Dual-comb spectroscopy resolved three-degree-
of-freedom sensing
SIYU ZHOU,
1
VUNAM LE,
1
SHILIN XIONG,
1
YUETANG YANG,
1
KAI NI,
2
QIAN ZHOU,
2
AND GUANHAO WU
1,
*
1
State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument,
Tsinghua University, Beijing 100084, China
2
Division of Advanced Manufacturing, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
*Corresponding author: guanhaowu@mail.tsinghua.edu.cn
Received 19 October 2020; revised 17 December 2020; accepted 17 December 2020; posted 21 December 2020 (Doc. ID 412898);
published 1 February 2021
Precise and fast determination of position and orientation, which is normally achieved by distance and angle
measurements, has broad applications in aca demia and industry. We propose a dynamic three-degree-of-freedom
measurement technique based on dual-comb interferometry and a self-designed grating-corner-c ube (GCC) com-
bined sensor. Benefiting from its unique combination of diffraction and reflection characteristics, the absolute
distance, pitch, and yaw of the GCC sensor can be determined simultaneously by resolving the phase spectra of the
corresponding diffracted beams. We experimentally demonstrate that the method exhibits a ranging precision
(Allan deviation) of 13.7 nm and an angular precision of 0.088 arcsec, alongside a 1 ms reaction time. The pro-
posed technique is capable of precise and fast measureme nt of distances and two-dimensional angles over long
stand-off distances. A system with such an overall performance may be potentially applied to space missions,
including in tight formation-flying satellites, for spacecraft rendezvou s and docking, and for antenna measure-
ment as well as the precise manufacture of components including lithography machines and aircraft-
manufacturing devices.
© 2021 Chinese Laser Press
https://doi.org/10.1364/PRJ.412898
1. INTRODUCTION
Precise geometric metrology, including the determination of
positions and orientations, is essential to scientific research
[1–3], remote sensing [4], and advanced manufacturing proc-
esses [5]. At present, the most accurate method of geometric
measurement is based on interferometric phase measurement
[6]. In this case, the geometrical parameters can be directly
traceable to the wavelength of a continuous-wave (CW)
laser. The optical phase of the emitted laser beam accumulates
with the propagation of light waves and exhibits a period of 2π
rad, inducing phase wrapping ambiguity and hindering the ob-
servation of long-distance propagation. Therefore, to obtain
multiple integers of the unambiguous phase, the continuous
accumulation of instant phases based on incremental measure-
ments is required. To expand the range of unambiguity, either
the synthetic-wavelength method or the multiwavelength
method may be applied. However, they both require several
CW lasers, which encumber the system [7].
Over the past few decades, the advent of the optical-
frequency combs (OFCs) has provided discrete and uniform
mode-spacing narrow lines over wide spectra, constructing a
series of stable CW lasers in the frequency domain [8,9].
Various OFC-based methods have been develo ped for phase
measurement, e.g., the dispersive interferometr y method
[10,11], which uses the slope of the interferometric phase with
respect to the optical frequency; the inter-mode beat method,
which utilizes the harmonic phase of the pulse repetition rate
of the OFC [12]; the pulse alignment method, which sweeps
the pulse repetition rate [13]; and the dual-comb method
[14–16]. Among them, the dual-comb method exhibits the ad-
vantages of being dynamic, highly precise, and having a large
unambiguity range; therefore, it has been used as an efficient
tool in optical metrology [17,18]. Usually, phase information
is directly related to the distance of the target. In a multidimen-
sional free space, pitch and yaw also serve as critical parameters
that are used to determine the orientation of a target, e.g., the
orientation of a satellite within a formation [19] and the orien-
tations of constituent parts in aircraft assembly [ 20].
To realize high-precision distance and angle measurements,
several improved phase measurement principles have been pro-
posed, such as the multi-target interferometric method, the in-
terferometric and autocollimation combined method, the
Twyman–Green interferometer, and differential wavefront
sensing [21–30]. However, each of the four methods suffers
from particular shortcomings. Several targets need to be in-
stalled onto the target to be measured, and considerable distan-
ces need to be maintained between them to improve the
Research Article
Vol. 9, No. 2 / February 2021 / Photonics Research 243
2327-9125/21/020243-09 Journal © 2021 Chinese Laser Press