 31 to take a picture.

  The first azimuth measurement key 34 and the second azimuth measurement key 35 are keys for starting processing based on an application program for azimuth measurement (hereinafter, this processing is referred to as “azimuth measurement application”).

  When the user opens the lid 101 of the mobile phone 100 to set the lid open, the user presses one of the first azimuth measurement key 34 and the second azimuth measurement key 35 to activate the azimuth measurement application. Then, the direction of the direction in which the mobile phone 100 faces is displayed as a compass, for example, as shown in FIG. A display mode in which the measured azimuth is displayed by the azimuth angle 53 and the 16-segment magnetic needle 54 is referred to as an electronic compass mode.

  Further, in the case of performing the azimuth display in the navigation mode for performing the user's route guidance, the map image 50 is displayed so that the traveling direction of the user faces the upper side of the main display unit 2 as shown in FIG. A 16-divided magnetic needle 52 is superimposed and displayed.

  Further, when the cover 101 of the mobile phone 100 is closed and the cover is closed, the second direction measurement key 35 provided on the side surface of the mobile phone 100 is pressed to start the direction measurement application. In this case, the orientation of the mobile phone 100 is displayed on the sub display unit 5 in the electronic compass mode. The mobile phone 100 in the closed state is more compact than the open state by being folded, and functions as an electronic compass that can be accommodated in a so-called palm that displays an orientation on the sub display unit 5.

  FIG. 2 is a block diagram illustrating an example of a functional configuration of the mobile phone 100. According to the figure, the mobile phone 100 includes a control unit 166, a flash memory 167, a program ROM (Read Only Memory) 168, a system ROM 163, a data storage RAM (Random Access Memory) 164, an address / data bus processing unit 165, an input. 3, a display control unit 60, a camera unit 70, an audio output unit 80, a GPS (Global Positioning System) receiving unit 40, a communication unit 90, an external interface controller 176, a rechargeable battery 7, and a sensor unit 175.

  The configuration of these functional units can be appropriately designed and adopted. For example, the control unit 66 and the communication control unit 16 of the communication unit 90 may be integrated into a circuit configuration, or the system ROM 163, the program ROM 168, etc. The memories may be composed of the same memory.

  The control unit 166 includes a processor such as a CPU (Central Processing Unit) and performs processing corresponding to the application layer (layer 7) in the OSI reference model. Specifically, an application program stored in the program ROM 168 is read in response to an operation signal input from the input unit 3, and processing according to the program is executed. Then, the processing result is output to the display control unit 60 and displayed on the main display unit 2 and the sub display unit 5.

  In the present embodiment, when the control unit 166 detects that the first azimuth measurement key 34 and the second azimuth measurement key 35 are pressed by the user, the control unit 166 reads the azimuth measurement program from the program ROM 168, and the driver 1661 according to the program. The azimuth measurement application (corresponding to the flowchart of the application in FIG. 4) that acquires the azimuth calculated by the above and displays it on the display control unit 60 is started.

  The control unit 166 includes a driver 1661 that performs processing corresponding to the physical layer (layer 1) in the OSI reference model. In the present embodiment, the driver 1661 intermittently drives the sensor unit 175 in the background where the azimuth measurement application is activated, and acquires magnetic field information output from the magnetic sensor 178 of the sensor unit 175. Then, the offset correction value is calculated and the direction calculation is performed and returned to the direction measurement application.

  The flash memory 167 is a readable / writable nonvolatile memory, and is a memory area that temporarily stores various programs executed by the control unit 166 and data related to the execution of these programs.

  According to FIG. 2, the flash memory 167 includes an offset correction value table 1671. The offset correction value table 1671 is a data area for storing magnetic field information output from the magnetic sensor 178, offset correction values to be calculated / updated, and the like. The driver 1661 sequentially accumulates and stores the magnetic field information output from the magnetic sensor 178 when the azimuth measurement application is activated, and recalculates the offset correction value stored in the table using the magnetic field information. The offset correction value table 1671 is updated and stored. The driver 1661 updates the offset correction value as needed with the acquired magnetic field information, and performs an azimuth calculation using the offset correction value and the magnetic field information.

