Optical frequency domain angle measurement in a femtosecond laser autocollimator

Abstract

A mode-locked laser autocollimator, in which a group of first-order diffracted beams from a grating reflector are detected by an autocollimation unit, has an expanded angle measurement range compared with a conventional autocollimator using a single-wavelength laser source. In this paper, a new optical frequency domain angle measurement method is proposed to increase the visibility of output signal of the mode-locked femtosecond laser autocollimator, which is limited by the overlap of the focused diffracted light spots. The output visibility of a prototype femtosecond laser autocollimator has been increased by the proposed method to approximately 100% over a large range of 21600 arc-seconds.

Error compensation for long-distance measurements with a photoelectric autocollimator

“…7 Because the measurement range of the photoelectric autocollimator is closely related to the measurement distance, 8 long-distance and wide-range autocollimator has become a significant research focus in recent years. [9][10][11][12][13] Chen et al 12 proposed an angle measurement method based on optical frequency domain and realized a measurement range of 21,600 arc sec. Li et al 9 employed a cube corner as a reflector to extend the angle measurement range from 1.2 deg to 12 deg with an accuracy better than 35 arc sec.…”

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

“…2. Another drawback of the conventional optical angle sensors based on the laser autocollimation utilizing photodiodes is its narrow measurement range, which is determined by a diameter of the focused laser spot on the active cell in a photodiode, limited to the order of only 100 arc-seconds (Chen et al, 2017). 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). With the employment of a grating reflector, a measurement range has successfully been extended to larger than 11,000 arc-seconds while employing a photodiode as the photodetector.…”

“…With the employment of a grating reflector, a measurement range has successfully been extended to larger than 11,000 arc-seconds while employing a photodiode as the photodetector. Furthermore, a much wider measurement range of larger than 21,600 arc-second with an increased visibility of output signal of the femtosecond laser autocollimator has also been achieved by the optical frequency domain angle measurement method (Chen et al, 2017). Meanwhile, one of the drawbacks of the mode-locked laser autocollimator is that the employment of a high-precision reflective-type diffraction grating, which is to be mounted on a target of interest, is essential to obtain a group of the first-order diffracted beams required for the detection of angular displacement.…”