Aligning Polarization Devices Using Spatially Variant Elements
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Solution Overview
Problem
The assembly of polarization-based optical devices, such as those used in head-mounted displays, is time-consuming and costly due to the need for precise rotation of polarization components, often determined by trial and error, which complicates the achievement of desired polarization states like circularly polarized light.
Innovation Solution
An alignment apparatus and system that utilize spatially variant polarization elements and photodetector arrays to detect optical power distributions, allowing for precise alignment of polarization devices by determining the rotation angle needed to match a predetermined optical power distribution, thereby streamlining the assembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If trial and error method is used to determine rotation angles of polarization components, then alignment precision can be achieved, but assembly time and manufacturing cost increase significantly
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the optimal rotation angles for polarization components in a lookup table before assembly. During manufacturing, the system simply queries this pre-computed table based on measured optical parameters, eliminating the need for time-consuming trial and error adjustments while maintaining high alignment precision
Solution Approach 2:
The patent implements feedback by using photodetectors to measure the actual optical power distribution of the light beam, comparing it with the target distribution, and using this feedback information to determine the precise rotation angles needed. This closed-loop feedback mechanism enables rapid convergence to the correct alignment without iterative trial and error
2Manufacturing precision
If trial and error method is used to determine rotation angles of polarization components, then alignment precision can be achieved, but manufacturing cost increases
Solution Approach 1:
The patent replaces the mechanical trial-and-error adjustment process with an automated optical measurement and computation system. Photodetectors measure optical power distribution, a processor calculates the required rotation angles using pre-stored lookup tables, and actuators automatically position the polarization components. This substitution of mechanical iteration with automated optical-electrical-mechanical integration reduces both time and cost while maintaining high precision
Solution Approach 2:
The patent reduces manufacturing cost by pre-computing and storing optimal rotation angle solutions in lookup tables during system setup. This preliminary action eliminates the need for expensive iterative adjustment procedures during each assembly operation, transforming a high-cost per-unit process into a low-cost automated query-and-execute operation
3Productivity
If spatially variant polarization element is used, then alignment speed and precision improve, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the analyzer into multiple spatially separated photodetector elements, each measuring optical power at different positions. This segmentation enables parallel measurement of the optical power distribution across the beam profile, dramatically increasing alignment speed while the complexity is managed through systematic data processing using pre-stored lookup tables that map measurements to rotation angles
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 method significantly reduces the time and cost associated with aligning polarization-based optical devices by enabling quick and precise determination of the necessary rotation angles, ensuring accurate polarization states without the need for iterative trial and error.
Implementation Method 1
At least one of the polarizer or analyzer subassemblies includes a spatially variant polarization element having a polarization property varying along the first axis
Implementation Method 2
a photodetector array downstream of the analyzer subassembly, the photodetector array extending along the first axis for detecting the light beam propagated through the analyzer subassembly
Data Source
AI summary
An alignment apparatus for a polarization device includes a polarizer subassembly for polarizing a light beam, a rotary support for rotatably supporting the polarization device in a path of the light beam downstream of the polarizer subassembly, an analyzer subassembly downstream of the rotary support for receiving the light beam propagated through the polarization device, and a photodetector array disposed downstream of the analyzer subassembly and extending along the width dimension of the light beam for detecting the light beam propagated through the analyzer subassembly. At least one of the polarizer or analyzer subassemblies includes a spatially variant polarization element having a polarization property varying along the width dimension of the light beam.