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Apple's 3D Face ID Tech

1. Overview

Apple use Face ID as an unlocking method first in iPhone X, it use a bunch of technology to improve its performance.

  • Front facing depth-camera
  • infrared camera
  • Deep learning

I was so interested in this tech especially how can Apple apply deep learning with little data and limited compute resource in mobile phone.

2. How it Works?

Apple release a whitepaper about Face ID, so we can learn something from it.

The whole security system is called TrueDepth camera system

  • map the geometry of your face
  • confirms attention by detecting the direction of your gaze

As for users, they need to do something similar to Touch ID:

  1. Register users’ face
  2. Look at the phone
  3. slowly rotate the head
  4. DONE!

As we can see, the process is pretty simple and quick.


The problem here for normal classification procedure are

  • The raw data is limited
  • Computing resource is limited
  • Lack of negative samples

So I think Apple use another method to solve this problem

3. Possible Way

Above all, I think extracting features on faces is the very first thing to do. In this way, device can get a small vector rather than a huge image to train some classification or neural networks in a short time

siamese-like convolutional neural network might be a good way to do the job

Two network share the weights

The main purpose of this work is to value the similarity of two input

So Apple can

  1. pre-train such a model that can detect different feature in users’ face
  2. Get users’ face when they register Face ID and set it as input 1
  3. When users need to unlock their devices or use Face ID to purchase something, the camera get a image as input 2
  4. Calculate the similarity between input 1 and input 2

4. Ref

Towards Data Science Blog

Face ID White Paper