Simultaneous Distance Measurements Research Articles

Multi-Band Radar Based on a Cavity-Less Ultra-Short Optical Pulse Source for Simultaneous Measurement of Distance and Velocity

Multi-Band Radar Based on a Cavity-Less Ultra-Short Optical Pulse Source for Simultaneous Measurement of Distance and Velocity

Refractivity corrected distance measurement using the intermode beats derived from a supercontinuum.

Simultaneous distance measurements on two or more optical wavelengths enable dispersion-based correction of deviations that result from insufficient knowledge of the refractive index along the signal propagation path. We demonstrate a supercontinuum-based approach for highly accurate distance measurements suitable for such an inline refractivity compensation. The distance is estimated from the phase delay observations on the intermode beats. We use a supercontinuum (SC) coherently broadened from a 780 nm frequency comb and spanning the spectral range of 570-970 nm. Experiments are performed on the 590 and 890 nm wavelength bands filtered from the SC spectrum. Results show distance measurements with standard deviations of around 0.01 mm at 50 m, and a distance-dependent component below 0.2 ppm on the individual spectral bands. Distance residuals compared to a reference interferometer are on the order of 0.1 ppm for displacements up to 50 m. Controlled pressure-induced refractivity variations are created over a length of 15 m, resulting in an optical path length change of 0.4 mm. Using the two-color method, we demonstrate refractivity-corrected distance measurement with a standard deviation of around 0.08 mm for a 60 s averaging window. The current experimental configuration can be easily extended to distance measurements on more than two wavelengths. The results highlight its potential for practical long-distance measurements through inline refractivity compensation.

Simultaneous measurement of distance and speed using frequency-modulated continuous-wave self-mixing interferometry and all-phase fast Fourier transform

Simultaneous measurement of distance and speed using frequency-modulated continuous-wave self-mixing interferometry and all-phase fast Fourier transform

Frequency scanning interferometry based deformation monitoring system for the alignment of the FCC-ee machine detector interface

In a particle accelerator, two particle beams are accelerated and collided at one or several physics detectors. The machine detector interface (MDI) is the place where the accelerator ring is linked to the physics detector. It is the area where the alignment requirements are the most stringent, and the MDI of the lepton version of the future circular collider (FCC-ee) is no exception. It will implement a complex design and alignment requirement for typical components in the MDI are of the order of 30 μm. Until now, no working solutions have been proposed for the alignment of such MDI. In this contribution, two different systems are studied: the Surveillance d’Ouvrages par Fibre Optique (Structural Monitoring by Optical Fibers, SOFO) and the in-lined multiplexed and distributed frequency scanning interferometry (FSI). Both systems allow individual and simultaneous distance measurements of multiple portions along a fiber, and a new system using the FSI technology is proposed for the alignment monitoring. Using a network of helical shaped fiber allows the measurement of deformations if a sufficient amount of fibers is placed on the cylinder. With a sensor measurement accuracy of 1 μm, 3D coordinates of points at the end of a 4 m long and 0.25 m radius cylinder (FCC-ee MDI dimensions) can be determined at an accuracy under 5 μm. This system will provide a link between the alignment of the final focusing quadrupoles and the rest of the machine.

Simultaneous distance measurement and information transmission in mobile environment using digital acoustic communication

The purpose of this paper is to examine the feasibility of indoor acoustic positioning by measuring transmission distance and speed while simultaneously transmitting information using digital acoustic communication. The method we propose applies orthogonal signal division multiplexing, computes the channel impulse response in the delay-Doppler domain, and calculates the moving speed of the receiver and the time of flight to estimate the distance between the transmitter and receiver. Experiments confirm that the proposed method can estimate relative velocity and distance with errors of up to 6 mm s−1 and 34 mm, respectively, even when the signal power-to-noise power ratio drops to about 0 dB, while transmitting messages of up to 254 bits.