  The program ROM 168 is configured by a NOR flash memory, stores an application program necessary for the operation of the mobile phone 100 and data related to the execution of the program, and in this embodiment, an orientation measurement program for executing an orientation measurement application. Is stored.

  The system ROM 163 is a basic OS (operating system), various initial settings, an initialization (IPL) program for loading a program necessary for hardware inspection, various initial setting values related to the program, the mobile phone 100 Data (for example, serial number and subscriber ID) necessary for authentication is stored.

  The data storage RAM 164 is a readable / writable volatile memory, for example, multimedia including data related to communication of the mobile phone 100 such as address book data and mail data, still images and moving images captured by the camera unit 70. Stores data etc.

  The address / data bus processing unit 165 performs address control between the control unit 166 and the communication unit 90, control of data communication on the bus, and the like.

  The input unit 3 is an input device including a key group necessary for inputting an instruction to start execution of a program and inputting various information, and outputs a key pressing signal pressed by the user to the control unit 166.

  The display control unit 60 includes a display driver 169, a main display unit 2, a sub display unit 5, and an LED flash 10. The display driver 169 turns on the LED flash 10 according to an instruction from the control unit 166 and displays various screens on the main display unit 2 and the sub display unit 5.

  The main display unit 2 and the sub display unit 5 are display devices for displaying various information, orientations, and the like of the mobile phone 100, and are configured by an LCD (Liquid Crystal Display), an ELD (Electro Luminescence Display), or the like. When the control unit 166 detects, for example, that the mobile phone 100 is folded, that is, the lid is closed, by detecting the opening / closing detection magnet or the rotation of the hinge 103, the display of the main display unit 2 is displayed. The display is turned off, the display is switched to the sub display unit 5, and the display is switched to the main display unit 2 when it is detected that the lid is open.

  The GPS receiver 40 receives a GPS signal transmitted from a GPS satellite, measures the current position based on the GPS signal, and generates position information (for example, latitude and longitude). Then, the position information is output to the control unit 166. The control unit 166 drives the GPS receiving unit 40 in the navigation mode, acquires a map image near the current position from a server on the Internet based on the output position information, and causes the main display unit 2 to display the map image. At this time, a map image is displayed from the magnetic field information output from the magnetic sensor 178 in accordance with the direction in which the mobile phone 100 is facing. This allows the user to recognize which direction he / she is facing on the map.

  Based on an instruction input from the control unit 166, the communication unit 90 performs voice communication and various data communication with a wireless base station on a wireless communication network (including a wireless telephone network) via the antenna 14. It is a functional part. The communication unit 90 includes the communication control unit 16 including the antenna 14, the wireless unit 15, the communication data processing unit 161, and the audio interface 162.

  The radio unit 15 performs radio processing such as tuning processing of the antenna 14, A / D conversion of received signals, D / A conversion of transmission data, and modulation / demodulation. The communication data processing unit 161 includes a CELP (Code-Excited Linear Prediction) vocoder, a speech decoding processing circuit, a packet data generation circuit, and the like. The communication data processing unit 161 decodes data received via the wireless unit 15 and receives received data. Or the transmission data output from the audio interface 162 is encoded. The audio interface 162 outputs a voice based on the reception data acquired by the communication data processing unit 161 from the reception speaker 1 or converts a user's voice input from the transmission microphone 4 into transmission data of a digital signal. To do.

  As a modulation / demodulation method of a radio signal transmitted and received between the communication unit 90 and the radio base station, a PSK (Phase Shift Keying) method, a PDC (Personal Digital Cellular) method, a CDMA (Code Division Multiple Access) method, a GSM (Global Any of various known techniques such as a System for Mobile communication method may be used.

