JP2013054221A - Portable electronic device, and autofocus control method used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a portable electronic device that reduces power consumption for driving a lens in a camera.SOLUTION: After a camera censor 50 in a portable telephone 100 is started up, a host CPU 30 controls automatic focus adjustment when it is determined that detection level of an acceleration sensor 40 is within a predetermined range and a camera is being used for imaging, and stops a drive mechanism for automatic focus adjustment when the detection level is out of the predetermined range.

Description

  The present invention relates to a portable electronic device equipped with a camera and a control method thereof.

  In many cases, a portable electronic device such as a cellular phone or a portable information terminal is provided with a camera unit having an autofocus (autofocus) function. In the AF function, the lens part in which the lens is arranged inside the lens barrel is moved away from the image sensor or in a direction in which the lens unit approaches an image sensor, for example, a CMOS (Complementary Metal Oxide Semiconductor) sensor or a CCD (Charge Coupled Device) sensor. Realized by moving in the direction.

  Generally, a voice coil motor (hereinafter referred to as “VCM: Voice Coil Motor”) is adopted as a driving mechanism for moving the lens unit. When the VCM is used, it is possible to realize a camera unit that is small in size, simple in structure, and easy to assemble as compared with the case where other driving mechanisms are used. For this reason, in a portable electronic device such as a cellular phone, a camera unit having an AF function using a VCM is generally used.

  Next, an example of the structure of the VCM will be described. The VCM is mainly composed of a disk-shaped coil and a magnet. One of the coil and the magnet is fixed to the lens unit, and the other of the coil and the magnet is fixed to the housing. The movement of the lens unit is realized by passing a current through the coil.

  VCM is controlled by a motor driver. In general, the motor driver controls the VCM so as to move the lens unit only in one direction, specifically, to move the lens unit only in the direction away from the image sensor. In this case, the lens unit and the housing are connected by an urging spring, and the urging force of the urging spring urges the lens unit in a direction to approach the image sensor.

  In the camera unit having such a configuration, in a natural state where the VCM is not driven, the lens unit is located at a position where it can be focused (focused) far away. On the other hand, when focusing near, the motor driver controls the current to flow through the coil and moves the lens unit away from the image sensor.

  On the other hand, in the case where the focus is set to a distance from the state where the focus is once close, the driving force by the VCM is reduced or eliminated, and the lens unit is brought closer to the image sensor by the biasing force of the biasing spring. Energize.

  With respect to such control during shooting of the AF function, in Patent Document 1, for example, when manual focus position adjustment of a photographer is performed on the premise that control for automatic focus adjustment is performed. A technique is disclosed in which the automatic focus adjustment process is temporarily stopped and the automatic focus adjustment process is restarted again by detecting vibration or the like. Alternatively, Patent Document 2 discloses a technique for calculating the amount of change in the relative angle between the subject and the camera, and reducing unnecessary AF processing when the imaging angle of the camera changes greatly, such as panning. Is disclosed. Although these are based on the premise that AF processing is performed during shooting, the focus position adjustment that cannot be achieved by such automatic focus adjustment may occur due to the intention of the photographer. It is aimed at.

  Further, in Patent Document 3, in a composite camera capable of performing moving image shooting and still image shooting at the same time, moving image shooting is being performed in a display form different from that immediately after still image shooting during moving image shooting. By displaying this, a technique for preventing continued useless video shooting is disclosed.

JP 2004-64713 A JP 2006-301000 A Japanese Patent Laid-Open No. 9-222664

  On the other hand, in recent years, in a mobile phone with an AF function, when the camera is activated, the VCM is energized, and an operation of extending the AF lens position to a certain value is performed in advance. This action avoids the image from appearing blurred if the focus is too far.

  Further, when the shutter is released, an AF operation is executed and focused, and thereafter, the focused state is maintained or returned to the feeding start position.

  However, in any state, since a constant current flows through the coil, power consumption is required accordingly. Since the voltage of the VCM generally does not become a low voltage as a circuit configuration, it cannot be neglected as a camera unit from the viewpoint of power consumption, and becomes a problem as a heat source.

