Hybrid Microbolometer Pixel With Shared Readout for Fused IR Imaging
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Solution Overview
Problem
Current thermal cameras are bulky and costly due to separate visible and thermal imaging capabilities, with thermal-only cameras unable to detect visible information like signals and symbols, and typical thermal cameras have lower resolution compared to visible-image cameras, making them unsuitable for small form-factor applications and advanced driver-assist systems.
Innovation Solution
A hybrid pixel for image sensors that combines a resistive microbolometer with a photodiode, sharing the same readout circuitry, enabling fused visible/NIR or visible/LWIR imaging with low self-heating and low power consumption, using a metalens for integrated visible/NIR/LWIR imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate visible imaging and thermal imaging capabilities are used, then imaging functionality is complete, but system bulk and integration difficulty increase
Solution Approach 1:
The patent combines a visible-light photodiode and a thermal microbolometer into a single hybrid pixel structure, merging two separate imaging capabilities (visible and thermal) into one integrated sensor. This eliminates the need for separate cameras and reduces system bulk while maintaining complete imaging functionality across different wavelength ranges.
Solution Approach 2:
The hybrid pixel is designed to perform multiple imaging functions simultaneously - it can capture visible light, near-infrared, and thermal infrared wavelengths using a single sensor element. This multi-functionality allows one device to replace multiple separate imaging systems, reducing overall system complexity and integration requirements.
2Ease of operation
If DC bias current is used for resistive bolometer readout, then readout is achieved, but self-heating of the bolometer increases
Solution Approach 1:
The patent employs periodic modulation of the bias current applied to the microbolometer rather than continuous DC biasing. By switching the bias current on and off at specific intervals, the system achieves necessary readout capability while allowing the bolometer to cool between pulses, thereby significantly reducing self-heating effects and improving measurement accuracy.
3Reliability
If thermal-only imaging is used, then thermal detection capability is provided, but visible information detection is lost
Solution Approach 1:
The hybrid pixel structure merges a thermal microbolometer detector with a visible-light photodiode in the same pixel, enabling simultaneous detection of both thermal infrared radiation and visible light. This combination ensures that thermal detection capability is maintained while visible information is captured concurrently, eliminating the information loss inherent in thermal-only imaging systems.
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
The hybrid pixel provides improved accuracy for infrared images with reduced system cost and processing power consumption, enabling effective night vision and object recognition in ADAS and other applications.
Implementation Method 1
a resistive microbolometer with a photodiode in the same pixel
Implementation Method 2
resistive microbolometer that has no self-heating when not DC biased
Implementation Method 3
a resistive microbolometer with a photodiode in the same pixel
Implementation Method 4
using a metalens for integrated visible/NIR/LWIR imaging
Data Source
Figure 1
Figure 2A~2B
Figure 2C
AI summary
A pixel for an image sensor includes a resistive microbolometer sensor portion, a visible image sensor portion, and an output path. The resistive microbolometer sensor portion outputs a signal corresponding to an infrared (IR) image sensed by the resistive microbolometer sensor portion. The resistive microbolometer sensor portion uses no bias current. The visible image sensor portion outputs a signal corresponding to a visible image sensed by the visible image sensor portion. The output path is shared by the resistive microbolometer sensor portion and the visible image sensor portion, and may be controlled to selectively output the signal corresponding to the IR image, the signal corresponding to the visible image, or a fused image based on the IR image and the visible image. The resistive microbolometer sensor portion may sense a near infrared image or a longwave infrared image.