Patent Publication Number: US-11378795-B2

Title: Lens curvature variation apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. national stage application of International Patent Application No. PCT/KR2018/008210, filed Jul. 20, 2018, which claims the benefit under 35 U.S.C. § 119 of Korean Application No. 10-2017-0168517, filed Dec. 8, 2017, the disclosures of each of which are incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to a lens curvature variation apparatus, and more particularly, to a lens curvature variation apparatus capable of quickly and accurately sensing the curvature of a lens. 
     BACKGROUND ART 
     A lens is a device that diverts a path of light. Lenses are used in a variety of electronic devices, especially in cameras. 
     Light passing through a lens in a camera is converted into an electrical signal through an image sensor, and an image can be acquired based on the electrical signal obtained through conversion. 
     In order to adjust the focus of an image to capture, it is necessary to vary the position of the lens. However, when the camera is employed in a small electronic device, a considerable space needs to be secured to vary the position of the lens, which results in inconvenience. 
     Accordingly, an approach for adjusting the focus of an image to capture without varying the position of the lens is being studied. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a lens curvature variation apparatus capable of quickly and accurately sensing the curvature of a lens. 
     It is another object of the present invention to provide a lens curvature variation apparatus capable of quickly and accurately varying the curvature of a lens. 
     Solution to Problem 
     In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a lens curvature variation apparatus for varying a curvature of a liquid lens based on an applied electrical signal, the lens curvature variation apparatus including a lens driver to apply the electrical signal to the liquid lens, a sensor unit to sense the curvature of the liquid lens formed based on the electrical signal, and a controller to control the lens driver to form a target curvature of the liquid lens based on the sensed curvature, wherein the sensor unit senses a size of an area of a boundary region between an insulator on an electrode and an electroconductive aqueous solution in the liquid lens or a change in the size. 
     Advantageous Effects of Invention 
     As is apparent from the above description, A lens curvature variation apparatus according to an embodiment of the present invention is configured to vary the curvature of a liquid lens which is variable based on an applied electrical signal, and includes a lens driver to apply an electrical signal to a liquid lens, a sensor unit to sense the curvature of the liquid lens formed based on the electrical signal, and a controller to control the lens driver to form a target curvature of the liquid lens based on the sensed curvature. The sensor unit may quickly and accurately sense the curvature of the lens by sensing the size of the area of the boundary region between an insulator on an electrode and an electroconductive aqueous solution in the liquid lens or a change in the size. 
     In particular, the curvature of the lens may be accurately detected by sensing a capacitance corresponding to the size of the area of the boundary region between the insulator on the electrode and the electroconductive aqueous solution in the liquid lens or a change in the size. 
     The sensor unit may sense the capacitance corresponding to the size of the area of the boundary region between the insulator on the electrode and the electroconductive aqueous solution in the liquid lens or a or change in the size, and feed back the capacitance to apply an electrical signal to the liquid lens such that the curvature of the lens is varied. Thereby, the curvature of the lens may be varied quickly and accurately. 
     The lens curvature variation apparatus may include a plurality of conductive lines for supplying a plurality of electrical signals output from the lens driver to the liquid lens, and a switching element disposed between one of the plurality of conductive lines and the sensor unit, and the sensor unit may sense the size of the area of the boundary region between the insulator on the electrode and the electroconductive aqueous solution in the liquid lens or a or change in the size during an ON period of the switching element. Thereby, the curvature of the lens may be sensed quickly and accurately. 
     The lens curvature variation apparatus may include an equalizer to calculate a curvature error based on the calculated curvature and the target curvature, and a pulse width variation controller to generate and output a pulse width variation signal based on the calculated curvature error. Thereby, the curvature of the lens may be sensed quickly and accurately. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a cross-sectional view of the camera according to an embodiment of the present invention; 
         FIG. 1B  is an internal block diagram of the camera of  FIG. 1A ; 
         FIG. 2  is a view illustrating a lens driving method; 
         FIGS. 3A and 3B  are views illustrating a method of driving a liquid lens; 
         FIGS. 4A to 4C  are views showing the structure of a liquid lens; 
         FIGS. 5A to 5E  are views illustrating variation of the lens curvature of a liquid lens; 
         FIG. 6  is an exemplary internal block diagram of a camera related to the present invention; 
         FIG. 7  is an exemplary internal block diagram of a camera according to an embodiment of the present invention; 
         FIG. 8A  shows curvature change curves of the liquid lens in the liquid curvature variation apparatus of  FIG. 6  and the lens curvature variation apparatus of  FIG. 7 ;  FIG. 8B  illustrates a timing chart for the common electrode, the first electrode, and the switching element in the lens curvature variation apparatus of  FIG. 7 ; 
         FIG. 9A  illustrates a sensor unit capable of sensing a capacitance without applying a separate additional pulse signal;  FIG. 9B  illustrates a sensor unit capable of applying a separate additional pulse signal to the common electrode and sensing the capacitance during application of the additional pulse signal; 
         FIG. 10  shows an exemplary internal circuit diagram of the lens driver of  FIG. 9A  or  FIG. 9B ; 
         FIG. 11A  is an exemplary waveform diagram for explaining the operation of the lens driver of  FIG. 10 ;  FIG. 11B  is an exemplary diagram for explaining the operation of the sensor unit of  FIG. 9A ;  FIG. 11C  is an exemplary waveform diagram illustrating the operation of the lens driver of  FIG. 10 ;  FIG. 11D  is a diagram illustrating the operation of the sensor unit of  FIG. 9A ; 
         FIG. 12A  is an exemplary waveform diagram illustrating the operation of the lens driver of  FIG. 10 ; and  FIG. 12B  is a diagram illustrating the operation of the sensor unit of  FIG. 9B ; 
         FIG. 13A  is an exemplary internal block diagram of a camera according to another embodiment of the present invention; 
         FIG. 13B  is an exemplary internal block diagram of a camera according to yet another embodiment of the present invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     As used herein, the suffixes “module” and “unit” are added or used interchangeably to facilitate preparation of this specification and are not intended to suggest distinct meanings or functions. Accordingly, the terms “module” and “unit” may be used interchangeably. 
       FIG. 1A  is a cross-sectional view of the camera according to an embodiment of the present invention. 
     First,  FIG. 1A  is an example of a cross-sectional view of the camera  195 . 
     The camera  195  may include aperture  194 , lens  193  and image sensor  820 . 
     The aperture  194  may obstruct or allow light incident on the lens  193 . 
     The image sensor  820  may include an RGB filter  910  and sensor array  911  to convert an optical signal into an electrical signal to sense RGB colors. 
     Accordingly, the image sensor  820  may sense and output RGB image. 
