#Train simulator 2019 jittering update
The performance of ASOPS based high speed ranging applications, say, at ~kHz update rate, is determined by short term stability of femtosecond lasers on the time scale of ~millisecond. Several groups have demonstrated micrometer precision TOF ranging at several kilohertz update rate using a pair of incoherent femtosecond lasers. For the sake of industrial applications, where a simple setup and high speed measurement are always preferred, the sophisticated phase-locking between the two optical combs is not required because the ranging precision at high update rate is only determined by the TOF measurement using pulse envelope. Note that the unprecedented performance relies on tight phase locking of the comb teeth to a common optical standard, and the nanometer precision is achieved by coherent averaging.
have demonstrated 5 nm precision in an 1.5 m ambiguous range when a pair of tightly phase locked optical frequency combs are employed. The capability of femtosecond laser based distance measurements can be further advanced by an asynchronous optical sampling (ASOPS) implementation, where a slight repetition rate difference between the two femtosecond lasers allows for rapid update rate against multiple targets with an extended ambiguity range up to pulse train spacing. In addition, a transition from incoherent, TOF measurement to coherent, fringe-resolved interferometry can be achieved by taking advantage of a phase-stabilized optical frequency comb from a passively mode-locked femtosecond laser, resulting in wavelength resolution over arbitrary range. Alternatively, the optical cross correlation between the target-reflected pulses and reference pulses can function as a timing gate providing sub-femtosecond temporal resolution. utilized a set of radio frequency (RF) harmonics encoded in the femtosecond laser pulse train for an absolute distance measurement in a 240 m tunnel. The precision of TOF distance measurements can be significantly improved by using passively mode-locked lasers, which emit a uniformly spaced pulse train with typical pulse duration down to tens of femtoseconds. Time-of-flight (TOF) of pulsed lasers allows for non-contact absolute distance measurements at long ranges, enabling a number of applications, such as altimeter, terrain mapping and surface profilometry of large-scale structures. The comparison between experiment and numerical model shows that the quantum-limited timing jitter of femtosecond lasers sets a fundamental limit on the performance of dual femtosecond laser TOF distance measurements. The timing jitter of the lasers is also characterized by an attosecond resolution balanced optical cross correlation method.
#Train simulator 2019 jittering free
Finally, the analytical and numerical models are verified by a TOF ranging experiment using a pair of free running femtosecond Er-fiber lasers. A numerical study is conducted by involving typical timing jitter sources in femtosecond lasers in the following. An analytical model governing dual femtosecond laser TOF distance measurement in the presence of pulse train timing jitter is built at first. Here, we investigate the obtainable ranging precision set by the timing jitter from femtosecond lasers. The cross correlation between a pair of femtosecond lasers with slightly different repetition rates enables high precision, high update rate time-of-flight (TOF) distance measurements against multiple targets. Note: Author names will be searched in the keywords field, also, but that may find papers where the person is mentioned, rather than papers they authored.Use a comma to separate multiple people: J Smith, RL Jones, Macarthur.Use these formats for best results: Smith or J Smith.For best results, use the separate Authors field to search for author names.
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