WO2012057435A1

WO2012057435A1 - Camera module and estimation method of auto focus search range thereof

Info

Publication number: WO2012057435A1
Application number: PCT/KR2011/005399
Authority: WO
Inventors: Junghyun Lee
Original assignee: LG Innotek Co Ltd
Current assignee: LG Innotek Co Ltd
Priority date: 2010-10-26
Filing date: 2011-07-21
Publication date: 2012-05-03
Anticipated expiration: 2013-04-26
Also published as: KR101126295B1

Abstract

A camera module according to the present invention includes: an actuator increasing an electrostatic capacity in response to intensity of applied voltage or current; and an actuator driving unit applying a voltage or a current to the actuator, wherein the actuator driving unit includes a cap sensing unit sensing electrostatic capacity of the actuator, and an auto focusing range setting unit setting up an auto focusing search range of the actuator by using change of electrostatic capacity sensed by the cap sensing unit under an auto focusing search range set-up mode.

Description

CAMERA MODULE AND ESTIMATION METHOD OF AUTO FOCUS SEARCH RANGE THEREOF

The teachings in accordance with the exemplary embodiments of this invention relate generally to a camera module and an estimation method of auto focus search range thereof.

Generally, a small compact camera module is applied to mobile communication devices and various IT (Information Technology) devices including a camera phone, a PDA and a smart phone. The camera module is manufactured using an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) as an essential element, and is also focus-adjustably manufactured to adjust the size of an image.

At this time, the camera module includes a plurality of lenses where a driving source is mounted to adjust an optical focal length by moving each lens to change its relative distance.

To be more specific, the camera module includes an image sensor for changing an optical signal to an electrical signal, lenses and IR (Infrared) filter for condensing light to the image sensor, a housing for housing the image sensor, the lenses and IR filter, and a PCB (Printed Circuit Board) processing the signal of the image sensor.

The lenses are attached to a lens barrel coupled to a bobbin to be positioned on the image sensor, and a VCM (Voice Coil Motor) is mounted as a driving source to adjust a gap between the lens barrel and the image sensor.

Recently, researches are actively waged on a camera module capable of performing an auto focus function by using a MEMS (Micro-Electromechanical) actuator utilizing MEMS system instead of a conventional VCM. The MEMS actuator adjusts a focus by vertically moving only one or two moving lenses among the plurality of lenses in response to difference of electrostatic capacity by way of electrostatic force method.

At this time, the MEMS actuator moves the lenses based on intensity of voltage (or current) inputted from a driver IC (Integrated Circuit) as electrostatic capacity changes, where the driving distance varies based on the voltage applied to the actuator in every camera module.

AF (Auto Focus) calibration is a method in which an actual driving section that is focused among a total driving distance of a lens for auto focusing is searched and stored in a memory, and an auto focusing drive is controlled at the actual auto focusing section only. In a camera module using the conventional VCM actuator is not available with a feedback signal relative to lens driving, such that a focusing value change is pursued through image test for AF calculation, or an actual lens driving scope can be estimated through a displacement measurer using laser displacement.

However, the displacement measurer using laser displacement has a disadvantage because of restrictions caused by difficulty in accurate adjustment and cost of equipment. The other disadvantage is that tack time increase and deviation of image sensor must be covered in case of image test.

The present invention is directed to solve at least one or more of the aforementioned problems in whole or in part and to provide a method for estimating an auto focus search range of a camera module capable of setting up an effective auto focusing search range for each camera module.

Technical problems to be solved by the present invention are not restricted to the above-mentioned, and any other technical problems not mentioned so far will be clearly appreciated from the following description by skilled in the art.

An object of the invention is to overcome at least one or more of the above problems and/or disadvantages in whole or in part, and/or provide at least the advantages described hereinafter, and/or make improvements in the prior art. In order to achieve at least the above objects, in whole or in part, and in accordance with the purposes of the invention, as embodied and broadly described, and in one general aspect of the present invention, there is provided a camera module, comprising: an actuator increasing an electrostatic capacity in response to intensity of applied voltage or current; and an actuator driving unit applying a voltage or a current to the actuator, wherein the actuator driving unit includes a cap sensing unit sensing electrostatic capacity of the actuator, and an auto focusing range setting unit setting up an auto focusing search range of the actuator by using change of electrostatic capacity sensed by the cap sensing unit under an auto focusing search range set-up mode.

