JP4637537B2 - Lens driving device and digital camera - Google Patents

Description

  The present invention relates to a lens driving device that detects the origin position of a lens and controls the lens position, and a digital camera equipped with the lens driving device.

  Many small-sized devices such as mobile phones and PDAs (Personal Digital Assistants) that incorporate an imaging device that captures a subject and acquires a digital photographed image are commercially available. In recent years, along with the widespread use of small devices with built-in imaging devices, high-quality small CCDs and high-contrast small lenses have been developed, and photographing is performed using small devices such as mobile phones and PDAs. The quality of captured images is rapidly increasing. However, the imaging devices built into these small devices are considerably smaller than ordinary digital cameras, so the size of components such as lenses and CCDs and the space for storing these components are greatly limited. Is done.

In an autofocus function and a zoom function provided in a digital camera or video camera of a normal size, a lens driving device that moves a plurality of lenses in the optical axis direction using a DC motor or a stepping motor is provided in the imaging device Patent Documents 1 to 4 describe a lens driving device that uses a hollow stepping motor instead of a DC motor to move a lens barrel in the optical axis direction. In such a hollow stepping motor, the lens driving device can be miniaturized by integrating the lens barrel and the hollow rotor constituting the hollow stepping motor. In the lens driving device, it is important to detect the origin position of the lens in order to control the position of the lens with high accuracy. Therefore, the lens driving device is provided with optical position detection means such as a photo interrupter to detect the origin position of the lens.
JP 60-415 JP-A-60-416 JP 60-417 Japanese Patent Laid-Open No. 62-195615

  However, even if a lens driving device using a hollow type stepping motor as described in Patent Documents 1 to 4 described above is provided in the imaging device to reduce the size of the imaging device, improve the accuracy of lens movement control, etc. If the origin position of the lens is detected using a photo interrupter as in the past, the installation space for the photo interrupter must be secured in the lens driving device, and there is a problem that the lens driving device is enlarged. .

  The present invention has been made to solve the above-described problems. A small lens driving device that detects the origin position of a lens and accurately controls the lens position, and a digital camera including the lens driving device are provided. The purpose is to provide.

  In order to achieve the above object, a lens driving device according to the present invention has a cylindrical shape, a stator that forms a magnetic field in the cylindrical shape, and is positioned within the cylindrical shape of the stator and coaxial with the cylindrical shape. A rotor having a cylindrical shape and rotating with respect to the stator by a magnetic field formed by the stator, and a cylindrical lens holder positioned further inside the cylindrical shape of the rotor and holding a lens, In the lens driving device that moves the lens holder along the optical axis direction by rotation of the rotor, the conductor provided on one end surface of the lens holder and the lens holder move to one end position of the moving range A pair of electrodes provided opposite to the conductive member, and an electrostatic capacitance connected between the electrodes and formed between the electrode and the conductive member. And a determination unit that determines that the lens holder is at the origin position based on a change in capacitance detected by the capacitance detection unit. It is what. The conductor may be a washer having the same shape as the end surface of the lens holder.

  The digital camera according to the present invention includes the lens driving device described above, an imaging unit that captures an image of a subject formed by the lens and acquires image data, and the image data captured by the imaging unit. Storage means for storing.

  According to the lens driving device and the digital camera of the present invention, the lens drive in which the rotor rotated by the magnetic field formed by the stator and the lens holder disposed in the rotor move along the optical axis direction by the rotation of the rotor. In the apparatus, a conductor provided at one end of the lens holder and a pair of electrodes are provided so as to face the conductor when the lens holder is moved to one end position of the moving range. Since the capacitance formed between the electrodes is detected and it is determined that the lens is at the origin position based on the change in the capacitance, the lens drive is compared with the case where a photo interrupter is used. The apparatus and the digital camera can be downsized.

  In the present embodiment, a camera-equipped cellular phone in which a digital camera using the lens driving device of the present invention is incorporated in a cellular phone will be described as an example. 1 and 2 are external perspective views of a front side and a back side of a camera-equipped mobile phone to which the present invention is applied. The main body 2 of the camera-equipped mobile phone 1 includes an upper housing 11 and a lower housing 12 and a hinge portion 13 that rotatably connects the housings 11 and 12.

  As shown in FIG. 2, a part of the photographing lens 14 is exposed on the upper casing 11, and the upper casing is used for the hinge portion 13 when the digital camera built in the camera-equipped mobile phone 1 is used. A click mechanism (not shown) is provided so that 11 and the lower housing 12 are locked at a predetermined angle. The main body unit 2 can be unfolded and folded by rotating the main unit 2 via the hinge unit 13. When the camera-equipped mobile phone 1 is not used, the upper case 11 can be expanded and folded. 11 and the lower housing 12 are folded so as to be parallel to each other.

