CMOS HDR Sensor Readout Using Multiple Integration Times
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image sensor readout techniques struggle to achieve a high dynamic range without compromising frame rate, power consumption, or increasing cost, often sacrificing either bright or dark area representation in images.
Innovation Solution
The method involves reading pixel reset and signal voltages corresponding to multiple integration times to determine saturation conditions, selecting non-saturated signals, and processing them to produce a digitized output that maintains image accuracy across varying light intensities, using a CMOS imager with sample-and-hold circuits and pre-processing modules to normalize pixel signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the integration time is increased to capture more light, then the dynamic range is improved, but the photosensor saturates and loses accuracy in bright areas
Solution Approach 1:
The patent divides the image capture process into multiple exposures with different integration times. The image sensor performs a first exposure with a first integration time and a second exposure with a second integration time longer than the first. This segmentation allows different regions of the image (bright and dark areas) to be captured at appropriate exposure levels, preventing saturation in bright areas while maintaining detail in dark areas.
Solution Approach 2:
The patent dynamically adjusts the integration time based on the scene requirements. By using multiple integration times (first integration time and second integration time which is longer), the system can adapt to varying light conditions across different regions of the image, optimizing both highlight and shadow detail capture without fixed integration time limitations.
2Measurement precision
If the integration time is decreased to prevent saturation, then accuracy in bright areas is maintained, but detail in dark areas is lost
Solution Approach 1:
The patent segments the capture process into multiple exposures with different integration times. The first exposure uses a shorter integration time to accurately capture bright areas without saturation, while the second exposure uses a longer integration time to capture detail in dark areas. This segmentation resolves the trade-off by capturing both regions at their optimal exposure levels.
Solution Approach 2:
The system dynamically selects different integration times for different regions of the image. By implementing multiple exposures with varying integration times (first integration time for highlights, second integration time for shadows), the system adapts to local lighting conditions, preventing information loss in dark areas while maintaining accuracy in bright areas.
3Illumination intensity
If conventional readout techniques are used to compensate for saturation, then dynamic range is improved, but frame rate decreases and power consumption increases
Solution Approach 1:
The patent merges multiple exposures with different integration times into a single high dynamic range image. By combining the first exposure (short integration time) and second exposure (long integration time) data, the system achieves extended dynamic range while maintaining a single frame rate output. This merging approach avoids the need for multiple separate readout operations that would reduce frame rate.
Solution Approach 2:
The image sensor performs multiple functions within a single capture sequence: it captures both short and long integration time exposures, handles both bright and dark area optimization, and produces a unified high dynamic range output. This multi-functionality allows the system to achieve improved dynamic range without requiring separate processing channels that would increase power consumption and reduce frame rate.
4Illumination intensity
If conventional readout techniques are used to compensate for saturation, then dynamic range is improved, but power consumption and die area increase
Solution Approach 1:
The patent combines multiple exposure data within the existing sensor readout architecture. By merging the first and second exposure information during the normal readout process, the system achieves high dynamic range without adding separate power-intensive processing channels. The combined approach utilizes existing sensor resources efficiently, avoiding additional power consumption associated with conventional multi-channel HDR techniques.
Solution Approach 2:
The image sensor is designed to perform multiple exposure capture and processing functions within its existing operational framework. This multi-functionality allows the sensor to achieve improved dynamic range without requiring additional dedicated hardware components that would increase die area and power consumption. The universal approach leverages existing sensor capabilities for both standard and HDR operation.
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 approach enables a higher dynamic range for captured images while reducing frame rate and power consumption, maintaining image quality without the need for additional components, thus lowering costs and enabling efficient image processing.
Implementation Method 1
In an imager, photosensors capture the photons and provide respective signals that represent a captured image. Each photosensor may include a photodiode, which is initially reset to a reference voltage, and which, after reset, integrates a charge over a specified time period proportional to the intensity of light on the photosensor.
Data Source
AI summary
Imagers reproduce an image by converting photons to a signal that is representative of the image. A sensor readout module reads reset and signal voltages corresponding to a plurality of integration times for each of a plurality of pixels. The sensor readout module is capable of determining whether the differences between reset and signal voltages corresponding to respective integration times indicate a saturation condition of the pixel. Accordingly, the sensor readout module may provide an output signal based on reset and signal voltages corresponding to an integration time that is less than an integration time for reset and signal voltages that indicate the saturation condition. A normalization module may normalize the output signal to correspond with a linear response curve.