Nanophotonic Microlens Array for Optical Sensor Light Loss
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Solution Overview
Problem
Optical sensors face light loss and decreased sensitivity due to deep trench isolation structures and increasing chief ray angles, especially at the edges, which complicates image processing and reduces image quality.
Innovation Solution
A nanophotonic microlens array is designed to redirect incident light away from the center of deep trench isolation structures and optimize light collection on photosensitive cells, minimizing light loss and enhancing sensitivity by using a phase profile with convex regions that correspond to the number and arrangement of photosensitive cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an optical lens array is used to collect incident light on pixels with DTI structure for autofocusing, then the AF technique can be implemented, but light loss occurs due to light being absorbed by the DTI structure at the pixel center
Solution Approach 1:
The patent applies local quality by designing different regions within each microlens with distinct optical functions. Specifically, each microlens is divided into a first region (central area) and a second region (peripheral area), where the first region directs light to the DTI structure for AF measurement while the second region directs light to the photosensitive cells for image capture. This spatial differentiation of optical paths resolves the contradiction by ensuring that AF functionality is achieved without compromising light utilization for imaging.
Solution Approach 2:
The patent segments the microlens structure into multiple functional regions - specifically dividing each microlens into a first region corresponding to the DTI structure area and a second region corresponding to the photosensitive cell area. This segmentation allows independent optimization of light paths: one path for autofocusing measurement and another for image capture, thereby eliminating the trade-off between AF capability and light loss.
2Volume of moving object
If the optical sensor is miniaturized, then the device size is reduced, but the chief ray angle at the edge increases causing decreased pixel sensitivity and dark edges
Solution Approach 1:
The patent applies parameter changes by modifying the optical parameters of the microlens array, specifically the focal length and curvature radius of the microlenses. By optimizing these parameters, the patent achieves effective light collection even for oblique incident rays at the sensor edges, thereby maintaining pixel sensitivity without increasing sensor size. This parameter optimization resolves the contradiction between miniaturization and edge sensitivity.
3Reliability
If light is collected on the center of the DTI structure to implement AF technique, then autofocusing is achieved, but the amount of incident light collected on photosensitive cells is reduced
Solution Approach 1:
The patent segments the light collection function by spatially separating the light paths within each microlens. The first region of each microlens is dedicated to collecting light on the DTI structure for AF measurement, while the second region is dedicated to collecting light on the photosensitive cells for image capture. This segmentation ensures that both AF function and light collection efficiency operate simultaneously without competing for the same light resources.
Solution Approach 2:
The patent introduces the microlens structure as an intermediary optical element that mediates between incident light and the two different targets (DTI structure and photosensitive cells). By designing the microlens with specific regional characteristics, it acts as a mediator that divides and directs light to different destinations based on spatial position, thereby enabling both AF measurement and efficient image capture without direct competition.
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 nanophotonic microlens array effectively reduces light loss on deep trench isolation structures and improves sensitivity at the edges of optical sensors, leading to better image quality and reduced computational burden in image processing.
Implementation Method 1
a nanophotonic microlens array provided on the filter layer and including a plurality of nanophotonic microlenses, each of the plurality of nanophotonic microlenses being configured to focus incident light on a corresponding pixel among the plurality of pixels
Data Source
AI summary
An optical sensor includes: a sensor substrate including a plurality of pixels that sense incident light, a filter layer arranged on the sensor substrate and including a plurality of filters corresponding to the plurality of pixels, the plurality of filters transmitting only light of a particular wavelength band, and a nanophotonic microlens array arranged on the filter layer and including a plurality of nanophotonic microlenses, each of which focuses incident light on a corresponding pixel among the plurality of pixels.