  The camera unit 70 includes an imaging module 171 such as a CMOS (Complementary Metal Oxide Semiconductor) sensor or a CCD (Charge Coupled Device) sensor, a DSP (Digital Signal Processor) 172, a piezo motor 170, and an imaging lens 6. The imaging module 171 photoelectrically converts the optical image transmitted through the imaging lens 6 to generate an electrical signal, D / A converts the electrical signal, and outputs the electrical signal to the DSP 172.

  The DSP 172 performs various digital signal processing such as encoding and compression processing of the digital signal output from the imaging module 171 and image processing. The control unit 166 stores the captured image that has been subjected to the digital signal processing by the DSP 172 in the data storage RAM 164. The piezo motor 170 is a motor for performing zoom control of the imaging lens 6.

  This is a functional unit that outputs audio based on audio data input from the audio output unit 80 and the control unit 166 to the stereo speakers 8 and 9, and includes a sound source IC 173 and an amplifier 174. The sound source IC 173 stores in advance a ring tone that is output when a call is received, voice data of operation sounds that are output when a key group is pressed, D / A conversion of these data, and amplification by an amplifier 174 Then, audio is output from the stereo speakers 8 and 9.

  The external interface controller 176 controls, for example, the power connection terminal 12 of the 18-core connector and the external interface 13 that performs data communication with an external device. The rechargeable battery 7 supplies power to each functional unit based on an instruction from the control unit 166 using the power stored via the power connection terminal 12.

  The sensor unit 175 includes a magnetic sensor 178 (for example, a Hall element, an MI (Magneto Impedance) element, an amorphous magnetic body) that detects magnetism in three directions of the X axis, the Y axis, and the Z axis of the mobile phone 100, a temperature, And a sensor 177. The magnetic sensor 178 detects peripheral magnetism in the three axial directions in accordance with an instruction from the driver 1661 of the control unit 166, and outputs the magnetism to the driver 1661 as magnetic field information. The temperature sensor 177 detects the temperature of the magnetic sensor 178 in accordance with an instruction from the driver 1661 and returns it to the driver 1661.

  The driver 1661 drives the sensor unit 175 intermittently, calculates an offset correction value based on the magnetic field information output from the magnetic sensor 178 during the driving, and corrects the magnetic field information using the offset correction value. For the calculation of the offset correction value, it is necessary to acquire the magnetic field information that varies, and the larger the variation, the more accurate the offset correction value can be calculated and the correction accuracy of the magnetic field information can be improved.

  Specifically, by widening the time interval for acquiring the magnetic field information, the mobile phone 100 can be easily changed in posture and movement, and the magnetic field information with variations can be acquired. However, since it is difficult to perform highly accurate correction when the magnetic field fluctuates rapidly, it is desirable to first increase the accuracy by correcting the magnetic field information with low accuracy.

  Therefore, in the present embodiment, two correction levels are provided according to the degree of variation in magnetic field information, and the correction accuracy of the magnetic field information is increased by switching the correction levels in stages. Here, each correction level will be described with reference to FIG.

  First, level A is the correction level with the lowest correction accuracy, and can be switched by driving the sensor unit 175 at a cycle of 100 ms in both the electronic compass mode and the navigation mode. Further, it is set as a default correction level at the start of azimuth measurement. The period for driving the sensor unit 175 is hereinafter referred to as “drive period”.

  At this level A, the drive cycle is set shorter than other correction levels, and the variation in magnetic field information is reduced. For this reason, by reflecting the magnetic field information with little variation in the offset correction value, the calculation accuracy of the offset correction value is lowered, but the number of data of the magnetic field information can be increased. Correction is possible in small changes.

  Level C is the correction level with the highest correction accuracy, and the driving cycle of the sensor unit 175 is set at 400 ms and is adopted in the navigation mode. Level B is set as an intermediate accuracy between level A and level C. This level B is set in the electronic compass mode when the driving cycle of the sensor unit 175 is set to 200 ms.

