1. 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, 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.