Design and Performance of a Focus-Detection System for Use in Laser Micromachining

Cao, Binh Xuan; Bae, Munju; Sohn, Hosik; Choi, Jiyeon; Kim, YoungDuk; Kim, Jeng-o

doi:10.3390/mi7010002

Cited by 21 publications

(3 citation statements)

References 14 publications

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“…Various optical sensing methods have been reported to measure workpiece distance along the optical axis in real-time. Techniques involving monitoring of the laser spot diameter using image sensors have also been developed [161,162], but may not perform well on irregular surfaces, defocusing direction may remain ambiguous, and marking the specimen by firing the machine beam in order to make a spot measurement may cause unwanted damage to the target. Hand et al developed a technique that redirected a fraction of the process-generated light into a separate optical path for analysis of the chromatic aberrations to determine focal error [163].…”

Section: Introductionmentioning

confidence: 99%

Penscriptive Depth-Controlled Robotic Laser Osteotomy

Jivraj¹

2021

Preprint

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Bone cutting in surgery is currently done using un-intelligent tools that depend on the proficiency of the surgeon to prevent damage to underlying critical structures. As one can imagine, damage isn’t always prevented. Iatrogenic damage to dura and sub-dural neural structures during osteotomical procedures such as a craniotomy can result in increased patient morbidity. This dissertation proposes the development of a robot-guided laser osteotome (bone cutter) with the use of inline optical coherence tomography (OCT) to precisely control the cutting depth in real-time. The all-fiber system design integrates a high peak-power pulsed Yb-doped fiber laser (1064nm) coupled directly into the sample arm of a swept-source OCT system (λc = 1310nm) with a fourth-order power disparity between the OCT system and fiber laser. Sub-millimeter accuracy was achieved in percussion drilling of phantom and porcine bone. Through the use of optical topographic imaging (OTI), this work presents a novel method for the surgeon to identify arbitrary trajectories for desired cuts. A surgical pencil is used to demarcate cutting trajectories for the robot to follow directly onto the boney surface. OTI imaging combined with a novel algorithm developed through this work allows the penscribed line to be isolated and translated into spatial attitude information for the robot to guide the end effector-mounted laser along. Sub-millimeter trajectory following accuracy was achieved. This work also demonstrates the first use of OCT in continuous, real-time refocusing of the optical end-effector in order to maintain cut quality. The focus of the laser was able to be maintained within the Rayleigh length of the focused Gaussian beam for linear feed rates up to 1mm/s at a 45◦ surface incline. Finally, optimization of bone ablation is explored in this dissertation. The use of graphite as a high-absorption topical chromophore and the use of nitrogen as an assist gas in the form of a coaxial jet are both analyzed to determine how to achieve the highest etch rate in bone. The results in this dissertation show that the topical application of graphite was able to significantly reduce the mean and variance of etching performance; an improvement by at least two orders of magnitude in the time to 0.5mm etch depth is demonstrated. It is also demonstrated that etch rate during ablation can be optimized for coaxial nitrogen flow (30SCFH out of a nozzle with 3mm output diameter); higher and lower flow rates showed slower etch rates. It is hypothesized that a system such as the one developed in this dissertation will increase the precision of bone cutting, decrease the amount of time needed to make cuts into sensitive structures and also address certain issues of unsuccessful uptake of lasers in modern medicine.

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Section: Introductionmentioning

confidence: 99%

Penscriptive Depth-Controlled Robotic Laser Osteotomy

Jivraj¹

2021

Preprint

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“…Various optical sensing methods have been reported to measure workpiece distance along the optical axis in real-time. Techniques involving monitoring of the laser spot diameter using image sensors have also been developed 2,3 but may not perform well on irregular surfaces, defocusing direction may remain ambiguous, and marking the specimen by firing the machine beam in order to make a spot measurement may cause unwanted damage to the target. Hand et al 4 developed a technique that redirected a fraction of the process-generated light into a separate optical path for analysis of the chromatic aberrations to determine focal error.…”

Section: Introductionmentioning

confidence: 99%

Optical coherence tomography for dynamic axial correction of an optical end-effector for robot-guided surgical laser ablation

Jivraj

Chen

Barrows³

et al. 2019

Opt. Eng.

