研究目的
To investigate the effect of temperature on the speckle pattern generated by light scattered from a metallic rough surface and determine the sensitivity of parameters like fractal dimension, lacunarity, and correlation to temperature changes.
研究成果
Fractal dimension is less sensitive to temperature changes compared to lacunarity and correlation, making it more suitable for roughness monitoring in environments with temperature variations. Correlation is highly sensitive and best for detecting small temperature changes, while lacunarity shows intermediate sensitivity. This study provides insights for optimizing speckle pattern analysis in industrial applications where temperature control is difficult.
研究不足
The thermocouples measured temperature inside the sample near the surface, not exactly at the surface, potentially introducing slight inaccuracies. The experiment focused on a single aluminum sample with specific roughness, and results may vary for other materials or roughness levels. The high number of images (around 110,000) required significant processing time (e.g., 9 hours for fractal dimension and lacunarity calculations). Temperature control in industrial settings was noted as a challenge, and the methods may not be directly applicable without adjustments.
1：Experimental Design and Method Selection:
The experiment involved acquiring 8-bit digital images of speckle patterns from a laser-illuminated aluminum rough surface at varying temperatures. Parameters such as fractal dimension, lacunarity, and correlation were calculated using specific algorithms (differential box counting for fractal dimension, gliding box for lacunarity, and standard correlation coefficient).
2：Sample Selection and Data Sources:
An aluminum sample with dimensions 104mm x 38mm x 6mm and an average roughness of 1.3 ± 0.2 μm was used. Speckle pattern images were captured as the sample cooled from high temperatures (up to 452.55°C) to room temperature.
3：3 ± 2 μm was used. Speckle pattern images were captured as the sample cooled from high temperatures (up to 55°C) to room temperature. List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included a DPSS laser (532 nm, 5.0 mW), neutral filters (ND 30A, OD=3.0 and ND=6A, OD=0.6), a monochromatic CCD camera (30 fps), a vitro-ceramic heating plate (Jung, model CV200AP01), K-type thermocouples, an analog-to-digital converter (Datalogger A202), and software (ImageJ with Fraclac and Image CorrelationJ 1o plugins, VirtualDub, Masterlogger). Materials included the aluminum sample and custom holders.
4：0 mW), neutral filters (ND 30A, OD=0 and ND=6A, OD=6), a monochromatic CCD camera (30 fps), a vitro-ceramic heating plate (Jung, model CV200AP01), K-type thermocouples, an analog-to-digital converter (Datalogger A202), and software (ImageJ with Fraclac and Image CorrelationJ 1o plugins, VirtualDub, Masterlogger). Materials included the aluminum sample and custom holders. Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The sample was heated using a controlled heating scheme (5 min to reach final temperature, 60 min stabilization, then natural cooling). Speckle pattern images were captured during cooling, with temperatures recorded every 10 seconds. Images were processed to compute fractal dimension, lacunarity, and correlation for different temperature ranges.
5：Data Analysis Methods:
Data analysis involved calculating fractal dimension, lacunarity, and correlation using ImageJ plugins. Statistical analysis included percentage relative differences to compare parameter sensitivity to temperature changes.
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Confocal microscope
DCM3D
LEICA
Used to assess the average roughness of the aluminum sample according to DIN 4768 norm.
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DPSS laser
532 nm, 5.0 mW
Used as the light source to generate coherent light for producing speckle patterns on the metallic surface.
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Neutral filter
ND 30A, OD=3.0
Used to adjust the laser intensity to avoid camera saturation.
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Neutral filter
ND=6A, OD=0.6
Used to adjust the laser intensity to avoid camera saturation.
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CCD camera
Monochromatic, 30 fps
Used to capture digital images of the speckle patterns without a lens, operating in the diffraction plane.
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Heating plate
CV200AP01
Jung
Used to heat the aluminum sample to various temperatures with a digital controller.
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Thermocouple
K type
Used to measure the temperature inside the aluminum sample near the surface.
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Analog-to-digital converter
A202
Datalogger
Used to convert analog temperature signals from thermocouples to digital data for recording.
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Software
ImageJ
NIH
Used for image processing, including calculations of fractal dimension and lacunarity with plugins.
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Software
Fraclac
Plugin for ImageJ used to calculate fractal dimension and lacunarity from digital images.
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Software
Image CorrelationJ 1o
Plugin for ImageJ used to calculate correlation between digital images.
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Software
VirtualDub
Used to extract frames from the video captured by the CCD camera.
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Software
Masterlogger
Used to monitor and record temperature data from the thermocouples.
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Computer
Intel Core i7 processor, 16 Gb RAM
Intel
Used to process the digital images and perform calculations for the experiment.
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