KR102310998B1 - Camera module and method for controlling liquid lens - Google Patents

Abstract

The camera module of the present invention includes: a plate including a cavity in which a conductive liquid and a non-conductive liquid are disposed, a liquid lens including a common electrode disposed on the plate and a plurality of individual electrodes disposed below the plate; a lens holder including a solid lens disposed above or below the liquid lens; a sensor substrate disposed under the lens holder and on which an image sensor is disposed; a control unit disposed on the sensor substrate and controlling a driving voltage supplied between the common electrode and a plurality of individual electrodes; and a connection part electrically connecting the plurality of individual electrodes or the common electrode and the sensor substrate, wherein when the camera module is driven for a predetermined time, the resolution of the camera module is dependent on regulating the driving voltage applied to the liquid lens. It has a section that decreases and then increases.

Description

CAMERA MODULE AND METHOD FOR CONTROLLING LIQUID LENS

The present invention relates to a liquid lens and a camera module and optical device including the same. More specifically, the present invention relates to a camera module including a lens capable of adjusting a focal length using electrical energy.

Users of portable devices want optical devices that have high resolution, are small in size, and have various shooting functions (eg, Auto-Focusing (AF) function, image stabilization or Optical Image Stabilizer (OIS) function, etc.) are doing Such a photographing function may be implemented through a method of directly moving a lens by combining a plurality of lenses, but if the number of lenses is increased, the size of the optical device may increase. Autofocus and image stabilization are performed by moving or tilting multiple lens modules fixed to the lens holder and aligned with the optical axis in the vertical direction of the optical axis or optical axis, and driving a separate lens to drive the lens module device is used. However, the lens driving device consumes high power, and in order to protect it, a cover glass must be added separately from the camera module, so the overall thickness is increased.

Therefore, research on a liquid lens that performs autofocus and image stabilization functions by electrically controlling the curvature of the interface between two liquids is being conducted.

In a camera module including a lens capable of adjusting the position of an interface located between two liquids according to electrical energy, the present invention provides It is possible to provide a driving circuit and a lens control method of a lens capable of compensating for a change in diopter (diopter).

In addition, the present invention is a liquid lens in which the degree of curvature and bias of the interface formed by the two liquids included in the lens is adjusted according to the supply voltage, the resolution of the lens is lowered by the thermal expansion coefficient according to the temperature change In order to overcome this tendency, we will provide a camera module that can adjust the driving voltage that can adjust the movement of the interface formed by the two liquids in response to the change in spatial frequency response (SFR) according to the temperature change of the liquid lens. can

In addition, the present invention is a camera module capable of outputting a driving voltage capable of compensating for a change in diopter according to the temperature of the liquid lens without a temperature sensor measuring the temperature change of the liquid included in the liquid lens of the camera module. can provide

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention belongs from the description below. will be able

A camera module according to an embodiment of the present invention includes a plate including a cavity in which a conductive liquid and a non-conductive liquid are disposed, a liquid lens including a common electrode disposed on the plate and a plurality of individual electrodes disposed below the plate; a lens holder including a solid lens disposed above or below the liquid lens; a sensor substrate disposed under the lens holder and on which an image sensor is disposed; a control unit disposed on the sensor substrate and controlling a driving voltage supplied between the common electrode and a plurality of individual electrodes; and a connection part electrically connecting the plurality of individual electrodes or the common electrode and the sensor substrate, wherein when the camera module is driven for a predetermined time, the resolution of the camera module is dependent on regulating the driving voltage applied to the liquid lens. It may have a section that decreases and then increases.

Also, in the period, when a preset time is reached from the time of the preset operation by the controller, the level of the driving voltage may be adjusted by a preset level.

In addition, the preset operation time point may be a time point when power is applied to the image sensor or the control unit, or a time point at which the control unit focuses on a specific object in an image acquired through the image sensor.

Also, the preset period may be within 520 seconds.

Also, the controller may decrease the driving voltage by the preset level.

In addition, the control unit may control the driving voltage in response to n-bit (n is a natural number) data corresponding to temperature, and decrease the driving voltage by the n-bit specific code when the preset time elapses.

In addition, the controller may differently supply the driving voltage to each of the plurality of individual electrodes to compensate for shake.

In addition, the camera module further includes a gyro sensor that detects the movement of the camera module and outputs a detection signal corresponding to the movement, wherein the controller includes the detection signal and the temperature change of the camera module or the liquid lens In response, the level of the driving voltage may be determined.

A liquid lens control method according to another embodiment of the present invention is a camera module including a liquid lens including one common electrode and four individual electrodes to adjust the interface formed by two liquids, detecting a preset operation time; supplying a driving voltage corresponding to the preset operation; and adjusting the driving voltage by a preset level when a preset time elapses after the driving voltage is supplied.

Aspects of the present invention are only some of the preferred embodiments of the present invention, and various embodiments in which the technical features of the present invention are reflected are detailed descriptions of the present invention that will be described below by those of ordinary skill in the art can be derived and understood based on

The effect on the device according to the present invention will be described as follows.

The present invention may provide a control circuit and a control method capable of reducing a decrease in resolution or increasing resolution when a temperature change of a liquid lens in a camera module occurs due to heat generation of an image sensor or the like.

In addition, the present invention can reduce a distortion coefficient according to temperature in a lens assembly composed of a plurality of lenses including a liquid lens, so that auto focus (AF) and optical image stabilization (OIS) of the camera module can be reduced. ) can improve performance.

Effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those of ordinary skill in the art from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are provided to help understanding of the present invention, and provide embodiments of the present invention together with detailed description. However, the technical features of the present invention are not limited to specific drawings, and features disclosed in each drawing may be combined with each other to form a new embodiment.
1 illustrates a camera module.
2 illustrates a lens assembly comprising a liquid lens.
3A and 3B illustrate a liquid lens.
4 illustrates the structure of a liquid lens.
5A and 5B explain why the diopter (diopter) changes in the liquid lens according to the temperature change.
6A and 6B illustrate a diopter (diopter) change amount of a liquid lens according to a change in temperature.
7A and 7B illustrate a method of measuring a spatial resolution change of a liquid lens according to a change in temperature.
8A and 8B illustrate the spatial resolution change of the liquid lens according to the temperature change.
Fig. 9 explains the determination of the compensation value of the liquid lens according to the temperature change.
10 illustrates a camera module.
11 illustrates a control circuit in the camera module.
Fig. 12 explains the control method of the liquid lens.

Hereinafter, an embodiment will be described in detail with reference to the accompanying drawings. Since the embodiment may have various changes and may have various forms, specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the embodiment to a specific disclosed form, and it should be understood to include all modifications, equivalents, and substitutions included in the spirit and scope of the embodiment.

Terms such as “first” and “second” may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used for the purpose of distinguishing one component from another. In addition, terms specifically defined in consideration of the configuration and operation of the embodiment are only for describing the embodiment, and do not limit the scope of the embodiment.

In the description of the embodiment, in the case where it is described as being formed "on or under" of each element, above (above) or below (below) ( on or under includes both elements in which two elements are in direct contact with each other or in which one or more other elements are disposed between the two elements indirectly. In addition, when expressed as "up (up)" or "down (on or under)", the meaning of not only the upward direction but also the downward direction based on one element may be included.

Further, as used hereinafter, relational terms such as "upper/upper/above" and "lower/lower/below" etc. do not necessarily require or imply any physical or logical relationship or order between such entities or elements, It may be used to distinguish one entity or element from another entity or element.

1 illustrates an example of a camera device. As shown, the camera module may include a lens assembly 22 and an image sensor. The lens assembly 22 may include a liquid lens whose focal length is adjusted in response to an applied voltage. The camera module includes a lens assembly 22 including a plurality of lenses including a first lens whose focal length is adjusted in response to a driving voltage applied between a common terminal and a plurality of individual terminals, and a driving voltage applied to the first lens. It may include a control circuit 24 for supplying, and an image sensor 26 arranged in the lens assembly 22 and converting the light transmitted through the lens assembly 22 into an electrical signal.

Referring to FIG. 1 , the camera module may include circuits 24 and 26 formed on one printed circuit board (PCB) and a lens assembly 22 including a plurality of lenses, but this is only one example. However, it does not limit the scope of the invention. The configuration of the control circuit 24 may be designed differently according to specifications required for the camera module. In particular, when the magnitude of the voltage applied to the liquid lens 28 is reduced, the control circuit 24 may be implemented as a single chip. Through this, the size of the camera module mounted on the portable device can be further reduced.

Referring to FIG. 2 , as shown, the lens assembly 22 includes a first lens unit 100 , a second lens unit 200 , a liquid lens unit 300 , a lens holder 400 , and a connection unit 500 . may include. The connection unit 500 electrically connects the image sensor and the liquid lens, and may include a substrate, wire, or electric wire, which will be described later. The illustrated structure of the lens assembly 22 is only one example, and the structure of the lens assembly 22 may vary according to specifications required for the camera module. For example, in the illustrated example, the liquid lens unit 300 is positioned between the first lens unit 100 and the second lens unit 200 , but in another example, the liquid lens unit 300 includes the first lens unit ( 100) may be located above (front), and either the first lens unit 100 or the second lens unit 200 may be omitted. The configuration of the control circuit 24 may be designed differently according to specifications required for the camera device. In particular, when the level of the operating voltage applied to the lens assembly 22 is reduced, the control circuit 24 may be implemented as a single chip. Through this, the size of the camera device mounted on the portable device can be further reduced.

2 illustrates an example of a lens assembly 22 included in a camera device.

As shown, the lens assembly 22 may include a first lens unit 100 , a second lens unit 200 , a liquid lens unit 300 , a lens holder 400 , and a connection unit 500 . The connection unit 500 electrically connects the image sensor and the liquid lens, and may include a substrate, wire, or electric wire, which will be described later. The illustrated structure of the lens assembly 22 is only one example, and the structure of the lens assembly 22 may vary according to specifications required for the camera module. For example, in the illustrated example, the liquid lens unit 300 is positioned between the first lens unit 100 and the second lens unit 200 , but in another example, the liquid lens unit 300 includes the first lens unit ( 100) may be located above (front), and either the first lens unit 100 or the second lens unit 200 may be omitted.

Referring to FIG. 2 , the first lens unit 100 is disposed in front of the lens assembly, and is a portion where light is incident from the outside of the lens assembly. The first lens unit 100 may be provided as at least one lens, or two or more lenses may be aligned with respect to the central axis PL to form an optical system.

