Patent ID: 7418202

Claim:
A blur filter, comprising: (a) a body having (i) first and second surfaces, and (ii) first and second in-plane axes that are orthogonal with respect to each other and a third axis that is mutually orthogonal to the first and second in-plane axes in a thickness direction of the body; and (b) a portion of the first surface being a structured surface having a variable pitch and a linear geometric feature, wherein the portion is structured such that, when the blur filter is placed within an optical path between a lens and an image sensor, the structured surface spreads a light signal in the optical path into a plurality of light signals being at least partially spatially separated when incident upon the image sensor, and wherein the body has birefringence and the birefringence is imparted by stretching the body after forming the linear geometric feature on the body, and wherein a cross sectional shape of the linear geometric feature after the stretching is substantially identical to a cross sectional shape of the linear geometric feature prior to the stretching.