# Resolution Aspects for Near-Field Projections
## 1 Introduction
The visual acuity influenced by age plays a significant role in general traffic. [PERSON] and [PERSON]'s examination illustrates an increase in older drivers in eight countries worldwide: the United States, Sweden, Norway, Great Britain, Canada, Japan, South Korea and Germany [23]. Second, [PERSON] et al. provide a study on the impact of age and sex on simple visual reaction times. The results state that age significantly influences the reaction times for participants older than 70 years. Additionally, the comparison shows a sex difference [20]. Henceforth, this indicates the importance of focusing on the older population for visual tasks in the context of future mobility concepts in urban environments. Second are environmental factors such as adaptation luminance, the projection surface, or viewing distance [12; 24; 25; 26; 27; 28]. In detail, the relationship between viewing distance, the resulting screen size and visual acuity has been under evaluation for several years for conventional displays or projection-based screens [24; 26; 27; 28]. Previous research from the television or physiology sector indicates the preferred viewing distance and screen size when viewing an image or video [26; 27; 28]. Additionally, the impact of the adaptation luminance is stated by [PERSON], as the findings illustrate that visual acuity varies with different adaptation luminance due to the interaction of cones and rods on the retina. Furthermore, the tested target shape influences visual acuity and the resulting detailed perception [28]. Moreover, [PERSON] discovered in his experiments in television research the correlation between viewing distance and the resulting screen size. Like [PERSON], [PERSON] had his participants set their optimal viewing distance for themselves in the various experiments [26; 27]. Both researchers, [PERSON] and [PERSON] [26; 27], varied the image size and/or the resolution. A point of criticism is that [PERSON] mixes certain influencing factors without considering their effect, for example, using different screen technologies (conventional display or projection screen) or changing the ambient lighting within the experiments [27]. Consequently, when mixing the methods and drawing a correlated conclusion, [PERSON]'s results must be considered with caution, and are saturated at increasing viewing distances due to decreasing visual acuity [27]. However, this outcome corresponds to the results of [PERSON] [26]. Furthermore, [PERSON] lists possible influencing factors crucial for the experimental setting, such as screen resolution, ambient lighting, video content and the participants' mindset [27]. Further, [PERSON] mentions that the various projection surfaces, like the different granularity of the asphalt, limit the image quality which an observer perceives when looking at a near-field projection [12]. It is necessary to examine the requirements for near-field projections in the automotive sector, especially for safety-relevant projections with potential differences for either text- or symbol-based projection content and the influence on the observer's perception of various lighting conditions. In this work, two subject studies present an experimental approach to defining an effective resolution on the street's surface in the near-field around the vehicle under two different lighting levels. Hence, the forced-choice method is used in the subject studies to collect the necessary data for subjective opinion regarding the resolution requirements for a high-quality projection. Consequently, logistic regression is applied to the data to evaluate thresholds for the perceived resolution and, finally, to establish resolution requirements for near-field projections. To the best knowledge of the author, the reported experiments are the first to systematically study repeatedly the impact on human perception by road-/near-field projections for either safety- or design-driven purposes.