Patent Publication Number: US-2022229264-A1

Title: Liquid lens control device

Description:
TECHNICAL FIELD 
     Embodiments relate to a liquid lens control device. 
     BACKGROUND ART 
     People who use portable devices demand optical devices that have high resolution, are small, and have various photographing functions. For example, the various photographing functions may include at least one of an optical zoom-in/zoom-out function, an auto-focusing (AF) function, or a hand-tremor compensation or optical image stabilization (OIS) function. 
     Conventionally, the aforementioned various photographing functions are realized by combining a plurality of lenses and directly moving the combined lenses. In the case in which the number of lenses is increased, however, the size of an optical device may increase. 
     The AF function and the hand-tremor compensation function are performed by moving or tilting a plurality of lenses, which are fixed to a lens holder and are aligned with an optical axis, in the optical-axis direction or in a direction perpendicular to the optical axis. To this end, a separate lens-moving apparatus is used to move a lens assembly constituted by a plurality of lenses. However, the lens-moving apparatus consumes a lot of power, and an additional cover glass needs to be provided separately from a camera module in order to protect the lens-moving apparatus, thus leading to an increase in the overall size of the conventional camera module. In order to solve this, research has been conducted on a liquid lens configured to electrically adjust the curvature of an interface between two types of liquids in order to perform the AF function and the hand-tremor compensation function. 
     Also, research with the goal of improving spatial frequency response (SFR) and an OIS suppression ratio by precisely controlling a liquid lens has been conducted. 
     DISCLOSURE 
     Technical Problem 
     Embodiments provide a liquid lens control device capable of precisely controlling a liquid lens in order to improve spatial frequency response and an OIS suppression ratio without increasing the size thereof. 
     The objects to be accomplished by the embodiments are riot limited to the above-mentioned objects, and other objects not mentioned herein will be clearly understood by those skilled in the art from the following description. 
     Technical Solution 
     liquid lens control device according to an embodiment may include a liquid lens configured to control the interface between liquids in response to a plurality of individual voltages applied to respective ones of a plurality of individual electrodes, a controller configured to control the plurality of individual voltages, and a compensator configured to compensate for the characteristic of at least one individual electrode among the plurality of individual electrodes. 
     For example, the characteristic compensated for by the compensator may be the position of the interface according to the individual voltage applied to the individual electrode. 
     For example, the compensator may perform compensation using a first ADC value, acquired when a first voltage is applied to each of the plurality of individual electrodes, and a second ADC value, acquired when a second voltage, which is different from the first voltage, is applied to each of the plurality of individual electrodes. 
     For example, the compensator may perform compensation using the slope of the straight line connecting the first ADC value corresponding to the first voltage and the second ADC value corresponding to the second voltage for each of the plurality of individual electrodes. 
     For example, the compensator may include a single compensator, and the single compensator may compensate for the characteristic. 
     For example, the compensator may include a plurality of compensators that respectively correspond to the individual electrodes, and each of the plurality of compensators may compensate for the characteristic of the individual electrode corresponding to each of the compensators. 
     For example, the compensator may calculate a plurality of first slopes, each of which is the slope of an ADC value corresponding to the position of the interface between the liquids in the liquid lens with respect to the individual voltage for each of the plurality of individual electrodes, may calculate a reference slope using at least two of the plurality of first slopes, and may correct at least one first slope, among the plurality of first slopes, using the reference slope. One of the at least one first. slope may be the slope having the largest deviation from the reference slope. 
     For example, the reference slope may be the average value of the remaining slopes, other than the slope having the largest deviation, among the plurality of first slopes. 
     For example, the liquid lens control device may include a first driving voltage generator configured to generate an individual voltage that is applied to an individual electrode having at least one corrected first slope among the plurality of first slopes, a second driving voltage generator configured to generate an individual voltage that is applied to an individual electrode having the remaining slope, other than the at least one corrected first slope, among the plurality of first slopes, and a compensator configured to multiply a plurality of individual voltages generated by the first and second driving voltage generators by the same compensation gain and to apply the result of multiplication to the plurality of individual electrodes. 
     Advantageous Effects 
     A liquid lens control device according to an embodiment is capable of correcting variation in the response of a liquid lens for voltages applied to individual electrodes, thereby more accurately driving the liquid lens. 
     However, the effects achievable through the embodiments are not limited to the above-mentioned effects, and other effects not mentioned herein will be clearly understood by those skilled in the art from the following description. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a camera module according to an embodiment. 
         FIG. 2  is a cross-sectional view of a liquid lens unit. 
         FIGS. 3( a ) and ( b )  are views for explaining a liquid lens, the interface of which is adjusted in response to a driving voltage. 
         FIG. 4  a block diagram of the camera module according to the embodiment. 
         FIG. 5  is a graph showing an ADC value for each of individual voltages applied to respective ones of individual electrodes before correction. 
         FIG. 6  is a graph showing an ADC value for each of individual voltages after correction. 
         FIG. 7  is a block diagram of a correction method in a liquid lens control device according to an embodiment. 
         FIG. 8  is a block diagram of a liquid lens control device according to another embodiment. 
     
    
    
