JP2008202988A - Position detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detection device capable of improving reliability of the device by preventing malfunction when a magnetic field change detection element is broken or failed, and by preventing breakage or failure of a position detection device by allowing an eddy current to flow in the magnetic field change detection element, in the position detection device for detecting a relative position between a magnetic field generator and the magnetic field change detection element. <P>SOLUTION: The sum of each signal from a plurality of magnetic field change detection elements 1, 2 arranged mutually separately, for outputting each signal corresponding to a distance to the magnetic field generator 7 is operated by a sum signal generation circuit 4, and the operated sun signal is output to a detection circuit 6. The detection circuit 6 detects fluctuation from a set value of the sum signal, and when the fluctuation continues as long as a prescribed time or longer, outputs a signal showing the effect to a control circuit 5, to thereby stop operation of the control circuit 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a position detection device used in a camera shake correction mechanism or the like of an imaging device, and more particularly to a position detection device that performs position detection based on a relative position between a magnetic field generator and a magnetic field change detection element.

Conventionally, in an imaging device such as a camera, imaging of an image sensor caused by camera shake or the like is caused by shifting the optical system or the image sensor in a plane direction perpendicular to the optical axis in accordance with the amount of camera shake occurring during shooting. Various camera shake correction mechanisms that suppress image blur on the surface have been proposed. In such a camera shake correction mechanism, a position detection device is used to detect the shift position of the optical system or the image sensor. There are various types of such position detection devices. For example, there is one using a magnetic field generator and a magnetic field change detection element disclosed in Patent Document 1. This Patent Document 1 describes a position detection circuit that can easily perform compensation for solid-state variations of a magnetic field generator, and a technique related thereto.
JP 2005-331399 A

  Here, the magnetic field change detecting element is generally an element having a low electrostatic resistance. Therefore, when the magnetic field change detecting element is destroyed or broken down due to static electricity or the like, the magnetic field change detecting element malfunctions and the position is erroneously detected. Although there is a risk of failure, Patent Document 1 does not take this point into consideration.

  The present invention has been made in view of the above circumstances, and in a position detection device that detects the relative position between a magnetic field generator and a magnetic field change detection element, prevents malfunction when the magnetic field change detection element is broken or failed. An object of the present invention is to provide a position detecting device capable of preventing the position detecting device from being broken or broken due to an overcurrent flowing through the magnetic field change detecting element and improving the reliability of the device.

  In order to achieve the above object, a position detection device according to a first aspect of the present invention includes a plurality of magnetic field change detection elements that are arranged apart from each other and output a signal corresponding to a distance from a magnetic field generator, A position signal generation circuit configured to generate a signal indicating a relative position between the magnetic field generator and the plurality of magnetic field change detection elements based on a difference between the signals from the plurality of magnetic field change detection elements; A sum signal generation circuit that outputs the sum of each signal from the magnetic field change detection element; a control circuit that controls the plurality of magnetic field change detection elements so that the sum signal from the sum signal generation circuit is constant; and And a detection circuit that detects a change from a set value of the sum signal and generates and outputs a signal for stopping the function of the control circuit based on the change.

  According to the present invention, in the position detection device that detects the relative position between the magnetic field generator and the magnetic field change detection element, the magnetic field change detection element is prevented from malfunctioning when the magnetic field change detection element is broken or failed, and the magnetic field change detection element has an overcurrent. It is possible to provide a position detecting device that can prevent the position detecting device from being destroyed or broken due to the flow of the air and improve the reliability of the device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, a first embodiment of the present invention will be described. FIG. 1 is a diagram illustrating a configuration of an imaging apparatus including a position detection apparatus according to the first embodiment of the present invention. The imaging apparatus illustrated in FIG. 1 includes a position detection device 101, an imaging unit 102, a shake amount detection circuit 103, a CPU 104, a drive circuit 105, and an external device 106.

  The position detection device 101 includes magnetic field change detection elements 1 and 2, a position signal generation circuit 3, a sum signal generation circuit 4, a control circuit 5, and a detection circuit 6.

  The magnetic field change detection elements 1 and 2 are arranged so as to be spaced apart from each other so as to sandwich the magnetic field generator 7 provided in the imaging unit 102, and correspond to the distance from the magnetic field generator 7 provided in the imaging unit 102, respectively. Output a signal. For example, Hall sensors are used as the magnetic field change detection elements 1 and 2.

