Three-dimensional measurement of an inner surface profile using a supercontinuum beam

Calibration for endoscopic 3D shape measurement with cone beam projection

We demonstrate a calibration method for endoscopic three-dimensional shape measurement with cone beam projection. In this method, changes in the shape of the optical sectioning profiles are quantified and fitted while scanning a calibration board in the depth direction, using a cubic function. In accuracy tests using a flat plate and a ring reference gauge, the proposed method obtains an accuracy of 0.02 mm in the depth dimension and 0.09 mm in the radial dimension. These results represent 88% and 55% improvements compared to previous analysis. For medical applications, an ear examination simulator was employed, and our measurement results were compared to ground truth data obtained by microfocus X-ray computed tomography. The surface deviation of our method relative to the ground truth data was ±0.36m m during manual operation. A comparison of the measurement results before and after calibration revealed an improvement in the peak agreement with the ground truth data, with the deviation shifting from 0.2 mm to -0.05m m. Our strategy achieves a digital transformation of 3D endoscopy, which would benefit a number of medical fields.

Lensless single-fiber ghost imaging

We demonstrate lensless single-fiber ghost imaging, which allows illumination and collection using a single optical fiber without a transmission-type system. Speckle patterns with relative coincidence degrees of 0.14 were formed by image reconstruction using improved differential ghost imaging. Employing fiber with a diameter of 105 µm, we achieved a spatial resolution of 0.05 mm in an observing area of 9m m 2, at a working distance of 10 mm. Compared to a conventional neuroendoscope at a power density of 94m W/c m 2, our imaging could be realized by extremely weak illumination at a laser power density of 0.10m W/c m 2. Using our lensless single-fiber ghost imaging, with 30,000 speckle patterns and implementing a diffuser, we attained an average coincidence degree of 0.45.

A three-dimensional reconstruction method for the inner surface of a deep hole using a rotating mechanism

An inner surface 3D reconstruction device structure is proposed in this paper to reconstruct the complex curved inner surface of a deep hole. First, the optical paths of the camera and the structured light transmitter are converged on the deep hole inner surface through plane mirrors to form a multi-line structured light projection system (MSLPS). The parameters of the MSLPS are then calibrated before the measurement. Second, the MSLPS rotates during the measurement process to obtain the point cloud collections of the inner surface and the rotation angles at different measurement positions are recorded. The point clouds contain the 3D surface information of the measured areas. Finally, the entire surface shape is reconstructed by the proposed reconstruction algorithm, and the feature parameters of the deep hole inner surface can be calculated by the reconstructed point cloud. The development process of the system was demonstrated in the experiment. The proposed system is validated through the reconstruction experiment of different areas in a deep hole.

Silicon twisted cone structure produced by optical vortex pulse with structure evaluation by radiation hydrodynamic simulation

We demonstrate a radiation hydrodynamic simulation of optical vortex pulse-ablated microcone structures on silicon (Si) substrates. Doughnut-shaped craters were formed by single pulse irradiation on the Si substrate, and a twisted cone structure with a height of 3.5 µm was created at the center of the irradiation spot by the circularly polarized optical vortex pulse. A two-dimensional (2-D) radiation hydrodynamic simulation reproduced the cone structure well with a height of 3 µm. The central part of the incident laser power was lowered from the initial profile due to plasma shielding over the laser pulse duration for an inverted double-well laser profile. The acute tip shape of the silicon surface can survive over the laser irradiation period.