Wednesday, July 20, 2011

Looking forward..

Hey everyone..!

I'm back home again! Last week at COSI was such good fun! Next I look forward to Frontiers in Optics in October. This year FiO is in the Bay area. It's usually a big enough meeting that plenty of people travel to make it. So it's nice to have it in sunny California!

Although a large part of conferences involves checking out the latest and best in optics, much of it involves meeting new people and building strong professional relationships. Networking lunches, dinners and receptions are ideal for these. Most meetings also host exhibitions and poster sessions that let you connect with people who may have interests in your field.

In the past couple of years there have also been plenty of activities that are specifically targeted toward students and the somewhat younger crowd in optics. My favorite at FiO had been a couple of years ago in Rochester, they had Jorge Cham of PhD comics talk about procrastination! :) Some time back there was also the most awesome laser tag event and some cool eday demos. Young optics professionals from all over had come together to showcase all the cool and innovative stuff you can do with optics. Check out Nicole Moore's demo of a pinhole camera.

Ref: OSA E-day 2008,

This year's conference has quite a few fun events. I was just having a look at the Young Professionals and Student Activities link. The Entrepreneurs International Network (EIN) Workshop and VIP Industry Leaders Networking Event certainly look very useful! There's a Minorities and Women in OSA Tea that I'll attend.

Also, check out this Student Chapter Competition. It's going to be a contest - Mission Optical, where Student Chapters from all over the world will do optics demos for youth optics education using only ordinary household items.. under 25$.

I was thinking about the household items bit and you know, there actually are plenty of household items that can be used in optics experiments! A TV screen makes for an amazingly bright object with built-in illumination, plastic spoons show excellent stress birefringence, water and glass are always the good old reliable light-benders, jello can be cut out to be shaped like lenses, and as Nicole pointed out, even a Folger's coffee can is reusable as a lensless, pinhole camera! 

Promises to be highly imaginative, right? I'll be sure to check it out! Hope they take videos at this event.. or maybe I will!  

Thursday, July 14, 2011

COSI 2011 - part 3 (final)

Hey everyone.. 

Today was the last day. A lot more relaxed. I got to hang out with some friends and do some fun stuff.  

Sunny and blue!
Wish I had taken more pictures of us! Next time..
There is so much in terms of talks I haven’t written about. I’m going to mention just a few things next.

This year’s meeting included quite a few talks on areas related to Lithography. I liked that because I don’t often go to conferences that are focused only on lithography. But it’s an interesting area and very relevant to anybody interested in imaging. So it was good to find some talks on this topic here.

Mehdi Vaez Iravani from KLA Tencor spoke about metrology in the semiconductor industry – mainly inspection of patterned and unpatterned wafers and related issues. There was also a very nice talk on model based metrology for resist patterns by Arie Boef from ASML. I also got to meet Dr. Alan Rosenbluth from IBM, T. J. Watson Research Center. His work on identifying a correction factor for source radiance in photolithography is an example of how much depends on “little” details in lithography. Clearly speed and accuracy are so very important in this industry.

Kenny Kubala from Five Focal gave an interesting talk on improving yield in wafer level cameras. He talked about measuring errors in manufacturing. They have their own fast, model-based algorithm for measuring post-assembly errors such as decenter and air-gaps. 

There was a very interesting talk on superresolution due to spatial non-linearity effects in non-linear material by Christopher Barsi from Princeton. He showed increased resolution and wider FOV.

There was also an interesting talk from Marc Christensen’s group on using structured illumination for optical superresolution using active illumination in cameras. Manju, the speaker at COSI, told us they are starting off a company called SLIC Technology which is trying to productize this work. And hey, startups for superresolution are always cool in my book! 

There is much I may have skipped here. These conference posts are written in some haste. Hopefully no one will mind typos and misspelled names. And then there was so much good stuff that I just couldn’t attend because of parallel sessions that I needed to be in. There was lots of Fourier Transform Spectroscopy, Wavefront Sensing, Adaptive Optics, 3D imaging, localization imaging.. it goes on. I attended some, but lots, I missed! I am hoping my colleagues caught it and will give me an update. 

The best part of conferences is always people! I am really glad I got to catch up with old friends again, meet new folks! The enthusiasm and excitement everyone has for their work is always infectious. And at conferences we get it all in one concentrated dose! :)

Now it’s time to go home. Am at the gate now and super-happy that Toronto airport has free WiFi!! :)

Cheers and thanks for reading!

Wednesday, July 13, 2011

COSI 2011 - part 2

Hey everyone..!

