Length Standards Research
Length Standards research is aimed at improving our realization of the metre, improving our current measurement abilities, and extending those abilities into new areas, with new techniques.
The iodine stabilized helium neon lasers that define the metre in NZ are very accurate, stable frequency sources, but only have a few micro Watts power output. This is insufficient to use them directly as sources for interferometric measurement. Laser diodes are capable of much higher output but in most cases are inherently less stable. We are currently working on stabilizing laser diodes at 633 nm on to iodine absorption lines, to provide compact, higher power, accurate and stable frequency sources.
Our current measurement capability is limited to distances less than four metres although we can measure tapes longer than this in sections. We are currently designing a system to operate in a 60 metre long underground tunnel, for calibrating electronic long distance measuring equipment, such as that used by surveyors. We are likely to use a robotic trolley, tracking a laser beam down the length of the tunnel to compare the accuracy of one measurement system against another over 60 meters.