JP2006251100A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus having a function to correct a focal position. <P>SOLUTION: The imaging apparatus (20) is equipped with: a lens (1); a lens frame (2); a fixed barrel (3); a supporting member (4) supporting the lens and the lens frame movably in an optical axis direction with reference to the fixed barrel; a bimorph type piezoelectric element (6) moving the lens unit in the optical axis direction; a controller (14) controlling the bimorph type piezoelectric element; an acceleration sensor (5) capable of detecting the acceleration of the lens unit in the optical axis direction; an acceleration change detection means (10) detecting the change of the acceleration based on an output signal from the acceleration sensor; a reverse phase signal generation means (11) inverting the output signal from the acceleration change detection means to a reverse phase; and a displacement amount calculation means (12) obtaining the displacement amount of the lens based on the output signal from the reverse phase signal generation means. The controller controls the bimorph type piezoelectric element in accordance with an output signal from the displacement amount calculation means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging apparatus that prevents fluctuations in focus position and improves seismic resistance even when a bimorph piezoelectric element is used.

  In recent years, various imaging apparatuses using a bimorph piezoelectric element as a driving source for an autofocus lens have been proposed. Patent Document 1 discloses such an imaging apparatus. FIG. 4 is a perspective view illustrating a configuration of a conventional imaging device 50. As shown in FIG. 4, the imaging device 50 includes a lens 51, a holding unit 52 that holds the lens, a fixing unit 53, one end fixed to the holding unit 52, and the other end fixed to the fixing unit 53. A voltage is applied to the member 54, the L-shaped member 55 protruding from the fixed portion 53 and having a relatively low rigidity and being easily bent, the bimorph piezoelectric element 56 installed so as to sandwich the L-shaped member 55, and the bimorph piezoelectric element 56 Has a power supply unit 57 for applying. In the imaging device 50, when a voltage is applied to the bimorph piezoelectric element 56 by the power supply unit 57, the bimorph piezoelectric element 56 is bent and displaced in a substantially C shape. Accordingly, the L-shaped member 55 sandwiched between the bimorph piezoelectric elements 56 is also bent. Therefore, the holding part 52 holding the lens 51 can be moved in the optical axis direction.

  Here, in order to obtain a certain amount of lens movement using the bimorph type piezoelectric element, it is necessary to increase the applied voltage or lengthen the entire length (span) of the bimorph type piezoelectric element. However, the applied voltage cannot be increased excessively due to the power consumption of the imaging apparatus. Therefore, it has been proposed to increase the overall length of the bimorph piezoelectric element. This is because by increasing the total length of the bimorph piezoelectric element, the amount of displacement of the bimorph piezoelectric element increases.

JP-A-5-210861

  However, if the total length of the bimorph piezoelectric element is increased, the amount of elastic deformation of the bimorph piezoelectric element itself increases depending on the weight of the autofocus lens supported by the bimorph piezoelectric element. Moreover, in recent years, with the increase in the number of pixels of a charge coupled device (CCD), the number of lenses provided in the imaging device is increasing. For this reason, the weight of the autofocus lens tends to increase. Therefore, when an impact is applied to the imaging device, the lens vibrates and the focus fluctuates, and further, the bimorph piezoelectric element cannot withstand the weight of the lens, and the bimorph piezoelectric element is greatly bent and damaged. there were.

  Accordingly, an object of the present invention is to provide an imaging apparatus that prevents fluctuations in the focus position and has improved earthquake resistance even when a bimorph piezoelectric element is used.

  The present invention provides a lens unit including a lens capable of forming a subject image at a predetermined position, a fixing member provided with the lens unit, and the lens unit movable in the optical axis direction with respect to the fixing member. A supporting member to support, a piezoelectric element that moves the lens unit in the optical axis direction, a controller unit that controls the piezoelectric element, an acceleration sensor that can detect acceleration in the optical axis direction of the lens unit, and Acceleration change detecting means for outputting a change in acceleration based on an output signal of the acceleration sensor, an antiphase signal generating means for inverting the output signal of the acceleration change detecting means to an antiphase, and an output of the antiphase signal generating means Displacement amount calculating means for obtaining a displacement amount of the lens unit in the optical axis direction based on a signal, and the controller unit calculates the displacement amount In accordance with the output signal of the stage, which is an imaging apparatus characterized by controlling the piezoelectric element.

  With this configuration, even when vibration is applied to the lens unit, the focus position of the lens unit can be kept constant without fluctuation. In addition, the piezoelectric element can be protected against an external impact.

  The acceleration sensor can be provided in the lens unit. With this configuration, the degree of freedom in design can be increased. Further, the acceleration in the optical axis direction of the lens unit can be accurately detected.

