JP2019114920A - Actuator driver, imaging apparatus using the same, and calibration method - Google Patents

Abstract

To provide an imaging apparatus which is less susceptible to changes in environmental temperature and capable of high-accuracy and high-speed positioning of an imaging lens.SOLUTION: A calibration is performed to adjust a gain and/or an offset of a position detection signal Sso that the position detection signals Sof a position detection element 404 at a first end and a second end for mechanically restricting both ends of a movable range of an actuator movable portion on which an imaging lens 304 is mounted have a predetermined value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an actuator driver, an imaging apparatus using the same, and a calibration method.

  2. Description of the Related Art In recent years, in camera modules mounted on smartphones and the like, there is an increase in those incorporating a function to control the position of an imaging lens with high accuracy and at high speed by detecting the position of the imaging lens and feeding back this position information. ing. By incorporating feedback control into the autofocus operation, high-precision and high-speed autofocus becomes possible. Also, by incorporating feedback control as optical image stabilization (OIS), high accuracy image stabilization becomes possible. In a camera incorporating such feedback control, control errors may occur if the position detection signal changes with temperature.

  In particular, in an imaging apparatus provided with an imaging element (image sensor) capable of phase difference detection for auto focusing, direct imaging is performed up to the output value of the position detection signal corresponding to the in-focus position determined by phase difference detection. By displacing the lens, high-speed autofocusing is enabled, but if the relationship between the in-focus position and the output value of the position detection signal deviates due to temperature change, the lens deviates from the in-focus position. It will be accessed and it will take additional time to focus.

  In addition, in an imaging apparatus provided with a plurality of camera modules called a dual camera or the like, it may be necessary to control the movement of the plurality of camera modules while interlocking them. Even in such a case, if the relationship between the position detection signal and the actual displacement deviates due to temperature, the link between the two camera modules may be broken, which may affect the generated image. There is.

  In Patent Document 1, an environmental temperature is detected based on the resistance value of the shape memory alloy, and a drive that corrects the inclination component and the offset component between the control value-displacement characteristic according to the difference between the environmental temperature and the reference temperature. An apparatus is disclosed. Patent Document 2 discloses a position detection device that corrects position information detected according to a difference between a reference temperature and an ambient temperature.

WO2009 / 093645 gazette JP 2013-205550 A

  In the technique described in Patent Document 1, it is necessary to measure temperature characteristics in advance and to define a temperature coefficient for correction. Also, assuming that the correction value of the control value is proportional to the difference between the environmental temperature and the reference temperature, the temperature coefficient as a proportional constant is determined, and if the temperature coefficient differs depending on the environmental temperature, the temperature coefficient is calculated for each environmental temperature. It is necessary to determine, and a large memory capacity is also required to store the temperature coefficient for each temperature.

  Similarly, in the technique described in Patent Document 2, it is necessary to measure the temperature characteristic in advance and to define the temperature coefficient for correction. Further, the temperature coefficient as a proportional constant is defined as that the correction amount of the control value is proportional to the difference between the environmental temperature and the reference temperature, and when the temperature coefficient differs depending on the environmental temperature, a correction error occurs.

  The present invention has been made in view of such circumstances, and one of the exemplary objects of an aspect thereof is to provide an imaging device capable of high-accuracy and high-speed positioning of an imaging lens.

  One embodiment of the present invention relates to an imaging device. The imaging device includes an imaging lens, an actuator that positions the imaging lens, a position detection element that generates a position detection signal that indicates the position of the imaging lens, and an actuator driver that supplies a drive signal to the actuator. The actuator has a first end and a second end for mechanically restricting both ends of the movable range of the movable portion including the imaging lens. The actuator driver is configured to be able to perform calibration such that the position detection value based on the position detection signal at the first end becomes a first predetermined value and the position detection value becomes a second predetermined value at the second end. Ru.

  Another aspect of the present invention relates to an actuator driver that drives an actuator that positions an imaging lens. The actuator has a first end and a second end for mechanically restricting both ends of the movable range of the movable portion including the imaging lens. The actuator driver generates a drive signal such that the position detection value based on the position detection signal indicating the position of the imaging lens from the position detection element approaches the target value, and the position detection value is first at the first end. And a calibration unit that executes calibration so that the position detection value becomes a second predetermined value at the second end.

  It is to be noted that any combination of the above-described constituent elements, or one in which the constituent elements and expressions of the present invention are mutually replaced among methods, apparatuses, systems, etc. is also effective as an aspect of the present invention.

  Furthermore, the description of the means for solving this problem does not explain all the essential features, and thus the subcombinations of these features to be described may also be the invention.

  According to the present invention, position detection signals can be used under certain conditions without being influenced by changes in the environment, etc., and high-precision and high-speed positioning of the imaging lens becomes possible.

