Adaptive Two-Wavelength Single-Camera Imaging Thermography for Metal Additive Manufacturing
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Solution Overview
Problem
Current in-situ monitoring methods for metal Additive Manufacturing (AM) lack accurate and fast full-field temperature measurement capabilities, especially during ultrafast laser metal AM processes, due to limitations in existing sensors and measurement techniques which struggle with capturing transient temperature profiles and emissivity variations.
Innovation Solution
A two-wavelength single-camera imaging thermography system that uses spectral and temporal modulation, along with tunable filters, to adaptively measure temperature profiles, reducing equipment costs and enhancing accuracy by eliminating the need for multiple cameras and accounting for material-specific emissivity variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods (photodiode, thermal couple, infrared camera, off-the-shelf pyrometers) are used for temperature measurement, then the measurement can be performed with simple equipment, but the measurement accuracy and ability to capture full-field temperature profiles is poor
Solution Approach 1:
The patent segments the measurement process by dividing the light path into multiple wavelength-specific channels using beam splitters and bandpass filters. Each wavelength channel captures temperature information at specific spectral bands, enabling multi-wavelength pyrometry that eliminates emissivity dependencies and improves measurement accuracy without requiring a single complex sensor
Solution Approach 2:
The patent transitions from single-point or single-wavelength measurement to full-field multi-wavelength temperature mapping by combining spatial imaging with spectral discrimination. This dimensional expansion from 1D (temperature value) to 2D (spatial temperature distribution) and incorporating wavelength as a third dimension enables comprehensive melt pool characterization
2Speed
If high-speed measurement is implemented to capture ultrafast melting and cooling processes (hundreds of microseconds), then the transient temperature profiles can be captured, but the measurement system complexity and cost increases
Solution Approach 1:
The patent merges multiple wavelength-specific imaging paths into a single camera system using beam splitters and optical combiners. This allows simultaneous capture of multi-wavelength information at high speeds (100,000 fps) using one camera rather than multiple synchronized cameras, reducing system complexity while maintaining measurement speed
Solution Approach 2:
The patent employs periodic modulation of the laser source and synchronous detection techniques to extract temperature information at specific phases of the ultrafast process cycle. This enables capture of transient temperature profiles during melting and cooling phases through time-resolved pyrometry
3Loss of information
If multiple sensors are used to capture comprehensive temperature data, then the measurement coverage is improved, but the data processing complexity and measurement uncertainty increases
Solution Approach 1:
The patent creates a universal measurement system where a single high-speed camera performs multiple functions: capturing spatial temperature distributions, measuring transient dynamics, and providing full-field data across the melt pool region. The multi-wavelength capability further enables simultaneous measurement of temperature and emissivity effects, consolidating what would otherwise require multiple specialized sensors
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
Enables high-speed, high-resolution, and high-precision full-field temperature measurement in metal AM processes, improving process understanding and reducing measurement uncertainties, and is adaptable to various materials and processes.
Implementation Method 1
a beam splitter divides the target light beam into a first light beam and a second light beam
Implementation Method 2
a first band pass filter installed within the first light path conduit for regulating the first light beam to a first wavelength
Implementation Method 3
a second band pass filter installed within the second light path conduit for regulating the second light beam to a second wavelength
Implementation Method 4
a polarizing beam splitter installed in the junction housing, wherein the polarizing beam splitter reflects the first light beam of λ1 wavelength along the same path or a parallel path of the second light beam of λ2 wavelength
Implementation Method 5
a half waveplate installed within the first light path conduit to modulate a polarization ratio of the first light beam of λ1 wavelength
Implementation Method 6
a high-speed camera for imaging the merged light beam
Data Source
AI summary
A two-wavelength, single-camera imaging thermography system for in-situ temperature measurement of a target, comprising: a target light path inlet conduit for receiving a target light beam reflected from the target; a beam splitter installed in a splitter housing at a distal end of the target light path conduit, wherein the beam splitter divides the target light beam into a first light beam and a second light beam; a first light path conduit emanating from the splitter housing comprising a first aperture iris installed within the first light path conduit for aligning the first light beam; a first band pass filter installed within the first light path conduit for regulating the first light beam to a first wavelength λ1 and an optional half waveplate installed within the first light path conduit to modulate a polarization ratio of the first light beam of λ1 wavelength; a second light path conduit emanating from the splitter housing comprising a second aperture iris installed within the second light path conduit for aligning the second light beam; a second band pass filter installed within the second light path conduit for regulating the second light beam to a second wavelength λ2; a junction housing, wherein distal ends of each of the first and second light path conduits are connected to the junction housing; a polarizing beam splitter installed in the junction housing, wherein the polarizing beam splitter reflects the first light beam of λ1 wavelength along the same path or a parallel path of the second light beam of λ2 wavelength that passes directly through the polarizing beam splitter unreflected to create a merged light beam comprising light of λ1 and λ2 wavelengths; and a light path outlet conduit connected to the junction for directing the merged beam to a high-speed camera for imaging.