1. Field of Invention
The present invention relates to an adaptive de-flicker device and a method for adaptive de-flicker.
2. Description of Related Art
When ambient light comes from an indoor light source instead of a natural light source, a 50 Hz or 60 Hz flicker is generated according to the frequency of a power supply. To capture images by an image capture device (e.g., an image sensor) under such circumstance, it usually requires de-flickering to avoid inconsistency among brightness of the pictures. In general, de-flickering is processed by way of adjusting exposure time, wherein the exposure time is set to an integer multiple of 1/100 second when the frequency of the power supply is 50 Hz, and is set to an integer multiple of 1/120 second when the frequency of the power supply is 60 Hz. To determine the frequency of the ambient light wherein the image capture device is operated, the prior art provides two ways: The first way is to determine the 50 Hz or 60 Hz frequency by the geographical location where an apparatus using the image capture device (e.g., digital camera, digital video recorder, or monitor) is sold. The problem of this approach is that, for certain types of machines such as a digital video recorder, a user may use it in different geographical regions because of traveling. The other way is presently only applicable to a monitor system, wherein a power frequency sensor and a switch circuit is provided in addition to the monitor. The power frequency sensor determines whether the frequency of the power supply is 50 Hz or 60 Hz, and switches the monitor system to a corresponding frequency that is suitable for de-flicker. This approach is subject to a condition that the monitor system has to be placed in a fixed location, and supplied by a local power supply. However, if the machine is supplied by its own battery instead of the local power supply, such as a portable machine (e.g., a digital video recorder), it is not possible to obtain the frequency of the local power supply and to de-flicker accordingly.
In view of the foregoing, the present invention provides an adaptive de-flicker device and a method related thereto.
A first objective of the present invention is to provide an adaptive de-flicker device, which can be applied to, for example but not limited to, a system related to capturing images.
Another objective of the present invention is to provide a method for adaptive de-flicker.
To achieve the foregoing objectives, in one perspective of the present invention, it provides an adaptive de-flicker device comprising: a light sensor for sensing ambient light and generating a corresponding electric signal; and a signal processor coupled to the light sensor, for obtaining a flicker frequency of the ambient light according to the electric signal generated by the light sensor.
In one preferable embodiment, the signal processor includes an amplifier amplifying the electric signal generated by the light sensor. The signal processor may further include a filter filtering the amplified electric signal and/or an analog to digital converter performing analog to digital conversion on the amplified electric signal.
In another preferable embodiment, the adaptive de-flicker device further comprises a clock generator coupled to the signal processor, for generating a clock related to the flicker frequency of the ambient light according to an output signal of the signal processor. The clock generator preferably further includes a delay lock loop (DLL) generating a signal with a stable frequency according to a frequency of the output signal of the signal processor. The clock generator further includes a frequency-division circuit coupled to the DLL for performing frequency-division on the signal generated by the DLL.
In another perspective of the present invention, it provides a method for adaptive de-flicker, comprising: sensing ambient light and generating a corresponding electric signal; obtaining a flicker frequency of the ambient light according to a frequency of the electric signal; and de-flickering an image captured by an image capture device according to the flicker frequency of the ambient light.
In one preferable embodiment, the step of obtaining a flicker frequency of the ambient light includes: filtering the electric signal.
The step of obtaining a flicker frequency of the ambient light may further include: amplifying the electric signal before filtering it, and performing analog to digital conversion on the electric signal.
In one embodiment, the foregoing method for adaptive de-flicker further comprises: generating a clock related to the flicker frequency of the ambient light. The step of generating a clock for example includes: sampling the flicker frequency of the ambient light by a sampling frequency, and duplicating the flicker frequency to generate a signal with a stable frequency. In addition, the step of generating a clock may further include: dividing the stable frequency.
The objectives, technical details, features, and effects of the present invention will be better understood with regard to the detailed description of the embodiments below, with reference to the drawings.
Please refer to
The signal processor 20 can be embodied by various ways, and
After the analog signal is converted to the digital signal, it can next be filtered by a filter 26. Or, the analog signal can be filtered by the filter 26 first, and next converted to the digital signal, as shown in
The clock generator 30 can be embodied by various ways, of which one embodiment is shown in
Please refer to
A state machine of the DLL 32 is shown in
Compared with the prior art, the present invention is more advantageous because it can adaptively sense and eliminate the flicker in the ambient light, which is a great benefit to a portable device. In addition, the present invention can support a function for synchronization or line lock among multiple video cameras.
The present invention has been described in considerable detail with reference to certain preferred embodiments thereof. It should be understood that the description is for illustrative purpose, not for limiting the scope of the present invention. Those skilled in this art can readily conceive variations and modifications within the spirit of the present invention. For example, any function performed by a single hardware circuit in the drawing can be performed by multiple hardware circuits or software instead. As another example, in the embodiment shown in
Number | Date | Country | Kind |
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098116462 | May 2009 | TW | national |