I shall first remind the basic properties of gravitational lens systems and how these can be used to derive interesting astrophysical and cosmological parameters. I shall specially address the case of symmetric gravitational lens systems for which such parameters can be derived irrespective of the assumed lens model.

I shall then describe the 4m International Liquid Mirror Telescope project and explain how this telescope, to be be soon erected on the ARIES site in Devasthal (Uttarakhand), will be used to detect and monitor approximately 50 cases of multiply imaged quasars.