Bistatic Lidar Beam Alignment and Focus Adjustment
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Solution Overview
Problem
Bistatic laser radar systems require frequent recalibration of beam focus and squint adjustments when changing the system range, reducing flexibility and user-friendliness, especially due to limitations in spatial resolution and sensitivity caused by diffraction and spurious reflections in monostatic systems.
Innovation Solution
A bistatic laser radar device with a transmit channel and a receive channel, where the focus of both beams is adjusted on a common axis within the operable range, allowing for simultaneous focus and squint adjustments using linear translation stages, ensuring optimal beam intersection without the need for separate calibration steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If monostatic lidar systems use common transmit/receive optics to achieve spatial resolution, then spatial resolution is improved, but diffraction restricts operation to short ranges and internal parasitic reflections significantly degrade system performance
Solution Approach 1:
The system divides the optical path into separate transmit and receive channels with distinct optics. The transmit optics include a transmit lens and the receive optics include a receive lens, eliminating the common optics that cause parasitic reflections. This segmentation allows each channel to be optimized independently for its specific function.
Solution Approach 2:
The patent extracts and removes the problematic common transmit/receive optics from the system. By taking out the shared optical path, the invention eliminates the source of internal parasitic reflections while preserving the ability to achieve spatial resolution through separate focused beams.
2Object-affected harmful factors
If bistatic lidar systems use separate transmit and receive optics to reduce spurious reflections, then noise from spurious reflections is reduced, but the transmit and receive beams must be separately focused and adjusted in angle requiring frequent recalibration when range is altered
Solution Approach 1:
The patent combines the focus adjustment and squint adjustment functions into a single integrated mechanism. By coupling the lateral position of the receive lens with the focus adjustment, the system achieves both beam intersection and proper focusing simultaneously, eliminating the need for separate calibration steps when range changes.
Solution Approach 2:
The receive lens assembly serves multiple functions simultaneously: it focuses the receive beam, provides squint adjustment for beam angle, and maintains proper alignment with the transmit beam. This multi-functionality in a single component eliminates the need for separate adjustment mechanisms and recalibration procedures.
3Measurement precision
If bistatic lidar systems focus transmit and receive beams to intersect at a specific point to define a probe volume, then the probe volume is accurately defined, but the non-parallel beams reduce the strength of the returned signal for distributed targets
Solution Approach 1:
The system applies different optical characteristics to different parts of the optical path. The transmit optics are optimized for creating a focused beam, while the receive optics are optimized for collecting scattered light. The receive lens has specific optical properties that enhance its ability to collect weak returned signals while maintaining the focused beam geometry.
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 enhances the flexibility and user-friendliness of bistatic lidar systems by maintaining optimal performance across the operational range without the need for frequent recalibration, reducing noise from spurious reflections, and improving sensitivity by ensuring precise beam intersection.
Implementation Method 1
a transmit channel for forming a focused transmit beam
Implementation Method 2
detect the returned signal
Implementation Method 3
a receive channel for forming a focused receive beam
Implementation Method 4
the use of coherent laser radar (CLR) permits the measurement of any Doppler shift in the frequency of the returned signal thereby enabling information on the relative speed of the target to be measured
Implementation Method 5
Measurement of the Doppler frequency shift to a high accuracy is typically achieved in CLR devices by beating (heterodyning) the return signal with a stable local-oscillator beam
Data Source
AI summary
A bistatic laser radar (lidar) device is described that comprises a transmit channel (60) for forming a focused transmit beam, and a receive channel (62) for forming a focused receive beam. The device is arranged such that the focus of the transmit beam and the focus of the receive beam fall on a common axis when focused to a distance within the operable distance range of the device. The device may be used for vibrometry, wind speed measurements and the like. Implementation of such a device using optical fiber based components is described.