The first lens unit 100 and the second lens unit 200 may be mounted on the lens holder 400 . In this case, a through hole may be formed in the lens holder 400 , and the first lens unit 100 and the second lens unit 200 may be disposed in the through hole. In addition, the liquid lens unit 300 may be inserted into the space between the first lens unit 100 and the second lens unit 200 in the lens holder 400 .

Meanwhile, the first lens unit 100 may include a solid lens 110 . The solid lens 110 may protrude to the outside of the lens holder 400 and be exposed to the outside. When a solid lens is exposed, the lens surface may be damaged due to exposure to the outside. If the lens surface is damaged, the image quality of the image taken by the camera module may be deteriorated. In order to prevent and suppress surface damage of the solid lens 110, a method of disposing a cover glass or forming a coating layer or forming the solid lens 100 with a wear-resistant material to prevent surface damage may be applied.

The second lens unit 200 is disposed behind the first lens unit 100 and the liquid lens unit 300 , and light incident to the first lens unit 100 from the outside passes through the liquid lens unit 300 . Thus, it may be incident to the second lens unit 200 . The second lens unit 200 may be spaced apart from the first lens unit 100 and disposed in a through hole formed in the lens holder 400 .

Meanwhile, the second lens unit 200 may be provided as at least one lens, and when two or more lenses are included, the optical system may be formed by aligning the second lens unit 200 based on the central axis PL.

The liquid lens unit 300 is disposed between the first lens unit 100 and the second lens unit 200 , and may be inserted into the insertion hole 410 of the lens holder 400 . The insertion hole 410 may be formed by opening a portion of the side surface of the lens holder. That is, the liquid lens may be inserted and disposed through the insertion hole 410 on the side of the holder. The liquid lens unit 300 may also be aligned with the central axis PL like the first lens unit 100 and the second lens unit 200 .

The liquid lens unit 300 may include a lens region 310 . The lens region 310 is a portion through which the light passing through the first lens unit 100 transmits, and at least a portion thereof may include a liquid. For example, the lens region 310 may include two types, namely, a conductive liquid and a non-conductive liquid, and the conductive liquid and the non-conductive liquid may form an interface without being mixed with each other. . The interface between the conductive liquid and the non-conductive liquid is deformed by the driving voltage applied through the connection part 500 , so that the curvature of the interface of the liquid lens 28 or the focal length of the liquid lens may be changed. When the boundary surface deformation and curvature change are controlled, the liquid lens unit 300 and the camera module including the same may perform an auto-focusing function, a hand-shake correction function, and the like.

3 illustrates a liquid lens whose focal length is adjusted in response to a driving voltage. Specifically, (a) describes the first lens 28 included in the lens assembly 22 (refer to FIG. 2), and (b) describes the equivalent circuit of the lens 28. As shown in FIG.

First, referring to (a), the lens 28 whose focal length is adjusted in response to the driving voltage has the same angular distance and the voltage through the individual terminals L1, L2, L3, and L4 arranged in four different directions. can be authorized. The individual terminals may be disposed with the same angular distance based on the central axis of the liquid lens, and may include four individual terminals. The four individual terminals may be respectively disposed at the four corners of the liquid lens. When a voltage is applied through the individual terminals L1, L2, L3, and L4, the applied voltage is disposed in the lens region 310 by a driving voltage formed by interaction with a voltage applied to the common terminal C0, which will be described later. The interface between the electrically conductive liquid and the non-conductive liquid may be deformed.

In addition, referring to (b), one side of the lens 28 receives operating voltages from different individual terminals (L1, L2, L3, L4), and the other side of the lens 28 receives a plurality of capacitors connected to the common terminal (C0) ( 30) can be explained. Here, the plurality of capacitors 30 included in the equivalent circuit may have a small capacitance of about several tens to 200 picofarads (pF) or less. The terminal of the liquid lens described above of the liquid lens may be referred to herein as an electrode sector or a sub-electrode.

4 illustrates the structure of a liquid lens.

As shown, the liquid lens 28 may include a liquid, a first plate, and an electrode. The liquids 122 and 124 included in the liquid lens 28 may include a conductive liquid and a non-conductive liquid. The first plate may include a cavity 150 or a hole in which a conductive liquid and a non-conductive liquid are disposed. The cavity 150 may include an inclined surface. The electrodes 132 and 134 may be disposed on the first plate 114 , and may be disposed above the first plate 114 or below the first plate 114 . The liquid lens 28 may further include a second plate 112 that may be disposed above (below) the electrodes 132 and 134 . In addition, the liquid lens 28 may further include a third plate 116 that may be disposed under (upper) the electrodes 132 and 134 . As shown, one embodiment of a liquid lens 28 may include an interface 130 formed by two different liquids 122 , 124 . It may also include at least one substrate 142 , 144 for supplying a voltage to the liquid lens 28 . The edge (corner) of the liquid lens 28 may be thinner than the center of the liquid lens 28 . The second plate may be disposed on the upper surface of the liquid lens and the third plate may be disposed on the lower surface of the liquid lens, but the second plate or third plate is not disposed on a part of the upper surface or lower surface of the liquid lens corner. may be thinner than the central portion. An electrode may be exposed on the upper or lower surface of the corner of the liquid lens.

