JP2008178206A - Actuator drive device and camera device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator drive device that makes it possible to rapidly and stably operate step drive of an electromagnetic actuator by open-loop control and a camera device capable of performing a focus search in a short time using a voice coil motor (VCM) of the open-loop control. <P>SOLUTION: This actuator drive device drives the electromagnetic actuator whose movable portion is supported by an elastic member by the open-loop control. When the movable portion is displaced by a predetermined amount, a drive current I of the electromagnetic actuator is changed from a first current value to a second one by a prescribed gradient and the period of time during which the drive current is changed by the prescribed gradient is set to nT (where T is an inherent vibration period of the movable portion based on the elastic force of the elastic member and n is a natural number). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an actuator driving device that drives an electromagnetic actuator by open loop control, and a camera device that drives a camera lens by a VCM (voice coil motor).

  There has been a camera device that performs autofocus control by moving a camera lens with a VCM. Further, in a camera device mounted on a mobile phone, in order to reduce the size and cost, the driving method of the camera lens is usually an open loop control instead of a closed loop control. That is, the actuator is driven and controlled as if a predetermined amount of displacement was obtained when a predetermined drive current was output without performing control such as detecting the position of the movable part or applying a servo by feeding back the detection signal.

  The autofocus control in the camera device is usually executed as follows. As shown in the waveform diagram of FIG. 18, first, a drive current I that changes stepwise and in multiple stages is output to the VCM, and the camera lens is displaced in multiple stages in units of steps. In the VCM, the movable part is supported by a spring or the like, so that the magnitude of the output current I and the displacement amount X of the movable part have a substantially proportional relationship.

  In parallel with this step drive, the amount of focus shift is detected at each stage of the step, and the step in which the focus shift amount is the smallest among all the steps is found. Finally, the focus search is completed by changing the drive current I so that the position of the camera lens returns to the stage where the amount of focus deviation is minimized.

  As shown in the waveform diagram of FIG. 18B, when the VCM is step-driven by open loop control, the drive current I rises or falls depending on the action of the spring supporting the movable part and the inertia of the movable part. There was a problem that natural vibration occurred in the movable part at the timing.

  Therefore, when auto focus control is performed with the VCM of the opul loop control, the natural vibration is generated in the camera lens at each step, and it is necessary to wait until the vibration becomes small in order to detect the focus shift amount. For this reason, the problem that the time required for one focus search is increased correspondingly.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an actuator driving device that can quickly obtain a stable displacement operation without generating a natural vibration when an electromagnetic actuator is displaced by a predetermined amount by open loop control.

  Another object of the present invention is to provide a camera device that can perform a focus search in a short time in a camera device that performs autofocus driving using an open loop control VCM.

  In order to solve the above-mentioned problem, the invention according to claim 1 is an actuator driving apparatus for driving an electromagnetic actuator having a movable part supported by an elastic member by open loop control, and the movable part is displaced by a predetermined amount In addition, the drive current of the electromagnetic actuator is changed from the first current value with a constant gradient to the second current value, and a period during which the drive current is changed with the constant gradient is a period of the elastic member of the movable part. It is characterized by being set to approximately n times (n is a natural number) the natural vibration period based on the elastic force.

  Here, substantially n times the natural vibration period indicates a range including the following error. Simulation experiments and the like show that the smaller the error, the smaller the natural vibration that occurs after displacement, and the larger the error, the greater the natural vibration that occurs after displacement. However, the error is within ± 10% of the natural vibration period T. By doing so, the natural vibration after displacement can be greatly reduced. Further, it is more preferable that the error is within 5% of the natural vibration period T, so that the natural vibration after the displacement can be remarkably reduced, and more preferably, the error is within 3% of the natural vibration period T. The generation of natural vibration after displacement can be almost eliminated.

