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Ultrastable heterodyne interferometer system using a CMOS modulated light camera

Patel, Rikesh; Achamfuo-Yeboah, Samuel; Light, Roger; Clark, Matt


Samuel Achamfuo-Yeboah

Roger Light

Professor of Applied Optics


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. Interferograms taken using the ultrastable system are presented with one of the interferometer mirrors moving at up to 85 mm s?1 over a variety of frequencies from 18 Hz to 20 kHz (giving a variation in optical path length of 220 ?m, or 350 wavelengths at 62 Hz). This limit was the result of complex motion in the mirror mount rather than the stability limit of the system. The system is shown to be insensitive to pure piston phase variations equivalent to an object velocity of over 3 m s?1.


Patel, R., Achamfuo-Yeboah, S., Light, R., & Clark, M. (2012). Ultrastable heterodyne interferometer system using a CMOS modulated light camera. Optics Express, 20(16),

Journal Article Type Article
Publication Date Jul 30, 2012
Deposit Date Mar 27, 2014
Publicly Available Date Mar 27, 2014
Journal Optics Express
Electronic ISSN 1094-4087
Publisher Optical Society of America
Peer Reviewed Peer Reviewed
Volume 20
Issue 16
Public URL
Publisher URL


PatelUltrastable.pdf (1.2 Mb)

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