For small camera modules in consumer applications, such as mobile phones or webcams, size and cost are
important constraints. An autofocus system increases both size and cost and can degrade optical performance
by misalignment. Therefore, a monolithic optical system with a fixed focus is preferable for these applications.
On the other hand, the optical system of the camera has to exhibit a very large depth of field, as it is expected
to deliver sharp images for all typical working distances. The depth of field of a camera system can be increased
by using a larger F-number, but this is undesirable due to light sensitivity considerations. On the other hand, it
can also be increased by reducing focal length.
Multi-aperture systems use multiple optical channels, each of them with a smaller focal length than a comparable
single-aperture system. Accordingly, each of the channels has a large depth of field. However, as the
channels are displaced laterally, parallax becomes noticeable for close objects. Therefore, the channel images
have to be shifted accordingly when recombining them into a complete image.
We demonstrate an algorithm that compensates for parallax as well as chromatic aberration and geometric
distortion. We present a very flat camera system without moving parts that is capable of taking photos and
video at a wide range of distances. On the demonstration system, object distance can be adjusted in real time
from 4 mm to infinity. The focus position can be selected during capture or after the images were taken.