A HeNe laser position-detector for recording jaw movements: principle of operation and application in animal experiments

Abstract

A new equipment for recording jaw movements in animals by use of a HeNe laser and a phototransistor (PhT) array is described. The principle of operation of this equipment is that the beam angle of the HeNe laser is continuously controlled to irradiate the center of the PhT array by a feedback mechanism composed of a microcomputer (CPU) and XY scanners. The driving currents sent from the CPU to the XY scanners are utilized for monitoring two-dimensional jaw movements. The linearity of this recording system is preserved both vertically and horizontally over a range of 11 mm from the center of the scanning field of the laser beam within less than 1.5%, which is satisfactory for monitoring rabbit jaw movements. When this equipment was applied to the rabbit, there was no sign of disturbance to the animal during chewing carrots.