Yesterday and today were packed. We met lots of people, heard lots of talks, had lots of discussions. At smaller meetings like this there is plenty of opportunity to meet people and chat. The breaks tend to be well spaced, and then yesterday there was a networking lunch and an evening reception. So it’s been interesting, intriguing, sometimes highly entertaining, and finally exhausting! :) There is still another morning’s worth of events to go. But most of the conference is almost over. Has been such good fun!

My colleagues - Prasanna, Jorge, David and Kathrin had a talk on design for better depth estimation. It was very well received. I think this was a really good meeting to present work from our group.

Now let me give you all an update on some of the interesting talks we saw past few days. This post is going to get terrifically newsy now.

Ravi Athale and David Brady gave some interesting talks dedicated to the memory of Dennis Healy and his vision for sensors and imaging. Ravi proposed all sorts of ideas and visions for the future. History and vision go very well together.  Certainly got everyone thinking.

There were many talks on Holography. They started out with Oscan’s group discussing LUCAS, an incoherent holography technique to image cells. Some of his results use prototype attachments for compact cell phones.

George Barbastathis’s group showed much work on 3D optical imaging. He gave a very interesting talk on quantitative reconstruction of phase objects, visualizing 3D flow, bubbles, etc. using digital holography including ideas for compressive sensing.

My own (earlier) group from Rochester, Jim Fienup’s research lab, showed results by Abbie Tippie on lensless synthetic aperture digital holography for gigapixel imaging. This work involves generating a digital hologram of an object and building up the hologram by scanning the detector to effectively obtain a larger aperture and more resolution. Abbie talked about sampling conditions, propagation approximations, defocus, aberrations, drift and other mosaicking errors and how to handle them all.   

David Brady’s group also collaborated on this project. They too showed results, by Sehoon Lim, on the corrections they have implemented for their system. Both groups had slightly different implementation issues. I love that this collaboration got so much research work done on that front.

Optical superresolution, as some of you may know, is the area of my thesis research. So I love work on superresolution. Zeev Zalevsky was at COSI today and gave a great talk on recent advances in superresolution imaging. This was a very nice review style talk with tons of info. He had so many slides to show. Even a 40 minute slot is sometimes not enough. I’ll put in a link here if I find his material or paper somewhere online.

Alden Jurling from the Fienup group talked about some interesting approximations that they found worked for them and helped to speed up broadband phase retrieval. He actually blurred some of his data to get rid of high frequencies (treating them like noise), which allowed him to quickly zero-in on a reasonable estimate. Speeding up algorithms is often critical for practical implementation. So it’s good to see them explore the regime of speed versus accuracy to try and find a balance.

Sam Thurman showed a useful method to estimate the OTF of an imaging system – phase and magnitude, using a binary Siemens Star Target. The cool thing is that his technique works even for undersampled images. This is probably because the Siemen’s Start Target has repetitive identical lines which, in my understanding, gives him multiple “measurements” and allows him to get around the sampling limits.  

Fredo Durand gave a very nice talk on computational photography, briefly describing the work on light fields, coded imaging, feature matching, SIFT, blind deconvolution and superresolution as done in the computational photography community.  

His talk was followed by another great talk by Edward Adelson where he demo-ed as well as talked about an elastomer they have developed, called GelSight, that easily deforms when touched by a feather, brush, thumb, even bubbles. This deformation can be seen on the other side of this skin-like Gel and imaged in 3D using photometric stereo. The images were impressive.

Ref: and

Ramesh Raskar’s group had an interesting talk on their picosecond camera – a streak camera that can capture picosecond phenomena, as long as they are repetitive events, using pulsed light and strategically sampled frames. They demonstrated images of light traversing a bottle, bouncing off of objects, etc.

Ed Dowski gave an interesting perspective on how optics may one day be manufactured like chips. Scalable, cost effective and easy to design.

Oh, and there was much work on CASSI and other such spectroscopy techniques, a lot of good talks from the Brady and Gehm groups.

It’s getting late now. But there is still more I want to note here. I’ll write again soon. 

Till then, cheerio and thanks for reading!

Monday, July 11, 2011

COSI 2011 - part 1

Hey everyone!

Quick update.. I am in Toronto for the Computational Optical Sensing andImaging (COSI), OSA meeting. This conference is held once every couple of years, usually collocated with Signal Recovery and Synthesis, Applied Industrial Optics, Adaptive Optics and Wavefront Sensing, Digital Holography and some other interesting meetings as part of the Imaging and Applied Optics Congress.

