# Resolution Aspects for Near-Field Projections
## 1 Introduction  
Projections are widely used in several fields of application nowadays, such as the film industry, consumer electronics and the automotive industry. Nevertheless, all fields have specific challenges or advantages when looking at projection technologies. In the future, mobility concepts or technology automated vehicles will be dominant. No matter how long the transition phase from manually driven to automated vehicles will take, it is crucial to define and evaluate technologies for these types of mobility. Therefore, the automotive sector will play a significant role in future communications technologies such as projection- or display-based communication with other non-automated road users. In the automotive sector, near-field projections or displays are used to show graphical or informative content around the vehicle to welcome the vehicle user with a message or design-driven pattern. Additionally, near-field projections or displays can inform the vehicle user with vehicle-based information, such as the battery status of an electric vehicle, or situation-based content, such as weather information at the trip's destination. Both technologies are considered for communication for highly automated vehicles with other road users (RUs). However, projection-based communication has an advantage compared to display-based methods since a safety-relevant projection can be placed in the field of view of other RUs, e.g., a projected turn indicator to warn an upcoming cyclist of a turning vehicle. In general, digital projectors are widely used in different sectors, such as consumer electronics, film and automotive industries. Every application field targets a positiveexperience for the user. However, environmental factors, which influence the projected content, vary depending on the application sector. For example, the various requirements in the automotive industry are diverse when projections are applied in the interior with curved projection surfaces [1] or in the vehicle's exterior while projecting onto the street's surface [2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12]. In addition, several properties depend on the application sector, which is essential for research: contrast, brightness, resolution and others. Finally, an important aspect is a necessary resolution on the projected surface to generate a sharp and high-quality image. This factor gains importance, especially when looking at pixel-based digital projection technologies, where an LCD, LCoS, DMD, or uLED is used as an imager [13; 14; 15]. Besides decorative or design-related near-field projections next to the vehicle, another important application field is the safety-relevant projection content, which is crucial for other RUs, e.g., pedestrians and cyclists, especially in an urban environment. Current research focuses on the unambiguity, understanding and detection of the different projection content and where it will be illustrated [4; 8; 16; 17; 18; 19]. However, the research still needs to examine the required resolution from the pedestrian's perspective, which, on the one hand, is crucial in perceiving the illustrated projection content (symbol- or text-based message). On the other hand, the resolution is relevant for decisions on the projection technology and, therefore, the resulting use cases [4; 8; 9; 12]. [PERSON] et al. focused on the use case of cyclists, which are warned by a near-field projection (amber arrow sign) of a turning vehicle in a dusk scenario. Afterward, 19 participants provided a subjective opinion, where 86.8% of the subjects understood the intention of the turning vehicle better with the turn indicator projection compared to the situation with no illustrated projection [4]. Additionally, several influencing factors affect the observer's perception when interacting with a near-field projection. There are two main influence areas for the perception of near-field projections. First, the participant's personal factors influence visual acuity [20; 21; 22; 23].