Moving refractive optical low pass filter (ROLPF) for digital cameras

As with any sampling process, image acquisition is subject to spatial domain aliasing. Many designs of optical filters have been proposed that reduce the amount of aliasing in image acquisition. Still, the most common systems are based on birefringent optical materials. Unfortunately, these filters are expensive and the actual filter response curve can only partially be influenced. We propose a new refractive optical low-pass filter (ROLPF) based on refraction at a structured glass plate. The transparent plate features a single surface with a defined structure. This leads to refraction and will lead to a modified light distribution on the sensor. The plate is placed in front of the sensor and is moved in the image sensor plane during an exposure. This causes an averaging process and results in a spatial domain filtering. The response curve of this setup can be controlled by designing the gradient of the surface. This filter will be easy to manufacture, it offers a true low-pass characteristic which can be specifically designed and the bandwidth can be adjusted at runtime by variation of the distance to the sensor.