# Review of Microsoft HoloLens Applications over the Past Five Years
## 3 Results
### Applications in Engineering Fields
#### 3.2.1 Industrial Engineering  
Currently, industrial manufacturing is changing to flexible and intelligent manufacturing and the development of automation and robotics, information and communication technology (ICT) has increased the efficiency and flexibility of production. As industrial robots are introduced and become increasingly used in the manufacturing industry, it is important to isolate and monitor the workspaces of the human workers and robots. Recently, HoloLens has been used to monitor the workspaces of industrial robots. Furthermore, AR devices have been used for the maintenance, repair and retrofitting of robots, as well as for product assembly and production management. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Reference** & **Year** & **Aim of Study** & **Number of Citations** & **HoloLens Version** & **Visualization Technology** & **Functionality** \\ \hline [PERSON] et al. [48] & 2020 & Evaluation of the learning effects of AR in physiology and anatomy learning & 3 & 1 & AR & Interaction \\ \hline [PERSON] et al. [49] & 2020 & Evaluation of the utility of HoloLens in virtual autopsy & 1 & 1 & AR & Interaction \\ \hline [PERSON] et al. [50] & 2018 & Development of training system for orthopedic open surgery using AR & 71 & 1 & MR & Immersion \\ \hline [PERSON] et al. [51] & 2020 & Digital simulation of surgical operation using HoloLens & 2 & 1 & MR & Interaction \\ \hline [PERSON] et al. [52] & 2017 & Development of AR-based telemedicine mentoring service & 70 & 1 & AR & Immersion \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary of Microsoft HoloLens application for medical education and simulation. [PERSON] et al. [53] proposed an interactive AR user interface (UI) to monitor and secure the minimum protective distance between a robot and an operator in the industrial manufacturing field. The AR UI was implemented with two pieces of hardware--a projector-mirror setup and wearable AR gear (HoloLens). The workspace model and UI were evaluated in a realistic diesel engine assembly task. Compared with the baseline without interaction, it was confirmed that AR-based interactive UIs reduce the time required for task completion and robot idle time. However, according to the user experience evaluation, AR using HoloLens is not yet suitable for industrial manufacturing and the projector-mirror setup needs improvement with respect to safety and work ergonomics. [PERSON] et al. [54] used an AR device to convey the motion intent of an industrial robot to the user. The AR visualization of the robot's path, preview and volume enables users to perceive the movement of the robot in the workspace. The AR devices were also used to visualize the future path of the end-effector, the complete robot configuration model projected into the future and the volume slice that the robot projected onto a 2D circle, which would be occupied in the future. The proposed visualization shows the robot's motion only for a short time ahead, while the robot is moving; however, this visualization is sufficiently long for the operator to recognize and react to the oncoming robot. Furthermore, it has been shown that collisions between the robots and human workers can be prevented in advance, which minimizes the downtime and reduces productivity losses. [PERSON] et al. [55] proposed a method for remodeling production machinery using AR. In the case study, they analyzed how to help machine users perform tasks in the right sequence, to save retrofit time and cost. Owing to HoloLens' work support, the users were able to obtain a type of navigation system. Additionally, the system can be edited to retrofit production machines for which user manuals are no longer available. [PERSON] et al. [56] presented the results of the research conducted using AR-based and audio-only communication systems for remote maintenance in a real-world industry setting.