JP2006072053A - Lens drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive lens drive device capable of driving a lens with high accuracy. <P>SOLUTION: A moving shaft 12 is provided with a mark for detecting a position. Grooves 120 where many marks are arrayed so that high position detecting accuracy is obtained are formed on the moving shaft, and the projecting and recessed parts of the grooves where many marks are arrayed are detected by a sensor 131. The moving shaft 12 having the grooves 120 for detecting a position is inexpensively manufactured, and further a general-purpose sensor is used as the sensor 131, whereby both the moving shaft 12 and the sensor 131 realize the drastic reduction of cost. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lens driving device that drives a lens.

  The most popular driving device for driving a lens is a motor. Recently, the number of mobile phones equipped with a camera has increased, so that a piezoelectric element has been spotlighted as a small actuator replacing the motor. When driving a lens using this piezoelectric element, the lens holding frame is engaged with the driving shaft by frictional force, and the driving shaft and the lens holding frame are moved relative to each other by expansion and contraction of the piezoelectric element. The lens holding frame is moved in the optical axis direction (see, for example, Patent Document 1).

  However, in the case of a mobile phone or the like, since the stroke is short, the above configuration may be used. However, if the above configuration is applied to a general digital camera as it is, the stroke must be lengthened, so that the drive shaft becomes too long and the piezoelectricity is increased. The linearity of the drive shaft including the element may not be obtained. If the linearity of the drive shaft cannot be obtained in this way, the lens is tilted or the position of the lens is shifted.

  Therefore, both ends of the drive shaft are supported movably, a friction generating member is disposed so as to surround the drive shaft, and a piezoelectric element is disposed adjacent to the friction generating member. Techniques have been proposed in which the lens is moved together with the drive shaft by relatively moving the generating member and the drive shaft (see Patent Documents 2 to 3).

  However, if the lens is moved together with the drive shaft by a long stroke by moving the drive shaft itself, a slightly longer line sensor or the like must be used as a sensor for detecting the position of the lens. However, when a line sensor or the like is used, there is a risk of increasing the size, and further, if the line sensor is used to detect the position of the lens, wiring or the like may be complicated.

  By the way, among those that move the moving body along the drive shaft, both the drive shaft and the moving body are used as constituent members of the sensor, without the need to provide a sensor such as a line sensor. Some attempt to detect the position of the body with high accuracy (see, for example, Patent Documents 4 and 5).

  In Patent Document 4, a variable resistor is formed using a conductive material for the drive shaft itself, and a movable contact in contact with the variable resistor is configured on the movable body side to detect the position on the movable body side with high accuracy. To do. Although this technique can be applied using this movable body as a lens holding frame, the accuracy required for a lens holding frame that requires fine detection accuracy may not be obtained depending on the resistance range of the variable resistor.

Moreover, in the thing of patent document 5, the voltage which generate | occur | produces in the magnetoresistive sensor near a magnetizing rod during the movement of a magnetizing rod using the magnetizing rod by which the N pole and the S pole were alternately arranged on the drive shaft. It is trying to detect the lens position accurately by detecting the AC change in the lens. If it does in this way, detection accuracy will become high, so that S pole and N pole are arranged finely. However, if the S and N poles are finely provided in this way, the magnetizing rod may be expensive. Magnetoresistive elements are relatively expensive.
JP-A-4-69070 JP-A-4-69071 JP 2002-233171 A JP 2000-205809 A JP-A-8-29660

  In view of the above circumstances, it is an object to provide a lens driving device that is inexpensive and can drive a lens with high accuracy.

