Asymmetrical Microlens for Phase-Difference Focus Detection
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Solution Overview
Problem
Existing image pickup devices face challenges in improving both focus detection accuracy based on phase difference detection and image pickup performance, particularly in sensitivity to oblique incident light and reducing color mixing from adjacent pixel signals.
Innovation Solution
The use of asymmetrical microlenses in an image pickup device, where the vertex position of the microlens is off-center, allows for enhanced focus detection accuracy and sensitivity by optimizing the light collection and distribution across photoelectric conversion units, thereby improving both focus detection and image pickup performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If symmetrical microlenses are used in image pickup devices, then manufacturing is simpler, but focus detection accuracy and sensitivity to oblique incident light are insufficient
Solution Approach 1:
The patent applies asymmetry by designing microlenses with different curvature radii in the first and second directions (R1 ≠ R2). This asymmetrical design allows the microlens to effectively collect oblique incident light and improve focus detection accuracy by creating distinct focal points for different orientations, while still being manufacturable using standard photolithography processes with appropriately designed mask patterns.
2Measurement precision
If microlens focal points are positioned closer to the microlens for focus detection pixels, then focus detection accuracy improves, but image pickup performance deteriorates
Solution Approach 1:
The patent applies local quality by making the microlens curvature radii different in different directions (R1 in the first direction, R2 in the second direction). This creates directionally-dependent focal characteristics where the microlens can optimize light collection for oblique incident light in specific directions, thereby improving focus detection accuracy without significantly compromising overall image pickup performance.
3Measurement precision
If microlens positions are varied according to image height, then focus detection accuracy improves, but device complexity increases
Solution Approach 1:
The patent applies asymmetry by designing microlenses with different curvature radii in the first and second directions (R1 ≠ R2). This asymmetrical design allows the microlens to effectively collect oblique incident light and improve focus detection accuracy by creating distinct focal points for different orientations, while still being manufacturable using standard photolithography processes with appropriately designed mask patterns.
4Measurement precision
If asymmetrical microlenses with off-center vertices are used, then sensitivity to oblique incident light and focus detection accuracy improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies asymmetry by designing microlenses with different curvature radii in the first and second directions (R1 ≠ R2). This asymmetrical design allows the microlens to effectively collect oblique incident light and improve focus detection accuracy by creating distinct focal points for different orientations, while still being manufacturable using standard photolithography processes with appropriately designed mask patterns.
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 asymmetrical microlens design enables better focus detection accuracy and increased sensitivity, effectively addressing the limitations of existing technologies by allowing for flexible focus positioning and improved light collection, especially in oblique incidence scenarios.
Implementation Method 1
a plurality of microlenses arranged to correspond to respective photoelectric conversion units of the respective image pickup pixels; and a plurality of microlenses arranged to correspond to respective photoelectric conversion units of the respective focus detection pixels
Implementation Method 2
the focal point of a microlens for a focus detection pixel is closer to the microlens than the focal point of a microlens for an image pickup pixel
Data Source
AI summary
An image pickup device includes a pixel region having a plurality of pixels that are two-dimensionally arranged, the plurality of pixels including a plurality of image pickup pixels and a plurality of focus detection pixels capable of phase difference detection; a plurality of microlenses arranged to correspond to respective photoelectric conversion units of respective image pickup pixels; and a plurality of microlenses arranged to correspond to respective photoelectric conversion units of the respective focus detection pixels. When at least one of the plurality of microlenses is orthogonally projected onto the corresponding photoelectric conversion unit, a vertex position of the at least one microlens is off a center position of the at least one microlens.