KR20200118782A - Camera module and method for auto focusing the same - Google Patents

Abstract

The present invention relates to a camera module and to an auto-focusing method thereof. That is, the camera module of the present invention comprises: an actuator for moving a mover including at least one lens to which an optical image of a subject is incident; and an actuator driving unit controlling the actuator to drive the mover in a forward or reverse direction. When a search section for driving the mover in the forward direction is defined as a first search section, and a search section for driving the mover in the reverse direction is defined as a second search section, separate direction bits are included to drive the first search section and the second search section. According to the present invention, the current consumption of the camera module can be reduced, the resolution can be increased, and an algorithm for driving the actuator can be simplified.

Description

Camera module and its auto focusing method {CAMERA MODULE AND METHOD FOR AUTO FOCUSING THE SAME}

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 are being developed.

In the case of a conventional digital camera module applied to a mobile phone, etc., it was not possible to adjust the distance between the image sensor and the lens that converts external light into a digital image or a digital image. The same lens driving device has been developed to obtain an improved digital image or digital image from the camera module.

In general, in a voice coil motor applied to a camera module, a mover having a lens mounted therein moves from a base to an upper portion to adjust the distance between the lens and an image sensor disposed at the rear of the base.

Conventional voice coil motors have a structure in which an elastic member presses a mover to contact the base when a driving signal is not applied.

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

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

However, the mover of a conventional voice coil motor not only has displacement according to the attitude of the voice coil motor, but also includes a non-driving section that is not driven even when a driving signal is applied, but the mover is driven by an auto focusing algorithm that does not reflect this. It has a problem that it takes a lot of time.

The present invention is to solve the problem of reducing the current consumption of the camera module, increasing the resolution, and simplifying the algorithm for driving the actuator.

The present invention,

An actuator for moving a mover including at least one lens for incident light image of a subject;

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

When a search section for driving the mover in the forward direction is defined as a first search section and a search section for driving the mover in a reverse direction is defined as a second search section, the first search section and the second search section are driven For this purpose, a camera module including a separate direction bit is provided.

Further, according to an embodiment of the present invention, codes allocated to drive the first search interval may be -1023 to 0, and codes allocated to drive the second search interval may be 0 to 1023.

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

Here, according to an embodiment of the present invention, codes allocated to drive the first search interval may be -1023 to 0, and codes allocated to drive the second search interval may be 0 to 1023. In other words, it has twice the resolution using the same number of bits and direction bits.

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

In addition, the first search section and the second search section may be asymmetric.

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

In addition, a posture detection unit for detecting the posture of the mover and outputting posture data; It may further include a control unit for outputting a control signal to the actuator driving unit with the attitude data output from the posture detection 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 part formed thereon; A stator having the first driving part and a second driving part for driving the mover by the action of electromagnetic force; A lower stopper in which the stator is fixed and stops the mover; An upper stopper function for stopping the mover may be included.

In addition, the upper stopper may include a cover.

In addition, the lower stopper may include a base.

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

Further, 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,

Moving a mover including a lens to infinity or macro;

Starting the mover movement at the infinity or the macro to search for a best focusing point;

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

There is provided an auto-focusing method of a camera module that focuses forward and backward with a separate direction bit.

The present invention,

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

Determining whether an increase in a focusing value is in an infinite direction or a macro direction in the first search;

When the focusing value increases in the direction of infinity, searching for a best focusing point by moving the mover to the infinity;

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

In addition, in the first search, in the step of determining whether an increase in a focusing value is in an infinite direction or a macro direction in the first search, when a focusing value increases in the macro direction, A step of searching for a best focusing point may be performed by moving the mover with the macro.

In addition, a function of lowering a mechanical impact sound may be included in a longer time compared to other steps when a moving time is initially moved in the infinite direction or the macro direction.

In addition, a function of reducing the mechanical impact sound by dividing a step size that moves in the infinite direction or the macro direction when the first movement is performed may be divided into several steps.

In the present invention, a current value can be designated for each address by allocating a search section that can be driven in the forward and reverse directions from -1023 to 1023 bits, including direction bits in the forward and reverse directions, 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, according to the present invention, there is an effect of detecting a posture of a voice coil motor or a lens and controlling the voice coil motor with this posture data to reduce current consumption and drive a camera module with optimization.

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

1 is a block diagram showing 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 according to an embodiment of the present invention is positioned in an upward direction
3 is a conceptual cross-sectional view illustrating that a lens of a camera module according to an embodiment of the present invention is positioned in a lateral direction
4 is a conceptual cross-sectional view illustrating that a lens of a camera module according to an embodiment of the present invention is positioned in a downward direction
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, embodiments of 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 description. In addition, terms specifically defined in consideration of the configuration and operation of the present invention may vary according to the intention or custom of users or operators. Definitions of these terms should be made based on the contents throughout the present 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 direction), and codes allocated for driving in both directions may be -1023 to 1023.