  The invention according to claim 2 further includes a controller for controlling the driving of the electromagnetic actuator, a driver circuit for outputting a driving current to the electromagnetic actuator, and adding a gradient to the rising or falling of the signal upon receiving a step signal. A signal processing circuit for outputting the processed signal, a step signal is output from the controller to the signal processing circuit, and the signal processing circuit adds a gradient to the signal and outputs the signal to the driver circuit, whereby the driver A drive current that changes with a constant gradient for a period corresponding to the natural vibration period is output from the circuit.

  According to a third aspect of the present invention, the signal processing circuit is configured to add a preset gradient to the rising or falling of the step signal, and the controller performs the step driving of the electromagnetic actuator. A step signal having a preset height, or a step signal having an integral multiple of the height, is output to the signal processing circuit, and the preset gradient and the preset A drive current that changes with a constant gradient for a period corresponding to the natural vibration period is output from the driver circuit in accordance with a step signal of height.

  According to a fourth aspect of the invention, there is provided the controller according to the first aspect, comprising: a controller that outputs a drive signal; and a driver circuit that receives the drive signal and outputs a drive current corresponding to the drive signal to the electromagnetic actuator. The controller outputs a drive signal with a gradient via a D / A converter, so that a drive current that changes with a constant gradient according to the natural vibration period is output from the driver circuit. Yes.

  The invention described in claim 5 is further characterized in that the electromagnetic actuator is a voice coil motor.

  According to a sixth aspect of the present invention, in the camera device, the actuator driving device according to the fifth aspect, a camera lens fixed to the movable part of the voice coil motor, and light incident through the camera lens are received. And an image pickup device.

  According to the first aspect of the present invention, after the drive current is changed with a constant gradient and the electromagnetic actuator is displaced by a predetermined amount, the vibration of the movable part based on the natural vibration is reduced, and the position of the movable part is quickly adjusted. It can be stabilized.

  According to the second aspect of the present invention, by adding a signal processing circuit separately, it is possible to generate a signal having a constant gradient as described above by digital signal processing of the controller.

  According to the third aspect of the present invention, it is possible to generate a signal having a constant gradient as described above without complicating the configuration of the signal processing circuit.

  According to the fourth aspect of the present invention, by providing a D / A converter with a high number of gradations, it is possible to generate a signal that changes with a constant gradient as described above only by digital signal processing of the controller.

  According to the fifth aspect of the present invention, the above-described effect can be obtained in an apparatus using a voice coil motor.

  According to the sixth aspect of the present invention, the time required for one focus search can be very shortened in the autofocus control of the camera device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a control system of a camera device according to a first embodiment of the present invention, and FIG. 2 shows a mechanical configuration of a lens driving portion in the camera device. FIG. (B) is a side sectional view.

  The camera device of this embodiment is mounted on a small electronic device such as a cellular phone, for example, and an image sensor 11 such as a CCD (Charge-Coupled Device) or CMOS sensor, and a camera lens that connects an image to the image sensor 11. 12, a VCM (Voice Coil Motor) 30 as an electromagnetic actuator that drives the camera lens 12 in the focus direction, a motor driver 21 that outputs a drive current to the VCM 30, and various pixel signals output from the image sensor 11. The image processing circuit 22 that performs signal processing of the above and converts it into image data, the controller 24 that performs focus control of the captured image and the control processing of the entire unit, and receives a step waveform signal and gives a predetermined gradient to its rise and fall A ramp wave generation circuit 40 is provided as a signal processing circuit that outputs a signal having a ramp waveform. Among these, the VCM 30, the motor driver 21, the ramp wave generation circuit 40 and the controller 24 constitute an actuator driving device.

  In the above configuration, the VCM 30, the image pickup device 11, the image processing circuit 22, and the like are integrated into a camera unit, and the controller 24, the ramp wave generation circuit 40, and the motor driver 21 are provided separately from the camera unit. May be. Further, the controller 22 may be configured in common with the controller of the electronic device on which the controller 22 is mounted.

