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 and including a second portion configured to provide a second calibration image; and a controller configured to control 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 alignment of the first image and the second image.