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Micro Phase Shifting 2014-07-01 Se-Hoon, Park -Mohit Gupta and Shree K. Nayar, CVPR2012
2 Real-Time Compressive Tracking Contents Phase shifting Phase shift encoding Phase shift decoding Issue Inter reflection Micro Phase shifting Disambiguation experiments
Phase shifting Phase shift encoding Three image structured light I1(x,y) = I’(x,y) + I’’(x,y)cos[θ(x,y) - 2π/3] I2(x,y) = I’(x,y) + I’’(x,y)cos[θ(x,y)] I3(x,y) = I’(x,y) + I’’(x,y)cos[θ(x,y) + 2π/3] I1(x,y) : first imageI2(x,y) : seond imageI3(x,y) : third image I’(x,y) : average intensityI’’(x,y) : intensity modulationθ(x,y) : phase
Phase shifting Phase shift encoding Ex) I’(x,y) = 125 I’’(x,y) = 125 I1(x,y) = I’(x,y) + I’’(x,y)cos[θ(x,y) - 2π/3] I2(x,y) = I’(x,y) + I’’(x,y)cos[θ(x,y)] I3(x,y) = I’(x,y) + I’’(x,y)cos[θ(x,y) + 2π/3] θ(x,y)I1(x,y)I2(x,y)I3(x,y) π/6 12523316 π/3 187 0 π/2 23312516 2π/3 25062 5π/6 23316125 π 1870
Phase shift encoding Phase shifting 55 I1I2I3
Phase shifting I1(x,y)I2(x,y)I3(x,y)θ(x,y) 12523316 π/6 187 0 π/3 23312516 π/2 25062 2π/3 23316125 5π/6 1870 π
Phase shifting Phase shift decoding Camera image Projector image
Phase shift decoding –If the noise is same in the three camera images, noise doesn’t matter. Phase shifting 8
9 pixel pixel θ (π) θ (π) Input phase output phase ambiguous I1(x,y) = I’(x,y) + I’’(x,y)cos[θ(x,y) - 2π/3] I2(x,y) = I’(x,y) + I’’(x,y)cos[θ(x,y)] I3(x,y) = I’(x,y) + I’’(x,y)cos[θ(x,y) + 2π/3] Input phase Output phase
Phase shifting 10 frequency ( ) amplitude Broad Frequency Band max mean min Unambiguous but Noisy Accurate but Ambiguous
Inter reflection Issue 11 camera projector Inter reflections P Q R time Inter reflections Direct Radiance radiance scene
Inter reflection Issue 12 camera projector Inter reflections P Q R time Inter reflections Direct Radiance radiance scene Phase Error
Inter reflection Issue 13 camera projector Inter reflections P Q R scene Inter reflection Illumination pattern light transport coefficients
Inter reflection Issue 14 camera projector Inter reflections P Q R scene Inter reflection Illumination pattern light transport coefficients
Inter reflection Issue 15 camera projector Inter reflections P Q R scene Inter reflection Illumination pattern light transport coefficients
Inter reflection Issue 16 camera projector Inter reflections P Q R scene Inter reflection Illumination pattern light transport coefficients N
Inter reflection Issue 17 Inter reflection * illumination patternlight transport coefficients pixels
Inter reflection Issue 18 frequency projected patterns Inter reflection illumination patternlight transport coefficients
Inter reflection Issue 19 frequency projected patterns Inter reflection illumination patternlight transport coefficients Micro phase shifting
Micro Phase shifting 20 max mean min frequency ( ) amplitude How Can We Disambiguate Phase Without Low Frequency Patterns?
Micro Phase shifting 21 number of periods (unknown) Phase disambiguation
Micro Phase shifting 22 unknownknownunknownknownunknownknown
Micro Phase shifting 23
Micro Phase shifting 24 Experiments –Ceramic bowl
Micro Phase shifting 25 Experiments –Ceramic bowl point projector
Micro Phase shifting 26 Experiments –Ceramic bowl Conventional Phase Shifting Micro Phase Shifting [Our]
Micro Phase shifting 27 Experiments –Lemon point projector subsurface scacttering
Experiments –Lemon Micro Phase shifting 28 Conventional Phase Sh ifting Micro Phase Shifting [Our]
Experiments –Shiny Metal Bowl Micro Phase shifting 29
Experiments –Shiny Metal Bowl Micro Phase shifting 30 Conventional Phase Shi fting Micro Phase Shifting [Our]
Micro Phase Shifting Mohit Gupta and Shree K. Nayar Computer Science Columbia University Supported by: NSF and ONR.
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