     BEST MODE 
     Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. 
     The examples, however, may be embodied in many different forms, and should not be construed as being limited to the embodiments set forth herein. Rather, within the spirt and scope of the present disclosure, one or more components may be selectively and operatively combined or substituted. 
     Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meanings as commonly understood by those skilled in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having meanings consistent with their meanings in the context of the relevant art. 
     Terms used in the embodiments of the present disclosure are provided for description of the embodiments, and the present disclosure is not limited thereto, in the specification, singular forms in sentences include plural forms unless otherwise noted. The meaning of “at least one of A, B, or C (or one or more of A, B, and C)” may be one or more combinations among all possible combinations that can be obtained from A, B, and C. 
     Additionally, terms such as “first”, “second”, “A”, “B”, “(a)”, “(b)”, etc. may be used herein to describe the components of the embodiments of the present disclosure. These terms are only used to distinguish one element from another element, and the essence, order, or sequence of corresponding elements is not limited by these terms. 
     It should be noted that if it is described in the specification that one component is “connected”, “coupled”, or “joined” to another component, the former may be directly “connected”, “coupled”, or “joined” to the latter, or may be indirectly “connected”, “coupled”, or “joined” to the latter via another component interposed therebetween. 
     It will be understood that when an element is referred to as being “on” or “under” another element, it can be directly on/under the element, or one or more intervening elements may also be present. When an element is referred to as being “on” or “under,” “under the element” as well as “on the element” can be included based on the element. 
     A variable lens may be a variable focus lens. Further, a variable lens may be a lens that is adjustable in focus. A variable lens may be at least one of a liquid lens, a polymer lens, a liquid-crystal lens, a voice coil motor (VCM) type, or a shape memory alloy (SMA) type. A liquid lens may include a liquid lens including a single liquid and a liquid lens including two liquids. A liquid lens including a single liquid may change the focus by adjusting a membrane disposed at a position corresponding to the liquid, for example, by pressing the membrane using the electromagnetic force between a magnet and a coil. A liquid lens including two liquids may include a conductive liquid and a non-conductive liquid, and may adjust the interface formed between the conductive liquid and the non-conductive liquid using the voltage applied to the liquid lens. A polymer lens may change the focus by controlling a polymer material using a driving unit such as a piezo actuator. A liquid-crystal lens may change the focus by controlling a liquid crystal using electromagnetic force. A VCM type may change the focus by adjusting a solid lens or a lens assembly including a solid lens using the electromagnetic force between a magnet and a coil. An SMA type may change the focus by controlling a solid lens or a lens assembly including a solid lens using a shape memory alloy. 
     Hereinafter, a variable lens to be controlled by a control device according to an embodiment will be described as being a liquid lens. However, the following description may also apply to the case in which the control device according to the embodiment controls variable lenses other than a liquid lens. 
     Hereinafter, a liquid lens  142 , which is an object to be controlled, and a camera module  100  including the liquid lens  142  will be described with reference to the accompanying drawings prior to describing a liquid lens control device  200  according to an embodiment. 
       FIG. 1  is a schematic cross-sectional view of a camera module  100  according to an embodiment. 
     Referring to  FIG. 1 , the camera module  100  may include a lens assembly  22 , a control circuit  24 , and an image sensor  26 . 
     The lens assembly  22  may include at least one lens unit. The at least one lens unit may include first and second lenses and a liquid lens unit (or a liquid lens module). 
     The control circuit  24  serves to control a lens unit, e.g. a liquid lens unit, and to supply a driving voltage (or an operating voltage) for driving the liquid lens unit. The control circuit  24  may be implemented in the form of an integrated circuit (IC). The control circuit  24  may include a liquid lens control device  200  to be described later. 
     The image sensor  26  may function to convert light that has passed through the first lens, the liquid lens unit, and the second lens into image data. More specifically, the image sensor  26  may convert light into analog signals through a pixel array including a plurality of pixels, and may synthesize digital signals corresponding to the analog signals to generate image data. 
     The control circuit  24  and the image sensor  26  described above may be disposed on a single printed circuit board (PCB). However, this is merely exemplary, and the embodiments are not limited thereto. 
     When the camera module  100  is applied to an optical device (or an optical instrument), the configuration of the control circuit  24  may be designed differently depending on the specifications required for the optical device. In particular, the control circuit  24  may be implemented as a single chip having the form of an integrated circuit (IC). 
     The first lens may be disposed on the lens assembly  22 , and may be a region on which light is incident from outside the lens assembly  22 . The first lens may be implemented as a single lens, or may be implemented as two or more lenses that are aligned with a central axis to form an optical system. Here, the central axis may be an optical axis LX of an optical system that is formed by the first lens, the liquid lens unit, and the second lens included in the camera module  100 , or may be an axis parallel to the optical axis LX. The optical axis LX may correspond to the optical axis of the image sensor  26 . That is, the first lens, the liquid lens unit, the second lens, and the image sensor  26  may be disposed so as to be aligned with the optical axis LX through active alignment (AA). Here, the active alignment may be the operation of aligning the optical axis of each of the first lens, the second lens, and the liquid lens unit with the optical axis of the image sensor  26 . 
     The second lens may be disposed under the liquid lens unit. The second lens may be spaced apart from the first lens in the optical-axis direction. 
     The light incident on the first lens from outside the camera module  100  may pass through the liquid lens unit, and may be incident on the second lens. The second lens may be implemented as a single lens, or may be implemented as two or more lenses that are aligned with the central axis to form an optical system. 
     Unlike the liquid lens unit, each of the first lens and the second lens may be a solid lens, and may be formed of plastic. However, the embodiments are not limited as to the specific material of each of the first lens and the second lens. 
       FIG. 2  is a cross-sectional view of a general liquid lens unit. 
     The liquid lens unit shown in  FIG. 2  may include a first connection substrate (or an individual electrode connection substrate)  144 , a liquid lens (or a liquid lens body), and a second connection substrate (or a common electrode connection substrate)  146 . 
     The liquid lens may include a plurality of different kinds of liquids LQ 1  and LQ 2 , first to third plates P 1 , P 2 , and P 3 , first and second electrodes E 1  and E 2 , and an insulating layer  148 . 
     The plurality of liquids LQ 1  and LQ 2  may be accommodated in a cavity CA, and may include a first liquid LQ 1 , which is conductive, and a second liquid (or an insulating liquid) LQ 2 , which is not conductive. The first liquid LQ 1  and the second liquid LQ 2  may be immiscible with each other, and an interface BO may be formed at the contact portion between the first liquid LQ 1  and the second liquid LQ 2 . For example, the first liquid LQ 1  may be disposed on the second liquid LQ 2 , but the embodiments are not limited thereto. 
     The inner surface of the first plate P 1  may form a sidewall i of the cavity CA. The first plate P 1  may include upper and lower openings having a predetermined inclined surface. That is, the cavity CA may be defined as a region surrounded by the inclined surface i of the first plate P 1 , the first opening contacting the second plate P 2 , and the second opening contacting the third plate P 3 . 
