Dr. Vebi Nadhira Profile

Dr. Vebi Nadhira

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Publications (4)

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Proceedings Article | 12 March 2021 Paper

Improvement of digital phase shifting profilometry skin imaging by combination of frequency and spatial filtering

Naila Zahra, Dwi Astuti, Brigitta d'Avriella, Vebi Nadhira, Suprijanto Suprijanto

Proceedings Volume 11789, 1178906 (2021) https://doi.org/10.1117/12.2585577

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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.

Proceedings Article | 12 March 2021 Paper

Laser distance meter for cylinder tank volume measurement system

Endang Juliastuti, Vebi Nadhira, Naila Zahra, Durotul Muntafiah, Putu Ayustin Suriasni

Proceedings Volume 11789, 117890M (2021) https://doi.org/10.1117/12.2585570

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One of standard measuring device used in legal metrology is a vertical storage tank (also known as cylindrical tank) which is a standard measuring tank having a circular cross section and stands on a solid and fixed foundation. To maintain the truth value of a vertical storage tank, a calibrating and re-calibrating process must be carried out. Measuring instruments used in the calibrating and recalibrating process currently have several drawbacks, such as unaffordable prices and impractical use. In this study a cylinder tank volume measurement system was made by utilizing a laser distance gauge. The system using the travel time measurement principle in measuring the radius and height of the vertical storage tank to obtain the value of tank volume. To validate the system a miniature prototype of a vertical storage tank with an actual radius of 2.021 m and a height of 6.083 m was used. The instrument is positioned close to the center point of the vertical storage tank to measure its radius and height. The measuring tool rotates 360° to take 200 measurement data. From the experiment the instrument obtained the average volume measurements with an error of 3.087% and 3.283%.

Proceedings Article | 12 March 2021 Paper

Reconstruction and regularization multi frame super resolution on vegetation index NIR image

Ahmad Zahi Ulul Azmi, Suprijanto Suprijanto, Vebi Nadhira

Proceedings Volume 11789, 1178905 (2021) https://doi.org/10.1117/12.2585559

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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.

Proceedings Article | 11 April 2019 Paper

Measurement of skin wrinkles differences using novel optical skin imaging system of digital fringes profilometry

Dina Sari, E. Juliastuti, V. Nadhira

Proceedings Volume 11044, 1104406 (2019) https://doi.org/10.1117/12.2503421

KEYWORDS: Skin, Cameras, Imaging systems, Projection systems, Digital Light Processing, Tissue optics, 3D modeling, Image processing, Nonlinear filtering, Phase shift keying

Read Abstract +

Wrinkle is one of skin properties used to indicate aging or environment damage in human body. This feature can be assessed through contact and non-contact methods. Dermatology industry often utilizes tools such as dermatoscopy, however it lacks the ability to yield wrinkle's depth and requires contact with skin, which are not preferable because possibility of deforming skin's natural texture. These lead to the development of digital fringe profilometry which utilize phase-shifted fringes being projected to the skin. This method can satisfy both wrinkle's depth and non-invasive measurement.

A novel system of digital fringe profilometry technique is presented, which used newly improved camera technology preferred by the dermatological industry and a projector, both are commercially available, with new configuration suitable for skin measurement. The system is configured with certain height and angle to respectively project fringes and obtain images. Images will later be processed using phase shifting interferometry (PSI) and global phase unwrapping. The processing system will produce wrapped phase and absolute phase value. In order to prove system's feasibility, experiment was done by sampling two areas from three fingers. Quantitative analysis was done through statistical paired T-Test to see the system ability to acknowledge significant difference of two groups' skin topographic condition. Based on the T-Test, P value that was obtained is 0.003915, which concluded that the system is capable of quantifying two different skin topographic conditions and provide significantly different results.

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