Phase Difference Pixel Layout for Higher Autofocus Sensitivity
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Solution Overview
Problem
The existing solid-state imaging devices face challenges in achieving high autofocus accuracy due to weak light intensity incident on the photodiode, as light transmitted through the photoelectric conversion film is not effectively absorbed, leading to reduced sensitivity and efficiency in charge conversion to voltage.
Innovation Solution
The solid-state imaging device incorporates a phase difference pixel with a larger area of one electrode compared to the imaging pixel, and includes a light shielding film to limit incident light, enhancing sensitivity and autofocus accuracy by increasing the output difference between phase difference pixels at various incident angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light is transmitted through the photoelectric conversion film to reach the photodiode, then phase difference detection is enabled, but the light intensity becomes weak resulting in low autofocus accuracy
Solution Approach 1:
The patent applies local quality by making the lower electrode area in phase difference pixels larger than in ordinary imaging pixels. This localized change in electrode area specifically enhances light absorption capacity in phase difference pixels where light intensity is critical for autofocus accuracy, without affecting other pixels. The asymmetric electrode design creates different optical characteristics in different pixel types within the same image sensor.
Solution Approach 2:
The patent changes the physical parameter of electrode area to improve light absorption. By increasing the lower electrode area in phase difference pixels, the capacitance and light absorption capacity are enhanced, which directly addresses the weak light intensity problem. This parameter change transforms the optical characteristics of specific pixels to optimize phase difference detection performance.
2Measurement precision
If the lower electrode area is increased in phase difference pixels, then sensitivity and autofocus accuracy are improved, but the electrode capacitance increases reducing charge to voltage conversion efficiency
Solution Approach 1:
The patent segments the electrode area by type of pixel. Instead of using a uniform electrode design across all pixels, it divides the image sensor into ordinary imaging pixels and phase difference pixels, with each type having optimized electrode areas suited to their specific functions. This segmentation allows phase difference pixels to have larger electrodes for sensitivity while ordinary pixels maintain smaller electrodes for efficiency.
Solution Approach 2:
The patent applies local quality by making the lower electrode area in phase difference pixels larger than in ordinary imaging pixels. This localized change in electrode area specifically enhances light absorption capacity in phase difference pixels where light intensity is critical for autofocus accuracy, without affecting other pixels. The asymmetric electrode design creates different optical characteristics in different pixel types within the same image sensor.
3Loss of energy
If the lower electrode area is minimized in imaging pixels, then charge to voltage conversion efficiency is improved, but sensitivity output may be insufficient
Solution Approach 1:
The patent segments the electrode area by type of pixel. Instead of using a uniform electrode design across all pixels, it divides the image sensor into ordinary imaging pixels and phase difference pixels, with each type having optimized electrode areas suited to their specific functions. This segmentation allows phase difference pixels to have larger electrodes for sensitivity while ordinary pixels maintain smaller electrodes for efficiency.
Solution Approach 2:
The patent optimizes the electrode area parameter differently for different pixel types. In ordinary imaging pixels, the smaller electrode area reduces capacitance and improves charge to voltage conversion efficiency. In phase difference pixels, the larger electrode area enhances light absorption and sensitivity. This differential parameter optimization resolves the contradiction between efficiency and sensitivity by applying appropriate parameters to appropriate locations.
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 results in improved sensitivity and enhanced autofocus accuracy by increasing the sensitivity difference between phase difference pixels, particularly at large incident angles, thereby improving the overall imaging characteristics.
Implementation Method 1
an upper electrode and a lower electrode that sandwich a photoelectric conversion film and that is used for obtaining an imaging signal
Implementation Method 2
a light shielding film to limit incident light above the photoelectric conversion film of the phase difference pixel
Data Source
AI summary
Imaging devices and electronic apparatuses incorporating imaging devices are provided. An imaging device as disclosed can include a first pixel of a first pixel and a second pixel of a second pixel. The first and second pixels each have a first electrode, a portion of a photoelectric conversion film, and a portion of a second electrode, where the photoelectric conversion film is between the first electrode and the second electrode. The first electrode of the first pixel has a first area, while the first electrode of the second pixel has a second area that is smaller than the first area. The first pixel can include a light shielding film. Alternatively or in addition, the first pixel can be divided into first and second portions.