Online seminars series - Day 1: Advanced Laser Welding, Optical super-resolved microscopy
OpTecBB online seminar in cooperation with Photonics Israel
16:00-17:00 UTC +3
Optical super-resolved microscopy Prof Steve Lipson (Emeritus Professor of Physics at Technion)
Abstract: According to Ernst Abbe’s theory of microscope resolution from 1873, the resolution limit of an image created using incoherent light is λ⁄2"NA" , where the numerical aperture NA is n sinα, n being the refractive index of the medium surrounding the object and α the semi-angle of the imaging lens at its focal point. This leads to a limitation of λ⁄2n for a wide-angle lens. Since Toraldo di Francia’s work in 1952, many efforts have been made to improve on this limit, which culminated in three scientists’ receiving a Nobel Prize in 2014 for techniques using fluorescent labelling. I will discuss the basic physics underlying these techniques and others which have also been developed in the meantime. Today, resolutions more than 50 times better than the Abbe limit have been achieved in the visible spectrum. Super-resolution comes at a price, and the use of information theory allows this to be estimated. I will show that one price is inefficiency in light usage. Another price is a need for pre-knowledge of expected details in the image being investigated, and may include serious limitations of the field of view.
18:30-19:30 UTC +3
Advanced Laser Welding With Dynamic Beam DR Eyal Shekel (Dr. Shekel is the founder and CEO of Civan Advanced Technologies Ltd)
Abstract: Presently a Laser Beam is Dynamic because it is moving from point to point, by mechanical steering a mirror or a mechanical robotic arm. These movements are limited in speed/frequency. Moreover, the energy profile of the beam is fixed throughout the process.A revolutionary technological improvement developed at CIVAN ADVANCED TECHNOLOGIES, in Jerusalem, allows now to achieve changes of beam energy profile at will, with MHz frequency and at unlimited high power levels. The beam thus generated can deliver, for example, a highly concentrated oscillating spot associated with pre- or post-heating areas of sizes at will, to optimize the heat input for the specific welding, cutting or heat-treatment application. Unlimited geometrical energy profile shapes can be generated in real time enabling unprecedented processes optimization opportunities.In Laser Beam Melting 3D printers, the energy distribution of this technology can eliminate the power limitation in present machines of 400-700 W by maintaining concomitantly a large number of melt pools, in similarity to the Electron Beam Melting and also raising the powder bed temperature highly enough to reduce the high stresses developing in this process.In Butt or Lap Welding the deep melt pool traps gas bubbles because high turbulence in the molten metal. A high frequency oscillation imposed to a high energy spot within the beam reduces the turbulence and the associated porosity. A half-moon energy profile preceding the high energy spot will be beneficial in processing high-heat-conducive metals. A similar heat profile, at the trail side will reduce the cracking of welds of sensitive alloys.Cutting and drilling will benefit not only from the beam energy profile customization but also from the long focal length possible, because of the high depth of view, keeping the same focus within 4 mm depth. Surface treatment of materials, such as steel hardening requires a spreading of the energy, regularly done by de-focusing a beam