A 905-nm 5-kHz rep. rate diode-laser biaxial lidar ceilometer (cloud-height monitoring) prototype is presented. The
prototype uses a low-cost Fresnel lens and a low-NEP avalanche photodiode (APD) opto-electronic receiver. The article
presents the opto-mechanical engineering of both the system and main subsystems involved as well as the system energy
The reception subsystem is based on a low-cost Fresnel-lens telescope and collimating and focusing adjustable parts,
which include a rectangular slit diaphragm to minimise background radiance. Equivalent focal length, background
radiance rejection gain, confusion circle and imaged spot characteristics onto the photodiode surface are also formulated
and discussed by means of a geometrical optics approach.
The emission subsystem uses a beam expander to ensure eye-safety (maximum exposure levels) and ad-hoc mechanics
to provide enough degrees of freedom for emission-reception overlap factor (OVF) adjustment. At this point, an
overview of future alternative mechanical solutions for enhanced pointing accuracy and trade-offs among different laser
diode-based solutions is presented. This part is complemented with OVF simulations of the prototype designed.
Finally, preliminary test measurements at our premises in North Campus (UPC) are introduced as raw and rangecorrected