  The casings 11 and 12 are both formed in a substantially rectangular thin plate shape, the photographing lens 14 is exposed from the back surface 11a of the upper casing 11, the LCD panel 26 and the reception speaker 27 are displayed on the front surface 11b, and the upper surface 11c. Is provided with an antenna 28, and an operation unit 31 and a transmission microphone 32 are disposed on the front surface 12 a of the lower housing 12. Further, the lower surface 12b of the lower housing 12 is provided with a socket 34 for connecting a cable to an external device such as a personal computer, and a memory card slot 36 into which a memory card is loaded.

  The antenna 28 receives a radio signal from another mobile phone or an Internet server when using a telephone call, e-mail service, or Internet connection service, and transmits a radio signal transmitted from the camera-equipped mobile phone 1 to the outside. . The receiving speaker 27 outputs the voice or ringtone of the communication partner. On the LCD panel 26, various information such as a menu screen and a telephone number of the called party, a through image obtained by the CCD, and a photographed image recorded on the memory card are displayed. The transmitting microphone 32 converts the voice of the speaker into an electric voice signal and transmits it to the other party via the antenna 28.

  The operation unit 31 includes a selection key 31a, a shutter button 31b, a dial key 31c, and the like. The selection key 31a is used for selecting / setting various menus. The camera-equipped cellular phone 1 can shoot a subject by selecting a shooting mode from various modes, and these modes are selected by operating the selection key 31a. The shutter button 31b is used for a release operation when photographing with a digital camera. Furthermore, the dial key 31c is operated when inputting a telephone number or an e-mail text.

  FIG. 3 is a cross-sectional view of the lens driving device 21 used in the digital camera. The lens driving device 21 includes an upper cover 40 and a lower cover 41, a stator 42, a lens holder 45, a first lens 48, a second lens 49, a third lens 50, a magnet 52 as a rotor, a rotating body 53, and the like. Has been.

  The stator 42 sandwiched between the upper cover 40 and the lower cover 41 is composed of two layers of coil parts, a first coil part 57 and a second coil part 58. Since the first coil unit 57 and the second coil unit 58 have the same configuration, the configuration of the first coil unit 57 will be described, and the configuration of the second coil unit 58 will be omitted.

  As shown in FIG. 4, the first coil portion 57 is formed by a wound coil 60 surrounded by an upper coil cover 61 and a lower coil cover 62, and has a cylindrical shape. Teeth 61a, 62a provided on the upper coil cover 61 and the lower coil cover 62 are arranged on the inner peripheral surface of the cylindrical first coil portion 57 so as to mesh with each other, and the teeth 61a, 62a are A total of 48 are provided. As shown in FIG. 4, the teeth 61a and 62a of the first coil portion 57 and the teeth 61a and 62a of the second coil portion 58 are arranged so as to be shifted by half of the teeth 61a and 62a. Further, as shown in the figure, a gap is provided between the teeth 61a and the teeth 62a.

  A pulse current is alternately supplied to the coils 60 of the first coil unit 57 and the second coil unit 58. For example, when the pulse current is supplied in the arrow direction A in the drawing as the forward direction, when the pulse current is supplied in the forward direction to the coil 60 of the first coil portion 57, the pulse current flows around the coil 60. A clockwise magnetic field is generated concentrically in the direction. Thereby, the magnetic field lines are guided from the upper coil cover 61 to the lower coil cover 62. At this time, the lines of magnetic force exit from the upper coll cover 61 into the gap (in the air) and enter the lower coil cover 62. As a result, the teeth 61a of the upper coil cover 61 become N poles, the teeth 62a of the lower coil cover 62 become S poles, and the teeth 61a, 62a provided alternately on the inner circumference of the cylindrical shape of the stator 42 have N poles. S pole magnetic fields are alternately formed. In addition, when a pulse current in the reverse direction is supplied to the coil 60, a magnetic field is generated around the coil 60, and the lines of magnetic force exit from the lower coil cover 62 into the gap (in the air) and enter the upper coil cover 61. Accordingly, the teeth 61a of the upper coil cover 61 are S poles, and the teeth 62a of the lower coil cover 62 are N poles. Therefore, magnetic fields of N and S poles are alternately formed on the teeth 61a and 62a provided on the cylindrical inner periphery of the stator 42.

