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Munther Gdeisat

Phase unwrapping, Wavelet transform profilometry (WTP), and MEtrology GUided RAdioTHerapy (MEGURATH). Munther Gdeisat. Phase unwrapping. Phase unwrapping. Problem statement 2D phase unwrapping 3D phase unwrapping Publicity—free source code. What is phase unwrapping?.

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Munther Gdeisat

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  1. Phase unwrapping, Wavelet transform profilometry (WTP), andMEtrology GUided RAdioTHerapy(MEGURATH) Munther Gdeisat

  2. Phase unwrapping

  3. Phase unwrapping • Problem statement • 2D phase unwrapping • 3D phase unwrapping • Publicity—free source code

  4. What is phase unwrapping? • Suppose that you have a signal, an image or a video. • The required information is embedded in the phase of the signal, image or video • To extract the phase information you need an algorithm • Fourier transform • Wavelet transform • Etc… • Normally, these algorithms produce complex data. • The phase can be extracted using the arctangent function that operates on these complex data.

  5. What is phase unwrapping? • The arctangent function extracts the required phase information. • But this information cannot exceed the range - and +. • If the original information exceeds the 2 range, then • The extracted phase is wrapped • And an unwrapping algorithm is required.

  6. 1D phase unwrapping- example 1 • Phase unwrapping appears simple at the first glance but in reality it is a very difficult problem.

  7. 1D phase unwrapping

  8. 1D phase unwrapping

  9. Unwrapping using basic algorithm Unwrapping using basic algorithm Unwrapping using basic algorithm Unwrapping using basic algorithm Unwrapping using basic algorithm Unwrapping using basic algorithm Unwrapping using basic algorithm An image An image An image An image An image An image An image An image An image Unwrapping using our algorithm Unwrapping using our algorithm Unwrapping using our algorithm Unwrapping using our algorithm The image is wrapped The image is wrapped The image is wrapped The image is wrapped The image is wrapped 2D phase unwrapping-example 2 Unwrapping using basic algorithm An image Unwrapping using our algorithm The image is wrapped

  10. Unwrapping using our algorithm Unwrapping using LP algorithm Unwrapping using Flynn algorithm The image

  11. Example 3 • Doris Mannequin • Information encoded in the phase of the fringe pattern • The phase information are extracted using the Fourier transform. The resultant image is wrapped • Unwrapping the image to get the required height information.

  12. 2D phase unwrapping • Hundreds of algorithms already proposed in the literature • The robust phase unwrapping techniques are time consuming (10 seconds or more to process an image with the size of 512  512 pixels) • Our algorithm is robust and requires 0.25 seconds to process an image with the size of 512  512 pixels • It is easy to understand-but hard to program • The C language source code is available to download for free from GERI website.

  13. How the algorithm does work? • The quality of each pixel is calculated using its 8 direct neighbours • Horizontal and vertical edges are constructed. • Edges connect two pixels together. • The quality of the edges are calculated • Search for the edge with the highest quality • Unwrap the two pixels that it connects or • Unwrap a pixel and a region that it connects or • Unwrap the two regions that it connects • Search for the next unprocessed edge with the highest quality • Unwrap the two….. • And so on for the rest of edges

  14. 3D phase unwrapping • Sometimes we are required to unwrap a sequence of images (i.e., video data) • The existing algorithms are very time consuming • The famous prelude 3D phase unwrapper requires five days to process a volume of 512  512  50 voxels. • Other unwrappers require few minutes to unwrap such data volume but they are not robust. • Our 3D phase unwrapper is fast, robust and free to download • It requires less than a minute to process this data volume. • Our 3D phase unwrapper is more robust than any other existing 3D phase unwrappers. • We have published three journal papers and two conference papers about 2D and 3D phase unwrapping. • One of these journal papers is very famous and it has been cited 19 times.

  15. Phase unwrapping We got many customers to our phase unwrappers • 1. The Christie Hospital, Manchester, UK. http://www.christie.nhs.uk/ • 2. EADS Astrium, Germany. This is a multinational aerospace manufacturer of satellite systems. Its website is http://www.astrium.eads.net/ • 3. The European Southern Observatory based in Australia. Their website is http://www.eso.org/public/ • 4. The Helen Wills Neuroscience Institute at the University of California, Berkeley, Their website is http://neuroscience.berkeley.edu/. • 5. Our phase unwrappers have been integrated in SciPy free open-source mathematical library. The website for the library is http://www.scipy.org/. • 6.Microgravity Research Centre  Universite Libre de Bruxelles • And many we do not know!!!