Preferably, the actuator driving unit further includes a memory storing the auto focusing search range set up by the auto focusing range setting unit, and the actuator driving unit applies a current or a voltage corresponding to the auto focusing search range stored in the memory under a photographing (shooting mode).

Preferably, the auto focusing range setting unit gradually increases a digital code at a set first code interval, and sets up a first prior electrostatic capacity at a minimum electrostatic capacity of the auto focusing search range in case that a difference between the first prior electrostatic capacity of the actuator corresponding to the increase of the digital code and a first current electrostatic capacity is more than a set minimum change.

Preferably, the auto focusing range setting unit gradually decreases a digital code at a set second code interval, and sets up a second prior electrostatic capacity at a maximum electrostatic capacity of the auto focusing search range in case that a difference between the second prior electrostatic capacity of the actuator corresponding to the decrease of the digital code and a second current electrostatic capacity is more than a set maximum change.

Preferably, the first code interval is greater than the second code interval.

Preferably, the actuator is an actuator connected to a moving lens to vertically move the moving lens along an optical axis in response to the electrostatic capacity formed by the current or voltage applied from the actuator driving unit.

In another general aspect of the present invention, there is provided a method for setting up an auto focusing search range of an actuator in which electrostatic capacity changes in response to intensity of applied current or voltage, the method comprising: applying to the actuator a current or a voltage corresponding to a digital code changing by increasing a digital code at a set first code interval under an auto focusing search range setting mode (a); sensing the electrostatic capacity change of the actuator (b); comparing a prior electrostatic capacity and a current electrostatic capacity of the actuator (c); and setting the prior electrostatic capacity as a minimum electrostatic capacity in case that a difference between the prior electrostatic capacity and the current electrostatic capacity is more than a set minimum change (d).

Preferably, the (a) step and the (c) step are repeatedly performed in case that the difference between the prior electrostatic capacity and the current electrostatic capacity is less than the set minimum change.

Preferably, the method further includes storing a minimum digital code corresponding to the minimum electrostatic capacity of the auto focusing search range (e).

Preferably, the method further includes applying to the actuator only a current or a voltage higher than a current or voltage corresponding to the minimum digital code stored under a photographing mode (f).

Preferably, the actuator is an actuator connected to a moving lens to vertically move the moving lens along an optical axis in response to the electrostatic capacity formed by the current or voltage applied from the actuator driving unit, and the digital code is a code corresponding to a distance moved by a moving lens.

In still another general aspect of the present invention, there is provided a method for setting up an auto focusing search range of an actuator in which electrostatic capacity changes in response to intensity of applied current or voltage, the method comprising: applying to the actuator a current or a voltage corresponding to a digital code changing by decreasing a digital code at a set second code interval under an auto focusing search range setting mode (a); sensing the electrostatic capacity change of the actuator (b); comparing a prior electrostatic capacity and a current electrostatic capacity of the actuator (c); and setting the prior electrostatic capacity as a maximum electrostatic capacity in case that a difference between the prior electrostatic capacity and the current electrostatic capacity is more than a set maximum change (d).

Preferably, the (a) step and the (c) step are repeatedly performed in case that the difference between the prior electrostatic capacity and the current electrostatic capacity is less than the set maximum change.

Preferably, the method further includes storing a maximum digital code corresponding to the maximum electrostatic capacity of the auto focusing search range (e).

Preferably, the method further includes applying to the actuator only a current or a voltage less than a current or voltage corresponding to the maximum digital code stored under a photographing mode (f).

In still further general aspect of the present invention, there is provided a method for setting up an auto focusing search range of an actuator in which electrostatic capacity changes in response to intensity of applied current or voltage, the method comprising: applying to the actuator a current or a voltage corresponding to a digital code changing by increasing a minimum digital code at a set first code interval under an auto focusing search range setting mode (a); sensing the electrostatic capacity change of the actuator (b); comparing a first prior electrostatic capacity and a first current electrostatic capacity of the actuator (c); setting the first prior electrostatic capacity as a minimum electrostatic capacity of the auto focusing search range in case that a difference between the first prior electrostatic capacity and the first current electrostatic capacity is more than a set minimum change (d); applying to the actuator a current or a voltage corresponding to a digital code changing by decreasing a maximum digital code at a set second code interval (e); sensing the electrostatic capacity change of the actuator (f); comparing a second prior electrostatic capacity and a second current electrostatic capacity of the actuator (g); and setting the second prior electrostatic capacity as a maximum electrostatic capacity of the auto focusing search range in case that a difference between the second prior electrostatic capacity and the second current electrostatic capacity is more than a set maximum change (h).