The liquid lens 28 includes two different liquids, for example, a conductive liquid 122 and a non-conductive liquid 124 , and the curvature and shape of the interface 130 formed by the two liquids are in the liquid lens 28 . It can be adjusted by the supplied driving voltage. The driving voltage supplied to the liquid lens 28 may be transmitted through the connection unit 500 . The connection part may include at least one of the first substrate 142 and the second substrate 144 . When the connecting portion includes the first substrate 142 and the second substrate 144 , the second substrate 144 may transmit a voltage to each of a plurality of individual terminals, and the first substrate 142 may apply a voltage to the common terminal. can transmit The plurality of individual terminals may be four, and the second substrate 144 may transmit a voltage to each of the four individual terminals. The voltage supplied through the second substrate 144 and the first substrate 142 may be applied to the plurality of electrodes 134 and 132 disposed or exposed at each corner of the liquid lens 28 .

In addition, the liquid lens 28 is located between the third plate 116 and the second plate 112, the third plate 116 and the second plate 112 including a transparent material, and has an opening having a preset inclined surface. It may include a first plate 114 including a region.

In addition, the liquid lens 28 may include a cavity 150 determined by the opening areas of the third plate 116 , the second plate 112 , and the first plate 114 . Here, the cavity 150 may be filled with two liquids 122 and 124 of different properties (eg, a conductive liquid and a non-conductive liquid), and an interface 130 between the two liquids 122 and 124 of different properties. ) can be formed.

In addition, at least one of the two liquids 122 and 124 included in the liquid lens 28 has conductivity, and the liquid lens 28 has two electrodes 132 and 134 disposed above and below the first plate 114 . may include. The first plate 114 may include an inclined surface and further include an insulating layer 118 disposed on the inclined surface. The conductive liquid may contact the insulating layer. Here, the insulating layer 118 covers one of the two electrodes 132 and 134 (eg, the second electrode 134 ) and partially covers the other electrode (eg, the first electrode 132 ). or exposed to apply electrical energy to the conductive liquid (eg, 122 ). Here, the first electrode 132 includes at least one electrode sector (eg, C0), and the second electrode 134 includes two or more electrode sectors (eg, L1, L2, L3, L4 in FIG. 4). can do. For example, the second electrode 134 may include a plurality of electrode sectors sequentially arranged in a clockwise direction with respect to the optical axis. The electrode sector may be referred to as a sub-electrode or a terminal of a liquid lens.

One or two or more substrates 142 and 144 for transferring voltage to the two electrodes 132 and 134 included in the liquid lens 28 may be connected. The focal length of the liquid lens 28 may be adjusted while the curvature, curvature, or inclination of the interface 130 formed in the liquid lens 28 is changed in response to the driving voltage.

5A and 5B explain the reason why the diopter (diopter) changes in a liquid lens according to a change in temperature. Specifically, FIG. 5A describes a liquid lens at room temperature, and FIG. 5B shows a liquid lens at a high temperature. Explain.

As described above, the cavity determined by the first layer 12 , the intermediate layer 14 , and the second layer 16 is filled with two liquids having different properties. The intermediate layer 14 may be referred to as a first plate, the first layer 12 may be referred to as a second plate, and the second layer 16 may be referred to as a third plate. The intermediate layer 14 may include a cavity in which a conductive liquid and a non-conductive liquid are disposed. The liquid filled in the liquid lens has a property of expanding when the temperature increases (eg, thermal expansion).

The two liquids filled in the cavity may include an electrolyte (or conductive) liquid and a non-electrolyte (or non-conductive) liquid. The thermal expansion of liquids may be greater than that of solids. When the temperature of a substance increases, the movement of molecules becomes more active, and the distance between the molecules increases, which can increase the volume. In particular, since molecules constituting a liquid can move more freely than molecules constituting a solid, when the degree of temperature change is the same, the degree of thermal expansion of the liquid may be greater than that of the solid. A typical example of an electrolyte (conductive) liquid used in a liquid lens is water (H ₂ O). In the case of water, the volume expands when the temperature rises above 4°C, but decreases in volume when the temperature rises below 4°C. The coefficient of thermal expansion of water is known to be ^{about 1.8 (unit: 10 -5 /℃).}

5A, if there is no change in the volume of the two liquids filled in the cavity at room temperature, the light (light) incident through the first layer 12 is refracted by the interface 30 formed between the two liquids in the cavity. may be affected and pass through the second layer 16 . In this case, the liquid lens can be controlled in a desired direction by applying electric energy to the liquid lens to change the curvature of the interface 30 .

Referring to FIG. 5B , a shape in which the first layer 12 or the second layer 16 swells may occur due to a change in volume of the two liquids filled in the cavity at a high temperature. The central and peripheral regions of the first layer are not adhered to the intermediate layer 14, and since the thickness of the central portion is thin, the first layer 12 may be bent in response to the two liquids increasing in volume according to the temperature change. have. For example, the first layer 12 may swell up to about 20 mm, and in this case, the amount of change in dioptre (diopter) may be about 4.7.

On the other hand, due to the thickness of the first layer 12 and the second layer 16 and the area in contact with the liquid, the second layer 16 swells relatively less than the first layer 12 or does not swell even with a temperature change. can

After the intermediate layer 14 on which the plurality of electrode patterns are disposed is fixed on the second layer 16, an insulating layer (not shown) may be formed to prevent the plurality of electrode patterns from being exposed to the cavity. For example, one of the two electrode patterns is covered with an insulating layer and only the other is exposed to prevent the properties of the two liquids filled in the cavity from changing. Due to the insulating layer formed on the intermediate layer 14 and the second layer 16, even if the two liquids thermally expand in response to a temperature change, the second layer 16 does not swell relatively compared to the first layer 12. , the strength of the weak first layer 12 may be relatively swollen compared to the second layer 16 .

