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

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Optical Performance 147 pay proper attention to these and corresponding issues can result in retinal rivalry, eye strain, fatigue, and, if severe enough, diplopia. Humans view scenes binocularly. Typically, an adult male’s eyes are located 55-73 mm apart with the eyes’ lines-of-sight converged to an angle that matches their accommodation distance. Because of this configuration, each eye sees a slightly different view (perspective) of the same scene, which provides depth perception and stereopsis. Biocular/binocular HMDs, while providing imagery to both eyes, can depart from this natural arrangement in several ways (National Research Council, 1997). Biocular HMDs use a single sensor to present the same image of the scene to both eyes, but lacking the disparity in perspective to provide stereopsis. ANVIS is a straight forward binocular display, using two input sensors separated by a distance to provide separate images to the two eyes. HIDSS is a biocular system. But, since the FLIR sensor FOV is larger than the display optics FOV, the HIDSS presents approximately two-thirds of the sensor FOV to each eye, resulting in a display FOV that matches the sensor FOV, but consists of two monocular regions and a central region seen by both eyes. Biocular tolerances Having two optical channels presents the opportunity to have disparities (mismatches) between the imagery presented to the two eyes. These disparities can be alignment errors or optical image differences. Alignment errors reflect lack of parallelism of the two optical axes and can be vertical, horizontal, and/or rotational. Optical image differences can be in contrast, distortion, size (magnification), and/or luminance (Self, 1986). These errors will exist. The question is what magnitude of disparity can be tolerated before performance noticeably degrades. These permissible differences are referred to as the optical tolerance limits for the HMD design. Self (1986) provides a review of optical tolerance studies conducted and standards developed before 1986. The results of the review are summarized in Table 5.6. Also included in Table 5.6 are more recent tolerance recommendations. It is important to note that users will have varying sensitivities to these tolerances. Table 5.6. Summary of binocular optical tolerance limits.
148 Clarence E. Rash and William E. McLean Vertical misalignment 8 arcminutes (2.3 mr) (Jacobs, 1943) 14 arcminutes (4.1 mr) (Harvey, 1970) 17 arcminutes (4.9 mr) (MIL-Hand-141, 1962) 2 arcminutes (0.6 mr) (U.S. Navy, 1966) 3.4 arcminutes (1 mr) (Gold and Hyman, 1970) 19 arcminutes (5.5 mr) (Lippert, 1990) 3.4 arcminutes (1 mr) (Gold, 1971) (Self, 1986) Horizontal misalignment (Convergence) 22.5 arcminutes (6.5 mr) (Jacobs, 1943) 28 arcminutes (8.1 mr) (Harvey, 1970) 2 arcminutes (0.6 mr) (Department of the U.S. Navy, 1966) 8.8 arcminutes (2.6 mr) (Genco, 1983) 8.6 arcminutes (2.5 mr) (Gold, 1971) 2.7 degrees (47.1 mr) (Farrell and Booth, 1984) Table 5.6. (continued) Horizontal misalignment (Divergence) 7.5 arcminutes (2.2 mr) (Jacobs, 1943) 14 arcminutes (4.1 mr) (Harvey, 1970) 4 arcminutes (1.2 mr) (Department of the U.S. Navy, 1966) 3.4 arcminutes (1 mr) (Gold, 1971) 4.1 arcminutes (1.2 mr) (Genco, 1983) 3.4 arcminutes (1 mr) (Gold and Hyman, 1970)
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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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Page 116: DESIGN ISSUES PART TWO
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Page 199 and 200: Visual Performance 181 0 to -5.25 d
Page 201 and 202: Visual Performance 183 Report No. 9
Page 203 and 204: Biodynamics 7 B. Joseph McEntire He
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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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