Patent ID: 8203788

Claim:
An electromagnetic beam converter for conversion of an input beam of electromagnetic radiation a(x,y) into an output beam having a prescribed target intensity profile I(x′,y′), the beam converter comprising a generalized phase contrast system with a phase modifying element positioned for illumination by the input beam a(x,y) and for phase modulation of the input electromagnetic beam by phasor values e iφ(x,y) thereby forming phase modulated radiation a(x,y) e iφ(x,y) , first Fourier or Fresnel optics positioned in the propagation path of the phase modulated radiation for Fourier or Fresnel transforming the phase modulated electromagnetic radiation a(x,y) e iφ(x,y) , a spatial filter for filtering the Fourier or Fresnel transformed electromagnetic field by in a region of spatial frequencies comprising DC in the Fourier or Fresnel plane phase shifting with a predetermined phase shift value θ the modulated electromagnetic field in relation to the remaining part of the electromagnetic field, and multiplying the amplitude of the modulated electromagnetic field with a constant B, and in a region of remaining spatial frequencies in the Fourier or Fresnel plane, multiplying the amplitude of the modulated electromagnetic field with a constant A, and second Fourier or Fresnel optics for forming an output electromagnetic field with the prescribed intensity profile I(x′, y′) by Fourier or Fresnel transforming the phase shifted Fourier or Fresnel transformed electromagnetic field, wherein the input beam has a Gaussian intensity profile a ( x,y )= a ( r )=exp[−r 2 /w 0 2 ] wherein w 0 is the beam waist, and r is the distance from the centre of the beam, and wherein the phasor values e iφ(x,y) and the phase shift value θ are calculated in accordance with the equations: α _ ⁡ [ exp ⁡ ( i ⁢ ⁢ θ ) - 1 ] = - 1 , ⁢ θ = 2 ⁢ cot - 1 ⁡ ( 2 ⁢ α _ imaginary ) = 2 ⁢ cot - 1 ⁡ [ 2 ⁢ ∫ a ⁡ ( x , y ) ⁢ sin ⁡ [ ϕ ⁡ ( x , y ) ] ⁢ ⅆ x ⁢ ⅆ y ∫ a ⁡ ( x , y ) ⁢ ⅆ x ⁢ ⅆ y ] , cos ⁡ [ ϕ ⁡ ( r ′ ) ] = 1 - I 0 2 ⁢ exp ⁡ ( 2 ⁢ r ′2 / w 0 2 ) ⁢ I ⁡ ( x ′ , y ′ ) wherein I 0 is the target uniform intensity to be determined based on energy conservation.