The two buildings on either side of CN tower 
look tilted in my pic!  What does that say 
about my cell phone's camera?

Today is our first day here. The whole Ricoh Innovations Inc. (RII), Digital Optics Research group is here. We have two talks at this meeting. One was today, Kathrin Berkner's and my submission on “Optimization of Spectrally Coded Mask for Multi-modal Plenoptic Camera” (CMD4) I'll put in a link to the paper once it gets online. Some people at the conference had already shown interest in the work. So despite being pretty late in the day we had a decent crowd. We had been looking forward to this for a while now and were glad to see the response.

Plenoptic imaging systems have been around for a while and promise to be very useful for digital refocusing, angular imaging, multimodal imaging, etc. Lately there is a lot of industry interest in exploring the potential for these kinds of applications. Our group works on the optics side of it - design, tolerancing, etc. Being in industry, these things are important to us. The research culture at RII is strong and we greatly value the opinion of the diverse academic research community. We got some great feedback and good discussions after the talk today. Thanks folks, for all your interest!

We have one more talk from RII coming up on Tuesday afternoon - 3D Imager Design through Multiple Aperture Optimization (JTuD4). Do stop by if you are at COSI 2011!   

Thursday, July 7, 2011

Meeting Jay Sharping - Fiber Optical Parametric Oscillators

Hey everyone!

Meeting time! I recently went to the dinner and meeting hosted by the N-Cal OSA chapter. This month the guest of honor was Professor Jay Sharping from the University of California at Merced. 

We were joined by a whole crowd of optics locals. Dinner with this group of people is always fun. I get to hear much about what else is going on with other groups and areas of optics. Here’s Jay (front) with Rick Rairden, Olaf Korth, Yujun Deng, Eric Hansotte and I’m-not-sure-who-that-is? I forced everyone to stop their discussion so I could click this pic and they kindly obliged! :) I couldn’t manage to get the whole table in one click. Need one of those 180 degree panoramic viewing cameras!

Fig.1. Dinner with Jay Sharping (front)
Afterwards we drove over to Xerox PARC where Jay talked about his work at UC Merced. UC Merced is a relatively new school, started around 2005, located about 90 minutes South-East from the Bay area. Jay is on their Physics faculty and heads the Applied Photonics Research Group.

Most of his research revolves around Optical Parametric Oscillators. OPOs are essentially used as tunable light sources. An OPO uses the principles of nonlinear optics i.e. the nonlinear influence of the electric field of light on the dielectric polarization of a material such as nonlinear crystals or fibers. 

In an OPO, an input pump frequency is passed through an optical non-linearity such as a nonlinear crystal or fiber to output a pulse at a different frequency. You can change the output frequency by tuning the phase matching properties of the nonlinear material. Jay’s team works specifically in the area of OPOs that use photonic crystal fiber to provide the non-linearity.  Photonic crystal fibers show similar nonlinear effects as ordinary optical fiber, along with the benefit of greater chi(3) nonlinearity. Here and here are two of his papers that elaborate a little more.

My interest in OPOs and femto second/pico second lasers stems from their use in two-photon microscopy, CARS (Coherent Anti-stokes Raman Spectroscopy) and other such non-linear imaging modalities.

Two-photon emission results from the absorption of two photons which are at twice the wavelength of absorption of a fluorescent dye. i.e. If your dye would fluoresce on the absorption of one photon at 350nm, instead it will fluoresce the same emission w/l if it is bombarded with two photons, each at 700nm. So effectively one ends up using much longer w/ls for two photon excitation. Longer w/ls penetrate deeper, so one can image deeper. Longer w/ls are also usually safer for living tissue. The nonlinear emission process is generally localized to the center of the beam where the intensity is maximum, hence it naturally imparts some amount of sectioning. Non-linear emission processes are less efficient for longer pulse widths (or continuous beams) since they require high peak intensities which can typically be achieved only in short pulse widths.

Pulsed lasers are commonly used as sources for non-linear imaging when a narrow band of wavelength tunability is sufficient. In cases where a broad range of tunable wavelengths are required, OPOs offer significant advantages. 

Jay showed some good results using their Fiber-OPO for CARS imaging. I also liked his one-line description of CARS, “If you tune two frequencies to coincide with the Raman mode of a material, you can efficiently excite that mode and use it to image!” That’s succinct! Well, CARS sure makes for useful images! 

OPOs do have other uses in probing material properties, quantum states, etc. I haven't written much about that here. But you can look up his work at UC Merced as well as his earlier collaborators, the Gaeta Group at Cornell for more details if you are interested.

Cheers and thanks for reading!