WO2020237450A1

WO2020237450A1 - Imaging device and information terminal

Info

Publication number: WO2020237450A1
Application number: PCT/CN2019/088464
Authority: WO
Inventors: Atsushi Yoneyama; Masaru Uno
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2019-05-27
Filing date: 2019-05-27
Publication date: 2020-12-03
Also published as: CN113940054B; CN113940054A; JP7324301B2; JP2022522306A

Abstract

An imaging device with a simple configuration and less power consumption of a drive mechanism is provided. The imaging device includes: a first lens group; a second lens group through which light transmitted through the first lens group passes; a first drive shaft that is in frictional engagement with the first lens group and is in frictional engagement with the second lens group with a friction force smaller than a friction force with the first lens group; a first piezoelectric element secured to one end portion of the first drive shaft to cause the first drive shaft to expand and contract; a second drive shaft that is in frictional engagement with the second lens group and is in frictional engagement with the first lens group with a friction force smaller than a friction force with the second lens group; a second piezoelectric element secured to one end portion of the second drive shaft to cause the second drive shaft to expand and contract; and a sensor that receives light transmitted through the first lens group and the second lens group.

Description

IMAGING DEVICE AND INFORMATION TERMINAL

Technical Field

The present disclosure relates to an imaging device and an information terminal and, more particularly, to a drive mechanism for achieving a zoom function and an auto focus (AF) function.

Background Art

Portable information terminals such as a smartphone often include an imaging function to function as a camera (imaging device) . This imaging function achieves a demanded zoom function and AF function by driving and operating lenses or the like.

The portable information terminals are each restricted in the thicknes s of its case, and it is desired that the imaging function is implemented by a mechanism that has a simple structure does not take much space. It is also desired that the actuator which constitutes a drive mechanism for the imaging function consumes low power.

It is an object of the present disclosure to provide an imaging device and an information terminal which are simple in configuration and whose drive mechanisms consume low power.

Summary of Invention

The present invention in its first aspect provides an imaging device including: a first lens group; a second lens group through which light transmitted through the first lens group passes; a first drive shaft that is in frictional engagement with the first lens group and is in frictional engagement with the second lens group with a friction force smaller than a coefficient of friction with the first lens group; a first piezoelectric element secured to one end portion of the first drive shaft to cause the first drive shaft to expand and contract; a second drive shaft that is in frictional engagement with the second lens group and is in frictional engagement with the first lens group with a friction force smaller than a friction force with the second lens group; a second piezoelectric element secured to one end portion of the second drive shaft to cause the second drive shaft to expand and contract; and a sensor that receives light transmitted through the first lens group and the second lens group.

The present invention in its second aspect provides an imaging device including: a lens group; a sensor that receives light transmitted through the lens group; a mirror that reflects incident light toward the lens group; and a control unit that performs optical image stabilization on a component in a direction orthogonal to an optical axis of the lens group by causing vibration at a position of the reflection of the mirror.

Brief Description of Drawings

[Fig. 1A] Fig. 1A is a perspective view showing a smartphone according to an embodiment of the present invention from a back surface thereof;

[Fig. 1B] Fig. 1B is a perspective view showing the smartphone according to the embodiment of the present invention from a front surface thereof;

[Fig. 2] Fig. 2 (a) is a plan view showing internal mechanisms of the smartphone according to the embodiment of the present invention and Fig. 2 (b) is a side view showing the same;

[Fig. 3] Fig. 3 is a diagram showing the layout relationship between magnets on a mirror side and coils on a sub chassis side;

[Fig. 4] Fig. 4 is a diagram showing a core member on which a coil is mounted;

[Fig. 5] Fig. 5 is a diagram showing changes in magnetic poles of core arms by current supply to the coils in rotational driving of the mirror;

[Fig. 6A] Fig. 6A is a diagram showing waveforms of hall elements that detect the rotation of the mirror;

[Fig. 6B] Fig. 6B is a diagram showing waveforms of the hall elements that detect the rotation of the mirror; and

[Fig. 7] Fig. 7 is a block diagram mainly showing a configuration for drive control of the smartphone of the present embodiment.

