Helmet-Mounted Display Design Guide Richard L. Newman and Kevin W. Greeley TR-97-11 3 November 1997 Crew Systems Post Office Box 963 San Marcos, Texas (512)-754-7733 REPORT DOCUMENTATION PAGE Form Approved OMB NO. 0704-0188 I -- Pu~licreporting burden for thls collection of lnformatlon IS estimated to average 1 hour per response~nclud~n~the tlme for reviewing instructions, searching exlstlna data sources 1 gather~noand malntalilnc? the data needed and Completlno and revlewlng the collection of informatlon Send comments reqardlnq thls burden estlmate or any othei aspect of this collect8on of informat~on.~nciud~n- suagestions for reducing tiiir burden to Washington Headquarters Services, Directorate Tor lnf6rmation Operations and Remns, 1215 Jefferson 1 Davis Hlohway, Su~te1204. Arlinat&, \j& 22202.43132, and to tn.0 Off~ceof Manaaem-nt and Budae?. Paoerwork Reduction Proiect. (0704-0188).. Washlnaton. DC 20503 1 1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DAT S COVERED 3 November 1997 Eontractor Report 1I 1I 14. TITLE AND SUBTITLE 5. FUNDING NUMBERS I Helmet-Mounted Display Design Guide I Contract NAS2-14151 Richard L. Newman and Kevin W. Greeley I I I 7. PERFORMING ORGANIZATION NAMEIS) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER 1 Crew Systems Post Office Box 963 San Marcos, Texas 78667 I 9. SPONSORINGIMONlTORlMG AGENCY NAME(S) AND ADDRESS(E5) 10. SPONSORING IMONIJORING AGENCY REPORT NUMBER Aeroflightdynamics Directorate I Ames Research Center Moffett Field, California 94035 11. SUPPLEMENTARY NOTES 12a. DISTRIBUTION I AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Unclassified-Unlimited I 13. AESTRACT (Maximum 200 words) 1 Helmet-mounted d~splays(HMDs) present flight, navigation, and weapon information in the pilot's line of sight. The HMD was developed to allow the pilot to retain aircraft and weapon information while looking off boresight. This document reviews current state-of-the-art in HMDs and presents a design guide fir the HMD engineer in identifying several critical HMD issues: symbol stabilization, inadequate definitions, undefined symbol drive laws, helmet considerations, and field-of-view (FOV) vs. resolution tradeoff requirements. In particular, display latency is a key issue for HMDs. In addition to requiring further experimental studies, it impacts the definition and control law issues. Symbol stabilization is also critical. In the case of the Apache helicopter, the lack of compensation for pilot head motion creates exces- sive workload during hovering and nap-of-the-earth (NOE flight. This translates into exces- sive training requirements. There is no agreed upon set ot' definitions or descriptions for how HMD symbols are driven to compensate for pilot head motion. A set of definitions is pro- posed to address this. There are several specific areas where simulation and flight experi- ments are needed: development of hover and NOE symbologies which com ensate for pilot head movement; display latency and sampling, and the tradeoff between F8 V, sensor reso- lution and symbology. 114. SUIJECT TERMS I Helmet-Mounted Displays(HMD); Flight Displays; Symbology; f Latency; Field-of-View (FOV); Resolution; Stabilization OF PEPORT OF THIS PAGE OF ABSTRACT IL P I NSlv 7'546-0: -280-5500 Standard Form 298 (Rev 2-89) Prescribed by ANSI Std 239.18 298 102 The helmet-mounted display (HMD) presents flight, navigation, and weapon information in the pilot's line of sight. The HMD was developed to allow the pilot to retain aircraft and weapon information while looking off boresight. This document reviews current state-of-the-art in HMDs and presents a design guide to assist the HMD engineer in identifying several critical HMD issues: symbol stabilization, inadequate definitions, undefined symbol drive laws, helmet considerations, and field- of-view (FOV) vs. resolution tradeoff requirements. In particular, display latency is a key issue for HMDs. In addition to requiring further experimental studies, it was found to impact the definition and control law issues. Symbol stabilization is critical. In the case of the Apache helicopter, the lack of com- pensation for pilot head motion creates excessive workload during hovering and nap- of-the-earth (NOE) flight. This high workload translates into excessive training require- ments. Part of the problem is there is no agreed upon set of definitions or descriptions for how HMD symbols are driven to compensate for pilot head motion. A candidate set of definitions is proposed to address this. There are several specific areas where additional simulation and flight experiments are needed. These include development of hover and NOE symbology which compensates for pilot head movement; the issue of display latency and sampling, and the tradeoff between FOV, sensor resolution and symbology. This work was sponsored by the Aeroflightdynamics Directorate, Ames Research Cen- ter, Moffett Field, California under contract NAS2-14151. Ms. Catharine P. Levin was Contracting Officer. Dr. Wendell Stephens was the Contracting Officer's Technical Representative. Their help is appreciated. The authors wish to acknowledge the assistance of Mr. Richard Scwartz of Lockheed- Martin who reviewed the optics chapter and Mr. Asa Mader of Indeterminate Media who prepared the the database. The many technical discussions with Mr. Loran Haworth of the Aeroflightdynamics Directorate were always interesting and of great help. Intentionally left blank Summary . iii Acknowledgements. iii Contents . v List of Figures . xi List of Tables xv Abbreviations xiii 1: Introduction . 