研究目的
To address the problem of silicon-based cameras being sensitive to temperature variations in the near infrared range, leading to image saturation or poor dynamic range, by developing a technique for real-time automatic adjustment of exposure time to maintain stable gray level images during temperature changes.
研究成果
The study successfully develops and validates an innovative technique for automatic exposure time adjustment using Planck's algorithm, enabling stable gray level images during temperature evolution. Experimental results show high accuracy with temperature differences less than 1 K, proving the technique's effectiveness and reliability for near infrared thermography applications.
研究不足
The technique is validated for a narrow temperature range (200 K for blackbody, up to about 200 K for specimen). It assumes operation in a dark room to minimize surrounding radiation effects, which may not be practical in all environments. The algorithms may require further optimization for broader temperature ranges or different materials.
1：Experimental Design and Method Selection:
The study involves designing experiments to validate algorithms for exposure time adjustment. Radiometric models based on Planck's law are used, with calibration via least square method. Home-made Labview software controls image acquisition and exposure time adjustment.
2：Sample Selection and Data Sources:
A blackbody (temperature reference source) and a Ti-6Al-4V titanium alloy specimen coated with black paint are used. Images are acquired from a CMOS camera, with temperature data from a pyrometer and thermocouples.
3：List of Experimental Equipment and Materials:
Includes a blackbody with temperature controller (RCN 1200 N1 by HGH), 8-bit CMOS camera (Viewworks VC-12MC) with Nikon ED 200 mm lens, computer with Labview software, pyrometer, and thermocouples. Materials involve black paint and titanium alloy specimen.
4：Experimental Procedures and Operational Workflow:
Experiments are conducted in a dark room. For blackbody heating, temperature is varied from 1024 K to 1224 K, and exposure time is adjusted automatically using the software. For specimen heating, temperature is controlled from 873 K to 1023 K with a heating rate of 5 K/s. Images are acquired, and mean gray levels are monitored.
5：Data Analysis Methods:
Data is analyzed using Matlab for simulations. Radiometric model parameters are calibrated, and errors are calculated. Thermal fields are reconstructed based on the radiometric model.
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