Patent Publication Number: US-2011051243-A1

Title: Prism type lens structure

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a prism type lens structure, particularly to a prism type lens structure with vibration reduction capability. 
     2. Description of the Prior Art 
     The image capturing devices, such as the mobile phones and the PDA with image capturing capability, the digital cameras and so on, are now becoming popular and have brought a lot of convenience to people. A prism type lens structure includes a lens set concealed within the case of the image capturing device and a total reflection prism used to deflect the incident light by 90° to make the incident light in a direction along the optical axis of the lens set and guide the incident light into the lens set, wherein the focal distance of the lens set is adjusted by moving the lens set up or down. In this design of the prism type lens structure, because the lens set is not protruded out of the case of the image capturing device, the size and the thickness of the image capturing devices may be substantially decreased to have the advantages of more compact appearance and better portability. 
     However, the image capturing devices with prism type lens structure are very sensitive to the vibration. During capturing the pictures, the vibration caused by hand-shake will cause the movement of the light signals on the image sensor element after passing through the camera lens, so as to result in blur images. One of the common methods for vibration reduction includes adopting a compensational lens set specialized for vibration reduction in the camera lens, and adjusting the position and angle of the compensational lens set according to the direction and the degree of the vibration, so as to maintain a steady optical path. However, this method for vibration reduction requires the specialized compensational lens set and results in an increase in size and weight of the image capturing devices and disadvantage for compact design trend. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to provide a prism type lens structure that may control the deflection angle of the total reflection prism by adopting piezoelectric elements that may be controlled in their deformation with voltage variation to compensate the unstable optical path caused by hand shake. Therefore, the light signals may steadily transmit to the image sensor element to achieve the purpose of the vibration reduction. 
     According to an embodiment, a prism type lens structure comprises an optical lens set comprising at least one lens configured along an optical axis; an image sensor element configured below the optical lens set; a reflective element movably configured above the optical lens set for guiding a light signal along the optical axis of the optical lens set to image on the image sensor element; and a vibration reduction device comprising at least three piezoelectric elements distributively mounted to the reflective element; and a control mechanism electrically connected to the piezoelectric elements for detecting a vibration and applying a corresponding voltage to the piezoelectric elements for controlling a deflection angle of the reflective element. 
     Other advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the accompanying advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram illustrating a prism type lens structure according to one embodiment of the present invention; 
         FIG. 2  is a schematic diagram illustrating a prism type lens structure with four sets of piezoelectric elements configured on a total reflection prism according to one embodiment of the present invention; and 
         FIG. 3  is a schematic diagram illustrating a prism type lens structure in practice according to one embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a schematic diagram illustrating a prism type lens structure according to an embodiment of the present invention. A prism type lens structure may be applied in stand-alone digital cameras or the camera modules in other electronics, e.g. the mobile phones. In this embodiment, the prism type lens structure  10  includes an optical lens set  12 , an image sensor element  14 , a reflective element, and a vibration reduction device. In this embodiment, the reflective element is a total reflection prism  16 ; the vibration reduction device includes a plurality of the piezoelectric elements  18  (including  18 A and  18 B) and a control mechanism (not illustrated). 
     In one embodiment, the optical lens set  12  includes two sets of the lenses  121 ,  121 ′ configured along an optical axis  13 . The image sensor element  14 , e.g. a CMOS or a CCD image sensor, is configured below the optical lens set  12  along the optical axis  13  of the optical lens set  12 . The total reflection prism  16  is movably configured above the optical lens set  12 , and an included angle of 45° is between a reflection mirror  161  of the total reflection prism  16  and the optical axis  13  of the optical lens set  12  for receiving the light and guiding the light in the direction of the optical axis  13  of the optical lens set  12 . 
     A plurality of the piezoelectric elements  18  are mounted to the total reflection prism  16 . In this embodiment, a plurality of the piezoelectric elements  18  are configured at an outer surface of the reflection mirror  161  of the total reflection prism  16 , wherein the inner surface of the reflection mirror  161  is a reflective surface, and the reflection mirror  161  presents a tetragonal shape, as illustrated in  FIG. 2 . In this embodiment, four sets of the piezoelectric elements  18  are respectively configured at each corner of the outer surface of the tetragonal reflection mirror  161  and electrically connected to the control mechanism. The control mechanism may detect the horizontal and/or the vertical vibration of the camera and applying corresponding voltage to at least portions of the piezoelectric elements  18 . The shapes of the piezoelectric elements  18  are deformed due to the converse piezoelectric effect to propel the total reflection prism  16  with controlled deflection angle. 