  When the driver 1661 starts azimuth measurement, the correction level is switched in the order of level A → level B (electronic compass mode) or level A → level C (navigation mode) according to the number of offset correction value calculations. The drive cycle of the sensor unit 175 is increased. As a result, the magnetic field information acquired in the drive cycle is likely to be subject to changes in the posture and movement of the mobile phone 100. For this reason, the dispersion | variation in the data of magnetic field information becomes large, and the calculation precision of an offset correction value becomes high. In other words, regardless of which display mode is set, first, at a level A, the magnetic field information is corrected by calculating an offset correction value at a high speed and roughly with the magnetic field information having a large number of data, and thereafter, according to the set display mode. The correction accuracy is increased by increasing the correction level with level B and level C.

  In addition, by increasing the correction level and lengthening the driving cycle, it is not necessary to drive the sensor unit 175 unnecessarily in order to acquire magnetic field information with large variations, and circuit resources can be used efficiently.

  Specifically, as shown in FIG. 3, if the driving time of the sensor unit 175 is 40 ms and the driving current at that time is approximately 8 mA, the current consumption per 3.2 ms of the sensor unit 175 at level A is 3.2 mA. (= 8 mA × (40 ms / 100 ms)). On the other hand, 1.6 mA (= 8 mA × (40 ms / 200 ms)) is consumed at level B, and 0.8 ms (= 8 mA × (40 ms / 400 ms)) is consumed at level C. Thus, by increasing the correction level and lengthening the driving cycle, it is possible to improve the correction accuracy and suppress the current consumption.

  The reason why the drive cycle is changed according to the display mode as described above is as follows.

  First, as a first reason, the navigation mode is allowed up to an error of 22.5 ° in order to display the measured azimuth in 16 divisions, whereas the electronic compass mode has a numerical value (azimuth) This is because a higher accuracy than that in the navigation mode is required for display by angle).

  As a second reason, it is assumed that the electronic compass mode does not move much while the user holds the mobile phone 100 in his / her hand, and it is difficult to obtain fluttering magnetic field information, whereas the navigation mode This is because the display mode is assumed to be used while moving, and it is assumed that the mobile phone 100 moves.

  The third reason is that the electronic compass mode that performs only the azimuth display is assumed to have a shorter user use time than the navigation mode that provides the route guidance to the destination. This is because it is necessary to shorten the time. Further, this is because power saving is desired in the navigation mode having a long usage time.

  In this way, by changing the drive cycle according to the correction accuracy required in each display mode of the electronic compass mode and navigation mode, priority is given to improving correction accuracy in the electronic compass mode, and power saving in the navigation mode. Can be prioritized.

  The range in which the drive cycle can be set is 100 ms or more and 1 s or less. This is because, if the magnetic field information to be acquired is excessively adjacent, it is difficult to acquire the dispersed data, and therefore the correction effect cannot be expected when the drive cycle is set to 100 ms or less. In addition, if the interval of the magnetic field information to be acquired is too far away, it is difficult to acquire the magnetic field information according to the fine movement of the mobile phone 100, and the connection between the continuous magnetic field information is thin and its usefulness is reduced. .

  Next, specific processing contents of the direction measuring method of the mobile phone 100 will be described with reference to the flowcharts of FIGS. As described above, the direction measurement application is a process executed by the control unit 166, and the main body is the control unit 166. In order to clarify the relationship with the driver 1661 included in the control unit 166, the direction measurement application is appropriately set. The measurement application will be mainly described.

  First, the azimuth measurement application functioning as a user interface detects that the user presses either the first azimuth measurement key 34 or the second azimuth measurement key 35 by the control unit 166, and performs an operation on the input unit 3 of the user. A display command indicating the display mode set accordingly is output to the driver 1661 (step B1), and a standby state for detecting the calculation result of the azimuth calculation from the driver 1661 is entered (step B3).

