A Multiprocessor System-on-Chip Implementation of a Laser-based Transparency Meter on an FPGA

Modern FPGAs are large enough to implement multi-processor systems-on-chip (MPSoCs). Commercial FPGA companies also provide system design tools that abstract sufficient low-level system details to allow non-FPGA experts to design these systems for new applications. The application presented herein was designed by photomask researchers to implement a new technique for measuring the transparency of bimetallic grayscale masks using an FPGA platform. Production of the bimetallic grayscale masks requires a direct-write laser system. Previously, system calibration was determined by writing large rectangles of varying transparency on a mask and then measuring them using a spectrometer. The proposed technique uses the same mask-writing system but adds photodiode sensors connected to a multiprocessor computing system implemented on an FPGA. The added sensors combined with the laser beam's smaller focal point allows the calibration rectangles to be up to 5000 times smaller than those required by the spectrometer. This allows for direct mask verification on a mum-sized scale. Furthermore, the MPSoC design on the FPGA is easily scalable to support an increased number of photodiodes for the future addition of a feedback approach to the project.