A new infrared preprocessing modality called sequence differential processing is proposed. Different from the cold image subtraction which only decreases the background noise, the proposed modality takes the parallel test into account to preprocess the raw thermal data sequence prior to applying the advanced postprocessing techniques such as principal component thermography and pulsed phase thermography. The results show that the preprocessing method not only effectively reduces the influence of uneven laser energy distribution on detection efficiency but also enhances internal defect information. Moreover, the combination of the proposed preprocessing method with the pulsed phase thermography and principal component analysis algorithms improves the ability of laser infrared thermography to detect defects inside aviation carbon-fiber-reinforced plastics.
To provide a more effective auxiliary tool for maintenance and inspection in small space, a miniature camera optical system is designed. According to the real work situation, a small camera structure with 25 mm long and 16 mm of the focal length has been formed in this paper. At the same time, Zemax software is utilized to analyze the image quality of the camera lens. The results show that the field curvature is less than 0.1 in optical band and the maximum distortion is less than 0.5%.The RMS and GEO of the image formed under the selection of height condition is small. Under the condition of different temperature and pressure, the image quality can be ensured and the MTF of this system is greater than 0.35 which meets the design requirements. This structure can be a reference structure for the optical part of a maintenance support system.
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