EYE BOX Non Pupil forming HeadHelmet Mounted Displays

EYE BOX – Non Pupil forming Head/Helmet Mounted Displays Art Hastings Jr 12/11/2006

Head/Helmet Mounted Display (HMD) n n HMD is a device intended to present virtual image of a microdisplay to the user at comfortable viewing distance and magnification Applications: Military, Medical, Gaming

HMDs e. Magin 3 D Visor HMD VSI F-35 HMDS

Pupil Forming vs Non Pupil Forming n n Pupil Forming – real exit pupil formed where the design eye location is. Exit pupil can be measured as luminance profile Non Pupil Forming – no real exit pupil formed, must use performance parameters to determine the volume where the user’s eye must be palce

Non Pupil Forming Performance Parameters n n Field of View (FOV): the FOV viewable by the user at a given eye location Resolution: the Contrast Transfer Function (CTF) at a given eye location

Field of View n n The FOV the user can achieve at a given eye location limited by vignetting of off axis field angles This will be limited by the eye relief and the FOV of the system

FOV limitations n Eye must rotate to view off axis field angles n n Eye point of rotation located 10 mm behind pupil Will cause translation of pupil n As the eye translates out of Eye Box the user will move eye closer to the system (effectively decreasing the Eye Relief)

Eye Relief (ER) effect on viewable FOV Pupil placed at ER resulting in vignetting of off axis field angles (lose FOV at edges) Eye point of rotation placed at ER resulting in reduced clearance between user’s eye and the HMD, but vignetting minimized

Resolution: Contrast Transfer Fucntion (CTF) n CTF: measurement of contrast for a given spatial frequency square wave pattern Example of square wave pattern displayed by HMD

CTF will vary with pupil position n n Horizontal and Vertical CTF both measured as function of pupil position Cutoff at 50% of CTF at ideal pupil position

Eye Box n The eye box of the HMD is the volume where the user can place his pupil and achieve the full FOV for the system and see the full resolution of the system.