  None of the conventional techniques disclosed in the above-mentioned patent documents consider power consumption in such a case.

  Therefore, an object of the present invention is to provide a portable electronic device capable of realizing low power consumption for driving a lens in an imaging device in a portable electronic device in which an imaging device having an automatic focus adjustment function is built in a housing. An object is to provide a device and an autofocus control method used therefor.

  Another object of the present invention is to provide a portable electronic device capable of reducing the temperature rise of the housing and an autofocus control method used therefor.

  According to one aspect of the present invention, a portable electronic device includes an imaging unit having an automatic focus adjustment mechanism, and the automatic focus adjustment mechanism includes a lens and a biasing unit that biases the lens in a predetermined direction. Drive means for driving the lens to the in-focus position against the bias, and acceleration detecting means for detecting acceleration applied to the portable electronic device, and control means for controlling the focus adjustment of the imaging means And the control means executes control of automatic focus adjustment when the detection level of the acceleration detection means is within a predetermined range after the activation of the imaging means, and the detection level is outside the predetermined range. In this case, the driving means is stopped.

  Preferably, the control means sets the control value for the automatic focus adjustment mechanism set for the automatic focus adjustment in response to the detection level of the acceleration detection means being outside a predetermined range after performing the automatic focus adjustment. Once invalidated, the control for automatic focus adjustment is resumed in response to a change in the detection level of the acceleration detection means.

  Preferably, the state where the driving unit is stopped is a state where the lens is positioned at one end of the movable range of the automatic focus adjustment mechanism by the biasing unit.

  According to another aspect of the present invention, there is provided an autofocus control method for an image pickup apparatus having an autofocus adjustment mechanism, wherein the autofocus adjustment mechanism includes a lens, a biasing unit that biases the lens in a predetermined direction, Driving means for driving the lens to the in-focus position against the force, the step of detecting the acceleration by the acceleration detection means, and the detection level of the acceleration detection means within a predetermined range after the start of the imaging device In some cases, the method includes a step of executing control of automatic focus adjustment and a step of stopping the driving means when the detection level is out of a predetermined range.

  According to the portable electronic device of the present invention and the autofocus control method used therefor, the power consumption can be reduced by stopping the lens driving mechanism when it is determined that the photographing operation is not performed while the photographing apparatus is being activated. Can be reduced.

  In addition, according to the portable electronic device and the autofocus control method used therefor according to the present invention, it is possible to reduce the temperature rise of the housing by reducing the power consumption of the automatic focus adjustment mechanism.

It is a block diagram for demonstrating the structure of the mobile telephone 100 which concerns on embodiment. 6 is a diagram illustrating a relationship between a control current value from a motor driver 60 and a lens extension amount in the camera sensor 50. FIG. It is a figure which shows an example of the camera operation state detection by the acceleration sensor. It is a flowchart for demonstrating the autofocus control method of this Embodiment.

  Hereinafter, “camera autofocus control” according to an embodiment of the present invention will be described using a mobile phone equipped with a camera as an example. However, such “camera autofocus control” is more generally not limited to a mobile phone, but is a camera mounted on a battery-powered portable electronic device such as a more general portable information communication terminal. It can be applied to autofocus control.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a mobile phone equipped with camera autofocus control according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram for explaining a configuration of a mobile phone 100 according to an embodiment.

  Referring to FIG. 1, a mobile phone 100 performs an antenna 10, a communication unit 20 for transmitting and receiving communication data via the antenna 10, and general control of the mobile phone 100, for example, a communication operation of the mobile phone. A host CPU 30 that executes control and control of photographing processing according to an instruction from a user input to an input device (not shown).

  The mobile phone 100 further includes an acceleration sensor 40 for detecting an acceleration that changes according to the operation state of the operator with respect to the mobile phone 100, a camera sensor (including a VCM drive driver mechanism) 50 for executing photographing, and a host. An image sensor processor (ISP) 70 that controls the focus operation and shutter operation of the camera sensor 50 according to the control from the CPU 30, and a VCM drive driver mechanism according to the control from the image sensor processor 70 And a motor driver 60 that generates a control current. The image sensor processor (ISP) 70 may be a digital sensor processor (DSP).

