Millimeter Wave Radiometer for Infrared Camera Calibration
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Solution Overview
Problem
Non-contact temperature measurement techniques face significant errors due to variations in object emissivity, which is difficult to predict accurately, especially in additive manufacturing and other applications where contact methods are not feasible.
Innovation Solution
A passive millimeter wave radiometer system that simultaneously measures thermal emission and emissivity using a dual-wave receiver system, enabling real-time non-contact temperature measurement and correction by employing a parabolic mirror, optical chopper, and lock-in amplifiers to calculate corrected temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-contact temperature measurement methods are used, then contact temperature measurement is avoided in processes where contact methods are not feasible, but large errors occur due to emissivity variation
Solution Approach 1:
The patent introduces a reference body with known emissivity properties as an intermediary element in the measurement system. By comparing the thermal radiation from the target object against this reference standard, the system can compensate for emissivity variations and achieve accurate temperature measurements without physical contact. The reference body serves as a mediator that enables correction of the emissivity-related measurement errors.
Solution Approach 2:
The system employs dual-wavelength or multi-wavelength radiation detection to measure thermal emission at different spectral parameters. By analyzing the radiation intensity ratios across different wavelengths and applying emissivity correction algorithms, the system dynamically adjusts for emissivity variations. This parameter-based approach allows accurate temperature determination despite unknown or varying emissivity characteristics of the measured object.
2Measurement precision
If emissivity correction is attempted using traditional methods, then temperature accuracy may be improved, but the complexity of the measurement system increases
Solution Approach 1:
The measurement system is segmented into distinct functional modules: radiation detection components, reference body subsystem, signal processing units, and temperature calculation algorithms. This modular segmentation allows each component to be optimized independently and simplifies the overall system architecture. The reference body subsystem can be separately calibrated and maintained, reducing the complexity burden on the main measurement system.
Solution Approach 2:
The patent designs the measurement system with universal components that can handle both reference body measurements and target object measurements using the same optical path and detection hardware. The dual-wavelength detection system serves multiple functions: measuring target radiation, measuring reference body radiation, and providing internal calibration. This multi-functionality reduces the need for separate specialized equipment, thereby limiting the increase in system complexity.
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 accurate temperature measurement from cryogenic to high temperatures, reducing errors associated with emissivity variations and enabling real-time process control in challenging environments like additive manufacturing.
Implementation Method 1
a waveguide disposed in a primary light path from the source, the waveguide configured to collect and guide the light along the waveguide
Implementation Method 2
a parabolic mirror disposed in the primary light path from the waveguide. The light wave radiometer also includes a window disposed in the primary light path to pass focused light from the parabolic mirror
Implementation Method 3
an optical chopper disposed in the primary light path, the optical chopper disposed at an angle relative to an axis of the primary light path such that the optical chopper periodically allows the focused light to pass into a secondary light path and a tertiary light path
Implementation Method 4
a first radiometer receiver disposed in the secondary light path. The light wave radiometer also includes a second radiometer receiver disposed in the tertiary light path
Implementation Method 5
a first lock-in amplifier electrically connected to the first radiometer and configured to generate a first signal in response to receiving light in the secondary light path. The light wave radiometer also includes a second lock-in amplifier electrically connected to the second radiometer and configured to generate a second signal in response to receiving light in the tertiary light path
Data Source
AI summary
An apparatus for accurate measurement of surface and sub-surface temperatures of an object from a distance without contacting the object is provided. Illustrative embodiments provide for simultaneous measurement of thermal emission and emissivity in the mm-wave regime thereby enabling real-time non-contact measurement of emissivity. Corrected temperatures for the object which may be used for calibration of infrared thermographic cameras are determined from the measurement of emissivity.