Solid Immersion Lens Focal Plane Array Sub-Diffraction Spot
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Solution Overview
Problem
Focal plane arrays face limitations in reducing pixel size due to diffraction constraints, leading to increased dark current and noise, which affects imaging performance and requires larger optical systems, while maintaining a field of view and signal collection.
Innovation Solution
The implementation of a solid immersion lens (SIL) that reduces the spot size of incident light below diffraction limits, allowing for smaller pixel sizes and reduced dark current, achieved by configuring the focal plane array in optical contact with the SIL, which effectively magnifies the pixels without increasing physical size, enabling a more compact and cost-efficient optical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to improve resolution and reduce dark current, then imaging precision improves, but diffraction constraints cause increased noise and signal loss
Solution Approach 1:
A solid immersion lens is introduced as an intermediary optical element between the incident light and the pixel array. The lens focuses light onto the pixels while being in optical contact with the focal plane array, enabling sub-diffraction-limited spot sizes to be achieved without increasing pixel physical dimensions. This mediator allows precise light control at the pixel level while maintaining diffraction-limited performance.
Solution Approach 2:
The patent changes the optical parameters by using a solid immersion lens with specific refractive index and curvature to achieve a reduced spot size. The lens transforms the light distribution from a diffraction-limited pattern to a smaller, more concentrated spot that can be delivered to smaller pixels. This parameter transformation enables the system to break the conventional diffraction barrier for pixel size reduction.
2Reliability
If pixel size is reduced to minimize dark current, then signal-to-noise ratio improves, but the optical system requires larger aperture to maintain field of view
Solution Approach 1:
The solid immersion lens introduces an additional optical dimension by creating a virtual image of the focal plane array at a different location. This dimensional transformation allows the system to maintain a compact physical aperture while achieving an effectively larger collecting area through the lens-induced virtual imaging, thus maintaining field of view without requiring proportionally larger physical aperture.
3Length of moving object
If solid immersion lens is used to reduce spot size below diffraction limit, then pixel size can be reduced, but lens manufacturing precision requirements increase
Solution Approach 1:
The optical system is segmented into distinct functional components: the solid immersion lens for light focusing, the focal plane array for detection, and the virtual image formation for optical coupling. This segmentation allows each component to be optimized independently, with the lens designed for specific refractive index and curvature properties rather than requiring perfect geometric precision throughout the entire 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
This approach enables smaller, more sensitive, and cost-effective focal plane arrays with reduced dark current and noise, maintaining or increasing the field of view while minimizing pixel size, thus improving imaging performance and reducing the need for extensive cooling systems.
Implementation Method 1
directing the incident light to the optical system including a solid immersion lens... focusing, by the solid immersion lens, the incident light on the focal plane array
Implementation Method 2
each photosensor includes a p-n junction configured to output a current indicative of an amount of light incident on the p-n junction
Data Source
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AI summary
Aspects of the present disclosure are directed to an optical system including a solid immersion lens including a first surface and a second surface, and a focal plane array comprising a plurality of pixels, the focal plane array being configured to be in optical contact with the first surface of the solid immersion lens. In one embodiment, the first surface is a planar surface and the second surface is a non-planar surface. In an embodiment, the solid immersion lens is an aspherical lens.