  The piezoelectric element may be a bimorph type piezoelectric element. With this configuration, even when a bimorph piezoelectric element is used, it is possible to prevent fluctuations in the focus position due to vibration. Further, it is possible to prevent the bimorph piezoelectric element from being damaged by an external impact.

  The support member may be a parallel link mechanism. With this configuration, the imaging element surface and the lens surface of the lens unit can always be kept parallel.

  The support member may be a guide shaft and a guide sleeve. Even with this configuration, the imaging element surface and the lens surface of the lens unit can always be kept parallel.

Hereinafter, an embodiment of an imaging device according to the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of the imaging apparatus 20 and a control method of the imaging apparatus 20 in the present embodiment. FIG. 2 is a front view of the imaging apparatus 20. As shown in FIG. 1, the imaging apparatus 20 in the present embodiment includes a lens 1, a lens frame 2, a fixed cylinder 3, a lens frame support 4, an acceleration sensor 5, a bimorph piezoelectric element 6, an imaging element 7, and an acceleration sensor driver. 8, an amplifier 9, an acceleration change detection unit 10, an antiphase signal generation unit 11, a displacement amount calculation unit 12, a lens movement instruction unit 13, a controller 14, and a piezoelectric element driver 15.

  The lens 1 is composed of one or a plurality of lenses. The lens frame 2 is configured to support the lens 1. The fixed cylinder 3 is provided with at least a lens support 4, a bimorph type piezoelectric element 6, and an image sensor 7. The lens frame support portion 4 is composed of a pair of levers 4A and 4B having the same length, and is arranged so as to be equally spaced from each other. One end can be rotated by the lens frame 2 and the other end can be rotated by the fixed cylinder 3. To form a parallel link mechanism. The bimorph type piezoelectric element 6 has a structure in which two piezoelectric elements polarized in the thickness direction are bonded together. One end in the longitudinal direction is fixed to the fixed cylinder 3, and the other end is engaged with the locking portions 2A and 2B of the lens frame 2. Here, when a voltage is applied to the bimorph type piezoelectric element 6, the free end is bent and deformed substantially in the optical axis direction. Therefore, the lens 1 can be moved in the optical axis direction by applying a voltage to the bimorph piezoelectric element 6. Note that the bimorph piezoelectric element 6 is set to an infinite focus position when no current is applied. The image sensor 7 converts the light of the subject image formed by the lens 1 into an electrical signal. The acceleration sensor 5 is fixed to the lens frame 2 and detects the acceleration of the lens frame 2 in the optical axis direction.

  The acceleration sensor driver 8 supplies power to the acceleration sensor 5. The amplifier 9 amplifies the output signal from the acceleration sensor 5. The acceleration change detection means 10 receives a signal from the acceleration sensor 5 and outputs a signal indicating acceleration per unit time. The reverse phase signal generation means 11 inverts the signal from the acceleration change detection means 10 and outputs it. The displacement amount calculation means 12 calculates the movement amount and movement direction of the lens frame 2 in the optical axis direction according to the signal from the antiphase signal generation means 11 and outputs the result to the controller 14. The lens movement instruction means 13 instructs the lens 1 to move by a predetermined amount in the optical axis direction according to the photographer's intention during autofocus shooting or manual shooting. The controller 14 calculates the optimum lens movement amount in the optical axis direction in response to inputs from the lens movement instruction means 13 and the displacement amount calculation means 12 and instructs the movement of the lens 1. The piezoelectric element driver 15 applies a voltage to the bimorph type piezoelectric element 6 in accordance with an output signal from the controller 14. With such a configuration, the photographer moves the lens 1 in the optical axis direction to adjust the focus.

  Next, the operation of this embodiment will be described. In order to simplify the description, it is assumed that there is no friction between the lens frame support member 4, the lens frame 2, and the fixed cylinder 3.

  At the time of normal photographing, as shown in FIG. 1, the lens movement instruction means 13 instructs the controller 14 to move the bimorph type piezoelectric element 6 by a predetermined displacement amount in accordance with autofocus photographing or manual photographing. The controller 14 outputs a signal indicating a voltage value necessary for moving the bimorph piezoelectric element 6 by a predetermined movement amount to the piezoelectric element driver 15. The piezoelectric element driver 15 applies a voltage corresponding to the signal from the controller 14 to the bimorph piezoelectric element 6. As a result, the lens frame 2 moves by the amount instructed by the lens movement instruction means 13.

