Polarization Separation in LIDAR Imaging to Reduce Walk-Off Signal Loss
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Solution Overview
Problem
FMCW based LIDAR systems experience signal loss due to the 'walk-off' effect, where incoming laser beams are directed away from the input facet of the photonic integrated circuit (PIC) as the scanner mirror rotates, limiting scan speeds, range of operation, and signal-to-noise ratio.
Innovation Solution
Implementing a LIDAR system with a single output waveguide and multiple input waveguides spaced apart based on FOV, fast-axis speed, slow-axis speed, and other parameters to capture returning photons from different orientations, minimizing signal loss and enabling high-speed scanning without degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single input facet is used for receiving reflected laser beams, then the device complexity is reduced, but signal loss increases due to walk-off effect at high scan speeds
Solution Approach 1:
The single input facet is divided into multiple input facets arranged in a specific pattern. Each input facet captures photons returning at different angles and time intervals, ensuring complete signal capture across the entire field of view even at high scan speeds. This segmentation resolves the walk-off effect by distributing the photon collection across multiple spatial positions.
2Loss of energy
If multiple input facets are used to capture returning photons at different angles, then signal loss is reduced, but device complexity increases
Solution Approach 1:
Multiple input facets are designed to serve multiple functions simultaneously: they capture photons from different angles, handle different time intervals of returning signals, and maintain polarization information. The waveguide structure is configured to receive photons from various orientations and route them to appropriate detection paths, making the system universally capable of handling high-speed scanning without signal loss.
3Productivity
If the scanner operates at high speed, then productivity is improved, but signal loss increases due to walk-off effect
Solution Approach 1:
The multiple input facets are pre-configured in specific spatial arrangements before operation begins. This preliminary arrangement ensures that as the scanner operates at high speed, photons returning at different angles and time intervals are already positioned to be captured by the appropriate input facets, eliminating the need for real-time adjustment and preventing signal loss during high-speed scanning.
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 system effectively extends the range of operation and maintains high scan resolution by maximizing photon capture, allowing for simultaneous detection of objects at short and medium ranges without increasing costs.
Implementation Method 1
FMCW systems may can include a polarization separator element that can split an incoming or return signal into two polarization components, namely a transverse electric (TE) component and a transverse magnetic (TM) component
Implementation Method 2
The plurality of input waveguides may be configured to couple reflected imaging signals into the imaging device
Implementation Method 3
FMCW based LIDARs have emerged as a leading imaging technology that is immune to ambient light interference and provides several data metrics for each imaging pixel
Data Source
AI summary
Systems and methods described herein are directed to polarization separation of incoming light signals associated with an imaging system, such as a Light Detection and Ranging (LIDAR) system. Example embodiments describe a system configured to direct incoming light signals to a polarization separator and capture the two polarization states of the incoming light signals. The system may process the two polarization states of the incoming light signals separately to extract information associated with reflecting objects within the field-of-view of the imaging system. The polarization separator may be a birefringent crystal positioned adjacent to an edge of a photonic integrated circuit (PIC) that is used for processing outgoing and incoming light signals associated with the imaging system. The PIC may include at least one on-chip polarization rotator for converting a light signal of one polarization state to a light signal of another polarization state.