The exemplary embodiments of the present invention have advantageous effect in that electrostatic capacity change of an actuator in response to digital code change can be detected and analyzed to set up an auto focusing search range of the actuator free from the conventional separate devices as employed in laser displacement or image test.

The exemplary embodiments of the present invention have another advantageous effect in that a time for searching for an unnecessary dead zone for auto focusing can be reduced and the auto focusing speed can be enhanced by driving the actuator within an auto focusing search range stored in the memory unit (84) under a shooting (photographing) mode.

The exemplary embodiments of the present invention have still another advantageous effect in that a numerical value necessary for setting an auto focusing search range is set up in consideration of the fact that the electrostatic capacity change of an actuator becomes smaller as a digital code is smaller, and the electrostatic capacity change of an actuator becomes larger as the digital code is larger, to thereby increase a search accuracy of minimum value and maximum value of the auto focusing search range.

The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:

FIG.1 is a cross-sectional view illustrating a camera module according to an exemplary embodiment of the present invention;

FIG.2 is a schematic constitutional diagram illustrating a camera module according to an exemplary embodiment of the present invention;

FIG.3 is a schematic constitutional diagram illustrating a camera module according to another exemplary embodiment of the present invention;

FIG.4 is a schematic flowchart illustrating a method setting a minimum value of auto focusing search range according to an exemplary embodiment of the present invention;

FIG.5 is a graph illustrating an electrostatic capacity change of an actuator (30) in response to digital code change of FIG.4;

FIG.6 is a schematic flowchart illustrating a method setting a maximum value of auto focusing search range according to an exemplary embodiment of the present invention; and

FIG.7 is a graph illustrating an electrostatic capacity change of an actuator (30) in response to digital code change of FIG.6.

The following description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the following teachings, and skill and knowledge of the relevant art are within the scope of the present invention. The embodiments described herein are further intended to explain modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the present invention.

The disclosed embodiments and advantages thereof are best understood by referring to FIGS. 1-7 of the drawings. Other features and advantages of the disclosed embodiments will be or will become apparent to one of ordinary skill in the art upon examination of the following figures and detailed description.

It is intended that all such additional features and advantages be included within the scope of the disclosed embodiments, and protected by the accompanying drawings. Further, the illustrated figures are only exemplary and not intended to assert or imply any limitation with regard to the environment, architecture, or process in which different embodiments may be implemented. Accordingly, the described aspect is intended to embrace all such alterations, modifications, and variations that fall within the scope and novel idea of the present invention.

It will be understood that the terms "includes" and/or "including" when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. That is, the terms "including", "includes", "having", "has", "with", or variants thereof may be used in the detailed description and/or the claims to denote non-exhaustive inclusion in a manner similar to the term "comprising".

Furthermore, "exemplary" is merely meant to mean an example, rather than the best. It is also to be appreciated that features, layers and/or elements depicted herein are illustrated with particular dimensions and/or orientation relative to one another for purposes of simplicity and ease of understanding, and that the actual dimensions and/or orientations may differ substantially from that illustrated. That is, in the drawings, the size and relative sizes of layers, regions and/or other elements may be exaggerated or reduced for clarity. Like numbers refer to like elements throughout and explanations that duplicate one another will be omitted.

It will be understood that when an element or layer is referred to as being "on", "connected to" or "coupled to" another element or layer, the element or layer can be directly on, connected or coupled to another element or layer or intervening elements or layers. In contrast, when an element is referred to as being "directly on," "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It is to be understood that, as used in the specification and in the claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

Now, the present invention will be described in detail with reference to the accompanying drawings.

FIG.1 is a cross-sectional view illustrating a camera module according to an exemplary embodiment of the present invention, FIG.2 is a schematic constitutional diagram illustrating a camera module according to an exemplary embodiment of the present invention, and FIG.3 is a schematic constitutional diagram illustrating a camera module according to another exemplary embodiment of the present invention.

Referring to FIG.1, a camera module according to the present invention includes a moving lens (10), a plurality of stationary lenses (20, 21, 22, 23), an actuator (30), a lens barrel (40), a holder (50), an image sensor (60), a PCB (Printed Circuit Board) (70) and an actuator moving unit (80).

