How to focus objects in mobile phone camera - I

If you have a DSLR camera, you can adjust the focus by rotating the lens. Even in the auto mode functionality, the adjustment can be seen by the naked eye. Today we are going to find out how the mobile phone camera mechanism takes place to adjust the lens to capture objects. Basically, several technologies can be used to find the focus of a mobile phone camera. Each cell phone uses a different technology. You can see that some mobile phones use two or more technologies.

We can categorize these options into different technologies. Let's see what are the focus types within these three categories separately.

• Passive Auto Focus
• CDAF - Contrast-Detection Auto Focus
• PDAF - Phase-Detection Auto Focus
• Dual Pixel Auto Focus (aka Dual Pixel PDAF)

•  Active Auto Focus - Laser Auto Focus 
  

•  Hybrid Auto Focus - Focus types using two or more of the above mechanisms (Eg: PDAF+Laser AF) 

Let's see, what are Passive Focus and Active Focus.

Passive focus is the process by which a stream of light from an outside object passes through the camera lens and is set to focus on the distance and light intensity of an object by an algorithm provided by the CCD (Charged Coupled Device) on the camera sensor. A part of the camera sensor detects the location and distance of an object and adjusts the lens. For a passive focus to function properly, it must have both the light and the object contrast (Lighting condition and Contrast) relative to other objects. Then it is certain that a Passive Auto Focus does not happen in the dark. So how exactly do you focus in the dark? That's when the Active Focus Mechanism emerges.

Before we talk about Active Focus, we need to talk about Sonar Beam. Ever wondered how the shapes of seabed objects (like sunken ships) know the distance? What happens is that ships or submarines send a sonar beam, which is a very sensitive range of sound, to the seabed. The distance to the object is determined by calculating how long it took for the beam to collide with the object and reflect back. This process has been developed to the extent that the shape of the relevant objects can be identified. Sonar radar systems operate on this principle. This is very easy to understand if you understand how an ultrasonic sensor commonly used in Arduino works.

Off the topic: Dolphins, considered to be the most intelligent species in the world, use this sonar beam to communicate with their species many miles away. Even today, scientists do not know how to do that. Turning to the Activate Focus again, it simply means that the technology works in the same way as the Sonar Beam or Ultrasonic mentioned above. The difference is that it uses a laser beam. The device emits a laser beam and adjusts the focal length by calculating the time it will take to hit the object and recover. That means an Activate Focus works even in a dark place. Having light is not a mandatory factor. Then you will understand by now why Active = Active and Passive = Passive as I said earlier. 

The rest is just one category. Hybrid, or Hybrid Focus Mechanism. This is very simple to say. Using two or more Activate and Passive Focus Mechanisms to adjust the Focus Length is called a Hybrid Focus Mechanism. Easy to say but a very complex process takes place here. We will talk about that in the next section. 

Usually, when we say hybrid, the first thing that comes to mind is a car that runs on both liquid fuel and electricity. But the word hybrid literally means hybrid. This means that any process that combines two types of technologies in any science can be called a hybrid, any process that enhances efficiency and productivity. Hybrid Autofocus Mechanism is one of the hybrid processes that is working in zoology, botany, automotive technology, and camera parts.

In this hybrid category, two Passive focus mechanisms (Mechanism) or two Passive Active mechanisms can be used to find the exact focus.

• Passive + Passive = PDAF + CDAF 
• Passive + Activate = PDAF + Laser AF
  

There are two ways to create a Hybrid Focus. You can usually find a Hybrid Focus Mechanism in the High-End mobile phone with the flagship category or close to it. 

Visit this link to read more > Part II

Cheers!