Tilted cat helmet-mounted display

A new 50° x 60° field of view helmet-mounted display (HMD) with a tilted catadioptric combiner has been designed, fabricated, and tested. The tilted cat display concept allows a wide-FOV display to be designed that has a 3:1 display brightness improvement over the conventional folded catadioptric approach, provides a similar improvement in combiner seethrough transmissions, and requires only a small tilt on the optically powered combiner that minimizes the complexity of the optics. Large-FOV HMDs with see-through capability require tilted, optically powered surfaces with complex optical systems for the display projection and relay. The optical performance of a tilted, optically powered element becomes more asymmetric as the tilt increases, and to maintain a resultant wellresolved symmetric display image, additional nonsymmetric, tilted, decentered lens elements are required. The tilted cat combiner permits a practical display optical system to be defined for a 60° FOV. The highresolution performance levels of the smaller FOV displays were obtained, with the resolution limited only by the CRT's resolution. A summary of the design considerations, development process, and demonstrated performance data for the 60° tilted cat HMD are presented.