Pixel-Level Dark Current Compensation Using Temperature Sensor Pixels
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Solution Overview
Problem
Conventional image sensors struggle to accurately compensate for dark current noise in image signals due to temperature variations across the sensor array, as single temperature readings from junction sensors fail to represent conditions at all pixels, leading to inaccurate correction values.
Innovation Solution
Incorporating temperature sensor pixels with increased dark current generation capabilities, arranged around the array, to provide localized temperature estimates used for calculating precise dark current compensation values for each image sensor pixel, thereby improving noise reduction across the image sensor array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single junction sensor is used to measure temperature, then device complexity is reduced, but measurement precision deteriorates because it cannot accurately capture temperature variations across different locations of the image sensor array
Solution Approach 1:
The image sensor array is divided into multiple regions, each with its own temperature sensor pixel. This segmentation allows each sensor to measure temperature locally, capturing spatial temperature variations across the array rather than using a single centralized sensor.
Solution Approach 2:
Temperature sensor pixels are distributed throughout the image sensor array, with each sensor providing temperature measurements for its local region. This local quality approach ensures that temperature compensation can be applied specifically to each region based on its actual temperature conditions.
2Measurement precision
If temperature sensor pixels are distributed around the array, then measurement precision improves for capturing temperature gradients, but device complexity increases due to additional sensors and processing requirements
Solution Approach 1:
The temperature sensor pixels use the same photodiode structure as image sensor pixels, allowing them to serve dual purposes: temperature measurement and potential image capture. This multi-functionality reduces the need for completely separate temperature sensing hardware.
Solution Approach 2:
The temperature sensor pixels utilize their own dark current generation characteristics to self-measure temperature. By measuring the dark current produced by each temperature sensor pixel, the system obtains temperature information without requiring external temperature sensors or additional measurement infrastructure.
3Device complexity
If dark current compensation is applied uniformly across the array, then processing complexity is reduced, but reliability deteriorates because it cannot account for local temperature variations and produces inaccurate correction
Solution Approach 1:
The image sensor array is divided into multiple regions, each with its own temperature sensor pixel. This segmentation allows each sensor to measure temperature locally, capturing spatial temperature variations across the array rather than using a single centralized sensor.
Solution Approach 2:
Temperature sensor pixels are distributed throughout the image sensor array, with each sensor providing temperature measurements for its local region. This local quality approach ensures that temperature compensation can be applied specifically to each region based on its actual temperature conditions.
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 effectively compensates for temperature-dependent dark current noise, enhancing image quality by providing accurate dark current correction values for each pixel, thus reducing noise and improving sensitivity across the image sensor array.
Implementation Method 1
there is some current (i.e., dark current) in the photodiode even when no light is incident upon the photodiode (due to the inherent movement of electrons across the corresponding semiconductor junction). As the temperature of the photodiode increases, this flow of the electrons, and therefore the dark current, increases.
Data Source
AI summary
An imaging system may include processing circuitry, a lens, and an array of pixels including image sensor pixels and temperature sensor pixels. The image sensor pixels may generate image pixel values in response to image light received through the lens. The temperature sensor pixels may generate thermal estimate signals based on the temperature of the pixel array. The image sensor pixels and temperature sensor pixels may generate dark current. As the temperature of the pixel array increases, the image sensor pixels and temperatures sensor pixels may generate increased dark current. Temperature sensor pixels may generate more dark current than image sensor pixels. Dark current generated by the temperature sensor pixels may be used to generate dark current compensation values that may compensate for the dark current generated by the image sensor pixels.