     The diameter of the opening that is larger, among the first opening and the second opening, may vary depending on the field of view (FOV) required for the liquid lens or the role that the liquid lens plays in the camera module  100 . The size (or the area or the width) of the first opening O 1  may be greater than the size (or the area or the width) of the second opening O 2 . Here, the size of each of the first opening and the second opening may be the cross-sectional area in the horizontal direction. For example, when each of the first and second openings has a circular cross-section, the size thereof may be a radius, and when each of the first and second openings has a square cross-section, the size thereof may be a diagonal length. 
     Each of the first and second openings may have the shape of a hole having a circular cross-section. The interface BO formed between the two liquids may be moved along the inclined surface i of the cavity CA by the driving voltage applied to the liquid lens. 
     The first liquid LQ 1  and the second liquid LQ 2  are charged, accommodated, or disposed in the cavity CA in the first plate P 1 . In addition, the cavity CA is a portion through which the light that has passed through the first lens passes. Therefore, the first plate P 1  may be formed of a transparent material, or may include impurities so that light does not easily pass therethrough. 
     Electrodes may be disposed on one surface and another surface of the first plate P 1 . A plurality of first electrodes E 1  may be spaced apart from a second electrode E 2 , and may be disposed on one surface (e.g. the lower surface, the side surface, or the upper surface) of the first plate P 1 . The second electrode E 2  may be disposed on at least a portion of the other surface (e.g. the upper surface) of the first plate P 1 , and may be in direct contact with the first liquid LQ 1 . 
     In addition, the first electrode E 1  may be implemented as a plurality of electrodes (hereinafter referred to as “individual electrodes”), and the second electrode E 2  may be implemented as a single electrode (hereinafter referred to as a “common electrode”). 
     A portion of the second electrode E 2  that disposed on the other surface of the first plate P 1  may be exposed to the first liquid LQ 1 , which is conductive. 
     Each of the first and second electrodes E 1  and E 2  may be formed of a conductive material. 
     In addition, the second plate P 2  may be disposed on one surface of the second electrode E 2 . That is, the second plate P 2  may be disposed on the first plate P 1 . Specifically, the second plate P 2  may be disposed on the upper surface of the second electrode E 2  and the cavity CA. 
     The third plate P 3  may be disposed on one surface of the first electrode E 1 . That is, the third plate P 3  may be disposed under the first plate P 1 . Specifically, the third plate P 3  may be disposed under the lower surface of the first electrode E 1  and the cavity CA. 
     The second plate P 2  and the third plate P 3  may be disposed opposite each other, with the first plate P 1  interposed therebetween. At least one of the second plate P 2  or the third plate P 3  may be omitted. 
     At least one of the second plate P 2  or the third plate P 3  may have a rectangular planar shape. Each of the second and third plates P 2  and P 3  may be a region through which light passes, and may be formed of a light-transmissive material. For example, each of the second and third plates P 2  and P 3  may be formed of glass. The second and third plates and P 3  may be formed of the same material as each other for convenience of processing. 
     In one example, light may be incident on the second plate P 2  from the first lens. That is, in the cavity CA, the area of the first opening, which faces the direction from which light is incident, may be greater than the area of the second opening, which faces the opposite direction. To this end, the second plate P 2  may have a configuration that allows light to travel into the cavity CA. The third plate P 3  may have a configuration that allows the light that has passed through the cavity CA in the first plate P 1  to travel to the second lens. 
     In another example, light may be incident on the third plate P 3  from the first lens. That is, in the cavity CA, the area of the second opening, which faces the direction from which light is incident, may be less than the area of the first opening, which faces the opposite direction. To this end, the third plate P 3  may have a configuration that allows light to travel into the cavity CA. The second plate P 2  may have a configuration that allows the light that has passed through the cavity CA in the first plate P 1  to travel to the second lens. 
     The second plate P 2  may be in direct contact with the first liquid LQ 1 . 
     The insulating layer  148  may be disposed so as to cover a portion of the upper surface of the third plate P 3  under the cavity CA. That is, the insulating layer  148  may be disposed between the second liquid LQ 2  and the third plate P 3 . 
     In addition, the insulating layer  148  may be disposed so as to cover the portion of the first electrode El that forms the sidewall of the cavity CA. In addition, the insulating layer  148  may be disposed so as to cover a portion of the second electrode  92 , the first plate P 1 , and the first electrode E 1  on the upper surface of the first plate P 1 . Accordingly, contact between the first electrode E 1  and the first liquid LQ 1  and contact between the first electrode E 1  and the second liquid LQ 2  may be prevented by the insulating layer  148 . 
     The insulating layer  148  may cover one (e.g. the first electrode E 1 ) of the first and second electrodes E 1  and E 2 , and may expose a portion of the other one thereof (e.g. the second electrode E 2 ), so that electric energy is applied to the first liquid LQ 1 , which is conductive. 
     The first connection substrate  144  may electrically connect the plurality of first electrodes  144  included in the liquid lens to a main board (not shown). The second connection substrate  146  may electrically connect the second electrode E 2  of the liquid lens to the main board. To this end, the first connection substrate  144  may be implemented as a flexible printed circuit board (FPCB), and the second connection substrate  146  may be implemented as an FPCB or a single metal substrate (a conductive metal plate). 
     The first connection substrate  144  may be electrically connected to an electrode pad formed on the main board via a connection pad electrically connected to each of the plurality of first electrodes E 1 . 
     The second connection substrate  146  may be electrically connected to an electrode pad formed on the main board via a connection pad electrically connected to the second electrode E 2 . 
     The main board may include a recess, in which the image sensor  26  may be mounted, seated, tightly fitted, fixed, provisionally fixed, supported, coupled, or accommodated, and a circuit element (not shown). The circuit element of the main board may constitute a liquid lens control device  200  for controlling the liquid lens, which will be described later. The liquid lens control device  200  will be described later with reference to  FIG. 4 . The circuit element may include at least one of a passive element or an active element, and may have any of various areas and heights. 
     The main board may be implemented as a rigid flexible printed circuit board (RFPCB) including an FPCB. The FPCB may be bent according to the requirements of the space in which the camera module  100  is mounted. 
       FIGS. 3( a ) and ( b )  are views for explaining the liquid lens  142 , the interface of which is adjusted in response to a driving voltage. Specifically,  FIG. 3( a )  is a perspective view of the liquid lens  142  included in the lens assembly  22 , and  FIG. 3( b  )  illustrates an equivalent circuit of the liquid lens  142 . Here, the liquid lens  142  may correspond to the liquid lens shown in  FIG. 2 . 
     Referring to  FIG. 3( a ) , the liquid lens  142 , the interface BO of which is adjusted in shape in response to a driving voltage, may receive individual voltages through a plurality of individual electrodes, which are disposed at the same angular interval from each other in four different directions. The individual electrodes may be disposed at the same angular interval from each other with respect to the central axis of the liquid lens  142 . Although it is illustrated in  FIG. 3( a )  that four individual electrodes E 11 , E 12 , E 13 , and E 14  are respectively disposed at the four corners, the embodiments are not limited thereto. Further, the liquid lens  142  may receive a common voltage through a common electrode E 2 . 
