Polarising Beam Splitter Window for Lidar Backscatter Reduction
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Solution Overview
Problem
Current laser projection and return systems in gas detection face challenges in minimizing backscatter and crosstalk, which affects the sensitivity and accuracy of gas detection, particularly in high-sensitivity, low-power remote gas detection systems.
Innovation Solution
The optical assembly incorporates a polarising beam splitter/combiner that serves as a window, reducing the number of optical surfaces in the common exit/return path, and employs super-polished surfaces and additional polarisers to minimize backscatter, along with a mechanical design that limits the optical path to the detector to reduce stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a polarising beam splitter/combiner is used to separate laser light from scattered light, then measurement precision is improved, but device complexity increases due to additional optical components
Solution Approach 1:
The patent combines the window function and beam splitter function into a single polarising beam splitter/combiner component. This merging eliminates the need for separate windows and reduces the number of optical surfaces, thereby maintaining measurement precision while reducing device complexity.
Solution Approach 2:
The polarising beam splitter/combiner serves multiple functions simultaneously: it acts as a window to the housing, separates laser light from scattered light based on polarization, and minimizes backscatter. This multi-functionality reduces the overall number of components needed in the optical assembly.
2Reliability
If multiple optical surfaces are present in the exit/return path, then optical component functionality is maintained, but backscatter and crosstalk increase reducing measurement precision
Solution Approach 1:
The patent extracts or removes unnecessary optical surfaces from the optical path by using the beam splitter/combiner as the window. This reduction in optical surfaces directly decreases backscatter and crosstalk, improving measurement precision while maintaining essential optical functionality.
Solution Approach 2:
The patent applies super-polished surfaces specifically at critical optical interfaces where backscatter occurs. This localized quality enhancement minimizes backscatter at key points without requiring all optical surfaces to be super-polished, balancing reliability and precision.
3Measurement precision
If additional optical components are added to minimize backscatter, then measurement precision is improved, but loss of energy increases due to more interfaces
Solution Approach 1:
By merging the window and beam splitter functions into one component, the patent reduces the number of optical interfaces. This reduction minimizes energy loss at interfaces while still achieving backscatter separation, thus improving signal-to-noise ratio without excessive energy loss.
Solution Approach 2:
The patent changes the polarization parameter of light to separate the laser beam from the scattered return. This parameter-based separation method is more efficient than using additional physical components, reducing energy loss while maintaining precision.
4Ease of manufacture
If the optical assembly uses a conventional window and beam splitter configuration, then ease of manufacture is improved, but backscatter into the detector increases reducing reliability
Solution Approach 1:
The patent combines two separate components (window and beam splitter) into one integrated polarising beam splitter/combiner. This reduces the number of assembly steps and potential misalignments, maintaining ease of manufacture while significantly improving reliability by reducing backscatter paths.
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 configuration enhances the rejection of reflected laser light, increases the sensitivity of gas detection, and reduces operational costs by minimizing laser power feedback into the detector, thereby improving the accuracy and efficiency of gas detection systems.
Implementation Method 1
a polarising beam splitter/combiner common to the exit path and the return path arranged to polarise laser light exiting from the housing and to separate scattered laser light returned to the assembly, that is orthogonally polarised to the exiting laser radiation
Data Source
AI summary
An optical assembly for a laser projection and return laser light detection device comprises a housing; a first series of components arranged in the housing to define an exit path for laser radiation entering from a laser source and then exiting from the housing; a second series of components arranged in the housing to define a return path for scattered returns of the laser radiation entering the housing and passing to a detector; a polarising beam splitter/combiner common to the exit path and the return path arranged to polarise laser light exiting from the housing and to separate scattered laser light returned to the assembly, that is orthogonally polarised to the exiting laser radiation. The polarising beam splitter/combiner forms a window to the housing.