Electro-optic tunable optical filter

An optical filter comprising:

• first and second polarizers spaced from one another along a predetermined path and having their respective pass directions for polarized light oriented at a desired angular relationship with respect to one another;
• a birefringent crystalline medium disposed along said path between said first and second polarizers and oriented with its optic axis perpendicular to said path, said medium having at least one non-zero electro-optic coefficient selected from the group consisting of the coefficients r.sub.41, r.sub.42, r.sub.43, r.sub.51, r.sub.52, r.sub.53, r.sub.61, r.sub.62 and r.sub.63 ;
• means for directing a beam of light including a plurality of wavelengths through said first polarizer and said medium along said path;
• and
• means for applying to successive regions of said medium along said path a dc electric field which is spatially varying along said path to electro-optically produce in said medium an effective variation of the optic axis thereof about the pass direction of said first polarizer in a plane perpendicular to said path as a function of distance along said path with a predetermined spatial variation such that at least one of said wavelengths in said beam is passed by said second polarizer and at least another of said wavelengths is rejected by said second polarizer.