Filtering signal from encoder

Hi, (again xD)
My last problem in a project is a encoder.
The encoder signal is quite bad.(but encoder it seems to me is made good (mechanically))
Chart:http://www.sdilej.eu/pics/aae22f70161d07cb0d8e165e0137f44d.png

Chart undulates I cannot use <80 is matt pad and >80 is shiny pad.

but also oscillates so the method: "If is difference between values >30 is it a transition to another pad" - It is useless

I'm looking for something about the Kalman filter but in my language is not much and it is written at university level (after all, it's university subject) and in English? I opened Wikipedia and I did not know what is the word and what is the term xD

If someone could help with application or have any other idea how to get from this signal a binary signal.I would be grateful

Sorry for english

I think your asking for a comparator, such as a LM393

which is a dual comparator in a single package, basically you give it a reference voltage anything above that is logic high, anything below that is logic low (and works well for optical based encoders where there is a lot of "gray" areas in the output)