KR20210128963A - Camera module and method for auto focusing the same - Google Patents

Abstract

The present invention relates to a camera module and an auto-focusing method thereof. That is, the camera module of the present invention includes: an actuator for moving a mover including at least one lens for projecting the optical image of a subject; and an actuator driving part for controlling the actuator to drive the mover in the forward or reverse direction. When a search section in which the mover is driven in the forward direction is defined as a first search section and a search section in which the mover is driven in a reverse direction is defined as a second search section, a separate direction bit is included to drive the first and second search sections.

Description

Camera module and autofocusing method thereof

The present invention relates to a camera module and an auto-focusing method thereof.

Recently, mobile phones and tablet PCs with built-in micro camera modules have been developed.

In the case of a digital camera module applied to a conventional mobile phone, etc., the distance between the image sensor and the lens for changing external light into a digital image or digital image could not be adjusted. The same lens driving device has been developed so that a more improved digital image or digital image can be obtained from the camera module.

In general, in a voice coil motor applied to a camera module, a mover equipped with a lens moves upward from the base to adjust the distance between the lens and the image sensor disposed on the back of the base.

The conventional voice coil motor has a structure in which the elastic member presses the mover to contact the base when no driving signal is applied.

That is, in the conventional voice coil motor, since the elastic member presses the mover, in order for the mover to be separated from the base, the electromagnetic force for driving the mover must be greater than the elastic force of the elastic member and the weight of the mover.

Also, the mover of the conventional voice coil motor has a displacement of about 30 μm to 50 μm depending on the posture of the voice coil motor.

However, since the mover of the conventional voice coil motor has a displacement according to the posture of the voice coil motor and includes an undriven section that is not driven even when a driving signal is applied, the mover is driven by an autofocusing algorithm that does not reflect this. There is a problem that takes a lot of time.

(Patent Document 1) KR10-0952488 B1

The present invention can reduce the current consumption of the camera module, increase the resolution, and solve the problems that can simplify the algorithm for driving the actuator.

The present invention is

an actuator for moving a mover including at least one lens that is incident on an optical image of a subject;

In order to drive the mover in the forward or reverse direction, comprising an actuator driving unit for controlling the actuator,

When a search section in which the mover is driven in the forward direction is defined as a first search section and a search section in which the mover is driven in a reverse direction is defined as a second search section, the first and second search sections are driven In order to do this, a camera module including a separate direction bit is provided.

And, according to an embodiment of the present invention, the code allocated to drive the first search period may be -1023 to 0, and the code allocated to drive the second search period may be 0 to 1023.

In addition, codes allocated to drive the first search period may be 0 to 1023, and codes allocated to drive the second search period may be -1023 to 0.

Here, in an embodiment of the present invention, codes allocated for driving the first search period may be -1023 to 0, and codes allocated for driving the second search period may be 0 to 1023. That is, it has twice the resolution using the same number of bits and direction bits.

In addition, the first search period and the second search period may be symmetrical.

Also, the first search interval and the second search interval may be asymmetric.

In addition, the actuator may be one of a voice coil motor (VCM) actuator, an actuator driven by piezoelectric force, and a MEMS actuator driven by a capacitive method.

In addition, a posture detection unit for detecting the posture of the mover and outputting posture data; The controller may further include a control unit for outputting a control signal to the actuator driving unit as the posture data output from the posture sensing unit.

In addition, the posture of the mover may be one of an up posture, a side posture, and a down posture of the lens.

In addition, the actuator may include a mover including the lens and having a first driving unit formed thereon; a stator having a second driving unit configured to drive the movable element by the action of the first driving unit and electromagnetic force; a lower stopper to which the stator is fixed and to stop the mover; An upper stopper function to stop the mover may be included.

In addition, the upper stopper may include a cover.

In addition, the lower stopper may include a base.

In addition, the mover may be spaced apart from the cover and the base.

In addition, the first driving unit may be a wound coil, the second driving unit may be a magnet, or the first driving unit may be a magnet, and the second driving unit may be a wound coil.

