Online monitoring of a high-power CW laser optical mirror based on infrared and visible image features visualization

In high-power CW (continuous wave) laser systems, laser damage to optical mirrors often occurs, and it is urgent to develop timely and effective monitoring technologies to avoid laser damage or emergency stop at the early damage stage. In this paper, an online monitoring method based on the combination of infrared and visible images is proposed. The proposed method is based on the feature recognition of infrared and visible images. After setting an appropriate threshold, a decision model can be employed to enable real-time monitoring and health status evaluation of optical mirrors. Here, the thresholds for abnormal and dangerous temperatures were established at 100°C and 200°C, respectively. The results show that the temperature of the optical mirror would significantly increase after damage, with the surface temperature of the element reaching up to 250°C. At the same time, the damaged area could be captured by a visible camera and the changes in gray values were displayed in the visible image. Online monitoring of the health status of optical elements can be achieved by assessing changes in infrared image temperature, visible image spot position, and area. This monitoring method serves as an early warning method for potential optical elements damage.