       FIG. 1B  is an internal block diagram of the camera of  FIG. 1A . 
     Referring to  FIG. 1B , the camera  195  may include lens  193  and image sensor  820 , and an image processor  830 . 
     The image processor  830  may generate an RGB image based on the electrical signal from the image sensor  820 . 
     The exposure time may be adjusted based on the electrical signals from the image sensor  820 . 
       FIG. 2  is a view illustrating a lens driving method. 
       FIG. 2( a )  illustrates that light from the focus point  401  is transmitted to the lens  403 , the beam splitter  405 , the microlens  407 , and the image sensor  409 , and thus an image PH having a size Fa is formed on the image sensor  409 . 
     Particularly,  FIG. 2( a )  illustrates that the focus is correctly formed in correspondence with the focus point  401 . 
     Next,  FIG. 2( b )  illustrates that the lens  403  is shifted toward the focus point  401 , as compared to  FIG. 2A , and an image PH having a size Fb less than Fa is focused on the image sensor  409 . 
     Particularly,  FIG. 2( b )  illustrates that the focus is formed excessively ahead in correspondence with the focus point  401 . 
     Next,  FIG. 2( c )  illustrates that the lens  403  is shifted away from the focus point  401 , and thus an image PH having a size Fc greater than Fa is focused on the image sensor  409 . 
     Particularly,  FIG. 2( c )  illustrates that the focus is formed excessively behind in correspondence with the focus point  401 . 
     That is,  FIG. 2  illustrates varying the position of the lens to adjust the focus of a captured image. 
     As shown in  FIG. 2 , a voice coil motor (VCM) is used to vary the position of the lens  403 . 
     However, the VCM requires a considerable space for movement of the lens when it is used in a small electronic device such as the mobile terminal of  FIGS. 1A-1B . 
     In the case of the camera  195  used in the mobile terminal, an optical image stabilization (OIS) function is required in addition to autofocusing. 
     Since the VCM allows only one-dimensional movement in a direction such as the left-right direction as shown in  FIG. 2 , it is not suitable to stabilize the image. 
     In order to address this issue, the present invention uses a liquid lens driving system instead of the VCM system. 
     In the liquid lens driving system, the curvature of the liquid lens is varied by applying an electrical signal to the liquid lens, and therefore the lens need not be shifted for autofocusing. In addition, in implementing the image stabilization function, the liquid lens driving system may inhibit blurring in two dimensions or three dimensions. 
       FIGS. 3A and 3B  are views illustrating a method of driving a liquid lens. 
     First,  FIG. 3A (a) illustrates that a first voltage V 1  is applied to a liquid lens  500 , and the liquid lens operates as a concave lens. 
     Next,  FIG. 3A (b) illustrates that the liquid lens  500  does not change the travel direction of light as a second voltage V 2 , which is greater than the first voltage V 1 , is applied to the liquid lens  500 . 
     Next,  FIG. 3A (c) illustrates that the liquid lens  500  operates as a convex lens as a third voltage V 3 , which is greater than the second voltage V 2 , is applied to the liquid lens  500 . 
     While it is illustrated in  FIG. 3A  that the curvature or diopter of the liquid lens changes according to the level of the applied voltage, embodiments of the present invention are not limited thereto. The curvature or diopter of the liquid lens may be varied according to a pulse width of an applied pulse. 
     Next,  FIG. 3B (a) illustrates that the liquid in the liquid lens  500  has the same curvature and operates as a convex lens. 
     Referring to  FIG. 3B (a), incident light Lpaa is converged, and corresponding output light Lpab is output. 
     Next,  FIG. 3B (b) illustrates that the traveling light is diverted upward as the liquid in the liquid lens  500  has an asymmetric curved surface. 
     Referring to  FIG. 3B (b), the incident light Lpaa is converged upward, and the corresponding output light Lpac is output. 
       FIGS. 4A to 4C  are views showing the structure of a liquid lens. Particularly,  FIG. 4A  is a top view of a liquid lens,  FIG. 4B  is a bottom view of the liquid lens, and  FIG. 4C  is a cross-sectional view taken along line I-I′ in  FIGS. 4A and 4C . 
     Particularly,  FIG. 4A  corresponds to the right side surface of the liquid lens  500  in  FIGS. 3A and 3B , and  FIG. 4B  corresponds to the left side surface of the liquid lens  500  in  FIGS. 3A and 3B . 
     Referring to the drawings, a common electrode (COM)  520  may be disposed on the liquid lens  500 , as shown in  FIG. 4A . The common electrode (COM)  520  may be arranged in a tubular shape, and the liquid  530  may be disposed in a region under the common electrode (COM)  520 , particularly, a region corresponding to the hollow. 
     Although not shown in the figures, an insulator (not shown) may be disposed between the common electrode (COM)  520  and the liquid to insulate the common electrode (COM). 
     As shown in  FIG. 4B , a plurality of electrodes (LA to LD)  540   a  to  540   d  may be disposed under the common electrode (COM)  520 , particularly under the liquid  530 . In particular, the plurality of electrodes (LA to LD)  540   a  to  540   d  may be arranged so as to surround the liquid  530 . 
     A plurality of insulators  550   a  to  550   d  for insulation may be disposed between the plurality of electrodes (LA to LD)  540   a  to  540   d  and the liquid  530 . 
     That is, the liquid lens  500  may include the common electrode (COM)  520 , the plurality of electrodes (LA to LD)  540   a  to  540   d  spaced apart from the common electrode (COM), and the liquid  530  and an electroconductive aqueous solution  595  (see  FIG. 4C ) disposed between the common electrode (COM)  520  and the plurality of electrodes (LA to LD)  540   a  to  540   d.    
     Referring to  FIG. 4C , the liquid lens  500  may include a plurality of electrodes (LA to LD)  540   a  to  540   d  on a first substrate  510 , a plurality of insulators  550   a  to  550   d  for insulation of the plurality of electrodes (LA to LD)  540   a  to  540   d , a liquid  530  on the plurality of electrodes (LA to LD)  540   a  to  540   d , an electroconductive aqueous solution  595  on the liquid  530 , a common electrode (COM)  520  spaced apart from the liquid  530 , and a second substrate  515  on the common electrode (COM)  520 . 
     The common electrode  520  may be formed in a tubular shape with a hollow. The liquid  530  and the electroconductive aqueous solution  595  may be disposed in the hollow region. The liquid  530  may be arranged in a circular shape, as shown in  FIGS. 4A and 4B . The liquid  530  may be a nonconductive liquid such as oil. 
     The size of the cross section of the hollow region may increase as it extends from the lower portion thereof to the upper portion thereof, and thus The lower portion of the plurality of electrodes (LA to LD)  540   a  to  540   d  may be larger than the upper portion of the plurality of electrodes (LA to LD)  540   a  to  540   d.    