Description of Embodiments

The following will describe embodiments of the present invention with reference to the accompanying drawings. Figs. 1A and 1B are perspective views showing a smartphone functioning as an imaging device (camera) according to an embodiment of the present invention; Fig. 1A shows a view of the smartphone from the back surface thereof, and Fig. 1B shows a view of the smartphone from the front surface thereof.

In those drawings, a smartphone 100 includes an imaging mechanism to function as a camera (imaging device) . More specifically, an opening 103 is provided in a back surface 101B of the smartphone 100, and a lens is provided so as to close the opening 103. A mirror 3 is provided inside the opening 103, and the direction of light incident through the opening 103 is changed by the mirror 3 so that the light enters the optical system of the imaging mechanism provided inside the smartphone 100. Herewith, a user can perform imaging by operating a predetermined imaging button while directing the back surface 101B to a subject. Further, as shown in Fig. 1B, the mirror 3 is configured to be able to pop up through an upper part of the smartphone 100 through a pop-up unit 102. A lens is provided at the opening of the pop-up unit 102 so as to close the opening. The mirror 3 rotates 90 degrees from the state shown in Fig. 1A as the pop-up unit 102 pops up. This enables the user to perform imaging with the front surface 101A directed to the subject. In this manner, the smartphone 100 according to the present embodiment can perform imaging with either the back surface 101B or the front surface 101A directed to the subject. In addition, the pop-up mechanism provided for the mirror or the like permits almost the entire front surface 101A to serve as a display screen. In other words, it is unnecessary to provide an incident light path for imaging such as a lens in a part of the display screen, so that the arrangement and size of the display screen are not restricted.

Figs. 2 (a) and 2 (b) are respective a plan view and a side view each showing the configuration of the camera (imaging) function inside the smartphone according to the embodiment of the present invention.

The camera mechanism according to the present embodiment roughly includes a zoom lens group 10, an auto focus (hereinafter referred to as "AF" ) lens group 15, an aperture system 16, a sensor 18, and mirror 3 for guiding light from a subject to the sensor 18 through those lens groups. The zoom lens group 10 and the AF lens group 15 are provided together with their drive parts on an AF/zoom chassis 17. The mirror 3 and the sensor 18 are provided on a sub chassis 2. The AF/zoom chassis 17 is provided movably on the sub chassis 2. Further, the sub chassis 2 is provided movable with respect to a main chassis 1. The main chassis 1 constitutes a part of the chassis of the smartphone 100 of the present embodiment. Although the zoom lens group 10 and the AF lens group 15 in the present embodiment are each constituted by a plurality of lenses, both or one of the lens groups may be constituted by a single lens depending on the specifications of the camera.

The smartphone of the present embodiment has a rear-side camera mode and a front-side camera mode as described above with reference to Figs. 1A and 1B. In rear-side camera mode, as shown in Fig. 2 (b) , the rotational position of the mirror 3 is set to an angle at which light incident from the rear side of the smartphone is reflected through the opening 103 (Fig. 1A) to be guided to the lens groups. In front-side camera mode, on the other hand, the sub-chassis 2 is moved to the pop-up position, and the rotational position of the mirror 3 is set to an angle at which light incident from the front side of the smartphone via the pop-up unit 102 (Fig. 1B) is reflected to be guided to the lens groups.

The drive mechanisms for the zoom lens group 10 and the AF lens group 15 provided on the AF/zoom chassis 17 are as follows.

