Implementation of line-scan dispersive interferometry for defect detection

Surface assurance is one of the main concerns for advanced manufacturing technologies such as Roll-to-Roll (R2R) technique. The undesired defects present on the barrier films make R2R products suffer from a low efficiency and short life span. In order to enhance the performance and the yield of the products, an inspection system enabling in-line metrology of functional surfaces in production lines is desirable to optimise the manufacturing processes. This paper reports an instantaneous line-scan dispersive interferometry which has sufficient resolutions and nano-scale measurement repeatability to detect defects on flexible PV films. Free from any mechanical scanning and obtaining a surface profile in a single shot allows this setup to minimise environmental effects and to be used on the shop floor. The captured spectral interferogram is analysed using a FFT based algorithm, and the process time can be accelerated through data parallelism using a graphics processing unit (GPU). The performance of the developed system was evaluated experimentally by measuring the polyethylene naphthalate (PEN) films provided by the Centre for Process Innovation (CPI). The experimental details and results are presented in this paper.