Patent ID: 11906286
Assignee: NANJING UNIVERSITY OF SCIENCE AND TECHNOLOGY
Field: Computer technology (Electrical engineering)
Classification: CPC G | IPC G

Claim 1:
2. According to claim 1, a deep learning-based temporal phase unwrapping method for fringe projection profilometry is characterized by step one wherein four sets of three- step phase-shifting fringe patterns with different frequencies are projected to the tested objects;
each set of patterns contains three fringe patterns with the same frequency and different initial phase; any set of three-step phase-shifting fringe patterns projected by a projector is represented as:

I1p(xp, yp)=128+127 cos[2πf xp/W]

I2p(xp, yp)=128+127 cos[2πf xp/W+27π/3]

I3p(xp, yp)=128+127 cos[2πf xp/W+4π/3], where I1p(xp, yp), I2p(xp, yp), I3p(xp, yp) are three-step phase-shifiing, fringe patterns projected by the projector; (xp, yp) is a pixel coordinate of the projector; W is a horizontal resolution of the projector; f is a frequency of phase-shifting fringe patterns; a DLP projector is used to project four sets of three-step phase-shifting fringe patterns onto the tested objects; the frequencies of four sets of three-step phase-shifting fringe patterns are 1, 8, 32, and 64, respectively; each set of three fringe patterns has the same frequency; the projected fringe patterns are captured by the camera simultaneously; the acquired three-step phase-shifting fringe images are represented as:

I1(x, y)=A(x, y)+B(x, y)cos[Φ(x, y)]

I2(x, y)=A(x, y)+B(x, y)cos[Φ(x, y)+2π/3]

I3(x, y)=A(x, y)+B(x, y)cos[Φ(x, y)+4π/3], where I1(x, y), I2 (x, y), I3 (x, y) are three-step phase-shifting fringe images; (x, y) is a pixel coordinate of the camera; A(x, y) is an average intensity; B (x, y) is an intensity modulation; Φ(x, y) is a phase distribution the tested objects.