# Applications of Smart Glasses in Applied Sciences: A Systematic Review
## 1 Introduction  
With the development of information and communication technology, various forms of wearable devices that can replace smartphones are receiving attention. Wearable devices are defined as \"all devices capable of computing that can be worn on the body, including for applications that entail computing functions\" [1]. Wearable devices can be used for diverse purposes through the installation of applications available on a mobile operating system (OS), thereby providing various functionalities in addition to those related to fashion and health. Smart glasses are a type of wearable device that can be worn on the face, and they meet the original objective of enabling clearer vision in addition to functioning as a computer. Since Google released \"Google Glass\" in 2012, companies such as Sony, Microsoft, and Epson have launched their own smart glass products. Figure 1 shows an example of smart glasses, which provide the desired information to users through a display in the form of external glasses or binoculars. They support wireless communication technologies, such as Bluetooth and Wi-Fi, and can be used to search and share information in real time through an internet connection. In addition, by providing a location tracking function through the Global Positioning System (GPS), it is possible to develop various applications based on location information. As an interface for communication between smart glasses and users, a touch button or a natural language command processing method based on voice recognition is used. By using a camera mounted in front of the device, it is possible to acquire photographs or video data of the surrounding environment in real time [2]. In [3], the concept of virtual reality (VR) was introduced, and in [4], a head-mounted display (HMD) was first presented. Smart glasses are a technology based on optical HMDs (OHMDs), which comprise plastic objects placed at eye level, allowing the user to view an online digital world, an offline world, and the physical world [5]. Unlike smartphones and other wearable devices, smart glasses enable users to conduct tasks without extensive physical effort; for example, it is not necessary to use one's hands or eyes repeatedly to interact with a smart glass [6]. In addition, smart glasses are used in a variety of ways, including application development. Examples include information visualization, image data analysis, data processing, navigation, information transmission and sharing, and risk detection and warning [7; 8; 9; 10; 11; 12]. A number of studies have been conducted on smart glass technologies used in various fields, and various review papers have evaluated the suitability of smart glasses for research purposes. [PERSON] et al. [13] surveyed relevant studies using specific keywords and search engines to assess the suitability of smart glasses used in the medical field and analyzed and evaluated three specific products. [PERSON] et al. [14] focused on the technologies used in smart glasses applied to various services, and [PERSON] et al. [15] focused on the literature dealing with the ethical issues of smart glasses. In addition, [PERSON] and [PERSON] [16] analyzed the products, technologies, sensors, and other factors considered in prior studies after intensively investigating the input methods employed in the literature related to commercialized smart eyeglasses. [PERSON] et al. [17] evaluated the suitability of using smart glasses in the medical field and explored the corresponding merits and demerits for healthcare professionals. However, applications of smart glasses in all fields of applied sciences are yet to be reviewed systematically. The purpose of this study is to examine the current state of research based on smart glasses since 2014 through secondary research, grasp the research trends of smart glasses, and present the direction of future research.