Microlens Curvature Optimization for Image Sensor Focus and Crosstalk
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Solution Overview
Problem
The curvature of a microlens for improving pupil division ability to enhance focus detection performance and the curvature for suppressing crosstalk between pixels to improve imaging performance do not always match, leading to suboptimal performance in both focus detection and imaging.
Innovation Solution
An image sensor with pixels that include a microlens optical system with a principal curved surface where the first curvature at a shorter distance from the optical axis is larger than the second curvature at a farther distance, optimizing both pupil division and crosstalk suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the curvature of the microlens is increased to improve pupil division ability, then focus detection performance is improved, but crosstalk between pixels increases and imaging performance deteriorates
Solution Approach 1:
The microlens optical system is designed with non-uniform curvature distribution: the first curvature at the first distance from the optical axis is larger than the second curvature at the second distance. This local variation in curvature allows different regions of the microlens to perform different functions - the higher curvature region improves pupil division for focus detection, while the lower curvature region suppresses crosstalk between pixels
Solution Approach 2:
The invention changes the curvature parameter of the microlens optical system from a uniform value to a spatially varying value. By making the curvature depend on the distance from the optical axis, the system optimizes both focus detection performance and imaging quality simultaneously, resolving the contradiction between these two requirements
2Object-generated harmful factors
If the curvature of the microlens is decreased to suppress crosstalk between pixels, then imaging performance is improved, but pupil division ability deteriorates and focus detection performance decreases
Solution Approach 1:
Different regions of the microlens optical system are assigned different curvature values to perform different functions. The region at the first distance from the optical axis has larger curvature for focus detection, while the region at the second distance has smaller curvature for suppressing crosstalk
Solution Approach 2:
The microlens optical system is effectively segmented into different functional zones based on distance from the optical axis. Each zone has optimized curvature characteristics for its specific function, allowing the system to achieve both good focus detection and imaging performance
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 suppresses crosstalk between pixels while maintaining high focus detection performance, achieving good imaging performance simultaneously.
Implementation Method 1
a microlens optical system provided on a light incident side with respect to the photoelectric conversion unit
Data Source
AI summary
In an image sensor having a plurality of pixels including focus detection pixels that outputs signals from which a pair of focus detection signals having parallax can be obtained based on light flux passing through different pupil regions of an imaging optical system, each pixel comprises: at least one photoelectric conversion unit; and a microlens optical system provided on a side on which light is incident with respect to the photoelectric conversion unit, wherein a shape of a principal curved surface of the microlens optical system is such that a first curvature of the microlens optical system at a first distance from an optical axis of the microlens optical system is larger than a second curvature of the microlens optical system at a second distance which is farther from the optical axis of the microlens optical system than the first distance.