OKAS-3D - OPTOELECTRONIC JAW MOVEMENT RECORDING-SYSTEM WITH 6-DEGREES-OF-FREEDOM

OKAS-3D is a further development of the single floating circle target tracker. This tracker consists of a cathode ray tube display, a lens i n front of the display and a circular light-sensitive photocell placed in the image field of the lens. A small circular trace generated on t he screen is focused around the photocell. The sinusoidal electrical o utput of the photocell contains all the relevant information regarding the position of the photocell relative to the image of the circular l ight trace. This gives the tracker the properties of a servo-controlle r with position feedback. In OKAS-3D three pairs of photocells are loc ated on two lightweight frames attached to the upper and lower frontal teeth by individually adapted clutches. By using the formulas of rigi d body mathematics, the motion of any point of the mandible can be rec onstructed. The system permits a high sampling frequency of at least 3 00 Hz per photocell co-ordinate. The noise, linearity and accuracy are better than 0.08 mm, 0.07 mm and 0.13 mm for points in the lower inci sal region, and better than 0.25 mm, 0.17 mm and 0.27 mm for points in the condylar region. Thus jaw movements can be recorded with a high s patial and temporal resolution.