JP2012078418A - Autofocus device, imaging apparatus mounting the autofocus device, and portable electronic device mounting the imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an autofocus device, an imaging apparatus, and a portable electronic device for enhancing starting speed of a camera.SOLUTION: The autofocus device includes: a lens 13 condensing the light from a subject; a lens holder 15 housing the lens 13; a frame 16 housing the lens 13 via the lens holder 15; a support member 17 attached to the upper part or the lower part of the subject side of the frame 16, and elastically supporting the lens holder 15 in an optical axis direction; and shape-memory alloy 18 connected to the frame 16 and the lens holder 15, and moving the lens 13 in the optical axis direction by extending and contracting. The shape-memory alloy 18 is attached in such a manner that the lens 13 moves towards the subject when the shape-memory alloy 18 extends. A drive part 20 driving the shape-memory alloy 18 performs preliminary calibration operation.

Description

  The present invention relates to an autofocus device, an imaging device equipped with the autofocus device, and a portable electronic device equipped with the imaging device, such as a digital camera, a mobile phone with a camera function, and a personal digital assistant (PDA). It is.

  Conventionally, some autofocus devices use a shape memory alloy for an actuator in order to increase the speed of autofocus. This autofocus device supplies power to the shape memory alloy to generate heat and shrink the shape memory alloy to move the lens in one direction, and the shape memory alloy naturally dissipates and expands the lens. It is comprised so that it may move in the direction opposite to the said direction.

In these autofocus devices, the position of the lens is controlled by a resistance value corresponding to the deformation amount of the shape memory alloy, that is, a resistance value that decreases by contraction and increases by extension.
In order to prolong the life of such an autofocus device, the shape memory alloy is heated, the measurement resistance is monitored, the maximum resistance and the minimum resistance are detected, and the resistance value of the detected maximum resistance is detected. A pre-calibration operation is performed which includes deriving and storing the magnitude of the resistance range between the resistance values of the minimum resistances. (For example, patent document 1).

  This pre-calibration operation is performed only when power is supplied or the device is switched on, and after the pre-calibration operation, the lens position is moved to the initial position. Normally, this initial position is set so that the lens is at infinity (for example, Patent Document 2).

Special table 2010-518438 gazette JP-A-5-5835

However, in the above-described autofocus device, the lens moves in a direction in which the lens deviates from the image sensor when the shape memory alloy generates heat and contracts in order to reduce the holding power at the initial position, which is an infinite position. Due to the moving configuration, there is a problem that the time from the execution of the preliminary calibration operation to the movement to the infinite position close to the image sensor becomes longer, and the startup time of the camera becomes longer.
The present invention solves the above-described problem, and an object of the present invention is to provide an autofocus device that can shorten the time for moving the lens to the initial position after the preliminary calibration operation.

A lens that collects light from a subject; a lens holder that houses the lens; a frame that houses the lens through the lens holder; and an upper or lower portion of the frame on the subject side; And a shape memory alloy that is connected to the frame and the lens holder and moves the lens in the optical axis direction by extending and contracting, and the shape memory alloy extends. The lens is attached so as to move in the direction of the subject.

According to this configuration, when the shape memory alloy is stretched, the lens is attached so as to move in the direction of the subject, so that the resistance value of the shape memory alloy when the initial position that is an infinite position is maintained is the minimum resistance value. Therefore, the difference in resistance value before moving to the initial position after the preliminary calibration operation can be reduced, so that the time for moving to the initial position after the preliminary calibration operation can be shortened.
In an autofocus device according to a second aspect of the present invention, the autofocus device includes a drive unit that expands and contracts the shape memory alloy, and a control unit that instructs the drive unit to operate, and the drive unit energizes the shape memory alloy. When acquiring the resistance value measured by the resistance value measurement unit when moving the lens to an arbitrary position, the current value to be calculated, the resistance value measurement unit for calculating the resistance value of the shape memory alloy, A drive control unit for instructing the energization unit to energize the shape memory alloy until a resistance value corresponding to an arbitrary position, and controlling the energization unit to heat the shape memory alloy, By monitoring the measurement resistance of the shape memory alloy, the maximum resistance value and the minimum resistance value are detected, and a preliminary calibration operation for deriving and storing the resistance range between the maximum resistance value and the minimum resistance value can be executed, and the control Is the preliminary calibration operation And controlling the driving unit to move the lens to the initial position after.
According to such a configuration, by using the minimum resistance value, it becomes difficult to be influenced by a change in the resistance value of the ambient temperature, thereby enabling accurate positioning of the movable element.
In addition, by using the resistance value between the minimum resistance value and the maximum resistance value, and operating within the range not exceeding the minimum resistance value, it is possible to reduce the damage to the shape memory alloy crystal and prolong the life of the shape memory alloy actuator It becomes.
The image pickup apparatus according to the present invention includes the autofocus device according to claim 1 or 2.

