Digital Phase Meter for a Laser Heterodyne Interferometer

The figure depicts two digital waveforms and a block diagram of a digital phase meter for measuring the difference between their phases. This digital phase meter is being developed for incorporation into a laser heterodyne interferometer in a metrological apparatus, but could also be adapted to other uses. Relative to prior phase meters of similar capability, including digital ones, this digital phase meter is smaller, less complex, and less expensive. The phase meter has been constructed and tested in the form of a field-programmable gate array (FPGA) of fewer than 104 gates.