  The controller 24 includes a CPU (Central Processing Controller) 25, a nonvolatile memory 26 in which control programs and control data are stored, a RAM (Random Access Memory) 27 that provides a working memory space to the CPU 25, an analog output For example, a D / A converter 28 is provided. The nonvolatile memory 26 stores, as control data, for example, signal waveform data output from the D / A converter 28 when performing a focus search.

  As shown in FIG. 2, the VCM 30 includes an outer peripheral frame 31 fixed to a frame of the apparatus, a cylindrical movable part 32 that is disposed inside the outer peripheral frame 31 and is movable up and down, and a movable part 32. It consists of a leaf spring 33 or the like as an elastic member that is supported so as to be vertically movable. A cylindrical magnet M is fixed on the inner peripheral side of the outer peripheral frame 31, and a coil C is provided on the outer peripheral portion of the movable portion 32 so as to oppose the magnet M. Then, by passing an electric current through the coil C, the movable part 32 is displaced in the vertical direction by the interaction with the magnet M.

  Note that the VCM 30 is not limited to the configuration shown in FIG. For example, it may be a moving magnet type in which a magnet is provided on the movable part side, or a configuration in which a yoke is provided at a location facing the magnet with the electromagnetic coil sandwiched so that the magnetic field of the magnet is mixed with the electromagnetic coil. good.

  The VCM 30 is driven by open loop control. The controller 24 outputs a predetermined analog signal via the D / A converter 28 and the ramp wave generation circuit 40, and the motor driver 21 generates a drive current proportional to the analog signal. The movable part 32 is displaced by outputting to the VCM 30. Detection of the position of the movable portion 32, feedback control of the detection signal, and the like are not performed, thereby eliminating the need for a sensor, an arithmetic circuit for generating a feedback signal, and the like, and realizing a reduction in size and cost of the lens driving portion.

  The VCM 30 has a structure in which the movable portion 32 stops at a position where the electromagnetic force generated in the coil C and the repulsive force of the leaf spring 33 are balanced. Further, since the electromagnetic force is proportional to the energization amount of the coil C, the displacement amount of the movable portion 32 has a relationship proportional to the energization amount of the coil C. Since the output of the motor driver 21 is configured so that the voltage and the current are substantially proportional, the output current can be replaced with the output voltage in the above description.

  Further, the VCM 30 has a property that when the movable part 32 is suddenly displaced, vibration is generated in the movable part 32 due to the elastic force of the leaf spring 33 and the inertia of the movable part 32. This vibration has a natural vibration period determined by the spring coefficient of the leaf spring 33 and the weight of the movable portion 32 including the camera lens 12.

  FIG. 3 shows a circuit configuration diagram of the ramp wave generation circuit 40 of FIG.

  When a stepped voltage signal is input, the ramp wave generation circuit 40 outputs a signal with a predetermined gradient a added to the rising and falling edges of the signal. The ramp wave generation circuit 40 includes a comparator 41, a constant current circuit 42 that can output a constant current I1 in the forward direction and the reverse direction, a capacitor C1 that inputs and outputs the constant current I1, and generates a voltage. It comprises a voltage follower (voltage buffer) 43 that receives the voltage of C1 and outputs this voltage.

  The comparator 41 is connected such that the voltage Vin output from the D / A converter 28 is input to the non-inverting input terminal and the output voltage Vout is input to the inverting input terminal. The constant current circuit 42 is configured to output a current I1 in the forward direction when a high level signal is input, and to output a current I1 in the reverse direction when a low level signal is input.

  With such a configuration, for example, when the input voltage Vin is stable at a constant value, the input voltage Vin and the output voltage Vout have the same value due to the negative feedback of the output voltage Vout. On the other hand, when a step signal that causes the input voltage Vin to rise from the first voltage to the second voltage is input, the output of the comparator 41 becomes high level from the rising timing of this signal, and the constant current circuit 42 outputs a constant current. I1 is output. Then, the voltage of the capacitor C increases in proportion to time. Further, when this voltage reaches the second voltage, the output of the constant current I1 is stopped and the voltage of the capacitor C is stabilized. Therefore, the output voltage Vout has a ramp waveform that rises from the first voltage to the second voltage with a constant gradient “I1 / C1 (capacitance value of the capacitor C1)”.