The moving lens (10) is positioned on an upper side of a plurality of stationary lenses (20) to vertically move along an optical axis direction (0) by way of the actuator (30). The actuator (30) is connected to the moving lens (10) to vertically move the moving lens (10) along the optical axis direction (0) according to the electrostatic capacity formed by a current (or voltage) applied to the actuator moving unit (80).

The actuator is such that the electrostatic capacity is increased as the intensity of the current (or voltage) applied from the actuator moving unit (80) is increased to increase a distance that moves the moving lens (10).

In the present invention, the actuator (30) and the actuator moving unit (80) are electrically connected. The way of electrically connecting the actuator (30) and the actuator moving unit (80) may be variably realized, and the way is not limited thereto in the present invention.

The lens barrel (40) secures the actuator (30) to accommodate therein a plurality of stationary lens (20, 21, 22, 23), where a periphery of the lens barrel (40) is tangent to an inner surface of the holder (50), and an upper surface of the lens barrel (40) straddles an upper surface of the holder (50).

The holder (50) is positioned on a periphery of the lens barrel (40) to secure the lens barrel (40), and is supported at a bottom surface thereof by the PCB (Printed Circuit Board) (70). The image sensor (60) is attached to a bottom surface of the lens barrel (40) and an upper surface of the PCB (70) to convert an optical energy incident from the lenses (10, 20) to an electrical energy.

Referring to FIG.2, the actuator moving unit (80) includes a moving unit (81) taking the shape of a driver IC (Integrated Circuit) and applying a current (or voltage) corresponding to a digital code inputted from a memory unit (84) to the actuator (30), a cap sensor (82) capable of sensing an electrostatic capacity of the actuator (30), an auto focusing range setting unit (83) using electrostatic capacity change sensed by the cap sensor (82) under an auto focusing search range setting mode of the camera module to set up an auto focusing search range of the actuator (30), and the memory unit (84) storing the auto focusing search range set up by the auto focusing range setting unit (83).

The actuator (30) is driven within the auto focusing search range stored in the memory unit (84) under the shooting mode after the auto focusing search range setting mode is completed. Thus, in the present invention, the actuator (30) is driven only within the auto focusing search range stored in the memory unit (84) under the shooting mode, whereby a time to search for a dead zone unnecessary for auto focusing can be reduced to enhance an auto focusing speed.

The digital code is a code corresponding to a distance moving the moving lens (10) to a position where a focus of an image outputted from the image sensor is matched. The memory unit (84) applies a digital code corresponding to the auto focusing search range to the moving unit (81).

In case of a 10-bit resolution, the digital code is 0~1023, such that as the digital code is increased, intensity of current (or voltage) applied to the actuator (30) is increased to increase the moving distance of the moving lens (10).

Although the present invention has described that the auto focusing range setting unit (83) and the memory unit (84) are included in the actuator moving unit (80), the auto focusing range setting unit (83) and the memory unit (84) may be positioned outside of the camera module through a I2C bus, as illustrated in FIG.3.

The auto focusing search range is determined by the electrostatic capacity change of the actuator (30). Now, a method for setting an auto focusing search range in the actuator moving unit (80) will be described in more detail with reference to FIGS. 4 through 7.

FIG.4 is a schematic flowchart illustrating a method setting a minimum value of auto focusing search range according to an exemplary embodiment of the present invention, and FIG.5 is a graph illustrating an electrostatic capacity change of an actuator (30) in response to digital code change of FIG.4.

Referring to FIG.4, the auto focusing range setting unit (83) inputs a prior digital code to the moving unit (81) (S401), where 'n' may be zero. The moving unit (83) then applies a prior current corresponding to the prior digital code to the actuator (30) (S402). Then, a prior electrostatic capacity corresponding to the prior current is formed at the actuator (30), and the cap sensor (82) senses the prior electrostatic capacity of the actuator (30) and outputs the prior electrostatic capacity to the auto focusing range setting unit (83) (S403).

The auto focusing range setting unit (83) outputs to the moving unit (81) a current digital code increased as much as a first code interval (20 codes in FIG.8) set up by the prior digital code (S404). Then, the moving unit (81) applies to the actuator (30) a current (present) current corresponding to the inputted current digital code (S405). The actuator (30) forms a current electrostatic capacity corresponding to the applied current (present) current and the cap sensor (82) senses the current electrostatic capacity of the actuator (30) and outputs the current electrostatic capacity of the actuator (30) to the auto focusing range setting unit (83) (S406).