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Robot-guided laser ablation for surgical applications potentially offers many advantages compared to by-hand mechanical tissue cutting. However, given that tissue can be rough and/or uneven, ablation quality can be compromised if the beam waist deviates significantly from the target tissue surface. Therefore, we present a method that uses optical coherence tomography (OCT) for dynamic refocusing of robot-guided surgical laser ablation. A 7-DOF robotic manipulator with an OCT-equipped optical payload was used to simulate robotic guided laser osteotomy. M-mode OCT feedback is used for continuous surface detection to correct for axial deviations along the ablation path due to surface nonuniformity. We were able to show that such a correction scheme could maintain the beam waist within the depth of focus for surface variation as aggressive as 45 deg with feed rates up to 1 mm∕s. Strategies for implementation in surgical and nonsurgical applications are examined.

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“…More importantly, some other studies have already improved the optical setup to explore the focus on a non-planar sample based on diffractive beam samplers [ 12 , 13 ] or the macro/micro dual-drive principle [ 14 ]. Furthermore, many auto-focusing devices have been developed for laser direct writing [ 14 , 15 , 16 ]; laser ablation [ 17 ]; automatic microscopy and measurement [ 18 ]; laser material processing [ 19 ]; two-photon photo-polymerization (TPP)-based micro-fabrication [ 20 ]; and several other applications [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ] in Shack-Hartmann wave-front sensor fabrication [ 21 ], parallel data processing [ 22 ], photonic force microscopy [ 23 ], controllable mirror-lens retrofocus objective [ 24 ], tunable lens focal offset measurement [ 25 ], laser micromachining [ 26 ], remote sensing [ 27 ], automated optical inspection [ 28 ], auto-focusing infinity corrected microscopes [ 29 ], and direct imaging technology [ 30 ] with detailed theoretical models. However, these focus detection systems are complicated, expensive, and inadequate for the mass production of 3D patterns [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ].…”

Section: Introductionmentioning

confidence: 99%

In-Situ Real-Time Focus Detection during Laser Processing Using Double-Hole Masks and Advanced Image Sensor Software

Cao

Hoang

Ahn

et al. 2017

Sensors

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In modern high-intensity ultrafast laser processing, detecting the focal position of the working laser beam, at which the intensity is the highest and the beam diameter is the lowest, and immediately locating the target sample at that point are challenging tasks. A system that allows in-situ real-time focus determination and fabrication using a high-power laser has been in high demand among both engineers and scientists. Conventional techniques require the complicated mathematical theory of wave optics, employing interference as well as diffraction phenomena to detect the focal position; however, these methods are ineffective and expensive for industrial application. Moreover, these techniques could not perform detection and fabrication simultaneously. In this paper, we propose an optical design capable of detecting the focal point and fabricating complex patterns on a planar sample surface simultaneously. In-situ real-time focus detection is performed using a bandpass filter, which only allows for the detection of laser transmission. The technique enables rapid, non-destructive, and precise detection of the focal point. Furthermore, it is sufficiently simple for application in both science and industry for mass production, and it is expected to contribute to the next generation of laser equipment, which can be used to fabricate micro-patterns with high complexity.

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Design and Performance of a Focus-Detection System for Use in Laser Micromachining

Cited by 21 publications

References 14 publications

Penscriptive Depth-Controlled Robotic Laser Osteotomy

Penscriptive Depth-Controlled Robotic Laser Osteotomy

Optical coherence tomography for dynamic axial correction of an optical end-effector for robot-guided surgical laser ablation

In-Situ Real-Time Focus Detection during Laser Processing Using Double-Hole Masks and Advanced Image Sensor Software

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