     The shape of the interface BO between the first liquid LQ 1  and the second liquid LQ 2 , which are disposed in the cavity CA, may be changed by the driving voltage formed by the interaction between the individual voltages applied through the plurality of individual electrodes E 11 , E 12 , E 13 , and E 14  and the common voltage applied through the common electrode E 2 . The shape and deformation of the interface BO between the first liquid LQ 1  and the second liquid LQ 2  may be controlled by the liquid lens control device  200  shown in  FIG. 4 , which will be described later, in order to implement at least one of the AF function or the OIS function. 
     In addition, referring to  FIG. 3( b ) , the liquid lens  142  may be constituted by a plurality of capacitors C 1 , C 2 , C 3 , and C 4 , one side of each of which receives an operating voltage from a corresponding one of the individual electrodes E 11 , E 12 , E 13 , and E 14 , which are different from each other, and the opposite side of each of which is connected to the common electrode E 2 . Here, each of the plurality of capacitors C 1 , C 2 , C 3 , and C 4  included in the equivalent circuit may have a low capacitance of about several tens to 200 picofarads (pF). 
     Hereinafter, the operation of the liquid lens  142  configured as described above will be described in detail. 
     The first connection substrate  144  and the second connection substrate  146  serve to supply a driving voltage for driving the liquid lens  142  to the first and second electrodes E 1  and E 2 , respectively. When the driving voltage is applied to the first and second electrodes E 1  and E 2  through the first connection substrate  144  and the second connection substrate  146 , the interface BO between the first liquid LQ 1  and the second liquid LQ 2  may be deformed, and at least one of the shape, such as the curvature, the focal length, or the tilting angle of the liquid lens  142  may be changed (or adjusted). For example, the focal length of the liquid lens  142  may be adjusted with a change in at least one of the flexure or the inclination of the interface BO formed in the liquid lens  142  according to the driving voltage. In this manner, when the deformation, the radius of curvature, and the tilting angle of the interface BO are controlled, the camera module  100  including the liquid lens  142  may perform the auto-focusing (AF) function and the hand-tremor compensation or optical image stabilization (OIS) function. 
     For example, the first connection substrate  144  may respectively transmit four different individual voltages, namely first to fourth individual voltages, to the first to fourth individual electrodes E 1 , E 12 , E 13 , and E 14  of the liquid lens  142 , and the second connection substrate  146  may transmit one common voltage to the common electrode E 2  of the liquid lens  142 . The common voltage may include DC voltage or AC voltage. When the common voltage is applied in the form of a pulse, the width or duty cycle of the pulse may be constant. 
     Although not shown, a conductive epoxy may be disposed between the first connection substrate  144  and the plurality of first electrodes E 1  so that the first connection substrate  144  and the plurality of first electrodes E 1  are in contact with, coupled to, and electrically connected to each other. In addition, a conductive epoxy may be disposed between the second connection substrate  146  and the second electrode E 2  so that the second connection substrate  146  and the second electrode E 2  are in contact with, coupled to, and electrically connected to each other. 
     Hereinafter, the liquid lens control device  200  according to the embodiment will be described with reference to the accompanying drawings. The following description will be made on the assumption that the number of the plurality of individual electrodes E 1  is four, but the embodiments are not limited thereto. That is, the following description may also apply to the case in which the number of the plurality of individual electrodes E 1  is greater than or less than four. 
       FIG. 4  is a block diagram of a camera module  100 A according to an embodiment. 
     The camera module  100 A shown in  FIG. 4  may correspond to the embodiment of the camera module  100  shown in  FIG. 1 , and may include a liquid lens control device  200  and a liquid lens  300 . 
     The liquid lens control device  200  shown in  FIG. 4  may include a controller  210 , a driving voltage generator  220 , and a compensator  230 . Although the compensator  230  is illustrated as being a separate component, the same may be included in the controller  210 . 
     The liquid lens control device  200  serves to control the liquid lens  300 , which operates in response to a driving signal. Here, the liquid lens  300  may correspond to the liquid lens  142  shown in  FIGS. 2, 3 ( a ), and  3 ( b ) described above, but the embodiments are not limited thereto. That is, according to another embodiment, the liquid lens control device  200  according to the embodiment may also control a liquid lens configured differently from the liquid lens  142  shown in  FIGS. 2, 3 ( a ), and  3 ( b ). 
     The capacitors C 1 , C 2 , C 3 , and C 4  included in the liquid lens  300  shown in  FIG. 4  respectively correspond to the capacitors C 1 , C 2 , C 3 , and C 4  shown in  FIG. 3( b ) , and the resistors R 1  to R 8  correspond to the parasitic resistors of the liquid lens  300 . 
     Hereinafter, for better understanding, the liquid lens  300 , which is controlled by the liquid lens control device  200  according to the embodiment, will be described as being the liquid lens  142  shown in  FIGS. 2, 3 ( a ), and  3 ( b ). Also, although not shown in  FIG. 4 , the common voltage may be supplied from the liquid lens control device  200  to the liquid lens  300 . 
     The driving voltage generator  220  may generate individual voltages to be respectively provided to the plurality of individual electrodes E 11 , E 12 , E 13 , and E 14  in response to the control signal output from the controller  210 , and may output the generated individual voltages to the compensator  230 . Also, although not shown, the compensator  230  may perform compensation operation in front of the controller  210 , and may output a compensation signal to the controller  210 . Alternatively, the compensator  230  may be disposed between the controller  210  and the driving voltage generator  220  to compensate for the signal received from the controller  210 , and may output a compensation signal to the driving voltage generator  220 . The compensator  230  may perform compensation between the controller  210  and an ADC sensor, and may output a compensation signal to the controller  210 . Alternatively, the compensator  230  may be included in the controller  210 . 
     To this end, the driving voltage generator  220  may include a plurality of individual voltage generators, for example, first to fourth individual voltage generators  222  to  228 . 
     The first individual voltage generator  222  may generate a first individual voltage to be provided to the first individual electrode E 11  in response to the control signal output from the controller  210 , and may output the generated first individual voltage to the compensator  230 . The second individual voltage generator  224  may generate a second individual voltage to be provided to the second individual electrode E 12  in response to the control signal output from the controller  210 , and may output the generated second individual voltage to the compensator  230 . The third individual voltage generator  226  may generate a third individual voltage to be provided to the third individual electrode E 13  in response to the control signal output from the controller  210 , and may output the generated third individual voltage to the compensator  230 . The fourth individual voltage generator  228  may generate a fourth individual voltage to be provided to the fourth individual electrode E 14  in response to the control signal output from the controller  210 , and may output the generated fourth individual voltage to the compensator  230 . 
     Also, the compensator  230  may perform compensation (ADC gain compensation) on the signal output from the ADC sensor, and the controller  210  may control the driving voltage generator  220  in response to the compensated signal. Also, the signal output from the controller  210  may be compensated for by the compensator  230  so as to be used to control the driving voltage generator  220 . 
     The individual voltages output from, the driving voltage generator  220  may be pulse-type voltages having a predetermined width, which are applied to the respective individual electrodes of the liquid lens  300 . The driving voltage applied to the liquid lens  300  is the difference between the voltage applied to each of the plurality of individual electrodes E 11 , E 12 , E 13 , and E 14  and the voltage applied to the common electrode E 2 . 
