Image Sensor Pixel Structure With Variable Light Shields
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Solution Overview
Problem
In solid-state imaging devices, the existing inter-color-filter light-shielding portions do not effectively prevent optical color mixing and reduce image quality due to inadequate light blocking between pixel units with different on-chip lens sizes, leading to reduced sensitivity and image quality.
Innovation Solution
A solid-state imaging device with a lattice-shaped inter-color-filter light-shielding portion of varying heights surrounding color filters, where the height surrounding larger on-chip lenses is greater than that between smaller on-chip lenses, to prevent oblique light from entering adjacent pixel units and reduce optical color mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the height of inter-color-filter light-shielding portions is increased to prevent optical color mixing, then image quality is improved, but sensitivity is reduced due to excessive light blocking
Solution Approach 1:
The patent applies local quality by setting different heights for inter-color-filter light-shielding portions based on the size of on-chip lenses in different pixel units. Specifically, pixel units with larger on-chip lenses have taller light-shielding portions, while those with smaller lenses have shorter portions. This localized differentiation prevents optical color mixing in regions where it occurs while preserving light sensitivity in regions where it is less critical.
2Reliability
If larger on-chip lenses are used to improve light collection, then sensitivity is enhanced, but optical color mixing increases due to wider light paths
Solution Approach 1:
The patent addresses this contradiction by implementing locally differentiated light-shielding heights that correspond to the spatial distribution of on-chip lens sizes. Larger on-chip lenses that are more prone to optical color mixing are paired with taller light-shielding portions, while smaller lenses use shorter portions. This creates a matched system where each pixel unit's light-shielding configuration is optimized for its specific lens characteristics.
3Ease of manufacture
If uniform light-shielding height is used across all pixel units, then manufacturing is simplified, but image quality deteriorates due to inadequate suppression of optical color mixing in certain regions
Solution Approach 1:
The patent resolves this contradiction by introducing local differentiation in light-shielding heights only where necessary - specifically, taller portions are used only for pixel units with larger on-chip lenses that require enhanced color mixing prevention. This approach maintains manufacturing simplicity for the majority of uniform pixel units while applying enhanced local structures only where performance demands it.
Solution Approach 2:
The patent applies segmentation by dividing the light-shielding structure into multiple height levels corresponding to different pixel unit types. This segmentation allows the manufacturing process to handle the majority of uniform regions efficiently while applying differentiated structures to specific segments (pixel units with larger lenses) that require enhanced performance.
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 configuration enhances image quality by improving light collection and sensitivity while minimizing optical color mixing, allowing for higher quality image acquisition.
Implementation Method 1
an inter-color-filter light-shielding portion formed on a side of light incident surfaces of the photoelectric conversion units so as to surround the respective color filters
Implementation Method 2
a plurality of pixel units including on-chip lenses, color filters, and photoelectric conversion units
Data Source
AI summary
Provided is a solid-state imaging device capable of acquiring an image with higher image quality. It includes a plurality of pixel units including on-chip lenses, color filters, and photoelectric conversion units. The plurality of pixel units includes a first pixel unit (e.g., a pixel unit of an imaging pixel) and a second pixel unit (e.g., a pixel unit of a phase-difference detection pixel), the first pixel unit including an on-chip lens of a predetermined size, the second pixel unit including an on-chip lens of a size larger than the predetermined size, the first pixel unit including first pixel units, the second pixel unit including second pixel units. A height of an inter-CF light-shielding portion surrounding the respective color filters of the second pixel units is larger than a height of an inter-CF light-shielding portion between the color filters of the first pixel units.