Real-time laser detection method for edge position of objects with nanometer level accuracy

This study proposes an object edge position detection method with optical drift compensation based on the defect spot working mode of a position-sensitive detector (PSD). The proposed method utilizes the output characteristics of PSD in the defect spot working mode, the asymmetry of the defect spot, and the size transformation characteristics during the focused beam projection process to obtain ultra-high sensitivity gain for measuring object displacement and light deflection angle. The proposed system measures the beam angle drift while detecting the edge position of the object through a co path compensation optical path structure, thereby achieving real-time compensation of light drift and improving the accuracy of edge detection. To verify the feasibility and effectiveness of the method, calibration experiments and object edge position detection experiments were conducted using piezoelectric transducers (PZT). Experimental results show that, under the system setting parameters, the sensitivity of the proposed edge position detection system reaches 0.9 nm, and the standard deviation of multiple detections is 5 nm. Compared with edge detection methods based on image recognition and other methods, the proposed method achieves nanometer level detection accuracy while also having the advantages of a simple system and high real-time performance, and can be used for precision positioning, measurement, and other applications.