Referring to FIG.5, the prior electrostatic capacity and the current electrostatic capacity may be equal or may be unequal. The present invention seeks for a prior electrostatic capacity where a difference between the prior electrostatic capacity and the current electrostatic capacity is greater than a set "minimum change". Therefore, the auto focusing range setting unit (83) compares in case that the difference between the prior electrostatic capacity and the current electrostatic capacity is less than or greater than the set minimum change (S407). At this time, the minimum change is a predetermined value and may be variably set up depending on type of actuator (30) and the manufacturer.

In case that the difference between the prior electrostatic capacity and the current electrostatic capacity is greater than the set minimum change (S407), the auto focusing range setting unit (83) sets the prior electrostatic capacity of this condition as "minimum electrostatic capacity of auto focusing search range" (S408). Then, the auto focusing range setting unit (83) outputs to the memory unit (84) a minimum digital code corresponding to the minimum electrostatic capacity of auto focusing search range, where the memory unit (84) is stored with the minimum digital code of the auto focusing search range (S409).

However, in case that the difference between the prior electrostatic capacity and the current electrostatic capacity is less than the minimum electrostatic capacity (S407), the auto focusing range setting unit (83) repeats the steps from S404 to S407 to seek for a prior electrostatic capacity where the difference between the prior electrostatic capacity and the current electrostatic capacity is greater than the minimum change, and sets the prior electrostatic capacity of this condition as "minimum electrostatic capacity of auto focusing search range" (S408).

Referring to FIG.5 again, the auto focusing range setting unit (83) may increase the digital code by a first code interval to increase a current applied to the actuator (30), where the electrostatic capacity of the actuator (30) is increased in accordance with the increase of the digital code increasing by the first code interval.

FIG.5 describes the minimum electrostatic capacity of approximately 200, where a minimum digital code corresponding to the minimum electrostatic capacity is approximately 612.

FIG.6 is a schematic flowchart illustrating a method setting a maximum value of auto focusing search range according to an exemplary embodiment of the present invention, and FIG.7 is a graph illustrating an electrostatic capacity change of an actuator (30) in response to digital code change of FIG.6.

Referring to FIG.6, the auto focusing range setting unit (83) applies the mth digital code to the moving unit (81) (S601), where m may be 1,023 in case of 10 bit.

Then, the moving unit (81) applies a mth current corresponding to the mth digital code to the actuator (30) (S602). The actuator (30) is formed with the mth electrostatic capacity corresponding to the mth current, and the cap sensor (82) senses the mth electrostatic capacity of the actuator (30) and outputs the electrostatic capacity to the auto focusing range setting unit (83) (S603).

The auto focusing range setting unit (83) outputs to the moving unit (81) a m+1th digital code decreased as much as a second code interval (8 codes in FIG.7) set up by the mth digital code (S604). Then, the moving unit (81) applies to the actuator (30) a m+1th current corresponding to the m+1th digital code (S605). The actuator (30) is formed with a m+1th electrostatic capacity corresponding to the m+1th current and the cap sensor (82) senses the m+1th electrostatic capacity of the actuator (30) and outputs the m+1th electrostatic capacity of the actuator (30) to the auto focusing range setting unit (83) (S606).

Referring to FIG.7, the mth electrostatic capacity and the m+1th electrostatic capacity may be equal or may be unequal depending on a value of 'm'. The present invention seeks for the m+1th electrostatic capacity where a difference between the m+1th electrostatic capacity and the mth electrostatic capacity is greater than a set "maximum change". Therefore, the auto focusing range setting unit (83) compares in case that the difference between the m+1th electrostatic capacity and the mth electrostatic capacity is less than or greater than the set maximum change (S607). At this time, the maximum change is a predetermined value and may be variably set up depending on type of actuator (30) and the manufacturer.

In case that the difference between the m+1th electrostatic capacity and the mth electrostatic capacity is greater than the set maximum change (S607), the auto focusing range setting unit (83) sets the mth electrostatic capacity of this condition as "maximum electrostatic capacity of auto focusing search range" (S608). Then, the auto focusing range setting unit (83) outputs to the memory unit (84) a maximum digital code corresponding to the maximum electrostatic capacity of auto focusing search range, where the memory unit (84) is stored with the maximum digital code of the auto focusing search range (S609).