  Then, the azimuth measurement application shifts to the process of Step B3 and waits for the output of the calculation result from the driver 1661. For example, when the clear key is pressed, the program end command output by the main process of the control unit 166 is detected. In the case (step B13; Yes), an end command is output to the driver 1661, and the direction measurement of the driver 1661 is ended (step B15). After outputting the program end command to the direction measurement application, the control unit 166 ends the process of the direction measurement application.

  On the other hand, the driver 1661 determines the display mode set by the user based on the display command output from the direction measurement application (step A1), and if determined to be the navigation mode (step A1; navigation), the step When A3 to A17 directions are measured and it is determined that the electronic compass mode is selected (step A1; electronic compass), the directions A31 to A45 are measured. Then, the processing of steps A3 to A17 and the processing of steps A31 to A45 are performed until the end command is output from the azimuth measurement application, and when the output of the command is detected, the display command is again output.

  Note that the processes in steps A3 to A9 and the processes in steps A31 to A37 are processes in each display mode when the correction level is set to level A, and the processes are the same. The processing in steps A11 to A17 is processing in the navigation mode when the correction level is set to level C, and the processing in steps A39 to A45 is processing in the electronic compass mode when the correction level is set to level B. It is.

  First, when the driver 1661 determines that the display mode is the navigation mode, the driver 1661 sets the correction level to level A, drives the sensor unit 175 with a driving period of 100 ms, and acquires magnetic field information output from the magnetic sensor 178. (Step A3). Then, the offset correction value is calculated based on the acquired magnetic field information, the offset correction value table 1671 is updated (step A5), the direction calculation is performed, and the calculation result is output to the direction measurement application (step A7). .

  The driver 1661, after obtaining the magnetic field information and outputting the calculation result to the direction measurement application, repeats the calculation of the offset correction value and the update of the offset correction value table 1671 three times (Steps A3 to A9; No) ).

  At this time, when the azimuth measurement application detects the calculation result output from the driver 1661 in step A7 (step B5; Yes), if the display mode is the navigation mode (step B7; navigation), the communication unit 90 Then, the map image 50 received from the server on the Internet is displayed on the main display unit 2 in the direction according to the direction of the calculation result. Then, based on the current position measured by the GPS receiver 40 and the destination position, the traveling direction of the user is displayed with an arrow 51 as shown in FIG. Moreover, the magnetic needle 52 of the electronic compass of 16 division directions is displayed on the map image 50 (step B9).

  When the number of offset corrections exceeds 3 in step A9 (step A9; Yes), the driver 1661 switches the correction level to level C, drives the sensor unit 175 with a drive period of 400 ms, and acquires magnetic field information ( Step A11). Then, the offset correction value is calculated based on the acquired magnetic field information, the offset correction value table 1671 is updated (step A13), the direction calculation is performed, and the calculation result is output to the direction measurement application (step A15). .

  Next, the driver 1661 determines whether or not a sudden change in the ambient magnetic field or a temperature change in the sensor unit 175 has been detected based on the environmental change condition (step A17). Specifically, when the magnetic voltage value detected by the magnetic sensor 178 exceeds the range, it is determined that the surrounding magnetic field has changed significantly. Further, when the temperature detected by the temperature sensor 177 changes more than a certain value, it is determined that the temperature change of the sensor unit 175 has been detected.

  If the driver 1661 determines that a sudden change in the ambient magnetic field or a temperature change in the sensor unit 175 has been detected (step A17; Yes), the driver 1661 switches the correction level to the level A and proceeds to the process in step A3. As described above, when a sudden change in the peripheral magnetic field or a temperature change in the sensor unit 175 occurs, the correction level is switched to the level A to facilitate the calculation of the offset correction value and the correction of the magnetic field information.