     In this embodiment, these four sets of the piezoelectric elements  18  are respectively denominated as  18 A,  18 B,  18 C,  18 D, where the piezoelectric elements  18 A,  18 C and the piezoelectric elements  18 B,  18 D are respectively arranged in horizontal directions; the piezoelectric elements  18 A,  18 B and the piezoelectric elements  18 C,  18 D are respectively arranged in vertical directions. In the case of normal status, i.e. without vibration present, the piezoelectric elements  18 A,  18 B,  18 C,  18 D remain their original shapes, where  FIG. 1  illustrates the piezoelectric elements  18 A,  18 B only. A light signal  20  enters the total reflection prism  16  through an objective lens  22 , and deflected 90° by the total reflection prism  16  into the optical lens set  12  and then focused on the image sensor element  14  through an adjustment of the optical lens set  12 . 
     When the camera is vibrated vertically due to the hand shake, the image on the image sensor element  14  would vibrate vertically as well, and the control mechanism turns on one set of the piezoelectric elements including the piezoelectric elements  18 A,  18 C, and the other set of the piezoelectric elements including the piezoelectric element  18 B,  18 D. As illustrated in  FIG. 3 , the piezoelectric elements  18 A,  18 C are elongated while the piezoelectric elements  18 B,  18 D remain still or are slightly prolonged. As illustrated, the piezoelectric elements  18 A,  18 C are elongated more than the piezoelectric elements  18 B,  18 D. For simplification and clarification, this embodiment exemplifies vertical vibration only and illustrates the piezoelectric elements  18 A,  18 B; however, the piezoelectric elements  18 C and the piezoelectric elements  18 D would respectively actuate corresponding to the piezoelectric elements  18 A and the piezoelectric elements  18 B. In this embodiment, the combined deformation of these piezoelectric elements  18 A,  18 B,  18 C,  18 D results in an inclination angle θ of the total reflection prism  16 . The inclination angle θ in this way compensates the optical path shift caused by the vibration, so that the light may steadily travels along the optical axis  13  of the optical lens set  12  and may steadily image on the image sensor element  14 . Likewise, when the camera is vibrated horizontally due to the hand shake, the control mechanism turns on one set of the piezoelectric elements including the piezoelectric elements  18 A,  18 B, and the other set of the piezoelectric elements including the piezoelectric element  18 C,  18 D to control the rotation angle of the total reflection prism  16  so that the light may steadily image on the image sensor element  14 . The control mechanism may be used for detecting vertical and horizontal vibration and applying corresponding voltage to the piezoelectric elements  18 A,  18 B,  18 C,  18 D for compensating any shift in deflection angle, including the inclination angle or the rotation angle, so that the total vibration reduction may thus be achieved. 
     Here, the piezoelectric elements may be made of the piezoelectric ceramics and have no limitation in quantity. For example, there may be three or more piezoelectric elements. The control mechanism may adjust the weighted voltage based on the material and quantity of the piezoelectric elements and apply the appropriate voltage to the piezoelectric elements, so as to completely control the inclination angle and the rotation angle of the reflective element. 
     In addition, due to the nature of total light reflection, the optical path is deflected by an angle, and the angle is twice as the deflection angle of the total reflection prism; i.e. there is more shift in the image on the image sensor element. Therefore, the vibration reduction device of the present invention may adjust image position more by adjusting the deflection angle of the total reflection prism less. 
     To sum up, the present invention may control the deflection angle of the reflective element by adopting the piezoelectric elements that may be controlled in their deformation with voltage variation, to compensate the unstable optical path caused by hand shake. Therefore, the light signals may steadily transmit to the image sensor element to achieve the purpose of the vibration reduction. 
     While the invention is susceptible to various modifications and alternative forms, a specific example thereof has been shown in the drawings and is herein described in detail. It should be understood, however, that the invention is not to be limited to the particular form disclosed, but to the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the appended claims.