Three-dimensional measurement based on structured light has been widely used in many fields. Since center locations are used for calculating 3D coordinates, it is important for measurement accuracy. However, affected by the occlusion, shape or color of the measurement object, the angle between object and measurement system and so on, the gray distribution of stripe is degenerated from symmetric to asymmetric. Stripe center locating accuracy is decreased by asymmetric, and some measurement data with big error which decreasing the measurement accuracy seriously appears. In order to recognize those large error data, a new method is proposed by evaluating the quality of stripe gray distribution. The asymmetrical degree of stripe gray distribution is evaluated by the skewness coefficient of stripe gray distribution. The skewness coefficient is defined by the third-order central moment. Then the relationship between the skewness coefficient of stripe gray distribution and the stripe center locating error is analyzed and established by statistical methods. Based on the relationship, the threshold of skewness coefficient is set according to the requirement of measurement accuracy. The asymmetry of gray distribution is estimated by calculating the coefficients. According to the skewness of stripe gray distribution and threshold large error data with low reliability are identified. Higher measuring accuracy is achieved by rejecting the identified data. The validity and reliability of the method have been proved by experiments.
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