Autofocus: Phase Detection (2010)

chrisBob · on Sept 17, 2014

I understand how that works given a lens (or pair of lenses) and a long standoff, but I have not found any information on doing this at the focal plane in the way that Canon does with the AF pixels, and that new phones do (ie iPhone 6).

Does anyone know where you can find information on a phase detection pixel?

personZ · on Sept 17, 2014

http://www.dpreview.com/articles/2151234617/fujifilmpd

That was the first on-plane phase detection, and it is the technique used by the iPhone 6 and GS5.

chrisBob · on Sept 17, 2014

Thanks. I think I can probably get a talk out of that at an upcoming lab group meeting now.

personZ · on Sept 17, 2014

In contrast - http://graphics.stanford.edu/courses/cs178/applets/autofocus...

This is of relevance given the phase detection offered on the iPhone 6 (and previously released on the Galaxy S5).

chrisBob · on Sept 17, 2014

This is for contrast detection which is used by older/cheaper detectors, and specifically not in the iPhone 6, Galaxy S5. Contrast detection is why my iPad (4th generation) can be seen to visibly scan through its whole focus range before fixing focus on the part I want in focus. The whole idea of phase detection is that this is not necessary with the correct hardware.

personZ · on Sept 17, 2014

Indeed, the submission itself is phase detection. That comment was the contrast detection for, humorously, contrast.

Though the iPhone 6 and other devices still feature contrast detection (which is generally a function of the image processor) in addition to phase detection. They each have strengths and applications.