However, in case that the difference between the m+1th electrostatic capacity and the mth electrostatic capacity is less than the maximum electrostatic capacity (S607), the auto focusing range setting unit (83) repeats the steps from S604 to S607 to seek for a mth electrostatic capacity where the difference between the m+1th electrostatic capacity and the mth electrostatic capacity is greater than the maximum change, and sets the mth electrostatic capacity of this condition as "maximum electrostatic capacity of auto focusing search range" (S608).

Referring to FIG.7 again, the auto focusing range setting unit (83) may decrease the digital code by a second code interval to decrease a current applied to the actuator (30), where the electrostatic capacity of the actuator (30) is decreased in accordance with the decrease of the digital code decreasing by the second code interval.

Although FIG. 7 describes the maximum electrostatic capacity of approximately 495, a maximum digital code corresponding to the maximum electrostatic capacity is approximately 885.

As apparent from the foregoing, electrostatic capacity of an actuator can be detected and analyzed to set up an auto focusing search range of the actuator without the conventional separate devices as employed in laser displacement or image test.

Furthermore, a time for searching for an unnecessary dead zone for auto focusing can be reduced and the auto focusing speed can be enhanced by driving the actuator within an auto focusing search range stored in the memory unit (84) under a shooting (photographing) mode.

Now, referring to the graphs in FIGS.5 and 7, the electrostatic capacity of actuator is decreased in its change as the digital code is decreased, and the change is increased as the digital code is increased.

Therefore, in the method for setting a minimum value of the auto focusing search range according to the present invention, in consideration of the fact that the electrostatic capacity change is small, the first code interval is set relatively greater than the second code interval, and in the method for setting a maximum value of the auto focusing search range according to the present invention, in consideration of the fact that the electrostatic capacity change is large, the second code interval is set relatively smaller than the first code interval.

In the present invention, in consideration of the fact that the electrostatic capacity of actuator is decreased in its change as the digital code is decreased, and the change is increased as the digital code is increased, the maximum change is set greater than the minimum change.

As apparent from the foregoing, a numerical value necessary for setting an auto focusing search range is set up in consideration of the fact that the electrostatic capacity change of an actuator becomes smaller as a digital code is smaller, and the electrostatic capacity change of an actuator becomes larger as the digital code is larger, to thereby increase a search accuracy of minimum value and maximum value of the auto focusing search range.

The previous description of the present invention is provided to enable any person skilled in the art to make or use the invention. Various modifications to the invention will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the invention. Thus, the invention is not intended to limit the examples described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The present invention has industrial applicability in that a time for searching for an unnecessary dead zone for auto focusing can be reduced and the auto focusing speed can be enhanced by driving the actuator within an auto focusing search range stored in the memory unit (84) under a shooting (photographing) mode.

