Patent Application
20120268645
1. Field of the Invention
The present invention relates to portable electronic devices, and in particular relates to auto-focus control methods for the cameras thereof.
2. Description of the Related Art
Camera apparatuses nowadays are generally equipped with auto focus functions.
For portable electronic devices, such as a mobile phone or a PDA having cameras therein, or a camera and so on, the auto-focus accuracy of the camera apparatus therein is dependent on the way a user holds the portable electronic device.
In this auto focus field, improving the auto focus quality of cameras of portable electronic devices is important.
A portable electronic device and an auto focus method for cameras therein are disclosed.
A portable electronic device in accordance with an exemplary embodiment of the invention comprises one lens module, an image sensor, a G-sensor, a storage unit, a central processing unit and a focus module.
There is an image distance between the lens module and the image sensor. The G-sensor detects the orientation of the portable electronic device to generate orientation information. The storage unit stores autofocus look up tables for different orientations of the portable electronic device, respectively. According to the orientation information, the central processing unit selects one of the autofocus look up tables from the storage unit and generates an actuating signal for the focus module based on the selected autofocus look up table. Driven by the actuating signal, the focus module adjusts the image distance.
According to an exemplary embodiment of the invention, an autofocus method for a camera of a portable electronic device is disclosed and comprises the following steps: providing autofocus look up tables for different orientations of a portable electronic device, respectively; detecting the orientation of the portable electronic device to generate orientation information; selecting one of the autofocus look up tables according to the orientation information, and generates an actuating signal for an focus module based on the selected autofocus look up table; and driving the focus module according to the actuating signal to adjust an image distance between a lens module and an image sensor of the camera.
A detailed description is given in the following embodiments with reference to the accompanying drawings.
The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
Referring to
As shown in the embodiment of
It is noted that the orientation of the lens module 102 of the camera 202 changes with the orientation of the portable electronic device 200. That is, gravity should be taken into consideration in focus control. The following discussion is shown in contrast to a case where the lens module 102 faces forward. When the lens module 102 faces upward, a greater magnetic force MF is required to further support the lens module 102 because of gravity. When the lens module 102 faces downward, less magnetic force MF is required because the weight of the lens module 102 pushes outward.
The multiple autofocus look up tables LUT_1, LUT_2 and LUT_3 stored in the storage unit 206 are configured to manage the influence of gravity on the autofocus function. In this embodiment, the autofocus look up tables LUT_1, LUT_2 and LUT_3 relate to different orientations (e.g. 3 different orientations), and, each table provides one mapping table of the actuating signal As to the image distance d_image, as discussed in more detail below.
The first autofocus look up table LUT_1 relates to a case where the lens module 102 faces upward, and shows a mapping table, between the actuating signal As and the image distance d_image. The second autofocus look up table LUT_2 relates to a case where the lens module 102 faces forward, and shows a mapping table, between the actuating signal As and the image distance d_image. The third autofocus look up table LUT_3 relates to a case where the lens module 102 faces downward, and shows a mapping table, between the actuating signal As and the image distance d_image. For consistent control of the image distance d_image—for example, controlling the image distance d_image to be a specific value—the first autofocus look up table LUT_1 outputs a first actuating signal As1 which is greater than a second actuating signal As2 determined by the second autofocus look up table LUT_2, and, the second actuating signal As2 is greater than a third actuating signal As3 determined by the third autofocus table LUT_3. That is, As1>As2>As3. Because of the different actuating signals As1, As2 and As3, the focus controller 214 generates different driving currents (Ivcm) to drive the voice coil 212 to generate different magnetic forces (MF) to appropriately cope with different orientations of the lens module 102.
Note that other embodiments may use more autofocus look up tables if more orientations of the lens module are taken into consideration for autofocus control. The number of the autofocus look up tables is not limited to 3 (as in the case shown in
Furthermore, in other embodiments, the focus module 210 may be implemented by other techniques and is not limited to the voice coil technique shown in
Furthermore, the disclosed portable electronic device may be any portable device having camera functions. For example, a mobile phone or a PDA, or a camera for photography use, a video camera, and so on.
In addition to the disclosed portable electronic devices,
In one embodiment, the focus module may be implemented by a voice coil mechanism. That is, in step S306, a driving current may be generated based on the actuating signal to drive a voice coil to provide a magnetic force to shift the lens module and thereby adjust the image distance.
Note that the steps taken by the disclosed autofocus procedure are not limited for operation of the device of
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
