CMOS Image Sensor Boosted Voltage Charge Transfer
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Solution Overview
Problem
Conventional CMOS image sensors face challenges in transferring all accumulated charges from the photodiode to the charge detector, leading to afterimages and reduced conversion gain due to incomplete charge transfer, which degrades image sensor performance.
Innovation Solution
A CMOS image sensor with a charge transfer unit that utilizes a boosted voltage level higher than the external power voltage, selectively applied through a variable booster, to enhance the charge transfer process, ensuring complete transfer of charges and reducing afterimage effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If image sensors are fabricated at reduced sizes, then miniaturization is achieved, but charge transfer completeness deteriorates
Solution Approach 1:
The patent applies dynamics by making the charge transfer voltage variable rather than fixed. The voltage is dynamically adjusted based on the transfer efficiency detection results, allowing the system to adapt to the reduced sensor dimensions and maintain complete charge transfer despite miniaturization.
Solution Approach 2:
The patent changes the voltage parameter to optimize charge transfer. By varying the charge transfer voltage and detecting transfer efficiency, the system identifies the optimal voltage level that ensures complete charge transfer in miniaturized sensors, resolving the contradiction between small size and reliable charge transfer.
2Reliability
If charges are not completely transferred from photodiode to charge detector, then afterimages occur, but conversion gain decreases
Solution Approach 1:
The patent implements feedback by detecting charge transfer efficiency and using this information to adjust the charge transfer voltage. This closed-loop control ensures complete charge transfer (preventing afterimages) while optimizing the voltage level to maintain high conversion gain, resolving the contradiction between transfer completeness and gain preservation.
3Loss of energy
If conventional voltage levels are used for charge transfer, then power consumption is controlled, but charge transfer efficiency deteriorates
Solution Approach 1:
The patent changes the voltage parameter to optimize charge transfer efficiency. By detecting transfer efficiency and adjusting the voltage accordingly, the system achieves complete charge transfer while managing power consumption through intelligent voltage control rather than simply increasing voltage indefinitely.
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 boosted voltage level improves charge transfer efficiency, reducing afterimage effects and increasing conversion gain, thereby enhancing the overall performance of the image sensor.
Implementation Method 1
If a light is incident on the photodiode, the photodiode may absorb photo energy and may accumulate charges corresponding to a quantity or intensity of the incident light
Data Source
AI summary
An image sensor and method thereof. In an example, the image sensor, may include a pixel array including a plurality of unit pixels, each of the plurality of unit pixels having a charge transfer unit for transferring charges accumulated in an optoelectronic converter to a charge detector via a charge transfer driving signal. The example image sensor may further include a row driving unit generating a boosted voltage, the boosted voltage set to a boosted voltage level higher than a power voltage level, the boosted voltage selectively boosted in response to a boosting voltage variable control signal. The row driving unit may selectively apply the charge transfer driving signal to the pixel array. In another example, the method may include selectively adjusting a voltage level of a charge transfer driving voltage and transferring the charge transfer driving voltage to a charge transfer unit for controlling an operation of the charge transfer unit.