Mirror Device With Flattened Drive Coil for LiDAR
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Solution Overview
Problem
Existing mirror devices for LiDAR systems face a trade-off between increasing the detection range and deflection angle, as widening the reflective area leads to increased weight and reduced deflection angle, making it difficult to achieve compatibility between both.
Innovation Solution
A mirror device with a support substrate of a frame form, a movable portion inside the frame, first torsion bars connecting the movable portion to the substrate, a first drive coil wound on the peripheral edge, and a smoothing layer on the front surface to flatten the area and accommodate a large-area reflective layer without increasing the weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the area of the reflective layer is increased to widen the detection range, then the detection range is improved, but the weight of the movable portion increases and the deflection angle decreases
Solution Approach 1:
The drive coil is wound in a spiral pattern starting from the center toward the periphery of the movable portion, utilizing the radial dimension to maximize the effective area for light reflection without proportionally increasing the peripheral weight. This dimensional arrangement allows the reflective layer to cover a larger area while the drive coil remains compact and centrally located.
Solution Approach 2:
The drive coil is divided into multiple turns wound in a spiral pattern, with each turn contributing to the magnetic field generation at different radial positions. This segmentation allows the coil to generate sufficient magnetic field across the entire area of the reflective layer without requiring a single large coil that would increase the peripheral weight and reduce deflection angle.
2Area of stationary object
If the area of the reflective layer is increased to widen the detection range, then the detection range is improved, but the deflection angle decreases due to increased moment of inertia
Solution Approach 1:
By arranging the drive coil in a spiral pattern from the center outward, the design utilizes the radial dimension to maximize the reflective area coverage while keeping the coil's moment of inertia low. The coil turns are concentrated toward the center where they generate magnetic field most effectively for driving the mirror, rather than being distributed uniformly across the periphery.
Solution Approach 2:
The drive coil generates magnetic field locally at each radial position where it is wound, with the density and distribution of coil turns optimized for local effectiveness. The spiral pattern ensures that magnetic field is generated uniformly across the entire reflective area, providing localized driving force at each position to maintain deflection angle while covering maximum area.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables a large-area reflective layer without increasing the weight of the movable portion, allowing for a wider deflection angle and increased detection range while maintaining structural integrity.
Implementation Method 1
The drive coil is disposed in a direction perpendicular to a magnetic field, and when current is caused to flow through the drive coil, a force is applied to the drive coil. The force is called a Lorentz force, and the magnitude thereof is proportional to the intensity of current and magnetic field.
Implementation Method 2
The torsion bars, as well as being the rotation shaft of the mirror, act as torsion springs which suppress the rotation of the mirror. When current flows through the drive coil on the periphery of the mirror, the elastic force of torsion springs generated by the torsion bars, together with a torque which causes the mirror to rotate, works in a direction opposite to the rotation, and the rotation of the mirror stops when the two forces balance with each other.
Implementation Method 3
a reflective layer acting as the mirror is provided in the center of the movable portion
Data Source
AI summary
In order to expand the surface area of a reflective layer, the space between adjacent turns of a drive coil, which is wound a plurality of turns on a peripheral edge front surface of the principal surface of a movable portion which, being inside a frame-formed support substrate, is connected to the support substrate by torsion bars, is filled and flattened with a smoothing layer, thereby adopting a configuration such that the reflective layer can also be provided in the region of the upper surface of the drive coil.