Metasurface Polarimetric Image Sensor for Higher Quantum Efficiency
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Solution Overview
Problem
Existing polarimetric image sensors face limitations in measuring light polarization information due to bulky acquisition systems and reduced sensitivity caused by polarizing filters, which require successive image acquisitions and block part of the light signal.
Innovation Solution
A polarimetric image sensor integrated into a semiconductor substrate, featuring a two-dimensional metasurface and polarizing filters with metal bars coated in tungsten, silicon, and dielectric layers, which routes and filters light according to distinct polarizations, enhancing sensitivity and reducing bulkiness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If polarizing filters are placed in front of the image sensor to measure polarization information, then polarization measurement capability is improved, but the quantum efficiency and sensitivity of the sensor deteriorate because the filters block part of the light signal
Solution Approach 1:
The patent replaces conventional bulk polarizing filters with a metasurface structure that uses sub-wavelength resonant elements to manipulate light polarization. This metasurface achieves polarization measurement without significantly blocking light, thereby maintaining high quantum efficiency while enabling polarization information capture.
Solution Approach 2:
The patent changes the operational parameters by using resonant frequencies of the metasurface elements to match the wavelength of incident light. This resonance condition allows the metasurface to interact strongly with polarized light for measurement while minimizing overall light transmission loss, thus resolving the contradiction between measurement capability and quantum efficiency.
2Measurement precision
If a mechanism with multiple polarizers is used to change polarizer orientation between acquisitions, then polarization state measurement capability is improved, but the device complexity and bulkiness increase
Solution Approach 1:
The patent merges multiple polarizer functions into a single integrated metasurface structure. Instead of using separate polarizers that require mechanical rotation, the metasurface contains multiple resonant elements with different orientations that can simultaneously or sequentially measure different polarization states, greatly simplifying the overall system architecture.
Solution Approach 2:
The patent transitions from a one-dimensional mechanical rotation approach to a two-dimensional metasurface array where polarization measurement is achieved through spatial distribution of resonant elements with different orientations. This dimensional change eliminates the need for mechanical movement while maintaining full polarization measurement capability.
3Loss of information
If successive image acquisitions are performed with different polarizers to record multiple polarization states, then comprehensive polarization information is improved, but the acquisition time increases which is problematic when the scene varies over time
Solution Approach 1:
The patent prepares multiple polarization-sensitive resonant elements in advance within the metasurface structure, each oriented to detect specific polarization components. This preliminary configuration allows the system to capture multiple polarization states simultaneously in a single exposure, eliminating the need for successive acquisitions and preventing information loss due to scene changes during measurement.
Solution Approach 2:
The patent enables continuous polarization measurement by having all polarization-sensitive elements active simultaneously throughout the exposure time. This continuous action ensures that comprehensive polarization information is captured without interruption, maintaining accuracy even when the scene varies dynamically during acquisition.
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 solution improves the quantum efficiency of the image sensor by allowing simultaneous measurement of multiple polarizations without blocking light, enabling more efficient light routing and enhanced image acquisition capabilities.
Implementation Method 1
a polarization router comprising a two-dimensional metasurface arranged on the side of the polarizing filter opposite to the photodetectors, the metasurface comprising a two-dimensional array of pads
Implementation Method 2
a polarizing filter arranged on the side of an illumination surface of the photodetectors, the filter comprising, for each pixel, a polarizing structure
Implementation Method 3
a plurality of pixels, each comprising a photodetector formed in the semiconductor substrate
Data Source
AI summary
A polarimetric image sensor formed inside and on top of a semiconductor substrate, the sensor including: —a plurality of pixels, each including a photodetector formed in the semiconductor substrate; —a polarization router including a two-dimensional metasurface arranged on the side of an illumination surface of the photodetectors, the metasurface including a two-dimensional array of pads; and—a plurality of first microlenses extending in front of a pair of adjacent pixels of the sensor.