Integrated Multi-Band Focal Plane Array for Visible and Infrared Imaging
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Solution Overview
Problem
Conventional infrared detector systems require separate focal plane arrays for visible and infrared spectra, leading to increased complexity and cost, and existing multi-spectral imaging solutions struggle with thermal mismatch issues during packaging, which affects the reliability and cost-effectiveness of the imaging assembly.
Innovation Solution
An integrated multi-band focal plane array is developed, capable of simultaneous imaging in both visible and infrared spectra using a single array, where visible radiation is allowed to reach underlying CMOS imaging circuitry through openings in the suspended membrane of a diffractive resonant cavity microbolometer, and a continuous solid membrane structure with a single opening over active CMOS imaging circuitry, enabling high-performance infrared detection with fast response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate focal plane arrays are used for visible and infrared spectra, then imaging capability in both spectra is achieved, but device complexity and cost increase
Solution Approach 1:
The patent combines visible and infrared detector elements into a single integrated focal plane array. Each pixel element contains both a visible light photodetector and an infrared microbolometer detector, allowing simultaneous multi-spectral imaging without requiring separate arrays. This merging approach reduces system complexity while maintaining versatility.
Solution Approach 2:
The integrated pixel element performs multiple functions by detecting both visible and infrared radiation. The single pixel structure serves dual purposes: capturing visible light images and thermal infrared images, eliminating the need for separate imaging systems and reducing overall device complexity.
2Measurement precision
If thermal isolation is increased to improve sensitivity, then sensitivity improves, but response time becomes slower
Solution Approach 1:
The patent applies different thermal isolation characteristics to different parts of the detector structure. The microbolometer elements have enhanced thermal isolation for high sensitivity, while the visible photodetector elements have different thermal characteristics. This localized differentiation allows each sub-detector to optimize its performance independently within the same pixel element.
Solution Approach 2:
The patent enables dynamic switching between detection modes. The integrated circuit can selectively activate either the visible light detector or the infrared microbolometer based on the imaging requirement, allowing the system to optimize response time for fast visible light capture or sensitivity for thermal detection as needed.
3Ease of manufacture
If wafer level vacuum packaging is used, then manufacturing cost decreases, but thermal mismatch issues arise during packaging
Solution Approach 1:
The patent modifies the packaging parameters by implementing wafer-level vacuum packaging, which changes the manufacturing approach from conventional post-fabrication packaging to in-wafer packaging during fabrication. This parameter change reduces manufacturing cost while the design incorporates thermal mismatch compensation strategies to maintain reliability.
Solution Approach 2:
The patent introduces intermediary structures such as thermal anchoring elements and compliant layers that mediate between components with different thermal expansion coefficients. These intermediary elements absorb thermal mismatch stresses during packaging while maintaining the vacuum seal integrity and component functionality.
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 allows for high frame rate operation and cost-effective multi-spectral imaging by integrating visible and infrared imaging capabilities within a single focal plane array, reducing thermal response time and enhancing imaging performance while minimizing thermal mismatch issues during packaging.
Implementation Method 1
Microbolometers are infrared radiation detector elements that are fabricated on a substrate material using traditional integrated circuit fabrication techniques
Implementation Method 2
Microbolometer response time is the time necessary for a detector element to absorb sufficient infrared radiation to alter an electrical property, such as resistance, of the detector element
Implementation Method 3
Microbolometer sensitivity is determined by the amount of infrared radiation required to cause a sufficient change in an electrical property of the microbolometer detector element
Implementation Method 4
They are suspended over silicon ROIC wafers by long thermal isolation legs in a resonant absorbing quarter-wave cavity design
Implementation Method 5
visible radiation is allowed to reach underlying CMOS imaging circuitry through openings in the suspended membrane of a diffractive resonant cavity microbolometer
Implementation Method 6
They are suspended over silicon ROIC wafers by long thermal isolation legs
Data Source
AI summary
Infrared detector elements and methods for forming infrared detector elements in which the top metal layer of CMOS circuitry of the detector element is employed as a lead metal reflector for the infrared detector.