  The outer shape of the magnet 52 has a cylindrical shape slightly smaller than the inner periphery of the stator 42, and the outer periphery is a permanent magnet in which N poles and S poles are alternately poled. The magnet 52 is formed into 48 poles. The magnet 52 rotates relative to the stator 42 by the repulsive force and attractive force of a magnetic field formed by supplying a pulse current to the stator 42. The magnet 52 rotates with one pole as one step, and makes one round in 48 steps. The stator 42 and the magnet 52 constitute a hollow stepping motor 64.

  For example, if the forward direction is that the magnet 52 rotates in the direction of the arrow A in the figure around the optical axis as in the case of the pulse current, when the magnet 52 is rotated in the forward direction, the forward direction of the first coil unit 57, The supply of the pulse current is repeated in the order of the forward direction of the second coil unit 58, the reverse direction of the first coil unit 57, and the reverse direction of the second coil unit 58. Thereby, for example, the order of the N poles formed on the teeth 61a and 62a is the order of the teeth 61a of the first coil portion 57, then the teeth 61a of the second coil portion 58, the teeth 62a of the first coil portion 57, and the second. It becomes the teeth 62a of the coil part 58. Therefore, since the south pole of the magnet 52 is attracted to the north pole formed on the teeth 61a and 62a of the first and second coil portions 57 and 58, the magnet 52 rotates in the forward direction.

  Further, when the magnet 52 is rotated in the reverse direction, the forward direction of the first coil part 57, the reverse direction of the second coil part 58, the reverse direction of the first coil part 57, and the forward direction of the second coil part 58 are in this order. Repeat the pulse current supply. Thereby, for example, the order of the N poles formed on the teeth 61a and 62a is the order of the teeth 61a of the first coil portion 57, then the teeth 62a of the second coil portion 58, the teeth 62a of the first coil portion 57, and the second. It becomes the teeth 61a of the coil part 58. Therefore, since the S pole of the magnet 52 is attracted to the N pole formed on the teeth 61a and 62a of the first and second coil portions 57 and 58, the magnet 52 rotates in the reverse direction. Note that the N pole formed on the teeth 61a and 62a has been described, but the same applies to the S pole.

  The rotating body 53 is bonded to the inside of the magnet 52 and rotates together with the magnet 52 in the forward direction or the reverse direction. A spiral groove 67 is provided on the inner surface of the rotating body 53, and the spiral groove 67 meshes with a spiral groove 68 provided on the outer surface of the lens holder 45.

  The lens holder 45 holds a first lens 48, a second lens 49, and a third lens 50 in order from the incident light incident side, and the photographing lens 14 is configured by the first to third lenses 48 to 50. Yes. A spiral groove 68 is provided on the outer peripheral surface of the lens holder 45 holding the second lens 49 and the third lens 50, and the upper surface is provided on the outer periphery of the lens holder 45 holding the first lens 48. A projecting portion 72 that is fitted into a rail portion 71 formed on the cover 40 is provided.

  The rail portion 71 and the protruding portion 72 constitute a rotation stopping mechanism that restricts the rotation of the lens holder 45. Accordingly, when the rotating body 53 rotates, the rotation of the lens holder 45 is restricted by the protruding portion 72 and the rail portion 71, so that the lens holder 45 moves along the rail portion 71 in the optical axis direction. Hereinafter, the movement of the lens holder 45 toward the subject along the optical axis direction is defined as the forward direction, and the movement of the lens holder 45 toward the CCD described later is defined as the backward direction.

  A holding unit 77 provided in the lower cover 41 holds a low-pass filter 78, and on the rear side thereof, a CCD 80, which is an imaging means attached to a circuit board, is arranged. The low-pal filter 78 removes high frequency components contained in the subject light. By using the low-pass filter 78, it is possible to reduce problems such as pseudo colors and moire. The subject light that has passed through the low-pass filter 78 is received by the CCD 80, and image data representing the subject is generated.

  Further, the lens driving device 21 detects the origin position of the photographic lens 14 in order to control the position of the photographic lens 14 when performing focusing. As shown in FIG. 5, the detection of the origin position of the photographic lens 14 is performed at predetermined intervals on the lower cover 41 so as to face the conductive washer 85 provided on the end face of the lens holder 45 and the washer 85. A pair of electrodes 86a and 86b provided, a capacitance detection unit 87 provided on a base (not shown), and an origin position determination unit 88 are included.