When the first layer 12 swells, the light (light) incident through the first layer 12 has a curvature generated in the first layer 12 separately from the interface 30 whose curvature is controlled through electrical energy. can be refracted by In this case, the curvature occurring in the first layer 12 may not be reflected in the design of the liquid lens, and even if the coefficient of thermal expansion according to the temperature change of the two liquids is accurately known, the curvature of the first layer 12 is uniform. Chances are it won't happen. For example, depending on the adhesive strength of the first layer 12 and the intermediate layer 14 , it may swell from the portion having the lowest strength. As described above, a diopter change of the liquid lens may occur due to a temperature change due to the first layer 12 that is not uniformly maintained, and it may be difficult to accurately predict such a diopter change.

6A and 6B illustrate a diopter (diopter) change amount of a liquid lens according to a change in temperature. Specifically, FIGS. 6A and 6B are results of tracking a change in diopter according to a temperature change in a liquid lens having a preset focal length according to different operating environments or operating purposes.

6A and 6B , the liquid lens may have different diopter values according to the level of the applied driving voltage. However, it can be seen that the amount of diopter change occurs according to the temperature change (rising in the range of about 25 degrees Celsius to 40 degrees Celsius) even when the same driving voltage is applied. As can be seen in the case of the two liquid lenses, it can be seen that the amount of diopter change is proportional to the temperature rise in the normal temperature range.

However, the diopter change amount may not be proportional to the temperature change in the operating environment of the liquid lens at extremely low temperature or extremely high temperature. As described with reference to FIGS. 5A and 5B , it can be related to the coefficient of thermal expansion of the two liquids contained in the liquid lens. In addition, complex factors such as elasticity and bonding degree of the transparent layer constituting the liquid lens may also affect the amount of diopter change according to temperature change. Accordingly, the amount of diopter change according to the temperature change can be measured through a lens calibration process, and this data can be stored in the control circuit.

7A and 7B illustrate a method of measuring a spatial resolution change of a liquid lens according to a change in temperature. Specifically, FIG. 7A describes a chart for measuring spatial resolution (SFR) at a far focus, and FIG. 7B describes a chart for measuring spatial resolution (SRF) at a near focus.

The camera module receives light through an external filter and acquires an image in RGB format through an image sensor. Looking at the image acquisition using the sensor of the camera module in terms of frequency, the spatial frequency spectrum of the image to be acquired may have a spatial frequency spectrum in the form of repeating on the x-axis and y-axis of a two-dimensional plane. In order to measure the optical characteristics of the liquid lens, the distance between the liquid lens and the chart described in FIG. 7A or 7B is adjusted to a preset value, and an image for the chart may be obtained using the liquid lens.

In order to analyze the resolution of the camera module or the liquid lens, spatial frequency response (SFR) of the camera module or the liquid lens may be measured. Here, the spatial resolution is an index indicating the relationship between the input spatial frequency and the responsiveness of the digital camera, and is expressed as a change in the modulation transfer function (MTF) according to the increase of the spatial frequency. Here, the modulation transfer function (MTF) represents a reproduction ratio of the contrast, and may be expressed as a ratio of the output contrast (Ro) to the input contrast (Ri) (MTF=Ro/Ri).

The spatial frequency of each pattern of the resolution chart described in FIGS. 7A and 7B may indicate how many patterns are repeated per preset interval (eg, 1 mm) (eg, the unit is cycles/mm) . Through the modulation transfer function (MTF), it is possible to numerically display how much the resolution chart projected through the lens reproduces the original image compared to the original resolution chart. Assuming that the spatial resolution (SFR) obtainable in this way has a numerical range of 0 to 100, the spatial resolution (SFR) of the liquid lens must be greater than or equal to a preset value in accordance with the performance of the lens required by the camera module. may be applied to the camera module.

However, as described in FIGS. 5A, 5B, 6A, and 6B, since the spatial resolution (SFR) of the liquid lens changes according to the temperature change, in order to apply the liquid lens to the camera module, correction according to the temperature change is required. .

8A and 8B illustrate a change in spatial resolution (SFR) of a liquid lens according to a change in temperature. When power is supplied to the camera module, the temperature of the camera module may increase due to various factors that generate heat in the camera module. Here, the spatial resolution (SFR) change was measured assuming that the temperature change of the liquid lens rises from room temperature (about 23 degrees) to high temperature (about 50 degrees) over time.

Fig. 8A illustrates that the spatial resolution 74a of the liquid lens changes when the temperature 72 of the liquid lens changes, without correcting the driving voltage supplied to the liquid lens. Over time, the temperature in the camera module may increase, and the temperature increase in the camera module may increase the temperature of the liquid lens. As shown, as the temperature 72 rises, the spatial resolution 74a of the liquid lens can be lowered. Before the temperature 72 rises (time 0 seconds), the spatial resolution 74a is about 60, but after about 30 minutes (when the temperature rises), the spatial resolution 74a can be lowered to about 45.

