Ultrahigh-Precision Flash 3D Velocity Imaging

We propose an ultrahigh-precision solid-state flash velocity imaging method based on optical coherent detection by leveraging mature charge-coupled device (CCD) sensors. In the proposed system, a high-speed MZM is employed to perform intensity modulation, generating an intensity-modulated optical signal. When the modulated optical signal illuminates a uniformly moving target, the reflected light is coherently detected with the local reference beam. The CCD camera captures the resulting intensity variations, producing a readout voltage with a fixed frequency component, from which the target's velocity can be extracted. An experimental demonstration is performed. The experimental results exhibit that a velocity measurement precision as high as 1 µm/s is achieved. The proposed velocity imaging system provides high-precision velocity measurement by directly leveraging established CCDs. This advancement is crucial for monitoring chip etching rates, thin-film growth rates, and the build rate of models during 3D printing.