Image Processing Using THG for Image Correlation      HalimAll Optical Image Processing            UsingThird Harmonic Gen...
Image Processing Using THG for Image Correlation               Halim                                 Table of ContentsTopi...
Image Processing Using THG for Image Correlation                                        HalimPaper Reviewed:Third-harmonic...
Image Processing Using THG for Image Correlation                                         HalimOptical Image CorrelationOpt...
Image Processing Using THG for Image Correlation                                             HalimIn many current image co...
Image Processing Using THG for Image Correlation                                      HalimFigure 1 shows that three coher...
Image Processing Using THG for Image Correlation                                              HalimFigure 3: Vector mismat...
Image Processing Using THG for Image Correlation                                      HalimImportance of OrientationA majo...
Image Processing Using THG for Image Correlation                                                    HalimFigure 6: Realist...
Image Processing Using THG for Image Correlation                                     HalimFuture WorkNew kinds of molecule...
Image Processing Using THG for Image Correlation                                   HalimReferences   1. Third-harmonic gen...
Image Processing Using THG for Image Correlation                                  Halim      R. Sai Santosh Kumar, S. Venu...
Upcoming SlideShare
Loading in …5
×

All optical image processing using third harmonic generation for image correlation

890 views

Published on

Term Paper: All optical image processing using third harmonic generation for image correlation

Optical Information Processing Course

Monday, 20th December, 2010

Published in: Technology, Education
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
890
On SlideShare
0
From Embeds
0
Number of Embeds
4
Actions
Shares
0
Downloads
0
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide

All optical image processing using third harmonic generation for image correlation

