Mobile Focus Principle

Introduction to contrast focus, phase focus and triangulation focus principle and difference

Contrast focus: Use the algorithm to identify the contrast of the screen and confirm the focus success when the contrast is highest. As the focus lens begins to move, the screen becomes clearer and the contrast begins to rise; when the screen is clearest and the contrast is highest, it is already in the charred state, but the camera does not know, so it will continue to move the lens when it finds that the contrast is beginning to drop. Further moving the lens, it is found that the contrast drops further, the camera knows that the focus has been missed, and the lens is rolled back to the highest contrast position to complete the focus.

The phase detection focus has an exclusive focus sensor and a separation mirror (two lens), which forms two lens peaks on the sensor and determines if the focus is based on the spacing of two peaks. It is also possible to calculate the distance of the focus distance from the current focus according to the crest position, so you can direct the lens "one step" to complete the focus. Therefore, it has the characteristics of fast speed.

There is a "pull the bellows" process during the focusing process, so the speed of the contrast focusing system is generally less than that of the phase detection focusing system. But since the input of the contrast focusing system is the data of the main sensor, it is often more accurate than the phase focusing system and supports the focus at any point. At the same time, due to the contrast focus system does not need to add additional hardware, so the cost is low. With the improvement of processor performance and the progress of algorithms, today's contrast focusing system has been able to match the phase focus system at a single focus speed.

Triangulation Focus: Requires a dual camera, according to the target scene relative to the two camera different angle, in the use of the two camera distance between the parameters, the final can quickly measured the target object relative to the camera distance, and then through the Camera module motor for accurate adjustment to complete the fast focus.

In a sense, the focus of triangulation is the external implementation of phase focus (the separation of lens and sensors using dual cameras instead of phase focus), which is expensive and slow to achieve relative phase focusing. Of course, if it is possible to exist as a byproduct.

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Mobile Focus Principle