  Longtime monitoring of gravitational lens systems is often done using
telescopes and recording equipment with modest resolution. Still, it would be
interesting to get as much information as possible from the measured
lightcurves. From high resolution images we know that the recorded quasar
images are often blends and that the corresponding time series are not pure
shifted replicas of the source variability. In this paper we will develop an
algorithm to unscramble this kind of blended data.
  The proposed method is based on a simple idea. We use one of the photometric
curves, which is supposedly a simple shifted replica of the source curve, to
build different artificial combined curves. Then we compare these artificial
curves with the blended curves. Proper solutions for a full set of time delays
are then obtained by varying free input parameters and estimating statistical
distances between the artificial and blended curves.
  We performed a check of feasibility and applicability of the new algorithm.
For numerically generated data sets the time delay systems were recovered for a
wide range of setups. Application of the new algorithm to the classical double
quasar QSO 0957+561 A,B lightcurves shows a clear splitting of one of the
images. This is an unexpected result and extremely interesting, especially in
the context of the recent controversy about the exact time delay value for the
system.
  The proposed method allows us to properly analyse the data from low
resolution observations that have long time coverages. There are a number of
gravitational lens monitoring programmes that can make use of the new
algorithm.