That is, an actuator 200 for moving a movable member including at least one lens to which an optical image of a subject is incident; In order to drive the mover in both directions, it includes an actuator driving unit 210 that controls the actuator 200.

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

A plurality of codes for controlling a 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 the search section for driving the mover in the reverse direction is defined as a first search section, and when the search section for driving the mover in the forward direction is defined as the second search section, allocated to drive the first search section The code is -1023 to 0, and the code allocated to drive the second search section is 0 to 1023, or the code assigned to drive the first search section is 0 to 1023, and the second search section A code allocated to drive may be -1023 to 0.

For example, codes allocated to drive the first search interval and the second search interval may be -1023 to 1023.

In this case, a code assigned to drive the first search section may be -1023 to 0, and a code assigned to drive the second search section may be 0 to 1023.

In addition, the first search interval and the second search interval may be symmetrical or asymmetric.

Therefore, the present invention can drive in the forward and reverse directions in -1023 to 1023 codes by adding direction bits in the forward and reverse directions, so that the camera can have a resolution of 1 times 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 outputting the posture data by detecting the posture of the mover; It may further include a control unit 220 for outputting a control signal to the actuator driving unit 210 with the attitude data output from the posture detection unit 230.

That is, the posture detection unit 230 detects the posture of the mover and outputs posture data, and the control unit 220 receives posture data from the posture detector 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 detector 230 may sense three or more postures of the lens, but in an embodiment of the present invention, for convenience of explanation, the posture detector 230 is ) It will be described how to sense three postures, such as posture and down posture.

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

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

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

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

As described above, FIG. 2 shows an up position in which the lens of the camera module is positioned in the upward direction, and the "up position" refers to 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 “side posture” refers to the optical axis of the lens 135 of the mover 130 of the voice coil motor. 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 a downward direction, and the "down posture" refers to 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 the voice motor coils. Can be a part of 100.

Referring to FIG. 2, the voice coil motor 100 performs an auto focusing function by driving the mover 130 in a forward or reverse direction.

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 through a central portion is formed, and the base 110 serves as a lower stopper of the mover 130.

In addition, the image sensor 500 may be disposed at the rear of the base 110 or at the rear of the base 110. The image sensor 500 changes 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, a storage space may be formed inside the stator 120, and the mover 130 may be located in the storage space.

In addition, the elastic member 140 has one side fixed to the mover 130 and the other side opposite to the one side fixed to the stator 120, so that the elastic member 140 makes the mover 130 resilient. Can be supported by

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

Further, the cover 150 is fixed to the base 110, and the cover 150 surrounds the stator 120 and the mover 130. In addition, the cover 150 serves as an upper stopper for stopping the mover 130.

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

5 is a graph showing 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 direction) and assigning codes to -1023 to 1023 for driving in both directions.

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

Here, the number of codes allocated to the reverse direction may increase or decrease according to the 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 may be +50 mA.

6 is a flowchart of a method for autofocusing 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 to move to search for the best focusing point (step S110).

Here, in the step S100, when the mover moves to the infinity, the mover moves from the infinity to the macro to search for the best focusing point, and when the mover moves to the macro, the macro to the infinity The mover is moved to search for the best focusing point.

In addition, the search for the best focusing point can be searched by giving a tilt, and the impact sound of the instrument of the camera module can be reduced.

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 searched best focusing point (S120).

In addition, another method for auto-focusing of a camera module of the present invention includes the steps of performing a first search by moving a mover including a lens; Determining whether an increase in a focusing value is in an infinite direction or a macro direction in the first search; When the focusing value increases in the direction of infinity, searching for a best focusing point by moving the mover to the infinity; It may include performing focusing to the searched best focusing point.

And, in the step of determining whether the increase of the focusing value is in the infinite direction or the macro direction by the first search, when the focusing value increases in the macro direction, the mover moves to the macro. By doing so, the step of searching for the best focusing point may be performed.

In addition, a function of lowering the mechanical impact sound for a longer time compared to other steps when the moving time is initially moved in the infinite direction or the macro direction may be included.

In addition, a function of reducing the mechanical impact sound by dividing a step size that moves in the infinite direction or the macro direction when the first movement is performed may be divided into several steps.

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

Claims (1)

Base;
A cover fixed to the base;
A mover disposed in the cover;
An elastic member coupled to the mover;
An actuator including a coil disposed on the mover and a magnet facing the coil; And
Including an actuator driving part for controlling the actuator to move the mover,
At an initial position where no current is applied to the actuator, the movable member is spaced apart from the cover by a first gap and spaced apart from the base by a second gap,
The actuator driving unit moves the mover in a forward direction toward the cover so that the first gap decreases, or moves the mover in a reverse direction toward the base so that the second gap decreases,
Among the plurality of sections in the process of moving the mover from the initial position to the focusing point, the first section occurs before the second section,
A camera module in which time consumed when moving the mover in the first section is longer than a time consumed when moving the mover in the second section compared to a moving distance.

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