It is a figure showing an imaging device. It is a block diagram of actuator driver IC provided with a calibration function. It is a figure which shows the relationship of the actuator drive current and position detection signal in 1st Embodiment of the imaging device which concerns on this invention. It is a figure explaining correcting a position detection signal by calibration. It is a figure which shows the relationship between the position detection signal after correction | amendment, and AD value. It is a figure which shows the relationship between a target code and an actual lens position. It is a block diagram showing the system configuration of the lens control device in a 2nd embodiment of the imaging device concerning the present invention. It is a flowchart which shows the calibration process of the position detection signal in 2nd Embodiment of the imaging device which concerns on this invention. It is a figure which shows that the relationship between an actuator drive current and a position detection signal changes with temperature. It is a figure which shows the relationship between the actuator drive current after calibrating a position detection signal, and a position detection signal.

  Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and duplicating descriptions will be omitted as appropriate. In addition, the embodiments do not limit the invention and are merely examples, and all the features and combinations thereof described in the embodiments are not necessarily essential to the invention.

  Further, the dimensions (thickness, length, width, etc.) of each member described in the drawings may be scaled appropriately for ease of understanding. Furthermore, the dimensions of a plurality of members do not necessarily represent the magnitude relationship between them, and even if one member A is drawn thicker than another member B in the drawing, the member A is a member B It may be thinner than that.

  In the present specification, “the state in which the member A is connected to the member B” means that the members A and B are electrically connected in addition to the case where the members A and B are physically and directly connected. It also includes the case of indirect connection via other members that do not substantially affect the connection state of the connection or do not impair the function or effect provided by the connection.

  Similarly, "a state where the member C is provided between the member A and the member B" means that the member A and the member C, or the member B and the member C are directly connected, and It also includes the case of indirect connection via other members that do not substantially affect the connection state of the connection or do not impair the function or effect provided by the connection.

In the present embodiment, first, the configuration of an actuator for moving an imaging lens and its peripheral circuits will be briefly described. FIG. 1 is a diagram showing an imaging device. The imaging device 300 is a digital camera, a digital video camera, or a camera module incorporated in a smartphone or a tablet terminal. The imaging device 300 includes an imaging element 302, a lens 304, a processor 306, and a lens control device 400. The lens 304 is disposed on the optical axis of light incident on the imaging element 302. The lens control device 400 positions the lens 304 based on a control signal (referred to as a target code) S _REF indicating the position command value S _REF from the processor 306.

For example, the lens 304 is described as being driven in the optical axis direction as an AF lens. The lens control device 400 displaces the lens 304 in the optical axis direction (Z-axis direction). The processor 306 generates a position command value P _REF so as to increase the contrast of the image captured by the imaging element 302 (contrast AF). Alternatively, the position command value P _REF may be generated based on an output from an AF sensor provided outside the imaging element 302 or embedded in the imaging surface (phase difference AF).

  In one embodiment, the lens 304 may be driven in a direction perpendicular to the optical axis as a camera shake correction lens.

  The lens control device 400 controls the actuator 402 by position feedback. Specifically, the lens control device 400 includes an actuator 402, a position detection element 404, and an actuator driver IC (Integrated Circuit) 500. Although the temperature detection element 406 is not essential for the calibration operation itself, it is necessary when performing calibration by detecting a temperature change during operation as a camera. The actuator 402 is, for example, a voice coil motor, and a movable portion is formed by the lens 304, the holder 308, the coil 310, and the like. On the other hand, when the permanent magnet 312 is disposed in the fixed portion so as to face the coil 310 and a current is applied to the coil 310, the movable portion is driven in the optical axis direction by the magnetic interaction between the coil 310 and the permanent magnet 312. The fixed portion of the voice coil motor is fixed to the housing of the imaging device 300. The movable portion may be supported by a spring so as to be movable in the optical axis direction. Alternatively, it may be guided by a rotating body such as a ball or a sliding body.

As the position detection element 404, for example, a magnetic detection means such as a Hall element is often used, and the explanation here is based on the Hall element. A permanent magnet 314 for position detection is attached to the holder 308 which is a movable part, and a Hall element 316 is attached to the fixed part. When the movable part and the fixed part are displaced relative to each other, the magnetism from the permanent magnet 314 input to the Hall element 316 changes. The Hall element generates an electrical signal (hereinafter also referred to as a position detection signal _SFB ) according to the magnetic change, that is, the displacement of the movable portion of the actuator 402, in other words, the current position of the lens 304. The position detection signal S _FB is fed back to the actuator driver IC 500.

  The temperature detection element 406 may be provided with an element dedicated to temperature detection, such as a thermistor, or may be detected using a change in internal resistance value of the Hall element 316 due to temperature as described later. The temperature information T is also fed back to the actuator driver IC 500.

  The actuator driver IC 500 is a functional IC integrated on one semiconductor substrate. Here, “integration” includes the case where all of the circuit components are formed on a semiconductor substrate, and the case where the main components of the circuit are integrally integrated. The resistor of the part, the capacitor, etc. may be provided outside the semiconductor substrate. By integrating the circuit on one chip, the circuit area can be reduced and the characteristics of the circuit elements can be kept uniform.

The actuator driver IC 500 performs feedback control of the actuator 402 such that the position detection value P _FB corresponding to the feedback position detection signal S _FB matches the position command value P _REF based on the target code S _REF . Note that, for example, the position detection value P _FB may be obtained by amplifying the output voltage of the Hall element 316 as needed and digitally coding it. It is the aim of the present application to carry out a calibration on the digitally coded position detection value P _{FB so} that the same digital code is set for the same position.

