Stainless steel is known as a corrosion-resistant material and this superior ability could be a desired property for a pinhole aperture operated in a corrosive environment and thereby be able to maintain both smoothness and a perfect circular shape in order to achieve precise beam alignment. Laser drilling has widely been preferred when placing holes into stainless steel due to its non-contact method of machining. In addition, this method is capable of performing delicate machining while inducing relatively low amounts of heat in the affected zone in comparison with other traditional machining techniques such as punching. Laser drilling is also beneficial for specimens having a thin thickness since manufacturing tolerances are minimal in this case. In this paper, we have attempted to produce holes of various diameters in 10 m thick stainless steel foil by using a femtosecond laser trepanned method. We have demonstrated these to be of perfect circular shape and adhering to low tolerance manufacturing by adjusting the beam parameters. In addition, holes with various diameters have been made by employing previously selected machining parameters and the viability of pinhole apertures fabricated by laser drilling have been evaluated.

목 적: 펨토초레이저(Fentosecond laser)를 이용한 라식 수술 후 이중경로방식(double-pass technique) 으로 시력의 질을 평가하였다. 방 법: 펨토초레이저를 이용한 라식 수술을 받은 중등도 및 고도 근시안(평균 등가구면굴절력: -3.93 ± 1.48 D) 43명(85 안, 평균연령: 26.35 ± 6.86세)을 대상으로 하였다. 시력의 질은 수술 전과 수술 1주일 및 1개월 후에 Optical Quality Analysis System(OQAS) 장비를 이용하였고, modulation transfer function(MTF), Strehl ratio, objective scattering index(OSI) 및 객관적 시력(OQAS values, OVs)을 측 정하여 평가하였다. 결 과: 수술 1개월 후 MTF cutoff 값, Strehl ratio, OSI, OV100%, OV20% 및 OV9% 는 각각 41.67 ± 9.99 cycles/degree, 0.24 ± 0.06, 0.45 ± 0.19, 1.41 ± 0.28, 1.06 ± 0.26, 0.66 ± 0.18로 이 값들은 수술 전과 유의한 차이가 없었다(MTF p=0.23, Strehl ratio p=0.19, OSI p=0.19). 또한 객관적 시력 OV100%, OV20%, OV9% 도 모두 수술 전과 비교하여 유의한 차이를 보이지 않았다(p=0.95, p=0.10, p=0.10). 결 론: 펨토초레이저 라식 1개월 후 시력의 질은 수술 전 안경렌즈로 교정한 값과 차이를 보이지 않아 좋 은 시력의 질을 제공하는 것으로 생각된다.

In this paper, we describe experiment results using a vibration assisted hybrid femtosecond laser (λ:795 nm) ultra- precision machining system. The hybrid system we have developed is possible that optical focal point of the femtosec- ond laser constantly and frequently within the range of PZT(piezoactuator) vibrator working distance. Using the hybrid system, We have experimented on brass and studied about differences of result of hole aspect ratio compare to general experiment setup of femtosecond laser system. Aspect ratio of a micro hole on brass is increased as 54% with 100 Hz vibration frequency and surface roughness of the side wall also improved compare to non-vibration.