Phase shifting profilometry (PSP) has been widely used in many fields of application due to its accuracy and precision in obtaining depth information of a surface. One of the many applications that can take advantage of phase shifting profilometry is skin imaging, where PSP can be beneficial in efficacy testing of a certain cosmetic product, scar healing monitoring, etc. The simplicity of digital phase shifting profilometry hardware configuration further support the use of this technology for skin imaging application. Even though PSP and other interferogram based measurement is well known of its insensitivity to background lighting—because of its utilization of structured light pattern as light modulator—in practice, light interaction with surface finish still contributes to error to some extent. In this paper, the combination of frequency filter and spatial filtering is used to compensate that problem as preprocessing step prior to phase analysis. A simple Butterworth bandpass filter is used to isolate the first order harmonic containing modulation information, followed by Mean Curvature Diffusion to eliminate illuminance noise due to reflection from skin surface. Validation of this method was carried out by testing samples of leather having different textures.
Vegetation index is measured using remote sensing with VNIR image acquired by satellites, one of them is PROBA-V. It gathers pair of low resolution (LR) images and high resolution (HR) images. The LR images is acquired faster but contains aliasing. Hence it can be processed into high resolution image using multi frame super resolution. But, to have an ideal LR image as a comparison, new synthetic LR image dataset is generated using only translation, gaussian PSF, and gaussian noise. Two type of approaches are used, reconstruction and regularization. Results from both methods are post-processed using median filter to remove noise due to error in super resolution process and poorly chosen hyperparameter. Then, the result is evaluated using PSNR and SSIM by compared to ground truth from dataset HR images. Also, simple bicubic interpolation is used to measure any information improvement by performing super resolution. For both LR images from dataset and synthesis, highest PSNR and SSIM are provided by regularization method due to its multiple iteration for predicting high resolution image, meanwhile reconstruction method only uses single iteration.
Profile measurement system based on optical method is becoming widely applied. Among many methods that has been developed, Digital Fringe Projection Profilometry (DFPP) technique provides high resolution results. In processing the 2D image to 3D image, DFPP goes through some steps, which are phase extraction, phase unwrapping, and baseline offset removal. The most important step is phase extraction because this part will extract the deformed fringe information that can determine the accuracy of the 3D reconstruction results. In this paper, there are two methods of phase extraction that is observed, which are phase shifting interferometry and spatial carrier interferometry. Experiments are done with a specific made object that has 3 depths and 2 types of indentations. The results of each phase extraction methods are compared on not only how they reconstruct the flat part and the indentation type, but also how they restore the depth information.
Load and age of rails can result in problems such as breakage, depletion, and expansion that can lead to accidents. Rail inspection has been done manually by operator tracing the rails by walking or riding a special inspection vehicle. These methods obviously are inefficient and inaccurate, as operators might be missing some of the defects. In this research depletion detection of rails are conducted by analyzing changes of the area as well as position shifting of laser spot on captured images by utilizing the triangulation principle. Accuracy and efficiency improvement of rail inspection are expected from this method. Prior calibration of the system was conducted using gauge blocks with thickness varying from 19 to 1 mm with 1 mm decrement. Area changes and position shifting of laser spot are later analyzed through image processing. The system was also implemented on R-54 rail type based on the calibration and later be compared to the manual measurement data. It was shown that the system can detect depletion in rail type R-54. The calibration result shows that the deviation percentage of the measurement of laser area are ranging from 11.41% to 13.48% while for the measurement of laser spot position shift is from 6.91% to 8.80%. Implementation on rail type R-54 shows the deviation percentages between proposed method and manual measurement are ranging from 1.52% to 10.04% for the area measurement, while for the position shifting ranged from 1.11% to 12.68%.
Conference Committee Involvement (1)
Third International Seminar on Photonics, Optics, and Its Applications (ISPhOA 2018)
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