Non-contact VUV Optics Temperature Measurement via IR Coating
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Solution Overview
Problem
Current methods for non-contact temperature measurement in optical metrology systems, particularly in VUV systems, face challenges due to the high power illumination sources used, which lead to contamination and absorption issues, and existing solutions like contact sensors and thermal imaging are either invasive or impractical for complex optical components.
Innovation Solution
The application of a material coating with high emissivity and low reflectivity at long wavelength IR wavelengths on optical elements outside the direct optical path, allowing for non-contact temperature measurement using IR imaging, enabling accurate temperature distribution estimation without interfering with the primary measurement light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If contact temperature sensors (e.g., thermocouples) are mechanically attached to optical components, then temperature measurement is simple to implement, but the sensor may damage the optic, show incorrect temperature due to poor thermal conductivity, change the temperature at the contact point, and cannot be installed in sensitive optical systems due to cleanliness and alignment requirements
Solution Approach 1:
The patent replaces mechanical contact-based temperature sensing with non-contact infrared thermography. An infrared camera captures thermal radiation from the optical component surfaces, and a computing system processes these images to estimate temperature distributions. This eliminates mechanical attachment, avoiding damage to optics, thermal conductivity issues, and contamination problems while providing accurate, multi-point temperature measurements.
Solution Approach 2:
The patent changes the measurement parameter from contact-based local temperature to non-contact infrared radiation detection. By detecting infrared radiation emitted by the optical components and using computational algorithms to reconstruct temperature distributions, the system achieves accurate temperature measurement without physical contact, thereby avoiding the limitations of thermocouples in cleanroom optical environments.
2Reliability
If thermal imaging is used to measure temperature of optical components, then non-contact measurement is achieved, but optical components that are transparent or reflective to IR wavelengths cannot be measured accurately
Solution Approach 1:
The patent applies different properties to different parts of the optical system. High-emissivity coatings are applied selectively to specific regions of optical components that are visible to the infrared camera but outside the primary measurement optical path. This local modification enables accurate temperature measurement of otherwise transparent or reflective components without affecting their optical performance in the primary wavelength range.
Solution Approach 2:
The patent introduces high-emissivity coatings as intermediary elements on optical components. These coatings act as mediators that convert the optical component's surface into an effective infrared radiator, allowing the infrared camera to detect temperature accurately. The coatings are positioned in regions visible to the thermal imaging system but outside the primary measurement light path, thus enabling temperature measurement without interfering with the optical function.
3Productivity
If high power illumination sources are used in VUV systems, then radiance improvements are obtained supporting high throughput inspection, but contamination and absorption issues lead to failure of optical components
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring the temperature of optical components using infrared thermography. The computing system processes thermal images to estimate temperature distributions, providing real-time feedback on the thermal state of optical components. This early warning system allows for preventive maintenance and optimization of illumination power levels, preventing thermal damage and contamination while maintaining high throughput operation.
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 precise, non-invasive temperature measurement of optical components, even when they are transparent or reflective to IR, improving the reliability and accuracy of temperature monitoring in high-power optical metrology systems.
Implementation Method 1
a material coating having high emissivity, low reflectivity, and low transmission at long wavelength IR wavelengths is disposed over selected portions of one or more optical elements
Implementation Method 2
temperature measurements of the optical element are performed using long wavelength infrared light (e.g., 8-15 micrometers)
Data Source
AI summary
Methods and systems for performing non-contact temperature measurements of optical elements with long wavelength infrared light are described herein. The optical elements under measurement exhibit low emissivity to long wavelength infrared light and are often highly reflective or highly transmissive to long wavelength infrared light. In one aspect, a material coating having high emissivity, low reflectivity, and low transmission at long wavelength IR wavelengths is disposed over selected portions of one or more optical elements of a metrology or inspection system. The locations of the material coating are outside the direct optical path of the primary measurement light employed by the metrology or inspection system to perform measurements of a specimen. Temperature measurements of the front and back surfaces of an IR-transparent optical element are performed with a single IR camera. Temperature measurements are performed through multiple optical elements in an optical path of a primary measurement beam.