Metasurface-based structured light 3D imaging system and method

A metasurface-based structured light 3D imaging system, being arranged above a target object (003) and at least comprising a metasurface-based structured light projector (002) and a camera system (001) for acquiring a structured light, wherein:

• the structured light projector (002) comprises a semiconductor laser (101) used as a light source, and a beam homogenizer (102), a condenser (103), a cylindrical mirror (104) and a MEMS micromirror (105) are sequentially arranged in front of the semiconductor laser (101) in an incident direction;
• the camera system (001) at least comprises a photosensitive unit and an optical system, forms a complete imaging unit, and synchronously acquires a structured light pattern (106) projected to a surface of the target object (003);
• the semiconductor laser (101) is either a multi-mode edge-emitting laser EEL or a vertical-cavity surface-emitting laser array VCSELs;
• a laser beam (301) generated by the multi-mode edge-emitting laser EEL or the vertical-cavity surface-emitting laser array VCSELs first penetrates through the beam homogenizer (102), the beam homogenizer a reciprocating tangential translatory motion slightly or rotates around an axial slightly, wherein a motion amplitude ranges from 1 μm to 1000 μm, and a motion frequency ranges from 50 Hz to 5000 Hz;
• nano-micro structures are arranged on a surface of the beam homogenizer (102) to change a phase and vibration direction of light waves, and after the light waves penetrate through the beam homogenizer (102), energy is homogenized, and the vibration direction becomes random, such that coherence is destroyed;
• laser lights enter the condenser (103) after passing through the beam homogenizer (102), and the condenser (103) converges and shapes the laser lights into a Gaussian beam by means of nano micro-structures on a surface of the condenser (103);
• after being stretched by the cylindrical mirror (104), the Gaussian laser beam forms a uniform laser knife structure, that is, the laser beam is linearly distributed in an x-y plane;
• the laser beam enters the MEMS micromirror (105) and is then further reflected to the surface of the measured target object (003), the MEMS micromirror (105) is driven to make simple harmonic motions around an axis to drive laser lights to scan the surface of the object, the brightness of the laser is adjusted synchronously, and the structured light pattern (106) coded in one dimension and distributed in two dimension is projected to the surface of the target object (003);
• the phase of the light waves of the condenser (103) needs to follow the following phase distribution φnf(x,y) to converge the laser lights into a Gaussian laser beam, and the phase distribution required for forming the Gaussian laser beam is:
• φ
• n
• ⁢
• f
• (
• x
• ,
• y
• )
• =
• 2
• ⁢
• π
• λ
• ⁢
• (
• f
• -
• x
• 2
• +
• y
• 2
• +
• f
• 2
• )
• where, φnf(x,y) is a phase distribution of the Gaussian laser beam, λ is a wavelength of an incident light, and f is a focal length, x and y are positional coordinates of a cross-section of the laser beam;
• a distribution of the nano-units is designed to realize the phase distribution φnf(x,y) to converge the laser lights into the Gaussian laser beam;
• a mathematical model of a propagation model of the Gaussian laser beam is:
• w
• ⁡
• (
• z
• )
• =
• w
• 0
• ⁢
• 1
• +
• (
• M
• 2
• ⁢
• (
• z
• -
• z
• 0
• )
• ⁢
• λ
• π
• ⁢
• w
• 0
• 2
• )
• ,
• M
• 2
• ≥
• 1
• where, the beam propagates in a z direction, w0 is a diameter of a beam waist, a z value of the beam waist is z0, M2 is a parameter related to the laser beam, and for a desired Gaussian laser beam, M2=1, λ is a wavelength of the light waves, and w(z) is the Gaussian laser beam.