Like Canon, Nikon has no camera with the Hybrid AF sensor that might its one great cause of falls behind in the race. So the only way to get itself back into the track is either it hire AF sensor from Sony or develop its own sensor. However, the recent Patent filed by Nikon shows that they are working on improving the AF system of the camera. Yes, Nikon is working on PDAF sensor and it looks like we will soon see a camera’s announcement with this feature.
Most pixels are split into several sub-pixels for an accurate phase-detection, but some special pixels have single light-slit with novel arrangement to help phase-detection for a heavily defocused image.
[Publication date] December 7, Heisei 20 (2017.12.7)
Patent application title: Imaging device and electronic camera