Helmet Mounted Displays (HMDs) and Head Up Displays (HUDs) have been used extensively over the past decades especially within the defense sector. The complexity of the design and the fabrication of high quality see-through combiner optics to achieve high resolution over a large FOV have hindered their use in consumer electronic devices. Occlusion Head Mounted Displays (HMD) have also been used in the defense sector for simulation and training purposes, over similar large FOV, packed with custom head tracking and eye gesture sensors.
Recently, a paradigm shift to consumer electronics has occurred as part of the wider wearable computing effort. Technologies developed for the smart phone industry have been used to build smaller, lower power, cheaper, electronics. Similarly, novel integrated sensors and micro-displays have enabled the development of consumer electronic smart glasses and smart eyewear, professional AR (Augmented Reality) HMDs as well as VR (Virtual Reality) headsets.
Reducing the FOV while addressing the needs for an increased exit pupil (thus allowing their use by most people) alongside stringent industrial design constrains have been pushing the limits of the design techniques and technologies available to the optical engineer (refractive, catadioptric, micro-optic, segmented Fresnel, waveguide, diffractive, holographic, …).
The integration of the optical combiner within conventional meniscus prescription lenses is a challenge that has yet to be solved. We will review how a broad range of optical design techniques have been applied to fulfill such requirements, as well as the various head-worn devices developed to date. Finally, we will review additional optical technologies applied as input mechanisms (eye and head gesture sensing, gaze tracking and hand gesture sensing).