Dimensioning of optical birefringent anti-alias filters for digital cameras

A digital camera samples the continuous real world. As with any sampling process, questions of aliasing for certain sampling frequencies and the prevention thereof arise. In this paper we will discuss the spatial domain sampling and prevention of aliasing in digital cameras. We focus on the widely used birefringent anti alias filters that are often called optical low pass filters (OLPF). We show 2D models for all contributions to spatial domain sampling and derive optimum filter parameters for minimum aliasing and best possible image sharpness. Compared to previously used selection rules, we can show that the optimum selection of filter parameters can easily deliver more sharpness and reduce aliasing by a factor of 2. The simulated results are finally confirmed in real world experiments.