According to this configuration, the same effect as described above can be obtained in the imaging apparatus.
The portable electronic device according to the present invention is characterized in that the imaging device according to claim 3 is mounted.
According to this configuration, the same effect as described above can be obtained even in a portable electronic device.

  According to the present invention, it is possible to shorten the time for moving the lens to the initial position after the preliminary calibration operation, as compared with the conventional autofocus device.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole external view which shows the open state of the portable electronic device which concerns on one Embodiment of this invention, Comprising: (a) is a whole external view which shows a front side, (b) is a whole external view which shows a back side. Sectional drawing which shows the imaging device containing the autofocus apparatus based on the embodiment A block diagram of a system configuration showing an imaging device including an autofocus device according to the embodiment (A) is a figure which shows the phase of the time of the autofocus apparatus which concerns on the same embodiment, and the position of a lens, (b) is a figure which shows the correlation of time and resistance value of the autofocus apparatus which concerns on the same embodiment (A) is a figure which shows the phase of the time of a conventional autofocus apparatus, and the position of a lens, (b) is a figure which shows the correlation of the time of a conventional autofocus apparatus, and resistance value.

  Hereinafter, an embodiment of an autofocus device, an imaging device, and a portable electronic device according to the present invention will be described with reference to FIGS. Note that a case where the autofocus device according to the present embodiment is employed in an imaging device will be described. The case where the imaging device according to the present embodiment is employed in a portable electronic device will be described.

  First, a schematic configuration of the portable electronic device according to the present embodiment will be described with reference to FIG. FIG. 1 is an overall view of a portable electronic device according to the present embodiment. The mobile electronic device 1 according to the present embodiment is a so-called foldable mobile phone. FIG. 1A is a perspective view from a direction in which the foldable mobile phone is open and a main screen (a first display 10 to be described later) is visible. FIG. 4B is a perspective view from the back side (the side opposite to the surface on which the main screen is fitted) of the mobile phone shown in FIG.

  The mobile electronic device 1 according to the present embodiment is a mobile phone equipped with a digital camera function, that is, provided with an imaging device 2. The mobile phone 1 includes a first main body 3 and a second main body 5 that can be folded via the first main body 3 and the hinge mechanism 4.

  The first main body 3 includes an operation key unit 6 configured by numeric keys and the like for inputting operations of the mobile phone 1 and a microphone 7 for inputting a transmission voice on the inner surface side when the mobile phone 1 is folded. Is provided. In addition, the first main body 3 is provided with a sounder 8 for notifying an incoming state or the like on the outer surface side when the cellular phone 1 is folded.

  The second main body 5 is provided with a speaker 9 for outputting received voice and a first display 10 for displaying characters and images on the inner surface side when the cellular phone 1 is folded. The second main body 5 includes a second display 11 that displays characters and images on the outer peripheral surface when the cellular phone 1 is folded, a light emitting element 12 that emits light, and a subject. And an imaging device 2 that collects the light reflected by the light (light from the light emitting element 12 or light such as sunlight).

  The configuration of the portable electronic device 1 according to the present embodiment is as described above. Hereinafter, the configuration of the imaging device 2 according to the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a cross-sectional view of the imaging apparatus 2 according to the embodiment. FIG. 3 is a block diagram showing a system configuration of the imaging apparatus 2 according to the embodiment.

As shown in FIG. 2 or 3, the imaging apparatus 2 according to the present embodiment accommodates a lens 13 that collects light from a subject, an imaging element 14 that receives light via the lens 13, and the lens 13. The lens holder 15 to be mounted, the frame 16 for housing the lens 13 via the lens holder 15, and the upper and lower portions of the frame 16 on the subject side, and the lens holder 15 in the optical axis direction (A arrow direction in FIG. 2) The actuator is connected to the support member 17 that is elastically supported, for example, a metal (or resin, etc.) leaf spring, the frame 16 and the lens holder 15, and moves the lens holder 15 in the optical axis direction by expanding and contracting. A shape memory alloy 18. Then, a substrate 19 that is electrically connected to the image sensor 14 and fixed to the frame 16, a drive unit 20 that expands and contracts the shape memory alloy 18, an image signal from the image sensor 14 is processed, and autofocus is performed. And a control unit 21 for instructing the drive unit 20 to operate each time it moves to each designated position.
The autofocus device 22 includes the lens holder 15, the frame 16, the support member 17, the shape memory alloy 18, and the drive unit 20. Note that the control unit 21 may be built in the imaging device 14.
The lens 13 is integrated with the lens holder 15 so as to be movable in the optical axis direction (A arrow direction in FIG. 2) in the focus area of the imaging device 2. In the present embodiment, one lens 13 is provided. However, the present invention is not limited to this, and two or more lenses 13 may be provided.
The lens holder 15 is formed in a cylindrical shape, and is arranged so that the axis of the lens 13 coincides with the optical axis (dashed line). Further, the lens holder 15 includes a guided portion (not shown and numbered) guided by a guide portion (not shown and numbered) provided on the frame 16 so as to move stably in the optical axis direction. The lens holder 15 is not limited to the above-described embodiment, and the lens 13 is held on the inner side, a male screw is formed on the outer side, and a female screw and a screw formed on the inner side of an outer holder (or lens carrier) (not shown). The structure which unites may be taken (for example, refer FIG. 2 etc. of the special table | surface 2010-518438 gazette). In this case, the outer holder is elastically supported in the optical axis direction by the support member 17 (suspension element).