  The calibration is performed when the camera is started up. Calibration may be performed at the time of factory shipment, and the setting result of the digital code at that time may be stored in a memory and used at the time of use of the camera. Is likely to change with temperature and age. Therefore, it is desirable to recalibrate when the camera starts up. Furthermore, when a predetermined temperature change or more is detected during use of the camera, it is desirable to re-calibrate the calibration even while the camera is used.

  As described above, by detecting the position of the lens 304 and feeding it back for position control, it is possible to suppress transient vibration in the step response to accelerate convergence or to realize high-speed access to the target position.

  The above is the overall configuration of the imaging device 300. Subsequently, calibration according to the embodiment will be described. FIG. 2 is a block diagram of an actuator driver IC 500 having a calibration function. The actuator driver IC 500 includes an interface circuit 501, a front end circuit 502, a drive unit 503, and a calibration unit 504.

A control signal S _REF indicating the target position of the imaging lens 304 is input from the processor 306 to the actuator driver IC 500. The interface circuit 501 receives a control signal _{S REF,} the driving unit 503 generates a position command value _{P REF} that can be processed.

Further, a position detection signal S _FB indicating the position Z of the imaging lens 304 is input from the position detection element 404 to the actuator driver IC 500. Front-end circuit 502 receives the position detection signal _{S FB,} and generates a driving unit 503 can be processed by the position detection value _{P FB.} For example the front-end circuit 502 may generate the position detection value P _FB amplifies the position detection signal S _FB.

When the drive unit 503 is a digital circuit, the position detection value P _FB is further converted into a digital code.

The drive unit 503 generates the drive signal S _OUT so that the position detection value P _FB based on the position detection signal S _FB approaches the position command value P _REF according to the control signal S _REF , and drives the drive signal S _OUT. Supply to

  As described above, the actuator 402 is provided with the first end E1 and the second end E2 for mechanically restricting both ends of the movable range of the movable portion including the imaging lens 304.

When the movable portion contacts the first end E1, the calibration unit 504 determines that the position detection value P _FB becomes a first predetermined value, and when the movable portion contacts the second end E2, the position detection value P _FB becomes the second predetermined value. Perform calibration so that

The calibration is nothing more than correcting the relationship between the actual position Z of the lens and the position detection value P _FB . The input / output characteristics of the position detection element 404 and the front end circuit 502 are respectively
S _FB = f ₁ (Z)
P _FB = f ₂ (S _FB )
I assume.

Although f ₁ and f ₂ can be arbitrary functions, they can be simply expressed by linear functions.
S _FB = a ₁ × Z + b ₁
P _FB = a ₂ × S _FB + b ₂

The calibration unit 504 may adjust at least one of the gain of the position detecting device 404 (i.e., _a 1), the gain of the front end circuit 502 _{(a 2)} or offset _{(b 2).}

  The calibration will be described with reference to FIGS. Although the following description will be made as a method of calibrating the position detection signal in the AF operation, it may be applied to calibration of the position detection signal in the optical image stabilization (OIS) operation.

  FIG. 3 is a diagram showing the relationship between the actuator drive current of the imaging device and the position detection signal. In FIG. 3, the horizontal axis represents the current value applied to the coil 310 of the actuator 402, and the vertical axis represents the position detection signal (hole detection signal) when the movable portion is displaced by the application of the current. The actuator 402 is provided with mechanical stoppers (the first end E1 and the second end E2) for defining the movable range of the movable portion, and the stopper position on the infinite distance side is the Inf mechanical end and the macro side stopper. The position will be referred to as the Macro mechanical end. A current is applied until the movable part hits the Inf mechanical end and the Macro mechanical end. In the state of no current, it is assumed that the movable part does not contact either mechanical end, and a reverse current is applied to apply to the Inf mechanical end.

  The position of the Inf mechanical end and the position of the Macro mechanical end do not change. It is desirable that the structure be such that changes in its position can be neglected even by environmental changes such as temperature and humidity.

At each mechanical end, the position detection signal does not change even if the applied current is changed, and it has a flat characteristic independent of the current value. The hole detection value _{P FB} in Inf mechanical end _V L, the hole detection value _{P FB} in Macro mechanical end and _{V H.} Between V _L and V _H, the hole detection value P _FB also changes as the applied current changes, and the relationship between the current and the change of the hole detection value P _FB is ideally linear.

FIG. 4 is a diagram for explaining the correction of the position detection signal _SFB . In FIG. 4, the horizontal axis indicates the position Z of the lens, and the vertical axis indicates the position detection value P _FB before calibration (i) and after calibration (ii). The gain and the offset are corrected so that the values V _L and V _H obtained in FIG. 3 become predetermined values V _INF and V _MAC .

