Overlapping response separation and extraction method for ultra-thin sample thickness measurement in chromatic confocal sensor

For measurement of ultra-thin samples thickness in chromatic confocal sensor, the chromatic confocal responses of different surfaces may overlap, inducing peak extraction errors and limiting the measurable thickness. Conventional chromatic confocal algorithms exhibit limitations in separating and extracting overlapping responses. In this article, an overlapping response separation and extraction method is proposed for the thickness measurement of ultra-thin transparent samples. The proposed method is based on second-order numerical differentiation to estimate the initial peak, followed by generalized Gaussian fitting and iterative optimization with false response suppression. Experimental results of wedge air gap measurements demonstrate that the minimum measurable thickness achieved by the proposed method is 25.53 μ m when the relative standard deviation does not exceed 1%, less than 60% of that achieved by conventional methods.