3D Stacked Image Sensor Resolving Phase Difference AF Resolution Trade-off
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Solution Overview
Problem
Conventional imaging surface phase difference AF structures face a trade-off where precise phase difference AF is difficult to achieve without reducing overall image resolution, as pixels used for forming images are also utilized for phase difference detection.
Innovation Solution
An image sensor with a 3D stack structure is employed, featuring a first substrate with a smaller photodiode for phase difference AF and a second substrate for image formation, where light is selectively blocked or guided using metal interconnections, blocking layers, or Talbot effect induction filters to maintain high resolution and enable phase difference AF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pixels are used for both image formation and phase difference detection, then the phase difference AF function can be realized without a separate sensor module, but overall image resolution is reduced
Solution Approach 1:
The sensor is divided into two separate substrates: a first substrate dedicated to phase difference detection and a second substrate dedicated to high-resolution image formation. This segmentation allows each substrate to be optimized for its specific function, eliminating the trade-off between phase difference AF capability and image resolution.
Solution Approach 2:
The solution transitions from a 2D planar sensor structure to a 3D stacked sensor structure with multiple substrates arranged in different spatial dimensions. This vertical stacking enables independent optimization of phase difference detection and image capture functions without compromising either performance.
2Measurement precision
If a separate phase difference AF sensor module is used, then precise phase difference AF can be achieved, but device complexity and size increase
Solution Approach 1:
The phase difference detection function and image capture function are merged into a single integrated sensor module with stacked substrates. This consolidation eliminates the need for separate sensor modules while maintaining precise phase difference AF capability, thereby reducing overall device complexity.
Solution Approach 2:
The stacked sensor structure achieves multi-functionality by enabling both phase difference detection and high-resolution image capture within a single sensor module. This universal design eliminates the need for additional separate modules, simplifying the overall device architecture.
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 approach allows for fast phase difference AF without resolution loss, enabling precise distance measurement and three-dimensional image capture while maintaining high image quality.
Implementation Method 1
a part of light incident into the first photodiode is blocked to realize a phase difference AF function
Implementation Method 2
a light waveguide is formed at an upper portion of a part at which light is incident into the first photodiode, so that light is more sensitively transferred to the first photodiode
Implementation Method 3
a Talbot effect induction filter is provided at an upper portion of the first photodiode
Data Source
AI summary
Disclosed is an image sensor with a 3D stack structure, in which pixels of a top plate are realized as image pixels and pixels of a bottom plate are realized as pixels for realizing a phase difference AF, so that the phase difference AF is realized without loss of resolution. In the image sensor with a 3D stack structure, a problem of the reduction of resolution, which is a disadvantage of an existing imaging surface phase difference AF device, is solved, so that a fast phase difference AF is realized while maintaining high resolution without a separate phase difference AF module.