Optical Phased Array LIDAR for Vibration-Insensitive Terrain Mapping
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Solution Overview
Problem
Existing systems for providing navigational aids in low or no visibility situations, such as degraded visual cue environments, are limited by size, weight, power draw, and susceptibility to vibrations, and fail to deliver reliable real-time terrain mapping due to limitations in radar and millimeter wave systems.
Innovation Solution
An all-fiber optic laser-based scanning system using an optically phased array for real-time terrain mapping, which includes a modulator, beam splitter, phase modulator, transceiver, and electro-optical receiver to generate and phase-shift beams for accurate terrain profiling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radar or millimeter wave systems are used for terrain mapping, then real-time navigation capability is provided, but size, weight, and power consumption increase significantly
Solution Approach 1:
The patent replaces traditional mechanical radar systems with an optical LIDAR system using laser beams for terrain mapping. This substitution of the physical/mechanical radar approach with an optical system achieves the same navigation function while dramatically reducing size, weight, and power consumption, making it suitable for helicopter applications.
2Measurement precision
If millimeter wave radar with reduced wavelength is used, then cross range resolution is improved, but aperture size increases to 224 mm for 1° conical footprint
Solution Approach 1:
The patent changes the fundamental operating parameter from millimeter wave radar to optical LIDAR, operating at optical wavelengths (hundreds of nanometers) rather than millimeter waves (millimeters). This parameter change enables achieving the same or better angular resolution with a much smaller aperture, as optical wavelengths are thousands of times shorter than millimeter waves.
3Measurement precision
If traditional radar systems are used, then terrain mapping is provided, but specular reflections from natural materials reduce terrain resolution
Solution Approach 1:
The patent exploits the wavelength-dependent interaction of electromagnetic radiation with matter. By using optical wavelengths instead of radio wavelengths, the system interacts differently with natural materials - optical light is scattered by surface roughness at the micro-scale rather than producing specular reflections, thereby improving terrain resolution and eliminating the harmful reflection effect.
4Ease of operation
If plane-parallel plates are used for beam steering, then one-dimensional beam steering is achieved, but phase errors significantly reduce on-axis optical power and degrade resolution
Solution Approach 1:
The patent removes the plane-parallel plates from the optical system entirely, replacing the mechanical beam steering approach with direct electronic control of the laser source or use of other steering mechanisms that do not introduce phase errors. This extraction of the problematic component eliminates the phase error issue while maintaining beam steering capability through alternative means.
5Stability of the object's composition
If MEMS devices are used for beam steering, then scan angle and intrinsic stability are improved, but insertion loss and power handling capability require further improvement
Solution Approach 1:
The patent appears to use a more robust, perhaps less sophisticated beam steering approach that does not rely on fragile MEMS devices. By accepting slightly reduced stability in exchange for using simpler, more durable components with lower insertion loss and better power handling, the system achieves reliable operation in harsh helicopter environments.
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 provides agile, high-resolution, and vibration-insensitive real-time terrain mapping, suitable for helicopter applications, with reduced size, weight, and power consumption, enhancing situational awareness in degraded visual conditions.
Implementation Method 1
a modulator configured to modulate a beam
Implementation Method 2
a beam splitter configured to split the modulated beam into a plurality of beams
Implementation Method 3
a phase modulator configured to phase shift each of the plurality of beams
Implementation Method 4
an electro-optical receiver configured to convert the reflected beams into corresponding electrical signals
Data Source
AI summary
An all fiber optic laser based scanning system for real time terrain mapping under degraded visual conditions is disclosed. A laser output is modulated to achieve a desired pulse width and pulse repetition frequency (PRF) and the modulated signal is amplified. The amplified optical signals are split into N channels that correspond to N elements of an optically phased array that steers light by modulating the phase of light entering and exiting the optical system. By applying a linear phase shift across the beam's wave front, the light propagating along the system's optical axis is steered to an off-axis angle. A real time map of an underlying terrain is accomplished by sweeping the N channel array across the terrain while collecting range information from each scan grid.