Optical Flow: Method to estimate a very small displacement As I was searching for available resources( here, here, here and many more), I realize that many developed optical algorithm is to estimates LARGE displacement. However, there is very limited information or journals that put effort on estimate very small displacement. The small displacement I'm taking here is at sub-pixel level. The smaller the resolution the better.

So my question, you guys have any idea in mind that might inspire a new method, or suggest an existed method (that I might not be aware of/that can be improved)? Any method/suggestion/comment is very welcomed!
I was confronted to the same problem and I can recommend to use particle filtering. The idea is that instead of using a discretization of the space (which would favor only a limited range of motion detection), the optic flow is computed as a probability density function which is represented by a limited number of samples. These samples (or particles) are precise up to the precision of your computer and can thus detect very small displacments.

Some resources:


the original paper that led to this idea of applying the particle filter method to computer vision: http://www.robots.ox.ac.uk/~misard/condensation.html
a first implementation with details on the method: http://invibe.net/LaurentPerrinet/Publications/Perrinet12pred
a recent implementation : https://github.com/laurentperrinet/Khoei_2017_PLoSCB