Resolution enhancement of large pixel PMD sensors

As every image sensor, PMD (Photonic Mixer Device) sensors are limited in their dimensions and thus the number of pixels is finite. Smaller pixel size means higher spatial resolution but also reduced photosensitivity. This is particularly noticeable for PMD cameras, because in dependence to the point of use the pixel size varies. Pixel dimensions for outdoor-use reaches a maximum, as they have to distinguish the inherent IR signal from the solar spectrum. Usually, the pixel size is reduced to increase spatial resolution of an image sensor. If this is not possible, spatial resolution can be increased at the expense of temporal resolution. One method is known as multiframe super-resolution. It superimposes multiple low-resolution images to get a high-resolution image. To ensure an increase of information density, the input images should be sub-pixel shifted relative to each other. This work describes a new approach to increase the information density in the amplitude image of a PMD camera. To ensure a sub-pixel accurate image overlay an opto-algorithmic problem is solved. The resolution enhancement is proved by measuring the Modulation Transfer Function of the in- and output images.