# Augmented Reality Applications in Industry 4.0 Environment
## 4 Results
### Devices Used to Work with AR  
The real physical world can be augmented using two methods and several different devices as is shown in Figure 6. The first method is to equip an environment that can be carried out in two different methods. Projectors and holograms can be used for spatial AR where information can be projected onto 3D objects or screens. Large touch screens and tablets are used for computer-based AR. The second method involves equipping users with various smart devices. In the case of hand-held devices (HHD), there exists the possibility of using smartphones or tablets, while smart glasses are used in the case of head mounted displays (HMD). Almost two-thirds, 61%, of the analyzed papers show the implementation of AR by equipping the user.  
Processing and display of AR applications are performed on various visualization devices (Figure 7). Augmented reality smart glasses (ARSG) are among the most commonly used wearable devices for supporting operators in the shop-floor, with a share of 35%. The main advantage of ARSG is that in cases of industrial tasks, such as maintenance, repair or installation or assembly, workers can perform tasks hands-free while viewing in real-time [34; 35; 41; 45; 57; 60; 66; 69; 72; 93; 97; 100].  
According to the analysis of publications, the second most commonly used device to support AR in the industrial environment is the tablet (27%). Using tablets, AR can be administered by two methods, either as a computer based application or as a handheld  
Figure 6: Methods of AR application.  
Figure 7: Visualization devices for the application of AR.  
application. In the case of computer based applications, tablets are placed in a fixed position [67; 104]. On the other hand, in handheld applications the user must carry the device so his ability to perform the task is limited [40; 43; 47; 48; 49; 52; 55; 71; 75].  
Similar to fixed tablets, large touch screen devices (16%) can also be used to apply AR computer based applications [60; 62; 79; 80; 84; 85; 86; 87; 90; 91; 110]. These devices can be placed in the workplace by utilizing a camera that monitors the real world or as a part of the remote equipment used by experts.  
The use of projectors (15%) as a device for visualization of AR applications was also observed in the analyzed literature [28; 45; 47; 63; 69; 70; 81]. Additional task information can be projected on the big screen or on objects that are part of the task. Finally, smartphones (7%) are also used, but due to their relatively small size they are not utilized a large number of cases [52; 57; 77; 88; 110].  
Each of these devices has certain advantages and disadvantages. The main purpose of these devices is to help the user in performing the task and to improve his safety. In some cases, the use of smart glasses is optimal. In this case, the user's hands remain free and they possess all the necessary information in front of their eyes. There are wide ranges of ARSG available on the market today [111]. However, some technological improvements are still required in this field in order to extend the battery life and expand the field of view, increase the resolution and reduce the weight of the ARSG.  
On the other hand, the price of handheld devices (tablet and smartphone) is still relatively lower compared to smart glasses, but in the case that they are not used in computer applications they should be worn in the hands. Their smaller size is certainly an advantage due to their weight, while the main disadvantage is the amount of information that can be displayed.  
Computer based and projector based AR applications are stationary, connected to the work environment and difficult to make universal. Their advantage is that it is possible to easily utilize one device in different places by simply spreading the codes for them.