Anti-aliasing low-pass blur filter for reducing artifacts in imaging apparatus

Abstract

An imaging apparatus for generating an image signal from incident image light having its higher spatial frequencies limited to reduce undersampling artifacts includes an image sensor for generating the image signal from an array of photosites, and an optical section having a biaxial crystal optical filter interposed in the path of the incident image light so as to output a blurred image upon said photosites. The optical filter has two optical axes along which light can propagate and experience the same index of refraction for any polarization. The optical filter has parallel input and output surfaces; and one of the two optical axes is perpendicular to the input and output surfaces. The optical filter has "X", "Y", and "Z" axes; and the "Z" axis bisects the two optical axes. Preferably, the "Z" axis and the optical axes define the angle .THETA. such that: tan .THETA.=(N.sub.z /N.sub.x)SQRT›(N.sub.y.sup.2 -N.sub.x.sup.2)/(N.sub.z.sup.2 -N.sub.y.sup.2)!. The optical filter has three indices of refraction, N.sub.x, N.sub.y, and N.sub.z. As an example, N.sub.x =1,779, N.sub.y =1,789, and N.sub.z =1.887 for an optical wavelength of 532 nm.

Dependencies are inferred from the claim text.