Microlens Asymmetry for Phase Difference Detection Sensitivity
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Solution Overview
Problem
The existing solid-state imaging devices face challenges in enhancing the detection sensitivity of phase difference detection pixels while maintaining high sensitivity characteristics of imaging pixels, particularly in achieving accurate auto focus (AF) operations using the pupil-division phase difference detection method.
Innovation Solution
The implementation of a solid-state imaging device with a second microlens for phase difference detection pixels, featuring a unique configuration where the focal distance in the array direction coincides with that in the diagonal direction, and a light blocking film positioned to optimize the division of light flux from the exit pupil, enhancing the division ability of light in both directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the opening size for phase difference detection pixel is reduced to enhance detection sensitivity, then AF detection accuracy is improved, but light gathering capability deteriorates
Solution Approach 1:
The patent applies local quality by making the microlens corresponding to the phase difference detection pixel have different optical properties (smaller size, front defocusing) compared to microlenses for imaging pixels. This localized differentiation allows the phase difference detection pixel to have enhanced detection sensitivity through reduced opening size while the imaging pixels maintain their light gathering capability with larger openings.
2Measurement precision
If the microlens focus is set to front defocusing to divide light flux for AF function, then detection sensitivity is enhanced, but imaging quality may deteriorate
Solution Approach 1:
The patent segments the microlens array into two distinct types: microlenses for imaging pixels with standard focus characteristics, and a specialized microlens for the phase difference detection pixel with front defocusing. This segmentation allows each type to be optimized independently - the phase difference detection microlens achieves enhanced detection sensitivity through light flux division while imaging microlenses maintain optimal imaging quality.
Solution Approach 2:
The invention applies local quality by providing different focal characteristics to different locations in the microlens array. The microlens corresponding to the phase difference detection pixel is specifically designed with front defocusing to divide light flux into right and left portions for AF detection, while other microlenses maintain standard focus for high-quality imaging.
3Measurement precision
If a specialized microlens configuration is implemented for phase difference detection pixel, then AF detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent implements asymmetry by making the microlens for the phase difference detection pixel fundamentally different from standard imaging microlenses. The asymmetric design includes smaller size and front defocusing characteristics that enable light flux division for accurate AF detection. Despite this added complexity in the microlens configuration, the overall device structure remains relatively simple as it only requires modifying a single microlens within the existing pixel array.
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 significantly improves the detection sensitivity and accuracy of phase difference detection, allowing for more precise auto focus operations by ensuring the focal positions in both directions are near the light blocking film, thereby enhancing the division of light and improving AF detection accuracy.
Implementation Method 1
a second microlens corresponding to the phase difference detection pixel, the second microlens having a first bottom surface in the array direction and a second bottom surface in a direction diagonal to the array direction, the second bottom surface being closer to the upper surface of the photodiode than the first bottom surface
Data Source
AI summary
A solid-state imaging device comprises an imaging pixel located in a light receiving region, the imaging pixel being a component of a unit pixel that is one of a plurality of unit pixels arranged in an array direction. A phase difference detection pixel is located in the light receiving region and is a component of the unit pixel, and has a corresponding photodiode with an upper surface. A first microlens corresponds to the imaging pixel, and a second microlens corresponding to the phase difference detection pixel. The second microlens has a first bottom surface in the array direction and a second bottom surface in a direction diagonal to the array direction, the second bottom surface being closer to the upper surface of the photodiode than the first bottom surface.