  1. 1. Image Processing Using THG for Image Correlation HalimAll Optical Image Processing UsingThird Harmonic Generation For Image Correlation Md. Faisal Halim (Faissal) Optical Information Processing Course Prof. Dorsinville Monday, 20th December, 2010Monday, 20th December, 2010 1
  2. 2. Image Processing Using THG for Image Correlation Halim Table of ContentsTopic Page NumberPaper Reviewed 3Motive: Computing 3Optical Image Correlation 44-f Architecture 5Third Harmonic Generation 6Contrast of the Detected Image 7Importance of Orientation 8Time Gating 8Future Work 10Conclusion 10References 11Monday, 20th December, 2010 2
  3. 3. Image Processing Using THG for Image Correlation HalimPaper Reviewed:Third-harmonic generation and its applications in optical image processingCanek Fuentes-Hernandez, Gabriel Ramos-Ortiz, Shuo-Yen Tseng, Michael P. Gajaand Bernard KippelenJ. Mater. Chem., 2009, 19, 7394–7401DOI: 10.1039/b905561dMotive: ComputingJust as an anecdote, an IBM Road Runner Supercomputer (the world’s fastestsupercomputer) occupies 560 m2 of real estate and can run 1.7x1015 Floating PointOperations Per Second. 2 Dimensional image processing, on the other hand, whichimplements matrix convolutions and multiplications, when implemented with ultrafastnonlinear optical processes, can supersede 1016 Operations Per Second1.So, by utilizing the massive parallelism offered by 2D signal processing, the highrepetition rates of the ever faster laser sources2, and inherently ultrafast nonlinear opticalprocesses it will be possible to produce ever faster computers. This will scale up thespeed of computing, and thus extend their range of applications far beyond what the sizereduction of electronic chip components would otherwise allow, and so opticalinformation processing may become the new avenue that allows the computing industryto keep up with Moore’s Law.Monday, 20th December, 2010 3
  4. 4. Image Processing Using THG for Image Correlation HalimOptical Image CorrelationOptical image correlation is just one of the many applications of optical computing, and itmay one day make complex tasks that are done after the digitization, where computationsare performed on an electronic readout, a thing of the past. To give an analogy, when amodern radar system detects signals from a target it takes a digital readout, thencompares the spectral (and temporal) characteristics against a database of knownsignatures to identify the target. Such a system has a number of disadvantages, like (a)digitization is an intermediate step, and (b) digital signal processing, using electronics, isan inherently slower process than optical processes. If such processing could be doneeven before the received signal is read out by the radar system, however, then the systemcould perform a lot faster. This is where optical image correlation comes in. Imagecorrelation, when done in the optical regime, is useful because then physical processeslike harmonic generation can be utilized to generate a flag signal if and only if a targetsignal if detected (the flag signal, at a shorter wavelength than the target signal, alerts thesystem, or its users, of the presence of the intended target’s signal). Third harmonicgeneration (THG), while less efficient than second harmonic generation, is a good choiceof process for optical image correlation because it can happen where three coherent lightbeams interact1, much like the interaction of three coherent beams of equal wavelength,but different propagation vectors, in four wave mixing process where the three incomingbeams sum up to their third harmonic3. In fact, there are groups that are doing four wavemixing using the 4-f architecture (which is popular for image processing4)5,6.Monday, 20th December, 2010 4
  5. 5. Image Processing Using THG for Image Correlation HalimIn many current image correlation systems the incoming signals are sent through a spatiallight modulator (SLM) and the signal that one is looking for, as well as the background,are at the same wavelength. Using THG, however, the presence of a sought after signalwill trigger THG, so the lack of the third harmonic of the fundamental wavelength willindicate the absence of the sought after signal (more on this later). This does not removethe necessity of the SLM, however, as it may still be required to project the spectralcharacteristics of a sought after signal, and the signal from the target will have to interactwith it (and also a Gaussian signal) for THG to happen.4-f ArchitectureThe 4-f architecture used by this group is as follows:Figure 1: 4-f Architecture; an SLM can be used in the position of h, so that one may change whatobject one wants to detect.Monday, 20th December, 2010 5
  6. 6. Image Processing Using THG for Image Correlation HalimFigure 1 shows that three coherent beams, when propagating non collinearly, can undergoTHG in a suitable material (in this case, a stable, polymeric, solution processable materialwith a high χ(3), preferably a high absorption at the fundamental wavelength, and a lowabsorption at the third harmonic). If one of the beams goes through a pinhole (r), onegoes through a mask (h – the target being searched for) and the other (g) acts as the signalcomes in from a remote source (rather than through the diffractive optical element) thenthe image in the back plane will show bright spots where the spatial features andorientation of g match the features and orientation in h. In other words, wherever in theimage g there is a ‘copy’ of h, there will be a corresponding bright spot (in the shape of h)in the image in the back plane.Third Harmonic GenerationFigure 2: Propagation vectors for THG7Owing to the direction of the propagation vectors of the incoming light for THG (seeFigures 27 and 3) the incoming light and the THG light are spatial separated, and thus donot have to be separated using further optics, and there is no ambiguity as to the source ofthe light, upon detection at the back plane.Monday, 20th December, 2010 6
  7. 7. Image Processing Using THG for Image Correlation HalimFigure 3: Vector mismatch between the exciting and THG modes seen for (a) two beam excitationand (b) 3 beam excitation, along with the resulting spatial separation of the beams in the image planeContrast of the Detected ImageIn such a system the radius of the pinhole r (from Figure 1) dictates the sharpness,contrast and brightness of the detected image, as shown in Figure 4.Figure 4: Size of r decides contrast and brightness of detected imageMonday, 20th December, 2010 7
  8. 8. Image Processing Using THG for Image Correlation HalimImportance of OrientationA major drawback of the system used here is that the orientation of the detection mask (h,from Figure 1) dictates how well (and if) the signal being sought is even detected, asshown in Figure 5.Figure 5: Orientation of mask, relative to signal, dictates detection probabilityTime GatingOwing to the fact that an ultrashort pulse will get elongated by scattering media in a realsystem (see Figure 6) a time gating system will reduce the effects of scattering (Figures 7and 8), by only doing THG with the ballistic photons.Monday, 20th December, 2010 8
  9. 9. Image Processing Using THG for Image Correlation HalimFigure 6: Realistic System; note that h is used as the signal from the remote location, rather than g,here, as opposed to the text of this paper. ‘r’ is used as the gating signal for THG. Clearly, the THGsignal is separated, spatially, from the NIR (fundamental) signal.Figure 7: Effects of time gating: the bottom row shows the delay between the incoming signal and thegating (mfp = mean free path). The excitation was a 1550nm, and the detection was done at 517nm.Figure 8: Time gating the systems pulse, from Figure 6, can be used to select only the ballisticphotons from a region being scanned.Monday, 20th December, 2010 9
  10. 10. Image Processing Using THG for Image Correlation HalimFuture WorkNew kinds of molecules, like octupolar molecules, with higher absorption in at thefundamental wavelength, and lesser absorption at the THG wavelength will enhance suchapplications, even though this group has done some work on the materials used to makethe film for THG8,9,10.ConclusionAn optical image correlator has been implemented, and it is all optical. Completeindependence from the use of SLMs has not yet been achieved, but future all opticalsystems could eventually do for optical surveillance what radar target databases has donefor air surveillance, only they would work much faster.Monday, 20th December, 2010 10
  11. 11. Image Processing Using THG for Image Correlation HalimReferences 1. Third-harmonic generation and its applications in optical image processing Canek Fuentes-Hernandez, Gabriel Ramos-Ortiz, Shuo-Yen Tseng, Michael P. Gaja and Bernard Kippelen J. Mater. Chem., 2009, 19, 7394–7401 DOI: 10.1039/b905561d 2. Recent developments in compact ultrafast lasers Ursula Keller Nature 424, 831-838 (14 August 2003) DOI: 10.1038/nature01938 3. Springer Handbook of Lasers and Optics Copyright, 2007 Frank Träger (Ed.) 4. Optical Signal Processing Anthony VanderLugt Wiley, 2005 5. Degenerate multi-wave mixing inside a 4f imaging system in presence of nonlinear absorption K. Fedus, G. Boudebs, H. Leblond Appl Phys B (2010) 100: 827–831 DOI 10.1007/s00340-010-4004-z 6. Ultrafast nonlinear optical properties of alkyl phthalocyanines investigated using degenerate four-wave mixing techniqueMonday, 20th December, 2010 11
  12. 12. Image Processing Using THG for Image Correlation Halim R. Sai Santosh Kumar, S. Venugopal Rao, L. Giribabu, D. Narayana Rao Optical Materials 31 (2009) 1042–1047 7. Four-Wave Mixing and its Applications CW Thiel http://citeseerx.ist.psu.edu/viewdoc/download? doi=10.1.1.118.63&rep=rep1&type=pdf 20th December, 2010 8. "Ultrafast optical image processing based on third-harmonic generation in organic thin films“ Fuentes-Hernandez et. al. APPLIED PHYSICS LETTERS 91, 131110, 2007 9. "Thick Optical-Quality Films of Substituted Polyacetylenes with Large, Ultrafast Third-Order Nonlinearities and Application to Image Correlation“ Chi, et. al. Adv. Mater. 2008, 20, 3199–3203 10. “Second-order nonlinear optical properties of octupolar molecules structure– property relationship” Kim, et. al. J. Mater. Chem., 2009, 19, 7402–7409Monday, 20th December, 2010 12

×