3D Shape Measurement Based On Phase-Shifting In Electronic Speckle Pattern Interferometry

Electronic speckle pattern interferometry in reverse engineering, machine vision, NDT products online monitoring, especially in the measurement of 3-D shape of object has a broad prospect of application. Is an important branch of the optical measurement, with the advantages of whole field, high accuracy and non-contact. Based on the traditional speckle pattern interferomery, Electronic speckle pattern interferometry has a series of advantages of speckle pattern interferomery.In this paper, the combing with electronic speckle pattern interferometry and phase-shifting and the combing with electronic speckle pattern interferometry with Fourier transform are studied and discussed. In this paper, the cause of formation and generation methods of speckle pattern have been introduced. From two aspects of theory and practice of electronic speckle interfering method is studied, through Reviewing the development of 3-D shape measurement process. The basic principle of measuring 3-D shape with Electronic speckle pattern interferometry is light interference, that is taking two light beams with equal light intensity as object light and reference light respectively. Making object light and reference light interference in order to produce speckle interference fringes. If the measured surface is flat, the interference fringes are straight. Because of the surface height fluctuation the object has, the interference fringes become bend. And the phase information that is included in the bending deformation in the interference fringes. CCD camera is used in Acquisition system. For deformation of the computer access fringe image processing, such as filtering, de-noising and a series of real-time subtraction, then information and extracting phase are worked out, and 3-D surface shape can be reconstructed.Through combining phase-shifting with speckle pattern interference, this paper explains the principle of the 3-D shape measurement in detail, and put forward a kind of experiment al method that is using electronic speckle phase shift technique to measure object's 3-D shape. This method takes the electronic speckle pattern for information carrier interfere stripe, and uses the phase-shifting in order to change the measured phase. The key to the experimental measurement technique such as phase extraction, phase unwarping algorithm and phase-shifting method has been thoroughly discussed in the paper. Based on the theoretical discussion, the experiments are taken on two methods such as the methods to produce fringes(e.g. projection line and electronic speckle interference) and extraction phase methods(e.g. phase-shifting and Fourier transform). To four step phase-shifting, for example, a cylinder surface topography can be simulated by using computer. Based on the principle of electronic speckle interference, respectively for phase-shifting and Fourier transform, the methods of measuring the ball surface topography of the crown obtained satisfactory results of the experiment.