The CAFADIS camera is a new sensor patented by Universidad de La Laguna (Canary Islands, Spain): international
patent PCT/ES2007/000046 (WIPO publication number WO/2007/082975). It can measure the wavefront phase and the
distance to the light source at the same time in a real time process. It uses specialized hardware: Graphical Processing
Units (GPUs) and Field Programmable Gates Arrays (FPGAs). These two kinds of electronic hardware present an
architecture capable of handling the sensor output stream in a massively parallel approach. Of course, FPGAs are faster
than GPUs, this is why it is worth it using FPGAs integer arithmetic instead of GPUs floating point arithmetic.
GPUs must not be forgotten, as we have shown in previous papers, they are efficient enough to resolve several problems
for AO in Extremely Large Telescopes (ELTs) in terms of time processing requirements; in addition, the GPUs show a
widening gap in computing speed relative to CPUs. They are much more powerful in order to implement AO simulation
than common software packages running on top of CPUs.
Our paper shows an FPGA implementation of the wavefront phase recovery algorithm using the CAFADIS camera. This
is done in two steps: the estimation of the telescope pupil gradients from the telescope focus image, and then the very
novelty 2D-FFT over the FPGA. Time processing results are compared to our GPU implementation. In fact, what we are
doing is a comparison between the two different arithmetic mentioned above, then we are helping to answer about the
viability of the FPGAs for AO in the ELTs.