     Although not shown, the driving voltage generator  220  may further include at least one of a voltage booster (not shown), a voltage stabilizer (not shown), or a switching unit (not shown). The voltage booster serves to increase the magnitude of voltage that is supplied, and the voltage stabilizer serves to stabilize the output from the voltage booster. In addition, the switching unit serves to selectively supply the output from the voltage booster to each terminal of the liquid lens  300 . Here, the switching unit may include a circuit structure called an H bridge. The high voltage output from the voltage booster may be applied to the switching unit as a power supply voltage. The switching unit may selectively supply the applied power supply voltage and a reference potential (e.g. a ground voltage) across the two ends of the liquid lens  300 . The two ends of the liquid lens  300  may respectively be any one of the plurality of individual electrodes (e.g. E 11 , E 12 , E 13 , and E 14 ) and the second electrode E 2 . 
     Meanwhile, the controller  210  may have a configuration for performing the AF function and the OIS function, and may control the liquid lens  300  included in the lens assembly  22  in response to a user request or a result of sensing (e.g. a motion signal of a gyro sensor (not shown) or the like). 
     In addition, the controller  210  may receive information (i.e. information about the distance to an object) for performing the AF function from the inside (e.g. the image sensor  26 ) or the outside (e.g. a distance sensor or an application processor) of the optical device or the camera module  100  or  100 A, may calculate a driving voltage corresponding to the shape that the liquid lens  300  needs to have according to the focal length for focusing the lens on the object using the distance information, and may generate a control signal based thereon. 
     In addition, the controller  210  may output a control signal using a motion signal of the liquid lens or the optical device including the liquid lens, which is output from the gyro sensor, and may output the output control signal to the driving voltage generator  220 . 
     Although not shown, in order to implement the OIS function, the controller  210  may further include a low-pass filter (LPF) (not shown). The LPF may extract only a desired band by removing a high-frequency noise component from a motion signal output from the gyro sensor, may calculate the amount of hand tremor using the denoised motion signal, may calculate a driving voltage corresponding to the shape that the liquid lens  300  needs to have in order to compensate for the calculated amount of hand tremor, and may generate a control signal based thereon. 
     Hereinafter, the configuration and operation of the controller  210  of the liquid lens control device  200  according to the embodiment will be described with reference to the accompanying drawings. 
       FIG. 5  is a graph showing information corresponding to the position of the liquid interface with respect to the individual voltages applied to the individual electrodes (e.g. a value obtained by performing analog-to-digital conversion (ADC) on the capacitance value corresponding to the liquid lens interface or the capacitance value between each individual electrode and the common electrode) before correcting variation in the liquid interface or the ADC value corresponding to the liquid interface according to the voltage applied to each individual electrode.  FIG. 6  is a graph showing information corresponding to the position of the liquid interface with respect to the individual voltages (e.g. a value obtained by performing ADC on the capacitance value corresponding to the liquid lens interface or the capacitance value between each individual electrode and the common electrode) after correcting variation in the liquid interface or the value (e.g. the ADC value) corresponding to the liquid interface according to the voltage applied to each individual electrode. In each graph, the horizontal axis represents the effective value of the individual voltage, and the vertical axis represents the ADC value of the capacitance corresponding to the liquid interface. In each of  FIGS. 5 and 6 , each of the effective value of the individual voltage and the ADC value may take the form of code. 
     The controller  210  may calculate a plurality of first slopes, each of which is the slope of the ADC value corresponding to the position of the liquid interface BO of the liquid lens  300  with respect to the individual voltage applied to each of the plurality of individual electrodes E 11 , E 12 , E 13 , and E 14 . For example, the controller  210  may acquire the graph shown in  FIG. 5 . 
     To this end, the camera module  100 A may further include an ADC sensor  400 . The ADC sensor  400  is illustrated in  FIG. 4  as being disposed outside the liquid lens control device  200  or separately therefrom. However, according to another embodiment, the ADC sensor  400  may belong to the liquid lens control device  200  or the controller  210 . 
     The ADC sensor  400  senses an ADC value corresponding to the position of the liquid interface BO of the liquid lens  300  for each individual electrode, and outputs the result of sensing to the controller  210 . For example, the ADC sensor  400  may apply a voltage across the two ends of the insulating layer  148  shown in  FIG. 2 , may sense the capacitance values of the capacitors C 1  to C 4  shown in  FIG. 3( b ) , and may sense the ADC value for each individual voltage. Only one ADC sensor  400  may be provided. When a single ADC sensor  400  is provided, the ADC sensor  400  may convert the ADC values received from the plurality of individual electrodes into a representative value, and may output the representative value. The representative value may be, for example, a value corresponding to the average of capacitance or ADC values of the individual electrodes. Also, when a single ADC sensor  400  is provided, the ADC sensor  400  may acquire the capacitance of the liquid lens from the common electrode at a time. Alternatively, the ADC sensor  400  may be provided in a plural number. For example, the number of ADC sensors  400  may correspond to the number of the plurality of individual electrodes. In this case, each of the ADC sensors  400  may acquire a capacitance value corresponding to a respective one of the individual electrodes. 
     For example, referring to  FIG. 5 , when the first to fourth individual voltages are respectively applied to the first to fourth individual electrodes E 11 , E 12 , E 13 , and E 14 , the capacitance value of each of the individual electrodes may vary. Variation may occur for various reasons. For example, variation may occur due to structural tolerance in components (the electrodes, the insulating layer, etc.) of the liquid lens, which occurs during processing. Variation in each individual electrode makes it difficult to accurately control the liquid lens. Therefore, the embodiment uses the compensator for compensating for variation in the liquid interface according to application of voltage to each individual electrode, thereby more accurately controlling the liquid lens  300 . 
       FIG. 4  shows an embodiment in which a single compensator  230  compensates values output from a plurality of individual voltage generators. The deviation between the plurality of individual voltages may be compensated for by the compensator  230 , and the compensated individual voltages may be applied to the liquid lens  300 . Although not shown, a single compensator  230  may be located in front of the controller  210 , between the individual voltage generators and the controller  210 , or between the ADC sensor  400  and the controller  210 . Alternatively, the compensator  230  may be included in the controller  210 . 
     An embodiment of compensation method will be described with reference to  FIGS. 5 to 7 . Referring to  FIG. 5 , when the first to fourth individual voltages are respectively applied to the first to fourth individual electrodes E 11 , E 12 , E 13 , and E 14 , the compensator  230  or the controller  210  may calculate a first slope S 1  of the ADC value for the first individual voltage (hereinafter referred to as a “1−1 st  slope”), may calculate a first slope S 2  of the ADC value for the second individual voltage (hereinafter referred to as a “1−2 nd  slope”), may calculate a first slope S 3  of the ADC value for the third individual voltage (hereinafter referred to as a “1−3 rd  slope”), and may calculate a first slope S 4  of the ADC value for the fourth individual voltage (hereinafter referred to as a “1−4 th  slope”). 
     Each S of the 1−1 st  to 1−4 th  slopes S 1  to S 4  may be expressed using Equation 1 below. 
         S =( ADCm−ADCi )/( VLm−VLi )   [Equation 1]
 