The lens driving device of the present invention that achieves the above object is a lens driving device for driving a lens.
A lens holding frame for holding the driven lens;
A movement axis that extends in the optical axis direction of the driven lens and is provided with a movement detection mark and the lens holding frame is fixed and moved in the optical axis direction to move the lens holding frame in the optical axis direction;
A piezoelectric element that is arranged around the moving shaft, is supported at one end in a position-invariant manner, receives a drive signal, and expands and contracts to the other end side;
A friction generating member that is fixed to the other end of the piezoelectric element and that generates a friction between the moving shaft through the moving shaft;
A sensor for detecting the mark attached to the moving axis;
And a drive circuit that receives a detection signal from the sensor and applies a drive signal to the piezoelectric element so that the lens holding frame moves to a predetermined position.

  With this configuration, an inexpensive optical sensor, electromagnetic sensor, or the like can be used as the sensor, and the mark can be easily provided by painting or plating, thereby realizing an inexpensive lens driving device.

  Here, the moving shaft has a mark in which a plurality of grooves extending in the direction surrounding the moving shaft are arranged in the extending direction of the moving shaft as the mark, and the sensor detects the groove. It is preferable.

  With this configuration, it is relatively easy and inexpensive to manufacture the groove by machining or the like, so that the moving shaft can be manufactured at low cost.

  Further, the drive shaft may have a mark in which a number of lines extending in the direction surrounding the movement axis are arranged as the mark in the direction in which the movement axis extends, and the sensor may detect the line. good.

   As described above, a lens driving device that is inexpensive and can drive a lens with high accuracy is provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a lens driving apparatus according to an embodiment of the present invention.

  A lens driving device 1 shown in FIG. 1 includes a lens holding frame 11 that holds a driven lens 10. The driven lens 10 extends in the optical axis direction and is provided with a movement detection mark 120 so that the lens holding frame 11 is fixed and moved in the optical axis direction to move the lens holding frame 11 in the optical axis direction. The shaft 12 is supported by a support member 13. A piezoelectric element 15 arranged around the moving shaft 12 and supported at one end by a support member 13 in a position-invariant manner, and expanded and contracted to the other end side upon application of a drive signal from the drive circuit 14, and at the other end of the piezoelectric element 15 Friction generating members 16 that are fixed and pass through the moving shaft 12 to generate friction with the moving shaft 12 are provided. A sensor 131 is disposed on the support member 13 side so as to detect the mark 120 provided on the moving shaft 12 so as to face the moving shaft 12. The drive circuit 14 for driving the piezoelectric element 15 receives a detection signal from the sensor 131 and gives a drive signal to the piezoelectric element 15 so that the lens holding frame 11 moves to a predetermined position. A guide shaft 17 is provided on the side facing the moving shaft 12, and a fork 18 provided on the lens holding frame 11 is engaged with the guide shaft 17.

  FIG. 2 is a diagram illustrating the configuration of the sensor 131 portion disposed on the support member 13 side.

  As shown in FIG. 2, the moving shaft 12 has a mark 120 in which a plurality of grooves 1200 extending in the direction surrounding the moving shaft are arranged in the extending direction of the moving shaft 12. A sensor 131 is provided so that the groove 1200 can be detected.

  When the moving shaft 12 is moving, the sensor 131 detects any one of the grooves 1200 arranged in the extending direction of the moving shaft 12 by the sensor, and the detection signal is supplied to the drive circuit 14. . The drive circuit 14 receives a detection signal from the sensor 131 and gives a drive signal to the piezoelectric element 15 so that the lens holding frame 11 moves to a predetermined position.

  Here, it is assumed that the position before the driving circuit 14 drives the driven lens 10 is assumed, and how much the driven lens 10 has moved from that position is based on the detection signal from the sensor 131. It is detected by counting the number of grooves by the counter inside. By making the intervals of the grooves 1200 arranged as many as possible, the lens holding frame 11 can be properly moved to a predetermined position together with the lens 10.

  It is relatively easy to provide grooves arranged in a large number. Instead of forming a drive shaft by forming a resistance film on the surface as in the past, the N and S poles are magnetized and attached. It is possible to manufacture at a much lower cost than manufacturing a magnetic rod.

