Experimental Study On The Temperature Field Measurement And Surface Roughness Measurement By Digital Holography

The holographic interfereometry has been used to many fields. Although the conventional optical holographic interfereometry can realize the measurement of the objects, the non-real-time processing of the holograghic plate limits its practical application greatly. With the development of the high-resolution opto-electronic sensors like CCD/CMOS and high-speed computer technology, the digital hologram can be reconstructed numerically,which enables the digital holography developed rapidly. Digital holography is based on the optical holography. The hologram is recorded by CCD and transferred to a computer. The reconstruction is fulfilled digitally in the computer with the simulated reference wave. So, the whole procedure of the digital holography could be digitized, including the storage and transmission of the hologram. As the quantitive amplitude and phase information of the whole wave field can be obtained from only a single hologram after preprocessing by using a certain reconstruction algorithm, phase compensation, and proper phase-unwrapping algorithm, which makes the digital holography to actualize non-invasion, real-time, quantitative full-field measurement, so that digital holography have many potential applications. Based on the theoretical analysis and corresponding experimental research, this paper addresses the temperature field measurement and surface roughness measurement by lenless Fourier transform digital holography. The main contents are as follows:1,There is the particular relationship between the temperature field distribution under investigation and the phase distribution of the light waves passing through the temperature field. Since the digital holography can quantitatively recover the high-resolution phase distribution information of the temperature field, it can be adopted to realize the non-contact temperature measurement for the whole temperature field distribution. In this paper, the transmission lensless Fourier transform digital holography is performed to measure the temperature field distribution surrounding an electric soldering iron at different positions and the corresponding variations in the different heating steps firstly. Then, the temperature distribution near the metal plate of a radiator is measured. For the comparison, the temperature measurement system within the radiator is used to measure the temperature distributions. The results obtained by these two methods are in good agreement, which demonstrates that the digital holography method is valid for the measurement of the temperature distribution.2,Since the quantitative phase information of the object can be related to the height variation of the object and the transparent medium with constant refractive index, quantitative surface profile of the specimen can be acquired with the accurate vertical phase distribution information. In this paper, the reflection lensless Fourier transform digital holography is presented for detecting surface profiles of the standard roughness sample plates with the arithmetical average height of 3.2um and 1.6um respectively. Comparing the arithmetical average height of the standard roughness sample plates obtained from the experiment by the digital holography with the given parameters, the results are in good agreement, which demonstrates the effectiveness of this method for the measurement of the surface roughness.