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

2. Head/Helmet Mounted Display (HMD)
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

3. HMDs
eMagin 3D Visor HMD
VSI F-35 HMDS

4. Pupil Forming vs Non Pupil Forming
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

5. Non Pupil Forming Performance Parameters
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

6. Field of View
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

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

8. 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

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

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

11. Eye Box
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.