Neutral Density Filter for Longwave Infrared Welding Imaging
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Solution Overview
Problem
Current methods for remotely observing welding processes, particularly arc welding, face significant challenges in image quality due to high-temperature, high-intensity light interference, leading to degraded images and safety concerns with external lighting, and existing infrared imaging techniques struggle with saturation and noise from intense radiation.
Innovation Solution
Employing a longwave infrared camera in conjunction with a neutral density filter made of transparent polystyrene, which attenuates longwave infrared radiation and resists heat, allowing for effective imaging of welding arcs and weld pools without external lighting and minimizing camera saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If filtered visual light or external lighting is used to observe welding arcs, then arc light interference is reduced, but image quality degrades significantly
Solution Approach 1:
The patent introduces a neutral density filter as an intermediary component between the camera and the welding arc. This filter uniformly attenuates the intensity of the arc radiation across all wavelengths without selectively blocking specific bands, thereby reducing the harmful arc light interference while preserving the complete spectral information needed for high-quality imaging of the weld pool and arc dynamics.
Solution Approach 2:
The patent changes the imaging parameter from visible light to longwave infrared radiation. By operating in the LWIR spectral region, the system captures thermal radiation emitted by the hot welding arc and weld pool, providing natural illumination without requiring external lighting sources and avoiding the need for complex filtering that degrades image quality.
2Object-affected harmful factors
If band-pass filtering is used to suppress arc radiation, then specific wavelengths are rejected, but complete imaging of weld pool and arc is compromised
Solution Approach 1:
The neutral density filter serves as an intermediary that uniformly reduces the intensity of all wavelengths of arc radiation without selectively blocking any specific spectral bands. This approach maintains the complete spectral information contained in the arc emission, enabling simultaneous imaging of the weld pool, arc, and surrounding areas without the information loss that occurs with band-pass filtering.
Solution Approach 2:
The patent transitions from visible light imaging to longwave infrared imaging, fundamentally changing the spectral parameter. In the LWIR region, the welding arc and weld pool emit strong thermal radiation that provides natural illumination, eliminating the need for external lighting and avoiding the information loss associated with filtering out specific wavelength ranges.
3Object-affected harmful factors
If external laser lighting is used to suppress arc radiation, then specific wavelengths are attenuated, but equipment costs and safety issues increase
Solution Approach 1:
The patent replaces complex external lighting systems with a simple neutral density filter positioned between the camera and the arc. This intermediary component uniformly attenuates arc radiation without requiring high-power lasers or complex optical systems, thereby reducing equipment costs and eliminating occupational safety concerns associated with high-power laser operations.
Solution Approach 2:
The neutral density filter is a simple, inexpensive optical component that can be easily replaced if needed. Compared to expensive external laser lighting systems and complex filtering arrangements, the ND filter provides a cost-effective solution that maintains imaging quality without the safety infrastructure and high equipment costs required for laser-based systems.
4Illumination intensity
If neutral density filter is used to attenuate infrared radiation, then radiation intensity is reduced, but heat resistance of filter becomes critical
Solution Approach 1:
The patent changes the material parameter of the neutral density filter to have low thermal conductivity. This parameter change allows the filter to attenuate intense longwave infrared radiation while resisting heat buildup, as the low thermal conductivity prevents efficient heat transfer through the filter material, maintaining its optical properties and preventing saturation even under high-radiation conditions.
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 provides high-quality, real-time imaging of welding dynamics with improved video frame rates and reduced costs, effectively capturing detailed images of various welding processes without the need for band-pass filters or external illumination, thus enhancing monitoring and study of welding phenomena.
Implementation Method 1
The neutral density filter is characterized by transmission of longwave infrared radiation and by resistance to heat. The neutral density filter attenuates longwave infrared radiation emanating from the entity
Implementation Method 2
Passive detecting/imaging devices do not transmit electromagnetic radiation, but instead receive naturally occurring electromagnetic signals that are emitted or reflected by objects
Implementation Method 3
A type of welding known as 'arc welding' implements a welding power supply to create an electric arc ('welding arc') between an electrode and a base material, thereby melting the metals at the welding point
Implementation Method 4
A filler material is added to form a 'weld pool,' which cools to form a joint of the metal workpieces
Data Source
AI summary
A neutral density (ND) filter made of an LWIR-transmissive, heat-resistant material is interposed between a longwave infrared (LWIR) imager and an entity that is highly emanative of both light and heat. According to exemplary inventive practice, the ND filter is a thermoplastic (e.g., polystyrene) sheet characterized by a thickness in the 1-2 mm range and a thermal conductivity≦0.13 W/m-K. Important parameters of the ND filter include LWIR transmittance (which depends on material and thickness) and thermal conductivity (which depends on material). The quality of the image taken of the entity is affected by the respective degrees of LWIR attenuation by, and heating up of, the ND filter. Accordingly, the material and the thickness of the ND filter are selected to optimize the image, in particular so as to avoid saturation and/or whiting-out of the image due to insufficient LWIR attenuation and/or excessive ND filter temperature.