  FIG. 2 is a diagram showing the relationship between the control current value from the motor driver 60 and the lens extension amount in the camera sensor 50.

  Referring to FIG. 2, when the camera is activated as an initial operation, the motor driver 60 extends the lens to a certain value and maintains a state separated from the image sensor (for example, a CMOS sensor) under the control of the image sensor processor 70. (INF position). In this state, a constant current is passed to control the VCM drive mechanism.

  However, as described later, according to the situation, the motor driver 60 moves the lens position to a state where the VCM drive is almost stopped (mechanical end) with the drive current as the minimum set value under the control of the image sensor processor 70. It shall be. By doing in this way, the electric current in a VCM drive mechanism can be suppressed to the minimum, and low power consumption can be achieved.

  Here, the “mechanical end” means that in the VCM drive mechanism, the lens unit and the housing are connected by an urging mechanism, for example, an urging spring, and the lens unit is attached to the image sensor by the urging force of the urging spring. In the configuration in which the lens unit is biased in the approaching direction, the lens unit can be driven by the biasing spring, and the lens unit is stopped when the VCM driving is stopped. It is assumed that the lens portion is closest to the element.

FIG. 3 is a diagram illustrating an example of camera operation state detection by the acceleration sensor 40.
As shown in FIG. 3, the threshold value is set in advance to the detection level of the acceleration sensor, and is classified into three states (state A, state B, and state C).

  As will be described below, out of the three classifications, the state B in which the acceleration is an intermediate value is determined to be a state in which the camera is used. Further, it is determined that the state A and the state C are a state where the camera is not used, a state where photographing is not performed or a state where photographing is hindered, and the VCM driving current is set to the minimum setting value described with reference to FIG.

Hereinafter, each of the three states will be described.
(State A)
If the acceleration sensor 40 determines that there is a movement within a certain level or less, the host CPU 30 detects that the camera is not used but not used. The host CPU 30 determines that this state is “a state where no image is being taken” with the camera left or deliberately turned on. In state A, a minimum threshold value determined to be unused at the acceleration sensor response level is set and within the range.

(State B)
When the acceleration sensor 40 determines that there is movement within a certain level range (a level exceeding the state A and lower than a predetermined value), the host CPU 30 uses the camera. It is detected that it is in use or is in use. Since the host CPU 30 can assume a certain movement in normal shooting, this state is determined as “a state used for shooting”. The state B is within the range of the minimum threshold value determined as unused at the acceleration sensor response level and the maximum threshold value determined as malfunction.

(State C)
When the acceleration sensor 40 determines that there is a movement within a certain level or higher, the host CPU 30 detects that the camera is not in use but malfunctions. For example, the host CPU 30 may be in a state where the user forgets to turn off the camera and the user is walking, or while the camera is being moved to the shooting position while the power is on. It is determined that it is not in progress. In the state C, a maximum threshold value for determining a malfunction in the acceleration sensor response level is set and within the range.

  FIG. 4 is a flowchart for explaining the autofocus control method of the present embodiment.

  First, when the host CPU 30 activates the camera by an instruction input from the user (S100), the host CPU 30 activates the acceleration sensor 40 (S102).

  Thereafter, the host CPU 30 controls the image sensor processor 70 to set the initial value of the control current of the motor driver 60 in order to set the AF state to the state where the lens position is moved to a certain position. The host CPU 30 detects the camera operation state by the acceleration sensor 40 (S106).

  When the host CPU 30 detects the state B (S106), the host CPU 30 executes an AF operation for photographing, controls the image sensor processor 70, drives the VCM, and sets the motor driver 60 so that the focus position is reached. A control current is set (S108).

  On the other hand, when the host CPU 30 detects the state A or the state C (S106), the host CPU 30 monitors the elapse of a predetermined time with the counter timer (S110), and when the operation state does not change even after the predetermined time (S112). NO), the VCM drive is stopped (changed to the minimum set value) (S114).