     Here, ADCm represents a value corresponding to the ADC value at a macro position, VLm represents a value corresponding to the individual voltage at the macro position, ADCi represents a value corresponding to the ADC value at an infinite position, and VLi represents a value corresponding to the individual voltage at the infinite position. 
     Referring to Equation 1, it can be seen that the first slope S is a slope between the infinite position i and the macro position m. 
     According to the embodiment, the compensator  230  may perform an operation of calculating a plurality of first slopes in response to a power-on signal or an application-on signal. Here, the power-on signal may be a signal for supplying operating power of the camera module  100 A, and the application-on signal may be a signal that is generated when it is desired to correct deviation between the first slopes for each individual electrode in the camera module  100 A. 
     Also, the compensator  230  may calculate a reference slope using at least two of the plurality of first slopes S 1  to S 4 . 
     For example, the compensator  230  may calculate the average value of the plurality of first slopes S 1  to S 4  as a reference slope (hereinafter referred to as a “first reference slope”). The first reference slope may be expressed using Equation 2 below. 
         RS 1=Average( S 1, S 2, S 3, S 4)   [Equation 2]
 
     Here, RS1 represents the first reference slope, and Average (S 1 , S 2 , S 3 , S 4 ) represents the average value of S 1  to S 4 . 
     Also, the compensator  230  may correct at least one first slope (hereinafter referred to as a “correction target slope”) among the plurality of first slopes S 1  to S 4  based on the reference slope. 
     For example, as shown in Equation 3 below, the absolute values D1 to D4 of the difference between the 1−1 st  to 1−4 th  slopes S 1  to S 4  and the first reference slope RS1 may be obtained, and a slope corresponding to an absolute value larger than a predetermined value (e.g. 1.0) among the absolute values may be determined to be the correction target slope. 
         D 1 =ABS ( RS 1− S 1)
 
