Image sensor with in-pixel background subtraction and motion detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current image sensors face challenges in effectively distinguishing objects in the foreground from the background and detecting motion in external scenes, especially under varying lighting conditions, which limits their application in real-time monitoring and augmented/virtual reality systems.
Innovation Solution
A voltage domain global shutter image sensor system utilizing an infrared illumination source with a 940 nanometer wavelength, capturing two sequential images – one without and one with infrared illumination – and subtracting them to isolate foreground objects and detect motion, while minimizing visible distraction and ambient light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional image sensors are used to capture images in varying lighting conditions, then the sensor can operate in different environments, but it cannot effectively distinguish foreground objects from background or detect motion
Solution Approach 1:
The image sensor is divided into multiple pixel types (first pixels for background capture, second pixels for foreground capture) that perform different functions. This segmentation allows each pixel type to be optimized for its specific role, enabling effective foreground-background separation and motion detection while maintaining operation across varying lighting conditions.
Solution Approach 2:
The patent utilizes changes in infrared illumination parameters to differentiate between background and foreground. By capturing images with and without infrared illumination and comparing the differences, the system can isolate foreground objects and detect motion, achieving high detection accuracy while adapting to different lighting environments.
2Measurement precision
If infrared illumination is used to enhance object detection, then foreground objects can be isolated from background, but visible distraction and ambient light interference occur
Solution Approach 1:
The patent applies different quality characteristics to different parts of the imaging system. First pixels are optimized for capturing background information with reduced infrared sensitivity, while second pixels are optimized for capturing foreground information with enhanced infrared sensitivity. This local differentiation allows effective foreground isolation without visible distraction to users.
Solution Approach 2:
The patent introduces an intermediary processing mechanism that captures images through multiple pixel types and performs differential processing. This intermediary approach separates the background and foreground capture functions, allowing infrared illumination to enhance foreground detection while minimizing visible distraction and ambient light interference through selective pixel response.
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 enhances object detection and motion analysis in real-time monitoring and AR/VR applications by providing clear, unobtrusive imaging and reducing the impact of ambient light, enabling continuous monitoring without distracting the user.
Implementation Method 1
an infrared illumination source with a 940 nanometer wavelength
Implementation Method 2
pixels having photosensitive elements (e.g., photodiodes) that absorb a portion of the incident image light and generate image charge upon absorption of the image light
Data Source
AI summary
An imaging system includes a pixel array configured to generate image charge voltage signals in response to incident light received from an external scene. An infrared illumination source is deactivated during the capture of a first image of the external scene and activated during the capture of a second image of the external scene. An array of sample and hold circuits is coupled to the pixel array. Each sample and hold circuit is coupled to a respective pixel of the pixel array and includes first and second capacitors to store first and second image charge voltage signals of the captured first and second images, respectively. A column voltage domain differential amplifier is coupled to the first and second capacitors to determine a difference between the first and second image charge voltage signals to identify an object in a foreground of the external scene.