One end of the zoom lens group 10 is supported by a drive shaft 141 (first drive shaft) via a movement support part 151. The movement support part 151 and a drive shaft 141 are in frictional engagement with each other with a predetermined friction force. More specifically, the movement support part 151 has a V shaped cross-section whose inner surface is in line contact with the drive shaft 141 at two points. At the same time, a flat spring (not shown) abuts on the drive shaft 141 and presses the drive shaft 141 against the inner surface of the V shape of the movement support part due to its elastic force. This pressing causes the predetermined friction force. That end of the zoom lens group 10 which is opposite to the one end of the zoom lens group 10 in an X-axial direction is supported on a drive shaft 142 (second drive shaft) via a support part 161. The support part 161 and the drive shaft 142 are in engaged with each other with a friction force smaller than a friction force in the engagement of a movement support part 152 of the AF lens group 15 and the drive shaft 142. Specifically, the support part 161 has a U-shaped cross section, and the drive shaft 142 is engaged with the U-shaped inner surface with a fitting tolerance that forms a slight gap. Note that the cross-sectional shapes of the movement support part 151 and the support part 161 are of course not limited to the aforementioned shapes, and may of course take any shape as long as the friction force between the support part 161 and the drive shaft 142 is smaller than that between the movement support part 151 and the drive shaft 141. The same engagement relationship described above is also applied to the relationship of engagement of the support part 162 with the drive shaft 141 and the relationship of engagement of the corresponding movement support part 152 with the drive shaft 142.

For the zoom lens group 10, a weight 121 is attached to one end of the drive shaft 141, and one end of a piezoelectric element 131 (first piezoelectric element) is fixed to this weight 121. Further, one end of the drive shaft 141 is fixed to the other end of the piezoelectric element 131. The weight 121 is connected to a vertical chassis 171 by a flexible adhes ive. As a result, the weight 121 can move freely in the direction and the range of drive-based deformation of the piezoelectric element 131. The other end of the drive shaft 141 is held in a slidable manner by a vertical chassis 172. Note that the configuration for the action of the weight 121 is not limited to the aforementioned adhesive, and may take any form as long as the weight 121 can freely move within a predetermined range.

The AF lens group 15 also includes a drive mechanism similar to the drive mechanism for the aforementioned zoom lens group 10. That is, one end of the AF lens group 15 is supported by the drive shaft 142 via the movement support part 152. The movement support part 152 and the drive shaft 142 are in frictional engagement with each other by urging the drive shaft 142 toward the movement support part 152 having a V shaped cross-section, as mentioned above, by a flat spring (not shown) which contacts the drive shaft 142. Moreover, that end of the AF lens group 15 which is opposite to the one end of the AF lens group 15 in the X-axial direction is supported on the drive shaft 141 via the support part 162. As mentioned above, the support part 162 and the drive shaft 141 are engaged with each other by an allowance that forms a slight gap between the drive shaft 141 and the U-shaped cross section of the support part 162.

For the AF lens group 15, a weight 122 is attached to one end of the drive shaft 142, and one end of a piezoelectric element 132 (second piezoelectric element) is fixed to this weight 122. Further, one end of the drive shaft 142 is fixed to the other end of the piezoelectric element 13. The weight 122 is connected to the vertical chassis 172 by a flexible adhesive. The other end of the drive shaft 142 is held in a slidable manner by the vertical chassis 171.

The above-described principle of the driving by the drive mechanisms for the zoom lens group 10 and the AF lens group 15 are based on what is called smooth impact drive mechanism (hereinafter referred to as "SIDM" ) . The following is the description of the principle of driving the zoom lens group 10. As the drive shaft 141 is moved relatively slowly by driving the piezoelectric element 131 in an expansion direction of the piezoelectric element with the voltage applied to the piezoelectric element 131, the movement support part 151 moves together with the drive shaft 141 due to the frictional engagement with the drive shaft 141. Then, the piezoelectric element 131 is driven in the opposite direction, that is, in a contracted direction of the piezoelectric element so that the drive shaft 141 rapidly moves, causing the movement support part 151 to stay at the then position due to the relationship between the inertia of the movement support part 151 and dynamic friction with the drive shaft 141a. Repeating the aforementioned slow movement and rapid movement of the drive shaft 141 allows the movement support part 151, and thus the zoom lens group 10, to move in the negative direction of a Y axis. Further setting the moving speeds of the expansion and the contraction in the opposite relationship to the aforementioned moving speed relationship can move the zoom lens group 10 in the positive direction of the Y axis.

