Index of content:
Volume 28, Issue 4, November 2016
- Technical Articles
Conical microspike morphology formation and control on various metal surfaces using femtosecond laser pulse28(2016); http://dx.doi.org/10.2351/1.4954839View Description Hide Description
Formation of conical microspikes on various metal surfaces (316L stainless steel, Ti-6Al-4V, and Al5754) under femtosecond irradiation at high repetition rate is reported. Two types of microcone morphologies formed at these high repetition rates under high and low-fluence conditions were clearly distinguished. At low fluence (near the ablation thresholds), conical spikes with high aspect ratio and nonuniform distribution forms through random evolution. At high fluence, semiuniform conical spikes are formed through a simultaneous progressive evolution procedure with increasing the number of scans. Experimental results are presented showing the progression of random microspike formation to uniform microspikes as fluence increases and show how scan-speed affects the size of the spikes. Also, extraordinary absorption coefficient is measured for nonuniform conical spike covered 316L stainless steel formed under near threshold condition.
28(2016); http://dx.doi.org/10.2351/1.4954930View Description Hide Description
The photobiological safety of optical radiation emitted by image projectors, particularly of laser illuminated projectors (LIP), is addressed by the recently published product safety standard IEC 62471-5 [Photobiological Safety of Lamps and Lamp Systems—Part 5: Image Projectors (IEC, 2015)]. According to IEC 62471-5, the accessible emission is determined at a distance of 1 m from the projection lens. A classification framework is used to categorize projectors into risk groups (RG), indicating the degree of risk from potential optical radiation hazards to the eye and skin, ranging from the exempt risk group (RG0) to risk group 3 (RG3). According to IEC 62471-5, the highest classification permitted for consumer products is RG2. In this paper, a risk analysis for exposure to the emission of LIP classified as RG2, at distances less than 1 m is provided. The analysis shows that the risk for retinal injury associated with RG2 LIP or conventional projectors at distances less than 1 m can be considered as very low to negligible.