Patent ID: 7492948

Claim:
A phase contrast system for synthesizing an intensity pattern I(x′, y′), comprising a source of electromagnetic fields for emission of at least two substantially plane electromagnetic fields with different axes of propagation, a phase modifying element for phase modulation of the electromagnetic fields by phasor values e iφ(x,y) and positioned so that the at least two electromagnetic fields are incident upon it at different respective angles of approach, first Fourier or Fresnel optics for Fourier or Fresnel transforming the phase modulated electromagnetic fields positioned in the propagation paths of the at least two phase modulated fields, a spatial phase filter with at least two phase shifting regions positioned at respective zero-order diffraction regions of the at least two respective phase modulated electromagnetic fields for individually phase shifting the at least two respective Fourier or Fresnel transformed electromagnetic fields by predetermined respective phase shift values θ n in relation to the remaining part of the at least two respective transformed electromagnetic fields, and second Fourier or Fresnel optics for forming the intensity pattern I(x′, y′) by Fourier or Fresnel transforming the at least two respective phase shifted Fourier or Fresnel transformed electromagnetic fields, characterized in that the phasor values e iφ(x,y) of the phase modifying element and the phase shift values θ n substantially fulfilling that I ⁡ ( x ′ , y ′ ) ≅ ∑ n ⁢ S ⁡ ( n ) ⁢ A 2 ⁢  exp ⁡ ( ⅈ ⁢ ϕ ~ ⁡ ( x ′ , y ′ ) ) + K n ⁢  α _  ⁢ ( B n ⁢ A - 1 ⁢ exp ⁡ ( ⅈθ n ) - 1 )  2 for selected phase shift values θ n , wherein A is an optional amplitude modulation of the spatial phase filter outside the zero-order diffraction regions, B n is an optional amplitude modulation of the spatial phase filter in the respective n'th zero-order diffraction region, α =| α |exp(iφ α ) is the average of the phasors e iφ(x,y) of the resolution elements of the phase modifying element, and {tilde over (φ)}=φ−φ α , and S(n) is the intensity of the n'th electromagnetic field, and K n =1−J 0 (1.22πη n ), wherein J 0 is the zero-order Bessel function, and η n relates the radius R 1n of the n'th zero-order filtering region to the radius R 2 of the main-lobe of the Airy function of the input aperture, η n =R 1n /R 2 , except when the phase modifying element has fixed phasor values e iφ(x,y) and 1) θ n = π 2 and the phase shifting area of the phase filter is annular, or, 2) θ n =π and the phase filter is divided into a plurality of rows, every second row having phasor value e iπ and being interlaced with the remaining rows having the phasor value e i0 .