In the measurement of equi-inclination and Equi-attitude parameters, the four-step phase-shifting method using white light illumination is used to obtain the principal stress direction angles within the range of [-π/2, π/2], which are consistent with the attributes. This replaces the "inconsistent" isoclinic angles in the six-step phase-shifting method, avoiding the "sawtooth-like" errors in the isoclinic line-wrapped phase map and the "distortions" in the isochromatic line-wrapped phase map. The wrapped phase maps of the isochromatic lines are processed using general unwrapping methods, such as the Goldstein branch-cut method and the quality-guided method, to obtain full-field fractional fringe order. Finally, the separation of stresses is conducted to obtain σx, σy, and τxy for the entire field. A comparison is made between the experimental processing results of a radially compressed circular disk and the theoretical values. The error in the static equilibrium check on the 7.5mm diameter section of the disk, located at a distance of 30mm from the horizontal diameter, is 2.27%, meeting the engineering accuracy requirements.
Optical imaging technology is one of the main technology for underwater detection and recognition. However, the serious image noise occurred in the optical imaging and the signal to noise ratio of image decreased, due to water scattering and turbulence, background light interference and other factors. In this paper, an underwater visual image denoising algorithm based on total variation method is proposed to improve the signal-to-noise ratio of the underwater image at the same time keep the detail information of images. Based on the linear noise model of the image, the total variation model of the image is established and the partial differential equation of image problem is converted to optimization problems, which can be solved by gradient descent algorithm and finite difference algorithm. The method based on total variation was proposed to reduce the noise of underwater images compare with other traditional algorithms and verified by the simulation experiment and underwater experiment. Experimental verifications: after the image processing of the algorithm, the objective reference image quality evaluation index image peak signal-to-noise ratio (PSNR) was improved to more than 20 dB, and the score of no reference image quality evaluation index was improved by 4.8 times. The method can be applied to an underwater exploration and image enhancement for scatterer imaging applications.
When imaging an above-water scene from underwater, the water volume in between forms a prism, introducing strong distortion to image even when the water surface is perfectly calm. The above-water scene from the underwater image is analyzed, and a coordinate transformation method based on pinhole camera model is formulated. Two widely used camera configurations are considered and the image rectification results with proposed method are presented.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.