Abstract
A simultaneously high-precision, wide-range, and ultrafast time-resolution one-shot 3D shape measurement method is presented. Simultaneous times of flight from multiple positions to a target encoded in a chirped optical frequency comb can be obtained from spectral interferometry. We experimentally demonstrate a one-shot imaging profile measurement of a known step height of 480 µm with µm-level accuracy. We further demonstrate the extension of the dynamic range by measuring in one shot a large step height of 3 m while maintaining high accuracy using the accurate pulse-to-pulse separation of the optical frequency comb. The proposed method with its large dynamic range and measurement versatility can be applied to a broad range of applications, including microscopic structures, objects with large size or aspect ratio, and ultrafast time-resolved imaging. This study provides a powerful and versatile tool for 3D measurement, where various ranges of measurement performances can be tailored to demand.
Highlights
We proposed a novel principle for a one-shot 3D measurement method based on an ultrafast dimensional conversion between time, frequency, and space axis information encoded in chirped ultrashort pulses to capture dynamic 3D shapes[6]
Based on our previous chirp-imaging method’s principle[6], pulse-to-pulse interferometry using OFCs18 significantly extends the longitudinal measurement range based on high-precision pulse-to-pulse separation and could possibly break the fundamental trade-off in measurements to achieve extreme dynamic ranges that include the simultaneous imaging of separate targets with m-order distances without losing high precision
We proposed a new method to measure 3D shapes using one-shot imaging encoded in chirped optical frequency combs (OFCs)
Summary
We proposed a novel principle for a one-shot 3D measurement method based on an ultrafast dimensional conversion between time, frequency, and space axis information encoded in chirped ultrashort pulses to capture dynamic 3D shapes[6] This method was demonstrated using a highly chirped supercontinuum generated by an amplified Ti:Al2O3 laser and a femtosecond optical Kerr shutter to generate a real colour-coded 3D image in one pulse shot. Optical frequency combs (OFCs) have revolutionised frequency metrology[10, 11] and provided tools for the precise control of light waves with extreme accuracy This technology is useful in various application fields, including distance measurements with extreme accuracy and dynamic range[12,13,14,15]. In conventional spectral interferometry between the two chirp-free pulses, a uniform interference fringe spectrum is observed wherein the fineness of the fringe, i.e. the fringe frequency, is constant along the optical frequency (wavelength) and varies depending on the delay time between the two pulses (Fig. 1a,b)
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