Asymmetric Light Guide for Image Sensor Cross Talk Reduction
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Solution Overview
Problem
Conventional image sensors with light guides suffer from cross talk and signal loss due to scattered or absorbed light, making it difficult to perform focus detection using the pupil division phase difference method, and achieving high surface accuracy in the boundary surface is complex.
Innovation Solution
An image sensor with a light guide configuration where the maximum width of the cross section parallel to the image sensing surface is greater than the orthogonal direction, reducing cross talk by optimizing the shape of the light guide to improve light guidance and precision in focus detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a light guide is provided between the lens and photoelectric conversion portion, then light guidance is improved, but cross talk and signal loss occur due to scattered or absorbed light at boundary surfaces
Solution Approach 1:
The patent applies asymmetry by configuring the light guide with a rectangular cross-section where the dimension in the light incident direction (width) is larger than the dimension in the orthogonal direction (thickness). This asymmetric geometry optimizes light guidance while minimizing cross talk between adjacent pixels and reducing signal loss at boundary surfaces, directly resolving the technical contradiction between improving light guidance and reducing cross talk.
2Reliability
If a gap is provided to reduce cross talk, then cross talk is reduced, but light reception efficiency degrades due to scattered or absorbed light
Solution Approach 1:
The asymmetric light guide configuration (width > thickness) eliminates the need for additional gap structures. The optimized rectangular cross-section provides sufficient optical isolation between adjacent pixels while maintaining efficient light guidance, thereby reducing cross talk without degrading light reception efficiency.
Solution Approach 2:
The patent changes the geometric parameters of the light guide by setting the width (in light incident direction) larger than the thickness (in orthogonal direction). This parameter optimization achieves the dual goal of reducing cross talk through improved optical isolation while maintaining high light reception efficiency through effective light guidance.
3Reliability
If the maximum width of the light guide cross section in the arrangement direction is greater than in the orthogonal direction, then cross talk is reduced and light guidance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The asymmetric rectangular cross-section (width > thickness) provides superior optical isolation and light guidance performance compared to symmetric configurations. While this asymmetric geometry does impose manufacturing precision requirements, the performance benefits in cross talk reduction and light guidance efficiency make it the optimal choice for achieving reliable focus detection.
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 effectively reduces cross talk and signal loss, enabling precise focus detection and improved light reception efficiency by guiding light effectively between microlenses and photoelectric conversion portions.
Implementation Method 1
a light guide that guides light incident from a microlens to a plurality of photoelectric conversion portions
Data Source
AI summary
An image sensor comprising: a plurality of pixels that are each provided with a plurality of photoelectric conversion portions and a microlens, and that are configured to read out signals that have been subjected to pupil division, the plurality of pixels each being provided with a light guide that is located between the microlens and the plurality of photoelectric conversion portions, wherein a maximum width of a shape of a cross section, the cross section being parallel with an image sensing surface of the image sensor, of the light guide in an arrangement direction in which the plurality of photoelectric conversion portions that form a pair are arranged is greater than a maximum width of the shape of the cross section in an direction that is orthogonal to the arrangement direction.