Telecentric Sputter Imaging for Precise Weld Spatter Measurement
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Solution Overview
Problem
Existing sputter measurement systems struggle to precisely measure the size of sputters during welding due to variations in image size based on the distance of the sputters from the camera, leading to inaccurate measurements.
Innovation Solution
A sputter measurement system utilizing a telecentric lens and a back-light source to capture images of sputters within a defined depth-of-field region, combined with an optical filter to block unnecessary light and a controller to classify and measure sputter images with clear edges, ensuring precise size measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional camera is used to capture sputter images, then the system structure is simple, but the measurement precision deteriorates because image size varies with distance from the camera
Solution Approach 1:
A telecentric lens is introduced as an intermediary optical component between the sputter and the camera. This lens acts as a mediator that transforms the optical path to eliminate perspective distortion, ensuring that the magnification remains constant regardless of the sputter's distance from the camera, thereby resolving the measurement precision issue.
Solution Approach 2:
The patent changes the optical parameters by using a telecentric lens with specific focal length and aperture settings. This parameter change transforms the imaging characteristics from perspective-based to telecentric, where the chief rays are parallel to the optical axis, eliminating the variation in image size with object distance.
2Reliability
If the camera captures images at high speed to track moving sputters, then the measurement timeliness is improved, but the reliability deteriorates due to motion blur and incomplete capture within the depth-of-field region
Solution Approach 1:
The patent uses partial action by capturing images only when sputters are within the depth-of-field region of the telecentric lens. Rather than attempting to track every sputter throughout its entire trajectory, the system focuses measurement resources on the specific region where accurate measurement is possible, improving reliability by excluding out-of-focus measurements.
Solution Approach 2:
The system preliminarily defines the depth-of-field region and camera capture parameters before sputter measurement begins. By pre-configuring the telecentric lens focal length and camera exposure timing, the system ensures that measurements are taken under optimal conditions before sputters move out of the measurement zone.
3Measurement precision
If the camera captures all light from the molten portion, then the image brightness is sufficient, but the measurement precision deteriorates due to interference from welding light and other noise
Solution Approach 1:
The patent applies local quality by using an optical filter with specific wavelength transmission characteristics. The filter allows only certain wavelength ranges (corresponding to the backlight source) to pass through while blocking other wavelengths (welding arc light, plasma radiation). This creates local quality in the optical path where only desired wavelengths contribute to the image, improving edge detection precision.
Solution Approach 2:
The patent converts the harmful effect of strong welding light into a benefit by using it to illuminate the sputter from the backlight source. The welding arc itself becomes a secondary illumination source that, when combined with the controlled backlight, enhances sputter visibility while the optical filter eliminates the harmful broadband radiation from the welding zone.
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 accurate measurement of sputter size regardless of distance from the camera, reducing measurement errors and enhancing precision by excluding images with gradated edges and blocking noise light.
Implementation Method 1
a telecentric lens disposed between the molten portion and the camera
Implementation Method 2
a back-light source that emits parallel light toward the molten portion
Implementation Method 3
an optical filter that allows the light having the first wavelength to pass through the optical filter and that blocks the light generated at and around the molten portion during the welding
Data Source
AI summary
A sputter measurement system includes: a camera that captures an image of an observation region including a molten portion that is melted during welding; a telecentric lens disposed between the molten portion and the camera; and a controller that measures a size of a sputter flying from a molten portion based on an image captured by the camera.