  Thereafter, when the detection of the camera operation transitions to the state B (YES in S112), the host CPU 30 determines that it is in use and controls the image sensor processor 70 to change the VCM driving by the motor driver 60 to the initial setting value. (S116). Control then returns to step S106. As a result, while the host CPU 30 determines that the state is B in step S106, the processing loops in step S106 and step S108, and the same control as the VCM driving for focusing is performed. As a result, the low power consumption control is not performed during the processing period of this loop. In other words, after performing the automatic focus adjustment, the host CPU 30 determines that the state is the state A or the state C based on the detection level of the acceleration sensor 40, and thereby the VCM driving mechanism set for the automatic focus adjustment. The control value is once invalidated, and the control for automatic focus adjustment is resumed in response to being determined to be in the state B based on the detection level of the acceleration sensor 40.

  On the other hand, when the host CPU 30 determines that the state is the state A or the state C in step S106, the VCM driving is stopped, so that the power consumption is reduced accordingly.

  Note that in the case of shooting with the camera, when the user performs shooting using the timer setting, it is assumed that the camera is shot with a tripod or the like fixed. Even if it is determined, the process may be shifted to step S108 without shifting to step S110. In addition, as shown in FIG. 4, the control mode for stopping the VCM drive according to the determination in step S106 and the VCM drive is always the initial state after starting the camera regardless of the state detection as in the prior art. A control mode that moves between the set value and the set value at the in-focus position may be switched by a user setting.

  While the camera function is becoming a standard function in portable electronic devices, particularly mobile phones, the proportion of camera operation is still high in terms of power consumption as the functionality increases. Therefore, if the autofocus control method according to the present embodiment is adopted, the reduction in power consumption leads to a longer continuous usable time and a reduction in battery capacity, that is, a thinner casing.

  Furthermore, when the autofocus control method of the present embodiment is employed, it is effective for lowering the heat when the camera drive mechanism is viewed as a heat source.

  In addition, this embodiment can be realized with an AF function camera equipped with an acceleration sensor. If it is assumed that the acceleration sensor is installed for other purposes, the power consumption can be reduced with a simple system. Can be reduced.

  In addition to the lens position by the AF function, it is possible to further reduce power consumption by stopping unnecessary internal clocks and setting the variable frame rate during movie shooting to the minimum value according to the state detection. Become.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10 antenna, 20 communication unit, 30 host CPU, 40 acceleration sensor, 50 camera sensor, 60 motor driver, 70 image sensor processor, 100 mobile phone.

Claims (4)

A portable electronic device,
An imaging means having an automatic focus adjustment mechanism;
The automatic focus adjustment mechanism includes a lens, a biasing unit that biases the lens in a predetermined direction, and a driving unit that drives the lens to a focusing position against the biasing,
Acceleration detecting means for detecting acceleration applied to the portable electronic device;
Control means for controlling the focus adjustment of the imaging means,
The control means includes
When the detection level of the acceleration detection unit is within a predetermined range after activation of the imaging unit, control of automatic focus adjustment is executed, and when the detection level is outside the predetermined range, A portable electronic device that stops the driving means.   The control means controls the automatic focus adjustment mechanism set for the automatic focus adjustment in response to the detection level of the acceleration detection means being out of the predetermined range after performing the automatic focus adjustment. The portable electronic device according to claim 1, wherein the value is temporarily invalidated, and the control for the automatic focus adjustment is resumed in response to a change in a detection level of the acceleration detection unit.   3. The portable electronic device according to claim 1, wherein the state in which the driving unit is stopped is a state in which the lens is positioned at one end of a movable range of the automatic focus adjustment mechanism by the biasing unit. An autofocus control method for an imaging apparatus having an automatic focus adjustment mechanism,
The automatic focus adjustment mechanism includes a lens, a biasing unit that biases the lens in a predetermined direction, and a driving unit that drives the lens to a focusing position against the biasing,
Detecting the acceleration by the acceleration detecting means;
After the start-up of the imaging device, when the detection level of the acceleration detection means is within a predetermined range;
And a step of stopping the driving means when the detection level is outside the predetermined range.

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