Image Sensor Color Filter Curvature for Pixel Light Path Control
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Solution Overview
Problem
Existing image sensors face challenges in optimizing the optical path for each pixel and reducing channel differences, particularly due to variations in the angle of incident light and differences in refractive indices for red, green, and blue light.
Innovation Solution
The image sensor incorporates a substrate with photoelectric conversion regions, color filters positioned on the substrate's surface, and a microlens layer. The upper surface of at least one color filter has a concave curved surface, with varying curvatures for different color filters to optimize the optical path and reduce channel differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microlens is used to focus incoming light, then pixel sensitivity is increased, but channel difference problems occur where light passes into adjacent pixels instead of the intended pixel
Solution Approach 1:
The patent applies different curvature radii to microlenses based on their position and function. Specifically, microlenses corresponding to different color filters (R, G, B) have different curvature radii, and microlenses in different regions (central vs. outer) have different curvature radii. This local differentiation optimizes light focusing for each pixel while preventing light from entering adjacent pixels, thus resolving the channel difference problem while maintaining high pixel sensitivity.
2Adaptability or versatility
If color filters with different wavelengths (R, G, B) are used, then color detection is enabled, but focal points differ due to different refractive indices
Solution Approach 1:
The patent assigns different curvature radii to microlenses based on the color filter they correspond to. Since different colors (R, G, B) have different refractive indices and thus different focal points, the patent locally adjusts the curvature radius of each microlens to compensate for these differences. This ensures that all colors focus at the same point, maintaining manufacturing precision while preserving color detection capability.
Solution Approach 2:
The patent changes the physical parameter of curvature radius for microlenses based on the wavelength characteristics of different colors. By adjusting the curvature radius parameter according to the specific color filter (R, G, or B), the patent compensates for refractive index differences and achieves consistent focal points across all colors, thereby resolving the focal point consistency issue while maintaining color detection versatility.
3Area of stationary object
If the image sensor covers a large area, then more pixels are captured, but channel difference problems worsen in outer areas
Solution Approach 1:
The patent differentiates microlens curvature radii based on their position within the image sensor. Microlenses in the central region have one curvature radius, while microlenses in the outer region have a different curvature radius. This local adaptation compensates for the worsening channel difference in outer areas, allowing the image sensor to maintain high precision across its entire large area without suffering from the channel difference problem that typically affects outer regions.
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 optimizes the optical path for each pixel, reduces channel differences, and improves sensitivity and auto-focus contrast, particularly in the outer areas of the image sensor.
Implementation Method 1
A microlens serves to focus incoming light into the positive electrode region
Implementation Method 2
wavelengths of red (R), green (G), and blue (B) light are different, so after red, green, and blue light passes through microlenses
Implementation Method 3
The photodiode plays a role of converting incident light into an electrical signal
Data Source
AI summary
An image sensor including a first substrate including first and second surfaces facing each other and a plurality of photoelectric conversion regions, a plurality of color filters positioned on the second surface of the substrate, the plurality of color filters including a first color filter, a second color filter, and a third color filter; and a microlens layer including a plurality of microlenses and positioned to overlap each of the color filters. An upper surface of at least one of the first color filter, the second color filter, or the third color filter has a concave curved surface, and curvature of the upper surface of the third color filter is different from curvature of the upper surface of the second color filter or curvature of the upper surface of the first color filter.