Complex photodichroic spatial filter

Claim 1

A complex spatial filter for reversibly recording a filter function F(x,y) having a real component F r (x,y) and an imaginary component F i (x,y) and contained in the information in a beam of coherent light energy comprising: a first linear polarizer positioned to receive said beam of coherent light for transmitting only its light energy components of predetermined polarization; a first dichroic crystal plate positioned contiguous and parallel to said first linear polarizer and responsive to the absorption of light energy of a known first bandwidth and a first determinable polarization of said beam of coherent light for causing a difference in the fraction of its M-centers oriented along the [110] and [110] directions at each point (x,y) defined by f.sub.1 (x,y) - f.sub.2 (x,y) = (1/2k) a quarter waveplate element positioned contiguous and parallel to said first dichroic crystal plate for causing a 90° phase change between the two orthogonally polarized components of coherent light energy emerging from said first dichroic crystal plate; a second dichroic crystal plate positioned contiguous and parallel to said quarter waveplate element and responsive to the absorption of light energy of said known first bandwidth and a second determinable polarization of said beam of coherent light for causing a difference in the fraction of its M-centers oriented along the [110] and [110] directions at each point (x,y) defined by f.sub.1 '(x,y) - f.sub.2 '(x,y) = (1/2k) where k is a real positive constant of proportionality, said first and second dichroic crystal plates having their principal polarization axes oriented at 45° relative to the principal polarization axis of said quarter waveplate element; a second linear polarizer positioned contiguous and parallel to said second dichroic crystal plate for transmitting light energy components orthogonally polarized relative to said components of predetermined polarization; and a source of light energy of said known first bandwidth and non-polarized state disposed to irradiate said first and second dichroic crystal plates for restoring their M-centers to substantially random orientation.