Dynamic absolute distance measurement with nanometer-precision and MHz acquisition rate using a frequency comb-based combined method

Distance metrology is crucial in supporting modern science and technology such as satellites interconnection, autonomous driving, motion control, and precision manufacturing. A combined method, which is a simultaneous distance measurement with multiple methods, was developed and widely utilized to increase the measurable range while maintaining high precision. However, the measurement speed has been limited to a few kHz due to the requirement for combining a precision measurement with a long-range measurement. In this work, we present a new dynamic distance measurement method based on electro-optic sampling timing detection (EOS-TD) that can preserve the non-ambiguity range (NAR) extension even at >1 MHz acquisition rate. By combining the EOS-TD-based pulse time-of-flight detection method with a microwave phase detection method, 300-mm NAR and 49-nm precision are made possible at 1-μs acquisition time. With longer averaging time, the best precision of 0.99 nm is achieved at 0.22-s acquisition time, corresponding to 169 dB maximum dynamic range. As a demonstration experiment, two mirrors that were ∼83 mm apart and each controlled by a piezo actuator with hundreds of nanometers of displacement variations had their distance between them precisely measured.

Simultaneous measurement of distance and speed via frequency-modulated continuous-wave LIDAR system based on H13C14N gas cell

• Simultaneous and accurate measurement of distance and speed with frequency-modulated continuous-wave laser. • The traditional method of finding the measurement signal's frequency by Fourier transform is replaced. • Accurately fitting the relationship between the phase of the beat signal and the frequency of tunable laser according to the characteristics of the gas absorption cell. • Up and down-scanning frequency rate are obtained by Fabry Perot cavity. • The measurement signal's frequency is obtained by fitting relationship result and frequency rate. Traditional frequency-modulated continuous-wave lidar is to measure the distance of the target through the spectrogram of the beat signal. In this paper, we propose a lidar system to obtain distance and speed at the same time. The distance and speed of the moving target are extracted by product of the delay time obtained by H 13 C 14 N standard gas cell and the fitting frequency modulation rate obtained by Fabry Perot cavity, which can avoid spectral broadening. The experimental results show that the speed resolution of the system was 10µm/s, the mean error of the speed measurement from 0.1mm/s to 100mm/s was less than 162µm/s, and the mean standard deviation was less than 523µm/s. When the speed was less than 10mm/s and the distance was about 4.5m, the mean standard deviation of the distance was less than 163µm. With the advantages of light computation requirements, a simple optical path and measurement results with good repeatability and accuracy, this system has high practical value in precision industrial manufacturing.

Photonics-based simultaneous measurement of distance and velocity using multi-band LFM microwave signals with opposite chirps.

We propose and demonstrate a photonics-based method for simultaneously measuring distance and velocity by adopting multi-band linear-frequency-modulated microwave signals with opposite chirps as transmitted signals. A dual-drive Mach-Zehnder modulator and photodetector (PD) are used to mix transmitted and echo signals. By analyzing the electrical spectra of the electrical signals generated by the PD, distance and the magnitude and direction of velocity can be derived simultaneously, which is significant for real-time radar applications. Proof-of-concept experiments using the proposed approach are also presented. The measured relative errors for distance and velocity are less than 0.005% and 0.59%, respectively.

Simultaneous distance measurement at multiple wavelengths using the intermode beats from a coherent supercontinuum

Advances in ultrashort pulse lasers and spectral manipulation enable new approaches to metrological problems in various fields. Dimensional metrology may benefit particularly from this progress, including applications like long distance measurement and 3D laser scanning. Using the intermode beat notes obtained by direct photodetection of a mode-locked femtosecond laser has been demonstrated as a promising alternative to solutions based on actively modulated signals. In this work, we extend the approach to ultra-broadband sources derived from femtosecond lasers, aiming at investigating their potential as a technological basis for multiwavelength distance metrology. We have developed a short-distance experimental set-up for displacement measurement operating simultaneously at two wavelength ranges on both extremes of a 500 nm coherent supercontinuum. The results derived from the phases of the 1 GHz intermode beat notes show that the internal coherence of the source is sufficient to derive distances with an accuracy better than 50 μm. This is a promising first step for the prospective application of this method to develop spectrally-versatile solutions, which is of interest to provide surface material probing capabilities in laser scanning and to increase the accuracy of long distance measurement though dispersion-based refractivity compensation.

