  New, high-resolution CMOS image sensors for mobile phones have moved beyond
the single-binnable Quad Bayer and RGBW-Kodak patterns to the double binnable
Hexadeca Bayer pattern featuring 4x4 tiles of like-colored pixels. Pixel
binning enables high-speed, low-power readout in low-resolution modes and, more
importantly, a reduction of read noise via floating diffusion binning.
  In this paper, we present the non-intuitive result that Nona and Hexadeca
Bayer can be superior to Quad Bayer in demosaicking quality due to degeneracies
in the latter's spectrum. However, Hexadeca Bayer suffers from the weakness of
generating Quad Bayer after on round of binning.
  We introduce novel double binnable RGBW and LMS CFAs, composed of 2x2 tiles
capable of 4:1 floating diffusion binning, that are free from spectral
degeneracies and thus demosaic well in full resolution and both binned modes.
RGBW offers a 6 dB low-light, read noise-limited, SNR advantage over Quad and
Hexadeca Bayer in all resolution modes, while for LMS, the corresponding
advantage is 4.2 dB.