  On the other hand, when a step signal that causes the input voltage Vin to drop from the second voltage to the first voltage is input, the reverse operation is performed, and the output voltage Vout is constant from the second voltage to the first voltage. The ramp waveform falls at −I1 / C1 ″.

  FIG. 4 is a waveform diagram illustrating a first method for performing step driving of the VCM 30 without generating natural vibration.

  In the actuator driving apparatus according to the present invention, when step driving of the VCM 30 is performed, a driving current having a ramp waveform that changes with a constant inclination is output to the VCM 30, and as shown in FIG. Control is performed so as to be displaced with a constant slope in proportion to the driving current of the ramp waveform. Further, control is performed such that the period t0 during which the displacement is performed with the constant inclination is approximately n times (n is a natural number) the natural vibration period T of the movable portion 32.

  Furthermore, in this embodiment, in order to realize such drive current output control, the ramp waveform gradient amount a generated by the ramp wave generation circuit 40 and the step drive unit of the VCM 30 controlled by the controller 24 are provided. A method is adopted in which the displacement amount y0 is fixed in advance. That is, the gradient amount a is fixed to a predetermined value by appropriately setting the current value I1 and the capacitance value C1 of the ramp wave generation circuit 40. Further, the height of the step signal output from the controller 24 at the time of step driving of the VCM 30 is limited to a value corresponding to the unit displacement y0 or an integer multiple thereof. With such a setting, when the step signal is output from the controller 24, the period in which the signal output from the ramp wave generation circuit 40 changes with a constant gradient is always approximately n times the natural vibration period T. .

  FIG. 5 is a waveform diagram showing the actual movement of the VCM obtained by the drive current output under the above conditions. 5A shows the waveform of the drive current I, FIG. 5B shows the waveform of the displacement amount X of the movable part 32, and FIG. 5C shows the waveform of the speed v of the movable part 32.

  As shown in FIG. 5A, when the drive current I having a ramp waveform is output with the length of the natural vibration period T, an electromagnetic force proportional to the drive current I acts on the movable portion 32 of the VCM 30. As shown in (c), the speed v of the movable portion 32 increases from the ramp waveform starting end T1, reaches the maximum speed in the half period “T / 2”, and then decreases the speed again. The speed becomes almost zero at the end T2 of the ramp waveform (at the time point of the cycle “1 × T”).

  Therefore, as shown in FIG. 5 (b), the movable part 32 of the VCM 30 starts to be displaced from the start end T1 of the ramp waveform, becomes zero at the end T2 of the ramp waveform, stabilizes the displacement, and then increases. Vibration does not occur.

  Note that, in the motion of simple vibration, the potential energy of the moving body is maximized at a phase where the speed of the moving body is zero. Therefore, even in the movement of the VCM 30 shown in FIG. At the time T2 at the end of the ramp waveform, elastic energy is accumulated in the leaf spring 33, and after that, the elastic energy may cause an illusion that a large natural vibration is generated in the movable part 32. The reason is as follows. Thus, it can be explained that the position of the movable portion 32 is stabilized immediately after the movable portion 32 becomes zero speed.

  FIG. 6 is a graph showing the frequency response characteristics of the VCM 30, and FIG. 7 is an electromagnetic force applied to the movable portion 32 when the drive current I is vibrated with a ramp waveform having the same length as the natural vibration period T. A waveform diagram representing F is shown.