Simultaneous distance measurement at multiple wavelengths using the intermode beats from a femtosecond laser coherent supercontinuum

The intermode beats generated by direct detection of a mode-locked femtosecond laser represent inherent high-quality and high-frequency modulations suitable for electro-optical distance measurement (EDM). This approach has already been demonstrated as a robust alternative to standard long-distance EDM techniques. However, we extend this idea to intermode beating of a wideband source obtained by spectral broadening of a femtosecond laser. We aim at establishing a technological basis for accurate and flexible multiwavelength distance measurement. Results are presented from experiments using beat notes at 1 GHz generated by two bandpass-filtered regions from both extremes of a coherent supercontinuum ranging from 550 to 1050 nm. The displacement measurements performed simultaneously on both colors on a short-distance setup show that noise and coherence of the wideband laser are adequate for achieving accuracies of about 0.01 mm on each channel with a potential improvement by accessing higher beat notes. Pointing and power instabilities have been identified as dominant sources of systematic deviations. Nevertheless, the results demonstrate the basic feasibility of the proposed technique. We consider this a promising starting point for the further development of multiwavelength EDM enabling increased accuracy over long distances through dispersion-based integral refractivity compensation and for remote surface material probing along with distance measurement in laser scanning.

Spinning-rate encoded chemical shift correlations from rotational resonance solid-state NMR experiments

Structural measurements in magic-angle-spinning (MAS) solid-state NMR rely heavily on 13C–13C distance measurements. Broadbanded recoupling methods are used to generate many cross-peaks, but have complex polarization transfer mechanisms that limit the precision of distance constraints and can suffer from weak intensities for distant peaks due to relaxation, the broad distribution of polarization, as well as dipolar truncation. Frequency-selective methods that feature narrow-banded recoupling can reduce these effects. Indeed, rotational resonance (R2) experiments have found application in many different biological systems, where they have afforded improved precision and accuracy. Unfortunately, a highly selective transfer mechanism also leads to few cross-peaks in the resulting spectra, which complicates the extraction of multiple constraints. R2-width (R2W) measurements that scan a range of MAS rates to probe the R2 matching conditions of one or more sites can improve precision, and also permit multiple simultaneous distance measurements. However, multidimensional R2W can be very time-consuming. Here, we present an approach that facilitates the acquisition of 2D-like spectra based on a series of 1D R2W experiments, by taking advantage of the chemical shift information encoded in the MAS rates where matching occurs. This yields a more time-efficient experiment with many of the benefits of more conventional multidimensional R2W measurements. The obtained spectra reveal long-distance 13C–13C cross-peaks resulting from R2-mediated polarization transfer. This experiment also enables the efficient setup and targeted implementation of traditional R2 or R2W experiments. Analogous applications may extend to other variable-MAS and frequency-selective solid-state NMR experiments.

Scanning delay line with a rotating-parallelogram prism for low-coherence interferometry

We describe a fast scanning optical delay line for low-coherence interferometry that has good linearity, a high duty cycle, and a continuously adjustable scan range. The delay line consists of a rotating-parallelogram prism with the rotation axis tilted with respect to the incident beam and two motionless mirrors. The delay line is well suited for nearly simultaneous distance measurements at two different depths, which is useful for making absolute and differential distance measurements.

Development of High-Speed 3-D Range Finder Using Binocular Cameras.

Many types of devices have already been presented for obtaining 2-D scene information ; however, there are only a few devices for obtaining 3-D distance image, and a low-cost and high-speed device has not yet been developed to date. In this paper a high-speed acquisition system of distance image has been developed with the intent of the future industrial application. The device manufactured for trial, which receives the video images obtained by binocular cameras, can detect many characteristic points within each horizontal scanning line and find corresponding points, simultaneously leading to the output of parallax image. This output can be used as the distance signal as it is, thereby enabling the high-speed measurement of 3-D distance image. This high-speed function will lead to applications in that the device is applicable to not only the simultaneous measurements of distance and image but also the robot technologies, as well as the eyes of unmanned equipments and blind people. Some application tests to evaluate its characteristics showed that sufficient accuracy was attained in the distance measurement and the high practicability was confirmed.