Consider the case where the position detection value P _FB is converted to a digital code by the A / D converter. In this case, as the values of _V.sub.INF and _V.sub.MAC , values determined as the specifications of the A / D converter can be used. For example, predetermined values V _INF and V _MAC can select an input voltage corresponding to the minimum code (0) and the maximum code (1023 for 10 bits) of the output (AD value) of the A / D converter. In this case, the calibration is performed by using the position detection element 404 or the front end circuit such that the output (AD value) of the A / D converter at the Inf mechanical end and the output of the A / D converter at the Macro mechanical end coincide with 1023. This is equivalent to adjusting the input / output characteristics (gain and offset) of the circuit 502.

FIG. 5 is a diagram showing the relationship between the position detection value P _FB after calibration and the AD value obtained by digitizing the position command value P _FB . The horizontal axis represents the position detection value P _FB and the vertical axis represents the AD value.

FIG. 6 is a diagram showing the relationship between the target code S _REF after calibration and the actual lens position Z. The horizontal axis indicates the target code S _REF and the vertical axis indicates the position Z of the lens. In FIG. 4, the Inf mechanical end position, the Macro mechanical end position, V _INF and V _MAC are uniquely associated, and in FIG. 5, the V _INF and V _MAC and AD values 0 and 1023 are uniquely associated. As shown in FIG. 6, 0, 1023 of the target code S _REF , the Inf mechanical end position, and the Macro mechanical end position are uniquely associated with each other, and the middle portion thereof is a substantially straight line connecting both ends.

Of course, depending on the structure of the actuator, but also exist poor linearity of the position detection signal, in such a case, it is multiplied by the linear correction with respect to the position detection value P _FB.

  As described above, calibration that uniquely associates the target code with the position is performed.

  As described above, by calibrating the AD value of the hole detection signal at the mechanical end position which is not displaced to a predetermined value, the relationship between the position and the hole detection signal can always be made constant.

  The present invention is understood as the block diagram or the circuit diagram of FIG. 2 or extends to various devices, circuits and methods derived from the above description, and is not limited to a specific configuration. Hereinafter, in order not to narrow the scope of the present invention but to help the understanding of the nature of the invention and the circuit operation and to clarify them, more specific configuration examples and modifications will be described.

  Specific embodiments will be described with reference to FIGS. 7 to 10.

  FIG. 7 is a block diagram showing a system configuration of a lens control apparatus according to an embodiment. In this embodiment, a calibration method will be described, which is also assumed when the temperature change exceeds a predetermined value during use of the camera. Therefore, the lens control device is provided with a temperature detection element, and a case where a Hall element is used as the temperature detection element will be described.

The position detection element (404) is a Hall element 316, generates Hall voltages V ₊ and V ₋ according to the displacement of the movable part of the actuator 402, and supplies the Hall voltages to the hole detection pins (HP and HN) of the actuator driver IC 500. Hall voltages V ₊ and V ₋ correspond to the position detection signal S _FB .

The position detection unit 510 corresponds to the front end circuit 502 described above, and generates a position detection value P _FB indicating the position (displacement) Z of the movable portion of the actuator 402 based on the Hall voltages V ₊ and V _−. , Digitally encode and output it. The position detection unit 510 includes a Hall amplifier 512 that amplifies a Hall voltage, and an A / D converter 514 that converts the output of the Hall amplifier 512 into a digital position detection value _PFB .

  The temperature detection unit 520 generates a temperature detection value T indicating a temperature. The Hall element 316 which is the position detection element 404 is also used as the temperature detection element (406). This utilizes the fact that the internal resistance r of the Hall element 316 has temperature dependency. The temperature detection unit 520 measures the internal resistance r of the Hall element 316 and uses it as information indicating the temperature.

Temperature detection unit 520 includes a constant current circuit 522 and an A / D converter 524. The constant current circuit 522 supplies a predetermined bias current I _BIAS to the Hall element 316. The bias current I _BIAS is also a power supply signal necessary to operate the Hall element 316, so the constant current circuit 522 can be understood as a Hall bias circuit. By adjusting the bias current I _BIAS , the gain of the Hall detection signal can be adjusted.

A voltage drop I _BIAS × r occurs across the Hall element 316. This voltage drop is input to the Hall bias pin (HB). The A / D converter 524 converts the voltage V _HB (= I _BIAS × r) of the HB pin into a digital value T. Specifically, information on the change in resistance can be obtained by dividing V _HB by I _BIAS . Since the bias current I _BIAS is known and constant, the digital value T is a signal proportional to the internal resistance r, and therefore contains information on the temperature of the Hall element 316. Although it is possible to obtain information on the Hall element section by measuring in advance the relationship between the internal resistance r and the temperature, in this embodiment a change in the temperature is detected and a trigger for calibration execution is detected. Therefore, it is not necessary to convert to the temperature value, and the trigger may be used when the change of T becomes equal to or more than the predetermined value.

The calibration unit 530 corresponds to the calibration unit 504 in FIG. The calibration unit 530 issues an instruction to adjust the gain and the offset so that the digital position detection value P _FB becomes a predetermined value, converts the P _FB having the predetermined value into a digital code P _{FB — CMP} , and outputs it. . In order to adjust the gain, the bias current I _BIAS in the constant current circuit 522 is adjusted. To adjust the offset, an offset is applied to the amplifier output of the Hall detection signal. The offset information from the calibration unit 530 is converted to an analog value through the D / A converter 516, and is supplied to the amplifier 512. The calibration unit 530 includes a calibration MPU 532 as a processor that performs arithmetic processing and the like, and a memory 534 that stores temperature information and the like at the time of previous calibration execution.

