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

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Image Sources 45 the dye particles are dispersed back into the suspendant, and the surface takes on the color of the suspendant. EP displays offer the desirable features of large area, wide viewing angle, and long memory without the need of a power supply (Castellano, 1992; Tannas, 1985; Toyama et al., 1994). Digital micromirror The digital micromirror device (DMD) display is a matrix where each pixel is a very small square mirror on the order of 10-20 microns. Each mirror pixel is suspended above two electrodes driven by complementary drive signals. The mirrors are suspended between posts by a very thin torsion hinge attached to opposite (diagonal) corners of the mirror. When no signal voltage is applied, the mirror is in its flat state. The application of a drive signal causes the mirror to tilt one way or the other. The mirror tilt is typically 10 degrees. These two conditions (actually three, since the tilt can be in two directions) correspond to “on” and “off ” pixel states. Images are formed by using the mirrors to reflect light. DMDs are used in projection displays and offer potentially significant advantages in size, weight, and luminance capability over other types of projection systems (Critchley et al., 1995; Sampsell, 1994). Summary Further detailed descriptions of these technologies can be found in Tannas (1985), Clark (1992), and Biberman and Tsou (1991). While overcoming the weight, size, power, and heat generation deficiencies of CRTs, each FP technology offers advantages and disadvantages. These are summarized in Table 2.3. A survey of existing FP technologies (Harding et al., 1996) to identify those promising the most potential for Army aviation use concluded that AMLCD, EL, and plasma were the most commercially available technologies. LCDs, by far, are the most mature of the FP technologies and, therefore, the most likely candidate for aviation applications. In fact, Table 2.3. FP technology advantages and disadvantages.
46 Clarence E. Rash, Melissa H. Ledford, and John C. Mora Technology Advantages Disadvantages AMLCD 1. Full color 2. Superior image quality 3. Video speed for general viewing Passive LCD 1. Low cost 2. Simple design Electroluminescent 1. Very rugged 2. High resolution 3. Wide viewing angle 4. Long life Plasma 1. Long life 2. High luminance Field emission 1. High luminance 2. High energy efficiency Digital micromirror 1. High luminance for projection 2. Reduced flicker Light emitting diode 1. Limited viewing angle 2. Requires backlighting 3. Limited video speed for military applications 1. Reduced resolution 2. Slow response 1. Limited brightness 2. Full color under development 3. Inefficient drive scheme 1. Affected by electromagnetic fields 1. Questionable reliability 2. Higher voltages required 3. Production problems 1. Temporal artifacts 2. Artifacts, both temporal and spatial 1. Low cost 1. Lack of full color 2. High power requirement Electrochromic 1. High contrast 1. Addressing techniques 2. Low pixel addressing speed Electrophoretic 1. Low power requirement 1. Suspensions are complex and hard to reproduce 2. Low pixel addressing speed Vacuum fluorescent 1. High luminance 2. Wide viewing angle 1. Limited resolution AMLCDs have been selected by the Comanche program for both its paneland head-mounted displays. In November 1997, it was decided to replace the miniature CRTs in the HIDSS with AMLCDs. Considerable effort has been put into establishing criteria for the use
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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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Page 18 and 19: Introductory Overview 1 Clarence E.
Page 20 and 21: Introductory Overview 5 Figure 1.2.
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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,
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Page 46: Introductory Overview 31 Armstrong
Page 49 and 50: 34 Clarence E. Rash, Melissa H. Led
Page 55 and 56: 40 Liquid crystal Clarence E. Rash,
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Page 70 and 71: Optical Designs 3 William E. McLean
Page 72 and 73: Optical Designs 57 and plotted in l
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Page 76 and 77: Optical Designs 61 optics. Examples
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Page 106 and 107: 90 Clarence E. Rash as with ANVIS.
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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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