Image Sensor Pixel Layout Using Refractive Index Split for HDR
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Solution Overview
Problem
Conventional photoelectric conversion apparatuses have insufficient sensitivity differences between photodiodes, limiting their ability to capture images with high dynamic range in scenes with large contrast variations, such as those encountered in in-vehicle or security cameras.
Innovation Solution
The apparatus incorporates a substrate with a pixel structure featuring a high refractive index member and a low refractive index member, strategically positioned near the light incidence surface to enhance the sensitivity difference between large and small photoelectric conversion portions, allowing for a wider dynamic range by concentrating light on the high sensitivity photodiodes while reducing light on low sensitivity ones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple photodiodes with different sensitivities are combined to achieve high dynamic range, then the dynamic range is improved, but the sensitivity difference between photodiodes is insufficient
Solution Approach 1:
The patent applies local quality by forming members with different refractive indexes at different locations corresponding to different photoelectric conversion portions. Specifically, a first member with a first refractive index is formed over the first photoelectric conversion portion, and a second member with a second refractive index is formed over the second photoelectric conversion portion, creating localized optical property variations that enhance sensitivity differentiation.
Solution Approach 2:
The patent changes the refractive index parameter of the members formed over the photodiodes to control light distribution. By selecting members with different refractive indexes (first refractive index for high sensitivity photodiode, second refractive index for low sensitivity photodiode), the patent optimizes light concentration or dispersion to achieve sufficient sensitivity difference between photodiodes.
2Manufacturing precision
If members with different refractive indexes are formed to enhance sensitivity difference, then the sensitivity difference is improved, but the device structure becomes more complex
Solution Approach 1:
The patent merges the optical control function with the existing pixel structure by integrating members having different refractive indexes directly into the photoelectric conversion unit. These members are formed as part of the overall pixel structure, combining multiple functions (light guidance, sensitivity control) into a unified design rather than adding separate complex subsystems.
Solution Approach 2:
Instead of adding complex mechanical or structural mechanisms to control sensitivity, the patent changes the optical parameter (refractive index) of existing structural members. This approach achieves sensitivity differentiation through material property selection rather than through complex structural arrangements, thereby reducing overall device complexity.
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 increases the sensitivity difference between photodiodes, enabling a higher dynamic range than conventional sensors at the same pixel pitch, effectively capturing a broader range of light intensities without saturation.
Implementation Method 1
A refractive index of the first member is higher than a refractive index of the second member
Implementation Method 2
A refractive index of the first member is higher than a refractive index of the second member
Implementation Method 3
a pixel with a color filter is formed. The pixel includes a first photoelectric conversion portion and a second photoelectric conversion portion
Data Source
AI summary
An apparatus includes a substrate on which a pixel with a color filter is formed. The pixel includes a first conversion portion and a second conversion portion in an in-plane direction of the substrate, the second conversion portion having a lower sensitivity to light than a sensitivity of the first conversion portion. In a depth direction of the substrate, the apparatus includes a first member between the first conversion portion and the color filter and a second member between the second conversion portion and the color filter in a depth direction of the substrate. The first member is adjacent to the second member in the in-plane direction of the substrate. A refractive index of the first member is higher than a refractive index of the second member.