The present invention relates to a compact auto focus lens module with a piezoelectric actuator, especially to an auto focus lens module in which movement of an optical lens set is controlled by displacement and friction produced by deformation of the piezoelectric actuator for focusing.
Digital cameras or mobile phone cameras include a lens module that drives optical lens set moving along an optical axis so as to achieve autofocusing and/or zoom in/zoom out. One of the movement ways of the optical lens set is by Voice coil motor (VCM). After a current being applied to a coil, a driving force is generated in an electromagnetic field created by a permanent magnet so as to drive the optical lens set moving along the optical axis. Such design can reduce volume of lens modules so that it has been applied to mini-sized cameras, camera-equipped cellular phone or web-cameras broadly, as shown in US2008/0013196, U.S. Pat. No. 6,594,450, U.S. Pat. No. 7,145,738, TW M317027, JP3124292, JP3132575 and so on.
Ultrasonic motor (USM) is a type of electric motor formed from the ultrasonic vibration of piezoelectric material that is deformed while being applied with voltage. Then by design of a friction drive, the ultrasonic motor moves in a rotational or straight way, as prior arts disclosed in US2009/0153987, US2008/0297923, US2008/0174889 etc. Refer to
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In order to make the lens module move stably without tilting, devices disclosed in US2008/0144201, JP2004020935, etc. includes a guide rod arranged between the lens barrel and a housing of the lens module so as to stabilize the lens barrel. In US2007/0153404, a rail is used Refer to TW I265357, two sets of piezoelectric actuators are arranged on edges of the lens barrel so as to make the movement thereof become stable. However, conventional ultrasonic motors for movement of the lens barrel have shortcomings of complicated structure, high cost or large volume in designs of the guiding rod or friction generation so that they are difficult to be applied to compact auto focus lens modules. Thus there is a need to develop a driving member with high reliable and high stable structure that replaces conventional ways of generating friction. Moreover, requirements of simple structure, high precision, fast focus and reduced tilting need to be satisfied.
Therefore it is a primary object of the present invention to provide a compact auto focus lens module with a piezoelectric actuator having a piezoelectric actuator, a lens module and a frame. The piezoelectric actuator and the lens module are mounted in the frame. The lens module consists of a lens barrel fixed with an optical lens set therein, an elastic element and at least two guiding fixtures. The elastic element arranged between the lens barrel and the piezoelectric actuator includes an elastic member and a metal member. By the elastic force of the elastic element, a friction is generated on an interface between the elastic element and the piezoelectric actuator. The guiding fixture is formed by a guiding slot and a guide pin, corresponding to each other. The guiding slot is disposed on the lens barrel. The lens module slides under the guidance of the guide pin and being fixed in the frame. While being applied with a voltage, the lens barrel is driven by the piezoelectric actuator to move along the optical axis in the frame for focusing.
It is another object of the present invention to provide a compact auto focus lens module with a piezoelectric actuator with broader applications in which the elastic member is a coil spring so as to make the lens module have more applications. For further minimization of the volume, the elastic member can be an elastic pad made from elastic foam material or rubber. The elastic member can also be a leaf spring.
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The lens module 11 consists of a lens barrel 21, an optical lens set 22, an elastic element 30 and two guiding fixtures 23, 23′. The optical lens set 22 is fixed in the lens barrel 21 and having at least one optical lens for concentrating light on an image sensor (not shown in figure). For the auto focus lens module 11, the lens barrel 21 moves along an optical axis and the optical lens set 22 also move along with the movement of the lens barrel 21 so that the distance between the optical lens set 22 and the image sensor varies to have different imaging effects. However, the lens barrel 21 needs stability, without tilt for optimal imaging effects. This embodiment includes two guiding fixtures 23, 23′, respectively having corresponding guiding slots 211/211′ and guide pins 35/35′. The guiding slots 211/211′ are arranged at the lens barrel 21. By the guide pins 35/35′ that connects the guiding slots 211/211′ of the lens barrel 21 with a fixing ring 121 of the frame 12, the lens barrel 22 is set movably in the frame 12. Thus the lens module 11 can move vertically along the guide pins 35/35′ in the frame 12.
The elastic element 30 is disposed between the lens barrel 21 and the piezoelectric actuator 31. By such arrangement, the auto focus lens module 1 becomes more compact and the shortcoming of conventional lens module with larger volume caused by plate springs around the lens barrel. In the embodiment, the elastic element 30 is formed by an elastic member and a metal member 33. The elastic member 32 can be a pad made from elastic rubber or foam material that generates an elastic force. As shown in
Compared with conventional lens modules, the above design makes the lens module 11 moves stably and rapidly while the tilting of the lens module 11 is reduced. Moreover, the auto focus lens module 1 is minimized so as to be used in miniature optical systems.
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Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, and representative devices shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
Number | Date | Country | Kind |
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098213834 | Jul 2009 | TW | national |