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Light Field = Array of (virtual) Cameras Sub-aperture Virtual Camera = Sub-aperture View Marc Levoy MERL Mask-Enhanced Cameras: Heterodyned Light Fields & Coded Aperture Veeraraghavan, Raskar, Agrawal, Mohan & Tumblin Sensor Sensor Microlens array Mask Plenoptic Camera Heterodyne Camera • Samples individual rays • Samples coded combination of rays • • Predefined spectrum for lenses Chromatic abberration • Supports any wavelength • High alignment precision • Reconfigurable f/#, Easier alignment • Peripheral pixels wasted pixels • • No wastage High resolution image for parts of scene in focus • Negligible Light Loss • 50 % Light Loss due to mask x1 x2 x1’ = x1 + θi*z θi θj θj Shear of Light Field θ θi θ θj x2 l(x,θ) x1 x l(x,θ) x x1 x'1 Light Propagation (Defocus Blur) θ l(x,θ) 2-D FFT L(fx,fθ) fθ x fx Central Slice Line Integral 1-D FFT Captured Photo FFT of Captured Photo Space of LF representations Time-frequency representations Phase space representations Quasi light field Other LF representations Other LF representations Rihaczek Distribution Function Observable LF Augmented LF Traditional light field incoherent coherent WDF Quasi light fields the utility of light fields, the versatility of Maxwell We form coherent images by Other LF representatio ns Other LF representatio ns Rihaczek Distribution Function Observable LF Augmente d LF WDF Traditiona l light field incoherent formulating, coherent capturing, and integrating quasi light fields. (i) Observable Light Field • • • move aperture across plane look at directional spread continuous form of plenoptic camera scene aperture position s direction u (ii) Augmented Light Field with LF Transformer light field transformer WDF Augmented LF LF LF LF LF negative radiance (diffractive) optical element Light Field LF propagation LF propagation Interaction at the optical elements 8 Virtual light projector with real valued (possibly negative radiance) along a ray real projector first null (OPD = λ/2) virtual light projector real projector 9 (ii) ALF with LF Transformer 1 (iii) Rihaczek Distribution Function Tradeoff between cross-interference terms and localization u y (i) Spectrogram non-negative localization (ii) Wigner localization cross terms (iii) Rihaczek localization complex 3m u 0m 0m y 3m 0m y 3m 0m y 3m Property of the Representation Constant along rays Non-negativity Coherence Wavelength Interference Cross term Traditional LF always constant always positive only incoherent zero no Observable LF nearly constant always positive any coherence state any yes Augmented LF only in the paraxial region positive and negative any any yes WDF only in the paraxial region positive and negative any any yes complex any any reduced Rihaczek DF no; linear drift Benefits & Limitations of the Representation Simplicity of Adaptability Ability to Modeling computatio to current Near Field propagate wave optics n pipe line Traditional LF no very simple high no yes Observable not x-shear LF yes modest low yes yes Augmented LF x-shear yes modest high no yes WDF x-shear yes modest low yes yes yes better than WDF, not as simple as LF low no yes Rihaczek DF x-shear Far Field x-shear Motivation • What is the difference between a hologram and a lenticular screen? • How they capture ‘phase’ of a wavefront for telescope applications? • What is ‘wavefront coding’ lens for extended depth of field imaging? Application - Wavefront Coding Dowski and Cathey 1995 point in scene cubic phase plate small change in blur shape same aberrant blur regardless of depth of focus Can they be part of Computer Vision? Moving away from 2D images or 4D lightfields? Wavefront coding: WLC mobile phone cameras Holography: Reference targets Rendering: New perspective projection methods QuickTime™ and a BMP decompressor are needed to see this picture. Gaussian beam lasers: Modern active illumination Rotating PSF: Depth from defocus Raskar, Camera Culture, MIT Media Lab Computational Photography http://computationalphotography.org 1. Epsilon Photography – Low-level Vision: Pixels – Multiphotos by bracketing (HDR, panorama) – ‘Ultimate camera’ 2. Coded Photography – Mid-Level Cues: • Regions, Edges, Motion, Direct/global – Single/few snapshot • Reversible encoding of data, Lightfield – Additional sensors/optics/illum – ‘Smart Camera’ 3. Essence Photography – – – Not mimic human eye Beyond single view/illum ‘New artform’ Resources Rihaczek Distribution Function Observable LF Augmented LF Traditional light field • Website – http://scripts.mit.edu/~raskar/lightfields/ – Or follow http://cvpr2009.org tutorial pages • Key new papers • • • Wigner Distributions and How They Relate to the Light Field Zhengyun Zhang and Marc Levoy, ICCP 2009 (best paper) Augmenting Light Field to Model Wave Optics Effects , Se Baek Oh, Barbastathis, Raskar (in Preparation) Quasi light fields: extending the light field to coherent radiation , Anthony Accardi, Wornell (in Preparation) WDF Acknowledgements • Darthmuth – Marcus Testorf, • MIT – Ankit Mohan, Ahmed Kirmani, Jaewon Kim – George Barbastathis • Stanford – Marc Levoy, Ren Ng, Andrew Adams • Adobe – Todor Georgiev, • MERL – Ashok Veeraraghavan, Amit Agrawal MIT Media Lab Light Fields___ Camera Culture Ramesh Raskar MIT Media Lab http:// CameraCulture . info/ Light Fields in Ray and Wave Optics Introduction to Light Fields: Ramesh Raskar Wigner Distribution Function to explain Light Fields: Zhengyun Zhang Augmenting LF to explain Wigner Distribution Function: Se Baek Oh Q&A Break Light Fields with Coherent Light: Anthony Accardi New Opportunities and Applications: Raskar and Oh Q&A: All