Imaging Photodetection Device Using Diffractive Microlens Array
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Solution Overview
Problem
Conventional imaging photodetection devices face limitations in miniaturization and increasing pixel density due to inefficient light utilization and excessive light diffusion, leading to noise and focusing issues.
Innovation Solution
The use of a photodetection device with a low refractive index transparent layer and embedded high refractive index transparent sections that separate light through optical diffraction, allowing for improved light utilization and increased pixel density without the need for color filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If color filters are used to separate light wavelengths, then spectral selectivity is improved, but light utilization efficiency deteriorates
Solution Approach 1:
The patent replaces the conventional color filter system (which absorbs light) with a microlens array system that redirects light through total internal reflection. This substitution changes the mechanism from absorption-based wavelength separation to geometry-based light routing, achieving spectral selectivity without energy loss through absorption.
Solution Approach 2:
The invention changes the optical parameters by using microlenses with specific refractive indices and curvature radii, combined with precisely controlled spacing between the microlens array and photodetector array. This parameter optimization enables wavelength separation through constructive and destructive interference patterns, achieving spectral discrimination without color filters.
2Productivity
If photodetector spacing is reduced to increase pixel density, then productivity is improved, but light focusing performance deteriorates
Solution Approach 1:
The patent introduces an intermediary microlens array positioned between the incident light and the photodetector array. This microlens system acts as a mediator that focuses and redirects light from wider areas onto closely spaced photodetectors, enabling high pixel density while maintaining effective light focusing through the intermediary optical elements.
Solution Approach 2:
The invention utilizes the spatial dimension by positioning the microlens array at a specific distance above the photodetector array, creating a three-dimensional optical path. This vertical dimension allows light from larger horizontal areas to be focused onto closely spaced photodetectors, decoupling pixel density from focusing performance constraints.
3Area of moving object
If microlens size is reduced to accommodate higher pixel density, then area is improved, but light gathering capability deteriorates
Solution Approach 1:
The patent segments the light gathering function from the photodetector area by introducing separate microlens elements. Each microlens acts as an independent light gathering unit with optimized size, while the photodetectors can be smaller and more densely packed. The microlens array collectively captures light from larger areas and distributes it to multiple photodetectors.
Solution Approach 2:
The microlens array performs multiple functions: it focuses light, separates wavelengths through interference patterns, and distributes light to multiple photodetectors. This multi-functionality allows the system to maintain effective light gathering capability even with smaller individual optical elements, as the collective array provides the necessary light collection area.
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 enhances light utilization efficiency, enables smaller microlenses, and increases pixel density while maintaining practical dimensions, improving focusing performance and reducing noise.
Implementation Method 1
Light entering the low refractive index transparent layer and the high refractive index transparent sections passes therethrough to be separated into a 0th-order diffracted light, a 1st-order diffracted light and −1st-order diffracted light by a phase shift occurring on the wavefront
Implementation Method 2
The microlenses 10 function for refracting light such as a light beam 11a′ that enters with a shift relative to the central axis of the microlens 10 and guiding the light to the photodetector 6
Implementation Method 3
Light focused by the microlens 10 is received by the photodetector 6 located just under the microlens 10, and photoelectrically converted
Data Source
AI summary
An imaging photodetection device includes a plurality of photodetectors (6) arrayed on a substrate (5) one-dimensionally or two-dimensionally, a low refractive index transparent layer (12) formed above the plural photodetectors, and a plurality of columnar or plate-like high refractive index transparent sections (13) embedded in the low refractive index transparent layer along the array direction of the plural photodetectors. At least two of the photodetectors correspond to one of the high refractive index transparent sections. Light entering the low refractive index transparent layer and the high refractive index transparent sections passes therethrough to be separated into a 0th-order diffracted light, a 1st-order diffracted light and a −1st-order diffracted light by a phase shift occurring on the wavefront. Thereby, improvement in the efficiency for light utilization and pixel densification can be realized.