  As described above, a lens driving device that is inexpensive and can drive a lens with high accuracy is realized.

  FIG. 3 is a diagram illustrating an example in which different colors are alternately arranged as marks instead of providing a large number of grooves as marks.

  As shown in FIG. 3, the same effect can be obtained by providing marks of different colors 1201 alternately by plating or painting instead of providing the grooves 1200. At this time, for example, a white color having a high reflectance may be used as a different color, or a black color having a low reflectance may be used.

  FIG. 4 is a diagram showing an example in which a thin line is given.

  As shown in FIG. 4, thin lines 1202 may be provided at equal intervals instead of providing marks of different colors alternately as shown in FIG. 3 by plating or painting.

  As described above, a lens driving device that is inexpensive and can drive a lens with high accuracy is realized.

  Finally, an example in which the lens driving device is applied to an imaging device will be described.

  FIG. 5 is an external perspective view showing an external appearance of a camera 1a to which the lens driving device of FIG. 1 is applied.

  The camera 1a includes a photographic optical system and an image sensor, and generates an image signal representing a subject image formed on the image sensor via the photographic optical system.

  A lens barrel 10a is provided at the center of the camera body shown in FIG. 5, and a finder 11a is provided above the lens barrel 10a. While looking through the viewfinder 11a or visually recognizing a subject captured by the photographing optical system in the lens barrel 10a on a display screen (not shown) on the back side, a release button on the upper surface of the camera body 1a is used for a photo opportunity. The camera 13a is operated to take a picture. The release button 13a has two operation modes of half-pressing and full-pressing. When the half-pressing operation is performed, the TTL distance measurement is performed in the camera 1. Shooting is performed with focus according to the subject distance obtained by distance measurement. If the light metering part inside the camera detects that the brightness of the object field is insufficient when this photographing is performed, the flash light is emitted from the flash light emission window 12a provided next to the finder 11a, and the light amount necessary for photographing. Is given to the subject and shooting is performed.

  6 is a block diagram showing the internal configuration of the camera 1 shown in FIG.

  The camera 1a includes a TTL distance measuring unit that measures a subject distance using a focus lens 10 in a photographing optical system. In this embodiment, the focus lens 10 and an image sensor (here, a CCD solid-state image sensor is used). Since it is used, the TTL distance measuring unit is composed of 110a, A / D unit 120a, and signal processing block 130a. The lens driving device shown in FIG. 1 is applied to the portion that drives the focus lens 10.

  In the signal processing block 130a, signal processing such as white balance adjustment and YC separation is also performed.

  In this example, the signal processing block 130a, the JPEG encoder 160a, and the card I / F 170a are configured by a DSP, and the DSP is controlled by the CPU 100a. The CPU 100a controls the operation of the photographing apparatus according to the procedure of the program recorded in the ROM 1001a. When an operation signal for the release button 13 in the key block 103a is input to the CPU 100a, for example, Processing corresponding to the release operation signal is notified to the DSP, and the signal processing block 130a and the card I / F 170a in the DSP perform necessary processing.

  First, the operation of the photographing apparatus 1a when the power switch in the key block 130a is turned on will be described.

  When the power switch is turned on, power is supplied from the battery to the CCD 110a, A / D 120a, etc. shown in FIG. When power is supplied to the CCD 110a, a subject in a direction in which the photographing lens including the focus lens 10 is directed is imaged on the CCD 110a. At this time, the CPU 100a gives an instruction to output image data representing the subject imaged on the CCD 110a through the TG 1101a at every predetermined time, causes the CCD 110a to output the image data, and further the A / D 120a. Then, the image data is supplied to the signal processing block 130a at every predetermined time. At the same time, an instruction is issued from the CPU 100 to the drive circuit 14, the piezoelectric element 15 is driven, and the focus lens 10 is moved along the optical axis.

