Measurements of the performance of the light mixing chambers in the mixel camera

Spectral data acquired with traditional push-broom hyperspectral cameras may be significantly distorted due to spatial misregistration such as keystone. The mixel camera is a new type of push-broom hyperspectral camera, where an image recorded with arbitrary (even large) keystone is reconstructed to a nearly keystone-free image. The key component of the mixel camera is an array of light mixing chambers in the slit plane, and the precision of the image reconstruction depends on the light mixing properties of these chambers. In this work we describe how these properties were measured in a mixel camera prototype. We also investigate the potential performance of the mixel camera in terms of spatial co-registration, based on the measured response of the mixing chambers to a point source. The results suggest that, with the current chambers, a perfectly characterized mixel camera should have residual spatial misregistration that is equivalent to 0.02-0.03 pixels keystone. This compares favorably to high resolution instruments where keystone is corrected in hardware or by resampling.