  The position signal generation circuit 3 calculates a difference between output signals from the magnetic field change detection elements 1 and 2, and uses the difference signal as a relative positional relationship between the magnetic field generator 7 and the magnetic field change detection elements 1 and 2. Is output to the CPU 104 as a signal indicating.

  Here, in FIG. 1, only two (one set) magnetic field change detection elements are illustrated in order to simplify the following description. In this case, it is possible to detect movement in one direction of the image sensor 8. In an actual blur correction mechanism, it is necessary to move the image sensor 8 on a plane perpendicular to the optical axis of an optical system (not shown) for blur correction. Therefore, when the position detection device 101 is used for the camera shake correction mechanism. Requires at least four (two sets) of magnetic field change detecting elements.

  The sum signal generation circuit 4 calculates the sum of output signals from the magnetic field change detection elements 1 and 2, and uses the calculated sum signal as correction information for the magnetic field change detection elements 1 and 2. Output to. The control circuit 5 detects the sum signal from the sum signal generation circuit 4 and controls the current supplied to the magnetic field change detection elements 1 and 2 so that the detected sum signal becomes a constant value.

  The detection circuit 6 detects a change in the sum signal from the sum signal generation circuit 4 and is a signal for stopping the operation of the control circuit 5 when the detected change of the sum signal has continued for a predetermined time or more. And a signal indicating that the sum signal is not constant is output to the CPU 104.

  The imaging unit 102 includes a magnetic field generator 7 and an imaging element 8. The magnetic field generator 7 is an element that permanently generates a magnetic field. The magnetic field generator 7 is not particularly limited as long as it can generate a magnetic field continuously. For example, a permanent magnet or an electromagnet can be used. The image sensor 8 converts an optical signal from a subject (not shown) into an electrical image signal and outputs it to an image processing circuit (not shown). The magnetic field generator 7 is fixed on the same substrate as the image sensor 8, and the position of the image sensor 8 can be detected by the position detection device 101. Here, as the image sensor 8, for example, a CCD image sensor or a CMOS image sensor can be used.

  The blur amount detection circuit 103 includes, for example, an angular velocity sensor, detects the blur amount of the imaging apparatus, and outputs a signal indicating the detected blur amount to the CPU 104.

  The CPU 104 controls each block of the imaging device. At the time of blur correction, the CPU 104 takes in a signal indicating the blur amount from the blur amount detection circuit 103 and an output signal from the position signal generation circuit 3 as digital signals, and controls the control signal of the drive circuit 105 based on these signals. Is output to the drive circuit 105. When a signal indicating that the sum signal is not constant is received from the detection circuit 6, a control signal is output to the external device 106.

  The drive circuit 105 includes a motor or the like, and receives a control signal from the CPU 104 to drive the imaging unit 102 in a plane direction perpendicular to the optical axis of an optical system (not shown). The external device 106 presents to the operator that the magnetic field change detection elements 1 and 2 are abnormal based on a control signal from the CPU 104.

Hereinafter, the operation relating to the camera shake correction of the imaging apparatus shown in FIG. 1 will be described.
The blur amount detection circuit 103 detects the blur amount of the imaging apparatus at the time of shooting and outputs a signal corresponding to the detected blur amount to the CPU 104. The CPU 104 moves the image sensor 8 by controlling the drive circuit 105 in accordance with the output signal from the blur amount detection circuit 103. As the imaging element 8 moves, the relative positional relationship between the magnetic field generator 7 and the magnetic field change detection elements 1 and 2 changes. The magnetic field change detection elements 1 and 2 output signals corresponding to the distance from the magnetic field generator 7 to the position signal generation circuit 3 and the sum signal generation circuit 4, respectively.

  The position signal generation circuit 3 calculates the difference between the output signal from the magnetic field change detection element 1 and the output signal from the magnetic field change detection element 2, and sends the calculated difference signal to the CPU 104 as a signal indicating the position of the magnetic field generator 7. Output. The CPU 104 compares the signal indicating the position of the magnetic field generator 7 output from the position signal generation circuit 3 with the signal indicating the blur amount of the imaging device output from the blur amount detection circuit 103 while comparing the signal of the imaging device. The drive circuit 105 is controlled until the image sensor 8 moves to an optimum position where the blur is canceled.

