# Augmented Reality Applications in Industry 4.0 Environment
## 1 Introduction  
The Industry 4.0 (I4.0) concept transforms the current industrial environment through the digitization of production, automation and the integration of the production site into a comprehensive supply chain. This concept consists of full network integration and real-time information exchange [1]. The latest technologies, such as the Internet of Things (IoT), cloud manufacturing (CMFg), Big Data, augmented reality (AR), etc., are used in combination with concepts and techniques of traditional industrial production [2]. These technologies enable the establishment of smart factories, all with the aim of optimizing production processes by minimizing production costs, maximizing product quality and providing agile response to rapid changes in the global market [3,4]. In order to achieve this operational state, it is inevitable that current production processes must be redesigned, transformed and improved by introducing new technologies, devices and techniques [5]. The new industrial environment provides the backbone for the development of smart, flexible and configurable processes [6,7]. One of the most significant transformation can be observed in the work environment, specifically during human machine collaboration where the physical and virtual worlds merge [8]. Virtual animations and simulations of products and processes, as well as visualizations of raw and computational information, are just some of the key aspects necessary to achieve a Cyber Physical System (CPS) [9]. Adopting visual computing by using AR combined with the availability of appropriate data can improve vertical integration within the factory [10]. AR represents a new form of worker support and also a crucial link between humans and the I4.0 environment as a method of human machine collaboration [11,12]. Equipped with appropriate technological support, AR is able to transform present day workers into the smart workers/operators of the future. These smart workers are becoming one of the key elements of the I4.0 environment asstrategic decision makers and flexible problem-solving operators [13; 14]. In that case, AR represents a key link between the factory's web database and smart workers by presenting the right information in the right place [15]. The challenge is to develop AR applications that can lead to shorter production times, cost reductions and quality improvements [16]. Process control using AR can be based on BCI (Brain Computer Interfaces) technology. BCI technology enables direct contact between the brain and an external device and, based on the generated signals, it is possible to control the process and influence various objects in space, including, for example, the movement of a mobile robot in different manners [17]. AR applications show the potential to assist in solving problems such as limited availability of information to workers, insufficient training of workers, the gap between practical application and planned solution and poor communication between actors in an industrial environment [18]. Moreover, AR can potentially simplify a worker's tasks and optimize their decisions by introducing real-time virtual information into their environment. Regardless of the level of digitalization and automation in the industrial environment, they will continue to be key decision makers in the foreseeable future. AR can also play a significant role in improving occupational safety conditions in industrial environments, as workers' injuries are mainly associated with inadequate training, insufficient work experience and monotony at work [19]. AR can also be useful in areas of the product life cycle outside the design and production phases. In particular, it provides marketing opportunities by transforming the customer experience in pre-sales [20]. AR can also improve the after-sales experience by providing the user with AR manuals, repair instructions or communication from after-sales sales professionals, etc.