FMCW Lidar Reflector for Secondary Beat Frequency Resolution
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Solution Overview
Problem
Existing FMCW heterodyne detection LIDAR imaging systems face challenges in achieving improved range resolution without degrading system performance or complicating processing electronics, as increasing the chirp value can distort beat frequency measurements and optical power modulation introduces non-linearity.
Innovation Solution
Incorporating a reflector in the LIDAR system to reflect a portion of the backscattered object signal not collected by the optical collection element, allowing for the processing unit to determine distance from a secondary beat frequency of the heterodyne signal, thereby improving distance resolution without altering the chirp or increasing processing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the chirp value is increased to improve distance resolution, then distance resolution is improved, but beat frequency measurement becomes distorted and system performance degrades
Solution Approach 1:
The patent introduces a reflector as an intermediary element that reflects the optical signal back to the scene. This creates a secondary beat frequency component that can be used for distance measurement without requiring high chirp values. The reflector acts as a mediator that enables improved distance resolution through alternative measurement pathways while maintaining measurement accuracy.
Solution Approach 2:
The patent changes the measurement parameter from relying solely on the primary beat frequency (which requires high chirp for resolution) to utilizing the secondary beat frequency generated by the reflected signal. This parameter change allows distance resolution improvement without the harmful side effects of increasing the chirp value, as the secondary frequency component provides the necessary resolution through different physical mechanisms.
2Measurement precision
If the chirp value is increased to improve distance resolution, then distance resolution is improved, but optical power modulation introduces non-linearity
Solution Approach 1:
The reflector serves as an intermediary that creates an additional signal path. The secondary beat frequency generated through this reflected path provides distance measurement capability without requiring high optical power modulation. This intermediary mechanism bypasses the non-linearity issue caused by high chirp-induced power modulation while maintaining measurement precision.
Solution Approach 2:
The reflector creates a copied version of the optical signal that travels a different path (reflection path) before reaching the detector. This copied signal generates a secondary beat frequency that can be used for distance measurement without requiring the primary signal to undergo high power modulation, thus avoiding non-linearity while achieving the same measurement objective.
3Power
If the optical collection element collects all backscattered signal, then signal strength is maximized, but distance resolution cannot be improved beyond the fundamental limit
Solution Approach 1:
The patent segments the backscattered signal into two components: one that is collected by the optical collection element (maintaining signal strength) and another that is reflected by the reflector (enabling resolution improvement). This segmentation allows the system to simultaneously maintain strong signal detection through the collection element while utilizing the reflected portion for enhanced distance resolution through the secondary beat frequency.
Solution Approach 2:
The patent adds another dimension to the signal processing by introducing a reflected signal path in addition to the directly collected signal. This dimensional addition creates a secondary measurement channel that provides improved distance resolution without compromising the primary signal strength, effectively adding a new degree of freedom to the measurement system.
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 achieves a doubled distance resolution by utilizing the secondary beat frequency, maintaining system performance and simplicity, enabling precise discrimination between objects with small distance differences.
Implementation Method 1
an optical source (10), adapted to emit a primary signal (Sp) continuous and frequency modulated
Implementation Method 2
the photodetector (50), adapted to receive a part (Sor,c) of the backscattered object signal (Sor) and the reference signal (Sr), which interfere to form a heterodyne signal (Sh) having a beat frequency (fb)
Implementation Method 3
which interfere to form a heterodyne signal
Implementation Method 4
a reflector (42) adapted to reflect a part (Sor,nc) of the backscattered object signal (Sor) not collected by the optical collection element (41) towards the scene (2)
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
The invention relates to an FMCW-type Lidar imaging system with improved range resolution. The imaging system 1 comprises a reflector 42 adapted to reflect back towards the scene 2 a portion Sor,nc of the backscattered object signal Sor that has not been collected by the collector 41. Thus, the collected portion Sor,c of the backscattered object signal Sor consists of light beams Sor,c(1) not reflected by the reflector 42 and light beams Sor,c(2) reflected by the reflector 42. The heterodyne signal Sh therefore has a primary component Sh(1) associated with the light beams Sor,c(1), and a secondary component Sh(2) associated with the light beams Sor,c(2). The processing unit 60 is adapted to determine the distance zsc to the scene 2 from a beat frequency fb(2) of the secondary component Sh(2) of the heterodyne signal Sh.