Laser curtain wall is an emerging security technology, offering high detection accuracy and strong environmental adaptability. However, conventional laser curtain detectors face issues, including complex manufacturing processes, low assembly efficiency, and poor adaptability to dynamic environmental conditions. These limitations restrict their large-scale application in construction sites, transportation hubs, and power facilities. Therefore, this study aims to design a modular laser curtain detector. By integrating structural simplification and beam expansion optimization with an objective evaluation model, it seeks to achieve rapid, accurate, and cost-effective intrusion monitoring in complex scenarios.

Based on a modular design concept, an integrated detection and alarm device was constructed to enable rapid assembly and flexible reconfiguration without complex wiring. To extend the detection range, three types of beam expansion systems—Galilean, Keplerian, and Cassegrain—were designed and compared. Furthermore, an evaluation model based on grey relational analysis (GRA) was established to conduct a multi-indicator quantitative analysis of beam uniformity, expansion loss, and device size. In practical application, a monitoring space of 30 m × 30 m × 20 m was set up at a 500 kV construction site, and field tests were conducted under various conditions, including wind speed, illumination, and electromagnetic interference.

Fig.5 showed the on-site deployment at the construction site. The modular design significantly reduced the system deployment time to less than 20 minutes and allowed flexible adaptation to irregular terrain, enabling rapid and low-cost setup. The system achieved a detection radius of 40 m, a response time of 0.1 s, and a positioning accuracy of ±0.01 m.To further increase the maximum detection distance, three laser beam expansion systems (Galilean, Keplerian, and Cassegrain) were constructed. Fig.6 showed the beam expansion results, verifying an approximately six-fold beam expansion capability and stable light intensity distribution. On this basis, a comprehensive evaluation system for laser beam expansion effects based on GRA was proposed. This system normalized and ranked multiple indicators such as beam uniformity, expansion loss, and device size, achieving an objective quantitative assessment. Table 2 and Fig.7 showed that the Cassegrain system performed the best, with the highest beam uniformity (2.189), the lowest expansion loss (3.0%), and the highest comprehensive GRA score (0.592), outperforming the Keplerian (0.587) and Galilean (0.577) systems. A theoretical analysis of the BK7 glass absorption coefficients and MgF₂ single-layer antireflection coating reflectivity (Fig.8) confirmed the rationality of the evaluation results. Table 3 demonstrated the system reliability based on field test results: under a wind speed of 5 m/s, the false alarm rate was 4.1%; under changing illumination and electromagnetic interference, the false alarm rate was 2.1% for both conditions, with no missed detections under any condition. Table 4 showed that, compared with existing commercial laser curtain products, this system’s detection range was increased to 40 m (more than double that of commercial products), costs were reduced by 30%~60%, and it exhibited lower false alarm rates and higher stability in complex environments.

This paper proposes a modular laser curtain detector. Through integrated design and beam expansion optimization, it enhances assembly efficiency and reduces system costs while achieving high stability and low false alarm rates in complex environments. Compared with existing technologies, this system offers advantages such as a longer detection range, stronger adaptability, and better cost-effectiveness. It provides a feasible new solution for intrusion protection at construction sites, power infrastructure, and other security-critical locations.