Explanation:
The process of focusing is to make the image of the focusing area the clearest by moving the lens.
There are two kinds of focusing methods commonly used in mobile devices:
Contrast focus:
1. First of all, please understand a concept that the best definition of the image is when the contrast is the largest and the aberration is the smallest. The contrast focus is to find the point with the largest contrast in the focus area as the focus accurate point, and the phase focus is to find the point with the smallest difference in the focus area as the focus accurate point.
2. On the other hand, contrast focus and phase focus are only part of the focusing system and are only used to find the best position of the lens in the focusing process. How the lens is moved is not within the scope of this problem.
3. Contrast focus is by looking for the point with the highest contrast in the focus area as the accurate point of focus. However, the contrast size of different focus areas is not fixed, and the system does not know when the contrast is the largest, so it is necessary to move the lens back to find it.
Phase focus:
1. The phase focus determines the imaging difference by additional devices or special pixel points, then it is easy to know how the lens should move and how far it should be moved, so don't have to blindly go back to move the lens when focusing.
2. Through the above understanding, it can be known that the difference between the two focusing methods. In short, the phase focus is fast and the contrast focus is slow, but the realization of phase focusing requires additional phase detection device or pixel redesign of sensor. The requirement for light is relatively high. The contrast focus is simple, which is done through the algorithm to judge the contrast, and the requirement for light is not so high.
At present, as long as the phase focus is used, the contrast focus will be retained to supplement it, so it is called mixed focus.