The interface circuit 540 corresponds to the interface circuit (501) of FIG. The interface circuit 540 receives, from the processor 306, a target code TC indicating the target position of the movable part of the actuator 402. This target code TC is the control signal S _REF of FIG. For example, interface circuit 540 may be a serial interface such as I ² C (Inter IC). The filter 550 filters the target code TC received by the interface circuit 540 to generate a position command value P _REF . When the position command value P _REF changes rapidly, the position of the lens 304 may ring. The filter 550 suppresses this ringing.

The controller 560 and the driver unit 570 correspond to the drive unit 503 in FIG. Controller 560 receives position command value P _REF and position detection value P _{FB — CMP} after correction. Controller 560 generates control command value S _REF such that position detection value P _{FB — CMP} matches position command value P _REF . When the actuator 402 is a voice coil motor, the control command value S _REF is a command value of drive current to be supplied to the voice coil motor. Controller 560 includes, for example, an error detector 562 and a PID controller 564. The error detector 562 generates a difference (error) ΔP between the position detection value P _{FB — CMP} and the position command value P _REF . The PID controller 564 generates a control command value S _REF by PID (proportional-integral-derivative) operation. Instead of the PID controller 564, a PI controller may be used, or non-linear control may be employed.

When operating the controller 560, the switch 566 is connected to the terminal 566a side. The driver unit 570 supplies a drive current corresponding to the control command value S _REF to the actuator 402.

When calibration is performed, the switch 566 is connected to the terminal 566b. In response to an instruction from the calibration unit 530, the driver unit 570 supplies a current to the actuator 402 such that the movable portion of the actuator 402 hits the Inf mechanical end and the Macro mechanical end, and the detection signals V _L and V _H from the Hall element 316 Get The calibration unit 532 _issues an instruction to adjust the gain and the offset in the hole detection so that V _L and V _H become predetermined digital values V _INF and V _MAC . Then, between V _INF and V _MAC is divided into 1024, for example, and target codes of 0 to 1023 are set, and calibration is temporarily ended. When the calibration is completed, the switch 566 is connected to the terminal 566a side.

  Such calibration operation is performed at the time of camera start-up or the like. Calibration may be performed at the time of factory shipment, and conditions such as temperature at that time and calibration results may be stored in the memory 534. If the environment at the time of camera startup can be regarded as the same as the conditions at the time of factory shipment including the temperature, or if it is judged that the temperature etc. is the same, calibration at the time of camera startup may not be performed. . If calibration is always performed when the camera is started, the influence of temperature change from the time of factory shipment can be removed, so it is not necessary to perform temperature detection and the temperature detection element is also unnecessary. However, when the influence of the temperature change during camera use can not be ignored, the temperature detection element may be used to perform calibration again when the temperature change from the previous calibration execution exceeds the predetermined value. desirable.

  FIG. 8 is a flowchart showing calibration processing in the actuator driver IC 500 of FIG.

In processing 1 and processing 2, the calibration process is forcibly started at least once at the time of factory shipment, at the time of camera startup, or the like. In order to start the calibration process, first, in process 3, the switch 566 is connected to the terminal 566b on the calibration side. In process 4, the movable portion of the actuator is displaced from the Inf mechanical end to the Macro mechanical end (a current is supplied so as to be displaced). In processing 5, the hole detection signals V _L and V _H at the respective mechanical ends are read. In processing 6, the bias current and the offset are adjusted so that V _L and V _H have predetermined values V _INF and V _MAC, and the obtained V _INF and V _MAC are converted into digital values. In step _7, in response to the _{V INF} and _{V MAC,} it sets the digital code of the Hall signal. For example, it is set as a target code from 0 to 1023. Thus, the calibration process is completed (process 8). When calibration is completed, servo control is started (process 9). In order to execute servo control, the switch 566 is connected to the terminal 566a on the PID control side in process 10.

  Temperature monitoring is always performed to detect a change from the temperature when the previous calibration was performed. In the process 11, it is determined whether or not the temperature change from the previous calibration time is equal to or more than a predetermined value, and if the temperature change becomes equal to or more than the predetermined value, the calibration is redone. Here, the predetermined value may be the temperature change amount itself, or the change amount of the internal resistance value of the Hall element corresponding to the temperature change may be the predetermined value. The predetermined temperature change may be set to, for example, about 1 ° C. or about 5 ° C. Depending on the size of the temperature characteristic of the Hall element or the position detection magnet, the influence of the temperature change can not be ignored.

  If the temperature change is less than the predetermined value, imaging may be performed as it is (process 12). In processing 13, it is determined whether to continue imaging. If continuing as it is, it is determined again whether the temperature change exceeds the predetermined value. If the imaging is not continued, the servo control is ended (process 14), and the camera operation is ended (process 15). Even when the servo control is actually turned off and the camera mode is not turned off, for example, when the user interrupts imaging for a certain period of time, it may be a trigger to return to the start of the flowchart.

