Lidar Window Reflection Subtraction for Near Range Detection
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Solution Overview
Problem
Traditional lidar systems face challenges in accurately detecting objects at close ranges due to the reflection of light from the front glass window, which causes interference and makes it difficult to distinguish between window reflections and downrange objects.
Innovation Solution
The implementation of an Optical T0 reference subtraction technique, where a reference scan with no objects in front of the window is subtracted from the received signal to remove the window reflection, allowing for the detection of objects as close as zero meters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional lidar systems are used to detect objects at close ranges, then the system can measure distances to remote targets, but the reflection of light from the front glass window causes interference and makes it difficult to distinguish between window reflections and downrange objects
Solution Approach 1:
The system performs a reference scan before object detection to capture the window reflection signature in advance. This preliminary measurement of the interference pattern allows the system to subsequently subtract the window reflection from the received signal, enabling accurate detection of objects at close ranges that would otherwise be obscured by the window reflection interference
Solution Approach 2:
The system converts the harmful window reflection into a useful reference signal. By capturing and storing the window reflection signature during a reference scan, the system transforms the interference into a known pattern that can be subtracted from subsequent measurements, thereby eliminating the harmful effect and enabling near-range object detection
2Length of stationary object
If the lidar system attempts to detect objects at very close ranges, then the minimum ranging capability improves, but the window reflection interference increases and obscures the detection signal
Solution Approach 1:
The system extracts the window reflection component from the total received signal through subtraction. By removing the identified window reflection signature from the composite signal containing both window reflection and object return, the system isolates the object detection signal, thereby improving signal clarity and enabling detection at minimum range of zero meters
3Measurement precision
If the system uses reference scan subtraction to remove window reflection, then near-range object detection is enabled, but the system complexity increases due to additional processing requirements
Solution Approach 1:
The system creates a digital copy of the window reflection signature during a reference scan and stores it for subsequent subtraction operations. This copying approach allows the system to eliminate window reflection interference through simple digital signal subtraction rather than requiring complex optical filtering hardware, thereby achieving near-range detection capability with moderate processing complexity
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 technique enables accurate detection and classification of objects, including blockages on the window and nearby objects, by effectively removing the window reflection interference, thus improving the minimum ranging capability to 0 meters.
Implementation Method 1
The light source emits light towards a target which scatters the light, and some of the scattered light is received back at the receiver
Implementation Method 2
The system determines the distance to the target based on one or more characteristics associated with the received light. For example, the lidar system may determine the distance to the target based on the time of flight for a pulse of light emitted by the light source to travel to the target and back to the lidar system
Implementation Method 3
Traditional lidar systems face challenges in accurately detecting objects at close ranges due to the reflection of light from the front glass window
Data Source
AI summary
In the present application, a lidar system is disclosed. The system comprises a light source configured to emit an output beam comprising a plurality of light pulses through a window. The system comprises a receiver configured to detect a reference signal, the reference signal corresponding to one of the plurality of light pulses reflected from the window. The receiver is configured to detect a received signal, the received signal comprising a signal portion corresponding to one of the plurality of light pulses scattered by a target located at a distance. The system comprises a processor configured to determine the distance to the target using the received signal, including by being configured to subtract the reference signal from the received signal.