In addition, the actuator may further include an elastic member having one side fixed to the mover and the other side opposite to the one side fixed to the stator to elastically support the mover.

The present invention is

moving a mover including a lens to infinity or macro;

in the infinity or the macro, starting the mover movement to search for a best focusing point;

Including the step of focusing to the found best (Best) focusing point,

An auto-focusing method of a camera module that focuses in a forward and reverse direction with a separate direction bit is provided.

The present invention is

performing a first search by moving a mover including a lens;

determining, in the first search, whether an increase in a focusing value is in a direction of infinity or a direction of a macro;

when the focusing value increases in the infinity direction, moving the mover toward infinity to search for a best focusing point;

There is provided an auto-focusing method of a camera module including performing focusing to the found best focusing point.

And, in one embodiment of the present invention, in the step of determining whether the increase of the focusing value is in the infinity direction or the macro direction in the first search, when the focusing value increases in the macro direction, Searching for a best focusing point may be performed by moving the mover to the macro.

In addition, a function for lowering the mechanical impact sound may be included for a longer time compared to other steps when the first movement is performed in the infinity direction or the macro direction.

In addition, a function of lowering the mechanical impact sound may be included by dividing the first moving step size in the infinity direction or the macro direction into several steps.

The present invention assigns a search section that can be driven in the forward and reverse directions from -1023 to 1023 bits, including the direction bits in the forward and reverse directions, so that the current value can be specified for each address, thereby simplifying the algorithm for driving the actuator. There is an effect that can be done.

In addition, the present invention has the effect of increasing the resolution by driving in both directions.

In addition, the present invention has the effect of detecting the posture of the voice coil motor or the lens, controlling the voice coil motor with the posture data, reducing current consumption, and driving the camera module by optimization.

In addition, the present invention has the effect of solving the defocus problem by applying a current in the opposite direction even when a change in the spring occurs because the mover can be driven in both directions.

1 is a block diagram illustrating a camera module according to an embodiment of the present invention;
2 is a conceptual cross-sectional view for explaining that the lens of the camera module is located in the upper direction according to an embodiment of the present invention;
3 is a conceptual cross-sectional view for explaining that the lens of the camera module is positioned in the lateral direction according to an embodiment of the present invention;
4 is a conceptual cross-sectional view for explaining that a lens of a camera module is positioned in a downward direction according to an embodiment of the present invention;
5 is a graph showing current-distance characteristics of a camera module according to an embodiment of the present invention;
6 is a flowchart of an auto-focusing method of a camera module according to an embodiment of the present invention;

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings. In this process, the size or shape of the components shown in the drawings may be exaggerated for clarity and convenience of explanation. In addition, the terms specifically defined in consideration of the construction and operation of the present invention may vary depending on the intention or custom of the user or operator. Definitions of these terms should be made based on the content throughout this specification.

1 is a block diagram of a camera module according to an embodiment of the present invention.

The camera module according to an embodiment of the present invention drives a mover including at least one lens in both directions (forward or reverse), and codes allocated for bidirectional driving may be -1023 to 1023.

That is, the actuator 200 for moving the mover including at least one lens incident on the optical image of the subject; In order to drive the mover in both directions, an actuator driving unit 210 for controlling the actuator 200 is included.

Here, the actuator driving unit 210 controls the actuator 200 to drive the mover in the forward or reverse direction.

A plurality of codes for controlling the current applied to the coil of the actuator 200 may be allocated to the actuator driving unit 210 . Each of the plurality of codes may include a direction bit and 10 bits other than the direction bit. Each of the 10 bits other than the direction bit may selectively include any one of 0 and 1. The plurality of codes may include codes corresponding to -1023 to +1023.

And, when a search section for driving the mover in the reverse direction is defined as a first search section and a search section for driving the mover in a forward direction is defined as a second search section, The code is -1023 to 0, the code allocated to drive the second search interval is 0 to 1023, or the code allocated to drive the first search interval is 0 to 1023, and the second search interval The code allocated to drive the ? may be -1023 ~ 0.

As an example, codes allocated to drive the first search period and the second search period may be -1023 to 1023.