  The shape memory alloy 18 is formed in a V shape (in FIG. 2, two sides of the V shape are overlapped). That is, in the shape memory alloy 18, the V-shaped end portions 18 a and 18 c are fixed to the frame 16, and the V-shaped valley portion 18 b is fixed to the lens holder 15. The shape billion alloy 18 is supplied with heat (for example, voltage (power, current)) from both ends 18a and 18c of the V-shape, and is deformed (stretched) in the direction of the optical axis as a whole, and as a result, the lens The lens 13 is moved by adjusting the distance between the holder 15 and the frame 16. In addition, you may provide an external heater etc. separately as a means to supply heat.

Specifically, the shape memory alloy 18 generates heat and contracts when a voltage is applied to move the lens 13 in one direction, and naturally dissipates and extends the lens 13 in a direction opposite to the one direction. Configured to be moved. More specifically, the shape memory alloy 18 contracts the lens 13 and the image sensor 14 by contracting, and separates the lens 13 and the image sensor 14 by extending.
And the drive part 20 expands / contracts the shape memory alloy 18 by receiving a movement instruction (operation instruction) from the control part 21, for example, a communication signal, and moves the lens holder 15 in the optical axis direction. The drive unit 20 moves the lens 13 to a designated position based on a movement instruction from the control unit 21 and holds the position until a next movement instruction is received from the control unit 21.

At that time, while the resistance value of the shape memory alloy 18 corresponding to the deformation amount of the shape memory alloy 18 is monitored by the resistance value measuring unit 24, the drive control unit 25 supplies power to the energizing unit 23 based on the resistance value. The position of the lens 13 is controlled by controlling and adjusting the deformation amount of the shape memory alloy 18. The drive unit 20 modulates the voltage applied to the shape memory alloy 18 by pulse control (PWM control), that is, by modulating the time (pulse width) during which a predetermined voltage value is applied. It is adjusted.
That is, as shown in FIG. 3, the drive unit 20 includes an energization unit 23 that energizes the shape memory alloy 18 and a resistance value measurement unit that measures the resistance value of the shape memory alloy 18 when energized by the energization unit 23. 24, and a drive control unit 25 for controlling energization to the energization unit 23 based on the resistance value of the shape memory alloy 18 measured by the resistance value measurement unit 24 in order to move the lens holder 15 to a predetermined position. It is a thing. Accordingly, the drive unit 20 monitors the measurement resistance of the shape memory alloy 18 to detect the maximum resistance value and the minimum resistance value, and derives and stores the resistance range between the maximum resistance value and the minimum resistance value. Can be executed. The resistance value range used after the pre-calibration operation uses a value between the stored maximum resistance value and minimum resistance value.

  Next, the preliminary calibration operation of the imaging apparatus 2 according to the present embodiment will be described in detail with reference to FIGS. 4A is a phase diagram between the time of the autofocus device according to the embodiment and the position of the lens, and FIG. 4B is a correlation diagram between the time and resistance value of the autofocus device according to the embodiment. 5A is a phase diagram between the time of the conventional autofocus device and the lens position, and FIG. 5B is a correlation diagram between the time and the resistance value of the conventional autofocus device.

In this configuration, since the lens 13 is mounted so as to move in the direction of the subject when the shape memory alloy 18 is extended, the lens 13 is not energized as shown in FIG. 4A. Is the position of Pmax. Therefore, when performing the pre-calibration operation, first, the operation starts from the position of the peak position Pmax, and the lens 13 moves in the direction approaching the image pickup device 14 and corresponds to the most moving point of the pre-preparation operation. The preliminary calibration operation is completed via the bottom position Pmin. Here, the peak position is a state in which the shape memory alloy 18 is in a non-energized state, and the lens 13 is most distant from the image sensor 14, that is, a state in which the lens 13 is close to the subject. This indicates the state that is closest to the image sensor 14, that is, is separated from the subject. Thereafter, the lens 13 is moved to the initial position Pini1.
FIG. 4B illustrates this series of operations as a change in resistance value. When the preliminary calibration operation is started, the preliminary calibration operation is performed after the minimum resistance value Rmin is detected via the maximum resistance value Rmax. End. Thereafter, the resistance value changes to the resistance value Rini1 corresponding to the initial position Pini1.

