Dynamic Scattering: Meet Visiting Scholar Janos Keresztes

    Date Posted: 
    Thursday, July 9, 2015

    Given its world-class reputation, it's no surprise that the College of Optical Sciences attracts world-class talent. Augmenting our ranks each semester are several visiting scholars, faculty and students who travel to Tucson for a few weeks or months to collaborate with OSC researchers.

    Portrait of Janos Keresztes in front of the entrance to the Meinel BuildingJanos Keresztes is one such visitor. A Ph.D. student at the University of Leuven (Belgium), Janos has been working with Associate Dean R. John Koshel since January. He's kept busy in his short six months – at the podium, at outreach events and, of course, in the lab. We were lucky to catch a few minutes with him for this week's Watts Up!; alas, he heads back to Europe on Wednesday.

    Where are you from?

    I was born and raised in Liege, Belgium. I obtained my bachelor’s degree in engineering with a major in electronics and minor in computer sciences at the University of Liege. I pursued my master's in electrical engineering there.

    I got into optics thanks to Prof. Serge Habraken and computed depth maps using optics for my master's thesis with ATA-Vision. Thanks to Prof. Jacques Verly, I further pursued a six-month internship through the European Commission's Leonard da Vinci program at Holografika, on 3-D image restoration for holographic displays. Although I loved the optics behind the screen, I was intrigued on the potential of images containing more than three colors. I engaged further as a Ph.D. student in the biophotonics group of Prof. Wouter Saeys at the University of Leuven.

    Image predicting bruises using SWIR hyperspectral imaging, overlaid with a SWIR image of bruised apples at 1,200 nanometersWhat is your research on?

    I work on short-wave infrared hyperspectral imaging for nondestructive food quality inspection, mainly early bruise detection in apples. Hyperspectral line scan imaging consists of acquiring, line-by-line, an object moving on a conveyor belt, where each line is dispersed using a spectrograph onto a camera sensor. The resulting image contains a full reflectance spectrum of hundreds of bands or colors per pixel, providing chemical information about the object. In the SWIR (1-2.5 micrometers), CH and OH bonds can be observed, enabling monitoring of moisture, sugars, fat and other compounds present in food.

    My research consists of improving data handling and the optics in SWIR HSI systems, including illumination uniformity, glare artifacts reduction and prediction model-building for real-time early fruit bruise detection.

    Why did you come to OSC?

    During my research in Belgium, I encountered glare artifacts from the waxy surface of apples due to my existing illumination system. After reading Prof. Koshel's work, I wished to follow his course on illumination engineering and broaden my optics knowledge. I met him during the 2014 Frontiers in Optics conference, where I had the chance to visit OSC. I also was introduced to polarization during the conference by Prof. Scott Tyo, who convinced me that it could reduce apple gloss in my images.

    At OSC, I worked on modelling optical properties of apples, including bidirectional scatter distribution function, polarization and shape, in ray-tracing software for more realistic results. I had the opportunity to measure the SWIR spectral radiance of my light source with professor Stuart Biggar, the BRDF of apples with Dr. John Stover, SWIR spectral BRDF of apples with Prof. Robert A. Norwood and Mueller matrix images of apples with Prof. Russell Chipman. I also had the chance to work with Jacob Boyer, an undergraduate student in the lab of Todd Horne, and Prof. Jim Burge on a multispectral polarimetric BRDF imager. I am collaborating with Prof. Jeong-Yeol Yoon from the UA agriculture department on microscopy.

    Janos Keresztes in front of the Meinel Building with the College of Optical Sciences sign in the backgroundWhat did you learn at OSC that you'll be taking back with you?

    I have learned far more things during my stay than I could imagine. I followed a FRED training and stray light course at Photon Engineering and ASAP and APEX training at Breault Research Organization, where I had inspiring chats with Dr. Robert Breault. I followed a Zemax training thanks to SOCk. I was introduced to the ins and outs of BRDF by Dr. John Stover, Rich Pfisterer and Dr. Mary Turner. I followed the courses OPTI 484/584: Polarized Light and Polarimetry, OPTI 518: Introduction to Aberrations, OPTI 485/585: Illumination Engineering and OPTI 439A/539A: From Photonics Innovations to the Marketplace. With the help of Prof. Koshel, I currently have four accepted SPIE conference oral presentations and am working on an illumination journal paper. More may come out of my research on BRDF and polarization. 

    One of my coolest experience was Laser Fun Day. It was truly inspiring to see 100 volunteers presenting a broad range of applications in optics, with more than 1,000 attendees. My top three activities were the laser maze, the polarized OSC logo and, of course, the electric pickle.

    I wish I could bring the sun of Tucson back with me (except the month of June). The College of Optical Sciences is the heaven of optics.

    Collage of Janos practicing martial arts with a partner and Janos scuba-divingName three neat things about you.

    1. I try to always have some Belgian chocolate with me, it makes people around me smile.
    2. I practice martial arts and scuba diving.
    3. I am a great fan of Hans Zimmer, and listen to his music themes all day long.


    From Janos – Top: image predicting bruises using SWIR hyperspectral imaging, overlaid with a SWIR image of bruised apples at 1,200 nanometers; bottom: Janos practicing vovinam viet vo dao and scuba diving