HDR Image Sensor Readout Circuitry Power Control
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Solution Overview
Problem
High dynamic range imaging techniques for image sensors often consume excessive power and introduce sensor noise due to increased dark current, particularly in multiple exposure imaging methods.
Innovation Solution
Implementing power control circuitry that selectively disables readout circuitry for exposures determined to not produce useful data, based on initial image data comparisons to thresholds, to conserve power and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple exposure imaging is performed to capture high dynamic range images, then the dynamic range capability is improved, but power consumption increases and sensor noise increases due to increased dark current
Solution Approach 1:
The patent applies preliminary action by performing a first exposure and evaluating its image data before committing to subsequent exposures. The control circuitry determines whether the first exposure data is above a saturation threshold, and only if it is below the threshold does the system proceed with additional exposures. This preliminary evaluation prevents unnecessary multiple exposures that would waste power.
Solution Approach 2:
The patent implements partial action by selectively performing only the necessary number of exposures based on scene conditions. Instead of always performing all planned exposures, the system performs only one exposure when the scene is sufficiently bright (data above threshold), and performs multiple exposures only when needed (data below threshold). This partial execution reduces power consumption while maintaining HDR capability when required.
2Adaptability or versatility
If multiple exposure imaging is performed to capture high dynamic range images, then the dynamic range capability is improved, but sensor noise increases due to increased dark current
Solution Approach 1:
The control circuitry performs preliminary evaluation of the first exposure image data against a saturation threshold before initiating subsequent exposures. This preliminary check prevents unnecessary multiple exposures that would accumulate dark current and increase sensor noise, while still maintaining the capability to perform multiple exposures when the scene brightness requires it for proper HDR capture.
3Reliability
If readout circuitry is continuously enabled during multiple exposures, then complete image data is captured, but power consumption increases
Solution Approach 1:
The system performs preliminary capture and evaluation of the first exposure image data before determining whether to enable readout circuitry for subsequent exposures. The control circuitry compares the first exposure data to a saturation threshold and only enables additional readout operations when the data indicates underexposed conditions, thereby avoiding unnecessary power consumption from continuous readout while ensuring complete data capture when needed.
Solution Approach 2:
The patent applies partial action by enabling readout circuitry for only the necessary exposures rather than continuously. The system performs full readout for the first exposure, then selectively enables or disables readout for subsequent exposures based on the evaluated brightness conditions. This partial readout strategy reduces power consumption while maintaining reliability by ensuring all necessary exposure data is captured and combined.
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 reduces power consumption and minimizes sensor noise by disabling unnecessary readout circuitry during exposures that yield indistinguishable data from noise, while maintaining image quality by enabling circuitry for exposures with useful data.
Implementation Method 1
Each image pixel in the array includes a photodiode that is coupled to a floating diffusion region via a transfer gate
Data Source
AI summary
Image sensors may have high dynamic range (HDR) functionality. To implement the high dynamic range functionality, the image sensor may use multiple exposure imaging. In multiple exposure imaging, multiple images are captured with an image sensor at different exposure times and are later combined into a single high dynamic range image. Image data from one or more exposures in a multi-exposure imaging scheme may be used to determine that subsequent exposures will not produce useful information. To conserve power in the image sensor, certain readout circuitry such as analog-to-digital converter circuitry and column memory may be disabled during readout of the exposures that are determined to not produce useful information.