We report in this work on a project aimed at determining Lyα luminosity functions from z=3 to z=6. The project is based on the use of very deep photometry from the SHARDS Survey, in a set of 24 medium band filters in the GOODS-N field. We present here some preliminary work carried out with four test images in four consecutive bands. We use the narrow band selection technique for searching emission line candidates. Eleven candidates have been detected so far, many of which are strong Lyα candidates. In particular, we have seen a firm candidate to an interacting pair of Lyα sources at z=5.4.