Optical Radar Polarizing Filter for SN Ratio
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Solution Overview
Problem
Conventional optical radar apparatuses face challenges in achieving high signal-to-noise (SN) ratio due to intense background light, particularly from sunlight, which interferes with distance measurement accuracy, especially when the object's surface is inclined and the light path follows specular reflection, leading to weakened signal intensity and loss of outline information.
Innovation Solution
The optical radar apparatus employs a light source emitting pulse light, a scanning device that scans in one direction, and a polarizing filter system that polarizes the light vertically to the scanning direction, allowing only vertically polarized light to be transmitted to the sensor, while a sub sensor handles light polarized parallel to the scanning direction, effectively reducing background noise and enhancing SN ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a polarizer is installed to reduce background light interference, then the SN ratio is improved, but the signal intensity is reduced by half due to loss of polarized state
Solution Approach 1:
The light receiving system is divided into two separate channels: a first light receiving unit with a first polarizer oriented in a first direction, and a second light receiving unit with a second polarizer oriented in a second direction perpendicular to the first direction. This segmentation allows each channel to capture different polarization components of the reflected light, thereby recovering the total signal intensity while still filtering background light through polarization selection.
2Adaptability or versatility
If the optical radar apparatus operates under intense sunlight, then it can function in automotive applications, but background light causes serious interference when specular reflection occurs
Solution Approach 1:
The invention changes the polarization parameter of the light detection system by using two light receiving units with polarizers oriented in perpendicular directions. This parameter change allows the system to distinguish between polarized reflected light (signal) and unpolarized or differently polarized background light (noise), enabling operation under intense sunlight conditions.
3Measurement precision
If only a specific polarized state is detected to reduce background light, then the SN ratio is improved, but the signal intensity is reduced by half
Solution Approach 1:
The light receiving system is divided into two separate channels: a first light receiving unit with a first polarizer oriented in a first direction, and a second light receiving unit with a second polarizer oriented in a second direction perpendicular to the first direction. This segmentation allows each channel to capture different polarization components of the reflected light, thereby recovering the total signal intensity while still filtering background light through polarization selection.
Solution Approach 2:
The invention merges the output signals from two light receiving units that detect different polarization components. By combining these signals, the system recovers the total signal intensity that would otherwise be lost when using a single polarizer, while maintaining the background light rejection capability.
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 configuration significantly improves the SN ratio by reducing strong background light interference, allowing for accurate distance measurement and shape recognition even under intense sunlight conditions, while maintaining efficient light transmission without losing polarized state.
Implementation Method 1
a polarizing filter system that polarizes the light vertically to the scanning direction, allowing only vertically polarized light to be transmitted to the sensor
Implementation Method 2
a method of radiating laser light and measuring a flight time (Time-of-flight) until the laser light is reflected by the object and returns therefrom
Data Source
AI summary
An SN ratio of light to be received is improved. A polarizing filter (150) that is arranged in a light path extending from an object (11) to a light receiving unit (154) of a ToF sensor (153) and allows transmission of light polarized in a direction vertical to a direction of scanning is provided.