Integrated Dual-Band Focal Plane Array for Visible and Infrared Imaging

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Solution Overview

Problem

Conventional infrared detector arrays require separate focal plane arrays for visible and infrared spectra, leading to increased complexity and cost due to thermal mismatch issues with non-silicon-based window materials, and existing multi-spectral imaging solutions are cumbersome and costly.

Innovation Solution

An integrated multi-band focal plane array is developed, allowing simultaneous imaging in both visible and infrared spectra using a single array with a suspended low thermal mass microbolometer structure and integrated CMOS imaging circuitry, enabling high-speed infrared detection and visible spectrum imaging within the same pixel element.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If separate focal plane arrays are used for visible and infrared spectra, then imaging capability for both spectra is achieved, but device complexity and cost increase

Engineering Contradiction:

Improveimaging capabilityVSAvoidsystem complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines visible and infrared imaging capabilities into a single integrated focal plane array. The sensor structure integrates a visible light photodetector and an infrared microbolometer detector in one pixel element, allowing simultaneous detection of both spectral ranges through a single device rather than requiring separate arrays.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The integrated focal plane array provides multi-functional capability by enabling both visible and infrared imaging through a single device. The sensor can operate in visible spectrum mode, infrared mode, or combined mode, making it a universal imaging solution that replaces multiple specialized devices.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If non-silicon-based window materials are used for infrared detectors, then infrared detection capability is achieved, but thermal mismatch issues arise

Engineering Contradiction:

Improveinfrared detection capabilityVSAvoidthermal stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent uses silicon-based materials for both the visible light photodetector and the infrared microbolometer detector substrates. This homogeneous material approach ensures matching thermal expansion coefficients and eliminates thermal mismatch issues that would arise from bonding dissimilar materials like non-silicon window materials to silicon detectors.

Inventive Principle:

Principle #33Homogeneity

3Measurement precision

If thermal mass is increased in microbolometer structure, then sensitivity is improved, but response time becomes slower

Engineering Contradiction:

Improvedetection sensitivityVSAvoidresponse time

Core Design Contradiction:

Measurement precisionVSSpeed

Solution Approach 1:

The patent optimizes the microbolometer thermal mass to achieve an optimal balance between sensitivity and response time. By carefully controlling the thickness and material composition of the microbolometer membrane and absorbing layer, the design achieves sufficient thermal sensitivity for infrared detection while maintaining fast response times suitable for high-speed imaging applications.

Inventive Principle:

Principle #35Parameter changes

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 reduces thermal response time, enables high frame rates, and simplifies the imaging system by integrating both spectral imaging capabilities into a single focal plane array, reducing complexity and cost while maintaining high sensitivity and accuracy.

Implementation Method 1

Infrared (IR) detectors are often utilized to detect fires, overheating machinery, planes, vehicles, people, and any other objects that emit thermal radiation

Methodology Applied

Scientific EffectThermal radiation detection: Infrared Radiation

Implementation Method 2

Conventional microbolometers measure the change in resistance of a detector element after the microbolometer is exposed to thermal radiation

Methodology Applied

Scientific EffectResistive heating: Joule Heating

Implementation Method 3

Microbolometer detector arrays consist of thin, low thermal mass, thermally isolated, temperature-dependent resistive membrane structures

Methodology Applied

Scientific EffectThermal isolation: Thermal Insulation

Data Source

PatentUS7459686B2Systems and methods for integrating focal plane arrays

Publication Date: 2008.12.02 L3 TECHNOLOGIES INC

AI summary

Systems and methods for providing multi-spectral image capability using an integrated multi-band focal plane array that, in one example, may be employed to simultaneously image in the visible spectrum and infrared spectrum using an integrated dual-band focal plane array, e.g., by including visible imaging circuitry within read out integrated circuitry (ROIC) used to readout infrared detector elements within the same pixel element/s.