Sepehr Razi, Mahmoud Mollabashi, Khosro Madanipour,
Volume 9, Issue 1 (International Journal of Optics and Photonics (IJOP) Vol 9, No 1, Winter-Spring 2015)
Abstract
In this work, potential of the nanosecond laser processing technique on manipulating the surface wettability of 316L bio grade stainless steel is investigated. Results show that the steel wettability toward water, improves significantly after the laser treatment. Different analyses are assessed in correlation with wettability using Scanning Electron Microscope (SEM), Scanning Tunneling Microscope (STM) and Energy Dispersive X-ray spectroscopy (EDX). It is found that the improvement in the wettability relates to the combined effects of the increase in the surface roughness, oxygen content and the form of the created surface morphologies. Laser fluence is found as the most dominant processing parameter and the higher the incident fluence results in the higher surface roughness and improvement of the wettability. However, measurements indicate that all the treated surfaces become hydrophobic after air exposure for a few days. It is shown that the time dependency of the surface wettability relates to the chemical activity and the reduction of the Oxygen/Carbon (O/C) ratio on the treated surfaces. The behaviors are further studied with investigating the effects of the keeping environment. The long-term wettability alteration differs for the samples that are kept in different mediums. Results indicate that the nanosecond pulsed laser treatment is a versatile approach to create either hydrophobic or hydrophilic steel surfaces for industrial and medical applications.
Mr Amir Hossein Shahbazi, Prof. Khosro Madanipour, Prof. Ata Koohian,
Volume 9, Issue 2 (International Journal of Optics and Photonics (IJOP) Vol 9, No 2, Summer-Fall 2015)
Abstract
Defocusing effects in modulation transfer function (MTF) measurement of charge coupled device (CCD) cameras is the main focus of current paper. We introduce measuring Point-spread function (PSF) in order to calculate the MTF and further more we will study the shape of MTF and its cut-off frequency by adjusting the lens focusing in different locations. A collimated white light LED by broadband spectra is used as source and our results shows that the cut-off frequency is related to defocusing.
