Dual-Photodiode Image Sensor with Rotated Inner Grid Autofocus
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image sensors with dual photodiodes lack the capability to detect autofocus information in both horizontal and vertical directions due to incomplete light intensity variation detection, limiting their autofocus sensitivity.
Innovation Solution
Incorporating a rotated inner grid within the color filter of the image sensor, which splits incident light in both horizontal and vertical directions, allowing for the detection of light intensity variations and enhancing autofocus sensitivity by providing both horizontal and vertical autofocus information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional dual photodiode structure is used, then device simplicity is maintained, but autofocus sensitivity is limited due to incomplete autofocus information
Solution Approach 1:
The grid structure is divided into two distinct components: an outer grid and an inner grid. The outer grid provides basic light separation, while the inner grid with rotated spacers enhances autofocus information collection. This segmentation allows the system to improve measurement precision without overwhelming complexity, as each grid layer has a specific functional role.
Solution Approach 2:
The inner grid introduces a rotational dimension by positioning spacers at angles (e.g., 45 degrees) relative to the outer grid's vertical orientation. This angular rotation adds a new dimensional aspect to light detection, enabling the collection of complete autofocus information in both vertical and horizontal directions, thereby improving autofocus sensitivity.
2Loss of information
If inner grid with rotated spacers is added, then complete autofocus information is obtained, but manufacturing complexity increases
Solution Approach 1:
The inner grid is nested within the structure defined by the outer grid. The spacers of the inner grid are positioned within the spaces created by the outer grid's vertical spacers. This nested arrangement allows both grids to function together while sharing some structural support, reducing the overall manufacturing complexity compared to implementing two completely independent grid systems.
Solution Approach 2:
The grid structure combines different material properties: the outer grid uses vertically oriented spacers for basic light separation, while the inner grid uses rotated spacers (at angles such as 45 degrees) for enhanced autofocus information. This composite structural approach integrates multiple functional characteristics into a single system, achieving complete autofocus information while managing fabrication complexity through material and structural integration.
3Measurement precision
If inner grid is disposed in color filter, then light intensity detection in both directions is enhanced, but color filter complexity increases
Solution Approach 1:
The color filter structure serves multiple functions: it provides color filtering for the photodiodes and simultaneously houses the inner grid with rotated spacers for enhanced autofocus detection. By integrating the inner grid within the color filter's spacer structure, the system achieves multi-functionality, improving light intensity detection accuracy while avoiding the need for separate additional components.
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
The rotated inner grid improves autofocus sensitivity by enabling the detection of light intensity variations in both directions, thereby enhancing the overall autofocus capability of the image sensor.
Implementation Method 1
photoelectric transducers such as photodiodes for converting light into electric charges
Implementation Method 2
a microlens disposed over the color filter
Data Source
AI summary
An image sensor includes a first sensing unit. The first sensing unit includes a pair of photodiodes formed in a substrate and spaced by a deep trench isolation structure, an outer grid over the pair of photodiodes, a color filter filled in the outer grid, and an inner grid disposed in the color filter. The color filter overlaps the pair of photodiodes. The inner grid includes a first spacer, wherein the first spacer is rotated relative to the deep trench isolation structure.