  The signal processing block 130a detects the contrast based on the image signal supplied from the CCD 110a for each position in the middle of the movement of the focus lens 10, and calculates an AF evaluation value from the contrast. Then, processing for setting the peak of the AF evaluation value to the in-focus position is performed. By detecting the in-focus position in this signal processing block, the CPU 100 constantly moves the focus lens 10 to the in-focus position, so that a focused subject is always imaged on the CCD 110a. Image data representing the subject imaged on the CCD 110a is output to the signal processing block 130a via the A / D 121a, and image processing such as YC separation is performed on the image data supplied from the CCD 110a by the signal processing block 130a. The image processed image data is output to the DRAM 140a at every predetermined time, and the image data at every predetermined time is stored in the DRAM 140a one after another. The image data stored in the DRAM 140a is supplied to the image display unit 150a at every predetermined time, and the image display unit 150a switches the subject based on the image data supplied at the predetermined time and sequentially displays them on the display screen. To do. In this way, the subject captured by the photographing lens is displayed on the display screen of the image display unit.

  When the release button 13a is pressed at a photo opportunity while viewing the subject displayed on the display screen, a signal for performing exposure for a predetermined time from the timing when the release button 13a is pressed is supplied from the TG 1101a to the CCD 110a. Is done. After the predetermined time has passed and the exposure is completed, image data is output from the CCD 110a. The output image data is supplied to the signal processing block 130a via the A / D 120a, and the image data processed by the signal processing block 130a is further supplied to the JPEG encoder 160a. The image data is compressed by the JPEG encoder 160a, and an image file composed of the compressed image data and information related to the compression is recorded on the memory card 180a under the control of the card I / F 170a.

  In this way, when the lens driving device of FIG. 1 is applied to the photographing apparatus of FIG. 5, the space required for arranging the motor up to now is not required, and the photographing apparatus shown in FIG. 5 can be miniaturized.

It is a figure which shows the lens drive device which is embodiment of this invention. It is the figure which showed the structure of the sensor part arrange | positioned at the support member 13 side. It is a figure which shows the example where it replaced with providing many groove | channels as a mark, and the different color was alternately arranged as a mark. It is a figure which shows the example which gave the thin line. It is a figure which shows the external appearance of the imaging device to which the lens drive device of FIG. 1 is applied. FIG. 6 is a block diagram illustrating an internal configuration of the photographing apparatus in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens drive device 10 Lens 11 Lens holding frame 12 Moving shaft 120 Mark 1200 Groove 1201 Colored plating or colored coating 1202 Colored plating or colored coating different from 1201 1203 Fine wire 13 Support member 131 Sensor 14 Drive circuit 15 Piezoelectric element 16 Generating member 17 Guide shaft 18 Fork

Claims (3)

In a lens driving device that drives a lens,
A lens holding frame for holding the driven lens;
A movement axis that extends in the optical axis direction of the driven lens and is provided with a movement detection mark and the lens holding frame is fixed and moved in the optical axis direction to move the lens holding frame in the optical axis direction;
A piezoelectric element that is arranged around the moving shaft and is supported at one end in a position-invariant manner and receives a drive signal to expand and contract to the other end;
A friction generating member that is fixed to the other end of the piezoelectric element and through which the moving shaft passes and generates friction between the moving shaft;
A sensor for detecting the mark attached to the moving axis;
A lens driving device comprising: a driving circuit that receives a detection signal from the sensor and applies a driving signal to the piezoelectric element so that the lens holding frame moves to a predetermined position.   The moving shaft has, as the mark, a mark in which a plurality of grooves extending in a direction surrounding the moving shaft are arranged in the extending direction of the moving shaft, and the sensor is a sensor that detects the groove. The lens driving device according to claim 1.   The drive shaft has, as the mark, a mark in which a plurality of lines extending in a direction surrounding the moving shaft are arranged in the extending direction of the moving shaft, and the sensor is a sensor that detects the line. The lens driving device according to claim 1.

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