  On the other hand, the sum signal generation circuit 4 calculates the sum of the output signal from the magnetic field change detecting element 1 and the output signal from the magnetic field change detecting element 2, and uses the calculated sum signal as correction information for the magnetic field change detecting elements 1 and 2. To the control circuit 5 and the detection circuit 6. The control circuit 5 adjusts the current supplied to each of the magnetic field change detection elements 1 and 2 so that the sum signal from the sum signal generation circuit 4 is constant. That is, when the sum signal from the sum signal generation circuit 4 is about to increase, the control circuit 5 decreases the current supplied to the magnetic field change detection elements 1 and 2 and decreases the output signal of the magnetic field change detection elements 1 and 2. As a result, the sum signal from the sum signal generation circuit 4 is reduced. On the other hand, when the sum signal from the sum signal generation circuit 4 is about to decrease, the control circuit 5 increases the current supplied to the magnetic field change detection elements 1 and 2 to increase the output signal of the magnetic field change detection elements 1 and 2. As a result, the sum signal from the sum signal generation circuit 4 is increased. By performing such a negative feedback operation, the influence of individual variations of the magnetic field generator 7 is canceled, and a signal corresponding to the relative positional relationship between the magnetic field generator 7 and the magnetic field change detection elements 1 and 2 is accurately obtained. Can be detected.

  The detection circuit 6 detects a change from the set value (value to be constant) of the sum signal from the sum signal generation circuit 4, and stops the operation of the control circuit 5 when the change continues for a certain time or more. The signal for making it output is output to the control circuit 5.

  Here, as described above, a Hall sensor generated from a magnetic resistance is often used for the magnetic field change detection elements 1 and 2, but the Hall sensor generally has a low electrostatic withstand voltage, and the magnetic resistance is open or short. Often leads to failure. In this case, the sum signal from the sum signal generation circuit 4 does not become constant with respect to the set value, and the position signal generation circuit 3 determines the relative relationship between the magnetic field generator 7 and the magnetic field change detection elements 1 and 2. The positional relationship, that is, the position information of the magnetic field generator 7 cannot be accurately detected. Furthermore, when the negative feedback operation as described above is performed in a state where the Hall sensor is short-circuited, the sum signal generation circuit 4 calculates the sum of output signals from the magnetic field change detection elements 1 and 2 as 0, and as a result Since the control circuit 5 supplies an excessive current more than necessary to the magnetic field change detecting elements 1 and 2, the position detecting device 101 also fails.

  Therefore, while the sum signal from the sum signal generation circuit 4 is in the vicinity of the set value that should be constant, the position signal generation circuit 3 determines the difference between the signals from the magnetic field change detection elements 1 and 2 as the magnetic field generator 7. Is output to the CPU 104 as position information. On the other hand, when the sum signal from the sum signal generation circuit 4 greatly fluctuates from a set value that should be constant, the detection circuit 6 outputs the input signal to the magnetic field change detection elements 1 and 2 in the control circuit 5. The control function is stopped, and the detection circuit 6 notifies the CPU 104 that an abnormality has occurred in the magnetic field change detection elements 1 and 2. The CPU 104 notifies the external device 106 that the correct position detection of the image sensor 8 cannot be performed due to an abnormality in the magnetic field change detection elements 1 and 2, and as a result, correct camera shake correction cannot be performed. The external device 106 presents to the operator of the imaging device that the magnetic field change detection elements 1 and 2 are in an abnormal state. This method is performed by causing an LED to emit light in order to visually notify the abnormal state, or by generating an alarm sound in order to audibly notify the abnormal state. In FIG. 1, the abnormality of the magnetic field change detection elements 1 and 2 detected by the detection circuit 6 is notified to the external device 106 via the CPU 104, but directly from the detection circuit 6 to the external device 106. Information indicating that it is abnormal may be notified.

  As described above, according to the first embodiment, even when the magnetic field change detecting elements 1 and 2 fail due to electrostatic breakdown or the like, the position detecting device 101 is prevented from malfunctioning and the magnetic field change detecting element is excessively damaged. It is possible to prevent the position detection device from being broken or broken due to the flow of current, and to improve the reliability of the camera shake correction function in the imaging device. In addition, when an abnormality occurs in the magnetic field change detection elements 1 and 2, the external device 106 indicates to the operator that the camera shake correction cannot be performed correctly. Can be grasped.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 2 is a diagram illustrating a configuration of an imaging apparatus including a position detection apparatus according to the second embodiment of the present invention. The second embodiment shows an example of the configuration of the detection circuit 6 in the position detection device. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  The detection circuit 6 illustrated in FIG. 2 includes a first comparator 21, a transistor 22, a constant current source 23, a capacitor 24, and a second comparator 25.

