Pixel Array With Dark Pixel Sensors for Current Calibration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dark current in CMOS image sensors causes noise and defects in captured images and video due to energy sources other than incident light, leading to inaccurate photocurrent measurements.
Innovation Solution
A pixel array with both visible light and dark pixel sensors is implemented, where dark pixel sensors generate individual dark current measurements to calibrate visible light pixel sensors, improving accuracy by subtracting dark current from photocurrent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dark pixel sensors are added to the pixel array for dark current calibration, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The pixel array is segmented into multiple pixel types including visible light pixel sensors, dark pixel sensors, and near-infrared pixel sensors. Each segment serves a specific function: visible light sensors capture color information, dark sensors measure dark current for calibration, and NIR sensors capture infrared information. This segmentation allows dedicated dark current measurement without compromising the main imaging function.
Solution Approach 2:
The dark pixel sensors serve multiple purposes: they provide dark current calibration for visible light pixel sensors, enable accurate black level correction across different temperature conditions, and contribute to overall image quality enhancement. This multi-functionality justifies the additional device complexity by providing comprehensive calibration capabilities.
2Measurement precision
If individual dark current measurements are performed for each visible light pixel sensor, then measurement precision is improved, but loss of time increases
Solution Approach 1:
Dark current measurements are performed in advance during manufacturing or initialization phases, and the measured values are stored in memory for later use. This preliminary action eliminates the need for real-time dark current measurement during normal operation, thus avoiding time loss while maintaining high measurement precision through individual calibration.
3Reliability
If dark pixel sensors are integrated into the pixel array, then reliability is improved, but area of stationary object increases
Solution Approach 1:
Dark pixel sensors are strategically positioned at specific locations within the pixel array where they can effectively measure dark current for surrounding visible light pixel sensors. This localized placement ensures that each dark sensor serves a specific region, maintaining reliability through accurate local calibration without requiring uniform distribution across the entire array.
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 more accurate dark current calibration of visible light pixel sensors, reducing noise and enhancing image quality by accounting for individual dark current variations.
Implementation Method 1
Complementary metal oxide semiconductor (CMOS) image sensors utilize light-sensitive CMOS circuitry to convert light energy into electrical energy. The light-sensitive CMOS circuitry may include a photodiode formed in a silicon substrate. As the photodiode is exposed to light, an electrical charge is induced in the photodiode (referred to as a photocurrent).
Data Source
AI summary
A pixel array includes a plurality of dark pixel sensors configured to generate dark current calibration information for a plurality of visible light pixel sensors included in the pixel array. The plurality of dark pixel sensors may generate respective dark current measurements for each of the plurality of visible light pixel sensors or for small subsets of the plurality of visible light pixel sensors. In this way, each of the plurality of visible light pixel sensors may be individually calibrated (or small subsets of the plurality of visible light pixel sensors may be individually calibrated) based on an estimated dark current experienced by each of the plurality of visible light pixel sensors. This may enable more accurate dark current calibration of the visible light pixel sensors included in the pixel array, and may be used to account for large differences in estimated dark currents for the visible light pixel sensors.