# Augmented Reality in a Lean Workplace at Smart Factories: A Case Study
## 2 Literature Review
### Augmented Reality and Human Augmentation  
AR is one of the disruptive technologies that are emerging with Industry 4.0 and intends to combine the physical word with computer generated texts and images or animations, providing an intuitive interaction experience to the users [49]. AR can be defined as a real-time direct or indirect view of an enhanced or augmented real-world environment, combining real and virtual objects that interact in real-time, which allows the improvement of work performance and efficiency in a manufacturing environment [6; 7]. In other words, AR is used to supplement and enhance the physical environment, overlaying digital computer-generated information such as images, sound, video and graphics [50]. Nevertheless, AR applications should take into account all human senses [51] and aspects such as touch and haptic sensations can be employed to enhance the perception of the actual environment [52]. The goal is to enable organizations to join together processes and visualizations [50], which simplifies the user's experience by incorporating virtual details and reinforcing their understanding and involvement with the real world, augmenting the sense of reality in real-time [6]. In the last years, the way of providing information to operators has been changing [49; 53; 54; 55]. AR technology offers a range of chances for the manufacturing sector [56], since it can give operators access to data that cannot be obtained with their regular senses. What is more, this data is supplied in the pertinent context and when it is necessary [57]. AR has traditionally been primarily visual, enhancing sight sense. However, human perceptual capabilities are frequently shared by every sense, thus auditory and tactile senses are often enhanced as well within this context. In addition, AR can be used toenhance physical capabilities in order to reduce physical workload and improve ergonomic conditions and mitigate risks through the use of systems such as exoskeletons [58]. In sum, AR can be used to augment human senses, cognitive abilities and physical capabilities. The hardware used by AR technology can be divided into several categories: Head-Mounted Displays (HMD); Hand-Held Displays (HHD), Wrist-Worn Displays (WWD) and Spatial Augmented Reality (SAR) [59]. Moreover, Augmented Audio Reality (AAR) allows the augmentation of hearing sense, in order to perceive virtual sounds as an extension to the natural ones, creating a hybrid augmented environment [60], while the creation of super-strong humans in an industrial environment can be enabled by the use of wearable, lightweight, flexible and mobile exoskeletons [61]. Figure 1 shows the different types of AR, categorized into six different applications. AR technology has the potential to augment all human senses, providing virtual data to workers and extending, for example, their sight or hearing functions. Nevertheless, the prospects with regard to the utilization of this technology in industrial surroundings are not just restricted to sensory improvement, it is also possible to augment human beings in terms of their intellectual or cognitive abilities [62], as well as enhance their physical capabilities using exoskeletons in order to improve ergonomic conditions [63], allowing new forms of human actions [64]. AR application in the industrial environment holds a huge potential to augment human capabilities, specifically within the logistics area, allowing the improved of performance and efficiency, enhancing cognitive capabilities and reducing inequalities within workplaces [59]. Superimposing computer-generated information in the real world, in order to give relevant data that is not accessible within the real world, such as work instructions, directions or safety instructions, is one of the most promising possibilities of AR technology in a human-based environment [62].