Difference between revisions of "Ultrastable heterodyne interferometry using a modulated light camera"

From Applied Optics Wiki
Jump to: navigation, search
 
Line 20: Line 20:
  
 
<bibtex>
 
<bibtex>
@ARTICLE{Patel2012author = {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{Patel2014Title                      = {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 regionTwo 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} }
 
</bibtex>
 
</bibtex>
  
 
<bibtex>
 
<bibtex>
@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{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}}
 
</bibtex>
 
</bibtex>
  
 
<bibtex>
 
<bibtex>
@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} }
+
@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}}
 
</bibtex>
 
</bibtex>

Latest revision as of 12:13, 18 November 2014

Ultrastable heterodyne interferometry using a modulated light camera


PhD student: Rikesh Patel

Project Supervisor: Matt Clark


Project Brief:

Widefield ultrastable heterodyne interferometer
Widefield two laser interferometer

Interferometry is used in a wide variety of fields for the instrumentation and analysis of subjects and the environment. Captured widefield interference patterns can be used to determine changes in the optical path length of interfering beams across a 2D area. The heterodyne interferometers use light with different optical frequencies to generate a fringe pattern that is modulated at a frequency equal to the optical frequency difference (beat frequency). A widefield heterodyne system is not straightforward to bring into practice, however, it does offer some benefits such as direct phase interpretation and the suppression of low frequency background light in interferograms.

For this project, a widefield heterodyne interferometer system was developed. A custom prototype modulated light camera (MLC) chip was used to capture both homodyne and heterodyne fringe patterns. The 32x32 pixel camera is capable of continuously demodulating incident modulated light at frequencies between 100 kHz and 17 MHz. With modifications to the system, an ultrastable widefield heterodyne interferometer system was implemented. The intention of this system was to eliminate the contribution of piston phase to a captured interferogram without the need for common path optics. In contrast to the standard heterodyne setup, the reference signal used in the demodulation process was derived from one of the pixels on-board the MLC, rather than from an external source. This new local reference signal tracks the common changes in the temporal phase detected by all the MLC's pixels, eliminating piston phase and substantially reducing the contributions of unwanted vibrations and microphonics from interferograms. As an application of the ultrastable system, a novel interferometer has been developed that captures the widefield fringe patterns generated by interfering two independent light sources, rather than by a single split source. The two separately stabilised HeNe lasers, constructed in the laboratory, produce light with a reasonably stable output frequency. Interfering two of these sources produce a heterodyne interference pattern with an unknown beat frequency. The beat frequency continuously varies because of the variation in the output frequency of each laser, but these stabilised lasers produce a beat frequency that drift by as little as 3 MHz over 30 minutes. As the ultrastable system tracks changes in the temporal phase and instantaneous frequency of an incident fringe pattern, it can be used to track the variations in the modulation frequency generated by the fluctuations in the two separate lasers.

Thesis link: PDF

Publications:

Rikesh Patel, Samuel Achamfuo-Yeboah, Roger Light, Matt Clark - Widefield two laser interferometry
Opt. Express 22(22):27094--27101, Nov 2014
http://www.opticsexpress.org/abstract.cfm?URI=oe-22-22-27094
Bibtex
Author : Rikesh Patel, Samuel Achamfuo-Yeboah, Roger Light, Matt Clark
Title : Widefield two laser interferometry
In : Opt. Express -
Address :
Date : Nov 2014

Rikesh Patel, Samuel Achamfuo-Yeboah, Roger Light, Matt Clark - Ultrastable heterodyne interferometer system using a CMOS modulated light camera
Opt. Express 20(16):17722--17733, Jul 2012
http://www.opticsexpress.org/abstract.cfm?URI=oe-20-16-17722
Bibtex
Author : Rikesh Patel, Samuel Achamfuo-Yeboah, Roger Light, Matt Clark
Title : Ultrastable heterodyne interferometer system using a CMOS modulated light camera
In : Opt. Express -
Address :
Date : Jul 2012

Rikesh Patel, Samuel Achamfuo-Yeboah, Roger Light, Matt Clark - Widefield heterodyne interferometry using a custom CMOS modulated light camera
Opt. Express 19(24):24546--24556, Nov 2011
http://www.opticsexpress.org/abstract.cfm?URI=oe-19-24-24546
Bibtex
Author : Rikesh Patel, Samuel Achamfuo-Yeboah, Roger Light, Matt Clark
Title : Widefield heterodyne interferometry using a custom CMOS modulated light camera
In : Opt. Express -
Address :
Date : Nov 2011