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

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(Levinsohn and Mason, 1997) Image Sources 35 Specification 1-inch CRT 3/4-inch CRT ½-inch CRT Useable face plate size Final anode voltage Deflection sensitivity Face plate Fiber optic plano concave 19 mm dia 17.5 mm dia 11.5 mm dia 13 kV 12 kV 8.5 kV 1.29 A/cm 1.14 A/cm 1.5 A/cm Fiber optic plano concave Fiber optic plano concave Phosphor P53 P53 P53 Raster peak luminance Stroke peak luminance Raster line width Stroke line width Mass 75g excluding leads Dimensions 104 mm x 26.5 mm diameter 3000 fL 1500 fL 1500 fL 5000 fL 10000 fL 5000 fL 20 µm 30 µm 25 µm 25 µm 30 µm 30 µm 60g excluding leads 90 mm x 22.5 mm diameter 45g excluding leads 75 mm x 16.5mm diameter ratio of the luminous energy output to the electron beam energy input, range from 1-20%. [Efficiency values vary somewhat as a function of high voltage and spot size.] Luminance, also, is affected by beam writing speed, with slower speeds generating higher luminances. Miniature CRTs have demonstrated the capability of generating luminances > 6000 fL in stroke mode and > 3000 fL in raster mode. Contrast is an important FOM which is tied to the ability of the human visual system to detect the luminance difference between two adjacent
36 Clarence E. Rash, Melissa H. Ledford, and John C. Mora areas. A number of definitions and associated equations are used to express measures of contrast, e.g., contrast, contrast ratio, contrast modulation, etc. (Klymenko et al., 1997). In analog displays, such as CRTs, the range of contrast available is often expressed using the artificial concept of shades of grey (SOGs). SOGs are luminance steps which differ by a defined amount. They are by convention typically defined as differing by the square-root-of-two (approximately 1.414). In miniature CRTs for aviation, a minimum of 6 SOGs is considered acceptable for pilotage imagery. [This last statement is based on IHADSS experience.] The selection of a CRT phosphor is based on those phosphor characteristics which impact the application the most. The phosphor characteristics generally of greatest interest are luminous efficiency, spectral distribution, and persistence. Fielded ANVIS use the P20 (older) or P22-Green (newer - adopted for environmental concerns over cadmium in the P20) phosphors; IHADSS uses the P43 (which is being fielded for ANVIS use also) and the HIDSS currently uses the P53. A summary of characteristics for these phosphors is given in Table 2.2. Luminous efficiency Table 2.2. Phosphor characteristics. (EIA Tube Engineering Advisory Council, 1980) P20 (Zn,Cd)S:Ag ANVIS Persistence Medium 3 msec Spectral distribution P22-Green (ZnS):Cu,Al ANVIS P43 (Gd 2O 2)S:Tb IHADSS P53 (YAGaG:Tb) HIDSS 18.7% 12.4% 10.2% 6.3% Broad band 495 to 672 nm 560 nm peak Color Green/Greenyellow Medium 3 msec Broad band 495 to 660 nm 530 nm peak Green/Greenyellow Medium 1.3 msec Narrowband 540 to 560 nm 543 nm peak Medium 6.7 msec Narrowband 540 to 560 nm 546 nm peak Green-yellow Green-yellow Note: Most phosphors have several formulations which can result in differing persistence, peaks, and efficiencies. The spectral distribution of a phosphor is important in transferring display luminance to the eye. The eye’s photopic (daytime, >1 fL) response peaks at approximately 555 nanometers (nm), which is in the
Page 1: Helmet-Mounted Displays: Design Iss
Page 4 and 5: The views, opinions, and/or finding
Page 6 and 7: vi Contents 4. Visual Coupling Clar
Page 8 and 9: viii Contents References ..........
Page 10: x Ben T. Mozo, Research Physicist U
Page 13 and 14: xii Foreword began its phenomenal e
Page 15 and 16: xiv Preface Acknowledgments The aut
Page 18 and 19: Introductory Overview 1 Clarence E.
