Determination of the origin position for an angle sensor with a femtosecond laser

This paper proposes a new optical angle sensor, in which a mode-locked femtosecond laser referred to as an optical frequency comb is employed as a light source. By using the optical frequency comb whose carrier frequency is well stabilized by using an external frequency standard with an uncertainty of 10^-11, both the sensor stability and the sensor sensitivity are expected to be improved. In this paper, a prototype optical sensor head with the femtosecond laser for the angle sensor is fabricated. Since the light wavelength of the femtosecond laser used in this paper is out of the visible range, a new alignment method using a retroreflector is introduced to determine the origin position of the angle sensor. In addition, some basic experiments are carried out to verify the feasibility of the developed angle sensor with the optical frequency comb.