Image Sensor Asymmetric Light Shielding for Shading Reduction
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Solution Overview
Problem
In image sensors with a silicon layer photodiode, the condensing point of the on-chip lens decreases in radius of curvature, leading to oblique incidence characteristics deterioration and sensitivity unevenness, known as shading, as the image height increases.
Innovation Solution
An image sensor design where photoelectric conversion layers are stacked in two or more layers, with a light-shielding layer having asymmetric openings between the layers to direct light from a first photoelectric conversion layer closer to the optical lens to a second layer further away, allowing for improved light reception and phase difference detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the condensing point of the on-chip lens is set in the photodiode of the silicon layer, then the aperture ratio is high, but the radius of curvature of the on-chip lens decreases and oblique incidence characteristics deteriorate
Solution Approach 1:
The patent transitions from a single-layer photoelectric conversion structure to a stacked multi-layer structure. By stacking photoelectric conversion layers at different depths, the system can receive light at various incidence angles more effectively while maintaining high aperture ratio, thus resolving the contradiction between aperture size and oblique incidence performance
Solution Approach 2:
Different photoelectric conversion layers are positioned at different depths to handle different light incidence characteristics. The asymmetric opening design further localizes light reception properties to specific spatial regions, allowing each layer to optimize for its specific function and position
2Quantity of substance
If the radius of curvature of the on-chip lens is decreased to increase aperture ratio, then more light can be received, but sensitivity unevenness called shading occurs as image height increases
Solution Approach 1:
By adding the depth dimension through stacked layers, the system can distribute light reception across multiple focal planes. This multi-layer arrangement compensates for the shading effect that occurs in single-layer systems with small radius of curvature lenses, as each layer can be optimized for its specific depth position
Solution Approach 2:
The photoelectric conversion function is segmented across multiple layers rather than concentrated in a single layer. This segmentation allows each layer to handle specific portions of the light field, reducing the shading unevenness that would affect a monolithic structure
3Measurement precision
If asymmetric openings are introduced in the light-shielding layer, then phase difference detection performance is improved, but device complexity increases
Solution Approach 1:
Asymmetric openings are deliberately introduced in the light-shielding layer to create phase differences between light paths. This asymmetry is essential for achieving accurate phase difference detection, as it creates the necessary optical path length differences that enable focus and depth information to be captured
Solution Approach 2:
The stacked photoelectric conversion layers serve multiple functions simultaneously: they perform standard image capture while also enabling phase difference detection through the asymmetric opening configuration. This multi-functionality reduces the need for separate dedicated phase detection hardware
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 design enhances image quality by reducing shading and improving phase difference autofocus performance by increasing the radius of curvature of the on-chip lens and enhancing light reception across varying image heights.
Implementation Method 1
a light-shielding layer configured to shield light transmitted through the first photoelectric conversion layer, between the first photoelectric conversion layer and the second photoelectric conversion layer
Implementation Method 2
photoelectric conversion layers including photoelectric conversion units separated in units of pixels are stacked in two or more layers
Data Source
AI summary
The present technology relates to an image sensor and an electronic device capable of performing imaging in which mixed color is reduced. Photoelectric conversion layers including photoelectric conversion units separated in units of pixels are stacked in two or more layers, the image sensor is configured to include a state in which light incident on one pixel in a first photoelectric conversion layer closer to an optical lens is received by the photoelectric conversion unit in a second photoelectric conversion layer distant from the optical lens, the image sensor includes a light-shielding layer configured to shield light transmitted through the first photoelectric conversion layer, between the first photoelectric conversion layer and the second photoelectric conversion layer, the light-shielding layer has an opening to transmit the light from the first photoelectric conversion layer to the second photoelectric conversion layer, and the openings are made to be asymmetric with respect to the pixel in the first photoelectric conversion layer. The present technology can be applied to an image sensor with a multi-layered structure.