KR20200120597A - 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 includes: 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 in order to drive the mover in a forward or reverse direction. A search section for driving the mover in the forward direction is defined as a first search section. When a search section for driving the mover in the reverse direction is defined as a second search section, the first search section or the second search section is included.

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 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 the search section for driving the mover in the forward direction is defined as a first search section and the search section for driving the mover in the reverse direction is defined as the second search section, the first search section or the second search section is included. A camera module is provided.

In addition, in an embodiment of the present invention, half may be allocated to drive the first search interval, and the other half may be allocated to drive the second search interval.

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

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

Also, a code allocated between the first search interval and the second search interval may be in a range of 300 to 500.

In addition, a code allocated between the first search interval and the second search interval may be within a range of 500 to 1000.

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.

Further, 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 base having the stator fixed and performing a lower stopper function for stopping the mover; It may include a cover that performs a function of the upper stopper stopping the mover.

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

Further, the first driving part may be a wound coil, the second driving part may be a magnet, or the first driving part may be a magnet, and the second driving part 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;

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

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.

The present invention detects the attitude of the voice coil motor or lens, and controls the voice coil motor with this attitude data, thereby reducing current consumption and driving the camera module through optimization.

In addition, the present invention can designate a current value for each gig address by allocating a search section that can be driven in the forward and reverse directions from the bit, including directional bits in the forward and reverse directions, thereby simplifying the algorithm for driving the actuator. There is an effect.

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 a first embodiment of the present invention
7 is a flowchart of an autofocusing method of a camera module according to a second 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.

A camera module according to an embodiment of the present invention includes an actuator 200 for moving a mover 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 be formed by a plurality of bits including a direction bit. Each of the plurality of bits may selectively include any one of 0 and 1. The plurality of bits may include a total of 10 bits, and the plurality of codes may include a total of 1024 pieces (2 ¹⁰ pieces) corresponding to 0 to 1023. That is, each of the plurality of codes may be a binary number of up to 10 digits.

And, when the search section for driving the mover in the forward direction is defined as a first search section and the search section for driving the mover in the reverse direction is defined as the second search section, the first search section or the second search section It may include.

In addition, half of the plurality of codes may be allocated to drive the first search period, and the other half of the plurality of codes may be allocated to drive the second search period.

For example, codes allocated to drive the first search interval and the second search interval may be 0 to 1023. The least significant bit (LSB) may be a bit position that becomes a unit value for determining whether a binary integer is an even number or an odd number.

In this case, codes assigned to drive the first search section may be 0 to 513, and codes assigned to drive the second search section may be 513 to 1023.

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

In addition, a code allocated between the first search interval and the second search interval may be within a range of 300 to 500.

In addition, a code allocated between the first search interval and the second search interval may be within a range of 500 to 1000.

Therefore, in the present invention, by adding direction bits in the forward and reverse directions, a search section capable of driving in the forward and reverse directions from 0 to 1023 codes can be assigned to designate a current value for each address, so whether the actuator should move in the reverse direction Since there is no need for information on whether to move to and from, there is an advantage that the algorithm for driving the actuator can be simplified.

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.

In the camera module according to an embodiment of the present invention, 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 513, and the mover is driven in the forward direction (+). Codes allocated to drive the second search section are 513 to 1023.

Here, the number of bits allocated to the reverse direction may increase or decrease according to a reverse stroke or a current value.

And, when the code is 0, the current value is -50mA, when the code is 513, the current value is 0mA, and when the code is 1023, the current value may be +50mA.

6 is a flowchart of a method for auto-focusing of a camera module according to a first embodiment of the present invention, and FIG. 7 is a flowchart of a method for auto-focusing of a camera module according to a second embodiment of the present invention.

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

Then, at the infinity or the macro, the mover starts to move to search for a 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 initial steps 1 and 2 of the search for the best focusing point may be tilted or divided into steps so that the camera module may reduce the mechanical impact of the upper or lower stopper.

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

And, in the auto-focusing method of the camera module according to the second embodiment, as shown in FIG. 7, a first search is performed by moving a mover including a lens (step S200).

Subsequently, as the first search, it is determined whether the increase of the focusing value is in an infinite direction or a macro direction (step S210).

Thereafter, when the focusing value increases in the direction of infinity, the mover is moved to the infinity to search for a best focusing point (step S220).

Here, in the step S210, when the focusing value increases in the macro direction, the mover is moved to the macro to search for the best focusing point (step S230).

Then, focusing is performed to the searched best focusing point (step S240).

In this case, a function of lowering the 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.

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 including an upper plate and a side plate extending from the upper plate and fixed to the base;
A mover disposed in the cover;
A coil disposed on the mover;
A magnet disposed in the cover and facing the coil;
An elastic member coupled to the mover; And
Including an actuator driving unit for applying a current to the coil,
At an initial position where no current is applied to the coil, the mover is spaced apart from the top plate of the cover by a first gap and spaced apart from the base by a second gap,
Directional bits are allocated to the actuator driving unit,
The direction bit selectively includes any one of forward movement information in which the mover moves toward the cover to decrease the first gap and reverse movement information in which the mover moves toward the base to decrease the second gap. Camera module.

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