  We investigated the role of HUDs in CAI. HUDs have been used in various
situations in daily lives by recent downsizing and cost down of the display
devices. CAI is one of the promising applications for HUDs. We have developed
an HUD-based CAI system for effectively presenting instructions of the
equipment in the transportable earth station. This chapter described HUDs in
CAI from a viewpoint of human-computer interaction based on the development
experience.
