ABSTRACT
Conventional head-up displays (HUDs) suffer from a limited exit pupil and a lack of compactness mainly due to the use of bulky optics. HUDs need a high-quality image with a large field of view (FOV) in small packaging to gain commercial acceptability. Holographic HUDs are phase-only devices that allow vision correction and focus adjustment while having a wide FOV. However, the limited bandwidth of a spatial light modulator (SLM) imposes a trade-off between the FOV and eye-box size. Combining a holographic system with an image-replicating element eliminates such a tradeoff. For image replication, we designed and fabricated a compact 2D diffractive beam splitter formed from two perpendicular volume gratings operating in the Raman-Nath regime. The gratings were recorded holographically in photo-thermo-refractive (PTR) glass, with optimized index modulation, thickness, and period to provide uniform intensity distribution across all desired orders for the fundamental red, green and blue (RGB) colors. We demonstrated a full-color holographic projection with an eye-box expanded by the designed 2D diffractive beam splitters.
ABSTRACT
Background: Older drivers are a rapidly growing demographic group worldwide; many have visual processing impairments. Little is known about their preferences about vehicle instrument cluster design. Methods: We evaluated the psychometric properties of a questionnaire on "dashboard" design for a population-based sample of 1000 older drivers. Topics included gauges, knobs/switches, and interior lighting; items were statements about their visual design. Response options used a Likert-scale ("Definitely True" to "Definitely False"). Factor and Rasch analyses identified underlying subscales. Results: Driver responses revealed four thematic subscales fitting the Rasch model: cognitive processing, lighting, pattern recognition, and obstructions. Internal consistency of subscales was acceptable (0.70-0.87); all possessed a sufficiently unidimensional structure. Opportunities for improvement were identified (item scope, category ordering, discrimination of respondents' perception levels). Conclusions: Assessment of motor vehicle dashboard preferences indicated cognitive processing, lighting, pattern recognition, and obstructions are areas relevant to older drivers. Future work will examine the relationship between older drivers' visual function (e.g., contrast sensitivity, visual processing speed) and their design preferences as revealed by the Dashboard Questionnaire, with the aim to optimize instrument cluster displays for older drivers.
ABSTRACT
Little is known about older drivers' preferences and attitudes about instrumentation design in vehicles. Yet visual processing impairments are common among older adults and could impact their ability to interface with a vehicle's dashboard. The purpose of this study is to obtain information from them about this topic, using focus groups and content analysis methodology. A trained facilitator led 8 focus groups of older adults. Discussion was stimulated by an outline relevant to dashboard interfaces, audiotaped, and transcribed. Using multi-step content analysis, a trained coder placed comments into thematic categories and coded comments as positive, negative, or neutral in meaning. Comments were coded into these categories: gauges, knobs/switches, interior lighting, color, lettering, symbols, location, entertainment, GPS, cost, uniformity, and getting information. Comments on gauges and knobs/switches represented half the comments. Women made more comments about getting information; men made more comments about uniformity. Positive and negative comments were made in each category; individual differences in preferences were broad. The results of this study will be used to guide the design of a population-based survey of older drivers about instrument cluster format, which will also examine how their responses are related to their visual processing capabilities.