     In  FIG. 4C , the first electrode (LA)  540   a  and the second electrode (LB)  540   b  among the plurality of electrodes (LA to LD)  540   a  to  540   d  are arranged to be inclined, and the lower portion thereof is large than the upper portion thereof. 
     As an alternative to the example of  FIGS. 4A to 4C , the plurality of electrodes (LA to LD)  540   a  to  540   d  may be arranged at an upper position, and the common electrode  520  may be arranged at a lower position. 
     While  FIGS. 4A to 4C  illustrates that four electrodes are provided, embodiments are not limited thereto. Two or more electrodes may be formed. 
     In  FIG. 4C , if a pulse-like electrical signal is applied to the first electrode (LA)  540   a  and the second electrode (LB)  540   b  a predetermined time after a pulse-like electrical signal is applied to the common electrode  520 , a potential difference is made between the common electrode  520 , the first electrode (LA)  540   a  and the second electrode (LB)  540   b . Then, the shape of the electroconductive aqueous solution  595  having electrical conductivity changes, and the shape of the liquid  530  in the liquid lens changes according to the change in shape of the electroconductive aqueous solution  595 . 
     The present invention provides a method of simply and quickly sensing the curvature of the liquid  530  formed according to electrical signals applied to the plurality of electrodes (LA to LD)  540   a  to  540   d  and the common electrode  520 . 
     According to the present invention, the sensor unit  962  senses the size of the area of the boundary region Ac 0  between the first insulator  550   a  on the first electrode  540   a  and the electroconductive aqueous solution  595  in the liquid lens  500  or a change in the size. 
     In  FIG. 4C , AM 0  is exemplarily given as the area of the boundary region Ac 0 . In particular, it is illustrated that the area of the boundary region Ac 0  that contacts the electroconductive aqueous solution  595  in the inclined portion of the first insulator  550   a  on the first electrode  540   a  is AM 0 . 
     In  FIG. 4C , it is illustrated that the liquid  530  is neither concave nor convex, but is parallel to the first substrate  510  and the like. The curvature given in this case may be defined as 0, for example. 
     As shown in  FIG. 4C , for the boundary region Ac 0  contacting the electroconductive aqueous solution  595  in the inclined portion of the first insulator  550   a  on the first electrode  540   a , the capacitance C may be formed according Equation 1. 
     
       
         
           
             
               
                 
                   C 
                   = 
                   
                     ɛ 
                     ⁢ 
                     
                       A 
                       d 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     Here, ε denotes the dielectric constant of a dielectric  550   a , A denotes the area of the boundary region Ac 0 , and d denotes the thickness of the first dielectric  550   a.    
     Here, when it is assumed that E and d have fixed values, the area of the boundary region Ac 0  may greatly affect the capacitance C. 
     That is, as the area of the boundary region Ac 0  increases, the capacitance C formed in the boundary region Ac 0  may increase. 
     In the present invention, since the area of the boundary region Ac 0  is varied as the curvature of the liquid  530  is varied, the area of the boundary region Ac 0  or the capacitance C formed in the boundary region Ac 0  is sensed using the sensor unit  962 . 
     The capacitance of  FIG. 4C  may be defined as CAc 0 . 
       FIGS. 5A to 5E  are views illustrating various curvatures of the liquid lens  500 . 
       FIG. 5A  illustrates a case where a first curvature Ria is given to the liquid  530  according to application of an electrical signal to the plurality of electrodes (LA to LD)  540   a  to  540   d  and the common electrode  520 . 
     In  FIG. 5A , it is illustrated that the area of the boundary region Aaa is AMa (&gt;AM 0 ) as the first curvature Ria is given to the liquid  530 . In particular, it is illustrated that the area of the boundary region Aaa contacting the electroconductive aqueous solution  595  in the inclined portion of the first insulator  550   a  on the first electrode  540   a  is AMa. 
     According to Equation 1, the area of the boundary region Aaa in  FIG. 5A  is larger than that of  FIG. 4C , and therefore the capacitance of the boundary region Aaa becomes larger. The capacitance of  FIG. 5A  may be defined as CAaa, which is greater than the capacitance CAc 0  of  FIG. 4C . 
     The first curvature Ria may be defined as having a value of positive polarity. For example, the first curvature Ria may be defined as having a level of +2. 
       FIG. 5B  illustrates a case where a second curvature Rib is formed in the liquid  530  according to application of an electrical signal to the plurality of electrodes (LA to LD)  540   a  to  540   d  and the common electrode  520 . 
     In  FIG. 5B , AMb (&gt;AMa) is exemplarily given as the area of the boundary region Aba as the second curvature Rib is formed in the liquid  530 . In particular, it is illustrated that the area of the boundary region Aba contacting the electroconductive aqueous solution  595  in the inclined portion of the first insulator  550   a  on the first electrode  540   a  is AMb. 
     According to Equation 1, the area of the boundary region Aba in  FIG. 5B  is larger than that in  FIG. 5A , and therefore the capacitance of the boundary region Aba becomes larger. The capacitance of  FIG. 5B  may be defined as CAba, which is greater than the capacitance CAaa of  FIG. 5A . 
     The second curvature Rib may be defined as having a value of positive polarity greater than the first curvature Ria. For example, the second curvature Rib may be defined as having a level of +4. 
     Referring to  FIGS. 5A and 5B , the liquid lens  500  operates as a convex lens, thereby outputting output light LP 1   a  formed by converging the incident light LP 1 . 
     Next,  FIG. 5C  illustrates a case where a third curvature Ric is formed in the liquid  530  according to application of an electrical signal to the plurality of electrodes (LA to LD)  540   a  to  540   d  and the common electrode  520 . 
     In particular,  FIG. 5C  illustrates that AMa is given as the area of the left boundary region Aca, and AMb (&gt;AMa) is given as the area of the right boundary region Acb. 
     More specifically, the area of the boundary region Aca contacting the electroconductive aqueous solution  595  in the inclined portion of the first insulator  550   a  on the first electrode  540   a  is AMa, and the area of the boundary region Acb contacting the electroconductive aqueous solution  595  in the inclined portion of the second insulator  550   b  on the second electrode  540   b  is AMb. 
     Thus, the capacitance of the left boundary region Aca may be CAaa, and the capacitance of the right boundary region Acb may be CAba. 
     In this case, the third curvature Ric may be defined as having a value of positive polarity. For example, the third curvature Ric may be defined as having a level of +3. 
     Referring to  FIG. 5C , the liquid lens  500  operates as a convex lens, thereby outputting output light LP 1   b  by converging the incident light LP 1  further to one side. 
