High-precision Absolute Distance Measurements over a Long Range Based on Two Optoelectronic Oscillators

TL;DR

This paper introduces a novel high-precision absolute distance measurement method over long ranges using optoelectronic oscillators to convert distance into frequency information, achieving micrometer accuracy at several kilometers.

Contribution

The proposed scheme significantly enhances measurement precision by magnifying distance errors through frequency detection with two optoelectronic oscillators, surpassing traditional methods.

Findings

Maximum error of 1.5 micrometers at ~6 km distance

Achieved relative measurement precision of 2×10^10

Environmental factors limit current precision to about 4×10^9

Abstract

Absolute distance measurement (ADM) over a long range has been studied intensely over the last several decades, due to its important applications in large-scale manufacturing and outer space explorations [1-5]. Traditional absolute distance measurements utilize detection of time-of-flight information, detection of phase shift, or a combination of the two [6-17]. In this paper, we present a novel scheme for high-precision ADM over a long range based on frequency detection by using two optoelectronic oscillators (OEO) to convert distance information to frequency information. By taking advantage of accumulative magnification theory, the absolute error of the measured distance is magnified by about 2*10E5 times, which makes the precision of the measured distance significantly improved. In our experiments, the maximum error is 1.5 um at the emulated ~6 km distance, including the drift error of about 1 um in the air path due to the change in environmental conditions. In addition, the measurable distance using this scheme could be further extended. The highest relative measurement precision is 2*10E10 in our current system while the actual relative measurement precision of our experimental system is limited by the variation of atmospheric conditions and is about 4*10E9.