The 3D shape measurement technology based on structured-light with a single camera has many advantageous aspects on usability, such as non-contact, high precision, high speed etc. There are various kinds of software accepting its measurement results readily. That is why it has been widely used in reality. System calibration is the key step before it begins normal scanning, and the setting of parameters in calibration directly affects the accuracy of the measurement. Some problems exist in the process of its calibration, such as the process is complicated and hard to operate, always taking low accuracy for the scanning result. This paper aims to find methods to solve the problems. The 3D scanning system used in the research is composed of a Canada-made Point Grey CMOS industrial camera (FL3-U3-13Y3M-C) with a China-made lens, a Texas instrument projector DLP LightCrafter 4500 EVM.
The parameters that can be set in the process of system calibration are discussed in the paper, and the scanning results with parameter change are evaluated based on the indicators of camera and projector’s reprojection error, scanning resolution and point cloud’s uniformity. The research concludes that the distance between the projector and the calibration board is a key factor needs to be controlled. It can be set up properly based on the indicators for the quality of scanned data, which improves the speed of system calibration and keep the collected point cloud data more stable.
Aerial images captured using time delay and integration (TDI) charge-coupled devices (CCDs) could be blurred by three types of motion: forward image motion, turbulence disturbance and high frequency vibration. This work proposes a method to separately construct the three deterministic models by discerning or calculating the parameters from a single image blurred by all the three ones. Based on these models, we catch and separate the features existing in the power spectrum diagram, and select the methods with the best identification accuracy to the parameters. The results show the approach we mention can promise the accuracy of the determined parameters, which is helpful to improve the result of blind restoration algorithm.
To accurately discern the parameters of high frequency vibration blur model on a single TDI image, the research analyzes the imaging function when high frequency vibration occurs in TDI mode. The method of simplifying the vibration model is offered and verified, which promises the MTF will be only related with motion angle and vibration amplitude. Three algorithms for motion direction discerning are compared with one another, which are Radon transform, autocorrelation analysis and cepstral method. The conclusion reveals that cepstral method can measure the most accurate motion angle. Four algorithms for vibration amplitude discerning are compared, which are the quadratic Radon transform, cepstral analysis, autocorrelation analysis and direct analysis on frequency spectrum. It reveals that direct analysis on Log frequency spectrum is the most accurate for vibration amplitude. The research suggests that composition of cesptral method and direct analysis on log frequency spectrum could obtain the highly accurate parameters in high frequency vibration model.
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