Digital speckle pattern interferometry (DSPI) is a full-field optical testing technique that can be used to measure tiny deformations and strains. It has been widely used in aerospace, precision manufacturing and other fields. However, the lack of effective calibration method has prevented the wider adoption of this technique. In the measurement process of DSPI, there are phase shift errors, phase noise, phase map processing algorithm errors, geometric sensitivity factors miscalibration, etc., which will lead to the final measurement error. Item-by-item calibration of the aforementioned error sources faces many difficulties in implementation and does not work well. Comprehensive calibration would be a better solution to minimize the measurement error but it is hard to perform due to the lack of suitable references for deformation measurement. In this paper, a comprehensive calibration method based on the theory of three-axis angle motions measurement using DSPI has been proposed. The tiny three-axis angle motions are loaded by Piezoelectric actuators and measured using a DSPI device based on the DSPI three-axis angle motions measurement theory. A multi-axis interferometry is used to measure the three-axis angle motions simultaneously and its output is used as the measurement reference. Because the angle motions of a rigid body instead of the deformations of an elastic body are measured, the measurement reference is readily available, yielding the successful precision calibration of the DSPI.
A method of simultaneous and precision measurement of yaw and pitch based on digital speckle pattern interferometry is proposed. The relationship between the yaw/pitch and phase distribution is analyzed in detail, resulting in the establishment of the yaw and pitch simultaneous measurement model. A plane fitting method is proposed to separate the two angle motions from a single phase map. The proposed method enjoys the advantages of being free of cooperative target, high-resolution measurement, and compact optical setup. Experimental results show the mean absolute error of the measurement is <1 μrad.
A non-contact and non-cooperative method of angle measurement based on digital speckle pattern interferometry (DSPI) was introduced in this paper. Studies have shown that when the illumination angle of the DSPI system was every small, the angle can be determined according to the interferometric phase distribution and the length of the measured object. Thereby a direct relationship between the angle and the phase distribution was established. In our experiments, the resolution of measurement system was 0.00025° ( 0.9”), proving that the proposed method is effective for measuring small angles. Theoretically, this method can achieve higher resolution if the measurement noise can be minimized.
Recently, a non-cooperative method of roll angle measurement using digital speckle pattern interferometry (DSPI) is introduced. Mechanism was deduced and the mathematic model of roll angle measurement was established. The novel method also enjoys some other advantages, such as high-accuracy, stand-off, non-contact, and full-field measurement. However, this method is only used for precise measurement of very small roll angle which is up to a few milliradians due to the limitation of DSPI’s measuring range. In this article, a means of range enlargement for DSPI roll angle measurement is introduced. With this means, large roll angle can be divided into a number of small angles which are measured in sequence. Therefore, the large angle is then determined by calculating the sum of these small angles. The proposed method of roll angle is characterized by high-resolution and large-range measurement.
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