  Since the azimuth calculation in step A15 is performed based on the magnetic field information corrected at level C, the calculation result of the azimuth with higher accuracy than the calculation result in step A7 is obtained. For this reason, it is possible to improve the accuracy of the azimuth display compared to the level A. Further, since correction is performed at level C while the environment is stable, power saving can be greatly reduced compared to level A.

  On the other hand, when the driver 1661 determines that the electronic compass mode is selected (step A1; electronic compass), the driver 1661 performs azimuth measurement in steps A31 to A45. Note that the processing of steps A31 to A37 is processing in the electronic compass mode when the correction level is set to level A, and is the same processing as steps A3 to A9 described above, but will not be described. When the number of times exceeds three, the correction level is switched to level B, and the sensor unit 175 is driven with a driving period of 200 ms to acquire magnetic field information (step A39). Then, the offset correction value is calculated based on the acquired magnetic field information, the offset correction value table 1671 is updated (step A41), the direction calculation is performed, and the calculation result is output to the direction measurement application (step A43). .

  Next, the driver 1661 determines whether or not a sudden change in the ambient magnetic field or a temperature change in the sensor unit 175 has been detected based on the environmental change condition (step A45). Specifically, when the magnetic voltage value detected by the magnetic sensor 178 exceeds the range, it is determined that the surrounding magnetic field has changed significantly. Further, when the temperature detected by the temperature sensor 177 changes more than a certain value, it is determined that the temperature change of the sensor unit 175 has been detected.

  If the driver 1661 determines that an abrupt change in the ambient magnetic field or a temperature change in the sensor unit 175 has been detected (step A45; Yes), the driver 1661 switches the correction level to level A and proceeds to the processing in step A31. As described above, when a sudden change in the peripheral magnetic field or a temperature change in the sensor unit 175 occurs, the correction level is switched to the level A to facilitate the calculation of the offset correction value and the correction of the magnetic field information.

  In addition, since the azimuth | direction calculation in step A43 is performed based on the magnetic field information correct | amended at the level B, a calculation result with a higher precision than the calculation result in step A35 is obtained. For this reason, the accuracy of the azimuth display can be improved as compared with the level A. Further, since the correction is performed at the level B while the environment is stable, the power saving can be greatly reduced compared to the level A.

  As described above, when the display mode is the electronic compass mode, the driver 1661 switches the correction level from the level A to the level B, calculates the offset correction value, and corrects the magnetic field information output from the sensor unit 175. Do. Then, an azimuth calculation is performed based on the magnetic field information and output to the azimuth measurement application.

  At this time, since the electronic compass mode is set in the azimuth measurement application, the electronic compass 55 having the 16-division azimuth and the magnetic needle 54 indicating the azimuth are displayed on the main display unit as shown in FIG. 2 and the azimuth angle 53 is displayed numerically (step B11). When the second azimuth measurement button 35 is pressed, a simplified display screen of FIG. 6A is displayed on the sub display unit 5. As described above, in the electronic compass mode, the driving cycle of the sensor unit 175 is switched between 100 ms and 200 ms according to the correction level, so that the correction accuracy can be increased in a shorter period than in the navigation mode.

  As described above, according to this embodiment, the correction level is provided in two stages, and the correction level is increased step by step as the offset correction value is calculated and the azimuth calculation is performed, and the drive cycle of the magnetic sensor 178 is lengthened. . For this reason, the magnetic field information data can be varied, and the calculation accuracy of the offset correction value is increased. Therefore, as the azimuth measurement proceeds, the magnetic field information correction accuracy can be increased, and the power for driving the magnetic sensor 178 can be reduced.

  In addition, when a rapid fluctuation of the surrounding magnetic field or a temperature change of the sensor unit 175 is detected, the correction level is returned to level A, and the number of pieces of magnetic field information to be acquired is increased, so that a high-speed and rough offset correction value is obtained. Can be easily calculated.

