Polarization-Modulated Time-of-Flight Ranging for Precise Distance Sensing
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Solution Overview
Problem
Current vehicle perception systems, such as lidar, face limitations in high precision distance measurements due to the need for direct time measurements of light beam return signals, which can be inaccurate and limited by the speed of light.
Innovation Solution
A distance measuring system that uses a transmitter to send a time varying polarized light beam and a receiver to capture the reflected beam, calculating the time difference by comparing polarization states, allowing for indirect measurement of the time of flight and subsequent distance calculation without requiring direct time measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct time measurement of light beam return signals is used, then distance measurement can be performed, but measurement precision is limited by the speed of light and direct timing accuracy
Solution Approach 1:
The patent introduces polarization state as an intermediary parameter to measure time of flight. Instead of directly measuring time, the system modulates the polarization state of the transmitted light beam and measures the polarization state of the reflected beam. The change in polarization state serves as a mediator that encodes the time of flight information, allowing indirect measurement with higher precision than direct timing methods.
Solution Approach 2:
The patent changes the measurement parameter from direct time measurement to polarization state measurement. By modulating the polarization state of the transmitted beam and detecting the corresponding polarization state in the reflected beam, the system transforms the time measurement problem into a polarization state comparison problem, which can be measured with higher precision using polarization detectors.
2Measurement precision
If polarization modulation is used for indirect time measurement, then measurement precision is improved, but device complexity increases due to additional polarization modulators and detectors
Solution Approach 1:
The patent makes the light beam serve multiple functions: it simultaneously carries both intensity information and polarization state information. The same transmitted light beam is used for both ranging and target identification, and the same received beam provides both distance and material composition information. This multi-functionality reduces the need for separate measurement systems.
Solution Approach 2:
The target object itself serves as part of the measurement system by reflecting the polarized light beam. The target's material properties naturally affect the polarization state of the reflected beam, providing automatic target identification information without requiring additional sensors or active components at the target location.
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 method enables more accurate and precise distance measurements by correlating the polarization phase shift with the illumination state, improving range determination and target feature identification, while allowing continuous transmission and reception of light beams, enhancing navigation and object classification capabilities.
Implementation Method 1
a polarization modulator for modifying the polarization state of the linearly polarized light to a time varying polarization state
Implementation Method 2
a receiver configured to capture, at a plurality of subpixel regions of the receiver, a reflected time varying polarized light beam that has been reflected off of the target, wherein the receiver is further configured to generate a plurality of polarization signals for each subpixel region that are indicative of the polarization state
Implementation Method 3
The distance measuring system includes a controller configured to calculate a time difference between the transmitted time varying polarized light beam and the captured reflected light beam by comparing the polarization state of the captured reflected light beam with a polarization state of the transmitted time varying polarized light beam
Implementation Method 4
The controller is further configured to determine a distance between the target and the receiver by multiplying the calculated time difference with one half of the speed of light
Data Source
AI summary
A method for measuring a distance to a target based upon time modulated polarization state illumination is provided. The method includes: transmitting a time varying polarized light beam toward the target; capturing, at a plurality of subpixel regions of a receiver, a reflected time varying polarized light beam that has been reflected off of the target; generating a plurality of polarization signals for each subpixel region that are indicative of the polarization state of the captured reflected light beam in the subpixel region; calculating a time difference between the transmitted time varying polarized light beam and the captured reflected light beam by comparing the polarization state of the captured reflected light beam with a polarization state of the transmitted time varying polarized light beam; and calculating the distance by multiplying the calculated time difference with the speed of light.