  Laue lenses are an emerging technology based on diffraction in crystals that
allows the concentration of soft gamma rays. This kind of optics that works in
the 100 keV - 1.5 MeV band can be used to realize an high-sensitivity and
high-angular resolution telescope (in a narrow field of view). This paper
reviews the recent progresses that have been done in the development of
efficient crystals, in the design study and in the modelisation of the answer
of Laue lenses. Through the example of a new concept of 20 m focal length lens
focusing in the 100 keV - 600 keV band, the performance of a telescope based on
a Laue lens is presented. This lens uses the most efficient mosaic crystals in
each sub-energy range in order to yield the maximum reflectivity. Imaging
capabilities are investigated and shows promising results.
