I'm trying to implement a vision-based "lidar" system as described here: https://hackaday.com/2016/04/04/smartphone-and-ir-line-laser-measure-distance/
the idea is to capture video at 30fps and pulse a laser at 15hz such that the laser appears in odd frames and does not appear in even frames. By taking the difference between odd and even frames we can isolate the laser line.
when I implemented this, the isolated laser phases in and out with a period of ~1 second. Looking at the raw frames, sometimes the laser is full-brightness, sometimes it is not visible, and sometimes it's at 50% brightness.
Given that the laser is either on or off, I'm not sure why the partial-brightness frames occur. My current theory is that CMOS rolling shutter might not just scan top->bottom like I'd expect, but that doesn't make much sense. I checked to make sure that I'm getting video at 30fps and I'm using a usb camera with the ov9712 chip.