According to the present embodiment, driving of the zoom lens group 10 and the AF lens group 15 are performed as follows. An AF mode and a zoom mode are performed by connecting the movement of the zoom lens group 10 and the movement of the AF lens group 15 with each other. For example, when performing focusing at the same magnification with making an object different in a condition of focusing on an object at a zoom magnification, the AF lens group 15 is moved for focusing. Then, the zoom lens group 10 is moved due to changing of focusing on positon. More, when changing a zoom magnification without changing an object, a focusing on position is changed with moving of the zoom lens group 10 and thus the AF lens group is moved. As described above, the zoom lens group 10 and the AF lens group 15 are driven by corresponding

piezoelectric elements

131, 132 in any of the AF mode and the zoom mode. According to the present embodiment, driving frequencies of the respective piezoelectric elements are set to be respective proper frequencies in a range from around 200 KHz to around 300 KHz.

In the connected movements of the AF lens group 15 and the zoom lens group 10 with each other, so called “dithering effect” is caused in each of engagement relations of the support parts 161, 162 with

corresponding drive shaft

142, 141. More specifically, the connected movements of the above two lens groups cause the respective drive shafts to move in a vibrating manner and the engagements of correspond support parts 161, 162 with the respective drive shafts become to be engagements of dynamic frictions. Thus, the resistances due to the engagements are made small. As a result, driving forces of the

piezoelectric elements

131, 132 as driving sources for the AF lens group 15 and the zoom lens group 10 become to be small and thus power consumption can be decreased.

Note that even when any of the AF lens group 15 and the zoom lens group 10 is not moved, the dithering effect can be caused. The drive shaft may become in an idling state in which the drive shaft for moving the lens group that is not moved is vibrated by the corresponding piezoelectric element with a sine curve of a several KHz. This idling state allows the dithering effect to be caused between the support part for the lens group in moving and the vibrated drive shaft.

Further, although in the above described embodiment, the drive frequencies of

piezoelectric elements

131, 132 are set to be values in the range from around 200 KHz to around 300 KHz, the drive frequencies are of course not limited to these values. The respective drive frequencies of the two piezoelectric elements may be changed depending on conditions such as specifications and product shapes of the imaging device or the smartphone and may be determined according to be values that cause connected motions of the two lens groups and the dithering effect between the two lens groups.

Although the foregoing description is associated with the driving of the zoom lens group and the AF lens group, the two lens groups (first lens group and second lens group) are of course not limited to the zoom lens group and the AF lens group. The foregoing configurations and driving methods can be applied to any type of lens group as long as the target lens groups are two of the lens groups constituting the camera mechanism which are connectedly driven.

The aperture system 16 is provided in front of the AF lens group 15 along the optical axis, and adj usts the aperture with two levels of aperture sizes.

A magnet 11 is provided on the rear side of the AF/zoom chassis 17 on which the above-described optical system is mounted. A coil 20 is provided on the sub chassis 2 at a position where the coil 20 can face the magnet 11. The AF/zoom chassis 17 is provided to be movable with respect to the sub chassis 2 through three balls 4. This configuration can implement optical image stabilization (hereinafter referred to as "OIS" ) to be described later.

The sensor 18 is positioned at the back of the aforementioned optical system along the optical axis of the optical system. This sensor 18 is held by a sensor holder 19 fixed to the sub chassis 2.

The mirror 3, as described above, changes its rotational position between the rear-side camera mode and the front-side camera mode. The mirror 3 takes a vibrating action in the rotational direction for the OIS as described later. The following presents a mechanism for driving this mirror 3.

The mirror 3 is held to be rotatable about an axis parallel to the X axis by a support part 201 (not shown in Fig. 2 (b) ) provided on the sub chassis 2. A disc-shaped yoke 5 is attached to one side surface of the mirror 3, and a magnet 6 is attached to the yoke 5. This allows the mirror 3 and the magnet 6 to rotate together. A coil 7 is provided on the sub chassis 2 at a position facing the magnet 6 of the mirror 3.