  The VCM 30 has a frequency response characteristic as shown in FIG. 6 because a resistance force is applied to the movable portion 32 by, for example, the stickiness of the leaf spring 33 or the electromagnetic induction of the coil C. That is, a substantially constant gain is obtained for the low frequency input signal, the gain increases around the natural frequency f0, and the gain decreases as the frequency increases for a high frequency input signal. That is, for a low frequency signal, the gain of the VCM 30 is almost determined by the balance between the electromagnetic force F of the coil C and the elastic force of the leaf spring 33, whereas for a high frequency signal, the electromagnetic of the coil C is determined. In addition to the balance between the force F and the elastic force of the leaf spring 33, this shows that the action of the inertial force of the movable portion 32 has a great influence. Therefore, when a drive signal having a frequency component lower than the natural frequency f0 is used to drive the VCM 30, the action of the inertial force of the movable portion 32 is not so much affected, and the electromagnetic force F of the coil C and the leaf spring 33 are not affected. The influence of elastic force becomes dominant.

  In addition, in the ramp waveform having the same length as the natural vibration period T, as shown in FIG. 7A, even when it is vibrated at the highest frequency, it becomes a triangular wave with a period of “2T”, and the electromagnetic force F of the VCM 30 obtained thereby. Is also a triangular wave with a period of “2T”. Although such a triangular wave includes a relatively high frequency component at the start and end of its rise and fall, in many ranges, as shown by the dotted line in FIG. 7B, the half of the natural frequency f0 is “f0 / It is occupied by a signal having a frequency component of about 2 ″.

  Therefore, at the end T2 of the ramp waveform in FIG. 5, the speed of the movable part 32 becomes zero, but the influence of the inertial force of the movable part 32 is small, and the plate spring 33 has little potential energy accumulated. Thereafter, the position of the movable portion 32 becomes stable.

  8 to 11 show waveform diagrams of simulation results when the ramp waveform slope and period of the drive current are changed.

  FIG. 8 shows the slope of the ramp waveform in the same manner as in FIG. FIG. 9 shows that the ramp waveform slope is 1.5 times that of FIG. 5 and the period is the same as that of FIG. 5, so that a displacement amount 1.5 times that of FIG. 5 can be obtained. FIG. 10 shows that the ramp waveform slope is twice that of FIG. 5 and the period is the natural vibration period T, so that a displacement amount twice that of FIG. 5 can be obtained. FIG. 11 shows a case where the slope of the ramp waveform is the same as that in FIG. 5 and the period is 1.5 times the natural vibration period T.

  As shown in FIGS. 5 to 10, by setting the period of the ramp waveform to n times the natural vibration period T (n is a natural number), the speed of the movable portion 32 becomes zero at the end of the ramp waveform, so It can be seen that a stable displacement of the portion 32 is obtained. As shown in FIG. 11, when the period of the ramp waveform deviates from n times the natural vibration period T, the speed remains in the movable portion 32 at the end of the ramp waveform, and then the natural vibration is generated in the movable portion 32. You can see it happen.

  Next, an example of autofocus control executed by the camera device having the above configuration will be described.

  12 is a flowchart of the focus search process executed by the CPU 25 of the controller 24, and FIG. 13 is a time chart showing the D / A output of the controller 24 and the output of the ramp wave generation circuit 40 output in this focus search process. It is a chart.

  This focus search process is a process that is started by sending a signal to the controller 24 when a focus search operation such as a light press of the shutter button of the camera is performed. When this process is started, first, in step S1, the output of the D / A converter 28 is set to an initial value (control voltage V0), and in a subsequent step S2, a predetermined time is waited in order to stabilize the drive. Thereafter, in step S3, the focus state is confirmed based on the signal from the image processing circuit 22, and this confirmation value is registered in the memory 27.

  Next, the output of the D / A converter 28 is changed step by step by the branch processing of step S4 and the loop processing of steps S5, S2, and S3, and the confirmation value of the focus state at each step is registered in the memory 27. To go. Then, this loop process is performed for all steps.