     Next,  FIG. 5D  illustrates a case where a fourth curvature Rid is formed in the liquid  530  according to application of an electrical signal to the plurality of electrodes (LA to LD)  540   a  to  540   d  and the common electrode  520 . 
     In  FIG. 5D , AMd (&lt;AM 0 ) is exemplarily given as the area of the boundary region Ada as the fourth curvature Rid is formed in the liquid  530 . In particular, it is illustrated that the area of the boundary region (Ada) contacting the electroconductive aqueous solution  595  in the inclined portion of the first insulator  550   a  on the first electrode  540   a  is AMd. 
     According to Equation 1, the area of the boundary region (Ada) in  FIG. 5D  is smaller than that of  FIG. 4C , and therefore the capacitance of the boundary region (Ada) is reduced. The capacitance of  FIG. 5D  may be defined as CAda and has a value less than the capacitance CAc 0  of  FIG. 4C . 
     In this case, the fourth curvature Rid may be defined as having a value of negative polarity. For example, it may be defined that the fourth curvature Rid has a level of −2. 
     Next,  FIG. 5E  illustrates that the fifth curvature Rie is formed in the liquid  530  according to application of an electrical signal to the plurality of electrodes (LA to LD)  540   a  to  540   d  and the common electrode  520 . 
     In  FIG. 5E , AMe (&lt;AMd) is exemplarily given as the area of the boundary region Aea when the fifth curvature Rie is formed in the liquid  530 . In particular, it is illustrated that the area of the boundary region Aea contacting the electroconductive aqueous solution  595  in the inclined portion of the first insulator  550   a  on the first electrode  540   a  is AMe. 
     According to Equation 1, the area of the boundary region Aea in  FIG. 5E  is smaller than that of  FIG. 5D , and therefore the capacitance of the boundary region Aea becomes smaller. The capacitance of  FIG. 5E  may be defined as CAea, which is less than the capacitance CAda of  FIG. 5D . 
     In this case, the fifth curvature Rie may be defined as having a value of negative polarity. For example, the fifth curvature Rie may be defined as having a level of −4. 
     Referring to  FIGS. 5D and 5E , the liquid lens  500  operates as a concave lens, thereby outputting output light LP 1   c  by diverging the incident light LP 1 . 
       FIG. 6  is an exemplary internal block diagram of a camera related to the present invention. 
     Referring to  FIG. 6 , the camera  195   x  may include a lens curvature variation apparatus  800 , an image sensor  820 , an image processor  860 , a gyro sensor  830 , and a liquid lens  500 . 
     The lens curvature variation apparatus  800  may include a lens driver  860 , a pulse width variation controller  840 , and a power supply  890 . 
     The lens curvature variation apparatus  800  of  FIG. 6  operates as follows. The pulse width variation controller  840  outputs a pulse width variation signal V corresponding to a target curvature, and the lens driver  860  may output corresponding voltages to the plurality of electrodes and the common electrode of the liquid lens  500  using the pulse width variation signal V and the voltage Vx of the power supply  890 . 
     That is, the lens curvature variation apparatus  800  of  FIG. 6  operates as an open loop system to vary the curvature of the liquid lens. 
     According to this method, the curvature of the liquid lens  500  cannot be sensed, except that corresponding voltages are output to the plurality of electrodes and the common electrode of the liquid lens  500  according to the target curvature. 
     In addition, according to the lens curvature variation apparatus  800  of  FIG. 6 , when the curvature of the liquid lens  500  needs to be varied to inhibit blurring, it may be difficult to accurately vary the curvature since the curvature is not sensed. 
     Therefore, in the present invention, the lens curvature-variable device  800  is not implemented as an open loop system as shown in  FIG. 6 , but is implemented as a closed loop system. 
     That is, in order to identify the curvature of the liquid lens  500 , the capacitance formed in the insulator on the electrode in the liquid in the liquid lens  500  and the boundary region Ac 0  contacting the electroconductive aqueous solution  595  is sensed, and is fed back to calculate the difference between the target curvature and the current curvature and perform a control operation corresponding to the difference. 
     Accordingly, the curvature of the liquid lens  500  may be identified quickly and accurately, and the curvature of the liquid lens  500  may be controlled quickly and accurately so as to correspond to the target curvature. This operation will be described in more detail with reference to  FIG. 7  and subsequent drawings. 
       FIG. 7  is an exemplary internal block diagram of a camera according to an embodiment of the present invention. 
     Referring to  FIG. 7 , a camera  195   m  according to an embodiment of the present invention may include a lens curvature variation apparatus  900  to vary the curvature of a liquid lens  500 , an image sensor  820  to convert light from the liquid lens  500  into an electrical signal, and an image processor  930  to perform image processing based on the electrical signal from the image sensor  820 . image processor 
     The camera  195   m  of  FIG. 7  may further include a gyro sensor  915 . 
     The image processor  930  may output focus information AF about an image, and the gyro sensor  915  may output blurring information OIS. 
     Thus, the controller  970  in the lens curvature variation apparatus  900  may determine the target curvature based on the focus information AF and the blurring information OIS. 
     The lens curvature control apparatus  900  according to an embodiment of the present invention may include a lens driver  960  to apply an electrical signal to the liquid lens  500 , a sensor unit  962  to sense the curvature of the liquid lens  500  formed based on the electrical signal, and a controller  970  to control the lens driver  960  so as to form a target curvature of the liquid lens  500  based on the sensed curvature. The sensor unit  962  may sense the size or change in size of the area of the boundary region Ac 0  between an insulator on an electrode and an electroconductive aqueous solution  595  in the liquid lens  500 . Thus, the curvature of the lens may be sensed quickly and accurately. 
     According to an embodiment of the present invention, the lens curvature variation apparatus  900  may further include a liquid lens  500  having a curvature varied based on an applied electrical signal. 
     According to an embodiment of the present invention, the lens curvature control apparatus  900  may include a power supply  990  to supply power, and an analog-to-digital (AD) converter (not shown) to convert a signal related to the capacitance sensed by the sensor unit  962  into a digital signal. 
     The lens curvature variation apparatus  900  may include a plurality of conductive lines CA 1  and CA 2  for supplying an electrical signal from the lens driver  960  to each of the electrodes (the common electrode and the plurality of electrodes) in the liquid lens  500  driver, and a switching element SWL disposed between the sensor unit  962  and one CA 2  of the plurality of conductive lines. 
     The figure illustrates that the switching element SWL is disposed between the sensor unit  962  and the conductive line CA 2  for applying an electrical signal to any one of a plurality of electrodes in the liquid lens  500 . In this case, the contact point between the conductive line CA 2  and one end of the switching element SWL or the liquid lens  500  may be referred to as node A. 