Fig. 3 is a diagram showing the relationship of arrangement of the magnet 6 on the mirror 3 side and the coil 7 on the sub chassis 2 side, and Fig. 4 is a diagram showing a core member 70 on which the coil 7 is mounted.

As shown in Fig. 3, the magnet 6 includes twelve N-pole magnetized parts 6A, and also twelve S-pole magnetized parts 6B. As shown in Figs. 3 and 4, the coil 7 includes two kinds of

coils

7A and 7B, which are wound so as to pass through channels formed between core arms 71 to 78 of the core member 70. Specifically, the coils 7A and the coils 7B are arranged on the core member 70 with a phase difference of 90 degrees. In addition, both of the

coils

7A and 7B are arranged all around the magnet 6. Input-side terminals and output-side terminals of those coils (neither shown) are provided at predetermined locations. Note that the

coils

7A and 7B are present on each of the two layers of a coil substrate. Accordingly, currents flowing through the

coils

7A and 7B do not interfere with each other.

Fig. 5 is a diagram showing changes in magnetic poles of the core arms by current supply to the coil 7 in rotational driving of the mirror 3. When the rotational angle of the mirror 3 is 0 degrees (initial state) , the current supply to the

coils

7A and 7B set the magnetic poles of the core arms 71 to 78 to N, S, ... N, and S. As the current supply to the

coils

7A and 7B is controlled from this state to set the magnetic poles of the core arms 71 to 78 to S, N, ... S, and N, so that the mirror 3 rotates clockwise (CW) by 15 degrees. Changing the magnetic poles of the core arms 71 to 78 similarly allows the mirror 3 to rotate by 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees. When the N pole or the S pole of the magnet 6 directly faces the core arms 71 to 78 at such a rotational position, the rotational position becomes a magnetically stable point. As the current supply to the

coils

7A and 7B is cut off in that state, the position of the magnet 6 to the coil 7, and thus the position of the mirror 3 thereto is fixed. According to the present embodiment, the mode at a certain fixed point among those fixed points where the rotational angle of the mirror 3 is 0 degrees is referred to as the rear-side camera mode, and the mode at a certain fixed point among those fixed points where the rotational angle of the mirror 3 is 90 degrees is referred to as the front-side camera mode. At the time of transition to the rear-side camera mode from the front-side camera mode, the mirror 3 is rotated counterclockwise (CCW) to change the rotational position of the mirror 3.

Figs. 6A and 6B are diagrams showing waveforms of

hall elements

28A and 28B that detect the aforementioned rotation of the mirror 3. Fig. 6A shows waveforms the

hall elements

28A and 28B detect when the mirror 3 rotates clockwise, and a combined waveform of those detected waveforms, and Fig. 6B shows waveforms the

hall elements

28A and 28B detect when the mirror 3 rotates counterclockwise, and a combined waveform of those detected waveforms. In the present embodiment, the hall element 28A and the hall element 28B are disposed at positions separated from each other by an equivalent electrical angle of 90 degrees.

Whether the mirror 3 rotates clockwise or counterclockwise is determined by a phase difference between a combined waveform 28C and the waveforms detected by the

hall elements

28A and 28B. Moreover, the number of times the hall element passes the poles of the magnet 6 can be counted, that is, the rotational angle can be detected by the number of times the waveform detected by the hall element 28A crosses "0. "

According to the present embodiment, OIS is carried out by using the driving of the mirror 3. That is, with the mirror 3 fixed at a position of 0 degrees or 90 degrees or the rotational position of each of the rear-side camera mode or the front-side camera mode, OIS in a Z-axial direction can be controlled by using the hall element 28A. More specifically, the mirror 3 (magnet 6) is rotated by supplying current to the coil 7 and the rotational position of the mirror 3 is detected by the hall element 28A. On the condition that the range of the rotational position of the mirror 3 which is detected by the hall element 28A is set to a servo area shown in Fig. 6A, OIS in the Z-axial direction can be performed by rotating (vibrating) the mirror 3 (magnet 6) within this range. The following presents an example of the servo area. When the size detected by the hall element 28A is 3.5 mm, the angle of opening per magnetic pole is 360/24 which is 15 degrees. This angle is 0.46 nm in terms of distance, so that the range of the servo area that guarantees linearity becomes 0.32 mm on the condition that the margin is 70%. In other words, given that this area is assumed to be ±0.16 mm, OIS can be controlled within the range of ±5.2 degrees in terms of angle. In an example of the range of this servo control, given that the distance to the sensor 18 from the point of reflection of the mirror 3 is 10 mm, the moving distance of a light spot on the sensor 18 is about 1.835343446 mm. This value has a sufficient margin as compared with the moving distance of 150 μm of a light spot in ordinary OIS.

