Image Sensor Post Processing Circuit for Dynamic Range Extension
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Solution Overview
Problem
Image sensors face challenges in accurately measuring light intensities across a wide dynamic range due to saturation limits and noise charges, which affect the correlation between digital outputs and incident light, leading to measurement errors and limited operational ranges.
Innovation Solution
A pixel cell with multiple quantization modes (FD ADC, PD ADC, and TTS) and a raw output conversion circuit that uses conversion parameters to refine digital outputs, compensating for discontinuities between different intensity ranges and reducing noise effects, allowing for extended dynamic range and improved linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single A/D conversion relationship is used, then the device complexity is low, but the measurement precision is limited due to saturation and noise effects
Solution Approach 1:
The patent divides the light intensity measurement into multiple segments or ranges. Different A/D conversion relationships are applied to different intensity ranges: a first conversion relationship for lower intensities and a second conversion relationship for higher intensities. This segmentation allows each conversion relationship to be optimized for its specific range, improving overall measurement precision without requiring a single complex conversion relationship to handle all ranges equally well.
Solution Approach 2:
The patent implements a dynamic selection mechanism that automatically switches between different A/D conversion relationships based on the detected light intensity level. The system dynamically determines which conversion relationship to apply by evaluating the current intensity range, enabling adaptive optimization of measurement accuracy across varying conditions without manual intervention or fixed conversion parameters.
2Adaptability or versatility
If multiple quantization operations are performed for different intensity ranges, then the dynamic range is extended, but the device complexity increases due to multiple conversion relationships
Solution Approach 1:
The measurement system is segmented into multiple operational modes, each handling a specific intensity range. The patent defines distinct quantization operations (first and second quantization operations) that are activated based on the detected intensity level. This segmentation enables the system to extend its dynamic range by treating different intensity ranges as separate measurement problems, each with optimized conversion characteristics.
Solution Approach 2:
The patent implements preliminary determination of the appropriate quantization operation before actual conversion. The system first evaluates which intensity range the current measurement falls into, then pre-selects the corresponding A/D conversion relationship. This preliminary action prevents the need for complex real-time adjustments during conversion, simplifying the overall device architecture while maintaining extended dynamic range capability.
3Manufacturing precision
If conversion parameters are used to compensate for discontinuities, then the linearity across intensity ranges is improved, but the ease of operation decreases due to calibration requirements
Solution Approach 1:
The patent employs specific conversion parameters (such as offset compensation parameters and scaling factors) that are applied to the digital outputs from different quantization operations. These parameters are designed to compensate for discontinuities and non-linearities at the boundaries between intensity ranges. By changing the mathematical parameters of the conversion relationships rather than the hardware architecture, the system achieves improved linearity while keeping the physical device structure relatively simple.
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 extends the dynamic range of light intensity measurement, reduces measurement errors, and ensures a uniform linear relationship across intensity ranges, enhancing the accuracy of light intensity determination for applications like SLAM and AR/VR systems.
Implementation Method 1
A typical image sensor includes a photodiode to sense incident light by converting photons into charge (e.g., electrons or holes)
Data Source
AI summary
Methods and systems for quantizing a physical quantity, such as light, are provided. In one example, an apparatus comprises an analog-to-digital (A/D) converter configured to generate raw digital outputs based on performing at least one of: (1) a first quantization operation to quantize a physical stimulus within a first intensity range based on a first A/D conversion relationship, or (2) a second quantization operation to quantize the physical stimulus within a second intensity range based on a second A/D conversion relationship; and a raw output conversion circuit configured generate a refined digital output based on a raw digital output obtained from the A/D converter and at least one predetermined conversion parameter. The at least one conversion parameter compensates for a discontinuity between the first A/D conversion relationship and the second A/D conversion relationship.