     In the present invention, an electrical signal is applied to each of the electrodes (the common electrode and the plurality of electrodes) in the liquid lens  500  through the plurality of conductive lines CA 1  and CA 2  to sense the curvature of the liquid lens  500 . Thus, a curvature may be given to the liquid  530  as shown in  FIGS. 5A to 5E . 
     For example, during a first period, the switching element SWL may be turned on. 
     If an electrical signal is applied to the electrodes in the liquid lens  500  while the switching element SWL is turned on and is thus electrically connected with the sensor unit  962 , a curvature may be formed in the liquid lens  500 , and an electrical signal corresponding to the curvature may be supplied to the sensor unit  962  via the switching element SWL. 
     Thus, the sensor unit  962  may sense the size of the area of the boundary region Ac 0  between the insulator on the electrodes and the electroconductive aqueous solutions  595  in the liquid lens  500  or a change in the size or sense the capacitance of the boundary region Ac 0 , based on the electrical signal from the liquid lens  500  during the ON period of the switching element SWL. 
     Next, during a second period, the switching element SWL may be turned off, and the electrical signal may be continuously applied to the electrodes in the liquid lens  500 . Accordingly, a curvature may be formed in the liquid  530 . 
     Next, during a third period, the switching element SWL may be turned off, and no electrical signal or a low-level electrical signal may be applied to the electrodes in the liquid lens  500 . 
     Next, during a fourth period, the switching element SWL may be turned on. 
     If an electrical signal is applied to the electrodes in the liquid lens  500  while the switching element SWL is turned on and is electrically connected with the sensor unit  962 , a curvature may be formed in the liquid lens  500 , and an electrical signal corresponding to the curvature may be supplied to the sensor unit  962  via the switching element SWL. 
     If the curvature calculated based on the capacitance sensed during the first period is less than the target curvature, the controller  970  may control the pulse width of the pulse width variation control signal supplied to the driver  960  to be increased in order to obtain the target curvature. 
     Accordingly, the time difference between the pulses applied to the common electrode  530  and the plurality of electrodes may be increased, thereby increasing the curvature formed in the liquid  530 . 
     If an electrical signal is applied to the electrodes in the liquid lens  500  with the switching element SWL turned on and electrically connected with the sensor unit  962  during the fourth period, a curvature may be formed in the liquid lens  500 , and an electrical signal corresponding to the curvature may be supplied to the sensor unit  962  via the switching element SWL. 
     Thus, the sensor unit  962  may sense the size or change in size of the area of the boundary region Ac 0  between the insulator on the electrodes and the electroconductive aqueous solutions  595  in the liquid lens  500  or the capacitance of the boundary region Ac 0 , based on the electrical signal from the liquid lens  500  during the ON period of the switching element SWL. 
     Accordingly, the controller  970  may calculate the curvature based on the sensed capacitance, and may determine whether or not the curvature has reached the target curvature. If the curvature has reached the target curvature, the controller  970  may control a corresponding electrical signal to be supplied to each of the electrodes. 
     As the electrical signal is supplied, the curvature of the liquid  530  may be formed, and may be sensed immediately. Therefore, the curvature of the liquid lens  500  may be identified quickly and accurately. 
     The lens driver  960  and the sensor unit  962  may be implemented by a single module  965 . 
     The lens driver  960  and the sensor unit  962 , the controller  970 , the power supply  990 , the AD converter  967 , and the switching unit SWL shown in the figure may be implemented by a single system on chip (SOC). 
     As shown in  FIGS. 4A to 4C , the liquid lens  500  may include a common electrode (COM)  520 , a liquid  530  on the common electrode (COM)  520 , and an electroconductive aqueous solution  595  on the liquid  530 , and a plurality of electrodes (LA to LD) spaced apart from the liquid  530 . 
     As illustrated in  FIGS. 5A to 5E , the sensor unit  962  may sense the size or change in size of the area of the boundary region Ac 0  between an insulator on the electrodes and the electroconductive aqueous solution  595  in the liquid lens  500 , or may sense a capacitance corresponding thereto. 
     An analog signal related to the capacitance sensed by the sensor unit  962  may be converted into a digital signal through an AD converter  967  and input to the controller  970 . 
     As illustrated in  FIGS. 5A to 5E , as the curvature of the liquid lens  500  increases, the area of the boundary region Ac 0  increases, and consequently the capacitance of the boundary region Ac 0  increases. 
     In the present invention, it is assumed that the curvature is calculated using the capacitance sensed by the sensor unit  962 . 
     The controller  970  may control the level of a voltage applied to the liquid lens  500  to increase or the pulse width to increase so as to increase the curvature of the liquid lens  500 . 
     As shown in  FIG. 5C , when voltages of different levels or different pulse widths are applied to a first electrode  540   a  and a third electrode  540   c  among the plurality of electrodes (LA to LD)  540   a  to  540   d , a first capacitance of a first end portion Aca of the liquid  530  and a second capacitance of a second end portion Acb of the liquid  530  differ from each other. 
     Thus, the sensor unit  962  may sense the capacitances of the first end portion Aca and the second end portion Acb of the liquid  530 , respectively. 
     By sensing the capacitances around the end operations of the liquid  530  in the liquid lens  500 , the curvature of the lens may be accurately detected. 
     In other words, by sensing the capacitances of a plurality of boundary regions between the insulator on the electrodes and the electroconductive aqueous solution  595  in the liquid lens  500 , the curvature of the liquid lens may be accurately detected. 
     When a constant voltage is applied to the common electrode (COM)  520  and a pulse is applied to the plurality of electrodes (LA to LD)  540   a  to  540   d , the sensor unit  962  may sense the capacitances for a plurality of boundary regions between the insulator on the plurality of electrodes (LA to LD)  540   a  to  540   d  and the electroconductive aqueous solution  595 . 
     When a constant voltage is applied to the plurality of electrodes (LA to LD)  540   a  to  540   d  and a pulse is applied to the common electrode COM  520 , the capacitance of the boundary region between the insulator on the first electrode  520  and the electroconductive aqueous solution  595  may be sensed. 
     The controller  970  may calculate the curvature of the liquid lens  500  based on the capacitance sensed by the sensor unit  962 . 
     The controller  970  may calculate the curvature of the liquid lens  500  such that the curvature increases as the capacitance sensed by the sensor unit  962  increases. 
     Then, the controller  970  may control the liquid lens  500  to have a target curvature. 
     The controller  970  may calculate the curvature of the liquid lens  500  based on the capacitance sensed by the sensor unit  962 , and output a pulse width variation signal V based on the calculated curvature and the target curvature to the lens driver  960 . 
