Ambient IR Detection in Solid State Sensors Using OBIR Pixels
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Solution Overview
Problem
Existing image sensors equipped with infrared (IR) cutoff filters struggle to reliably detect ambient IR levels, which are crucial for accurate white balance in varying lighting conditions, as they cannot distinguish between white and non-white objects and often rely on estimation techniques, leading to inaccuracies in color reproduction.
Innovation Solution
The implementation of optically 'black' IR-sensitive (OBIR) and optically 'black' IR-blocking (OIRB) pixels, along with a patterned IR cutoff filter and barrier pixels, allows for the detection of IR illumination by averaging and normalizing signals from OBIR pixels, enabling the calculation of IRavg and subsequent adjustment of white balance algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an infrared cutoff filter is placed in front of the sensor to block IR illumination, then color reproduction accuracy is improved, but the ability to detect ambient IR levels is lost
Solution Approach 1:
The sensor array is segmented into two distinct types of pixels: standard pixels covered with IR cutoff filters for accurate color imaging, and specialized OBIR pixels without IR cutoff filters for detecting ambient IR levels. This segmentation allows both color accuracy and IR detection to coexist by assigning different functions to different sensor regions.
Solution Approach 2:
OBIR pixels act as intermediary elements that bridge the gap between the IR cutoff filter system and the need for IR detection. These pixels are strategically positioned within the sensor array and provide IR level information that is then used by the image processor to adjust white balance algorithms, thereby mediating between the conflicting requirements of color accuracy and IR detection.
2Device complexity
If white balance algorithms rely on estimation techniques to determine color temperature, then device complexity is reduced, but measurement precision of IR levels deteriorates
Solution Approach 1:
The system implements a feedback mechanism where OBIR pixels continuously provide ambient IR level measurements to the image processor. The image processor uses this feedback information to dynamically adjust white balance algorithms, replacing estimation techniques with actual measurement data. This feedback loop ensures high measurement precision while maintaining relatively simple algorithm implementation.
3Reliability
If OBIR pixels are integrated into the sensor array, then IR detection capability is improved, but device complexity increases
Solution Approach 1:
OBIR pixels are designed with multi-functionality to reduce overall device complexity. These pixels serve dual purposes: they detect ambient IR levels for white balance adjustment and can also contribute to visible light imaging when needed. This universal approach allows the sensor to maintain high IR detection reliability while minimizing the increase in device complexity by reusing existing pixel infrastructure for multiple functions.
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 accurate measurement of IR levels, allowing for effective white balance adjustments, even in high-dynamic-range scenarios, by differentiating between IR and visible illumination sources, thereby improving color accuracy in captured images.
Implementation Method 1
The sensor is comprised of a substrate that incorporates a plurality of pixels or photodiodes. The photodiodes are responsible for converting light into an electrical signal for use by the circuitry that reads the photodiode information.
Implementation Method 2
An infrared filter 120 is positioned over the CFA 112. The infrared filter 120 blocks infrared radiation such that only visible wavelength illumination reaches the photodiodes 101-104 under the infrared filter 120.
Data Source
AI summary
An image sensor device has a first region configured to sense only infrared illumination and a second region configured to not sense visible and infrared illumination.