1 A The ~eedFO; a ~esi~n~eihodolo~~ B Engineering Constraints C Display Design Fundamentals D The Evaluation Process E Relationship to Electronic Database F Organization of the Design Guide G References 2: The Need for a Design Methodology . A Precedents B Cross-over C New Challenges 3: Historical Review . A ~evelo~ment'ofcockpit ~ib~~a~s' B Development of Cockpit Automation C Cockpit Displays D Fly-By-Wire E HUD Development F HMD Development G Effect of Superimposed Imagery H Effect of Field-of-View I Spatial Disorientation J Symbology Lessons Learned K References 4: A Review of HMD Technology . A Differences Between HDD;, HUD~,and HMDS ' B Typical Arrangements C Data Processing D Head Tracking E Examples of HMD Designs F Rotary-Wing and VTOL HMD Symbology G Fixed-Wing Transport HMD Symbology H Fixed-Wing Fighter HMD Symbology I. Observations J. References 5: Design Methodology for Integrating HMDs . 105 A Introduction B Mission Considerations C Engineering Considerations D Cockpit Integration E Development of Display F References 6: Head-mounted Display Evaluations. 115 A History of Display Evaluations B Subjective Data C Test Approach D Evaluation Flight Tasks E Choice of Pilots F References 7: HMD Coordinate Systems 133 A Cockpit Geometry B Definitions C Reference Frames D Traps for the Unwary E Summary F References 8: A Review of Optics 151 A Optical ~undamentais B Pupil-Forming vs. Non-Pupil Forming Systems C Image Quality D See-Through Optics E References 9: Human Factors Issues. 171 A Human Vision B Display Issues C Data Latency Issues D Operator Precedents, Expectations, and Preferences E Spatial Disorientation F Helicopter Human Factors G Head and Neck Considerations H References 10: Optical Criteria 199 A ~ield-&iewm B Transmittance C Displacement Errors D Distortion E Optical Power F Binocular DisparitylAlignment G Symbologyllmage Display Accuracy H Symbologyllmage Display Luminance I Image Magnification J Image Rotation K Exit Pupil L Physical Eye Relief M lnterpupilary Distance (IPD) N Reflections 0 Chromatic Aberrations P ShphericalIAstigmatic Aberrations Q References 11: Environmental Criteria . 21 1 A Environmental Testing B Electromagnetic Interference C External Light D Power Requirements E References 12: Software Criteria . 21 3 A Software ~esi~n B Architecture C Data Fusion D Error Checking E Software Testing F Update Rates G Dynamic Response J Signal Augmentation I Damping J Jitter K Noise L Digital Displays M Dynamic Modulation Transfer Function N Documentation 0 References 13: Form and Fit Criteria . 221 A Head Tracker ~ccurac~ B Head Tilt Accuracy C Head-Tracker Field-of-Regard D Head-Tracker Latency E Fit F Head-borne Weight G Head-Protection H Egress I. References Mode and Functional Criteria . 229 A Symbol List B Horizon Reference C Symbol Priority D Declutter E Mode Annunciation F Warning Indications G Sensor Pointing Accuracy H Sensor Field-of-Regard I Sensor Gimballing J References Display Criteria . 235 A Compatibility 'With other ~is~la~s B Clutter C Size of Character D Shape of Symbols E Line Width F Fonts G Color H Raster Image I Resolution J Flicker K Coordinate Systems L References Primary Flight Display Symbology . 241 A Primary Flight Reference B Hover Mode C Nap-of-the-Earth Mode D Transition Mode E Low-Level Cruise Mode F Declutter G References Conclusions 255 A Issues B Comments C Recommendations D Summary E. References Glossary . 265 A loss& B References References Cited in Text 313 Bibliography 331 21 : Strawman HMD Specification Outline . 361 A General B Optical Specifications C Environmental Specifications D Software Specifications E Form and Fit Specifications F Functional Specifications G Display Specifications H Display Dynamics Specifications I Sensor Functional Specifications J References 22: Database Manual . 373 A Structure of database B User's Guide C Electronic Documentation D Database script (new material)) E References Intentionally left blank. -List of Figures- FigureTitle II Incorporation of Early Feedback in Cockpit Design 3.01 Design Flow Chart 3.02 Cockpit Design Flow Chart 3.03 Cockpit Design Flow Chart 3.04 Cockpit Design Flow Chart 3.05 Klopfstein (TC-121) HUD Symbology . 3.06 Apache Hover Symbology 3.07 Apache Cruise Symbology 3.08 Scene-linked HUD Symbology 4.01 Typical Civil HUD Architecture 4.02 HMD Data Architecture . 4.03 Global Pitch Ladder Symbol 4.04 Typical Optical Head Tracker 4.05 Typical Magnetic Head Tracker 4.06 UH-1 N Cruise ANVISIHUD Symbology 4.07 CH-47D ANVISIHUD Symbology .