## 2 Literature Review
### Eye-Tracking Experiment  
In contemporary vision experiments, the eye-tracking experiment is a common research and analytical tool. It can accurately capture the visual state and data of human eye vision in space and record eye-tracking trajectories within a defined timeframe, which can offer a powerful complement to subjective evaluation [18]. Currently, eye-tracking technology is widely used in medicine, behavioral research, human-computer interaction design, and design evaluation. (1) In the medical field, many scholars have used eye-tracking experiments to assist in and improve medical diagnoses. [PERSON] et al. [19] used eye-tracking methods to optimize the design of a user-centered self-injection system. [PERSON] et al. [20] assessed deficits in sports medicine clinicians' perceptions of eye movements associated with concussion through an online survey and determined that eye-tracking experiments could be effectively used in concussion diagnosis. [PERSON] et al. [21] demonstrated that the use of eye-tracking experiments and think-aloud protocols could help clinical laboratories to improve MDX report designs in a precision oncology setting. [PERSON] et al. [22] investigated the fixation behavior of children with ASD and TD in a classroom setting and used an eye-tracking experiment to develop and test a manipulative training tool that can be used to improve the typical fixation behavior of children with ASD. (2) Research and applications on user fixation behavior during various activities have been conducted in combination with eye-tracking experiments. [PERSON] et al. [23] used eye-tracking to study the association between teacher fixation and student-rated teacher interpersonal behavior. [PERSON] et al. [24] proposed a generative framework based on the hidden Markov model (HMM) and applied it to study selective sustained attention in children. [PERSON] et al. [25] used an eye-tracking experiment to compare the visual behavior and decision making in interactions between coaches and young players in the analysis of volleyball attack scenarios. (3) Eye-tracking experiments are used in the field of human-computer interactions to improve the user experience of interactive systems. [PERSON] et al. [26] developed an eye-tracking-based assistive system to control and monitor an IoT-based smart home. [PERSON] et al. [27] developed an eye-tracking typing application for a virtual keyboard based on eye-tracking experiments. [PERSON] et al. [28] designed human-centered cockpits to improve the safety and personnel performance in aviation by using eye-tracking to compare interactions with two different designs for crew alert systems. (4) Eye-tracking technology has been used to investigate the physiological-visual perception of users so as to explore the factors and effects of a design on their visual perception. [PERSON] et al. [29] used eye-tracking experiments to explore the size and design of alcohol content labels and how the strength of alcohol displayed on these labels affects consumers' visual attention. [PERSON] et al. [30] proposed combining VR with eye-tracking to measure consumers' visual attention in markets. [PERSON] et al. [31] used EEG and eye-tracking to investigate the issue of the implicit monitoring of users' perceptual responses to vehicle design. Based on the above research, this study combines eye-tracking experiments to quantitatively analyze the visual-perceptual traits of users when they observe the coating design of machine tools and provide optimization guidance regarding the details of the coating design schemes of machine tools. Machine tools are large and complex industrial machines, and any flaw in the modification process will likely result in major costs and time expenditure. Thus, we summarize the coating design specification of machine tools based on an eye-tracking experiment and use this information to guide the optimization of the design schemes to improve the economic efficiency of the optimization process of the coating design of machine tools.