Thermo-optic Array Using Reference Elements for Noise Cancellation
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Solution Overview
Problem
Thermal imaging systems face challenges with high costs and complexity due to low signal-to-noise ratios, manufacturing variations, and non-uniformities in optically read thermal devices, which reduce dynamic range and sensitivity.
Innovation Solution
A thermo-optic system with an array of optical elements that includes signal and reference elements configured to provide common-mode and differential-mode responses, using an optical readout subsystem to illuminate and filter signals, thereby reducing unwanted background and signal non-uniformities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cooled arrays of semiconductor sensor devices are employed to reduce noise, then signal-to-noise ratio is improved, but system cost and complexity increase significantly
Solution Approach 1:
The patent replaces the mechanical/physical cooling system with an optical reference-based noise cancellation system. Instead of physically cooling the sensor array to reduce thermal noise, the invention uses optical readout with reference elements to measure and subtract background thermal signals, achieving low noise without the complexity of cryogenic cooling infrastructure
Solution Approach 2:
The patent introduces reference elements as an intermediary mechanism. These reference elements experience the same thermal environment as the signal elements but do not receive the thermal signal of interest. By comparing signal elements with reference elements, the system mediates the noise problem through differential measurement, canceling common-mode thermal background without requiring physical cooling
2Measurement precision
If uncooled systems with MEMS and custom CMOS readout are used to generate high quality imagery, then image quality is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent replaces the complex MEMS mechanical structure with a simpler planar optical element array. Instead of fabricating three-dimensional microstructures with moving parts, the invention uses flat optical elements with thermally responsive optical properties that can be manufactured using standard semiconductor photolithography processes, eliminating the need for complex MEMS fabrication and custom CMOS readout integration
Solution Approach 2:
The patent makes the optical elements serve multiple functions: they act as both the thermal sensing element and the optical modulation element. The same optical element that responds to thermal signals also modulates the readout light, eliminating the need for separate MEMS structures and custom CMOS circuits, thereby simplifying manufacturing while maintaining image quality
3Reliability
If optical readouts are used instead of CMOS readouts to eliminate electrical interconnects, then thermal performance is improved, but contrast is reduced due to large optical background signals
Solution Approach 1:
The patent extracts the background optical signal from the total optical signal by using reference elements. The reference elements experience the same optical background as the signal elements but do not experience the thermal signal. By subtracting the reference element output from the signal element output, the common-mode optical background is removed, leaving only the thermal signal information with high contrast
Solution Approach 2:
The patent implements a feedback mechanism where the reference elements continuously measure the optical background conditions and this information is used to cancel the background in the signal elements. The system uses the reference measurement to actively compensate for and remove the unwanted optical background, maintaining high contrast despite the presence of large background signals
4Measurement precision
If optical elements with thermally responsive optical properties are used, then thermal signal detection is enabled, but manufacturing variations cause signal non-uniformities that reduce dynamic range
Solution Approach 1:
The patent extracts the manufacturing variation component from the total signal by using reference elements positioned adjacent to signal elements. Since reference and signal elements are fabricated together in the same location, they experience identical manufacturing variations. By subtracting the reference element signal from the signal element signal, the common-mode manufacturing non-uniformities are removed, leaving only the thermal signal with enhanced uniformity and dynamic range
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 solution enhances the signal-to-noise ratio and contrast, improving image quality and sensitivity by isolating thermal signals from ambient and manufacturing-induced noise, leading to improved dynamic range and reduced noise in thermal imaging systems.
Implementation Method 1
an array of optical elements each having a thermally responsive optical property
Data Source
AI summary
A thermo-optic system, which may be used for example in thermal imaging, includes an array of optical elements each having a thermally responsive optical property, the optical elements including signal elements and reference elements configured to provide (1) a common-mode response of the optical property to ambient temperature and (2) a differential-mode response of the optical property to a thermal signal appearing across the array of optical elements. The system also includes an optical readout subsystem configured to (1) illuminate the array of optical elements with optical energy at a readout wavelength corresponding to the optical property so as to generate a composite optical signal having common-mode and differential-mode signal components corresponding to the common-mode and differential-mode responses respectively of the signal and reference elements, and (2) filter the composite optical signal to generate a filtered optical signal being substantially the differential-mode image component.