Lidar Sensor Window Reflection Control With Timed Detector Modes
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Solution Overview
Problem
Lidar sensors are hindered by partial reflections on protective windows due to deposits or surface defects, leading to saturation and overlap of object echoes, particularly in close range, compromising detection reliability.
Innovation Solution
A lidar sensor with adjustable light sensitivity modes and a protective window integrated into the housing, utilizing a time interval and bias voltage adjustments to distinguish between partial reflections and object echoes, enhancing detection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective window is used to protect the lidar sensor from environmental influences, then the sensor is protected from moisture, dirt, and damage, but partial reflections occur on the protective window surface that cause saturation in the photodetector and overlap with object echoes
Solution Approach 1:
The patent applies preliminary action by adjusting the bias voltage of the photodetector before the expected arrival time of the laser pulse echo. The system anticipates the reflection interference and proactively modifies the detector's sensitivity state to prevent saturation, rather than reacting after saturation occurs. This is achieved by calculating a time interval based on the speed of light and the distance to the protective window, then adjusting the bias voltage in advance.
Solution Approach 2:
The patent changes the electrical parameter (bias voltage) of the photodetector dynamically based on the expected timing of reflected signals. By modifying the bias voltage parameter before and after the expected echo arrival time, the system controls the detector's gain and sensitivity to distinguish between weak true echoes and strong window reflections, preventing saturation while maintaining detection capability.
2Measurement precision
If the bias voltage of the photodetector is increased to improve detection sensitivity, then object echoes can be detected more accurately, but partial reflections from the protective window cause saturation in the photodetector
Solution Approach 1:
The system performs preliminary action by pre-adjusting the bias voltage before the expected arrival of the laser echo. By calculating the time interval based on light speed and window distance, the system knows when the reflection interference will occur and proactively sets the bias voltage to an optimal level that prevents saturation while maintaining sensitivity for true object echoes.
Solution Approach 2:
The patent implements dynamics by making the bias voltage adjustable and time-dependent rather than fixed. The system dynamically changes the bias voltage parameter based on the operational state and expected signal timing, allowing optimal detection sensitivity while avoiding saturation from protective window reflections. This dynamic adjustment enables the detector to adapt its characteristics in real-time.
3Measurement precision
If echo separation algorithms are used to distinguish between partial reflections and object echoes, then detection accuracy can be maintained, but the complexity of the evaluation unit increases
Solution Approach 1:
Instead of using complex software algorithms to separate echoes, the patent changes the fundamental parameter of the photodetector's bias voltage. This physical parameter adjustment creates distinct signal characteristics that simplify the evaluation process. By controlling the detector's electrical state based on timing information, the system achieves echo separation with minimal computational complexity, relying on physical principles rather than complex signal processing.
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 reduces interference from partial reflections, enabling reliable object detection even in close proximity, improving the accuracy and reliability of lidar sensors.
Implementation Method 1
deposits on the protective glass and/or surface defects of the protective glass (e.g., scratches) can lead to unwanted partial reflections of the laser light within the lidar sensor
Implementation Method 2
the receiving unit is configured to receive through the protective window, by means of a detector (specifically a photodetector), portions of the emitted laser pulse reflected in the environment, and to generate a signal (in particular an electrical signal) corresponding to the reflected portions of the laser pulse
Implementation Method 3
the transmitting unit has, for example, one or more laser diodes
Implementation Method 4
the lidar sensor is configured to ascertain distances to objects in the environment of the lidar sensor on the basis of a measurement of times of flight of an emitted laser light
Data Source
AI summary
A lidar sensor. The lidar sensor includes a transmitting unit, a receiving unit, a protective window, a housing, and an evaluation unit. The transmitting unit generates a laser pulse which is emitted into an environment, the receiving unit receives through the protective window portions of the emitted laser pulse reflected in the environment, and generates a signal corresponding to the reflected portions of the laser pulse. The evaluation unit puts the receiving unit into a first receiving mode before receiving partial reflections of a particular laser pulse, which are caused within the lidar sensor by the protective window, puts the receiving unit into a second receiving mode at a predefined time interval from the emission of the laser pulse, receives the generated signal, and distinguishes first signal components generated by partial reflections on the protective window from second signal components generated by reflections on objects in the environment.