Lidar Receiver Photodetector Segmentation for Dazzle Signal Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lidar devices face challenges in detecting near-field objects due to internal reflections and stray light, known as 'dazzle' signals, which saturate the receiver and prevent accurate detection of objects close to the device.
Innovation Solution
A pair of photodetectors in the receiver is used to differentiate between dazzle signals and valid return signals, with the second photodetector unable to detect the valid return signal, allowing for the subtraction of dazzle effects, thereby preventing receiver saturation and improving near-field object detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single photodetector is used to receive return signals, then the receiver can detect all optical signals including valid return signals, but the receiver becomes saturated by dazzle signals (internal reflections and stray light) from near-field objects
Solution Approach 1:
The receiver is segmented into two separate photodetectors: a first photodetector that receives both valid return signals and dazzle signals, and a second photodetector that receives only dazzle signals. This segmentation allows the system to separately measure and subsequently subtract the dazzle component from the total signal, preventing receiver saturation and enabling accurate near-field object detection.
Solution Approach 2:
The second photodetector acts as an intermediary that specifically measures the dazzle signal component. By using this intermediate measurement, the system can subtract the dazzle contribution from the first photodetector's output, effectively isolating the valid return signal and preventing saturation effects.
2Length of moving object
If the receiver attempts to detect objects at very close range, then near-field detection capability is improved, but internal reflections and stray light saturate the receiver preventing accurate detection
Solution Approach 1:
The receiver is divided into two photodetectors with different reception characteristics. The first photodetector captures the full signal (valid return + dazzle), while the second photodetector captures only the dazzle signal. This segmentation enables mathematical separation of the signal components, allowing reliable detection at minimum distances of 10 cm or less where dazzle signals would otherwise cause saturation.
Solution Approach 2:
The dazzle signal component is extracted through the second photodetector and then subtracted from the total signal received by the first photodetector. This extraction process removes the harmful dazzle contribution, enabling accurate detection of near-field objects that would otherwise be obscured by receiver saturation.
3Productivity
If optical signals are transmitted for near-field detection, then the ability to detect close objects is improved, but internal reflections generate dazzle signals that saturate the receiver
Solution Approach 1:
The system converts the harmful dazzle signals into a useful measurement by using the second photodetector to specifically detect them. Instead of treating dazzle signals as mere noise to be eliminated, the invention measures them separately and uses this information to subtract the dazzle component from the total signal, thereby converting a harmful effect into a beneficial correction mechanism that enables accurate near-field detection.
Solution Approach 2:
The second photodetector serves as an intermediary that measures the dazzle signal generated by internal reflections. This intermediate measurement allows the system to calculate and subtract the dazzle contribution from the first photodetector's output, effectively eliminating the harmful effect while maintaining high productivity in near-field object detection.
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 approach enables the detection of objects as close as 10 cm with 1.4% reflectivity, compared to previous systems that could only detect objects at 60 cm, significantly enhancing near-field detection capabilities.
Implementation Method 1
a first photodetector (e.g., a photodiode) configured to receive a first return signal and a second return signal and generate a first electrical current in response to the first return signal and the second return signal
Implementation Method 2
a second photodetector (e.g., a photodiode) configured to receive the first return signal but not the second return signal and generate a second electrical current in response to the first return signal
Data Source
AI summary
An apparatus for cancellation of scattered light in lidar sensors is provided. In some embodiments, the apparatus includes a lidar device with a transmitter configured to transmit optical signals and a receiver configured to receive return signals based on the optical signals. The receiver includes a first photodetector configured to receive a first return signal and a second return signal, and generate a first electrical current in response to the first return signal and the second return signal. The receiver further includes a second photodetector configured to receive the first return signal but not the second return signal, and generate a second electrical current in response to the first return signal. The receiver also includes an amplifier configured to receive a third electrical current equal to a difference between the first electrical current and the second electrical current.