A Spectral-Domain Low-Coherence Method for Measuring Composite Windshield Thickness

To improve the performance and reduce the weight of new-generation transparent windshields in aircraft, composite structures are commonly used. The thickness of each layer in a composite windshield has a significant impact on its optical properties and load-bearing capacity. However, existing thickness measurement methods for transparent windshields either cannot meet the requirements in terms of range and efficiency, or cannot measure the thickness of each layer in a transparent windshield. In this article, a large-range spectral-domain low-coherence measurement method for composite transparent windshield thickness is proposed. Specifically, 2-D dispersion technology is used to significantly increase spectral resolution, thereby achieving an improvement in measurement range. Then, a spectral stitching and wavenumber calibration method based on automatic fringe generation is proposed to achieve the conversion from spectral domain to spatial domain. Finally, a fully fiber-coupled co-path spectral-domain low-coherence measurement system for transparent windshields is constructed. Measurement experiment of standard measurement blocks and composite transparent windshields demonstrate that the proposed method has a range of up to 41 mm, a speed of up to 440 Hz, and an accuracy of up to 0.005 mm, thus validating the effectiveness of the proposed method.