Fiber Laser LIDAR Pulse Shape and Eye-Safety
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Solution Overview
Problem
Existing LIDAR apparatuses used on aerial platforms face limitations in performance and safety, particularly in high-speed data acquisition and vertical discrimination, with conventional lasers producing poorly shaped pulses and lower optical power, which affects accuracy and eye-safety.
Innovation Solution
The use of fiber lasers with rare-earth doped elements for high-speed pulse generation, capable of transmitting at least 20,000 pulses per second with pulse widths of five nanoseconds or less, along with advanced circuitry for precise time measurement and position tracking, enhances vertical discrimination and eye-safety by maintaining consistent pulse shape and increasing optical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional lasers are used for LIDAR measurements, then the system can operate at lower pulse rates, but the pulse shape becomes distorted and optical power decreases, reducing measurement accuracy and vertical discrimination
Solution Approach 1:
The patent changes the fundamental parameters of the laser system by using fiber lasers with rare-earth doping and specific cavity designs that enable high pulse rates (≥20,000 pulses per second) while maintaining consistent pulse shape and high optical power. This parameter change resolves the contradiction by allowing the system to operate at high speeds without sacrificing measurement precision.
Solution Approach 2:
The patent employs composite material structures in the laser medium, specifically using rare-earth-doped fiber materials that combine the advantages of optical fiber confinement with the gain properties of rare-earth ions. This composite approach enables the laser to maintain stable pulse characteristics at high transmission rates, thereby improving both speed and measurement precision simultaneously.
2Productivity
If conventional lasers transmit light pulses at high rates, then productivity increases, but pulse shape distortion and reduced optical power occur, harming measurement precision
Solution Approach 1:
The patent modifies the laser operating parameters by using fiber laser technology with rare-earth doping, which enables transmission rates of at least 20,000 pulses per second while maintaining consistent pulse shape and high optical power. This parameter change allows the system to achieve high productivity without compromising vertical discrimination capability.
Solution Approach 2:
The patent replaces conventional laser mechanisms with fiber laser technology, substituting the traditional laser cavity and gain medium with an optical fiber-based system. This substitution enables stable high-rate pulse transmission with consistent pulse shapes, thereby improving both data acquisition rate and vertical discrimination simultaneously.
3Measurement precision
If laser pulse width is reduced to improve vertical discrimination, then measurement accuracy improves, but eye-safety concerns increase due to higher peak power density
Solution Approach 1:
The patent changes the laser wavelength parameter to 1.5 micrometers, which falls in an eye-safe atmospheric transmission window. This parameter change allows the system to use narrow pulse widths (≤5 nanoseconds) for improved vertical discrimination while maintaining eye-safety, as the 1.5 micrometer wavelength is less damaging to the retina compared to visible wavelengths.
Solution Approach 2:
The patent converts the potential harm of high peak power density into a benefit by selecting a wavelength (1.5 micrometers) that is inherently safer for eye exposure. The narrow pulse width that would normally increase eye-safety risk actually improves vertical discrimination capability, while the wavelength selection mitigates the harm, turning a potential disadvantage into an advantage.
4Measurement precision
If fiber lasers with rare-earth doping are used to maintain consistent pulse shape at high rates, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent replaces complex conventional laser cavity designs with a fiber laser system, where the optical fiber itself serves as the laser medium and waveguide. This substitution simplifies the overall device structure while enabling consistent pulse shape at high transmission rates, thereby improving measurement precision without proportionally increasing device complexity.
Solution Approach 2:
The patent employs fiber lasers that can operate across multiple wavelengths and configurations, providing universal functionality for various LIDAR applications. The rare-earth-doped fiber medium can be tuned to different wavelengths (including the eye-safe 1.5 micrometer band), allowing a single device design to serve multiple purposes, thereby reducing overall system complexity while maintaining pulse shape consistency.
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 approach improves the accuracy of distance measurement to within ten centimeters or less, increases vertical discrimination to 3.5 meters or less, and enhances eye-safety by reducing pulse width and energy, allowing for higher altitudes and more efficient data acquisition.
Implementation Method 1
at least one fiber laser configured to transmit pulses of light to a surface
Implementation Method 2
Each fiber laser includes an optical fiber as an active gain region, wherein the active gain region includes a rare-earth doped element
Implementation Method 3
an optical receiver configured to receive return signals representing portions of the transmitted pulses of light reflected from the surface
Implementation Method 4
elapsed time circuitry configured to measure an elapsed time between transmission of the pulses of light by the fiber laser and reception of the return signals
Data Source
AI summary
Apparatuses and methods for gathering data describing a surface are disclosed. The apparatuses transmit pulses of light at a high rate using one or more fiber lasers. Examples of such apparatuses include laser ranging systems, such as light detection and ranging (LIDAR) systems, and laser scanners. Data received from the apparatus by a data processing unit can be used to create a data model, such as a point cloud, digital surface model or digital terrain model describing the surface. The surface can be the surface of terrain and/or objects, for example. Use of the fiber laser results in many advantages, such as improved vertical surface discrimination, increased pulse rate, safety benefits, as well as other advantages.