Coherent Ladar Receiver for Simultaneous Range and Velocity
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Solution Overview
Problem
Current ladar systems face limitations in size, power consumption, and cost due to the need for separate, bulky laser range finders to estimate target range and velocity, which also require multiple pulses and are less sensitive than coherent detection receivers.
Innovation Solution
A compact, low-cost solution using a single-pixel, wide-bandwidth coherent ladar receiver with digital holography transceiver hardware, featuring a small receiver aperture and a single-element wideband detector to simultaneously measure target range and Doppler velocity, eliminating the need for a second laser source and minimizing sensor optics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate laser range finders are used to estimate target range and velocity, then measurement capability is improved, but device complexity and size increase
Solution Approach 1:
The patent combines separate laser range finder and velocity measurement functions into a single integrated coherent detection receiver. The receiver uses a local oscillator beam mixed with the returned signal to simultaneously obtain both range and velocity information through coherent detection, eliminating the need for separate measurement systems.
Solution Approach 2:
The coherent detection receiver is designed to perform multiple functions: it detects target range, velocity, and provides imaging capability through digital holography. This multi-functional receiver replaces what would traditionally require separate specialized systems for each measurement type.
2Measurement precision
If multiple laser sources are used for range and velocity measurement, then measurement accuracy is improved, but power consumption and cost increase
Solution Approach 1:
The patent uses a single laser source that provides both the illumination beam and the local oscillator beam for coherent detection. This eliminates the need for multiple separate laser sources, reducing power consumption while maintaining the capability to measure both range and velocity with high precision.
3Reliability
If large receiver apertures are used, then sensitivity is improved, but size and weight increase
Solution Approach 1:
The patent changes the detection parameter from direct detection to coherent detection, which provides enhanced sensitivity through the mixing of the returned signal with a local oscillator beam. This allows for smaller receiver apertures and reduced weight while maintaining or improving detection sensitivity compared to direct detection systems.
4Device complexity
If direct detection is used, then system simplicity is improved, but measurement capability is worsened
Solution Approach 1:
The patent replaces direct detection with coherent detection, substituting a more complex detection mechanism that provides access to field phase information. This enables Doppler velocity measurement, vibrometry, and wavefront sensing capabilities that are not available with simpler direct detection systems.
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 enables efficient, sensitive, and cost-effective simultaneous range and velocity measurement, reducing power consumption and size while maintaining high sensitivity to high-energy-laser backscatter and background light, with potential for longer-range monitoring.
Implementation Method 1
coherent detection systems include a receiver that incorporates a local oscillator (LO) beam of light that is mixed with the received light to produce a signal proportional to the coherent addition of the LO electric field and the signal field
Implementation Method 2
The reflected light is interfered with one or more off-axis reference beams (e.g., local oscillators) to form holograms on the focal plane array
Implementation Method 3
Access to field phase enables many measurements and ladar architectures not available to direct detection lidar including Doppler-velocity
Data Source
AI summary
Systems and methods are provided for a digital holography range Doppler receiver. The subject system transmits outgoing electromagnetic radiation to a target, and provides a first reference local oscillator (LO) beam to a first detector and a second reference LO beam to a second detector, based on the outgoing electromagnetic radiation. The system receives reflected electromagnetic radiation from the target through a first optical receiver and a second optical receiver having a smaller diameter, and determines range and velocity of the target simultaneously using an interference with the second reference LO beam. The system applies time and frequency offsets to the first reference LO beam based on the measured range and velocity to align the first reference LO beam with the reflected electromagnetic radiation, and produces an image of the target using the first reference LO beam having the applied time and frequency offsets.