Certain aspects relate to systems and techniques for using imaging pixels (that is, non-phase detection pixels) for performing noise reduction on phase detection autofocus. Advantageously, this can provide for more accurate phase detection autofocus and also to optimized processor usage for performing phase detection. The phase difference detection pixels are provided to obtain a phase difference detection signal indicating a shift direction (defocus direction) and a shift amount (defocus amount) of image focus, and analysis of imaging pixel values can be used to estimate a level of focus of an in-focus region of interest and to limit the identified phase difference accordingly.