A while back, while looking at my Sony FDR-AX53 camcorder, I noticed it had a night shot mode. Having owned a Mini DV Sony Camcorder in the past, I knew this meant it could record in infrared. I thought it would be fun to use it to record the Face ID of my 10.5” 2018 iPad Pro unlocking since that also uses infrared (IR).

Fast forward a few months and I was looking for something interesting to post to Instagram late at night when I suddenly remembered the dot pattern caused by the Face ID in IR.

So I turned on Night Shot and I was surprised to see my Pixel 4 XL sitting on the desk blasting IR light into the room. I wasn’t using it at all, but it was steadily shining a continual pulse non-stop from a small emitter in the sensor bar.

I was especially confused because I was under the false impression that the Soli Radar chip in the Pixel 4 was what did the face unlocking and proximity sensing. So I pulled up the phone and unlocked it. After experimenting for a while, I realized I had Android’s Smart Unlock turned on, so the device wasn’t locking due to being connected to my watch. I turned that off and the Screen attention setting that keeps your screen on if the phone thinks you’re looking at it.

I tried unlocking the phone again, but still didn’t see the usual dot projection on my face like I was accustomed with the Apple FaceID so it led me to speculate that an IR emitter and the Soli radar chip were working in conjunction with one another.

I proceeded to make the first part of this video, but when editing (and looking at the footage on a bigger screen) I now saw a second beam of IR light being sent out from the side of the phone that I though the Soli Radar Chip was located.

After some digging on the internet I found a map of all of the sensors in the Pixel 4’s top sensor bar and it finally made sense. The first, less bright light, that is always on, is just a proximity sensor, much like any of the holiday decorations that play music when you walk by. It flashes a light non-stop, screen on or off, constantly checking to see if your hand is near to the screen. This may be able to be turned off with the “Show display when nearby” setting, that wakes the screen when you reach for the phone, thought I didn’t try. ( That’s another feature that I thought was due to the Soli Radar.)

Then when you attempt to unlock the phone, it blasts your face with a similar dot mapping pattern and measures the contours of your face, which is the 2nd, brighter light that you see. It may also use the Face Unlock Flood Illuminator, but it’s too bright in the camera to see which of the 2 are firing. However, what it does NOT use is the Soli Radar Chip, because despite covering that with my finger, I was still able to unlock the phone using just the IR emitters.

This leads me to 2 hypotheses

1. The Soli Radar chip that’s in the phone isn’t nearly as sensitive as most of the public was lead to believe

2. The Soli Radar uses a lot of energy and it’s only used when needed and AFTER the low powered IR proximity sensor recognizes something is nearby. The Soli Radar emits electromagnetic waves and perhaps they use more energy than infrared.

Unfortunately, I don’t have a way to further test this, but it’s interesting to me none the less. I think a lot has gone into making the Soli Radar that’s in this phone seem cooler than it actually is.

Anyway, this was just a fun little video without much purpose meant to just entertain. Hopefully you find the dot projections as neat to look at as I do.