The resolution of wavelength scanning of diode laser can influence the performance of interferometer mostly. In this article, we propose a method to improve the precision of wavelength calibration by using the theory of energy centrobaric correction for discrete spectrum. An optical wedge whose angle of tilt was known has been set in the optical system to measure the series of wavelength on time using a 2D Fourier Transfer (FT) of the interferograms generated by both surfaces of optical wedge. An energy centrobaric correction method is also put forward to evaluate the distribution of frequency and phase of fringe pattern generated by front and rear surface of optical wedge. The results of simulation and experiment show that the error of wavelength calibration reach to 0.01pm by correlating the distribution of frequency and phase of interferograms. The benefit is that the precision of wavelength of diode laser is improved significantly with a higher signal-to-noise ratio. This method can used to any tunable diode laser wavelength to improve the precision of measurement due to its simplicity and practicability.
Surface and internal defects of object are one of the most important reasons causing product quality problems and failures, including micro-cracks, micro-scratches, nano-deposition particles. In order to obtain the multi-layer information of the object, this paper proposes the wavelength-scanning digital holographic method. The algorithm is simulated to analyze the feasibility of acquiring the layered information of objects and the separation effect. Compared with the micro-hologram by compressive sensor, the result shows that digital holographic tomography based on wavelength scanning has a good separation effect on multi-layer object information and defects can be detected clearly.
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