1. An apparatus comprising: a first expander configured to provide a first image and including a first portion configured to provide a first calibration image; a second expander configured to provide a second image that includes substantially the same content as the first image and is distinct from the first image, the second expander including a second portion configured to provide a second calibration image; and a controller configured to control an alignment of the first image and the second image, a combination of the first calibration image and the second calibration image being useable to control the alignment of the first image and the second image.