actually i was working on ir sensors...so i am thinking of modulating the ir signal so that the ambient light,flash light can be neglected for the purpose of being used in a micromouse....
firstly i use a bandpass filter 20khz .and then a peak detector circuit.
i am actually confused in the peak detector circuit...please drop in ur ideas to elaborate this concept

 

check this out

http://www.allaboutcircuits.com/vol_3/chpt_3/5.html

basically, it turns your sinewave into a dc value that you can threshold.

Steve