  16. Phase unwrapping • Just search in Google the words phase unwrapping. This search will produce around 100,000 pages. • Search for the phrase “phase unwrapping” This will produce around 50,000 pages approximately. • We are number four after in both searches • Wikipedia • Stanford university (just a tutorial) • An Italian university (just a tutorial)

  17. Wavelet transform profilometry

  18. Wavelet transform profilometry • Wavelet transform profilometry means the utilisation of the continuous wavelet transform to extract the phase information from a fringe pattern. • There are two methods to perform this task • One-dimensional continuous wavelet transform • Already exists in the literature • Two-dimensional continuous wavelet transform • Has been developed in GERI

  19. Wavelet transform profilometry • This algorithm has many advantages over the Fourier transform method • little edge distortion • The extracted phase is more accurate • No limit on the number of fringes in an image • Better noise performance

  20. Example 1: a fringe analysed using wavelet and Fourier methods Fringe pattern

  21. Wrapped phase maps using… Wavelet transform Wavelet transform Fourier transform Fourier transform Fourier transform

  22. Unwrapped phase map using… Wavelet transform Fourier transform

  23. A fringe pattern with two fringes only analysed using the wavelet method

  24. The wavelet method can deal with holes in a fringe pattern image

  25. Wavelet software • We (Munther and Abdul-Basit) have developed a software in C that is capable of extracting the required phase information from a fringe pattern using the wavelet method. • I will publish this software on GERI website and make it available to download for free • Repeating the phase unwrapping good experience

  26. Wavelet software • We have spent over one year in writing this wavelet software. • The execution time required to analyse a 512 X 512 pixels fringe pattern in Matlab using the wavelet method is approximately five minutes. • The same operation requires less than one second using our software. • We have been invited to write a tutorial paper about this topic to the Optics and Lasers in Engineering Journal. • We have published three journal papers and three conference papers about this topic

  27. MEtrology GUided RAdioTHerapy(MEGURATH)

  28. Headlines • Introduction • Specifications • Components • Processing Pipeline • Future Work

  29. MEGURATH • This system is designed and built to enable the medics to measure the height map of human bodies. • This is an important step in cancer radiotherapy treatment

  30. Introduction • A state-of-the-art 3D body measurement system using fringe analysis • A catalogue of fringes analysis, phase unwrapping and fringes calibration methods were employed • User preferences of speed and robustness • System currently uses only one sensor unit (CCD camera and LCOS projector)

  31. Connection cables SSU: single sensor unit MSFMS: multi-sensor fringe measurement system Camera and projector Camera and projector Camera and projector SSU MSFMS Object 3D measurement System Block Diagram • Monochrome cameras • Optical filters to get three channels: • XB08 (Blue) • XB21 (Green) • XB24 (Red)

  32. Specifications • Field-of-view: 40cm x 40cm x 40cm • Measurement speeds: From 5 to 14 fps depending on pre-adjusted settings Phase stepping Fourier Wavelet • Maximum error: 0.5 mm

  33. Components 1/4 • System simply consists of projector, camera, processing station and processing software

  34. Conventional LCD projector LCos projector Components 2/4 • Projector: Canon XEED SX60 • LCoS technology: • Advantages • Low pixelisation • High brightness (2500 lumens)

  35. Components 3/4 • Camera: Prosilica GE1380 • GigE technology: • Monochrome • Progressive scan CCD • Sensitive Camera • 20 fps @ 1360 × 1024 • 35 fps @ 512 x 512 • Direct image registration to the system memory via a compatible Gigabit port

  36. Components 4/4 • Processing software:

  37. Output Buffer Grabbed Images from the Camera Processing Thread Input Thread Output Thread Input Buffer Display and/or store according to the user preferences Processing Pipeline • Multithreaded processing framework: • Input Thread: Project and grab frames • Processing thread: Apply measurement, unwrapping and calibration techniques • Output thread: Save/display results

  38. Thank you for listening.Any questions or suggestions?

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