Ultrasonic measurement of air temperature along the axis of a laser beam during interferometric measurement of length

Authors:

• Marek Dobosz,
• Marek Ściuba

Abstract

An ultrasonic technique that allows compensation of air temperature changes and gradients along the beam axis of the laser interferometer during displacement measurement is presented. The system is based on using two ultrasonic paths parallel to the laser beam that operate at different frequencies and continuous waves emitted in opposite directions. The theoretical basis of the measurements is presented. To enable ultrasonic temperature measurement when the measuring reflector is moving, an iterative measurement algorithm is proposed. Experimental assessment of the accuracy of the method is presented. The effect of air temperature gradients along the laser beam axis is tested. The influence of air flow on the measurement accuracy is analyzed.