8B shows the change in spatial resolution (SFR) of the liquid lens according to the temperature change when the driving voltage supplied to the liquid lens is lowered by about 1.44 V and supplied. For example, the driving voltage can be lowered by about 1.44V by reducing and inputting 32 codes of 12-bit data in a control circuit capable of controlling the driving voltage in response to 12-bit data corresponding to the temperature. As shown, when the temperature 72 of the liquid lens is room temperature, the spatial resolution 72b was low, but it shows that the spatial resolution SFR is improved as the temperature rises. Before the temperature 72 rises (time 0 sec), the spatial resolution 74a is about 55, but after about 30 minutes (when the temperature rises), the spatial resolution 74a can be increased to about 63.

Fig. 9 explains the determination of the compensation value of the liquid lens according to the temperature change.

As shown, the two cases described in FIGS. 8A and 8B may be combined to compensate for the lowering of the spatial resolution (SFR) according to the temperature change of the liquid lens. That is, when the driving voltage is not corrected (74a) and when the driving voltage is adjusted by a preset amount (about 1.44V) to provide better spatial resolution (SFR) based on the specific time point (A) (74b) ) to control the liquid lens.

Here, the specific time point A may be a time point when a preset time elapses from the start of a preset operation. For example, the preset time may be about 520 seconds. That is, the specific time point A at which the spatial resolution SFR becomes substantially the same in the case where the driving voltage is not corrected (74a) and when the driving voltage is adjusted by a preset amount (about 1.44V) (74b) is the initial state. 520 seconds have elapsed. Meanwhile, the specific time point A may be a time point when the temperature of the image sensor is about 40 to 45 degrees and the temperature of the liquid lens rises correspondingly. Even when the driving voltage supplied to the liquid lens for autofocusing (AF) increases from 30V to 40V, the driving voltage may be reduced by 1.44V after a preset time elapses. This can also be implemented by shifting the entire voltage-related code after a certain period of time has passed.

According to an embodiment, the start of the preset operation may be a time when power is applied to the image sensor or the controller. Also, in another embodiment, the start of the preset operation may be a point in time when the control circuit automatically focuses on a specific object in an image acquired through the image sensor.

Meanwhile, determining the start time of the preset operation may mean a time at which the temperature of the liquid lens starts to rise. This may vary depending on the structure and shape of the camera module including the liquid lens.

Based on a specific time point (A), the spatial resolution (SFR) of the liquid lens may have a preset range (B) according to a change in temperature through a method of correcting the driving voltage supplied to the liquid lens. For example, the spatial resolution (SFR) may range from about 57 to 64. Since the spatial resolution (SFR) of the liquid lens may have a preset range (B), that is, a small change according to the temperature change, the camera module including the liquid lens may implement substantially uniform resolution even with the temperature change. have.

10 illustrates a camera module.

As shown, the camera module includes a liquid lens 28 in which an interface 30 formed by two different liquids is adjusted in response to a driving voltage applied to a plurality of individual electrodes, and a driving voltage to compensate for temperature change. It may include a control circuit 24 for adjusting the level. Here, the camera module may perform a correction function corresponding to the temperature change, but a temperature sensor for detecting the temperature change may not be required.

The liquid lens 28 may include a lens region where the interface 30 is located and a rib region for protecting the lens region.

The control circuit 24 may determine a driving voltage differently for each of the plurality of individual electrodes in order to compensate for optical image stabilization (OIS). At this time, the control circuit 24 controls the driving voltage compensation value (eg, 1.44V) at the specific time point A and the specific time point A described with reference to FIG. 9 to compensate for the temperature change of the camera module or the liquid lens. can be saved. It is also possible to store code compensation values. In the case of a code compensation value, it may be a code value that needs to be compensated after a certain time elapses from the code value at the time of focusing. According to an embodiment, the control circuit 24 may control the driving voltage in response to 12-bit data corresponding to the temperature, and when a preset time elapses (that is, at a specific time point A), the 12-bit data is output. 32 codes can be reduced.

In addition, the control circuit 24 may further include a gyro sensor (not shown) that detects the movement of the camera module and outputs a detection signal corresponding to the movement. For compensation for optical image stabilization (OIS), the control circuit 24 may determine the level of the driving voltage in response to both the sensing signal and the temperature change.

Although not shown, the camera module may further include a connector (not shown) that connects the liquid lens 28 and the control circuit 24 and transmits a driving voltage. The connection part may use a flexible printed circuit board (FPCB). The flexible printed circuit board (FPCB) may include a simple circuit as well as at least one wire that transmits a driving voltage.

On the other hand, the control circuit 24 may further include a storage unit (not shown) for storing the amount of change in diopters (dioptre, diopter) according to the temperature change. The control circuit 24 may recognize the amount of diopter change corresponding to the temperature change from the storage unit. In this case, the storage unit may be included in the control circuit 24 as a non-volatile memory device, or may be implemented as an independent device interworking with the control circuit 24 . The amount of change in the diopter according to the temperature change stored in the storage unit may be determined by lens calibration.

The camera module converts the optical signal transmitted through the liquid lens 28 and the liquid lens 28 and the lens assembly 22 including at least one solid lens aligned with the center, and the lens assembly 22 into an electrical signal. It may further include an image sensor 26 that does.

The image sensor 26 may output image data, and the processing system or computing device 40 may perform image processing, correction, brightness adjustment, etc. based on the image data from the image sensor 26 . Here, the processing system or computing device 40 may transmit a control signal or a correction value for correction control to the control circuit 24 . Here, the processing system or computing device 40 may include a camera module or may be included in a portable device, a computer, a vehicle, a server, etc. that interwork with the camera module. The control circuit 24 may generate a driving voltage corresponding to the correction control, and may receive clock information from the processing system 40 to count a time from a preset time point. The control circuit 24 may count the time based on the clock information and correct the driving voltage by a preset level at a specific time point (A, see FIG. 9 ).

