Dynamic Spatial Filter for LiDAR Ambient Noise Rejection
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Solution Overview
Problem
Long-range LiDAR devices face challenges in detecting objects due to ambient light noise overshadowing reflected laser pulse signals, and existing noise rejection techniques are costly, inefficient, or not applicable to solid-state LiDAR systems.
Innovation Solution
A dynamic spatial filter is implemented in LiDAR devices, using technologies like liquid crystal displays or MEMS mirrors, to create a dynamically changing aperture that rejects ambient noise by aligning with the direction of laser pulse steering, enhancing the signal-to-noise ratio and allowing only desired signals to reach the photodetectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ambient light rejection techniques are applied to increase SNR, then detection range is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies a dynamic spatial filter that can change its aperture position and shape in real-time to match the moving laser beam position. This dynamic adaptation allows the filter to track the signal while rejecting ambient light, achieving high SNR without requiring complex fixed filtering structures for all possible beam positions.
Solution Approach 2:
The spatial filter creates a localized aperture only at the specific position where the laser beam is currently directed. Instead of using a complex filter structure across the entire detector array, the system applies filtering selectively only at the relevant local region, reducing overall device complexity while maintaining effective noise rejection.
2Measurement precision
If a spatial filter is used to reject ambient light, then signal-to-noise ratio is improved, but detection sensitivity is reduced
Solution Approach 1:
The spatial filter aperture dynamically tracks and follows the laser beam position throughout the scanning range. By maintaining the aperture at the correct position, the system ensures that reflected laser photons can pass through the filter and reach the detector, preserving detection sensitivity while still rejecting ambient light from other directions.
Solution Approach 2:
The system pre-calculates and positions the spatial filter aperture at the expected beam location before the beam arrives. This preliminary positioning ensures that the aperture is already in place to allow the signal through, preventing any loss of detection sensitivity while maintaining noise rejection throughout the scanning sequence.
3Ease of manufacture
If a fixed aperture spatial filter is used, then manufacturing is simplified, but adaptability to different scanning directions is lost
Solution Approach 1:
The spatial filter uses a programmable display device (such as an LCD or MEMS array) that can be electronically controlled to create apertures at different positions and orientations. This electronic programmability provides adaptability to various scanning directions and patterns without requiring physical reconfiguration or complex mechanical components, maintaining ease of manufacture while achieving versatility.
Solution Approach 2:
The programmable spatial filter serves multiple functions: it can create apertures at any position, adjust aperture size, and adapt to different scanning patterns. This single multi-functional component replaces what would otherwise require multiple fixed filters or complex mechanical adjustment mechanisms, achieving both ease of manufacture and adaptability.
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
This solution increases the detection range and sensitivity of LiDAR devices while reducing costs and improving accuracy, particularly in environments with vibrations, such as autonomous driving vehicles, by effectively filtering out ambient light and electronic noise.
Implementation Method 1
the spatial filter is implemented using a liquid crystal display (LCD) with multiple rows of segmented areas
Implementation Method 2
A LiDAR device can measure distances to objects in an environment by illuminating the objects with laser pulses and measuring reflected pulses from the objects
Data Source
AI summary
Embodiments of the invention disclose devices, methods, and computer media for noise rejections in a remote sensing device, such as a LIDAR device. In an exemplary embodiment, a spatial filter includes an aperture dynamically created in synchronization with one or more directions in which emitted laser pulses from the LiDAR device are steered. Photons from all other directions except the one or more directions are blocked by the spatial filter. Reflected photons from the one or more directions pass through the spatial filter via the aperture, and are projected on one or more sets of photodetectors. Noises in the photons that pass through the spatial filter are further to be rejected based on one or more fixed temporal patterns identified in laser pulses emitted by the LiDAR device. The spatial filter can be implemented using an electrochromic display, an array of micromechanical (MEMS) mirrors, a liquid crystal display (LCD), or an electro-wetting display.