  Also, by changing the driving frequency of each correction level between the electronic compass mode and the navigation mode, the electronic compass mode maintains the accuracy of the azimuth angle for numerical display. It is possible to save power while maintaining the accuracy that does not exceed.

  In this embodiment, the sudden change of the peripheral magnetic field is determined based on the output of the magnetic sensor 178 and the correction level is switched to the level A. For example, the communication unit 90 or the audio output unit 80 It may be switched to level A when driving is detected. In general, when data communication is performed by driving the communication unit 90, electromagnetic waves are generated by transmission and reception of radio waves, and the surrounding magnetic field fluctuates. Electromagnetic waves are also generated from the speakers 8 and 9 of the audio output unit 80. For this reason, it is of course possible to obtain the same effect as this embodiment by determining that the peripheral magnetic field has changed suddenly by driving the communication unit 90 and the audio output unit 80 and switching the correction level to level A. It is.

  Further, the azimuth measuring device of the present invention is applied to a mobile phone, but it can be applied to small electronic devices such as PDA (Personal Digital Assistant), PHS, and the like. It can also be applied to notebook computers.

An example of (a) front view and (b) rear view of the mobile phone in the present embodiment. The block diagram which shows an example of a function structure of a mobile telephone. The timing chart of the sensor unit for every correction level in electronic compass mode and navigation mode. The flowchart for demonstrating the processing operation on the driver side. The flowchart for demonstrating the specific processing operation by the direction measurement application side. (A) is a display example in the electronic compass mode, and (b) is a display example in the navigation mode.

Explanation of symbols

2 Main display section (display means)
3 Input section (setting means)
5 Sub display section (display means)
16 communication control unit 40 GPS reception unit 60 display control unit 66 control unit 70 camera unit 80 audio output unit 90 communication unit 100 mobile phone 166 control unit (correction value calculation means, azimuth calculation means, control means)
175 Sensor unit 177 Temperature sensor 178 Magnetic sensor (magnetic detection means, magnetic detection unit)
1661 Driver 1671 Offset correction value table

Claims (4)

Magnetic detection means for detecting the surrounding magnetism and outputting as magnetic field information;
Correction value calculation means for calculating a correction value based on magnetic field information output when the magnetic detection means is driven;
Based on the correction value calculated by the correction value calculation means, the azimuth calculation means for correcting the magnetic field information output from the magnetic detection means and performing azimuth calculation;
Display means for displaying a calculation result by the azimuth calculation means;
Setting means for setting the display mode of the calculation result displayed on the display means;
An azimuth measuring apparatus comprising: a control unit that controls a driving cycle of the magnetic detection unit based on a setting content by the setting unit. The display mode set by the setting means includes a numerical display of the azimuth calculated by the azimuth calculating means and a schematic display of the azimuth.
2. The azimuth according to claim 1, wherein when the numerical display is set by the setting unit, the control unit shortens the driving cycle of the magnetic detection unit than when the schematic display is set. Measuring device. A correction value calculating step for calculating a correction value based on magnetic field information output when the magnetic detection unit is driven;
Based on the correction value calculated in the correction value calculation step, the azimuth calculation step for correcting the output magnetic field information and performing the azimuth calculation;
A display step for displaying a calculation result in the azimuth calculation step;
A setting step for setting a display mode of the calculation result displayed in this display step;
A azimuth measuring method, comprising: a control step for controlling a driving cycle of the magnetic detection unit based on setting contents in the setting step. On the computer,
A correction value calculation function for calculating a correction value based on magnetic field information output when the magnetic detection unit is driven;
Based on the correction value calculated by the correction value calculation function, the azimuth calculation function for correcting the output magnetic field information and performing the azimuth calculation;
A display function to display the calculation result by this azimuth calculation function;
A setting function for setting a display mode of a calculation result displayed by the display function;
And a control function for controlling a drive cycle of the magnetic detection unit based on the setting content of the setting function.

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