Helmet-Mounted Displays: - USAARL - The - U.S. Army

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204 B. Joseph McEntire Fi gure 7. 10. V ector li mits fo r H MD br eakaw ay force. In divid u a l Fi tting S ys t e m s T h e se lectio n of a helmet fitting system has become more involved with increased helmet
Biodynamics 205 complexity and compatibility requirements. The primary function of the fitting system is to provide a comfortable, stable fit to the wearer. Comfort can be achieved by distributing the helmet weight across the head, thereby preventing or reducing the occurrence of “hot spots” (singular points of increased pressure), and resisting heat buildup. Stability is dependent on both, the helmet’s retention and fitting systems. Numerous fitting methods have been used and devised for aircrew helmets. Listed and described in Table 7.2 are some of the fitting systems previously used, currently in use, and proposed concepts. This table is not all inclusive, nor does it identify all of the attributes of each system. Some attributes which should be considered when selecting a fitting system include; fitting ease, sanitation, durability, maintainability, comfort, stability, low load deformation, impact attenuation effects, and retention effects. Another parameter is the anthropometric range the system can accommodate and the number of helmet sizes being designed. Fewer helmet sizes suggest the fitting system accommodate a greater anthropometric range. If designing a helmet system with a restricted exit pupil location, numerous helmet sizes may be required with a minimal thickness fitting system. Such design considerations will influence the type and configuration of the selected helmet fitting system. In the Army’s early Aviator Protective Helmet No. 5 (APH-5), multiple leather pads of varying thicknesses were employed. Initially, they were glued to the polystyrene liner; later self-adhesive strips were used. The SPH-3 and SPH-4 helmets initially used a sling suspension system consisting of three nylon cross straps which ran across the top of the head and a leather head band which ran around the circumference of the head, above the brow line. In the center where the cross straps intersected, there was a cushion pad (Figure 7.11). Both the head band and the cross straps were adjustable. Formally introduced in the SPH-4 helmet in the mid 1980s, a fitting system design based on thermoplastic liners (TPL TM ) is used in the SPH-4B and the HGU-56/P helmets. The TPL TM system typically consists of 2 to 5 plies of thermoplastic sheets with 1/4 inch diameter dimples (open cell), covered with a cloth cover (Figure 7.12). The TPL TM system was adopted to improve comfort and to alleviate fitting problems with the original sling suspension of the SPH-4 helmet brought on by extended mission lengths, the introduction of NVGs, and the increase in the number of female aircrew
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Helmet-Mounted Displays: Design Iss
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The views, opinions, and/or finding
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vi Contents 4. Visual Coupling Clar
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viii Contents References ..........
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x Ben T. Mozo, Research Physicist U
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xii Foreword began its phenomenal e
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xiv Preface Acknowledgments The aut
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Introductory Overview 1 Clarence E.
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Introductory Overview 5 Figure 1.2.
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Introductory Overview 7 The trend f
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Introductory Overview 9
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Introductory Overview 11 aviator to
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Introductory Overview 13 1970's. Ta
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Introductory Overview 15 Image sour
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Introductory Overview 17
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Table 1.3. HMD performance figures-
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Introductory Overview 21 direct vie
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Introductory Overview 23 Figure 1.9
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Introductory Overview 25 Figure 1.1
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Introductory Overview 27 Ercoline,
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Introductory Overview 29 II, Procee
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Introductory Overview 31 Armstrong
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34 Clarence E. Rash, Melissa H. Led
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40 Liquid crystal Clarence E. Rash,
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Optical Designs 3 William E. McLean
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Optical Designs 57 and plotted in l
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Optical Designs 59 phosphors, (b) u
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Optical Designs 61 optics. Examples
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Optical Designs 63
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prism combiner. Optical Designs 65
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Figure 3.2. (continued) Optical Des
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Optical Designs 69
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Optical Designs 71 Figure 3.4. Comp
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Optical Designs 73 Figure 3.6. Opti
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Optical Designs 75 Figure 3.8. Refl
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Optical Designs 77 Figure 3.9. Ray
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Optical Designs 79 incidence and re
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80 Clarence E. Rash hinted at befor
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82 Clarence E. Rash metal tolerant
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84 Clarence E. Rash the performance
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86 Clarence E. Rash Figure 4.3. Hig
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88 Clarence E. Rash imagery in HMDs
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90 Clarence E. Rash as with ANVIS.
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92 Clarence E. Rash performance, on
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94 Clarence E. Rash effects on visu
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96 Clarence E. Rash concerning roll
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98 Aeromedical Research Laboratory.
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DESIGN ISSUES PART TWO
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102 Clarence E. Rash and William E.
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104 Contrast Clarence E. Rash and W
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Page 187 and 188: Visual Performance 6 William E. McL
Page 189 and 190: Visual Performance 171 observer is
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Page 197 and 198: Visual Performance 179 individuals
Page 199 and 200: Visual Performance 181 0 to -5.25 d
Page 201 and 202: Visual Performance 183 Report No. 9
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Page 205 and 206: Biodynamics 187 behavior of this de
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Page 211 and 212: Biodynamics 193 al., 1972), and man
Page 213 and 214: Biodynamics 195 Figure 7.5. Vertica
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Page 217 and 218: Biodynamics 199 been fabricated int
Page 219 and 220: Biodynamics 201 Ty pic al acc ele r
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Page 227 and 228: Biodynamics 209 the fitting problem
Page 229 and 230: Biodynamics 211 adjustment buckle,
Page 231 and 232: Biodynamics 213 down. The helmet ma
Page 233 and 234: Biodynamics 215 Desert Shield/Deser
Page 235 and 236: Biodynamics 217 Donelson, S. M., an
Page 237 and 238: 219 Fort Rucker, AL: U.S. Army Aero
Page 239 and 240: 220 Ben T. Mozo Figure 8.1. Noise l
Page 241 and 242: 222 Ben T. Mozo available in the ne
Page 243 and 244: 224 Ben T. Mozo Protectors”(ANSI,
Page 245 and 246: 226 Ben T. Mozo language. Tests of
Page 247 and 248: 228 Ben T. Mozo Figure 8.6. Speech
Page 249 and 250: 230 Ben T. Mozo the communications
Page 251 and 252: 232 Ben T. Mozo Item Mass (grams) C
Page 253 and 254: Ribera, J. E., and Mozo, B. T. Unda
Page 255 and 256: 236 Joseph R. Licina operational us
Page 257 and 258: 238 Joseph R. Licina Standard MIL-S
Page 259 and 260: 240 Joseph R. Licina On electro-opt
Page 261 and 262: 242 Joseph R. Licina For HMDs with
Page 263 and 264: 244 Joseph R. Licina 1994b) that wi
Page 265 and 266: 246 Joseph R. Licina Table 9.2. Hea
Page 267 and 268: 248 Joseph R. Licina provided a 93.
Page 269 and 270: 250 Joseph R. Licina and buckles, a
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254 Joseph R. Licina a nuclear flas
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256 Joseph R. Licina requirements:
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HMD PERFORMANCE ASSESSMENT PART THR
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262 Clarence E. Rash, John C. Mora,
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Glossary 11
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270 making stereoposis possible. Bi
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272 John C. Mora and M elissa H. Le
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NOTES ON CONTRIBUTORS Melissa H. Le
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Notes on Contributors 281 Research
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284 Index Breakaway force (see Fran
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286 Index movement, 55, 80, 84, 90,
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288 Index 198, 204, 205, 208, 210,
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290 Index Microphone, 15, 186, 224,
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292 Index Speech intelligibility (S
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