Page 20 and 21: Introductory Overview 5 Figure 1.2.
Page 22 and 23: Introductory Overview 7 The trend f
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Page 26 and 27: Introductory Overview 11 aviator to
Page 28 and 29: Introductory Overview 13 1970's. Ta
Page 30 and 31: Introductory Overview 15 Image sour
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Page 34 and 35: Table 1.3. HMD performance figures-
Page 36 and 37: Introductory Overview 21 direct vie
Page 38 and 39: Introductory Overview 23 Figure 1.9
Page 40 and 41: Introductory Overview 25 Figure 1.1
Page 42 and 43: Introductory Overview 27 Ercoline,
Page 44 and 45: Introductory Overview 29 II, Procee
Page 46: Introductory Overview 31 Armstrong
Page 49: 34 Clarence E. Rash, Melissa H. Led
Page 53 and 54: 38 Clarence E. Rash, Melissa H. Led
Page 55 and 56: 40 Liquid crystal Clarence E. Rash,
Page 70 and 71: Optical Designs 3 William E. McLean
Page 72 and 73: Optical Designs 57 and plotted in l
Page 74 and 75: Optical Designs 59 phosphors, (b) u
Page 76 and 77: Optical Designs 61 optics. Examples
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Page 80 and 81: prism combiner. Optical Designs 65
Page 82 and 83: Figure 3.2. (continued) Optical Des
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Page 86 and 87: Optical Designs 71 Figure 3.4. Comp
Page 88 and 89: Optical Designs 73 Figure 3.6. Opti
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Page 92 and 93: Optical Designs 77 Figure 3.9. Ray
Page 94 and 95: Optical Designs 79 incidence and re
Page 96 and 97: 80 Clarence E. Rash hinted at befor
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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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168 Number of SOG = � log (C r) /
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Visual Performance 6 William E. McL
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Visual Performance 171 observer is
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seen. Visual Performance 173 Figure
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Visual Performance 175 perception.
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Visual Performance 177 with monovis
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Visual Performance 179 individuals
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Visual Performance 181 0 to -5.25 d
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Visual Performance 183 Report No. 9
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Biodynamics 7 B. Joseph McEntire He
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Biodynamics 187 behavior of this de
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Figure 7.2. Head anatomical coordin
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Biodynamics 191
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Biodynamics 193 al., 1972), and man
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Biodynamics 195 Figure 7.5. Vertica
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Biodynamics 197 disability and fata
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Biodynamics 199 been fabricated int
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Biodynamics 201 Ty pic al acc ele r
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Biodynamics 203 exceed the mechanic
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Biodynamics 205 complexity and comp
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Type Reference helmet Foam in place
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Biodynamics 209 the fitting problem
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Biodynamics 211 adjustment buckle,
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Biodynamics 213 down. The helmet ma
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Biodynamics 215 Desert Shield/Deser
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Biodynamics 217 Donelson, S. M., an
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219 Fort Rucker, AL: U.S. Army Aero
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220 Ben T. Mozo Figure 8.1. Noise l
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222 Ben T. Mozo available in the ne
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224 Ben T. Mozo Protectors”(ANSI,
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226 Ben T. Mozo language. Tests of
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228 Ben T. Mozo Figure 8.6. Speech
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230 Ben T. Mozo the communications
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232 Ben T. Mozo Item Mass (grams) C
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Ribera, J. E., and Mozo, B. T. Unda
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236 Joseph R. Licina operational us
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238 Joseph R. Licina Standard MIL-S
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240 Joseph R. Licina On electro-opt
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242 Joseph R. Licina For HMDs with
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244 Joseph R. Licina 1994b) that wi
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246 Joseph R. Licina Table 9.2. Hea
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248 Joseph R. Licina provided a 93.
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250 Joseph R. Licina and buckles, a
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252 Joseph R. Licina authorized to
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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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