Extending OCT into meter-scale working distances has potential applications in robotic vision, surgical planning and assistance, and non-invasive medical imaging. However, long-range imaging significantly decreases the numerical aperture (NA) of the system unless a much larger aperture is used. This diminishes the signal and requires the use of Gaussian beam theory for accurate determination of the beam profile and focusing behavior. We demonstrate and experimentally validate theory for focusing a laser source to optimize both resolution and signal and discuss the impact of the “focal shift” effect in which the geometric focus of the objective and Gaussian beam waist diverge at low NA.
In fields such as virtual/augmented reality, robotic vision, facial recognition, and biomedical imaging, the demand for accurate, fast coherent 3D surface imaging technology is increasing. However, current technologies like FMCW LiDAR have limitations in terms of low spectral bandwidth efficiency and high cost. We demonstrate a novel approach using synthetic wavelength phase unwrapping and line-scan off-axis holography. Our system achieved fast 3D surface imaging with a non-ambiguous depth range of 22.3mm. We validated system performance using a 3D-printed test target and a U.S. copper penny.
FMCW depth imaging is a coherent 3D imaging modality analogous to SS-OCT. Due to constraints of mechanical steering mirrors, meter-scale FMCW depth cameras typically suffer from low data rates (<1Hz 3D map rate). Here, we describe the design and construction of a high-speed FMCW depth camera that employs a grating for beam steering and a telescope for angular FOV magnification. Our camera produces 3D depth maps at 33Hz, each consisting of 475x500 pixels, spanning a depth range of 32.8cm with sub-millimeter depth localization accuracy. Our FMCW depth camera is suitable for room-scale real-time 3D imaging applications, particularly computer vision applications.
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