11 illustrates a control circuit in the camera module.

As shown, the camera module includes a liquid lens 28, an image sensor 26 for converting an optical signal transmitted through the liquid lens 28 into image data, and processing the data transmitted from the image sensor 26. A processing system 40 for controlling the liquid lens 28 and a control circuit 24 for controlling the liquid lens 28 may be included. Here, the image sensor 26 and the processing system 40 , the processing system 40 and the control circuit 24 may transmit and receive data and control signals through serial communication. For example, for serial communication, a clock line (Serial Clock, SCL) and a data line (Serial Data, SDA) for synchronization may be connected to each other.

The control circuit 24 includes a gyro sensor 52 for detecting the movement of the camera module, a driving circuit 54 for generating a driving voltage transmitted to the liquid lens 28, and compensation for optical image stabilization (OIS). It may include an optical image stabilization unit 56 that determines the value and transmits it to the driving circuit 54 .

The gyro sensor 52 and the optical image stabilization unit 56 may be connected through a serial peripheral interface bus (SPI bus). Here, the SPI bus is a synchronous serial data connection standard named after the Motorola architecture that operates in an architectural full duplex communication mode, in which devices communicate in a master-slave mode, where the master device initiates data frames, multiple slave devices They can operate with individual Slave Select (Chip Select) lines. The SPI bus may include a clock signal pin (SCLK, SCK/CLK), a chip select signal pin (CS, FSS/SS), a data input pin (MOSI), a data output pin (MISO), and the like.

The optical image shake prevention unit 56 recognizes a preset level at which the driving voltage needs to be corrected from the storage device 58 that stores the compensation code for compensating for the temperature change and the compensation time based on the 12-bit temperature data. Thereafter, the driving voltage may be transmitted to the driving circuit 54 to adjust the corrected level. Here, the storage device 58 may be included in the optical image stabilization unit 56 , or may be configured independently and interlock with the optical image stabilization unit 56 .

For example, a compensation code of -32 Code (1.44 V) and a compensation time of about 520 seconds, which is a preset time point, may be recorded in the storage device 58 based on 12-bit temperature data. The optical image shake prevention unit 56 can recognize the compensation time based on the transmitted clock information, and at that time, the driving voltage transmitted to the liquid lens 28 is as low as (about 1.44 V) corresponding to the compensation code. can make you lose

Fig. 12 explains the control method of the liquid lens.

As shown, the liquid lens control method includes the steps of detecting the start of a preset operation of the camera module (62), supplying a driving voltage corresponding to the preset operation (64), and after the driving voltage is supplied, After the set time has elapsed, the step of adjusting the driving voltage by a preset level (66) may be included.

In step 62 of detecting the start of the preset operation of the camera module, the start of the preset operation may be a time when power is applied to an image sensor or a control circuit in the camera module. Meanwhile, according to an embodiment, the preset operation start of the camera module may be a point in time when the control circuit automatically focuses on a specific object in an image acquired through the image sensor.

The control circuit included in the camera module may not only detect the start of a preset operation of the camera module, but may supply a driving voltage corresponding to the preset operation to the liquid lens (64). The driving voltage supplied to the liquid lens may include a voltage (LL1 to LL4, see FIG. 11) supplied to the individual electrodes and a voltage (COM, see FIG. 11) supplied to the common electrode. For example, when power is applied to the camera module, the control circuit may supply a driving voltage that allows the liquid lens to have optimal spatial resolution (SRF).

When power is applied to the camera module for a preset time, heat may be generated in components such as an image sensor in the camera module, and the temperature of the liquid lens in the camera module may rise.

When a preset time elapses after the driving voltage is supplied, the driving voltage may be adjusted by a preset level (66). For example, when it is about 520 seconds after the temperature inside the camera module starts to rise, the driving voltage can be lowered by about 1.44 V. At this time, the size of the adjusted driving voltage (about 1.44 V) is determined regardless of the auto-focusing (AF) function, hand-shake correction or optical image stabilization (OIS) function of the liquid lens.

If the driving voltage supplied to the liquid lens is changed for the image stabilization (OIS) function for a preset period of time, temperature compensation for the change in the driving voltage controlled through the autofocusing (AF) or image stabilization (OIS) function Compensation for For example, even when the driving voltage supplied to the liquid lens for autofocusing (AF) increases from 30V to 40V, the driving voltage may be reduced by 1.44V after a preset time elapses.

The camera module may include a plate including a cavity in which a conductive liquid and a non-conductive liquid are disposed, a common electrode disposed on the plate, and a liquid lens including a plurality of individual electrodes disposed below the plate. . In addition, it may further include a lens holder including a solid lens disposed above or below the liquid lens, and may further include a sensor substrate disposed under the lens holder and on which an image sensor is disposed. In addition, it is disposed on the sensor substrate and includes a control unit for controlling a driving voltage supplied between the common electrode and the plurality of individual electrodes, and a connection unit for electrically connecting the plurality of individual electrodes or the common electrode and the sensor substrate, , when the camera module is driven for a predetermined time, the resolution of the camera module may have a period of decreasing and increasing by adjusting the driving voltage applied to the liquid lens.