  The washer 85 has substantially the same shape as the end face of the lens holder 45 on the CCD 80 side, and is bonded so as not to cover the third lens 50. The pair of electrodes 86a and 86b are provided around the opening 41a (see FIG. 3) through which the subject light from the photographic lens 14 passes with a certain interval. The electrostatic capacitance detector 87 applies a predetermined voltage to the pair of electrodes 86a and 86b, and detects the electrostatic capacitance formed between the electrodes 86a and 86b and the washer 85. The origin position determination unit 88 determines whether or not the photographic lens 14 is disposed at the origin position based on the capacitance detected by the capacitance detection unit 87.

  FIG. 6 is a block diagram showing an electrical configuration of a digital camera using the lens driving device 21. The system controller 89 controls the entire lens driving device 21. The system controller 89 includes, for example, a microcomputer, and includes, in addition to the CPU, a ROM 89a that stores a control program, various setting data, and the like, and a RAM 89b that stores various data generated during control.

  An image signal output from the CCD 80 via the photographing lens 14 is input to the image processing circuit 90. The image processing circuit 90 converts an analog image signal into a digital image signal, and performs various correction processes such as brightness level correction and white balance correction, YC processing, compression processing, and the like on the image data.

  When a through image is displayed on the LCD panel 26 during shooting, various correction processes are performed on the image data whose image quality has been adjusted, and then a simple YC process is performed to convert the image data into YC image data composed of luminance data and color difference data. To do. The YC image data is read to the display circuit 92 via the image memory 91, converted into a composite signal such as NTSC, and input to the LCD panel 26.

  When photographing is performed, the image processing circuit 90 performs various correction processes on the image data, and then performs YC processing to generate YC image data. The YC image data is further subjected to a fixing process and a compression process, and is converted into, for example, a compressed image data in a jpeg format. The compressed image data is stored in a RAM 89b, which will be described later, and then recorded on a memory card 94, which is a storage medium, via a memory controller 93.

  The coil driver 95 controls the pulse current supplied to the first coil unit 57 and the second coil unit 58 based on the drive signal from the system controller 89. Thereby, the rotation direction and the rotation amount of the rotating body 53 are controlled, and the photographing lens 14 is moved in the optical axis direction.

  The electrostatic capacitance detection unit 87 applies a voltage to the electrodes 86 a and 86 b and detects the electrostatic capacitance formed between the electrodes 86 a and 86 b and the washer 85. When the lens holder 64 moves in the forward direction, the distance between the washer 85 and the electrodes 86a and 86b is increased, so that the capacitance detected by the capacitance detector 87 becomes small. Further, when the lens holder 64 moves in the backward direction, the distance between the washer 85 and the electrodes 86a and 86b approaches, so that the capacitance detected by the capacitance detection unit 87 increases. As described above, the detection result detected by the capacitance detection unit 87 is sent to the origin position determination unit 88.

  The origin position determination unit 88 determines whether or not the photographing lens 14 is at the origin position based on the change in capacitance detected from the capacitance detection unit 87. In the origin position determination unit 88, the capacitance detected when the photographing lens 14 is disposed at the origin position is stored in advance as a reference capacitance, and is sent from the capacitance detection unit 87. The capacitance and the stored reference capacitance are compared and determined. The origin position determination unit 88 determines that the photographing lens 14 is disposed at the origin position when the reference capacitance and the detected capacitance match, and transmits a signal to the system controller 89.

  The system controller 89 is provided with a counter 89 c that counts the number of pulse currents supplied to the first and second coils 57 and 58 by the coil driver 95. When the system controller 89 receives a signal from the origin position determination unit 88, the system controller 89 resets the counter 89c to “0”. The system controller 89 controls the position of the photographing lens 14 by outputting a drive signal to the coil driver 95 based on the count data of the counter 89c.

  The AF evaluation value calculation circuit 96 calculates an AF evaluation value based on the contrast of image data for one screen generated by the image processing circuit 90. The contrast of the image is the highest when the subject image is in focus, and the AF evaluation value is also highest at this time. The AF evaluation value calculation circuit 96 transmits an AF evaluation value signal corresponding to the AF evaluation value to the system controller 89. Based on the AF evaluation value signal, the system controller 89 controls the position of the photographic lens 14 to move the photographic lens 14 to the focus matching position.

  Next, photographing processing of the camera-equipped cellular phone 1 having the above-described configuration will be described with reference to flowcharts shown in FIGS. When shooting using the camera-equipped mobile phone 1, first, the main body 2 is moved from the folded state to the expanded state, and the selection key 31a is operated to select the shooting mode. When the shooting mode is selected, each part of the digital camera such as the CCD 80 is activated. At this time, the origin position detection operation of the photographic lens 14 is performed.