  Next, a signal flow when vibration is applied to the imaging apparatus 20 from the outside will be described with reference to FIG. When vibration is applied from the outside, the lens frame 2 vibrates at an acceleration Ax (t) that changes with time in the X-axis direction (optical axis direction). The acceleration sensor 5 fixed to the lens frame 2 outputs a current value 22 corresponding to the acceleration Ax (t) accompanying the vibration of the lens frame 2. Since the output from the acceleration sensor 5 is weak, the amplifier 9 amplifies the input current value 22 and outputs it as an amplified current value 23. The acceleration change detection means 10 quantizes the amplified current value 23 from the amplifier 9 per unit time and outputs it as a quantized signal 24. The antiphase signal generation unit 11 inverts the quantized signal 24 quantized by the acceleration change detection unit 10 and outputs the inverted signal as an antiphase quantized signal 25. The displacement amount calculating means 12 obtains the acceleration Ax (t) from the quantized signal of the acceleration change detecting means 10, the known mass m of the lens 1 and the lens frame 2, the spring constant k of the bimorph type piezoelectric element 6, ( The displacement amount δ of the lens frame is calculated from the balance formula between the force due to acceleration and the spring force shown in 1) and (2). Then, the displacement amount calculation means 12 outputs the displacement amount 26 toward the controller 14.

  The controller 14 outputs to the piezoelectric element driver 15 a voltage instruction signal 27 indicating a voltage value necessary for moving the displacement amount 26 instructed from the displacement amount calculation means 12. The piezoelectric element driver 15 applies the voltage value 28 instructed by the controller 14 to the bimorph piezoelectric element 6. As a result, the bimorph piezoelectric element 6 moves so as to cancel the displacement of the lens frame 2 due to external vibration.

  In this way, the bimorph piezoelectric element 6 moves so as to cancel the displacement of the lens frame 2 due to external vibrations, so that the focus position can be maintained. Therefore, even when a bimorph piezoelectric element is used for driving the lens, the focus position can be kept constant without fluctuation even when vibration is applied to the lens unit. Even if an excessive acceleration such as an impact is applied, it is possible to prevent damage due to the large deformation of the bimorph piezoelectric element. The lens frame support 4 is not limited to the parallel link mechanism as shown in FIG. 1, but a guide shaft-guide in which a guide shaft fixed to the fixed cylinder 3 and a guide sleeve provided on the lens frame 2 slide. A sleeve mechanism may be used. Further, although the acceleration sensor 5 is provided in the lens frame 2, it may be provided in the fixed cylinder 3.

  Note that the present invention is not limited to the above-described embodiments, and those skilled in the art can implement the present invention in various modes within the scope of the gist of the invention described in the claims.

It is the figure which showed the simple structure of the imaging device which concerns on a present Example. 1 is a front view of an imaging apparatus according to an embodiment. It is the figure which showed simply the flow of the signal when a vibration is added to the imaging device which concerns on a present Example. It is a perspective view which shows the structure of the conventional imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens 2 Lens frame 2A, 2B Locking part 3 Fixed cylinder 4 Lens frame support part 4A, 4B Lever 5 Acceleration sensor 6 Bimorph type piezoelectric element 7 Imaging element 8 Acceleration sensor driver 9 Amplifier 10 Acceleration change detection means 11 Reverse phase signal detection Means 12 Displacement calculation means 13 Lens movement support means 14 Controller 15 Piezoelectric element driver 20 Imaging device 21 Acceleration 22 Current value 23 Amplified current value 24 Quantized signal 25 Antiphase quantized signal 26 Displacement amount 27 Voltage indication signal 28 Voltage value 29 Displacement

Claims (5)

A lens unit including a lens capable of forming a subject image at a predetermined position;
A fixing member provided with the lens unit;
A support member that supports the lens unit movably in the optical axis direction with respect to the fixed member;
A piezoelectric element that moves the lens unit in the optical axis direction;
A controller unit for controlling the piezoelectric element;
An acceleration sensor capable of detecting acceleration in the optical axis direction of the lens unit;
Acceleration change detection means for outputting the change in acceleration based on an output signal of the acceleration sensor;
An antiphase signal generating means for inverting the output signal of the acceleration change detecting means to an antiphase,
Displacement amount calculating means for obtaining a displacement amount of the lens unit in the optical axis direction based on an output signal of the antiphase signal generating means;
The image pickup apparatus, wherein the controller unit controls the piezoelectric element according to an output signal of the displacement amount calculation means. The imaging apparatus according to claim 1, wherein the acceleration sensor is provided in the lens unit. The imaging apparatus according to claim 1, wherein the piezoelectric element is a bimorph type piezoelectric element. The imaging apparatus according to claim 1, wherein the support member is a parallel link mechanism. The imaging apparatus according to claim 1, wherein the support member is a guide shaft and a guide sleeve.

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