FPGA-accelerated adaptive optics wavefront control part II

Abstract

We present progressive work that is based on our recently developed rapid control prototyping system (RCP), designed for the implementation of high-performance adaptive optical control algorithms using a continuous deformable mirror (DM). The RCP system, presented in 2014, is resorting to a Xilinx Kintex-7 Field Programmable Gate Array (FPGA), placed on a self-developed PCIe card, and installed on a high-performance computer that runs a hard real-time Linux operating system. For this purpose, algorithms for the efficient evaluation of data from a Shack-Hartmann wavefront sensor (SHWFS) on an FPGA have been developed. The corresponding analog input and output cards are designed for exploiting the maximum possible performance while not being constrained to a specific DM and control algorithm due to the RCP approach. In this second part of our contribution, we focus on recent results that we achieved with this novel experimental setup. By presenting results which are far superior to the former ones, we further justify the deployment of the RCP system and its required time and resources. We conducted various experiments for revealing the effective performance, i.e. the maximum manageable complexity in the controller design that may be achieved in realtime without performance losses. A detailed analysis of the hidden latencies is carried out, showing that these latencies have been drastically reduced. In addition, a series of concepts relating the evaluation of the wavefront as well as designing and synthesizing a wavefront are thoroughly investigated with the goal to overcome some of the prevalent limitations. Furthermore, principal results regarding the closed-loop performance of the low-speed dynamics of the integrated heater in a DM concept are illustrated in detail; to be combined with the piezo-electric high-speed actuators in the next step

Implementing a Hybrid Method for Shack–Hartmann Wavefront Spots Labeling on FPGA

“…In ref. [11], a Connected Components Labeling method (CCL) was used to detect the position of the spots, and the calculation of the centroid was carried out after the spot detection. The authors in ref.…”

Transportable system for in-field testing of adaptive optical pre-compensation for optical feeder links

“…Before the actual optical design can be developed, the required beam size at these individual elements needs to be determined. Since the AO control loop is based on the real-time FPGA based system developed in [1,2], the beam diameter at the wavefront sensor is already dictated. Furthermore, the tip/tilt mirror as applied in [2] is incorporated, which predetermines the respective beam size as well.…”

“…Since the AO control loop is based on the real-time FPGA based system developed in [1,2], the beam diameter at the wavefront sensor is already dictated. Furthermore, the tip/tilt mirror as applied in [2] is incorporated, which predetermines the respective beam size as well. The AO system utilizes a unimorph deformable mirror manufactured at Fraunhofer IOF.…”

The Driver’s Design and Implementation of PCIe High Speed Image Acquisition Card Based on WDF

“…The core of the board is Xilinx's Kintex7 series XC7K70T FPGA processor, which uses Xilinx's official PCIe hard core [2] to communicate with the driver. As a bridge between the application and the underlying hardware, the driver is mainly responsible for receiving the control commands from the application program and the image data from the FPGA, selecting the set image type by command, and using DMA to move the data transferred to the FPGA to the upper application according to the size of the image.…”