Polarimetric phase imaging

A method for generating data related at least to the polarization state and the polarization rate, and advantageously to the wavefront shapes, of an incident light beam of any polarization state and any polarization rate,

• from a single intensity image acquisition Isensor of said light beam,
• using a polarization and wavefront shape imaging system which comprises a polarization modulating mask and an intensity sensor camera:
• the polarization modulating mask being a diffractive optical element comprising a two-dimensional birefringent diffraction grating consisting in a two-dimensional periodic lattice having any structure of any of the five possible two-dimensional Bravais lattices:
• oblique lattice, square lattice, rectangular lattice, hexagonal lattice or rhombic lattice,
• the two-dimensional periodic lattice being periodic along two transverse dimensions with at least one transverse period w and based on an unit cell (210), each unit cell exhibiting a two-dimensional birefringent motif-, advantageously with a unit cell being a square unit cell with the size of the side w, the polarization modulating mask being thinner than one tenth of the Rayleigh distance of the mask zR, with zR=πw2/λaverage, λaverage being the average wavelength of the incident light beam,
• said polarization modulating mask having:
• a polarization-resolved transmission or reflection matrix T,
• the property to generate interference patterns between any two cross-polarized impinging beams, at several planes transverse to the propagation axis, the several transverse planes lying at several working distances (d) from the input plane of said polarization modulating mask,
• the interference patterns so depending on the two respective amplitudes and the relative phase of said two cross-polarized impinging beams,
• the property to generate at least one set of four reference intensity patterns, at least at one working distance (d) from the input plane of the polarization modulating mask, when illuminated by four respective impinging reference light beams, said reference intensity patterns exhibiting structures of size equal to said transverse period w or smaller at said working distance (d),
• the working distance (d) being smaller than one tenth of wL/λaverage, with L the diagonal length of a captor of the intensity sensor camera and λaverage being the average wavelength of the incident light beam,
• the four impinging reference light beams having polarization states defining all together a tetrahedron of non-zero volume when represented on the polarization Poincaré sphere,
• each said set of four reference intensity patterns forming a Stokes parameters image basis, meaning that the auto-correlation matrix CL=(RiRjL,G of the corresponding four reference intensity patterns is invertible, Ri being the reference intensity pattern of polarization state i,
• the intensity sensor camera being placed downstream from said polarization modulating mask for recording the intensity image Isensor of the incident light beam, at least a part of which having been reflected by or transmitted through the polarization modulating mask, or alternatively at least a part of the incident light beam having interfered with another beam reflected by or transmitted through the polarization modulating mask,
• said intensity image Isensor lying at any of the several of said working distances (d) from the input plane of the polarization modulating mask,
• the method comprising:
• (A) having previously recorded one set of at least four reference intensity patterns (N1) with the intensity sensor camera of the imaging system, the reference intensity patterns being formed at one given of said working distances (d) from the input plane of the polarization modulating mask,
• each reference intensity pattern having been generated by a respective impinging reference light beam of known polarization rate and known polarization state, and advantageously of known wavefront shape,
• the polarization states of the impinging reference light beams defining all together a polyhedron of non-zero volume when represented on the polarization Poincaré sphere and reference intensity patterns defining a Stokes parameters image basis at the working distance (d),
• thus allowing the determination of the full polarization state of the impinging light beam,
• (B) recording the single intensity image Isensor of said incident light beam with the intensity camera sensor, the single intensity image being formed at the same given working distance (d) from the input plane of the polarization modulating mask,
• (C) processing the single intensity image Isensor based on the reference intensity patterns to generate the data related to the polarization state and the polarization rate, and advantageously to the wavefront shapes of the incident light beam.