         D 2 =ABS ( RS 1− S 2)
 
         D 3 =ABS ( RS 1− S 3)
 
         D 4 =ABS ( RS 1− S 4)   [Equation 3]
 
     Here, D1 represents the absolute value ABS of the difference between the 1−1 st  slope S 1  and the first reference slope RS1, D2 represents the absolute value ABS of the difference between the 1−2 nd  slope S 2  and the first reference slope RS1, D3 represents the absolute value ABS of the difference between the 1−3 rd  slope S 3  and the first reference slope RS1, and D4 represents the absolute value ABS of the difference between the 1−4 th  slope S 4  and the first reference slope RS1. 
     As described above, at least one first slope among the plurality of first slopes S 1  to S 4  may become the correction target slope. One of the correction target slopes may be the slope having the largest deviation from the reference slope (e.g. the first reference slope) (hereinafter referred to as a “maximally deviating slope”). 
     According to an embodiment, the maximally deviating slope may be any one of two first slopes, the difference (value) between the two neighboring ADC values of which is the largest at the macro position. Referring to  FIG. 5 , when the difference between the two neighboring ADC values of the 1−1 st  slope S 1  and the 1−2 nd  slope S 2  is referred to as a “first difference”, when the difference between the two neighboring ADC values of the 1−2 nd  slope S 2  and the 1−3 rd  slope S 3  is referred to as a “second difference”, and when the difference between the two neighboring ADC values of the 1−3 rd  slope S 3  and the 1−4 th  slope S 4  is referred to as a “third difference”, the third difference the largest among the first to third differences. Accordingly, the maximally deviating slope may be any one of the 1−3 rd  and 1−4 th  slopes S 3  and S 4 , for example, the 1−4 th  slope S 4 . 
     According to another embodiment, among the 1−1 st  to 1−4 th  slopes S 1  to S 4 , the maximally deviating slope may be the slope that is used for calculation of the largest value among D1 to D4 shown in Equation 3. In the case shown in 
       FIG. 5 , since D4 is the largest among D1 to D4, the 1−4 th  slope S 4 , which is used for calculation of D4, may be determined to be the maximally deviating slope. 
     The compensator  230  may calculate the average value of the first slopes other than the maximally deviating slope, among the plurality of first slopes S 1  to S  4 , as a reference slope (hereinafter referred to as a “second reference slope”). Alternatively, the compensator  230  may calculate the average value of slopes other than the correction target slope (hereinafter referred to as “non-corrected slopes”) among the plurality of first slopes S 1  to S 4  as the second reference slope. The second reference slope may be expressed using Equation 4 below. 
         RS 2=Average( TS _ EX _ SM )   [Equation 4]
 
     Here, RS2 represents the second reference slope, and Average (TS_EX_SM) represents the average value of the non-corrected slopes. 
     In addition, the correction target slope may be corrected as shown in Equation 5 below. 
         G=W×F    [Equation 5]
 
     Here, G represents a slope obtained by correcting the correction target slope, W represents a weight for realizing a theoretical value, and F may be expressed using Equation 6 below. 
         F=f×CS    [Equation 6]
 
     Here, f is expressed using Equation 7 below, and CS represents the correction target slope. 
     
       
         
           
             
               
                 
                   f 
                   = 
                   
                     
                       RS 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                     
                     CS 
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     7 
                   
                   ] 
                 
               
             
           
         
       
     
