1. Design Considerations and Preliminary Evaluation for an off-the-visor wide field of view HMD Russell S. Draper, Charles D. Balogh Night vision Electronic Sensors Directorate Steven J. Robbins Kaiser Electronics, San Jose, CA

2. Introduction Purpose –Performance evaluation of a prototype binocular, WFOV, “off-visor” HMD –Army’s interest in a “Jet Fighter” HMD? Directed development for Objective Force Warrior –Multi-spectral head worn sensor system –Possible form: binocular/see through vision system Maintain expertise in “state-of-the-art” HMD technology

3. Introduction Purpose –Test key performance attributes FOV Resolution –Test key ergonomic attributes Eye box Binocular alignment/stability Head borne weight/CG

4. Introduction Test Methods –NVESD Near Eye Display Test Station employed for all tests except system weight and CG –Weight/CG CG determined by analysis

5. WFOV HMD Goals Risk mitigation effort –Binocular+off-visor Stability/alignment Profile –4.1 lb+Binocular Stability/alignment –Eye relief+FOV Profile/CG Platform demo of emerging technology –LCD vs. CRT

6. System Evaluation Description –Display unit (DU) Binocular optical support structure (BOSS) Relay optics assemblies Visor/combiner –Helmet unit (HU) –Electronics Unit (EU) Display unit Helmet unit

7. System Evaluation Description- Display unit Visor/combiner BOSS Relay optic assembly(right)

8. System Evaluation Description- Helmet unit Helmet shell Retention/retraction LCD cables Interface PCB Suspension fit latches Main cable

9. System Evaluation Performance test results: FOV –Methods Display active area driven to full “on” condition Digital image frame captured with NEDTS WFOV CCD array sensor Unique edge detection algorithm applied to captured image –Edge detection starts at center and propagates outward Edge pixel values converted to angle space using NEDTS WFOV lens mapping. Test performed on right and left channels, 3 IPD settings each with sensor located at IPD setting design eye position.

10. System Evaluation Performance test results –FOV

11. System Evaluation Performance test results –FOV Inscribed rectangular areas

12. System Evaluation Performance test results: Resolution –Methods Maximum contrast measured with NEDTS PMT sensor. Display active area driven with 50% duty cycle square wave grid at Nyquist sample rate, ½, ¼, 1/8 Nyquist rate Digital image frame captured with NEDTS NFOV CCD array sensor Localized distortion correction (3 rd order warping horizontal or vertical) applied to captured image. Row/column averaging performed. Average cycle Michelson contrast computed for all viewable cycles.

13. System Evaluation Performance test results: Resolution –Methods Raw data:Distortion correction applied:

14. System Evaluation Performance test results: Resolution Right channelLeft channel

15. System Evaluation Performance test results: Eye box –Methods 2D scan of eye left and right side design eye location +/-12 mm vertical and +/-15 mm horizontal 3 parameters measured at each scan position –Luminance –On/off contrast –Nyquist rate contrast Plotted 50% contour of normalized data

16. System Evaluation Performance test results: Eye box Units in mm LuminanceDC contrastNyquist contrast

17. System Evaluation Performance test results: Alignment/Stablity –Methods Visor removal/replacement –Single 5 mr spot at approximately 0,0 field position displayed in each channel –Visor removed and replaced 20 times –Field location of test spot measured with each trial –Relative change between right and left channels recorded.

18. System Evaluation Performance test results: Alignment/Stablity –Methods IPD adjustment –Single 5 mr spot at approximately 0,0 field position displayed in each channel –IPD adjusted on single channel through all three settings for 10 trials –Field location of test spot measured with each trial for each channel –Relative change between right and left channel recorded

19. System Evaluation Performance test results: Alignment/Stablity –Methods Eye position shift –2-D Grid of 5 mr points displayed at approximately 4° increments –Sensor position moved in eye box from design eye location at nominal IPD +/- 2 mm horizontally and vertically –Field location of test spot measured with each trial for each channel –Relative change between right and left channel for corresponding spots within the binocular overlap region recorded

20. System Evaluation Performance test results: Alignment/Stablity –Methods Visor See through deviation –Collimated “plus” symbol generated with bright line theodolite outside of visor at specific field angle relative to DU. –NEDTS sensor with digital cross hair oriented to view collimated image until digital cross hair overlaped “plus” symbol –Visor removed –Theodolite adjusted to re-position “plus” symbol on cross hair –Theodolite change in azimuth/elevation recorded

21. System Evaluation Performance test results: Alignment/Stablity

22. System Evaluation Performance test results: Weight/CG –Methods Shell, fit system, electronics,1 ft. cable weighed Display unit weighed with visor and relay optics Visor weighed separately Right channel relay optics weighed separately Total head borne weight computed from actual component weights CG estimated from CAD data and actual component weights.

23. System Evaluation Performance test results: Weight/CG

24. Conclusions WFOV prototype HMD incorporates several innovative design elements –Flexible optical mounts for durability –3-point visor interface for improved visor positional repeatablity –Bifurcated v-shaped visor for narrow profile and visor stability –Integrated small footprint binocular optical support for stability –3 position IPD adjustment with kinematic interface

25. Conclusions WFOV promising performance attributes: –FOV >40° horizontal and 30° vertical for binocular viewing with approximately 30° overlap –Resolution nominally 0.75 cy/mr (currently display source limited) –Stability of binocular alignment better than 0.75 mr RMS and 2.5 mr worst case.

26. Conclusions WFOV performance concerns: –Notable FOV vignetting occurs for narrow IPDs –IPD adjustment mechanism has no apparent effect on eye box position. –Notable resolution loss over small area of design eye box –Visor bifurcation causes small amount of image doubling at joint