  If the temperature change exceeds a predetermined value during shooting of a moving image or the like, this may cause interruption of imaging. For example, the condition may be made variable, such as setting the predetermined value of the temperature change to a larger value only in the moving image mode. The calibration may be re-done at the timing at which imaging was temporarily interrupted.

  If the user is looking at the preview screen even during the calibration operation, the image of the image is temporarily distorted (for example, out of focus) due to the movement of the lens, so that the user is notified that the calibration is in progress. It is better.

  Next, an example of what a hole detection signal when there is an actual temperature change will be described using FIGS. 9 and 10. FIG.

  FIG. 9 is a diagram showing the temperature dependency of the relationship between the actuator drive current and the position detection signal. The horizontal axis is the DAC value of the current supplied to the actuator, and the vertical axis is the digital output of the Hall detection signal before calibration. As a result of measurement at 0 ° C., 30 ° C., and 60 ° C., characteristic differences are observed depending on the temperature. The actuator used for measurement is a bidirectional drive type, and in the region where the current DAC value is small, current flows in the opposite direction. In the region where the current DAC value is small, the movable part hits the Inf mechanical end, and in the region where the current DAC value is large, the movable part contacts the Macro mechanical end, so that no change is detected in the hole detection signal. In the middle region, the Hall detection signal also changes as the current DAC value changes, and the relationship is approximately linear.

  FIG. 10 is a diagram showing the relationship between the actuator drive current and the position detection signal after calibration of the position detection signal. Here, the values of hole detection signals at Inf mechanical end and Macro mechanical end at 30 ° C., 1028 and 3071 respectively, are predetermined Hall detection signal values, and the same at Inf mechanical end and Macro mechanical end even at 0 ° C. and 60 ° C. The Hall detection gain and offset were adjusted to show the values. By this calibration, the AD value of the hole detection signal which is not affected by the change in temperature can be obtained.

(Modification)
In the above description, although it demonstrated as calibration of AF, it is not necessarily limited to this and you may apply as a calibration method in OIS. In OIS, a method of displacing the lens in the XY direction perpendicular to the optical axis is common according to the shaking angle. The movable range in each of the X and Y directions is mechanically limited at both ends. As in the case of AF, position detection is not affected by temperature change by performing calibration that adjusts the gain and offset so that the hole detection signal at the mechanical end position at both ends of the movable range becomes a predetermined value. Is possible. In the case of OIS, if the entire movable range is set as the setting range of the target code, it is necessary to be careful because it may cause excessive swinging. That is, when camera shake exceeds a predetermined level, the servo system generates a large lens shift to correct it. However, the larger the shift amount, the lower the accuracy of camera shake correction around the pixel optically, and the pixel center You may feel discomfort as compared to residual blurring. In order to prevent such a phenomenon, it is desirable to minimize the movable range of the actuator.

When a control signal S _REF indicating the target position in the X and Y directions is externally supplied to the actuator driver IC 500 for OIS, the configuration can be substantially the same as that in FIG. Alternatively, angular velocity information in the pitching direction and the yawing direction may be received from the gyro sensor as the control signal S _REF . In this case, angular velocity information in the pitching direction is integrated and converted into angle information, and this is converted into position command in the Y axis direction used as a value P _{Ref_Y,} converted into angle information by integrating angular velocity information in the yawing direction, may be used it as a position command value P _{REF_X} the X-axis direction.

The invention disclosed herein can be grasped as follows.
1. One embodiment of the present invention relates to an imaging device. The imaging device includes an imaging lens, an actuator for positioning the imaging lens, a position detection element for detecting the position of the imaging lens, and an actuator driver for providing a drive signal to the actuator. The actuator has a first end and a second end for mechanically restricting both ends of the movable range of the movable portion including the imaging lens. The actuator driver has a calibration unit that adjusts the gain and offset of the position detection signal in the position detection element such that the position detection signal of the position detection element at the first end and the second end has a predetermined value. .

  According to the above configuration, since the position detection signals at both ends of the mechanical movable range where there is almost no change in position are calibrated so as to always have predetermined values, it is not influenced by environmental changes etc., and constant conditions The position detection signal can be used to enable high-precision and high-speed positioning of the imaging lens.

  Also, the imaging device according to an aspect may adjust the control current applied to the position detection element in order to adjust the gain of the position detection signal.

  Since the gain of the position detection signal can be adjusted by adjusting the control current, it becomes easy to calibrate so that the position detection signal at both ends of the mechanical movable range always has a predetermined value.

  In one aspect, the imaging device may convert the position detection signal into a digital signal based on a predetermined value of the position detection signal at the first end and the second end to generate a digital code of the position detection signal.

  According to the above configuration, it is possible to obtain a digital code of a constant position detection signal which is not influenced by a change in environment or the like.

  The imaging apparatus according to the present invention further includes a temperature detection unit that detects the temperature in the vicinity of the position detection element, and calibration performed by the calibration unit when a change from the temperature at the time of previous calibration execution becomes equal to or more than a predetermined value. Session may be run again.