     Then, the lens driver  960  may use the pulse width variation signal V and the voltages Lv 1  and Lv 2  of the power supply  990  to output corresponding electrical signals to the plurality of electrodes (LA to LD)  540   a  to  540   d  and the common electrode ( 520 ). 
     Thus, as the capacitance of the liquid lens  500  is sensed and fed back, and an electrical signal is applied to the liquid lens  500  to vary the curvature of the lens, the curvature of the lens may be varied quickly and accurately. 
     The controller  970  may include an equalizer  972  to calculate a curvature error based on the calculated curvature and the target curvature, and a pulse width variation controller  940  to generate and output a pulse width variation signal V based on the calculated curvature error Φ. 
     Accordingly, if the calculated curvature is greater than the target curvature, the controller  970  may control the duty of the pulse width variation signal V to increase or delay corresponding to the time difference between a plurality of pulses applied to the liquid lens  500  to increase, based on the calculated curvature error Φ. Accordingly, the curvature of the liquid lens  500  may be varied quickly and accurately. 
     The controller  970  may receive focus information AF from the image processor  930  and blurring information OIS from the gyro sensor  915 , and determine the target curvature based on the focus information AF and the blurring information OIS. 
     Here, the update cycle of the determined target curvature is preferably longer than the update cycle of the curvature calculated based on the sensed capacitance of the liquid lens  500 . 
     Since the update cycle of the calculated curvature is shorter than the update cycle of the target curvature, the curvature of the liquid lens  500  may be quickly changed to a desired curvature. 
       FIGS. 8A to 12B  are views referred to in the description of  FIG. 7 . 
       FIG. 8A  shows curvature change curves of the liquid lens  500  in the liquid curvature variation apparatus  800  of  FIG. 6  and the lens curvature variation apparatus  900  of  FIG. 7 . 
     Referring to  FIG. 8A , GRo represents a curvature change curve of the liquid lens  500  in the lens curvature variation apparatus  800  of  FIG. 6 , and GRc represents a curvature change curve of the liquid lens  500  in the lens curvature variation apparatus  900  of  FIG. 7 . 
     In particular, the figure illustrates a case where that a voltage for changing the curvature to a target curvature is applied to the liquid lens  500  at time Tx, and is interrupted at time Ty. 
     It can be seen from the two curves that the change in curvature in the case of the lens curvature variation apparatus  800  of  FIG. 6  of the open loop system is slowly settled to a target diopter, and the change in curvature in the case of the lens curvature variation apparatus  900  of  FIG. 7  of the closed loop system is quickly and precisely settled, although not accurate. 
     The lens curvature variation apparatus  900  of  FIG. 7  of the closed loop system may have a settling time shorter than the lens curvature variation apparatus  800  of  FIG. 6  of the open loop system by about 70%. 
     Therefore, with the lens curvature variation apparatus  900  of  FIG. 7  of the closed loop system, the curvature and the diopter may be formed quickly and accurately. 
     The diopter may correspond to the curvature of the liquid  530  illustrated in  FIGS. 5A to 5E . Accordingly, it may be defined that the diopter increases as the curvature of the liquid  530  increases, and decreases as the curvature decreases. 
     For example, as shown in  FIGS. 5A and 5B , when the curvature has a level of +2 or +4, the diopter may be defined as having a level of +2 or +4 corresponding to a convex lens. When the curvature has a level of 0, the diopter may be defined as having a level of 0 corresponding to the plane lens. When the curvature has a level of −2 or −4 as shown in  FIGS. 5D and 5E , the diopter may be defined as having a level of −2 or −4 corresponding to the concave lens. 
       FIG. 8B  illustrates a timing chart for the common electrode COM, the first electrode LA, and the switching element SWL in the lens curvature variation apparatus  900  of  FIG. 7 . 
     Referring to  FIG. 8B , during a period Dt 1  between time T 1  and time T 3 , the switching element SWL is turned on. 
     In order to sense the capacitance of the boundary region Ac 0  through the sensor unit  962 , a curvature is preferably formed in the liquid lens  500  during the period Da between time T 1  and time T 3 . 
     In order to ensure accuracy and stability of the sensing operation of the sensor unit  962  in the present invention, a pulse is applied to one of the common electrode and the plurality of electrodes in the liquid lens  500  during the period Da between the time T 1  and the time T 3 . 
     In particular, as shown in  FIG. 8B , a pulse having a pulse width of Dt 2  may be applied to the common electrode  530  at time T 2 . Accordingly, after time T 2 , a curvature of the liquid lens  500  may be formed. 
     Accordingly, the sensor unit  962  may sense capacitances formed by the electroconductive aqueous solution  595  and the electrodes according to the size or change in size of the area of the boundary region Ac 0  between the insulator on the electrodes and the electroconductive aqueous solution  595  in the liquid lens  500  during a period between time T 2  and time T 3  in the period Da between time T 1  and time T 3 . 
     During the period between time T 2  and time T 3 , the sensor unit  962  may sense a potential difference or an electric current between the electroconductive aqueous solution  595  and the electrodes corresponding to the size or change in size of the area of the boundary region Ac 0  between the insulator on the electrodes and the electroconductive aqueous solution  595  in the liquid lens  500 . 
     Next, at time T 4 , a pulse having a pulse width of Dt 3  may be applied to the first electrode LA. 
     That is, a high-level voltage may be applied to the common electrode COM at time point T 2 , and a high-level voltage may be applied to the first electrode LA at time point T 4 . 
     The curvature formed in the liquid  530  in the liquid lens  500  may be varied according to a time difference DFF 1  between the pulse applied to the common electrode COM and the pulse applied to the first electrode LA. 
     For example, as the time difference DFF 1  between the pulses increases, the area of the boundary region Ac 0  in which the electrodes contact the electroconductive aqueous solution  595  may increase, and accordingly the capacitance and the curvature may increase. 
       FIGS. 9A and 9B  are diagrams illustrating various sensing methods for the sensor unit. 
       FIG. 9A  illustrates a sensor unit  962   a  capable of sensing a capacitance without applying a separate additional pulse signal. 
     The sensor unit  962   a  in the lens curvature variation apparatus  900   a  of  FIG. 9A  may operate in a continuous sensing manner. 
     To this end, the sensor unit  962   a  of  FIG. 9A  may include a filter  1112  to filter electrical signals from at least one of the plurality of electrodes (LA to LD)  540   a  to  540   d , a peak detector  1114  to detect a peak of the electrical signal and a programmable gain amplifier (PGA)  1116  to amplify the electrical signal from the peak detector  1114 . 
     Specifically, the sensor unit  962   a  of  FIG. 9A  may sense the capacitance of the liquid lens  500  during a turn-on period of the switching element SWL connected to at least one of the plurality of electrodes (LA to LD)  540   a  to  540   d.    
