Hybrid Pixel Image Sensor with Non-Volatile Memory for Dynamic Range
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Solution Overview
Problem
CMOS image sensors suffer from low dynamic range, affecting image quality under varying light conditions, and existing solutions to enhance dynamic range increase silicon area, power dissipation, and complexity, making them cost-ineffective.
Innovation Solution
Incorporating a non-volatile memory (NVM) component in hybrid pixels, which calibrates resistance states based on light intensity to modulate capacitance and compress output signals, thereby enhancing sensitivity and dynamic range without increasing silicon area or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing solutions are used to enhance dynamic range, then dynamic range is improved, but silicon area, power dissipation, and complexity increase
Solution Approach 1:
The patent merges the pixel circuit and non-volatile memory (NVM) device into a hybrid pixel structure, where the NVM device is integrated within the pixel circuit. This combination allows the NVM device to store charge directly at the pixel level, enabling dynamic range enhancement without requiring separate memory structures or additional processing circuits, thus improving dynamic range while controlling complexity
Solution Approach 2:
The NVM device serves multiple functions: it acts as both a storage element for accumulated charge and a means to extend the dynamic range of the pixel. By integrating these functions into a single component, the patent avoids adding separate dedicated structures for each function, thereby improving dynamic range performance without proportionally increasing device complexity
2Reliability
If existing solutions are used to enhance dynamic range, then dynamic range is improved, but silicon area increases
Solution Approach 1:
The NVM device is nested within the pixel circuit structure, with the NVM device positioned to share physical space with existing pixel components. This nesting approach allows the dynamic range enhancement functionality to be embedded within the existing pixel footprint, improving dynamic range without requiring additional silicon area beyond what is already allocated for the pixel circuit
3Reliability
If existing solutions are used to enhance dynamic range, then dynamic range is improved, but power dissipation increases
Solution Approach 1:
The NVM device performs preliminary charge storage during the exposure period, accumulating charge in its high-resistance state. This preliminary action allows the pixel to handle a wider range of light intensities without requiring additional power-consuming processing steps later, as the charge is already stored and ready for readout, thus improving dynamic range while minimizing additional power dissipation
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 solution achieves higher dynamic range for image sensors, improving image quality under low and bright light conditions while maintaining cost-effectiveness by integrating the NVM device without significant silicon area penalties.
Implementation Method 1
Each hybrid pixel includes a light detecting element, such as a photodiode, to generate photo-electrons
Implementation Method 2
a charge to voltage conversion unit to provide an output pixel signal corresponding to the generated photo-electrons
Implementation Method 3
The non-volatile memory component may be calibrated to a resistance state, such that the output pixel signal modulates the resistance state of the non-volatile memory component
Data Source
AI summary
Examples of image sensors are described herein. In an example, an image sensor may comprise an array of hybrid pixels, where each hybrid pixel includes light sensing unit and a non-volatile memory component coupled to the light sensing unit. The light sensing unit comprises a light detecting element and a charge to voltage conversion unit. The charge to voltage conversion unit is to provide an output pixel signal (VPD), based on photo-electrons generated by the light detecting element. Further, the non-volatile component when calibrated to an initial resistance state is to compress the output pixel signal (VPD) during exposure.