Yeah, I remember when the first CMOS sensors with phase detection elements started showing up. This is what I meant by "conceptually similar" although I probabl

Yeah, I remember when the first CMOS sensors with phase detection elements started showing up. This is what I meant by "conceptually similar" although I probably should have clarified, since we've had massive sensors without these elements for longer. I guess contrast-based autofocus is what really needs the DSP, since you need to do edge detection / FFTs on more patches of image for the technique to work well, as well as PSF analysis if you want to guess the lens defocus direction. With phase it's just a few cheap 1D correlations, and you get accurate lens direction information for free, which explains why it feels so much faster. Unfortunately we didn't have access to an electron microscope, so a modern mirrorless camera would have made for a rather less interesting teardown.