     Next,  FIG. 9B  illustrates a sensor unit  962   b  capable of applying a separate additional pulse signal to the common electrode (COM)  520  and sensing the capacitance during application of the additional pulse signal. 
     The sensor unit  962   b  in the lens curvature variation apparatus  900   b  of  FIG. 9B  may operate in a discrete sensing manner. 
     To this end, the sensor unit  962   b  of  FIG. 9B  may include a conversion unit  1122  to convert the capacitance from at least one of the plurality of electrodes (LA to LD)  540   a  to  540   d  into a voltage, and an amplifier  1124  to amplify the voltage. 
     More specifically, during the turn-on period of the switching element SWL connected to at least one of the electrodes (LA to LD)  540   a  to  540   d , an additional pulse signal may be applied to the common electrode (COM)  520 , and the sensor unit  962   b  of  FIG. 9B  may sense the capacitance of the liquid lens  500  formed based on the additional pulse signal. 
     A lens driver applicable to both of  FIGS. 9A and 9B  may be illustrated as shown in  FIG. 10 . 
       FIG. 10  is an exemplary internal circuit diagram of the lens driver of  FIG. 9A or 9B . 
     Referring to  FIG. 10 , the lens driver  960   a  of  FIG. 10  may include a first driver  961  to drive a lens and a second driver  1310  to drive a sensor. 
     The lens driver  960   a  may further include a pulse width controller  1320  to output a pulse width variation signal to the second driver  1310 . 
     The pulse width controller  1320  may be provided in the pulse width controller  940  of  FIG. 7 . 
     The first driver  961  may include first upper-arm and lower-arm switching elements Sa and S′a connected in series to each other and second upper-arm and lower-arm switching elements Sb and S′b connected in series to each other. 
     Here, the first upper-arm and lower-arm switching elements Sa and S′a and the second upper-arm and lower-arm switching elements Sb and S′b are connected in parallel to each other. 
     A power of level LV 2  from the power supply  990  may be supplied to the first upper-arm switching element Sa and the second upper-arm switching element Sb. 
     The second driver  1310  may include third upper-arm and lower-arm elements Sc and S′c connected in series to each other. 
     A power of level LV 1 , which is lower than level LV 2 , from the power supply  990  may be supplied to the third upper-arm switching element Sc to generate an additional pulse of a low level. 
     A voltage may be applied to the common electrode  520  through a node between the first upper-arm switching element Sa and a first upper-arm switching element S′a or a node between the third upper-arm switching element Sc and the third lower-arm switching element S′c, and a voltage may be applied to the first electrode (LA)  540   a  through a node between the second upper-arm switching element Sb and the second lower-arm switching element S′b. 
       FIG. 11A  is an exemplary waveform diagram for explaining the operation of the lens driver  960   a  of  FIG. 10 , and  FIG. 11B  is an exemplary diagram referred to for explaining the operation of the sensor unit  962   a  of  FIG. 9A . 
     Referring to  FIG. 11A , during the period Dt 1  between time T 1  and time T 3 , a high level is applied to the switching element SWL to turn on the switching element SWL. 
     During the period Da between time T 1  and time T 3 , low-level control signals LAP and LAM are applied to the switching element Sb and the switching element S′b, respectively, and thus the switching element Sb and the switching element S′b are floated. 
     The switching element Sb and the switching element S′b are complementarily turned on. However, both switching elements are floated during the period in which the switching element SWL is turned on. 
     At time T 2 , the control signal CMHP applied to the switching element Sa is switched to the high level and the control signal CMHM applied to the switching element S′a is switched to the low level. 
     The switching element Sa and the switching element S′a are always turned on complementarily. 
     At time T 2 , the control signal CMHP applied to the switching element Sa is switched to the high level. At time T 4 , the control signal LAp applied to the switching element Sb is switched to the high level. 
     A pulse having a pulse width of Dt 2  may be applied at time T 2  during the period Da between time T 1  and time T 3 . Accordingly, after time T 2 , the curvature of the liquid lens  500  may be formed. 
     Accordingly, during the period between time T 2  and time T 3  in the period Da between time T 1  and time T 3 , the sensor unit  962  may sense a capacitance corresponding to the size or change in size of the area of the boundary region Ac 0  between the insulator on the electrodes and the electroconductive aqueous solution  595  in the liquid lens  500 . 
     Specifically, during the period between time T 2  and time T 3 , a signal of level Lv 3  may be applied to the filter  1112 , the peak detector  114  may detect the signal, and the PGA  1116  may amplify the signal. Thus, during the period between time T 2  and time T 3 , the capacitance corresponding to the size or change in size of the area of the boundary region Ac 0  between the insulator on the electrodes and the electroconductive aqueous solution  595  in the liquid lens  500  may be sensed. 
     A high-level voltage may be applied to the common electrode COM at time T 2 , and a high-level voltage may be applied to the first electrode LA at time T 4 . 
     The curvature formed in the liquid  530  in the liquid lens  500  may be varied according to a time difference DFF 1  between the pulse applied to the common electrode COM and the pulse applied to the first electrode LA. 
     For example, as the time difference DFF 1  between the pulses increases, the area of the boundary region Ac 0  in which the electrodes contact the electroconductive aqueous solution  595  may increase, and accordingly the capacitance may increase. 
     In the example of  FIG. 11A , the second driver  1310  of  FIG. 10  does not operate. 
     Next, the common electrode  520  is grounded at time T 5 , and the first electrode (LA)  540   a  is grounded at time T 6 . Thereafter, the operations at times T 1  and T 2  are repeated at times T 7  and T 8 . 
       FIG. 11C  is another exemplary waveform diagram illustrating the operation of the lens driver  960   a  of  FIG. 10 , and  FIG. 11D  is a diagram illustrating the operation of the sensor unit  962   a  of  FIG. 9A . 
       FIG. 11C  is similar to the waveform diagram of  FIG. 11A  except that control signals CMLP and CMLM for operation of the switching elements Sc and S′c in the second driver  1310  of  FIG. 10  are provided. 
     The sensor unit SWL is turned on during the period between T 1  and T 2  and is turned off after T 2 . 
     At time T 2 , the control signal CMHP applied to the switching element Sa is switched to the high level. At time T 3 , the control signal LAp applied to the switching element Sb is switched to the high level. 
     During the period between T 1  and T 2 , the switching element Sc may be turned on. Then, as shown in  FIG. 11D , an additional pulse SMP having a level Lv 1  supplied from the power supply  990   b  may be applied to the common electrode COM. 
     Accordingly, during the period Da between time T 1  and time T 2 , the sensor unit  962  may sense a capacitance corresponding to the size or change in size of the area of the boundary region Ac 0  between the insulator on the electrodes and the electroconductive aqueous solution  595  in the liquid lens  500 . 
