An annular beam provides a new laser drilling mechanism, which we refer to as optical trepanning. A refractive axicon system has been designed to transform an input Gaussian laser beam into a collimated annular beam. The diffractive effects of the axicon system and a convex lens focusing the collimated annular beam have been studied using the Fresnel diffraction integral. The theoretical diffraction patterns are compared with the patterns measured with a laser-beam analyzer. The results show that the refractive axicon system can produce Gaussian-like annular beams with the capability of easily adjusting the size of the annular beam.
Percussion drilling and trepanning are two laser drilling methods. Circular laser spots are generally used in conventional
laser drilling. Annular laser beams provide a new laser drilling mechanism. When an annular beam is focused on the
workpiece surface, the material around the annulus laser spot is heated, melted, vaporized and removed, leading to the
formation of a hole. This process, which we refer to as optical trepanning, does not involve any rotating optics or rotating
workpiece. Based on the ray tracing technique, an optical lens system using axicon lenses has been designed to transform
a Gaussian circular laser beam into an annular laser beam. Both theoretical and experimental results of irradiances of the
annular beam along the optical system were analyzed. Optical trepanning experiments were conducted on stainless Steel-
316. Some geometrical and metallurgical characteristics during optical trepanning were investigated.
Laser drilling is very important in many industries such as automotive, aerospace, electronics, and materials processing. It can be used to produce critical components with novel hole geometry for advanced systems. Percussion drilling and trepanning are two laser drilling methods. In the conventional trepanning method, a laser beam is scanned along a circular or spiral orbit to remove material to achieve a desired hole shape. These orbits generally trace a circular path at the inner wall of the holes. This suggests that an annular beam can be used to accomplish trepanning, a technique we refer to as optical trepanning. The ray-tracing technique of geometrical optics is employed in this paper to design the necessary optics to transform a Gaussian laser beam into an annular beam of different intensity profiles. Such profiles include uniform intensity within the annulus, full Gaussian with maximum intensity, and half Gaussian with maximum intensities at the inner and outer surfaces of the annulus.
Optical trepanning is a new laser drilling method using an annular beam. The annular beams allow numerous irradiance profiles to supply laser energy to the workpiece and thus provide more flexibility in affecting the hole quality than a traditional circular laser beam. The refractive axicon system has been designed to generating a collimated annular beam. In this article, calculations of intensity distributions produced by this refractive system are made by evaluating the Kirchhoff-Fresnel diffraction. It is shown that the refractive system is able to transform a Gaussian beam into a full
Gaussian annular beam. The base angle of the axicon lens, input laser beam diameter and intensity profiles are found to be important factors for the axcion refractive system. Their effects on the annular beam profiles are analyzed based on the numerical solutions of the diffraction patterns.
An annular beam provides a new laser drilling mechanism, that we refer to as "optical trepanning". Based on ray tracing techniques, a refractive axicon system has been designed to transform an input Gaussian laser beam into an annular beam with an appropriate irradiance profile. The properties of the resulting annular beam are investigated in this paper. The diffraction patterns were measured, showing that a collimated annular beam can be obtained using a refractive axicon system. However, due to spherical aberration effects, the focused annular beams possess altered irradiance profiles with different focusing lenses. The effects of spherical aberration on the focused annular beam are also investigated.
Laser drilling is very important in many industries such as automotive, aerospace, electronics and materials processing. It can be used to produce critical components with novel hole geometry for advanced systems. Percussion drilling and trepanning are two laser drilling methods. In the conventional trepanning method, a laser beam in scanned along a circular or spiral orbit to remove material to achieve a desired hole shape. These orbits generally trace a circular path at the inner wall of the holes. This suggests that an annular beam can be used to accomplish trepanning, which we referred to as optical trepanning. The ray tracing technique of geometrical optics will be employed in this paper to design the necessary optics to transform a Gaussian laser beam into an annular beam of different intensity profiles. Such profiles include half Gaussian with maximum intensities at the inner and outer surfaces of the annulus, respectively, and full Gaussian with maximum intensity within the annulus.
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