If you've been following rumours about the launch of three new models tomorrow, one of the claims put out is that the new AF system will be very fast, even compared to the already fast Panasonic models and DSLRs. That's a pretty big claim, with the big question of how could they do that? Just do the same but better? Or something really new?
Well, a patent from Olympus as reported by 43rumors
seems to show one way of doing it.
I have not read the patent yet and will do shortly. Going by what's written on the post alone, the key is by adding IR sensing elements into the bayer mix. The IR sensitive elements are suggested will replace some of the green ones at the desired AF points.
How it is claimed to work makes use of the knowledge that for most visible light optical lenses, they focus the IR region at a different plane than visible. By sensing and comparing the IR and green channel focus (still contrast based) they can gain information as to the true focal point relative to where the focus is set.
There is a cost to this, in that you lose some visible light sensors. I wonder if they can calibrate existing lenses to make use of this too? I would suspect for optimal performance, each lens model would need to be profiled to know how they react to visible and IR.
If this works as well as believed, this might be the point at which the last major contrast AF weakness over phase is overcome, at least in some conditions.
Limitations of such a system would be that the IR blocking filter obviously can't be put in front of the sensor any more, otherwise the AF wouldn't work quickly and have to fall back to conventional methods. That means to me they would have to filter the IR out of the RGB detectors at colour filter level? Also the scene would obviously need to contain a degree of IR light for it to work on. No problem outdoors particularly on a sunny day, but indoors might be a challenge there depending on the type of lighting used.