Claims

A camera module, comprising: an actuator increasing an electrostatic capacity in response to intensity of applied voltage or current; and an actuator driving unit applying a voltage or a current to the actuator, wherein the actuator driving unit includes a cap sensing unit sensing electrostatic capacity of the actuator, and an auto focusing range setting unit setting up an auto focusing search range of the actuator by using electrostatic capacity change sensed by the cap sensing unit under an auto focusing search range set-up mode.
The camera module of claim 1, wherein the actuator driving unit further includes a memory storing the auto focusing search range set up by the auto focusing range setting unit, and the actuator driving unit applies a current or a voltage corresponding to the auto focusing search range stored in the memory under a photographing (shooting mode).
The camera module of claim 1, wherein the auto focusing range setting unit gradually increases a digital code at a set first code interval, and sets up a first prior electrostatic capacity at a minimum electrostatic capacity of the auto focusing search range in case that a difference between the first prior electrostatic capacity of the actuator corresponding to the increase of the digital code and a first current electrostatic capacity is more than a set minimum change.
The camera module of claim 1, wherein the auto focusing range setting unit gradually decreases a digital code at a set second code interval, and sets up a second prior electrostatic capacity at a maximum electrostatic capacity of the auto focusing search range in case that a difference between the second prior electrostatic capacity of the actuator corresponding to the decrease of the digital code and a second current electrostatic capacity is more than a set maximum change.
The camera module of claims 3 and 4, wherein the first code interval is greater than the second code interval.
The camera module of claim 1, wherein the actuator is an actuator connected to a moving lens to vertically move the moving lens along an optical axis in response to the electrostatic capacity formed by the current or voltage applied from the actuator driving unit.
A method for setting up an auto focusing search range of an actuator in which electrostatic capacity changes in response to intensity of applied current or voltage, the method comprising: applying to the actuator a current or a voltage corresponding to a digital code changing by increasing a digital code at a set first code interval under an auto focusing search range setting mode (a); sensing the electrostatic capacity change of the actuator (b); comparing a prior electrostatic capacity and a current electrostatic capacity of the actuator (c); and setting the prior electrostatic capacity as a minimum electrostatic capacity in case that a difference between the prior electrostatic capacity and the current electrostatic capacity is more than a set minimum change (d).
The method of claim 7, wherein the (a) step and the (c) step are repeatedly performed in case that the difference between the prior electrostatic capacity and the current electrostatic capacity is less than the set minimum change.
The method of claim 7, further comprising: storing a minimum digital code corresponding to the minimum electrostatic capacity of the auto focusing search range (e).
The method of claim 9, further comprising: applying to the actuator only a current or a voltage higher than a current or voltage corresponding to the minimum digital code stored under a photographing mode (f).
The method of claim 7, wherein the actuator is an actuator connected to a moving lens to vertically move the moving lens along an optical axis in response to the electrostatic capacity formed by the current or voltage applied from the actuator driving unit, and the digital code is a code corresponding to a distance moved by a moving lens.
A method for setting up an auto focusing search range of an actuator in which electrostatic capacity changes in response to intensity of applied current or voltage, the method comprising: applying to the actuator a current or a voltage corresponding to a digital code changing by decreasing a digital code at a set second code interval under an auto focusing search range setting mode (a); sensing the electrostatic capacity change of the actuator (b); comparing a prior electrostatic capacity and a current electrostatic capacity of the actuator (c); and setting the prior electrostatic capacity as a maximum electrostatic capacity in case that a difference between the prior electrostatic capacity and the current electrostatic capacity is more than a set maximum change (d).
The method of claim 12, wherein the (a) step and the (c) step are repeatedly performed in case that the difference between the prior electrostatic capacity and the current electrostatic capacity is less than the set maximum change.
The method of claim 12, further comprising: storing a maximum digital code corresponding to the maximum electrostatic capacity of the auto focusing search range (e).
The method of claim 12, further comprising: applying to the actuator only a current or a voltage less than a current or voltage corresponding to the maximum digital code stored under a photographing mode (f).
The method of claim 12, wherein the actuator is an actuator connected to a moving lens to vertically move the moving lens along an optical axis in response to the electrostatic capacity formed by the current or voltage applied from the actuator driving unit, and the digital code is a code corresponding to a distance moved by a moving lens.
A method for setting up an auto focusing search range of an actuator in which electrostatic capacity changes in response to intensity of applied current or voltage, the method comprising: applying to the actuator a current or a voltage corresponding to a digital code changing by increasing a minimum digital code at a set first code interval under an auto focusing search range setting mode (a); sensing the electrostatic capacity change of the actuator (b); comparing a first prior electrostatic capacity and a first current electrostatic capacity of the actuator (c); setting the first prior electrostatic capacity as a minimum electrostatic capacity of the auto focusing search range in case that a difference between the first prior electrostatic capacity and the first current electrostatic capacity is more than a set minimum change (d); applying to the actuator a current or a voltage corresponding to a digital code changing by decreasing a maximum digital code at a set second code interval (e); sensing the electrostatic capacity change of the actuator (f); comparing a second prior electrostatic capacity and a second current electrostatic capacity of the actuator (g); and setting the second prior electrostatic capacity as a maximum electrostatic capacity of the auto focusing search range in case that a difference between the second prior electrostatic capacity and the second current electrostatic capacity is more than a set maximum change (h).
The method of claim 17, further comprising: storing a minimum digital code corresponding to the minimum electrostatic capacity of the auto focusing search range and a maximum digital code corresponding to the maximum electrostatic capacity of the auto focusing search range (i).
The method of claim 18, further comprising: applying to the actuator a current or a voltage higher than a current or voltage corresponding to the minimum digital code stored under a photographing mode, and applying to the actuator a current or a voltage less than a current or voltage corresponding to the maximum digital code stored under a photographing mode (j).
The method of claim 17, wherein the first code interval is greater than the second code interval.