Femto-photography is a term used to describe a technique for recording the propagation of ultrashort pulses of light through a scene at a very high speed. A femto-photograph is equivalent to an optical impulse response of a scene and has also been denoted by terms such as a light-in-flight recording or transient image. Femto-photography of macroscopic objects was first demonstrated using a holographic process in the 1970s by Nils Abramsson at the Royal Institute of Technology (Sweden). A research team at the MIT Media Lab led by Ramesh Raskar, together with contributors from the Graphics and Imaging Lab at the Universidad de Zaragoza, Spain, more recently achieved a significant increase in image quality using a streak camera synchronized to a pulsed laser and modified to obtain 2D images instead of just a single scanline.
In their publications, Raskar's team claims to be able to capture exposures so short that light only traverses 0.6 mm (corresponding to 2 picoseconds, or 2x10−12 seconds) during the exposure period, a figure that is in agreement with the nominal resolution of the Hamamatsu streak camera model C5680, on which their experimental setup is based. Recordings taken using the setup have reached significant spread in the mainstream media, including a presentation by Raskar at TEDGlobal 2012 Furthermore, the team was able to demonstrate the reconstruction of unknown objects "around corners", i.e., outside the line of sight of light source and camera, from femto-photographs.
In 2013, researchers at the University of British Columbia demonstrated a computational technique that allows the extraction of transient images from time-of-flight sensor data without the need for ultrafast light sources or detectors.
Other uses of the term
Prior to the aforementioned work, the term "femto-photography" had been used for certain proposed procedures in experimental nuclear physics.
- Abramsson, Nils (1978). "Light-in-flight recording by holography". Optics Letters 3 (4): 121–123. doi:10.1364/OL.3.000121.
- Smith, Adam; James Skorupski; James Davis (2008). "Transient Rendering". Technical Report, School of Engineering, University of California Santa Cruz. UCSC-SOE-08-26. Retrieved 31 July 2014.
- Kirmani, A.; Hutchison, T.; Davis, J.; Raskar, R. (2009). "Looking around the corner using transient imaging". IEEE 12th International Conference on Computer Vision: 159–166. doi:10.1109/ICCV.2009.5459160.
- "Visualizing Light at Trillion FPS, Camera Culture, MIT Media Lab". Web.media.mit.edu. 2011-12-13. doi:10.1145/2037715.2037730. Retrieved 2012-10-04.
- Velten, Andreas; Di Wu; Adrian Jarabo; Belen Masia; Christopher Barsi; Chinmaya Joshi; Everett Lawson; Moungi Bawendi; Diego Gutierrez; Ramesh Raskar (July 2013). "Femto-Photography: Capturing and Visualizing the Propagation of Light" (PDF). ACM Transactions on Graphics 32 (4). Retrieved 21 November 2013.
- "Slow art with a trillion frames per second camera". Dl.acm.org. doi:10.1145/2037715.2037730. Retrieved 2012-10-04.
- Hamamatsu Corporation. "Universal Streak Camera C5680 Series - Measurements Ranging From X-Ray to Near Infrared With a Temporal Resolution of 2 ps". Retrieved 2013-11-22.
- Information from alldatasheet.com
- Velten, Andreas; Thomas Willwacher; Otkrist Gupta; Ashok Veeraraghavan; Moungi G. Bawendi; Ramesh Raskar (20 March 2012). "Recovering three-dimensional shape around a corner using ultrafast time-of-flight imaging". Nature Communications 3. doi:10.1038/ncomms1747.
- TEDGlobal 2012. "Ramesh Raskar: Imaging at a trillion frames per second | Video on". Ted.com. Retrieved 2012-10-04.
- Heide, Felix; Matthias B. Hullin; James Gregson; Wolfgang Heidrich. "Low-Budget Transient Imaging using Photonic Mixer Devices". In: ACM Trans. Graph. 32(4) (Proc. SIGGRAPH 2013). Retrieved 22 November 2013.
- "Nucleon hologram with exclusive leptoproduction". Exclusive Processes at High Momentum Transfer. May 15–18, 2002. Retrieved 4 October 2012.
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