Nano-optical Micro-lens Array for Image Sensor Autofocus and Crosstalk
Solution Overview
Problem
As image sensors with increasing resolution have smaller unit pixels, they face challenges in low-light sensitivity and performance degradation due to chief ray angle variations, particularly in autofocus (AF) function and crosstalk reduction.
Innovation Solution
The implementation of a nano-optical micro-lens array with a high fill factor, specifically designed to improve autofocus performance and reduce crosstalk, where each nano-optical micro-lens includes nanostructures arranged in a specific pattern to optimize light condensation and pixel alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of image sensors is increased, then the detail imaging capability is improved, but the size of unit pixels decreases causing degradation in low-light sensitivity and autofocus performance
Solution Approach 1:
The micro-lens is divided into multiple nano-optical micro-lenses arranged in an array, where each nano-optical micro-lens corresponds to a specific pixel. This segmentation allows light to be focused more precisely onto individual pixels, improving both resolution and light collection efficiency even as pixel sizes decrease.
Solution Approach 2:
The patent transitions from conventional two-dimensional micro-lens structures to three-dimensional nano-optical micro-lenses with vertical nanostructures. These nanostructures extend in the depth direction, creating a multi-dimensional light condensation effect that enhances light gathering capability while maintaining small pixel footprints.
2Measurement precision
If the pixel size is reduced to increase resolution, then the imaging detail is improved, but the autofocus function and crosstalk reduction performance deteriorate
Solution Approach 1:
Each nano-optical micro-lens is customized with a specific arrangement of nanostructures tailored to its position in the array. Central pixels have different nanostructure configurations compared to peripheral pixels, optimizing light condensation and autofocus performance for each local region while maintaining high resolution across the entire sensor.
3Ease of manufacture
If conventional micro-lens configurations are used, then the manufacturing process is simpler, but the chief ray angle variation performance and crosstalk reduction are insufficient
Solution Approach 1:
The patent replaces conventional mechanical micro-lens fabrication with a nanostructure-based optical system. The nanostructures are formed using advanced nanofabrication techniques that enable precise control over light paths, effectively reducing crosstalk and chief ray angle variations despite increased manufacturing complexity.
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 nano-optical micro-lens array enhances autofocus performance by improving light condensation and reducing crosstalk between adjacent pixels, thereby maintaining image quality across varying light conditions and chief ray angles.
Implementation Method 1
each of the plurality of nano-optical micro-lenses may include a plurality of nanostructures to condense the incident light onto a corresponding pixel
Data Source
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AI summary
An image sensor includes a sensor substrate including a plurality of pixels sensing incident light, a nano-optical micro-lens array including a plurality of nano-optical micro-lenses respectively corresponding to the plurality of pixels, and a color filter array disposed between the sensor substrate and the nano-optical micro-lens array and including a plurality of color filters. Each of the plurality of nano-optical micro-lenses includes a plurality of nanostructures to condense the incident light onto a corresponding pixel, and when viewed in a cross-section of the nano-optical micro-lens array, a fill factor denotes a ratio of an area of the nanostructures arranged within a reference circle among the plurality of nanostructures included in one of the plurality of nano-optical micro-lenses, and the reference has a pixel size corresponding to the one nano-optical micro-lens as a diameter, the fill factor is greater than or equal to 95 %.