An unobtrusive measurement tool is important for Human-Robot Interaction (HRI) research that does not want to attach markers or devices on the experiment subjects. This property allows a natural observation of interaction between human and robot during the experiment. In HRI, an experiment that involves with psychological evaluation usually requires physical measurement for evaluating the interaction, for instance, distance, direction, and approaching speed between human and robot. Low-profile Evaluation System (LES) is an ongoing work in creating an unobtrusive measurement tool for HRI research that provides 3D video recording, playback and measurement inside 3D scene in real-time. LES is designed to operate on a single computer to make setup and experiment outside laboratory environment easier. The demonstration in the real-word setup shows that LES provides acceptable 3D measurement accuracy for HRI research.