|Frame-to-frame feature correlation|
The correlation-based mice rely heavily on the processing power and, at given power, are more limited in speed and resolution. The more modern mice are based on the laser speckle patterns, according to EDN article:
|Surface irregularities (left) and the speckle produced (right)|
"In order to analyze such a speckle, a different type of optical sensor is used which has a unique configuration of the photodiode arrays. This configuration is primarily aimed at producing a minimal number of output signals, in contrast to the large number of pixels used in image correlation technique. The reduced number of output signals reduces the processing requirements of the DSP, hence reducing the power consumption and system cost."