  The discovery of multiply-imaged gravitationally lensed QSOs is fundamental
to many astronomical and cosmological studies. However, these objects are rare
and challenging to discover due to requirements of high-angular resolution
astrometric, multiwavelength photometric and spectroscopic data. This has
limited the number of known systems to a few hundred objects. We aim to reduce
the constraints on angular resolution and discover multiply-imaged QSO
candidates by using new candidate selection principles based on unresolved
photometric time-series and ground-based images from public surveys. We
selected candidates for multiply-imaged QSOs based on low levels of entropy
computed from Catalina unresolved photometric time-series or Euclidean
similarity to known lenses in a space defined by the wavelet power spectra of
Pan-STARSS DR2 or DECaLS DR7 images, combined with multiple {\it Gaia} DR2
sources or large astrometric errors and supervised and unsupervised learning
methods. We then confirmed spectroscopically some candidates with the Palomar
Hale, Keck-I, and ESO/NTT telescopes. Here we report the discovery and
confirmation of seven doubly-imaged QSOs and one likely double quasar. This
demonstrates the potential of combining space-astrometry, even if unresolved,
with low spatial-resolution photometric time-series and/or low-spatial
resolution multi-band imaging to discover multiply-imaged lensed QSOs.
