Patent ID: 7232217

Claim:
A lens unit comprised of: A) a first lens having two surfaces providing a varying lens thickness as a function of position across the lens surfaces and B) a second lens having two surfaces providing a varying lens thickness as a function of position across the lens surfaces that is substantially complementary to the varying thickness of the first lens; wherein the designs of the thicknesses are chosen such that small adjustments of the relative positions of the two lenses in a first direction predominantly perpendicular to the viewing direction results in changes in the combined focus of the two lenses of each lens unit; and wherein the thicknesses are designed substantially in accordance with the following procedure: A) provide a lens thickness of the first lens to be f_lens 1 (X,Y)=C*(X 3 /3+XY 2 )+t 0 +(any polynomial of degree <3), where C and t 0 are constants, B) provide a lens thickness of the second lens to be f_lens 2 (X,Y)=−C*(X 3 /3+XY 2 )+t 0 +(the complementary polynomial), C) move the lenses with respect to each other in X and Y, to provide a net thickness of both lenses of: f_lens 1 (X+dx,Y+dy)+f_lens 2 (X−dx,Y−dy) which evaluates to [2*C*dx*(X 2 +Y 2 )]+[2*C*dy*(2XY)]+[(⅔)*C*dx*(dx 2 +3dy 2 )+2t 0 ]+(a polynomial of degree <2); wherein, the first bracketed term, proportional to dx, is the focus, the second bracketed term, proportional to dy, is astigmatism in a certain direction, and the third and fourth terms are just net thickness and wedge, which do not effect visual acuity.