Solid-State Imaging Device Variable Capacitance Dynamic Range
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS image sensors face challenges in achieving a wide dynamic range while maintaining high sensitivity and a high signal-to-noise ratio (S/N ratio), particularly in capturing images across varying illuminance levels without degrading image quality.
Innovation Solution
The proposed solid-state imaging device incorporates an integrated array of pixels with a photodiode, transfer transistor, floating diffusion region, and storage capacitor element, where the storage capacitor element accumulates overflowing photoelectric charges during a predetermined accumulation period, allowing for high sensitivity in low illuminance and expanded dynamic range in high illuminance, using a method that includes noise cancellation and differential signal processing to maintain a high S/N ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a small capacitance floating diffusion region is used for high sensitivity in low illuminance, then sensitivity is improved, but dynamic range is limited and cannot cover high illuminance values
Solution Approach 1:
The patent applies dynamics by making the floating diffusion region capacitance variable rather than fixed. The capacitance can be dynamically adjusted between a first value (for low illuminance/high sensitivity) and a second value (for high illuminance/wide dynamic range) based on the actual lighting conditions, allowing the same pixel structure to adapt to different illuminance levels without requiring separate hardware configurations.
Solution Approach 2:
The patent changes the capacitance parameter of the floating diffusion region to resolve the contradiction. By adjusting the capacitance value according to illuminance conditions, the system achieves both high sensitivity (when capacitance is at first value for low illuminance) and wide dynamic range (when capacitance is at second value for high illuminance), eliminating the need to choose between conflicting performance requirements.
2Adaptability or versatility
If a large capacitance floating diffusion region is used for wide dynamic range in high illuminance, then dynamic range is improved, but sensitivity deteriorates in low illuminance
Solution Approach 1:
The system dynamically switches the floating diffusion region capacitance between a first value (smaller, for sensitivity) and a second value (larger, for dynamic range) based on illuminance detection. This dynamic adjustment allows the system to optimize for wide dynamic range when capturing high illuminance scenes while maintaining high sensitivity when capturing low illuminance scenes, resolving the trade-off between these two parameters.
Solution Approach 2:
The patent changes the capacitance parameter of the floating diffusion region based on operating conditions. When high illuminance is detected, the capacitance is set to a second value to expand dynamic range; when low illuminance is detected, the capacitance is set to a first value to maximize sensitivity. This parameter adaptation resolves the contradiction by allowing optimal performance in both regimes.
3Adaptability or versatility
If different accumulation times are used for low illuminance and high illuminance shootings, then dynamic range is widened, but image matching becomes difficult due to temporal differences
Solution Approach 1:
Instead of using different accumulation times for different illuminance levels, the patent dynamically adjusts the floating diffusion region capacitance while maintaining a uniform accumulation time for all pixels. This approach preserves temporal consistency across the image while achieving wide dynamic range through capacitance modulation, thereby resolving the contradiction between dynamic range expansion and image matching accuracy.
Solution Approach 2:
The patent changes the capacitance parameter of the floating diffusion region rather than changing the accumulation time parameter. This allows different effective dynamic ranges to be achieved for low and high illuminance conditions while keeping the accumulation time constant, thus maintaining temporal consistency and avoiding the image matching problems that arise from differential accumulation times.
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 solution enables the CMOS image sensor to achieve a wide dynamic range with high sensitivity and a high S/N ratio, effectively addressing the limitations of existing technologies by allowing simultaneous high-quality image capture in both low and high illuminance conditions without splitting accumulation time.
Implementation Method 1
a photodiode for receiving light and generating and accumulating photoelectric charges
Data Source
AI summary
A solid-state imaging device and an optical sensor, which can enhance a wide dynamic range while keeping a high sensitivity with a high S/N ratio, and a method of operating a solid-state imaging device for enhancing a wide dynamic range while keeping a high sensitivity with a high S/N ratio are disclosed. An array of integrated pixels has a structure wherein each pixel comprises a photodiode PD for receiving light and generating and accumulating photoelectric charges and a storage capacitor element CS coupled to the photodiode PD through a transfer transistor Tr1 for accumulating the photoelectric charges overflowing from the photodiode PD. The storage capacitor element CS is structured to accumulate the photoelectric charges overflowing from the photodiode PD in a storage-capacitor-element accumulation period TCS that is set to be a period at a predetermined ratio with respect to an accumulation period of the photodiode PD.