In this case, the code allocated to drive the first search interval may be -1023 to 0, and the code allocated to drive the second search interval may be 0 to 1023.

Also, the first search interval and the second search interval may be symmetric or asymmetric.

Therefore, in the present invention, by adding direction bits in the forward and reverse directions, it is possible to drive in the forward and reverse directions in the -1023 to 1023 codes, so that the resolution can be achieved by one time with the same number of bits compared to when there is no direction bit. The resolution of the module can be increased.

On the other hand, the camera module according to an embodiment of the present invention, as shown in Figure 1, the posture detection unit 230 for detecting the posture of the mover and outputting the posture data; The controller 220 may further include a control signal for outputting a control signal to the actuator driver 210 as the posture data output from the posture sensing unit 230 .

That is, the posture detecting unit 230 detects the posture of the mover and outputs posture data, and the controller 220 receives the posture data from the posture detecting unit 230 and corresponds to the posture of the mover. A control signal is output to the actuator driving unit 210 , and the actuator driving unit 210 drives the actuator 200 to suit the posture of the mover.

In this case, the posture of the mover may be one of an up posture, a side posture, and a down posture of the lens, as described later.

Here, the posture detecting unit 230 may sense three or more postures of the lens, but in an embodiment of the present invention, the posture detecting unit 230 is an up posture of the lens and a side for convenience of description. ) and the sensing of three postures, such as a down posture, will be described.

In addition, the actuator 200 may be one of a voice coil motor (VCM) actuator, an actuator driven by piezoelectric force, and a MEMS actuator driven by a capacitive method.

For example, the voice coil motor drives the mover by electromagnetic force to auto-focus the camera module.

In addition, the posture sensor 230 may include a gyro sensor that senses the direction of gravity.

Figure 2 is a conceptual cross-sectional view for explaining that the lens of the camera module according to an embodiment of the present invention is located in the upper direction, Figure 3 is that the lens of the camera module according to the embodiment of the present invention is located in the lateral direction It is a conceptual cross-sectional view for explaining, FIG. 4 is a conceptual cross-sectional view for explaining that the lens of the camera module according to an embodiment of the present invention is located in the downward direction.

As described above, FIG. 2 shows an up posture in which the lens of the camera module is located in the upward direction, and the "up posture" is the lens 135 of the mover 130 of the voice coil motor. It may be defined as a posture in which the optical axis is formed in a direction perpendicular to the ground and the base 110 is disposed to face the ground.

In addition, FIG. 3 shows a side posture in which the lens of the camera module is positioned in the lateral direction, and the "side posture" indicates that the optical axis of the lens 135 of the mover 130 of the voice coil motor is on the ground. It is formed in a direction parallel to and may be defined as a posture in which the base 110 is disposed perpendicular to the ground.

In addition, FIG. 4 shows a down posture in which the lens of the camera module is located in the downward direction, and the "down posture" is the lens 135 of the mover 130 of the voice coil motor 100 . It may be defined as a posture in which the optical axis is formed in a direction perpendicular to the ground and the cover 150 is disposed to face the ground.

Here, in FIGS. 2 to 4, the voice coil motor 100 is applied as an actuator, and the mover 130, the stator 120, the base 110, the elastic member 140 and the cover 150 are voice motor coils. It can be a part of (100).

Referring to FIG. 2 , the voice coil motor 100 drives the mover 130 in a forward or reverse direction to perform an auto-focusing function.

For example, the mover 130 mounted on the voice coil motor 100 is driven in a forward direction rising to the cover 150 or driven in a reverse direction falling to the base 110, and in this process, the lens ( 135) and a focusing operation is performed between the image sensor 500 .

That is, the mover 130 is spaced apart from the cover 150 and the base 110 .

In addition, the base 110 is formed in a plate shape in which an opening through which light passes is formed in the center, and the base 110 serves as a lower stopper of the mover 130 .

In addition, the image sensor 500 may be disposed on the rear side of the base 110 or on the rear side of the base 110 . The image sensor 500 converts the light focused through the lens of the mover 130 into a digital image or a moving picture.

