Arbitrary thickness profile metrology of low-Z and monolithic material components with a single X-ray projection

Low-Z and monolithic material components with arbitrary thickness profiles are extensively utilized in heat conduction, biocompatible implants, microfluidics and integrated optics, where precise thickness measurement is crucial for quality control and performance analysis. X-ray micro-computed tomography (micro-CT) is widely employed for thickness metrology of such samples due to its nondestructive nature, high resolution and 3D imaging capabilities. However, the time-consuming projection acquisition and image reconstruction processes hinder it from efficient or dynamic thickness measurements. Additionally, micro-CT struggles with laminar samples. To overcome these limitations, we introduce X-ray phase contrast imaging for the thickness metrology of low-Z materials with arbitrary profiles by accurately retrieving the phase shift of X-rays passing through the sample from a single projection. Calibration using a standard nylon fiber demonstrates that within a 1.33 mm field of view (FOV) the method achieves a mean absolute error of 0.68 µm for cylindrical fibers with diameters of 407.14 µm. We further demonstrate the method's capability for efficient measurement and damage assessment using a worn fiber with complex geometry. Additionally, we applied this method to the thickness measurement and error analysis of a microlens array with varying sub-lens parameters. The 3D profiles of all sub-lenses were obtained from a single projection, facilitating error analysis of height, symmetry and eccentricity. The results highlight the method's advantages, including being in situ, non-contact and high precision, and having a large FOV, flexible adjustability and penetrative measurement capabilities. Our open device design suggests potential applications for dynamic thickness measurements and real-time monitoring of samples within in situ loading devices.