  Here, as shown by the solid line in FIG. 13, the output of the D / A converter 28 is an output that changes stepwise from voltage V1 to V7. The potential difference between these steps is set to a potential difference corresponding to the unit displacement amount y0 fixedly set in advance shown in FIG. Therefore, the signal output from the ramp wave generation circuit 40 based on this step signal changes at a constant gradient as shown by the dotted line in FIG. 13, and the period t0 of this change is a natural number times the natural vibration period T of the VCM 30. It becomes the value of.

  By such signal processing, the natural vibration generated in the movable portion 32 after the movable portion 32 of the VCM 30 is displaced to each step is suppressed, and the drive stabilization waiting time in step S2 can be set short. Thereby, the total processing time for confirming the focus state over all steps can be greatly shortened.

  When the focus state has been confirmed in all the steps as described above, in the subsequent step S6, the confirmation value of the focus state in all the steps registered in the memory 27 is compared to determine the step position where the focus is best. In step S7, the output of the D / A converter 28 is switched to the control voltage (V2 in FIG. 13) corresponding to the best step position.

  Here, since the control voltages V1 to V7 at each step are all voltages corresponding to the unit displacement y0 shown in FIG. 4, the difference between the control voltages (steps S7) that change over a plurality of steps ( V7−V2) is also a voltage corresponding to an integral multiple of this unit displacement y0. Accordingly, the period during which the signal output from the ramp wave generation circuit 40 in this step S7 (shown by a dotted line in FIG. 13) also changes at a constant gradient is a natural number multiple “5 × t0” of the natural vibration period T of the VCM 30. Thus, the natural vibration is not generated in the movable part 32 even by the displacement across the plurality of steps.

  Subsequently, in order for the drive of the VCM 30 to be stabilized, the system waits for a short time (step S8), and finally confirms whether or not the subject has moved (step S9). If the focus state is good by the branch process based on the result (step S10), this process is terminated. If the focus state is not good, the process returns to step S1 and the process from there is executed.

  In this way, by using the output of the ramp waveform corresponding to the natural vibration period T for the step drive of the VCM 30, vibration after each step drive is suppressed, so that the drive stabilization waiting time can be set short. It is possible to significantly shorten the overall processing time required for the search.

  Note that the step driving method of the VCM 30 in the focus search process can be variously modified.

  FIG. 14 shows a control voltage time chart showing another example of the focus search process.

  For example, as shown in FIG. 14, the VCM 30 may not be step driven step by step during focus search, but step driving may be performed by skipping one step, and various other step driving methods may be applied. You can also That is, if the output unit of the D / A converter 28 is set to the voltages V0 to V7, the period during which the output signal of the ramp wave generation circuit 40 changes at a constant gradient is VCM30 regardless of any step drive during this period. Thus, natural vibration period T is multiplied by a natural number, and it is possible to suppress generation of natural vibration in movable portion 32 after step driving.

  As described above, according to the camera device and the actuator driving device of this embodiment, even when the camera lens 12 is step-driven by the opul loop control, a driving current having a ramp waveform corresponding to the natural vibration period T is output to the VCM 30. Thus, it is possible to prevent the natural vibration of the camera lens 12 from being generated after the step drive, and to quickly converge the camera lens 12 to a predetermined position. Thereby, the effect that the time required for the focus search can be greatly shortened can be obtained.

  Since the ramp waveform is generated from the step waveform by the ramp wave generation circuit 40, a desired ramp waveform can be output without increasing the gradation number of the D / A converter 28 or increasing the operating frequency of the controller 24. The effect that can be done.

[Second Embodiment]
FIG. 15 is a block diagram showing the configuration of the control system of the camera apparatus of the second embodiment according to the present invention.

  The camera apparatus according to the second embodiment does not include the ramp wave generation circuit 40 according to the first embodiment, and is configured to pseudo-output a ramp waveform signal that changes at a constant gradient by the D / A converter 28B. .