Next, the origin position detection operation will be described. The capacitance detector 87 detects the capacitance between the conductor 85 and the electrodes 86a and 86b. The detected capacitance is transmitted to the origin position determination unit 88. The origin position determination unit 88 compares and determines whether or not the reference capacitance stored in advance matches the detected capacitance. If it is determined that the reference capacitance and the detected capacitance match, it is determined that the photographic lens 14 is at the origin position as shown in FIG. 9A, and the counter 89c is also reset. As a result, the origin position detection operation ends.

  If the reference capacitance does not match the detected capacitance, the photographic lens 14 is moved backward. At this time, the system controller 89 repeatedly determines whether or not a signal transmitted from the origin position determination unit 88 is received when the photographing lens 14 reaches the origin position. The system controller 89 moves the photographing lens 14 backward until a signal from the origin position determination unit 88 is received. Then, when receiving a signal from the origin position determination unit 88, the system controller 89 stops the movement of the photographing lens 14, resets the counter 89c, and ends the origin position detection operation.

  When the origin position detection operation is completed, acquisition of a through image is started, and for this through image, the system controller 89 controls the coil driver 95 based on the acquired AF evaluation value signal and the count value of the counter 89c. The photographic lens 14 is moved to the focus matching position.

  When the shutter button 31b is half-pressed, as shown in FIG. 9B, the photographing lens 14 is focus-locked at the focus matching position. Further, when the shutter button 31b is not pressed or when the half-press is released, focus adjustment is continuously performed on the through image.

  Thereafter, when the shutter button 31b is fully pressed, the captured image data is converted into compressed image data and written to the memory card 94. When the photographing is completed, the origin position detecting operation of the photographing lens 14 is performed again. When the origin position is detected, a reset pulse is generated, the counter 89c is reset, focus adjustment of the through image is performed again, and imaging is continued. As described above, the electrostatic capacitance between the washer 85 and the electrodes 86a and 86b is detected, and the origin position of the photographing lens 14 is detected based on the change in the electrostatic capacitance. Therefore, the lens driving device 21 is downsized. This is very advantageous.

  In the present embodiment, a conductive washer 85 is provided on the end face of the lens holder 45 and the capacitance between the washer 85 and the electrodes 86a and 86b is detected. However, instead of the washer 85, the lens holder 45 The entire end surface may be plated. In addition, a hollow stepping motor is used to move the lens holder 45 in the optical axis direction. However, the lens holder 45 may be moved in the optical axis direction using a DC motor or a stepping motor.

  In the present embodiment, the origin position at the time of focusing with the photographic lens 14 is detected. However, the present invention is not limited to this, and the origin position at the time of zooming adjustment with the zoom lens may be detected.

It is a front side perspective view of the mobile phone with a camera. It is a back side perspective view of a mobile phone with a camera. It is sectional drawing which shows the structure of a lens drive device. It is principal part sectional drawing which shows the structure of a stator and a magnet. It is explanatory drawing which shows the outline | summary of a washer and an electrode. It is a block diagram which shows the electric constitution of a digital camera. It is a flowchart explaining an imaging process. It is a flowchart explaining an origin position detection operation. It is principal part sectional drawing explaining the origin position and focus lock position of a photographic lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mobile phone with a camera 14 Shooting lens 21 Lens drive device 31b Shutter button 42 Stator 45 Lens holder 52 Magnet 53 Rotating body 85 Washer 86a, 86b Electrode 87 Electrostatic capacitance detection part 88 Origin position determination part 89 System controller

Claims (2)

A stator that has a cylindrical shape and that forms a magnetic field within the cylindrical shape; and a cylindrical shape that is positioned within the cylindrical shape of the stator and coaxial with the cylindrical shape, and the stator is configured by the magnetic field formed by the stator A rotor that rotates relative to the cylindrical shape of the rotor, and a cylindrical lens holder that is positioned further inside the cylindrical shape of the rotor and holds a lens, and the lens holder is moved along the optical axis direction by the rotation of the rotor In the lens driving device to be moved,
A conductor provided on one end face of the lens holder, and a washer having the same shape as the end face of the lens holder ;
A pair of electrodes provided to face the washer when the lens holder moves to one end position of the moving range;
A capacitance detecting means connected to the electrode and detecting a capacitance formed between the electrode and the washer ;
A lens driving device comprising: determination means for determining that the lens holder is at an origin position based on a change in capacitance detected by the capacitance detection means. 1 SL and mounting the lens driving device according to claim, imaging means for obtaining image data by imaging an object image formed by the lens, and a storage means for storing the image data captured by the image pickup means Digital camera characterized by having.

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