Multiple Harmonic Lissajous Scanning Patterns for Endomicroscopy With Parametrically-Resonant Micro-Mirrors

Parametrically-resonant micro-mirrors have proven highly effective in generating large amplitude, high-frequency motion for laser scanning in endoscopic microscopy, using Lissajous scan patterns to create a 2D image. However, Lissajous scanning produce low scanning density at the center of an image. In this work, a strategy for exciting additional harmonic behavior in a parametrically-resonant electrostatic micro-mirror is identified. The mirror’s nonlinear dynamics produce substantial changes in natural frequency with bias voltage. This allows a biased, duty-cycled square wave to produce higher harmonic oscillations that can be naturally synchronized with primary resonance in integer ratios. This in turn allows for alternate scanning distributions in 2D imaging that increase pixel sampling near the center of an image. In simulation, use of a biased square wave signal is found to be capable of producing steady-state oscillations at first and third harmonics of natural frequency for a micro-mirror operated via parametric resonance. Multiple harmonic motion is also realized without increasing input voltage amplitude beyond nominal amplitude, with a greater than 50% reduction fill time for the center of the imaging region. Parameterized relationships between input and output oscillations are identified, sensitivity of output trajectory to model variation, and impact on scanning density for a 2D MEMS micro-mirror are briefly described.

DESIGN AND IMPLEMENT OF A CONICAL AIRBORNE LIDAR SCANNING SYSTEM

At present, the main LiDAR is single-point lidar. APD arrays and laser arrays are restricted to exit, so the number of area array LiDAR is scarce. Single-point lidar can't form a scanning pattern with only one laser point on the ground after launching laser, so it must have a set of scanning device for single-point lidar. The scanning device designed in this paper forms a circular scanning area on the ground by rotating the refraction prism, and at the same time forms a conical field of view. At present, marine LiDAR uses this kind of scanner more frequently. The advantages of this scanner are: simple mechanical structure and smooth operation. Overlapping elliptical scanning trajectories can be obtained during flight, which increases scanning density. Ultra-low dispersion glass is used as refractive prism in this paper. In a certain range of laser frequencies, the refractive prism has almost the same effect on laser refraction at different frequencies. The simulation results show that the scanner can be used as a common LiDAR scanner or a dual-frequency LiDAR scanner.

Consideration of Scanning Line Density and Capture of Shape of Human Movement from 3D Laser Scanning Sensor Using Roundly Swinging Mechanism

A 3D SOKUIKI sensor (3D laser scanning sensor) with a roundly swinging mechanism can detect the range distance of a belt area at a certain vertical height and horizontal view angle without any converging points and without twisting any signal cables. It is useful for observing the movement of people and for capturing the shape of human movement. We analyzed the line-to-line distance as the scanning line density for this type of sensor. The entire belt area of directions is scanned twice by both positively and negatively inclined scanning lines in one period of a whole scan. The line-to-line distance depends on the vertical height and is dense at both vertical ends and sparse in the middle. As a result, the scanning density at center front is 1/2.5 (40%) compared to using ideal vertical direction control. Since ideal vertical direction control of a range-measuring beam is not technically possible at this time, this scanning density provided by the roundly swinging mechanism can be considered to be reasonably good and useful. The 3D SOKUIKI sensor using this roundly swinging mechanism can capture the shape of human movement.