In the camera module described above, when a preset time comes from the time of the preset operation by the controller, the level of the driving voltage may be adjusted by the preset level. In this case, the controller may reduce the driving voltage by a preset level, and the preset operation time is when power is applied to the image sensor or the controller, or when the controller focuses on a specific object in the image acquired through the image sensor. could be a point in time. The preset period may be within 520 seconds. In addition, the controller may control the driving voltage in response to n-bit (n is a natural number) data corresponding to the temperature, and may decrease the driving voltage by an n-bit specific code when a preset time elapses. The controller may differently supply a driving voltage to each of the plurality of individual electrodes for shake compensation.

The method for controlling a liquid lens includes the steps of detecting a preset operation time of the camera module, supplying a driving voltage corresponding to the preset operation, and driving by a preset level when a preset time elapses after the driving voltage is supplied It may include adjusting the voltage.

A compensation code and a compensation time may be stored in a storage unit in a control circuit that may be implemented as a nonvolatile memory device. In addition, a driving voltage corresponding to the optimal spatial resolution measured and recognized through lens calibration may also be recorded in the storage unit.

Meanwhile, according to an embodiment, at least a part of the process of determining the amount of change in the storage unit and the diopter may be implemented in the form of a program executed in a computer device or in the form of a batch file, and the change amount of the diopter is a code in the form of a table or a list Alternatively, it may be implemented with data.

The liquid lens described above may be included in the camera module. The camera module includes a lens assembly including a liquid lens mounted on a housing and at least one solid lens that can be disposed on the front or rear side of the liquid lens, an image sensor that converts an optical signal transmitted through the lens assembly into an electrical signal, and A control circuit for supplying a driving voltage to the liquid lens may be included.

On the other hand, the operation and operating method of the control circuit having the structure of the above-described embodiment may be produced as a program to be executed by a computer and stored in a computer-readable recording medium, and the computer-readable recording medium is a ROM. , RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices.

The computer-readable recording medium is distributed in a network-connected computer system, so that the computer-readable code can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the above-described method can be easily inferred by programmers in the technical field to which the embodiment belongs.

Although only a few have been described as described above in relation to the embodiments, various other forms of implementation are possible. The technical contents of the above-described embodiments may be combined in various forms unless they are incompatible with each other, and may be implemented in a new embodiment through this.

An optical device including the above-described camera module may be implemented. Here, the optical device may include a device capable of processing or analyzing an optical signal. Examples of optical devices include camera/video devices, telescope devices, microscope devices, interferometer devices, photometric devices, polarimeter devices, spectrometer devices, reflectometer devices, autocollimator devices, lensmeter devices, etc., and may include liquid lenses. The embodiment of the present invention can be applied to an optical device capable of In addition, the optical device may be implemented as a portable device such as a smart phone, a notebook computer, or a tablet computer. Such an optical device may include a camera module, a display unit for outputting an image, and a body housing on which the camera module and the display unit are mounted. The optical device may have a communication module capable of communicating with other devices mounted on the main housing and may further include a memory unit capable of storing data.

It is apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit and essential characteristics of the present invention. Accordingly, the above detailed description should not be construed as restrictive in all respects but as exemplary. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are included in the scope of the present invention.

Claims (9)

In the camera module, the camera module
a liquid lens including a plate including a cavity in which a conductive liquid and a non-conductive liquid are disposed, a common electrode disposed on the plate, and a plurality of individual electrodes disposed below the plate;
a lens holder including a solid lens disposed above or below the liquid lens;
a sensor substrate disposed under the lens holder and on which an image sensor is disposed;
a control unit disposed on the sensor substrate and controlling a driving voltage supplied between the common electrode and a plurality of individual electrodes; and
a connection part electrically connecting the plurality of individual electrodes or common electrodes and the sensor substrate;
When the camera module is driven for a certain time,
The resolution of the camera module decreases and then increases by adjusting the driving voltage applied to the liquid lens,
the control unit
Includes a storage unit for storing a preset level for each preset time,
The control unit to adjust the section,
When the preset time comes from the time of the preset operation, the preset level corresponding to the preset time is read from the storage unit and the level of the driving voltage is adjusted by the preset level. delete According to claim 1,
The preset operation point is a point in time when power is applied to the image sensor or the controller, or a point in time when the controller focuses on a specific object in an image acquired through the image sensor. According to claim 1,
The preset time is within 520 seconds, the camera module. According to claim 1,
The control unit decreases the level of the driving voltage by the preset level, the camera module. According to claim 1,
The controller controls the driving voltage in response to n-bit data corresponding to a temperature, and decreases the driving voltage by the n-bit specific code when the preset time elapses. According to claim 1,
The controller differently supplies the driving voltage to each of the plurality of individual electrodes to compensate for shake. According to claim 1,
Further comprising a gyro sensor for detecting the movement of the camera module and outputting a detection signal corresponding to the movement,
The control unit determines the level of the driving voltage in response to the detection signal and the temperature change of the camera module or the liquid lens, the camera module. A camera module comprising a liquid lens including one common electrode and four individual electrodes to adjust the interface formed by two liquids,
detecting a preset operation time of the camera module;
supplying a driving voltage corresponding to the preset operation; and
adjusting the driving voltage by a preset level when a preset time elapses after the driving voltage is supplied
including,
The preset level for each preset time is stored in advance,
When the driving voltage is adjusted, the preset level stored corresponding to the preset time is read out, a control method of a liquid lens.

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