Split Pixel Image Sensor Attenuation Layer Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Image sensors with split pixel structures face challenges in high intensity light sensing due to high angle light causing saturation of small photodiodes, which affects their sensitivity and dynamic range performance.
Innovation Solution
An attenuation layer is extended above small photodiodes and partially over large photodiodes to block high angle light, preventing saturation and improving sensitivity by controlling light exposure, while metal patterns enhance isolation and light management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If small photodiodes are used for high intensity light sensing, then dynamic range is improved, but high angle light causes saturation reducing sensitivity
Solution Approach 1:
The patent applies local quality by creating different photodiode sizes within the same pixel structure. Small photodiodes are positioned to receive high angle light for high intensity scenes, while large photodiodes receive low angle light for low intensity scenes. This spatial differentiation of photodiode sizes allows each region to be optimized for its specific light condition, resolving the contradiction between dynamic range and sensitivity.
Solution Approach 2:
The pixel structure is segmented into multiple photodiodes of different sizes (small and large photodiodes) within a single pixel. This segmentation allows the pixel to handle different light intensities simultaneously by directing high angle light to small photodiodes and low angle light to large photodiodes, thereby achieving both extended dynamic range and maintained sensitivity across varying light conditions.
2Measurement precision
If attenuation layer is extended over large photodiodes to block high angle light, then small photodiode sensitivity is improved, but large photodiode light exposure is reduced
Solution Approach 1:
The attenuation layer is applied locally and selectively only over the small photodiodes, not over the large photodiodes. This local application blocks high angle light specifically for the small photodiodes to prevent saturation and improve sensitivity, while leaving the large photodiodes fully exposed to capture low angle light effectively, thus resolving the contradiction between small photodiode sensitivity and large photodiode light exposure.
3Adaptability or versatility
If split pixel structure with different sized photodiodes is implemented, then dynamic range is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent segments the pixel into multiple photodiodes of different sizes that can be formed using standard semiconductor fabrication processes. By integrating these segmented photodiodes into a unified pixel structure with shared readout circuitry, the design achieves extended dynamic range while managing manufacturing complexity through process integration rather than requiring entirely new manufacturing approaches.
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 the sensitivity and dynamic range of image sensors, particularly in high intensity light conditions, by reducing unwanted light exposure to small photodiodes and maintaining the sensitivity of large photodiodes.
Implementation Method 1
An attenuation layer is extended above small photodiodes and partially over large photodiodes to block high angle light
Implementation Method 2
Image sensors with split pixel structures have photodiodes of different sizes
Data Source
AI summary
An image sensor includes a substrate material. The substrate material includes a plurality of photodiodes disposed therein. The plurality of photodiodes includes a plurality of small photodiodes (SPDs) and a plurality of large photodiodes (LPDs) larger than the SPDs. An array of color filters is disposed over the substrate material. A buffer layer is disposed between the substrate material and the array of color filters. A metal pattern is disposed between the color filters in the array of color filters, and between the array of color filters and the buffer layer. An attenuation layer is disposed between the substrate material and the array of color filters. The attenuation layer is above and aligned with the plurality of SPDs and a portion of each of the plurality of LPDs. An edge of the attenuation layer is over one of the plurality of LPDs.