Automated Optical Treatment Based on Diffuse Reflectance Signals.

Laser-based therapies offer high spatial precision and minimal invasiveness but rely heavily on operator skill and continuous manual guidance. Inaccurate operation can lead to undesired laser damage to surrounding healthy tissue. Closed-loop feedback approaches have been explored in laser ablation but remain underdeveloped for applications such as pigment removal and bacteria inactivation. Here, we introduce signal-activated precision optical treatment (SPOT), a high-speed closed-loop feedback platform based on diffuse reflectance detection. A dedicated and modulated guidance laser continuously interrogates tissue reflectance, and lock-in detection selectively extracts the guidance laser reflectance while effectively rejecting ambient light interference. This design enables high sensitivity to small contrast differences and sub-microsecond response. We demonstrate automated pigment removal using a nanosecond laser and bacterial inhibition with a blue laser. The SPOT framework is adaptable to other optical signal detection, enabling automated, safer, and more precise laser therapies that minimize damage to healthy tissue.