  This article presents a detector system consisting of three components, a
CMOS imaging array, a gaseous-detector structure with a Micromegas layout and a
UV-photon sensitive CsI reflective photocathode. All three elements have been
monolithically integrated using simple post-processing steps. The Micromegas
structure and the CMOS imaging chip are not impacted by the CsI deposition. The
detector operated reliably in He/isobutane mixtures and attained charge gains
with single photons up to a level of 6 \cdot 10^4. The Timepix CMOS array
permitted high resolution imaging of single UV-photons. The system has an MTF50
of 0.4 lp/pixel which corresponds to app. 7 lp/mm.