  Therefore, in this embodiment, a D / A converter 28B having a relatively large output gradation number is employed, and the operating frequency of the controller 24 is also set to a relatively high value.

  A pseudo ramp waveform signal output from the D / A converter 28B when the VCM 30 is step-driven is generated based on, for example, waveform data stored in the flash memory 26. Similarly to the case of the first embodiment, this waveform data is also generated so that the period changing at a constant gradient is a natural number times the natural vibration period T of the VCM 30.

  FIG. 16 shows a flowchart of the focus search process executed by the CPU 25 of the controller 24, and FIG. 17 shows a time chart showing the output of the D / A converter 28B output in this focus search process.

  This focus search process is substantially the same as the process of FIG. 12 described in the first embodiment, and is mainly different in that steps S11 and S12 for outputting a ramp waveform are added. Steps that are the same as those in FIG.

  In steps S11 and S12 for outputting the ramp waveform, for example, the waveform data of the ramp waveform is read from the memory table of the flash memory 26, and the control signal is switched according to the value of the memory table. Thereby, a pseudo ramp waveform is output from the D / A converter 28B.

  Then, as shown in FIG. 17, by the output processing of the D / A converter 28B, control including a ramp waveform having a period length that is a natural number multiple of the natural vibration period T of the VCM 30 is performed as in the first embodiment. A signal is output, and a drive current proportional to the signal is output to the VCM 30. Thereby, the movable part 32 of the VCM 30 is displaced in each step, and the occurrence of natural vibration in the movable part 32 after each step drive is suppressed.

  The ramp waveform signal output from the D / A converter 28B is a pseudo signal as shown in the enlarged view of FIG. 17, but the output rate of the D / A converter 28B is increased and the minimum unit of output gradation is selected. By setting it small and outputting in multiple stages, the same operation as the ramp wave of the first embodiment can be obtained.

  In this embodiment, since the ramp waveform is generated by the D / A converter 28B, the ramp waveform gradient a can be changed with a relatively high degree of freedom by changing the waveform data in the memory table. . Therefore, for example, it is possible to change the slope a of the ramp waveform in accordance with the amount of displacement. Even in this case, the period in which the signal changes with a constant slope is a natural number times the natural vibration period T of the VCM 30. I can do it.

  As described above, according to the camera device and the actuator driving device of this embodiment, even when the camera lens 12 is step-driven by the opul loop control, a driving current having a ramp waveform corresponding to the natural vibration period T is output to the VCM 30. Thus, it is possible to prevent the natural vibration of the camera lens 12 from being generated after the step drive, and to quickly converge the camera lens 12 to a predetermined position. Thereby, the effect that the time required for the focus search can be greatly shortened can be obtained.

  In addition, since the ramp waveform signal is generated by the output of the D / A converter 28B, it is possible to output a signal having a different slope a in each step drive when performing a plurality of step drives. Accordingly, unlike the first embodiment, the displacement amount of the step drive is not fixed to an integral multiple of the unit displacement amount y0, and it is possible to correspond to a fine displacement amount.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the above-described embodiment, an example in which the actuator driving device is applied to the driving mechanism of the camera lens 12 has been shown. It is.

  Further, although the VCM has been exemplified as the electromagnetic actuator, for example, an electromagnetic actuator in which a planar coil is fixed to a movable portion supported by a spring and a magnet is disposed opposite to the coil is used for various types of electromagnetic actuators. The present invention can be similarly applied.

  The autofocus control method shown in the above embodiment is merely an example, and the present invention can be effectively applied to various autofocus controls that perform focus search while stepping the camera lens. In addition, details specifically shown in this embodiment, such as the configuration of the ramp wave generation circuit and the VCM, can be appropriately changed without departing from the spirit of the invention.

