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Micro Phase Shifting 2014-07-01 Se-Hoon, Park -Mohit Gupta and Shree K. Nayar, CVPR2012

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2 Real-Time Compressive Tracking Contents Phase shifting Phase shift encoding Phase shift decoding Issue Inter reflection Micro Phase shifting Disambiguation experiments

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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

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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

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Phase shift encoding Phase shifting 55 I1I2I3

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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

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Phase shifting Phase shift decoding Camera image Projector image

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Phase shift decoding –If the noise is same in the three camera images, noise doesn’t matter. Phase shifting 8

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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

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Phase shifting 10 frequency ( ) amplitude Broad Frequency Band max mean min Unambiguous but Noisy Accurate but Ambiguous

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Inter reflection Issue 11 camera projector Inter reflections P Q R time Inter reflections Direct Radiance radiance scene

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Inter reflection Issue 12 camera projector Inter reflections P Q R time Inter reflections Direct Radiance radiance scene Phase Error

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Inter reflection Issue 13 camera projector Inter reflections P Q R scene Inter reflection Illumination pattern light transport coefficients

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Inter reflection Issue 14 camera projector Inter reflections P Q R scene Inter reflection Illumination pattern light transport coefficients

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Inter reflection Issue 15 camera projector Inter reflections P Q R scene Inter reflection Illumination pattern light transport coefficients

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Inter reflection Issue 16 camera projector Inter reflections P Q R scene Inter reflection Illumination pattern light transport coefficients N

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Inter reflection Issue 17 Inter reflection * illumination patternlight transport coefficients pixels

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Inter reflection Issue 18 frequency projected patterns Inter reflection illumination patternlight transport coefficients

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Inter reflection Issue 19 frequency projected patterns Inter reflection illumination patternlight transport coefficients Micro phase shifting

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Micro Phase shifting 20 max mean min frequency ( ) amplitude How Can We Disambiguate Phase Without Low Frequency Patterns?

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Micro Phase shifting 21 number of periods (unknown) Phase disambiguation

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Micro Phase shifting 22 unknownknownunknownknownunknownknown

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Micro Phase shifting 23

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Micro Phase shifting 24 Experiments –Ceramic bowl

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Micro Phase shifting 25 Experiments –Ceramic bowl point projector

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Micro Phase shifting 26 Experiments –Ceramic bowl Conventional Phase Shifting Micro Phase Shifting [Our]

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Micro Phase shifting 27 Experiments –Lemon point projector subsurface scacttering

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Experiments –Lemon Micro Phase shifting 28 Conventional Phase Sh ifting Micro Phase Shifting [Our]

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Experiments –Shiny Metal Bowl Micro Phase shifting 29

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Experiments –Shiny Metal Bowl Micro Phase shifting 30 Conventional Phase Shi fting Micro Phase Shifting [Our]

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