Image Sensor Dark Pixels for Ambient Light Detection
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Solution Overview
Problem
Stand-alone ambient light sensors in electronic devices consume excessive power and occupy additional volume, making them undesirable for integration in imaging systems.
Innovation Solution
Integrating ambient light sensing capabilities into image sensors by using an array of image sensors with dark image sensors that can detect ambient light and subtract dark current, allowing for efficient low-power ambient light detection without the need for a separate ambient light sensor module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If stand-alone ambient light sensors are used, then ambient light detection capability is provided, but power consumption increases and device volume increases
Solution Approach 1:
The patent combines ambient light sensing functionality with the image sensor by integrating dark pixels into the image sensor array. These dark pixels are optically isolated from scene light but receive ambient light, allowing the image sensor to perform both imaging and ambient light detection functions simultaneously, thereby eliminating the need for a separate ambient light sensor and reducing power consumption.
Solution Approach 2:
The image sensor is designed to serve multiple functions: capturing images through light-sensitive pixels and detecting ambient light through dark pixels. This multi-functional design allows a single component to replace what would traditionally require separate sensors, reducing overall device complexity and power consumption.
2Illumination intensity
If stand-alone ambient light sensors are used, then ambient light detection capability is provided, but device volume increases
Solution Approach 1:
The patent merges the ambient light sensor functionality into the image sensor structure by incorporating dark pixels within the same semiconductor substrate. This integration eliminates the need for additional separate sensor modules, thereby reducing the overall device volume while maintaining ambient light detection capability.
3Measurement precision
If dark pixels are added to image sensor, then ambient light detection precision is improved, but image sensor complexity increases
Solution Approach 1:
The image sensor array is segmented into two distinct types of pixels: light-sensitive pixels for image capture and dark pixels for ambient light detection. This segmentation allows each pixel type to be optimized for its specific function while sharing the same readout circuitry and processing pipeline, thereby improving measurement precision without proportionally increasing overall system complexity.
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 electronic devices to detect a broad range of ambient light conditions with enhanced low-light detection capabilities while minimizing power consumption and manufacturing costs.
Implementation Method 1
image pixels configured to receive incoming light
Implementation Method 2
dark pixels optically isolated from incoming light that prevent incoming light from reaching the dark pixels
Data Source
AI summary
Electronic devices may be provided with image sensors. Image sensors may be configured to capture images during imaging operations and monitor ambient light levels during non-imaging operations. An image sensor may include image pixels that receive light and dark pixels that are prevented from receiving light. An image sensor may include an ambient light detection circuit. The ambient light detection circuit may include an oscillator, timing and control circuitry, and a counter. The oscillator may be switchably coupled to the image pixels and the dark pixels. The counter may be configured to count up oscillator cycles of the oscillator while the oscillator is coupled to the image pixels and to count down oscillator cycles of the oscillator while the oscillator is coupled to the dark pixels. The counter may provide a count value that depends on a signal from the image pixels and a signal from the dark pixels.