In addition, the stator 120 is fixed on the base 110 .

Here, the first driving unit 138 may be a magnet, and the second driving unit 125 may be a wound coil.

Conversely, the first driving unit 138 may be a wound coil, and the second driving unit 125 may be a magnet.

In addition, an accommodation space may be formed inside the stator 120 , and the mover 130 may be located in the accommodation space.

In addition, one side of the elastic member 140 is fixed to the mover 130 and the other side opposite to the one side is fixed to the stator 120 , so that the elastic member 140 elastically holds the mover 130 . can be supported by

In one embodiment of the present invention, the elastic member 140 includes a first elastic member 143 formed at the lower end of the outer circumferential surface of the mover 130 and a second elastic member formed at the upper end of the outer circumferential surface of the mover 130 ( 146) may be included.

In addition, the cover 150 is fixed to the base 110 , and the cover 150 surrounds the stator 120 and the mover 130 . Also, the cover 150 serves as an upper stopper that stops the mover 130 .

Therefore, the present invention has the effect of solving the defocus problem by applying a current in the opposite direction even when a change in the spring occurs because the mover can be driven in both directions.

5 is a graph illustrating current-distance characteristics of a camera module according to an embodiment of the present invention.

As described above, the camera module according to an embodiment of the present invention can increase the resolution by driving the mover in both directions (forward or reverse) and assigning codes from -1023 to 1023 for bidirectional driving.

That is, in the camera module, codes assigned to drive the first search section in which the mover including the lens is driven in the reverse (-) direction are 0 to -1023, and the second search in which the mover is driven in the forward (+) direction. Codes allocated to drive the section are 0 to 1023.

Here, the number of codes allocated to the reverse direction may be increased or decreased according to a reverse stroke or current value.

And, when the code is 0, the current value is 0 mA, when the code is -1023, the current value is -50 mA, and when the code is 1023, the current value is +50 mA.

6 is a flowchart of an auto-focusing method of a camera module according to an embodiment of the present invention.

In the auto-focusing method of the camera module according to the first embodiment, as shown in FIG. 6 , a mover including a lens moves to infinity or macro. (Step S100 )

Then, in the infinity or the macro, the mover starts moving to search for a best focusing point. (Step S110)

Here, in step S100, when the mover moves to infinity, the mover moves from infinity to the macro to search for a best focusing point, and when the mover moves to the macro, the mover moves from the macro to the infinity to search the best focusing point by moving the mover.

And, the search for the best (Best) focusing point can be searched by giving a slope, and it is possible to lower the instrument impact sound of the camera module.

In addition, the code assigned to the step of searching for the best focusing point is -1023 to 1023, the code assigned to the infinity is -1023, and the z code assigned to the macro is 1023.

Subsequently, focusing is performed to the found best focusing point (S120).

In addition, another auto-focusing method of a camera module of the present invention includes the steps of moving a mover including a lens to perform a first search; determining, in the first search, whether an increase in a focusing value is in a direction of infinity or a direction of a macro; when the focusing value increases in the infinity direction, moving the mover toward infinity to search for a best focusing point; The method may include performing focusing to the found best focusing point.

And, in the step of determining whether the increase of the focusing value is in the infinity direction or the macro direction in the first search, if the focusing value increases in the macro direction, move the mover to the macro Thus, a step of searching for a best focusing point may be performed.

In addition, a function of lowering the mechanical impact sound may be included for a longer time compared to other steps when the first movement is performed in the infinity direction or the macro direction.

In addition, a function of lowering the mechanical impact sound may be included by dividing the first moving step size in the infinity direction or the macro direction into several steps.

Although the embodiments according to the present invention have been described above, it will be understood that these are merely exemplary, and those of ordinary skill in the art may make various modifications and equivalent ranges of the embodiments therefrom. Accordingly, the true technical protection scope of the present invention should be defined by the following claims.