  The first comparator 21 receives the sum signal from the sum signal generation circuit 4 and the reference voltage 1, compares the magnitude relationship between them, and outputs the result to the transistor 22. In the circuit of FIG. 2, the first comparator 21 outputs an L level when the sum signal from the sum signal generation circuit 4 is smaller than the reference voltage 1, and outputs an H level when it is larger. Here, the reference voltage 1 is set to a voltage value indicating an allowable limit value of fluctuation of the sum signal, for example.

  The transistor 22 is turned on or off according to the output signal of the first comparator 21. The constant current source 23 generates and outputs a reference current for charging the capacitor 24. The capacitor 24 is charged by the reference current from the constant current source 23 and delays the output signal of the first comparator 21.

  The voltage charged in the capacitor 24 and the reference voltage 2 are input to the second comparator 25, the magnitude relationship between these is compared, and the result is output to the control circuit 5. In the circuit of FIG. 2, the second comparator 25 outputs an H level when the charging voltage of the capacitor 24 is smaller than the reference voltage 2 and outputs an L level when it is larger.

Hereinafter, the operation of the detection circuit 6 shown in FIG. 2 will be described.
In normal times when no abnormality has occurred in the magnetic field change detection elements 1 and 2, the sum signal from the sum signal generation circuit 4 fluctuates in the vicinity of a set value that should be constant and exceeds the reference voltage 1. Yes. In this state, the first comparator 21 outputs the H level and turns on the transistor 22. In this case, the capacitor 24 is not charged, and as a result, the output of the second comparator 25 is also at the H level. The control circuit 5 determines the level of the output signal from the second comparator 25. If the output signal from the second comparator 25 is at the H level, an abnormality occurs in the magnetic field change detection elements 1 and 2. If not, the current supplied to the magnetic field change detection elements 1 and 2 is controlled in accordance with the change from the set value of the sum signal from the sum signal generation circuit 4.

  On the other hand, when an abnormality occurs in the magnetic field change detection elements 1 and 2, each output becomes a value close to 0. Therefore, the sum signal from the sum signal generation circuit 4 becomes smaller than the reference voltage 1, and the first The comparator 21 outputs the L level and turns off the transistor 22. Thereby, the capacitor 24 is charged by the reference current from the constant current source 23. If this state continues, the charging voltage of the capacitor 24 will eventually become higher than the reference voltage 2. At this time, the second comparator 25 outputs an L level. When the control circuit 5 receives an L level signal from the second comparator 25, it assumes that an abnormality has occurred in the magnetic field change detection elements 1 and 2, and stops supplying current to the magnetic field change detection elements 1 and 2. To do.

Here, the time until the voltage charged to the capacitor 24 becomes larger than the reference voltage 2 is T, the voltage charged to the capacitor 24 is V, the reference current supplied from the constant current source 23 to the capacitor 24 is I, When the capacitance value of the capacitor 24 is C, the following (Formula 1) is established.
T = CV / I (Formula 1)
This (Equation 1) indicates that the charging voltage of the capacitor 24 reaches the reference voltage 2 when the state in which the sum signal from the sum signal generation circuit 4 is smaller than the reference voltage 1 continues for the time T in (Equation 1). The second comparator 25 outputs an L level, indicating that the supply of current to the magnetic field change detection elements 1 and 2 by the control circuit 5 is stopped. That is, with the circuit configuration as shown in FIG. 2, it is possible not to detect instantaneous fluctuations of the sum signal from the sum signal generation circuit 4.

  Here, since the sum signal from the sum signal generation circuit 4 is indefinite for a certain period after the imaging apparatus is turned on, the detection circuit 6 cannot perform a normal detection operation during this period. Therefore, it is desirable that the operation of the detection circuit 6 is stopped by the CPU 104 for a certain period after the power is turned on, and the operation of the detection circuit 6 is started after the lapse of the certain period.

