December 19, 2025
Laser eyes, hot takes
Designing a Passive Lidar Detector Device
Your phone beams invisible dots; fans cheer, skeptics roll eyes
TLDR: A clever demo shows you can spot an iPhone Pro’s depth sensor turning on when the camera opens. Commenters split between privacy alarm and tech nitpicking, with many saying it only targets Apple’s specific infrared pattern, making it a cool side-channel but not a universal spy tool.
Phones are quietly shooting invisible laser dot grids and the internet is losing it. Inspired by Samy Kamkar’s DEF CON talk, a tinkerer set out to spot the iPhone Pro’s TrueDepth system lighting up when the Camera app opens, before any photo is taken. The gist: Apple’s depth sensor uses a tiny laser (VCSEL) and a super-sensitive detector (SPAD), pulsing at specific rhythms. You can see more in the creator’s write-ups at Medium and LiDAR News.
Cue the drama: the privacy posse freaked out about “detecting phones in the wild,” while the spec pedants rolled in to nitpick frequencies and wavelengths. MezzoDelCammin dropped the biggest reality check, saying this is basically detecting Apple’s specific 940nm/60Hz setup, not LiDAR in general. Others joked this is “pre-snap paparazzi radar,” and Android fans chimed in that Pixels also ping infrared for pocket detection. Meme-makers dubbed it “Apple’s laser mood ring” and threatened to show up with tin-foil case couture. Nostalgia also hit hard, with folks reminiscing about DIY laser mics on windows. Verdict from the crowd: clever side-channel and fun demo, but split between useful party trick and mini surveillance scare—and yes, the pedants brought receipts
Key Points
- •iPhone TrueDepth/Face ID LiDAR uses a 60 Hz VCSEL emitter and a 15 Hz SPAD sensing rate with a duty cycle envelope.
- •The LiDAR activates when an application uses it, including the default camera app at startup, enabling detection before a photo is taken.
- •The emission optics include 16 stacks of 4 VCSEL cells (64 total), expanded by a 3×3 DOE to 576 pulses; optimal range is 0.30–2.00 m.
- •LiDAR depth map sampling is 15 Hz despite a 60 Hz RGB camera framerate, limiting certain measurement applications.
- •Similar passive detection concepts can identify iPhone lock screen states and detect Pixel 5+ devices via infrared pocket detection; experiments used IR receivers and photodiodes.