  According to the above configuration, calibration of the position detection signal is performed again when a temperature change equal to or more than a predetermined value is detected, so that it is possible to obtain a position detection signal that is not easily influenced by the change in the environmental temperature.

  Further, in the imaging device according to the present invention, the temperature detection means may detect a temperature change by utilizing the fact that the internal resistance of the position detection element changes with temperature.

  According to the above configuration, the position detection element can be used for temperature detection, and a temperature change can be detected without using a special temperature sensor.

  In the imaging device according to the present invention, the position detection element may be a Hall element, and the temperature change may be detected by the change in the potential difference between both ends of the Hall element when a constant control current is applied.

  According to the above configuration, the Hall element can be used for temperature detection, and a temperature change can be detected without using a special temperature sensor.

  Further, the imaging device according to the present invention may control the position of the imaging lens based on the position detection signal as a result of the calibration performed by the calibration unit.

  According to the above configuration, since the position of the imaging lens is controlled based on the position detection signal which is not affected by environmental changes such as temperature, high precision and high-speed positioning of the imaging lens becomes possible.

  Another aspect of the invention relates to an actuator driver. The actuator driver is an actuator driver used for an imaging device, and the imaging device is driven by an imaging lens, an actuator for driving the imaging lens, a position detection element for detecting the position of the imaging lens, and the actuator An actuator driver for giving a signal, the actuator having a first end and a second end for mechanically restricting both ends of the movable range of the movable part including the imaging lens; It is characterized by having a calibration part which adjusts a gain and an offset of a position detection signal in a position detection element so that a position detection signal of a position detection element in an end and a 2nd end serves as a predetermined value.

  According to this aspect, the position detection signals at both ends of the mechanical movable range where there is almost no change in position are calibrated so that they always have predetermined values. A position detection signal can be used, and high-precision and high-speed positioning of the imaging lens is possible.

  The actuator driver according to the present invention may adjust the control current applied to the position detection element in order to adjust the gain of the position detection signal.

  Further, the actuator driver according to the present invention digitizes the position detection signal based on a predetermined value of the position detection signal at the first end and the second end and generates a digital code of the position detection signal. Good.

  The actuator driver according to the present invention further includes a temperature detection unit that detects the temperature in the vicinity of the position detection element, and calibration performed by the calibration unit when a change from the temperature at the time of previous calibration execution becomes equal to or more than a predetermined value. Session may be run again.

  In the actuator driver according to the present invention, the temperature detection means may detect a temperature change by utilizing the fact that the internal resistance of the position detection element changes with temperature.

  In the actuator driver according to the present invention, the position detection element may be a Hall element, and the temperature change may be detected by a change in the potential difference between both ends of the Hall element when a constant control current is applied.

  The actuator driver according to the present invention may control the position of the imaging lens based on the position detection signal as a result of the calibration performed by the calibration unit.

  Another aspect of the present invention relates to a calibration method. The calibration method is a position in an imaging apparatus including an imaging lens, an actuator for driving the imaging lens, a position detection element for detecting the position of the imaging lens, and an actuator driver for applying a drive signal to the actuator. A calibration method of detection, wherein an actuator has a first end and a second end for mechanically restricting both ends of a movable range of a movable part including an imaging lens, and the movable part of the actuator is The process of moving to the first end and obtaining the first position detection signal of the position detection element at that position, and moving the movable part of the actuator to the second end, the second position of the position detection element at that position A process of obtaining a detection signal, and the first position detection signal and the second position detection signal having predetermined values, A process of adjusting the gain and offset of the 置検 output signal, and further comprising a.

  According to this aspect, the position detection signals at both ends of the mechanical movable range where there is almost no change in position are calibrated so that they always have predetermined values. A position detection signal can be used, and high-precision and high-speed positioning of the imaging lens is possible.

  In the calibration method according to the present invention, a process of digitizing a position detection signal based on a predetermined value of the position detection signal at the first end and the second end and generating a digital code of the position detection signal May further be provided.

  Further, in the calibration method according to the present invention, the temperature in the vicinity of the position detection element is detected, and when the change from the temperature at the time of the previous calibration execution becomes equal to or more than a predetermined value, calibration by the calibration unit is performed again You may

  The imaging device, the actuator driver, and the calibration method as described above are used for a camera module for a mobile phone and the like. In particular, the present invention is preferably applied to an imaging device having a position detection function.

