Patel, Rikesh and Achamfuo-Yeboah, Samuel and Light, Roger and Clark, Matt (2012) Ultrastable heterodyne interferometer system using a CMOS modulated light

A novel ultrastable widefield interferometer is presented. This uses a modulated light camera (MLC) to capture and stabilise the interferogram in the widefield heterodyne interferometer. This system eliminates the contribution of piston phase to the interferogram without the need for common path optics and results in a highly stable widefield interferometer. The MLC uses quadrature demodulation circuitry built into each pixel to demodulate the light signal and extract phase information using an electronic reference signal. In contrast to the work previously presented [Opt. Express 19, 24546 (2011)], the reference signal is derived from one of the pixels on board the MLC rather than an external source. This local reference signal tracks the instantaneous modulation frequency detected by the other pixels and eliminates the contribution of piston phase to the interferogram, substantially removing the contributions of unwanted vibrations and microphonics to the interferogram. 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