Micro Phase Shifting 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/ π/ π/ π/ π/ π 1870

 Phase shift encoding Phase shifting 55 I1I2I3

Phase shifting I1(x,y)I2(x,y)I3(x,y)θ(x,y) π/ π/ π/ π/ π/ 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]