Patent ID: 7924517
Filing Date: 2011-04-12
Classification: G02B

Abstract:
1. A spatial filter, comprising: multiple opaque regions and multiple transparent regions, each transparent region defined by adjacent ones of the opaque regions and the opaque regions having different diverging or converging ratios so that the distance between pairs of opaque regions alters as a function of a rotational angle of the spatial filter, said rotational angle defined with respect to a radial line extending from a central axis of rotation of the spatial filter; wherein: at least a first pair of opaque regions of the multiple opaque regions are much longer than a cross-sectional dimension of a light beam for impinging onto the spatial filter, an axial distance between the first pair of opaque regions constantly changes over an axial distance from the central axis of rotation of the spatial filter, a width of each opaque region of the first pair of opaque regions alters as a function of the rotational angle of the spatial filter, and the multiple opaque regions are shaped substantially as portions of different spirals, different ones of the spirals having different separation distances between successive spiral turnings.