Fast Synchronization Method of Comb-Actuated MEMS Mirror Pair for LiDAR Application

MEMS-based LiDAR (micro-electro–mechanical system based light detection and ranging), with a low cost and small volume, becomes a promising solution for the two-dimensional (2D) and three-dimensional (3D) optical imaging. A semi-coaxial MEMS LiDAR design, based on a synchronous MEMS mirror pair, was proposed in our early study. In this paper, we specifically reveal the synchronization method of the comb-actuated MEMS mirror pair, including the frequency, amplitude, and phase synchronization. The frequency sweeping and phase adjustment are simultaneously implemented to accelerate the MEMS mirror synchronization process. The experiment is set up and the entire synchronization process is completed within 5 s. Eventually, a one-beam MEMS LiDAR system with the synchronous MEMS mirror pair is set up and a LiDAR with a field of view (FOV) of 60°, angular resolution of 0.2°, and frame rate of 360 Hz is obtained. The experimental results verify the feasibility of the MEMS mirror synchronization method and show a promising potential application prospect for the MEMS LiDAR system.

Tropical Lagrangians in toric del-Pezzo surfaces

We look at how one can construct from the data of a dimer model a Lagrangian submanifold in $$(\mathbb {C}^*)^n$$ ( C ∗ ) n whose valuation projection approximates a tropical hypersurface. Each face of the dimer corresponds to a Lagrangian disk with boundary on our tropical Lagrangian submanifold, forming a Lagrangian mutation seed. Using this we find tropical Lagrangian tori $$L_{T^2}$$ L T 2 in the complement of a smooth anticanonical divisor of a toric del-Pezzo whose wall-crossing transformations match those of monotone SYZ fibers. An example is worked out for the mirror pair $$(\mathbb {CP}^2{\setminus } E, W), {\check{X}}_{9111}$$ ( CP 2 \ E , W ) , X ˇ 9111 . We find a symplectomorphism of $$\mathbb {CP}^2{\setminus } E$$ CP 2 \ E interchanging $$L_{T^2}$$ L T 2 and a SYZ fiber. Evidence is provided that this symplectomorphism is mirror to fiberwise Fourier–Mukai transform on $${\check{X}}_{9111}$$ X ˇ 9111 .

A micro-focusing and high-flux-throughput beamline design using a bending magnet for microscopic XAFS at the High Energy Photon Source

An optical design study of a bending-magnet beamline, based on multi-bend achromat storage ring lattices, at the High Energy Photon Source, to be built in Beijing, China, is described. The main purpose of the beamline design is to produce a micro-scale beam from a bending-magnet source with little flux loss through apertures. To maximize the flux of the focal spot, the synchrotron source will be 1:1 imaged to a virtual source by a toroidal mirror; a mirror pair will be used to collimate the virtual source into quasi-parallel light which will be refocused by a Kirkpatrick–Baez mirror pair. In the case presented here, a beamline for tender X-rays ranging from 2.1 keV to 7.8 keV, with a spot size of approximately 7 µm (H) × 6 µm (V) and flux up to 2 × 1012 photons s−1, can be achieved for the purpose of X-ray absorption fine-structure (XAFS)-related experiments, such as scanning micro-XAFS and full-field nano-XAFS.