Patterned Mirror Edge for LiDAR Stray Beam Mitigation
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Solution Overview
Problem
LiDAR devices face interference from stray light or glare, which can impinge on the optical sensor and degrade the signal/noise ratio, especially when the glare beam diffracts from the edge of the folding mirror and interferes with the detection of return signals from the target scene.
Innovation Solution
The implementation of a diffractive structure along the outer edge of the central region of the mirror or a peripheral region with decreasing optical density to deflect or attenuate the glare beam away from the optical sensor, preventing diffraction and improving the signal/noise ratio in LiDAR devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional mirror edge is used, then the device structure is simple, but stray light diffracts from the edge and interferes with the optical sensor
Solution Approach 1:
The mirror is divided into a central reflective region and a peripheral region with different optical properties. The peripheral region has decreasing optical density from inner to outer edges, creating a gradient that locally modifies light interaction to prevent stray light diffraction while maintaining the overall mirror function
Solution Approach 2:
The peripheral region acts as an intermediary between the central reflective region and the surrounding environment. It gradually transitions the optical density to prevent abrupt diffraction at sharp edges, effectively mediating the light path to avoid sensor interference
2Reliability
If the peripheral region width is increased to reduce glare, then stray light attenuation improves, but the mirror area available for reflection decreases
Solution Approach 1:
The optical density parameter is varied continuously across the peripheral region, creating a gradient that transitions from high reflectivity near the center to low reflectivity at the outer edge. This allows the peripheral region to be effective at glare suppression while minimizing the impact on the central reflective 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
The described solutions effectively reduce or eliminate glare impinging on the optical sensor, enhancing the signal/noise ratio and enabling the fabrication of high-quality optical sensing devices by directing diffracted glare away from the sensor or attenuating it to prevent interference.
Implementation Method 1
a diffractive structure, which is disposed along an outer edge of the central region and is configured to diffract the light that is reflected back by the one or more optical surfaces of the output optic toward the mirror and is incident on the diffractive structure so that the incident light that is diffracted by the structure is deflected away from the axis
Implementation Method 2
having an optical density that decreases smoothly in a radial direction over the width. Typically, the width and optical density of the peripheral region are selected so that the light that is reflected back by the one or more optical surfaces of the output optic toward the mirror and is incident on the peripheral region is attenuated and not diffracted
Data Source
AI summary
A method for optical sensing includes providing a mirror comprising a central reflective region surrounded by a peripheral glare-suppressing region. A beam of light from a laser light source is directed to reflect from the central region so as to pass through an output optic along an axis toward a target scene. The light returned from the target scene through the output optic is focused onto an optical sensor, via collection optics having a collection aperture surrounding the mirror.