  As described above, according to the second embodiment, the output signal of the first comparator 21 is delayed by the capacitor 24 so that instantaneous fluctuation of the sum signal from the sum signal generation circuit 4 is not detected. Thus, it is possible to prevent erroneous detection of fluctuations in the sum signal. Further, by stopping the operation of the detection circuit 6 for a certain period after the power is turned on, it is possible to prevent erroneous detection of the fluctuation of the sum signal immediately after the power is turned on.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 3 is a diagram illustrating a configuration of an imaging apparatus including a position detection apparatus according to the third embodiment of the present invention. In the third embodiment, the function of the detection circuit 6 in the position detection device is digitized and incorporated in the CPU 104. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  The CPU 104 captures, as digital signals, a signal indicating the position of the magnetic field generator 7 output from the position signal generation circuit 3 and a signal indicating the blur amount of the imaging apparatus during shooting output from the blur amount detection circuit 103. While comparing, the drive circuit 105 is controlled until the image pickup device 8 moves to an optimum position where the blur of the image pickup apparatus is canceled. Further, the CPU 104 digitizes and takes in the sum signal from the sum signal generation circuit 4, determines whether the sum signal has greatly fluctuated from the set value, and if the fluctuation of the sum signal continues for a certain time or longer, the CPU 104 Stop operation. That is, the CPU 104 continues to sample the sum signal from the sum signal generation circuit 4 at an arbitrary time interval, and stops the operation of the control circuit 5 when the change from the set value of the sum signal continues for a certain time or more. Let As described in the second embodiment, the sum signal detection operation cannot be performed for a certain period after the imaging apparatus is turned on. Therefore, the operation of the control circuit 5 should not be stopped during that period. Is desirable.

  As described above, according to the third embodiment, since it is not necessary to provide the detection circuit 6 as an analog circuit in the position detection device 101, the circuit configuration is simplified, the imaging device is reduced in size, and the power consumption is reduced. It is possible to

  Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and applications are naturally possible within the scope of the gist of the present invention. For example, in each of the above-described embodiments, an imaging device that performs camera shake correction by moving the imaging element 8 in a plane perpendicular to the optical axis of an optical system (not shown) is taken as an example. The technique can also be applied to an imaging apparatus that performs camera shake correction by moving an optical system. However, in this case, the magnetic field generator 7 is fixed to the optical system instead of the image sensor 8.

  Further, the above-described embodiments include various stages of the invention, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some configuration requirements are deleted from all the configuration requirements shown in the embodiment, the above-described problem can be solved, and this configuration requirement is deleted when the above-described effects can be obtained. The configuration can also be extracted as an invention.

It is a figure which shows the structure of the imaging device containing the position detection apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the structure of the imaging device containing the position detection apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structure of the imaging device containing the position detection apparatus which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 2 ... Magnetic field change detection element, 3 ... Position signal generation circuit, 4 ... Sum signal generation circuit, 5 ... Control circuit, 6 ... Detection circuit, 7 ... Magnetic field generator, 8 ... Image sensor, 21 ... 1st comparator , 22 ... transistor, 23 ... constant current source, 24 ... capacitor, 25 ... second comparator, 101 ... position detection device, 102 ... imaging unit, 103 ... blur amount detection circuit, 104 ... CPU, 105 ... drive circuit, 106 ... External device

Claims (7)

A plurality of magnetic field change detection elements that are arranged apart from each other and output a signal corresponding to the distance from the magnetic field generator;
A position signal generation circuit that generates a signal indicating a relative position between the magnetic field generator and the plurality of magnetic field change detection elements based on a difference between signals from the plurality of magnetic field change detection elements;
A sum signal generation circuit that outputs a sum of signals from the plurality of magnetic field change detection elements;
A control circuit that controls the plurality of magnetic field change detection elements so that a sum signal from the sum signal generation circuit is constant;
A detection circuit that detects a change from the set value of the sum signal and generates and outputs a signal for stopping the function of the control circuit based on the change;
A position detection apparatus comprising:   The position detection device according to claim 1, further comprising a signal output circuit that outputs a signal indicating that the magnetic field change detection element is abnormal to an external device based on an output signal from the detection circuit. .   The position detection device according to claim 2, wherein the external device receives a signal from the signal output circuit and presents the operator with an abnormality in the magnetic field conversion detection element.   The position detection according to claim 1, wherein the detection circuit generates a signal for stopping the function of the control circuit when a change from the set value of the sum signal continues for a predetermined time or more. apparatus. The detection circuit includes:
A first comparator that outputs a signal indicating a magnitude relationship between the sum signal and a set value of the sum signal;
A delay circuit for delaying the output from the first comparator by the predetermined time;
A second comparator that outputs a signal for stopping the function of the control circuit based on the output from the first comparator delayed by the delay circuit;
The position detection device according to claim 4, comprising:   6. The detection circuit stops generation of a signal for stopping the function of the control circuit within a period from when the power is turned on until the sum signal from the sum signal generation circuit is stabilized. The position detection device according to any one of the above.   The said detection circuit converts the output from the said sum signal generation circuit into a digital signal, and produces | generates the signal which stops the function of the said control circuit based on this digital signal. The position detection device according to any one of 4 and 6.

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