It is a block diagram which shows the structure of the control system of the camera apparatus of 1st Embodiment. The mechanical structure of the lens drive part of a camera apparatus is shown, (a) is the top view, (b) is a sectional side view. It is a circuit block diagram of the ramp wave generation circuit of FIG. It is a wave form diagram explaining the 1st system which performs the step drive of VCM, without generating a natural vibration. It is a wave form diagram showing the actual motion of VCM obtained by the drive current of a ramp wave shape. It is the graph which showed the frequency response characteristic of VCM. FIG. 6 is a waveform diagram of current I and electromagnetic force F when a drive current is vibrated with a ramp waveform under a predetermined condition. It is a wave form diagram which shows an example of the simulation result at the time of changing the inclination and period of the ramp waveform of a drive current. It is a wave form diagram which shows an example of the simulation result at the time of changing the inclination and period of the ramp waveform of a drive current. It is a wave form diagram which shows an example of the simulation result at the time of changing the inclination and period of the ramp waveform of a drive current. It is a wave form diagram which shows the simulation result at the time of shifting the period of the ramp waveform of a drive current from the natural number multiple of the natural vibration period T. It is a flowchart of the focus search process performed by CPU of a controller. It is the time chart which showed the D / A output of the controller and the output of the ramp wave generation circuit which are output with focus search processing. It is a time chart which shows the other example of a focus search process. It is a block diagram which shows the structure of the control system of the camera apparatus of 2nd Embodiment. It is a flowchart of the focus search process in 2nd Embodiment. FIG. 17 is a time chart showing the output of the D / A converter output in the focus search process of FIG. 16. It is a wave form diagram explaining operation | movement of the conventional focus search.

Explanation of symbols

11 Image sensor 12 Camera lens 21 Motor driver (driver circuit)
24 controller 25 CPU
26 Nonvolatile memory 30 VCM (electromagnetic actuator)
32 Movable part 33 Leaf spring (elastic member)
40 Ramp Wave Generation Circuit 41 Comparator 42 Constant Current Circuit 43 Voltage Follower C1 Capacitor

Claims (6)

An actuator driving device for driving an electromagnetic actuator having a movable part supported by an elastic member by open loop control,
When the movable part is displaced by a predetermined amount, the driving current of the electromagnetic actuator is changed from the first current value with a constant gradient to the second current value,
The actuator driving device characterized in that the period during which the drive current is changed at the constant gradient is set to approximately n times (n is a natural number) of the natural vibration period based on the elastic force of the elastic member of the movable portion. . A controller for controlling the driving of the electromagnetic actuator;
A driver circuit for outputting a drive current to the electromagnetic actuator;
A signal processing circuit that receives a step signal and outputs a signal with a gradient added to the rising or falling edge of the step signal;
With
A step signal is output from the controller to the signal processing circuit, and the signal processing circuit adds a gradient to the signal and outputs the signal to the driver circuit, so that the driver circuit can output a constant period according to the natural vibration period. 2. The actuator driving device according to claim 1, wherein a driving current that changes with a gradient is output. The signal processing circuit is configured to add a preset gradient to the rising or falling edge of the step signal;
The controller is configured to output a step signal having a preset height or a step signal having an integral multiple of the height to the signal processing circuit when the electromagnetic actuator is step-driven. ,
The drive circuit outputs a drive current that changes at a constant slope for a period corresponding to the natural vibration period according to the step signal having the preset slope and the preset height. 3. The actuator driving device according to 2. A controller that outputs a drive signal;
A driver circuit that receives the drive signal and outputs a drive current corresponding to the drive signal to the electromagnetic actuator;
When the controller outputs a drive signal with a gradient added via a D / A converter, a drive current that changes with a constant gradient for a period corresponding to the natural vibration period is output from the driver circuit. The actuator driving device according to claim 1.   The actuator driving device according to claim 1, wherein the electromagnetic actuator is a voice coil motor. An actuator driving device according to claim 5;
A camera lens fixed to the movable part of the voice coil motor;
An image pickup device that receives light incident through the camera lens.

Images