Browsing by Author "Zou, Yunlu"
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Item Open Access Calibration of the inclined contour planes formed on ESPI and optimization of ESPI optical system for contouring(1992) Diao, Hongyan; Zou, Yunlu; Peng, Xiang; Tiziani, Hans J.; Chen, L.Es wird eine neue Konturing-Methode mit einer elektronischen Zweiwellenlängen-Speckle-Interferometrie (TWESPI) vorgeschlagen, bei der zwei Beleuchtungsstrahlen verwendet werden. Die optisch rauhe Oberfläche wird bei einer synthetischen längeren equivalenten Wellenlänge vermessen, so daß durch die Änderung der Wellenlängen eine variable Meßempfindlichkeit erhalten werden kann. Dadurch erweitert diese Technik den Meßbereich der Einwellen-Speckle-Interferometrie und erlaubt die Messung von Konturen steiler Profile als bisher mit der Einwellenlängen-Methode möglich war.Item Open Access Contouring by electronic speckle pattern interferometry employing divergent dual beam illumination(1994) Zou, Yunlu; Pedrini, Giancarlo; Tiziani, Hans J.For contouring of large object surfaces by means of electronic speckle pattern interferometry divergent illuminations were used. A method to shift dual illumination beams was employed to obtain contour fringes. The relationship between the fringes and object depth does not have the same form as in the case of collimated illuminations. It shows that the original measurement data can be corrected. Theoretical analysis and experimental results are presented which are in agreement with each other.Item Open Access Contouring by electronic speckle pattern interferometry with quadruple-beam illumination(1992) Zou, Yunlu; Diao, Hongyan; Peng, Xiang; Tiziani, Hans J.We present a new arrangement for contouring by electronic speckle pattern interferometry with four illumination beams, thereby making it unnecessary to move anything during the measurement.Item Open Access Contouring by modified dual-beam ESPI based on tilting illumination beams(1992) Peng, Xiang; Diao, Hongyan; Zou, Yunlu; Tiziani, Hans J.A new contouring method by modified dual-beam electronic speckle pattern interferometry is proposed. Instead of tilting test object as used in previous single, wavelength techniques by ESPI, we introduce a tilt to the illuminating beams in order to obtain the contour fringe patterns. The most attractive feature of this technique is the possibility of contouring a stationary object so that it would be a more promising method in practical engineering metrology. The theoretical and experimental results show good agreement.Item Open Access Contouring using two-wavelength electronic speckle pattern interferometry employing dual-beam illuminations(1992) Diao, Hongyan; Peng, Xiang; Zou, Yunlu; Tiziani, Hans J.; Chen, L.Es wird eine neue Konturing-Methode mit einer elektronischen Zweiwellenlängen-Speckle-Interferometrie (TWESPI) vorgeschlagen, bei der zwei Beleuchtungsstrahlen verwendet werden. Die optisch rauhe Oberfläche wird bei einer synthetischen längeren equivalenten Wellenlänge vermessen, so daß durch die Änderung der Wellenlängen eine variable Meßempfindlichkeit erhalten werden kann. Dadurch erweitert diese Technik den Meßbereich der Einwellen-Speckle-Interferometrie und erlaubt die Messung von Konturen steiler Profile als bisher mit der Einwellenlängen-Methode möglich war.Item Open Access Derivatives obtained directly from displacement data(1994) Zou, Yunlu; Pedrini, Giancarlo; Tiziani, Hans J.Two flexible shearing methods taking the derivative information directly from the data for displacement measurement are reported. The displacement information is obtained using a holographic recording directly on a CCD (charge-coupled-device) chip. Besides the advantage of taking the displacement information and the derivative information from a same set of data, other characteristics of these methods are that the derivative sensitivity can be controlled after recordings and displacement derivatives along arbitrary directions can be chosen easily. One method is based on the electronic recording which keeps the complex amplitudes of the wave fronts in a computer. The other needs only the phase modulo 2π of the displacement.Item Open Access Design consideration of a dual-beam ESPI optical system for contouring(1993) Diao, Hongyan; Zou, Yunlu; Tiziani, Hans J.A discussion of the essential technical advantages, limitations, various kinds of errors and required characteristics of dual-beam illumination ESPI optical system by tilting illuminations for contouring is attached. Attractive features are the simplification of the optical system, the stationary reference contour planes and the possibility of adjusting various parameters for contouring.Item Open Access Geometry for contouring by electronic speckle pattern interferometry based on shifting illumination beams(1992) Zou, Yunlu; Diao, Hongyan; Peng, Xiang; Tiziani, Hans J.When the method of contouring an object surface by electronic speckle pattern interferometry is based on shifting the illumination beams, the shifted phase of the interference speckle pattern has a new relationship with the depth of the test surface. Therefore the contour interval as well as the fringe sensitivity of this method has new forms. The geometry of such a situation, which differs from that of either the method of two-wavelength contouring or the method of contouring by tilting the test object is presented. The requirements on the experimental conditions for this method are also presented. Experimental results are in agreement with these analyses.Item Open Access A novel approach to determine decorrelation effect in a dual-beam electronic speckle pattern interferometer(1992) Peng, Xiang; Diao, Hongyan; Zou, Yunlu; Tiziani, Hans J.An intrinsic decorrelation effect in a dual-beam ESPI system for contouring application is quantified by simple image processing techniques incorporating experimental data of speckle patterns. Practical limits for the range of application on contouring an object are also considered from the point of view of automatic fringe analysis. An acceptable degree of decorrelation due to the tilt of illuminating beams has been established.Item Open Access A simplified multi-wavelength ESPI contouring technique based on a diode laser system(1992) Peng, Xiang; Zou, Yunlu; Diao, Hongyan; Tiziani, Hans J.A simplified multi-wavelength ESPI contouring technique using a diode laser source has been demonstrated to be a useful tool in the shape measurement of an object. Unlike other type of two-wavelength ESPI contouring systems, the technique described in this paper does not required a master-wavefront illumination and the conjugate condition imposed on the reference beam, the experiment procedure is, therefore, considerably simplified. Instead of modulating the injection current of the diode laser, the alternation of wavelength is achieved by adjusting the temperatures applied to the laser diode so that the problem of visibility reduction due to intensity variations of speckle pattern can be overcome. In addition, the decorrelation effect due to the wavelength change in this specific ESPI contouring system is also analyzed quantitatively in order to show the limitations of this technique on practical applications. Contour fringes of a pyramid, as an example, are obtained from experiments, which are in agreement with theoretical analysis.Item Open Access A simplified multi-wavelength ESPI contouring technique based on a diode laser system. 2, Automatic fringe analysis(1993) Peng, Xiang; Zou, Yunlu; Pedrini, Giancarlo; Tiziani, Hans J.A quantitative fringe analyses of interference patterns generated by a multi-wavelength laser diode ESPI contouring system is discussed. The goal is the accurate determination of the topography of an object with steep surface. The phase change related to the surface geometry is calculated with phase-shifting techniques and the results with different contour sensitivities are presented. Some limitations of this ESPI contouring system are also considered from the point of view of practical applications.