Patent-free Interest Point Detector? Possible Duplicate:
  Free alternatives to SIFT/SURF for commercial use  




There are same very good algorithms for interest point detection/description, like:


SIFT (Scale-Invariant Feature Transform)
SURF (Speeded-Up Robust Features)
MOPs (Multi-Scale Oriented Patches)


Regrettably, at least the first two are patented and cannot be used commercially without paying huge fees to the authors. I am currently negotiating about the third one, which is patented as well.

In a search for patent-free algorithm, I found there is a multitude of patents like this one. Huh?! Is there merely anything usable then?

Maybe at least Harris-Laplace or some basic detector can be used. But how to be sure?
(IANAL...)

If you only want detectors:


Harris is probably OK.
According to http://users.fmrib.ox.ac.uk/~steve/susan/, SUSAN is out of patent now.
I've not seen any claims that FAST is patented.


Descriptors are harder... 

Histograms of Oriented Gradients might be worth considering - again I've not seen any claims of patent on the original form.