PDAF Pixel Shielding Grid Layout for Cross-Talk Reduction
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Solution Overview
Problem
Existing image sensors with phase detection autofocus (PDAF) pixels face issues of increased sensitivity due to microlenses with smaller radii of curvature, leading to undesired cross-talk between sensing pixels, as light with large angles of incidence is not adequately blocked, causing uneven light reception.
Innovation Solution
The image sensor incorporates a light-shielding grid surrounding PDAF pixels with wider first portions and light-absorbing grids around sensing pixels, designed to block light with large angles of incidence and reduce cross-talk, enhancing sensitivity and uniformity of light reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microlens with a smaller radius of curvature is disposed on the PDAF pixel, then the sensitivity of the PDAF pixel is increased, but the cross-talk between sensing pixels near the PDAF pixel increases
Solution Approach 1:
The patent introduces a light-shielding grid structure that divides and segments the light paths around the PDAF pixel. The grid includes multiple light-shielding portions positioned between the PDAF pixel and adjacent sensing pixels, effectively segmenting the optical paths to prevent stray light from causing cross-talk while preserving the benefits of the smaller radius of curvature microlens for enhanced sensitivity.
Solution Approach 2:
The light-shielding grid acts as an intermediary element between the PDAF pixel and the surrounding sensing pixels. This intermediate structure selectively blocks harmful stray light paths while allowing useful light to reach the PDAF pixel, thus mediating the conflict between sensitivity enhancement and cross-talk reduction.
2Quantity of substance
If the microlens occupies less space on the PDAF pixel, then more light with large angle of incidence can enter, but this causes uneven light reception between sensing pixels
Solution Approach 1:
The light-shielding grid employs local quality by positioning specific light-shielding portions at strategic locations around the PDAF pixel. The grid structure has varying transparency and shielding characteristics in different regions, allowing it to selectively block light paths that would cause uneven reception while permitting beneficial light to reach the sensing pixels uniformly.
Solution Approach 2:
The light-shielding grid performs preliminary anti-action by preemptively blocking stray light with large angles of incidence before these light rays can cause uneven reception in the sensing pixels. The grid is positioned and configured to intercept harmful light paths in advance, preventing the uniformity issue from occurring.
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 solution effectively increases PDAF pixel sensitivity and reduces detection cross-talk between sensing pixels, ensuring consistent light reception and improved autofocus performance.
Implementation Method 1
The light-shielding grid surrounds the first color filter layer, in which the light-shielding grid includes a first portion and a second portion from a top view, the first portion is closer to a center of the substrate than the second portion
Implementation Method 2
The PDAF pixel includes four photodiodes and a first color filter layer on the four photodiodes. The sensing pixels are on the substrate and surround the PDAF pixel, in which each of the sensing pixels includes a single photodiode
Data Source
AI summary
The present disclosure provides an image sensor including a unit. The unit includes a phase detection auto focus (PDAF) pixel, sensing pixels, and a light-shielding grid. The PDAF pixel is on a substrate, in which the PDAF pixel includes four photodiodes and a first color filter layer on the four photodiodes. The sensing pixels are on the substrate and surround the PDAF pixel, in which each of the sensing pixels includes a single photodiode and a second color filter layer on the single photodiode. The light-shielding grid surrounds the first color filter layer, in which the light-shielding grid includes a first portion and a second portion from a top view, the first portion is closer to a center of the substrate than the second portion, and a width of the first portion is larger than a width of the second portion.