Referring again to Figs. 2 (a) and (b) , the configuration of OIS will be described. OIS in the X-axial direction can be performed by moving the AF/zoom chassis 17 in a direction along the X axis. Specifically, the AF/zoom chassis 17 is moved by a required distance in the X-axial direction by controlling the current supply to the coil 20 provided on the sub chassis 2 based on an image detected by the sensor 18. This can ensure execution of OIS in the X-axial direction. Further, OIS in the Z-axial direction is carried out through control using the hall elements with the rotational position of the mirror 3 being fixed at 0 degrees or 90 degrees, as described above.

As apparent from the above, the mirror 3 can be used in in OIS as well as switching of the optical path for the double-side camera modes, so that functions such as OIS can be implemented with a simple configuration without requiring a large space for the components.

The above-described optical system including the mirror 3 is mounted on the sub chassis 2. As this sub chassis 2 moves relative to the main chassis 1, pop-up associated with the front-side camera mode is enabled. The sub chassis 2 includes a bearing part 29 on one side surface in the X-axial direction, and a guide part 30 on the other side surface. The bearing part 29 is provided on the main chassis 1, and is engaged in a slidable manner with a main shaft 8 extending in the Y-axial direction. The guide part 30 is engaged in a slidable manner with a guide rail (not shown) extending in the Y-axial direction. That is, the sub chassis 2 is supported on the main chassis 1 via the main shaft 8 and the guide rail, and is movable in the Y-axial direction.

The main shaft 8 with which the bearing part 29 on the sub chassis 2 is engaged has both ends supported by respective support parts of the main chassis 1. A spring 22 is disposed between that support part in the two support parts on the sensor side at the back of the optical system, and the bearing part 29 to normally urge the bearing part 29 toward the front of the optical system. The bearing part 29 abuts on a nut 23 which is screwed over a lead screw 9 extending in the Y-axial direction on the opposite side to the portion at which the bearing part 29 is in contact with the spring 22. The elasticity of the spring 22 present absorbs the force erroneously exerted by a user to press the pop-up unit 102 at the pop-up position back into the smartphone, so that the influence on other members can be reduced.

The rotational driving of the lead screw 9 is carried out with a piezo type actuator 21 serving as a drive source. Specifically, the actuator 21 is caused to abut on a rotor 25 by a spring 24 surrounding the actuator 21. Then, a high-frequency voltage is applied to the actuator 21 to cause expansion/contraction, so that a metal chip mounted on the distal end of the actuator 21 makes elliptic motion, allowing the rotor 25 to rotate due to the friction between the metal chip and the rotor 25. The rotor 25 can be rotated reversely by changing the phase relationship of the applied voltage. The rotation of the rotor 25 causes rotation of a coaxial first gear 26, which rotation causes rotation of a second gear 27 which engages with the first gear 26. One end of the lead screw 9 is fixed to the second gear 27, which permits rotation of the lead screw 9. With the above-described configuration, when the lead screw 9 is rotated in a predetermined direction, the nut 23 advances in the positive direction of the Y axis, so that the bearing part 29 urged by the spring 22 can move in the same positive direction of the Y axis while in abutment with the nut 23. Therefore, the sub chassis 2 can move in the positive direction of the Y axis. The movement of the sub chassis 2 in the negative direction of the Y axis can be enabled by the reverse rotation of the rotor 25. As a result, the pop-up unit 102 can be popped up through the top portion of the smartphone 100 and popped into the smartphone 100.

