MEMS acoustic film surface defect detection method based on frequency domain transformation

Abstract

The invention discloses a frequency domain transformation-based MEMS acoustic film surface defect detection method, which comprises the following steps of: calculating a Fourier spectrogram and a frequency spectrum gradient map of an MEMS acoustic film surface defect image through two-dimensional discrete Fourier transformation, and calculating a segmentation threshold Tg between two peak values in a superimposed gradient histogram through a maximum between-class variance method; and establishing a Boolean mask, performing morphological operation on the Boolean mask, eliminating a dominant frequency component corresponding to the periodic structure identified by gradient calculation in the frequency domain according to the Boolean mask, and performing two-dimensional inverse discrete Fourier transform on the residual frequency spectrum to obtain a reconstructed image containing a defect area, and finally, carrying out binarization segmentation by adopting a threshold method to output a binarization image containing defect information. The problem that a traditional defect detection algorithm depends on an imaging light source and a reference image is solved, and the method has certain anti-noise performance and is not interfered by factors such as image translation, rotation and zooming.

Description

technical field [0001] The invention belongs to the technical field of machine vision, and in particular relates to a method for detecting surface defects of MEMS acoustic thin films based on frequency domain transformation. Background technique [0002] Micro-electro-mechanical systems (MEMS) is a high-tech sensing system that integrates microelectronics technology, mechanical technology and other disciplines, and has been widely used in aerospace, communication and other fields. As the core device in earphones and microphones, MEMS acoustic film is an important executive device for the mutual conversion of acoustic (mechanical vibration) / electrical (voltage, current) signals. However, the device is small in size, diverse in structure and complex in production process, and has extremely high requirements on tape-out, storage and packaging environments. Impurities such as water vapor, fibers, and dust suspended in the air can all attach to the surface of the acoustic membra...

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Problems solved by technology

Although the Gabor transform conforms to the characteristics of human visual perception and has good orientation selectivity, it requires a large amount of calculation to formulate filter parameters, which does not meet the needs of rapid detection.

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