     According to the embodiment, the compensator  230  may correct the ADC value at the macro position of the individual electrode having the maximally deviating slope using the reference slope. 
     For example, the ADC value VA 1  at the macro position of the maximally deviating slope S 4  shown in  FIG. 5  may be increased in the direction of the arrow to the ADC value VA 2  at the macro position of the maximally deviating slope S 4  shown in  FIG. 6 . In this manner, the maximally deviating slope S 4  may be corrected. 
     Hereinafter, an embodiment  230 A of the compensator  230  for correcting the correction target slope will be described with reference to  FIG. 7 . In addition, in order to help understanding the operation of correcting the correction target slope by the compensator  230 , it is assumed that S 1 , S 2 , S 3 , and S 4  shown in  FIG. 5  are, respectively, 4, 4.2, 4.4, and 2.2 and that the predetermined value is “1”. 
       FIG. 7  is a block diagram of an embodiment  230 A of the compensator  230  shown in  FIG. 5 . 
     The compensator  230 A shown in  FIG. 7  may include a first slope calculator  211 , a first reference slope calculator  212 , a slope comparator  214 , a slope selector  215 , a second reference slope calculator  216 , a slope corrector  217 , and a control signal generator  218 . 
     The first slope calculator  211  may calculate a plurality of first slopes (e.g. S 1  to S 4 ) using the ADC values for the individual voltages, which are output from the ADC sensor  400  and received through an input terminal IN. 
     The first reference slope calculator  212  calculates the first reference slope RS1 expressed in Equation 2 above using the plurality of first slopes S 1  to S 4  output from the first slope calculator  211 , and outputs the calculated first reference slope RS1, which is “3.7”, to the slope comparator  214 . 
     The slope comparator  214  calculates D1, D2, D3, and D4, expressed in Equation 3, using the plurality of first slopes S 1  to S 4  output from the first slope calculator  211  and the first reference slope RS1 output from the first reference slope calculator  212 , and outputs the calculated and D4, which are, respectively, 0.3, 0.5, 0.7, and 1.5, to the slope selector  215 . 
     The slope selector  215  compares each of D1 to D4 with the predetermined value, e.g. 1, selects a value larger than 1 from among D1 to D 4, i.e. the 1−4 th  slope S 4  used to calculate D4, as the correction target slope, outputs the selected correction target slope to the slope corrector  217 , and outputs a non-corrected slope to the second reference slope calculator  216 . 
     The second reference slope calculator  216  calculates the second reference slope RS2 expressed in Equation 4 using the non-corrected slope output from the slope selector  215 , and outputs the calculated second reference slope RS2, which is 4.2, to the slope corrector  217 . 
     Thereafter, the slope corrector  217  obtains f (1.91=4.2/2.2), expressed in Equation 7, using S 4 , which is the correction target slope CS output from the slope selector  215 , and the second reference slope RS2 output from the second reference slope calculator  216 , and calculates F (4.2=1.91×2.2), expressed in Equation 6, using f and S 4 , which is the correction target slope CS. Thereafter, when the weight W is “1”, the slope corrector  217  outputs 4.2, which is the slope G obtained by correcting the correction target slope S 4 , to the control signal generator  218  instead of S 4 . 
     The control signal generator  218  generates a control signal using S 1  to S 3  and 4.2, which is the corrected slope G, in place of S 4 , and outputs the generated control signal to the driving voltage generator  220  through an output terminal OUT. 
     Thereafter, the driving voltage generator  220  may generate plurality of individual voltages to be respectively supplied to the plurality of individual electrodes E 11 , E 12 , E 13 , and E 14  in response to the control signal, which is output from the controller  210  or the compensator  230  and is generated based on the result G of correcting the correction target slope. That is, in response to the control signal, the driving voltage generator  220  compensates the individual voltages according to the extent to which the ADC values change, and outputs the compensated individual voltages to the compensator  230 . 
     The driving voltage generator  220  may include a first driving voltage generator and a second driving voltage generator. The first driving voltage generator may generate an individual voltage to be applied to the individual electrode having the corrected correction target slope, among the plurality of first slopes, and the second driving voltage generator may generate individual voltages to be applied to the individual electrodes having the non-corrected slopes, other than the correction target slope, among the plurality of first slopes. In the example shown in  FIGS. 5 and 6  described above, the fourth individual voltage generator  228  corresponds to the first driving voltage generator, and the first to third individual voltage generators  222  to  226  correspond to the second driving voltage generator. 
     Meanwhile, referring again to  FIG. 4 , the compensator  230  may multiply the plurality of individual voltages, which are generated by the first and second driving voltage generators, by the same compensation gain, and may apply the result thereof to the plurality of individual electrodes of the liquid lens  300 . 
     Hereinafter, a liquid lens control device according to another embodiment will be described with reference to the accompanying drawings. 
       FIG. 8  is a block diagram of a camera module according to another embodiment, which includes a liquid lens control device  20 , a liquid lens  300 , and an ADC sensor  400 . 
     The liquid lens  300  and the ADC sensor  400  shown in  FIG. 8  are the same as the liquid lens  300  and the ADC sensor  400  shown in  FIG. 4 , respectively. Thus, the same parts are denoted by the same reference numerals, and a duplicate description thereof will be omitted. 
     The liquid lens control device  20  according to the embodiment includes controller  40 , a driving voltage generator  50 , and first to fourth compensators  62  to  68 . 
     The driving voltage generator  50  generates a plurality of individual voltages to be supplied to the plurality of individual electrodes E 11 , E 12 , E 13 , and E 14  in response to the control signal output from the controller  40 . To this end, the driving voltage generator  50  includes first to fourth individual voltage generators  52  to  58 . Here, the first to fourth individual voltage generators  52  to  58  perform the same functions as the first to fourth individual voltage generators  222  to  228  shown in  FIG. 4 , respectively. 
     The controller  40  of the liquid lens control device according to the embodiment may not correct the correction target slope. Accordingly, the controller  40  generates a control signal using the 1−1 st  to 1−4 th  slopes S 1  to S 4 , which are different from each other, and the driving voltage generator  50  generates a plurality of individual voltages in response to the control signal. Although not shown, the compensators may be disposed between the controller  40  and the respective individual voltage generators, and may compensate the signal from the controller  40 , thereby compensating for the deviation of each individual electrode. 
     In general, when the ADC values have large variation and are different from each other, individual voltages need to be generated so as to be suitable for the characteristics of the respective individual electrodes in order to secure spatial frequency response (SFR) and OIS performance. However, when only a single compensator is used to generate a plurality of individual voltages, SFR and OIS performance may be deteriorated. In order to prevent this, the liquid lens control device  50  according to the embodiment includes the plurality of first to fourth compensators  62  to  68 . The first to fourth compensators  62  to  68  multiply the plurality of individual voltages, which may be different from each other, by different compensation gains, thereby compensating the correction target slope, among the plurality of first slopes S 1  to S 4 . 
     Although only a limited number of embodiments have been described above, various other embodiments are possible. The technical contents of the above-described embodiments may be combined into various forms as long as they are not incompatible with one another, and thus may be implemented in new embodiments. 
     An optical device may be implemented using the camera module  100  or  100 A including the liquid lens control device  200  according to the embodiments described above. Here, the optical device may include a device that may process or analyze optical signals. Examples of the optical device may include camera/video devices, telescopic devices, microscopic devices, an interferometer, a photometer, a polarimeter, a spectrometer, a reflectometer, an auto-collimator, and a lens-meter, and the embodiments may be applied to optical devices that may include the lens assembly. 
     In addition, the optical device may be implemented in a portable device such as, for example, a smartphone, a laptop computer, or a tablet computer. Such an optical device may include the camera module  100  or  100 A, a display (not shown) configured to output an image, a battery (not shown) configured to supply power to the camera module  100  or  100 A, and a body housing in which the camera module  100  or  100 A, the display, and the battery are mounted. The optical device may further include a communication module capable of communicating with other devices and a memory unit capable of storing data. The communication module and the memory unit may also be mounted in the body housing. 
     It will be apparent to those skilled in the art that various changes in form and details may be made without departing from the spirit and the essential characteristics of the disclosure set forth herein. Accordingly, the above detailed description is not intended to be construed as limiting the disclosure in all aspects and to be considered by way of example. The scope of the disclosure should be determined by reasonable interpretation of the accompanying claims, and all equivalent modifications made without departing from the disclosure should be included in the scope of the disclosure. 
     Mode for Invention 
     Various embodiments have been described in the best mode for carrying out the disclosure. 
     INDUSTRIAL APPLICABILITY 
     A liquid lens control device according to the embodiments may be used in camera/video devices, telescopic devices, microscopic devices, an interferometer, a photometer, a polarimeter, a spectrometer, a reflectometer, an auto-collimator, a lens-meter, a smartphone, a laptop computer, a tablet computer, etc.