Imaging Device Diffractive Refractive Index Layers
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Solution Overview
Problem
Conventional imaging photodetection devices face limitations in miniaturization and pixel density due to inefficient light utilization and focusing performance, primarily because of the use of color filters for light separation and the size requirements of microlenses.
Innovation Solution
The device employs a transparent low refractive index layer with embedded columnar or plate-like high refractive index sections that diffract light into 0th-order, 1st-order, and −1st-order diffracted light, 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 for light separation, 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 diffractive optical system using transparent resin layers with periodic refractive index variations. This substitution changes the light separation mechanism from absorption-based to diffraction-based, enabling spectral separation without the energy losses inherent in absorptive filters.
Solution Approach 2:
The invention changes the fundamental parameter of light-matter interaction from absorption (color filters) to diffraction (periodic refractive index structures). By modifying the refractive index distribution periodically in the transparent resin layers, the system achieves wavelength-dependent light routing through diffraction orders rather than absorption, thereby improving light utilization efficiency while maintaining spectral selectivity.
2Productivity
If microlens size is reduced to increase pixel density, then productivity is improved, but focusing performance deteriorates
Solution Approach 1:
The patent replaces conventional microlenses with diffractive optical elements formed by periodic refractive index variations in transparent resin layers. This substitution eliminates the need for large-sized microlenses, as the diffractive structures can achieve effective light focusing and routing at much smaller dimensions, thereby enabling higher pixel density while maintaining optical performance.
Solution Approach 2:
The invention transitions from three-dimensional microlens structures to two-dimensional periodic refractive index patterns in thin transparent resin layers. This dimensional reduction allows for compact optical functionality with smaller feature sizes, enabling higher pixel density without sacrificing focusing capability.
3Productivity
If photodetector spacing is reduced to increase pixel density, then productivity is improved, but light separation performance deteriorates
Solution Approach 1:
The patent introduces a vertical dimension with multiple transparent resin layers having different periodic structures. This multi-layer diffractive system achieves spectral separation in the depth direction, allowing closely spaced photodetectors to receive wavelength-separated light through different diffraction orders from different layers, thereby maintaining light separation performance at reduced pixel pitch.
Solution Approach 2:
The invention segments the light separation function across multiple transparent resin layers, with each layer contributing to the overall diffractive optical effect. This segmentation allows for compact lateral spacing while achieving complete spectral separation through the cumulative effect of multiple diffractive layers.
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 detection of multiple color information per microlens, and reduces the spacing between photodetectors, achieving a higher pixel density and practical dimensions for the photodetection device.
Implementation Method 1
Light that enters the transparent low refractive index layer and the transparent high refractive index section passes therethrough to be separated into 0th-order diffracted light, 1st-order diffracted light and −1st-order diffracted light.
Data Source
AI summary
An imaging photodetection device (4) includes: a plurality of photodetectors (6) that are arrayed on a substrate (5) at least along a first direction; a transparent low refractive index layer (12) that is formed above the plurality of photodetectors; and a plurality of transparent high refractive index sections (13) that are embedded in the transparent low refractive index layer along the first direction. On a cross-section of the transparent high refractive index sections orthogonal to the substrate and along the first direction, central axes (14) of the transparent high refractive index sections are bent stepwise. Light that enters the transparent low refractive index layer and the transparent high refractive index section passes therethrough to be separated into 0th-order diffracted light, 1st-order diffracted light, and −1st-order diffracted light. Thereby, improvement in the efficiency of light utilization and pixel densification can be realized.