Determination of the zero-position for an optical angle sensor

Abstract

This paper proposes a new optical angle sensor, in which a mode-locked femtosecond laser referred to as the optical frequency comb is employed as the light source for the sensor. By using the optical frequency comb, whose carrier frequency is well stabilized by using an external frequency standard with the uncertainty of 10-11 , both the sensor stability and the sensor sensitivity are expected to be improved. In this paper, the angle error caused by the frequency fluctuation of the laser beam is considered in the case of both the mode-locked femtosecond laser and a laser diode, which is a conventional light source for the optical angle sensor. A prototype optical sensor head with the mode-locked femtosecond laser is then fabricated for the angle sensor. Since the light wavelength of the mode-locked femtosecond laser used in this paper is out of the visible range, an alignment method based on laser autocollimation with a retroreflector is introduced to determine the zero-position for the angle sensor. This method is also effective in suppressing the influence of the alignment error such as a cosine error. Some basic experiments are carried out to verify the feasibility of the developed angle sensor with the optical frequency comb.

Evaluation of the grating period based on laser diffraction by using a mode-locked femtosecond laser beam

“…By using the developed optical setup, experiments were carried out to demonstrate the feasibility of the proposed femtosecond laser diffraction method. At first, the Littrow configuration in the zeroth-order was determined by using a retroreflector (Tamada et al, 2016). The retroreflector was mounted on the precision air-bearing spindle on behalf of the diffraction grating, and the femtosecond laser beam was made incident to the retroreflector.…”

High Resolution Clinometers for Measurement of Roll Error Motion of a Precision Linear Slide

“…Especially, autocollimators are often employed in the manufacturing process of linear slides since they can continue their measurement even if their measurement laser beams are interrupted by operators for the hand scraping process. In addition, autocollimators have advantage of high measurement resolution on the order of sub arc-second [17][18][19][20][21]. In the case of measuring the yaw error motion by using an autocollimator, a small mirror reflector will be mounted on a slide table, while an optical sensor head of the autocollimator will be aligned in such a way that the optical axis will be parallel with the motion axis of the slide table.…”

An optical angle sensor based on chromatic dispersion with a mode-locked laser source

“…Meanwhile, recently, a mode-locked laser often referred to as the optical frequency comb (Holzwarth et al, 2000) is attracting much attentions in many scientific and industrial fields (Tan et al, 2005;Moreaux et al, 2000;Kim, 2009;Chong et al, 2008;Minoshima et al, 2000) due to its precise and highly stable optical frequencies. To overcome the above mentioned drawbacks of the conventional optical angle sensor based on the laser autocollimation employing photodiodes and a laser diode, an attempt has been made to employ a mode-locked femtosecond laser beam as the light source for the optical angle sensor (Tamada et al, 2016). In addition, a femtosecond laser autocollimator, which employs a femtosecond laser source as the light source for the laser autocollimator, has also been developed (Chen et al, 2017).…”