Claims (20)

stator;
a mover disposed within the stator and including a lens;
an actuator for moving the mover in a forward or reverse direction; and
An actuator driving unit for controlling the actuator,
A plurality of codes for controlling the current applied to the actuator are allocated to the actuator driving unit,
The plurality of codes includes a positive code for moving the mover in the forward direction and a negative code for moving the mover in the reverse direction. According to claim 1,
The moving time in the initial section of the mover is longer than the moving time in other sections of the camera module. 3. The method of claim 2,
The stator includes a base and a cover disposed on the base,
In an initial position where no current is applied to the actuator, the mover is spaced apart from the cover by the first gap and spaced apart from the base by the second gap in the optical axis direction,
The actuator driving unit moves the mover in one of the forward direction in which the first gap decreases and the reverse direction in which the second gap decreases. 4. The method of claim 3,
Among a plurality of sections in the process in which the mover moves from the initial position to the focusing point, the initial section occurs before the other sections,
The time consumed when the mover moves in the initial section is longer than the time consumed when the mover moves in the other section compared to the moving distance. 5. The method of claim 4,
In the initial section, the step size compared to the other sections is divided into a plurality of steps to lower the impact sound generated by the mover in contact with the cover or the base. According to claim 1,
The actuator includes a magnet and a coil disposed within the stator and moving the mover,
The actuator driver is a camera module for controlling the current applied to the coil. 7. The method of claim 6,
The actuator driving unit applies a forward current to the coil to move the mover in the forward direction and applies a reverse current to the coil to move the mover in the reverse direction,
The forward current is assigned to the positive code and the reverse current is assigned to the negative code. According to claim 1,
A plurality of bits are allocated to the actuator driving unit,
The code is determined by the plurality of bits,
The plurality of bits includes a direction bit selectively having a positive sign and a negative sign,
The code becomes the positive code when the direction bit has the positive sign, and becomes the negative code when the direction bit has the negative sign. According to claim 1,
A camera module including a first search section in which the mover moves in the forward direction and a second search section in which the mover moves in the reverse direction. 10. The method of claim 9,
A camera module to which half of the plurality of codes is allocated to drive the first search period, and the other half of the plurality of codes is allocated to drive the second search period. 10. The method of claim 9,
A code for driving the second search section is -1023 to 0, and a code for driving the first search section is 0 to 1023. 10. The method of claim 9,
The first search section and the second search section are symmetrical to the camera module. 10. The method of claim 9,
The first search section and the second search section are asymmetrical camera module. 4. The method of claim 3,
It includes an elastic member coupled to the movable member,
The elastic member includes a first elastic member coupled to the upper portion of the movable member, and a second elastic member coupled to the lower portion of the movable member,
The base performs a lower stopper function to stop driving in the reverse direction of the mover,
The cover is a camera module that performs an upper stopper function to stop driving of the mover in the forward direction. According to claim 1,
an image sensor,
The mover is a camera module including a lens disposed at a position corresponding to the image sensor. The camera module of any one of claims 1 to 15;
a posture detecting unit detecting the posture of the mover of the camera module and outputting posture data; and
and a control unit for outputting a control signal to the actuator driving unit of the camera module as the posture data output from the posture sensing unit. stator;
a mover disposed within the stator and including a lens;
an actuator for moving the mover in a forward or reverse direction; and
An actuator driving unit for controlling the actuator,
A plurality of bits for controlling the current applied to the actuator are allocated to the actuator driving unit,
The plurality of bits selectively include a positive sign bit for moving the mover in the forward direction and a negative sign bit for moving the mover in the reverse direction,
The moving time in the initial section of the mover is longer than the moving time in other sections of the camera module. 18. The method of claim 17,
Among a plurality of sections in the process in which the mover moves from the initial position to the focusing point, the initial section occurs before the other sections,
The time consumed when the mover moves in the initial section is longer than the time consumed when the mover moves in the other section compared to the moving distance. The camera module of any one of claims 17 or 18;
a posture detecting unit detecting the posture of the mover of the camera module and outputting posture data; and
and a control unit for outputting a control signal to the actuator driving unit of the camera module as the posture data output from the posture sensing unit. stator;
a mover disposed within the stator and including a lens; and
A camera module including an actuator for moving the mover.

Images