Image Sensor Feedback Unit for Wide Dynamic Range Control
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Solution Overview
Problem
Conventional image sensors face challenges in capturing images with a wide dynamic range, as they either overexpose subjects in high illuminance or underexpose them in low illuminance due to fixed sensitivity settings.
Innovation Solution
An image sensor design incorporating a photoelectric conversion unit, signal generation unit, and feedback unit, where the feedback unit adjusts the drive voltage based on the amount of photo-charges generated, allowing for dynamic sensitivity adjustment to handle varying light intensities, thereby implementing a wide dynamic range (WDR) function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the sensitivity of an image sensor is increased to capture low illuminance subjects, then low illuminance subjects can be captured with sufficient brightness, but high illuminance subjects become overexposed and indistinguishable
Solution Approach 1:
The patent implements a feedback mechanism that dynamically adjusts the drive voltage applied to the photoelectric conversion unit based on the amount of photocharges generated. When photocharge accumulation indicates high illuminance conditions, the feedback unit reduces the drive voltage magnitude to prevent saturation. Conversely, when photocharge accumulation indicates low illuminance conditions, the feedback unit increases the drive voltage magnitude to enhance sensitivity. This dynamic adjustment enables the image sensor to adapt to varying light conditions and capture both high and low illuminance subjects within the same scene without overexposure or underexposure.
2Adaptability or versatility
If the sensitivity of an image sensor is decreased to avoid overexposure in high illuminance, then high illuminance subjects can be captured without saturation, but low illuminance subjects become underexposed and indistinguishable
Solution Approach 1:
The patent employs a feedback control mechanism where the feedback unit continuously monitors the amount of photocharges accumulated in the photoelectric conversion unit and adjusts the drive voltage accordingly. The feedback unit generates a feedback signal proportional to the photocharge amount and uses this signal to modulate the drive voltage magnitude. This closed-loop control ensures that the photoelectric conversion unit operates within its linear response range regardless of incident light intensity, thereby maintaining both the dynamic range and the captured brightness across varying illuminance conditions.
3Device complexity
If a fixed sensitivity setting is used in the photoelectric conversion unit, then the device structure remains simple, but the image sensor cannot handle varying light intensities and loses adaptability
Solution Approach 1:
The patent changes the operational parameter (drive voltage magnitude) of the photoelectric conversion unit dynamically based on lighting conditions. The feedback unit adjusts the magnitude of the drive voltage applied to the photoelectric conversion unit according to the detected photocharge amount. By varying this key parameter, the system achieves adaptability to different light intensities without requiring fundamentally different hardware structures, thus maintaining relative simplicity while gaining versatility.
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 image sensor effectively captures images with both high and low illuminance without saturation, providing high-quality images across a wide range of light conditions by independently controlling the sensitivity of each pixel based on incident light intensity.
Implementation Method 1
the photoelectric conversion unit detects incident light to generate photo-charges based on a drive voltage
Data Source
AI summary
An image sensor includes a photoelectric conversion unit, a signal generation unit, and a feedback unit. The photoelectric conversion unit is formed above a substrate and detects incident light to generate photo-charges based on a drive voltage. The signal generation unit is formed on the substrate and generates an analog signal based on the photo-charges. The feedback unit generates the drive voltage based on an amount of the photo-charges generated from the photoelectric conversion unit. The image sensor may perform a wide dynamic range (WDR) function.