Fig. 7 is a block diagram mainly showing a configuration for drive control of the smartphone 100 of the present embodiment.

The smartphone 100 of the present embodiment includes a processing unit 111 that performs data processing and control on the operations of the individual components in the smartphone 100. A ROM 112 and a RAM 113 are storage units which are used at the time the processing unit 111 performs processing and control. The smartphone 100 also includes a display device 114 and an input device 115, and performs display on a display part of the front surface 101A and input processing via the display part.

A camera unit 180 includes drive units that control the above-described driving of the individual units. That is, a zoom-lens group drive unit 181 controls the above-described driving of the zoom lens group 10 under control of the processing unit 111, and an AF-lens-group drive unit 182 likewise controls the above-described driving of the AF lens group 15 under control of the processing unit 111. A mirror drive unit 183 controls the rotation of the mirror 3 as described above with reference to Figs. 5, 6A and 6B. Further, an AF/zoom-chassis drive unit 184 controls the above-described movement of the AF/zoom chassis 17, and a sub-chassis drive unit 185 controls the above-described movement of the sub chassis 2.

Claims

An imaging device comprising:

a first lens group;

a second lens group through which light transmitted through the first lens group passes;

a first drive shaft that is in frictional engagement with the first lens group and is in frictional engagement with the second lens group with a friction force smaller than a friction force with the first lens group;

a first piezoelectric element secured to one end portion of the first drive shaft to cause the first drive shaft to expand and contract;

a second drive shaft that is in frictional engagement with the second lens group and is in frictional engagement with the first lens group with a friction force smaller than a friction force with the second lens group;

a second piezoelectric element secured to one end portion of the second drive shaft to cause the second drive shaft to expand and contract; and

a sensor that receives light transmitted through the first lens group and the second lens group.
The imaging device according to claim 1, wherein

when the first lens group is moved by driving the first piezoelectric element to cause the first drive shaft to respectively move in directions in which the first piezoelectric element expands and contracts, the second piezoelectric element is driven to cause the second drive shaft to be respectively moved in directions in which the second piezoelectric element expands and contracts so that the second drive shaft is moved connectedly with the movement of the first drive shaft, and when the second lens group is moved by driving the second piezoelectric element to cause the second drive shaft to respectively move in directions in which the second piezoelectric element expands and contracts, the first piezoelectric element is driven to cause the first drive shaft to be respectively moved in directions in which the first piezoelectric element expands and contracts so that the first drive shaft is moved connectedly with the movement of the second drive shaft.
The imaging device according to claim 1 or 2, further comprising:

a lens group support part on which the first lens group, the second lens group, the first drive shaft, the first piezoelectric element, the second lens group, and the second piezoelectric element are mounted,

the lens group support part being provided movable with respect to the sensor.
The imaging device according to any one of claims 1 to 3, further comprising:

a mirror that reflects incident light toward the first lens group, and directs lights incident from a front surface and a back surface of the imaging device toward the first lens group by changing a rotational position of the mirror.
The imaging device according to claim 4, wherein

the imaging device demonstrates a zoom function by movement of the first lens group, demonstrates an auto focus function by movement of the second lens group, demonstrates a function of optical image stabilization on components in directions orthogonal to an optical axis of the first lens group and the second lens group by movement of the lens group support part, and demonstrates a function of optical image stabilization on a component in a direction that is orthogonal to the direction orthogonal to the optical axis and is parallel to a surface of the sensor by causing vibration at a position of the reflection of the mirror.
An imaging device comprising:

a lens group;

a sensor that receives light transmitted through the lens group;

a mirror that reflects incident light toward the lens group; and

a control unit that performs optical image stabilization on a component in a direction orthogonal to an optical axis of the lens group by causing vibration at a position of the reflection of the mirror.
The imaging device according to claim 6, wherein

the mirror directs lights incident from a front surface and a back surface of the imaging device toward the lens group by changing a rotational position of the mirror.
An information terminal comprising:

the imaging device according to any one of claims 1 to 7.