Figure 1
a) A diagram of the system illustrating the following: “1” indicates the direction that the subject is facing, “2” indicates the infrared-emitting LED, and “3” indicates the infrared receiver. b) A photo of the system shows the positions of 2 and 3. c) A diagram of the subject’s head rotation. The angle of the head rotation is calculated through trigonometric functions using the known length y and the measured length z. d) An overview from one side of the system.