Improvement in Laser-Irradiation Efficiency of Robot-Assisted Laser Hair Removal Through Pose Measurement of Skin Surface.

OBJECTIVE: This study aims to improve the performance of an automatic laser hair removal (LHR) system by applying an algorithm that considers the curve and slant of the skin surface.

BACKGROUND DATA: In an earlier research, a robot-assisted LHR system has been developed and validated for an almost flat skin or a relatively smooth curved part of the skin. For practical clinical applications, the feature of the robot-assisted LHR system is extended for real curved skins.

METHODS: A novel pose-measurement algorithm is developed and applied to the LHR system. This system detects a six-degree of freedom (DOF) pose of the skin surface using the pose-measurement algorithm. The main principle of this algorithm is finding the equation of a plane using three noncollinear points, which are obtained by sequential movement of a one dimensional laser sensor.

RESULTS: Evaluation of the proposed system was conducted. During the test, we demonstrated that the LHR device automatically and completely contacted the targets along the curved surface. The contact-accuracy test produced satisfactory outcome. The averages of the root mean square (RMS) of the position error and the RMS of the rotation were 1.4437 mm and 1.0982 degrees, respectively. The curvature measurement test produced a satisfactory average result of 0.0006 mm RMS error.

CONCLUSIONS: Using the proposed six-DOF pose-measurement algorithm, the performance of the robot-assisted LHR system could be significantly improved from the clinical point of view because most real skins have curved shapes.