Laser Radar Stray Light Suppression via Inclined Window and Low Reflectance Mirror
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Solution Overview
Problem
Laser radar devices face issues with stray light detection, where projected light can be reflected by a window and then by a mirror, entering the detector and incorrectly determining the direction of a retroreflector, leading to ghosting errors.
Innovation Solution
A laser radar device design featuring a mirror with a low reflection area and an inclined window, where the mirror's low reflection area is positioned adjacent to the light source and window, and the window's inclination shifts the laser light's travel direction away from the mirror, reducing stray light intensity and minimizing the low reflection area to maintain signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light blocking section is used to suppress stray light, then stray light detection is reduced, but the device structure becomes more complex and the light blocking section may interfere with normal laser light transmission
Solution Approach 1:
The mirror surface is divided into a high reflectance region and a low reflectance region, where each region has different optical properties tailored to its specific function. The low reflectance region specifically targets stray light paths while the high reflectance region maintains normal laser light reflection, eliminating the need for separate light blocking sections.
Solution Approach 2:
The harmful stray light reflection function is extracted from the main mirror surface and assigned to a specific low reflectance region. This allows the majority of the mirror surface to maintain high reflectance for normal operation, while only the necessary portion has reduced reflectance for stray light suppression.
2Reliability
If the window is positioned closer to the light source, then stray light path length is reduced, but the detector receives less signal intensity
Solution Approach 1:
The window is positioned at an optimized distance from the light source that balances two competing requirements: being close enough to minimize stray light path length and reflection intensity, but far enough to allow sufficient signal intensity to reach the detector. This optimal positioning parameter resolves the contradiction between stray light suppression and signal maintenance.
3Reliability
If the low reflectance area is enlarged, then stray light suppression is improved, but the signal-to-noise ratio deteriorates due to reduced reflection of normal laser light
Solution Approach 1:
The mirror surface is segmented into regions with different reflectance properties: a high reflectance region for normal laser light operation and a specifically positioned low reflectance region for stray light suppression. This local differentiation allows the low reflectance area to be sufficiently large for stray light control while the high reflectance area maintains strong signal reflection, thereby preserving the signal-to-noise ratio.
Solution Approach 2:
The mirror surface is divided into functionally distinct segments: a high reflectance region that handles primary laser light reflection and a low reflectance region that handles stray light suppression. This segmentation allows each region to be optimized for its specific function without compromising the other, resolving the contradiction between stray light suppression effectiveness and signal-to-noise ratio maintenance.
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 solution effectively suppresses stray light detection, improving the signal-to-noise ratio by reducing the low reflection area's impact on normal laser light, thereby enhancing the accuracy of the laser radar device.
Implementation Method 1
a mirror rotatable about a rotation shaft to reflect the laser light emitted by the light source
Implementation Method 2
a window through which the laser light reflected by the mirror passes
Implementation Method 3
a detector configured to detect the laser light passing through the window to be reflected by the mirror
Data Source
AI summary
A laser radar device includes: a light source; a mirror rotatable about a rotation shaft to reflect laser light emitted by the light source; a window; and a detector to detect laser light. The mirror has a low reflection area having a lower reflectance than the other region of the mirror, in a state where a mirror surface faces toward the light source, at position adjacent to the light source than the detector in an axial direction of the rotation shaft and adjacent to the window than a region where the laser light emitted by the light source hits for a first time in a radial direction of the rotation shaft. The window has an inclined posture in which a distance from the rotation shaft is shorter at position adjacent to the detector than at position adjacent to the light source.