Research Of Real-time Wavefront Processing Algorithms Based On Multi-core DSP

In an Adaptive Optics system, the Wavefront Processor is the core computingpart. it is responsible for transforming the distorted wave informations to the controlvoltage signals. By using the processing methods such as gradient calculation,wavefront reconstruction and control calculation, it can realize the real-time closedloop control. To ensure the real-time correcting feature, the whole process requireshigh data computing and transmission speed. Currently, in larger diameter telescopesystems, the system scale had to reach thousands of elements, the amount ofwavefront calculation sharply increased. If the given sampling frequency of CCDcamera was relatively stable, the real-time requirements of wavefront processor wouldhave to be very strict.In this paper, we propose a processing method of wavefront reconstruction andcontrol calculation based on multi-core DSP (TMS320C6678). It can implement thecalculation with the scale up to one thousand elements. According to the parallelcharacteristics of wavefront calculation and the data flow relationships among eachcalculation module, we develop a multi-core parallel processing design idea on spaceand time, which significantly reduce the processing latency. By comparing theoperating speed of CPU and the I/O speed of memory, we propose a reasonablememory allocation scheme, which effectively improve the actual computing speed ofmulti-core DSP. To making sure the real-time capabiliy of data transmission, weestablish the SRIO data communication between FPGA and DSP, the Hyperlinkreal-time data transmission between different DSPs. At last, by using the chosenhardware platform, we implemented the wavefront reconstruction and controlcalculation task with a single C6678. The system scale is968sub-apertures and913actuators. According to the experimental result, this method can meet the systemdemand of3000~4000HZ sample frequency and56.4us processing latency. Thewavefront processing method is a good guidance and reference for reducing operatinglatency of thousands of elements wavefront processing, and has very high engineeringvalue.