DESCRIPTION OF SYMBOLS 300 Imaging device 302 Imaging element 304 Lens 306 Processor 308 Holder 310 Coil 312, 314 Permanent magnet 316 Position detection element 400 Lens control device 402 Actuator 404 Position detection element 406 Temperature detection element 500 Actuator driver IC
501 interface circuit 502 front end circuit 503 drive unit 504 calibration unit 510 position detection unit 512 hall amplifier 514 A / D converter 516 DA converter 520 temperature detection unit 522 constant current circuit 524 A / D converter 530 calibration unit 532 processor 534 memory 540 interface circuit 550 filter 560 controller 562 error detector 564 PID controller 566 switch 570 driver section

Claims (20)

An imaging lens,
An actuator for positioning the imaging lens;
A position detection element that generates a position detection signal indicating the position of the imaging lens;
An actuator driver for supplying a drive signal to the actuator;
Equipped with
The actuator has a first end and a second end for mechanically restricting both ends of the movable range of the movable portion including the imaging lens.
The actuator driver performs calibration so that the position detection value based on the position detection signal at the first end becomes a first predetermined value and the position detection value becomes a second predetermined value at the second end. An imaging apparatus characterized in that it is configured to be executable.   The imaging device according to claim 1, wherein the actuator driver adjusts a control current or a control voltage supplied to the position detection element in the calibration.   The image pickup apparatus according to claim 1, wherein the actuator driver includes an amplifier that amplifies the position detection signal, and adjusts an offset of the amplifier in the calibration. The actuator driver further includes an A / D converter for converting the output of the amplifier into the digital position detection value,
The actuator driver performs calibration such that the position detection value becomes the first predetermined value at the first end and the position detection value becomes the second predetermined value at the second end. The imaging device according to claim 3, characterized in that The actuator driver further includes an A / D converter for converting the output of the amplifier into the digital position detection value,
In the actuator driver, at the first end, the input voltage of the A / D converter is a first voltage corresponding to the first predetermined value, and at the second end, the input voltage of the A / D converter is 4. The image pickup apparatus according to claim 3, wherein calibration is performed so as to be a second voltage corresponding to the second predetermined value.   The temperature detection means which detects the temperature of the vicinity of the said position detection element is provided, A calibration is re-executed when the detected temperature satisfy | fills a predetermined condition, It is characterized by the above-mentioned. Imaging device.   7. The image pickup apparatus according to claim 6, wherein calibration is re-executed on condition that a change from a temperature at the time of previous calibration execution is equal to or more than a predetermined value.   8. The image pickup apparatus according to claim 6, wherein the temperature detection unit detects a temperature change by utilizing a change in internal resistance of the position detection element depending on a temperature.   9. The image pickup apparatus according to claim 8, wherein the position detection element is a Hall element, and detects a temperature change based on a change in potential difference between both ends of the Hall element when a constant control current is applied.   The imaging device according to any one of claims 1 to 9, wherein the actuator driver generates the drive signal such that a position detection value based on the position detection signal approaches a target value. An actuator driver for driving an actuator for positioning an imaging lens, comprising:
The actuator has a first end and a second end for mechanically restricting both ends of the movable range of the movable portion including the imaging lens.
The actuator driver
A drive unit that generates a drive signal such that a position detection value based on a position detection signal indicating the position of the imaging lens from a position detection element approaches a target value;
A calibration unit that executes calibration so that the position detection value becomes a first predetermined value at the first end and becomes a second predetermined value at the second end;
An actuator driver comprising:   The actuator driver according to claim 11, wherein the calibration unit is capable of adjusting a control current or a control voltage supplied to the position detection element. It further comprises an amplifier for amplifying the position detection signal,
The actuator driver according to claim 11, wherein the calibration unit is capable of adjusting an offset of the amplifier. It further comprises an A / D converter for converting the output of the amplifier into the digital position detection value,
The calibration unit executes calibration so that the position detection value becomes the first predetermined value at the first end and the position detection value becomes the second predetermined value at the second end. The actuator driver according to claim 13, characterized in that: And A / D converter for converting the output of the amplifier into the digital position detection value,
The calibration unit is configured such that, at the first end, the input voltage of the A / D converter becomes a first voltage corresponding to the first predetermined value, and at the second end, the input voltage of the A / D converter The actuator driver according to claim 13, wherein calibration is performed such that the second voltage corresponding to the second predetermined value.   The calibration unit may include temperature detection means for detecting a temperature in the vicinity of the position detection element, and calibration may be re-executed when the detected temperature satisfies a predetermined condition. The actuator driver according to any one of the above.   The actuator driver according to claim 16, wherein the calibration unit re-executes the calibration under the condition that a change from the temperature at the time of the previous calibration execution is equal to or more than a predetermined value.   The actuator driver according to claim 16 or 17, wherein the temperature detection means detects a temperature change by utilizing a change in internal resistance of the position detection element due to a temperature.   19. The apparatus according to claim 18, wherein said position detection element is a Hall element, and said temperature detection means detects a temperature change based on a change in potential difference between both ends of the Hall element when given a constant control current. Actuator driver. Calibration method of imaging device comprising imaging lens, actuator for positioning imaging lens, position detection element for generating position detection signal indicating position of the imaging lens, and actuator driver for giving drive signal to the actuator And
Providing the actuator with a first end and a second end for mechanically restricting both ends of the movable range of the movable part including the imaging lens;
Moving the movable portion of the actuator to the first end and obtaining a first position detection value based on the position detection signal at that position;
Moving the movable portion of the actuator to the second end and obtaining a second position detection value at that position;
Performing calibration such that the first position detection value is a first predetermined value and the second position detection value is a second predetermined value;
A calibration method comprising:

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