Automotive Lidar Beam Steering via Liquid Crystal Polarization Control

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Solution Overview

Problem

Lidar systems in vehicles face resolution issues, assembly challenges, and temperature dependence due to the use of mechanical devices like spinning disks or MEMS for beam orientation, which are undesirable.

Innovation Solution

A method using a first quarter wave plate to generate a circularly polarized scanning beam, a liquid crystal half-wave plate to select the rotation direction of the polarization vector, and a liquid crystal polarized grating to deflect the beam by a selected angle, with a Faraday rotator and synchronized deflection stages in both transmitting and receiving channels to achieve precise beam orientation and direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If mechanical devices like spinning disks or MEMS are used for beam orientation, then beam direction control is achieved, but resolution issues and temperature dependence occur

Engineering Contradiction:

Improvebeam orientation precisionVSAvoidtemperature stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent replaces mechanical beam orientation devices (spinning disks, MEMS) with an optical system using wave plates and polarized gratings. The beam direction is controlled by electrically adjusting the polarization state of light through voltage-controlled wave plates, eliminating mechanical moving parts that cause temperature dependence and resolution issues.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system changes the polarization parameters of the light beam using voltage-controlled wave plates. By adjusting the voltage applied to the wave plates, the polarization state (linear, circular, elliptical) and orientation angle are dynamically changed, which in turn controls the beam deflection angle through the polarized diffraction grating, achieving precise beam orientation without mechanical movement.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If mechanical devices like spinning disks or MEMS are used for beam orientation, then beam direction control is achieved, but assembly issues occur

Engineering Contradiction:

Improvebeam orientation precisionVSAvoidassembly complexity

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If liquid crystal components are used for polarization control, then beam orientation precision is improved, but device complexity increases

Engineering Contradiction:

Improvebeam orientation precisionVSAvoidoptical component complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The wave plates serve multiple functions: they control the polarization state (linear, circular, elliptical), adjust the polarization orientation angle, and thereby control the beam deflection angle. This multi-functionality reduces the need for separate mechanical adjustment mechanisms, offsetting the added optical component complexity with functional integration.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution provides a stable and precise beam orientation mechanism that avoids the limitations of mechanical devices, enhancing the resolution and reliability of Lidar systems while reducing temperature dependence and assembly complexities.

Implementation Method 1

generating, at a first quarter wave plate of the Lidar system, a circularly polarized scanning beam of light

Methodology Applied

Scientific EffectWave plate phase retardation: Birefringence

Implementation Method 2

a liquid crystal half-wave plate that selects the rotation direction for the polarization vector and a liquid crystal polarized grating that deflects the scanning beam based on the selected rotation direction

Methodology Applied

Scientific EffectLiquid crystal optical rotation: Liquid Crystals

Implementation Method 3

a liquid crystal polarized grating that deflects the scanning beam by a selected angle from the longitudinal path based on the selected rotation direction of the polarization vector

Methodology Applied

Scientific EffectPolarized diffraction: Diffraction Grating

Implementation Method 4

A Faraday rotator of the Lidar system is used to impart a polarization direction to the reflected beam at a polarized beam splitter that is perpendicular to a polarization direction of the scanning beam at the polarized beam splitter

Methodology Applied

Scientific EffectFaraday rotation: Faraday Effect

Data Source

PatentUS11698445B2Automotive Lidar with multi-spectral depth imaging and discrete scanning mechanism

Publication Date: 2023.07.11 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A vehicle, Lidar system for the vehicle and method of scanning an object with the Lidar system. The Lidar system includes a first quarter wave plate, a first deflection stage and a detector. The first quarter wave plate produces a circularly polarized scanning beam of light. The first deflection stage selects a rotation direction for a polarization vector of the scanning beam and deflects the scanning beam by a selected angle based on the selected rotation direction of the polarization vector. The detector receives a reflected beam that is a reflection of the scanning beam from the object.