Polarimetric Camera Angular Filters Reduce Crosstalk
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Solution Overview
Problem
Existing polarimetric camera configurations face limitations such as reduced performance due to small polarizing filters, polarization crosstalk, and image overlapping, which affect the quality of polarization-separated images.
Innovation Solution
A polarimetric camera design that includes an optical system with a polarization separator and angular filters, allowing for the formation of spatially distinct images for each polarization state on a standard image sensor, while filtering out parasitic light beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If polarization separation is performed at the image sensor using polarizing filters, then polarization states can be separated, but the performance is reduced due to the small size of polarizing filters and polarization crosstalk occurs
Solution Approach 1:
The patent introduces an intermediary optical element (polarization separator) between the optical system and the image sensor. This polarization separator performs the polarization separation function in the optical path rather than at the pixel level, allowing standard image sensors to be used while achieving clean polarization separation without crosstalk or performance degradation.
2Measurement precision
If polarization separation is performed at the optical system using a polarization separator, then one image per polarization state can be formed, but image overlapping occurs between different polarization states
Solution Approach 1:
The patent segments the image sensor into multiple subsets of pixels, where each subset is associated with a specific exit pupil corresponding to a different polarization state. This segmentation allows each polarization state to be captured by dedicated pixels, preventing overlap and enabling precise spatial separation of polarization images.
3Measurement precision
If a polarization separator is used to separate polarization states, then multiple images per polarization state can be formed, but a non-polarized zero-order diffraction image appears around the optical axis
Solution Approach 1:
The patent extracts and separates the zero-order diffraction image from the polarization-separated images by assigning it to a dedicated subset of pixels. This allows the zero-order image to be captured independently without interfering with the polarization state measurements, effectively removing this harmful factor from the polarization imaging process.
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 design improves the quality of images associated with different polarization states by filtering out unwanted light, reducing crosstalk, and allowing the use of standard image sensors, thereby enhancing the overall performance of the polarimetric camera.
Implementation Method 1
a polarization separator adapted to divert the incident light beams coming from the scene to be imaged according to the N polarization states
Implementation Method 2
the image sensor including at least N angular filters located between the optical system and the photodetectors, each angular filter being adapted to transmit, to a subset of pixels, the incident light beams coming from the associated exit pupil, and to at least partly filter the incident light beams coming from the other exit pupil or pupils
Data Source
AI summary
A polarimetric camera includes an optical system and an image sensor. The optical system (i) forms, on the image sensor, N images of a scene to be imaged, with N greater than or equal to 2, N being a number of polarization states, (ii) includes a polarization separator diverting the light beams coming from the scene according to the N polarization states, and (iii) has N exit pupils. The image sensor includes a plurality of detection pixels distributed in N subsets of pixels. Each subset is associated with an exit pupil and receives the incident light beams according to the polarization state of the associated exit pupil. The image sensor includes at least N angular filters, each angular filter transmitting, to a subset of pixels, the light beams coming from the associated exit pupil, and filtering the other light beams.