Columnar Optical Element Array for Oblique-Light Image Sensors
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Solution Overview
Problem
Micro-structured lenses using effective medium approximation face limitations due to large aspect ratios and polarization dependence, especially when a significant difference in refractive indices occurs, making them difficult to manufacture and limiting light receiving efficiency.
Innovation Solution
An imaging element with a pixel array and an optical element array featuring columnar structure bodies with a refractive index higher than the surrounding material, formed at the same height and optimized in width to provide phase characteristics for guiding light according to incident angles, allowing for efficient light focusing and reduced aspect ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a micro-structured lens using effective medium approximation is used, then lens characteristics can be achieved, but the aspect ratio becomes large and manufacturing difficulty increases
Solution Approach 1:
The patent changes the refractive index parameter of the lens material from low (SiO2, n=1.45) to high (TiO2, n=2.4; SiN, n=2.05), which fundamentally alters the optical path length and allows achieving the same lens effect with much smaller physical dimensions, thereby reducing aspect ratio and easing manufacturing
Solution Approach 2:
The patent divides the lens into a two-dimensional array of independent columnar structure bodies, where each column acts as an individual optical element. This segmentation allows each column to be manufactured independently using standard semiconductor processes, avoiding the need to manufacture complex curved surfaces as a single monolithic structure
2Reliability
If a micro-structured lens with large refractive index difference is used, then optical confinement is improved, but polarization dependence increases
Solution Approach 1:
The patent uses asymmetric unit cell designs where the columnar structure bodies have different width configurations in orthogonal directions (e.g., different widths in x and y directions). This controlled asymmetry, combined with specific refractive index materials, achieves optical confinement while managing polarization effects through geometric phase control
Solution Approach 2:
The patent employs composite material systems combining high refractive index materials (TiO2, SiN) with low refractive index materials (SiO2, air), creating a composite optical structure that achieves strong optical confinement while the geometric design compensates for polarization dependence
3Reliability
If lenses optimized for oblique incident light are manufactured, then light receiving efficiency in circumferential portion is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by making each columnar structure body in the array have different width dimensions tailored to the specific incident angle requirements of its position in the sensor array. Central columns have different dimensions than circumferential columns, optimizing light receiving efficiency for oblique incident light at each location while using the same simple columnar geometry throughout
Solution Approach 2:
The patent creates a universal columnar structure body design that can serve multiple functions: it acts as both a lens element and a waveguide, and by adjusting the width parameter, the same basic structure can be optimized for different incident angles across the sensor array, eliminating the need for fundamentally different structures
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 enables imaging elements with lower aspect ratios and simpler configurations, effectively addressing the limitations of micro-structured lenses by optimizing light receiving efficiency and reducing manufacturing complexity, while providing lens characteristics corresponding to main incident angles for each pixel.
Implementation Method 1
the plurality of columnar structure bodies are formed in a width having a phase characteristic for guiding light to a photoelectric conversion element directly below a columnar structure body in accordance with an incident angle of the incident light of each columnar structure body
Implementation Method 2
the plurality of columnar structure bodies have a refractive index so that they have a phase characteristic for guiding light to the photoelectric conversion element directly below a columnar structure body
Data Source
AI summary
An imaging element (100) includes: a pixel array (110) in which a plurality of pixels including photoelectric conversion elements are arranged in a two-dimensional array; and an optical element array (120) in which optical elements composed of a plurality of columnar structure bodies (160) arranged opposite to a pixel array (110) and guiding incident light to a corresponding photoelectric conversion element are arranged in a two-dimensional array, in which the plurality of columnar structure bodies (160) are formed in a width having a phase characteristic for guiding light to a photoelectric conversion element directly below a columnar structure body in accordance with an incident angle of the incident light of each columnar structure body (160) when viewed in a plan view and are formed at a same height when viewed in a side view.