     Specifically, during the period between time T 1  and T 2 , a signal of a level Lv 5  lower than the level Lv 3  may be applied to the filter  1112 , the peak detector  114  may detect the signal, and the PGA  1116  may amplify the signal. Thus, during the period between time T 1  and time T 2 , the capacitance corresponding to the size or change in size of the area of the boundary region Ac 0  between the insulator on the electrodes and the electroconductive aqueous solution  595  in the liquid lens  500  may be sensed. 
     Next, at time T 3 , a pulse SLP having a pulse width of Dt 2  and a level Lv 2  higher than the level Lv 1  may be applied to the common electrode COM. 
     Next, at time T 4 , a pulse having a pulse width of Dt 3  may be applied to the first electrode LA. 
     The curvature formed in the liquid  530  in the liquid lens  500  may be varied according to a time difference DFF 1  between the pulse applied to the common electrode COM and the pulse applied to the first electrode LA. 
     For example, as the time difference DFF 1  between the pulses decreases, the area of the boundary region Ac 0  in which the electrodes contact the electroconductive aqueous solution  595  may increase, and accordingly the capacitance may increase. As a result, the curvature may decrease. 
       FIG. 12A  is another exemplary waveform diagram illustrating the operation of the lens driver  960   a  of  FIG. 10 , and  FIG. 12B  is a diagram illustrating the operation of the sensor unit  962   b  of  FIG. 9B . 
       FIG. 12A  is similar to the waveform diagram of  FIG. 11C . However, unlike  FIG. 11C , during the period from T 1  to T 2 , control signals CMLP and CMLM for operating the switching elements Sc and S′c in the second driver  1310  of  FIG. 10  have a plurality of pulses instead of a single pulse. 
     Thus, as shown in  FIG. 12B , a plurality of pulses SMPa is applied to the common electrode COM during the period from T 1  to T 2 . 
     Accordingly, during the period Da between time T 1  and time T 2 , the sensor unit  962  may sense a capacitance corresponding to the size or change in size of the area of the boundary region Ac 0  between the insulator on the electrodes and the electroconductive aqueous solution  595  in the liquid lens  500 . 
     Specifically, during the period between time T 1  and time T 2 , a plurality of pulse signals Lv 3  may be applied to the C2V converter  1122 , and the SC amplifier  1124  may amplify the plurality of pulse signals. Thus, during the period between time T 1  and time T 2 , the capacitance corresponding to the size or change in size of the area of the boundary region Ac 0  between the insulator on the electrodes and the electroconductive aqueous solution  595  in the liquid lens  500  may be sensed. In particular, a voltage signal corresponding to the capacitance may be output as the output of the sensor section  962 . 
       FIG. 13A  is an exemplary internal block diagram of a camera according to another embodiment of the present invention. 
     Referring to  FIG. 13A , the camera  195   n  and the lens curvature variation apparatus  900   b  shown in  FIG. 13A  are similar to the camera  195   m  and the lens curvature variation apparatus  900  shown in  FIG. 7 , except that the capacitances of the end portions of a plurality of liquids  530  corresponding to a plurality of electrodes (LA to LD)  540   a  to  540   d  are sensed. 
     To this end, a low-level voltage is applied to the common electrode (COM)  520 , and a pulse signal may be applied to the plurality of electrodes (LA to LD)  540   a  to  540   d.    
     Preferably, to allow operation of the sensor unit  962 , a plurality of switching elements SWLa to SWLd is provided between conductive lines CA to CD, which are connected between the plurality of electrodes (LA to LD) and the liquid lens  500 , and the sensor unit  962 . 
     The sensor unit  962  may sense the capacitances of the boundary regions between the insulator on the plurality of electrodes (LA to LD)  540   a  to  540   d  and the electroconductive aqueous solution based on the pulse signals applied to the plurality of electrodes (LA to LD)  540   a  to  540   d  during a period in which the plurality of switching elements SWLa to SWLd is turned on, and may transmit the sensed capacitances to the controller  970 . 
     Accordingly, the capacitances of a plurality of boundary regions of the liquid lens  500  may be sensed. 
     Further, the camera  195   n  of  FIG. 13A  may vary the voltages applied to the plurality of electrodes (LA to LD)  540   a  to  540   d  for blurring correction to form an asymmetric curvature. Blurring correction may be performed accurately and quickly. 
       FIG. 13B  is an exemplary internal block diagram of a camera according to yet another embodiment of the present invention. 
     Referring to  FIG. 13B , the camera  195   o  and the lens curvature variation apparatus  900   c  shown in  FIG. 13B  are similar to the camera  195   m  and the lens curvature variation apparatus  900  shown in  FIG. 7 , except that the capacitances of the end portions of the liquid corresponding to the plurality of electrodes (LA to LD)  540   a  to  540   d  are sensed. 
     To this end, a low-level voltage may be applied to the plurality of electrodes (LA to LD)  540   a  to  540   d , and a pulse signal may be applied to the common electrode (COM) 
     Preferably, to allow the operation of the sensor unit  962 , a switching element SWL is provided between a conductive line CM, which is connected between the common electrode COM and the liquid lens  500 , and the sensor unit  962 , instead of the conductive lines CA to CD connected between the plurality of electrodes (LA to LD)  540   a  to  540   d  and the liquid lens  500 . 
     The sensor unit  962  may sense the capacitance of the boundary region between the insulator on the electrodes and the electroconductive aqueous solution based on the pulse signal applied to the common electrode COM during a period in which the switching element SWL is turned on, and may transmit the sensed capacitance to the controller  970 . 
     Accordingly, the capacitance of the boundary region of the liquid lens  500  may be sensed. 
     Further, the camera  195   o  of  FIG. 13B  may form an asymmetric curvature in response to blurring correction, and therefore the blurring correction may be performed accurately and quickly. 
     The lens curvature variation apparatus  900  described with reference to  FIGS. 9A-13B  may be employed for various electronic devices such as the mobile terminal, a vehicle, a TV, a drone, a robot, and a robot cleaner. 
     The method of operating the lens curvature variation apparatus of the present invention may be implemented as a code that can be read by a processor on a recording medium readable by a processor included in the lens curvature variation apparatus. The processor-readable recording medium may include all kinds of recording apparatuses in which data readable by the processor is stored. Examples of the recording medium readable by the processor include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device, and may also be implemented in the form of a carrier wave such as transmission over the Internet. In addition, the processor-readable recording medium may be distributed over network-connected computer systems such that code readable by the processor in a distributed fashion may be stored and executed. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention is applicable to a lens curvature variation apparatus capable of quickly and accurately sensing the curvature of a lens.