Generally, the initial position of the lens is set to a position where the focal point is at infinity. Therefore, in the case of this configuration, the lens 13 approaches the image sensor 14 when the shape memory alloy 18 contracts, and therefore corresponds to the initial position. The resistance value is close to the minimum resistance value. Therefore, the pre-calibration operation is completed, and the time for moving from the situation where the resistance value of the shape memory alloy 18 is in the vicinity of the minimum resistance value to the resistance value corresponding to the initial position is shortened. That is, the time T from the preliminary calibration operation to the movement to the initial position can be shortened.
On the other hand, in the conventional configuration, when the shape memory alloy 18 is contracted, the lens 13 is mounted so as to move in the direction of the subject. Therefore, as shown in FIG. Then, the lens 13 is in the position of the bottom position Pmin. Therefore, when the preliminary calibration operation is performed, the lens 13 is first operated from the position of the bottom position Pmin, and the lens 13 moves in a direction away from the image pickup device 14 while performing the preliminary training operation. The preliminary calibration operation is completed via the peak position Pmax corresponding to the most moved point. Here, the bottom position is a state in which the shape memory alloy 18 is in a non-energized state, and the lens 13 is closest to the image sensor 14, that is, a state in which the lens 13 is separated from the subject, and the peak position is the lens 13. Is the most distant from the image sensor 14, that is, a state of approaching the subject. Thereafter, the lens 13 is moved to the initial position Pini2.
FIG. 5B illustrates this series of operations as changes in resistance value. When the preliminary calibration operation is started, the preliminary calibration operation is performed after detecting the minimum resistance value Rmin via the maximum resistance value Rmax. End. Thereafter, the resistance value Rini2 corresponding to the initial position Pini2 changes.
However, in the case of the conventional configuration, when the shape memory alloy 18 is contracted, the lens 13 is separated from the image sensor 14, so that the resistance value corresponding to the initial position is close to the maximum resistance value. Therefore, the pre-calibration operation is completed, and the time is increased because the shape memory alloy 18 moves from the situation where the resistance value is near the minimum resistance value to the resistance value (near the maximum resistance value) corresponding to the initial position. That is, the time T from the preliminary calibration operation to the movement to the initial position becomes long.

  In particular, since the movement from the end of the preliminary calibration to the initial position is a direction in which the shape memory alloy moves due to heat dissipation, the movement time may become longer depending on the ambient temperature of the shape memory alloy 18.

  The portable electronic device 1, the imaging device 2, and the autofocus device 22 according to the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. Of course.

  An autofocus device according to the present invention, an imaging device equipped with the autofocus device, and a portable electronic device equipped with the imaging device constitute a digital camera, a mobile phone with a camera function, a personal digital assistant (PDA), and the like It can be used effectively as something to do.

13 Lens 15 Lens holder 16 Frame 17 Support member 18 Shape memory alloy (actuator)

Claims (4)

A lens that collects light from a subject; a lens holder that houses the lens; a frame that houses the lens through the lens holder; and an upper or lower portion of the frame on the subject side; And a shape memory alloy that is connected to the frame and the lens holder and moves the lens in the optical axis direction by extending and contracting, and the shape memory alloy extends. And an autofocus device, wherein the lens is mounted to move in the direction of the subject. A drive unit for expanding and contracting the shape memory alloy; and a control unit for instructing the drive unit to perform an operation, and the drive unit includes an energization unit for energizing the shape memory alloy, and a resistance value of the shape memory alloy. When calculating the resistance value measurement unit and moving the lens to an arbitrary position, the shape is obtained until the resistance value corresponding to the arbitrary position is obtained while acquiring the resistance value measured by the resistance value measurement unit. A drive control unit for instructing the energization amount to the memory alloy to the energization unit, heating the shape memory alloy by controlling the energization unit, and monitoring the measurement resistance of the shape memory alloy to maximize the resistance A preliminary calibration operation for detecting a value and a minimum resistance value, and deriving and storing a resistance range between the maximum resistance value and the minimum resistance value, and the control unit moves the lens to an initial position after executing the preliminary calibration operation. Said drive part to be moved Autofocus device according to claim 1, characterized in that control. An imaging apparatus comprising the autofocus device according to claim 1. A portable electronic device comprising the imaging device according to claim 3.

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