mmorales

Unfortunately neither of these teardowns understand that while TrueDepth and LiDAR both use infrared laser spots, they are fundamentally different technology. 

TrueDepth throws a fine grid of laser points (randomized pattern for security), then looks at where the dots appear to be using parallax. This works great at close range but the accuracy falls dramatically with distance. So perfect for mapping a face but even at 1.5 meters (5 feet) the accuracy has really degraded. This makes it work poorly for AR.

LiDAR actually chops (modulates) the intensity of each laser beam and measures how long it takes for the light echo to return. Super cool, and very hard. This gives great distance accuracy (millimeters), but is hard so you don’t have nearly as many spots. Its accuracy does not meaningfully degrade with distance, though eventually the echo becomes faint enough off of dark surfaces that it can’t measure any more (5 meters or 15 feet for this sensor). 

So they are different sensors for different uses. One is appropriate for FaceID, while the other is appropriate for AR.