Difference between revisions of "Rikesh Patel"

@ARTICLE{Patel2012,  author = {Rikesh Patel and Samuel Achamfuo-Yeboah and Roger Light and Matt Clark},  title = {Ultrastable heterodyne interferometer system using a CMOS modulated light camera},  journal = {Opt. Express},  year = {2012},  volume = {20},  pages = {17722--17733},  number = {16},  month = {Jul},  abstract = {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 \&\#x0005B;Opt. Express 19, 24546 (2011)\&\#x0005D;, 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\&\#x02212;1 over a variety of frequencies from 18 Hz to 20 kHz (giving a variation in optical path length of 220 \&\#x003BC;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\&\#x02212;1.},  doi = {10.1364/OE.20.017722},  keywords = {Interferometric imaging ; Interferometric imaging},  owner = {rp},  publisher = {OSA},  timestamp = {2013.06.03},  url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-20-16-17722}, pdf = {http://optics.eee.nottingham.ac.uk/w/images/0/0f/Pap3.pdf}}

@ARTICLE{Patel2011a,  author = {Rikesh Patel and Samuel Achamfuo-Yeboah and Roger Light and Matt Clark},  title = {Widefield heterodyne interferometry using a custom CMOS modulated light camera},  journal = {Opt. Express},  year = {2011},  volume = {19},  pages = {24546--24556},  number = {24},  month = {Nov},  abstract = {In this paper a method of taking widefield heterodyne interferograms using a prototype modulated light camera is described. This custom CMOS modulated light camera (MLC) uses analogue quadrature demodulation at each pixel to output the phase and amplitude of the modulated light as DC voltages. The heterodyne interference fringe patterns are generated using an acousto-optical frequency shifter (AOFS) in an arm of a Mach-Zehnder interferometer. Widefield images of fringe patterns acquired using the prototype MLC are presented. The phase can be measured to an accuracy of {\textpm}6.6{\textdegree}. The added value of this method to acquire widefield images are discussed along with the advantages.},  doi = {10.1364/OE.19.024546},  owner = {rp},  publisher = {OSA},  timestamp = {2012.01.13},  url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-19-24-24546}, pdf = {http://optics.eee.nottingham.ac.uk/w/images/d/d6/Pap1.pdf}}

@Article{Patel2014,  Title                    = {Widefield two laser interferometry},  Author                  = {Rikesh Patel and Samuel Achamfuo-Yeboah and Roger Light and Matt Clark},  Journal                  = {Opt. Express},  Year                    = {2014},  Month                    = {Nov},  Number                  = {22},  Pages                    = {27094--27101},  Volume                  = {22},  Abstract                = {A novel system has been developed that can capture the wide-field interference pattern generated by interfering two independent and incoherent laser sources. The interferograms are captured using a custom CMOS modulated light camera (MLC) which is capable of demodulating light in the megahertz region. Two stabilised HeNe lasers were constructed in order to keep the optical frequency difference (beat frequency) between the beams within the operational range of the camera.This system is based on previously reported work of an ultrastable heterodyne interferometer \&\#x0005B;Opt. Express 20, 17722 (2012)\&\#x0005D;. The system used an electronic feedback system to mix down the heterodyne signal captured at each pixel on the camera to cancel out the effects of time varying piston phase changes observed across the array. In this paper, a similar technique is used to track and negate the effects of beat frequency variations across the two laser pattern. This technique makes it possible to capture the full field interferogram caused by interfering two independent lasers even though the beat frequency is effectively random.As a demonstration of the system\&\#x02019;s widefield interferogram capture capability, an image of a phase shifting object is taken using a very simple two laser interferometer.},  Doi                      = {10.1364/OE.22.027094},  Keywords                = {Interferometric imaging ; Interferometric imaging},  Owner                    = {rp},  Publisher                = {OSA},  Timestamp                = {2014.11.18},  Url                      = {http://www.opticsexpress.org/abstract.cfm?URI=oe-22-22-27094}, pdf = { http://optics.eee.nottingham.ac.uk/w/images/4/4d/Pap4.pdf} }