Coaxial real-time metrology and gas assisted laser micromachining: process development, stochastic behavior, and feedback control

Webster, Paul J. L.; Leung, Benjamin; Yu, Joe; Anderson, Mitchell D.; Hoult, Tony; Fraser, James M.

doi:10.1117/12.842409

Cited by 12 publications

(15 citation statements)

References 10 publications

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“…ICI does not require assumptions about repeatability of the ablation process, especially in a heterogeneous material like cancellous bone. In addition, the local ablation rate can be easily extracted from M‐mode images by using simple interface‐detection algorithms 32. Applications such as craniotomy and vertebral body osteotomy typically require cutting through a mixture of cortical and cancellous bone, which signifies the importance of ablation depth monitoring without a priori knowledge.…”

Section: Discussionmentioning

confidence: 99%

Real‐time guidance of thermal and ultrashort pulsed laser ablation in hard tissue using inline coherent imaging

et al. 2012

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Background and Objective: During tissue ablation, laser light can be delivered with high precision in the transverse dimensions but final incision depth can be difficult to control. We monitor incision depth as it progresses, providing feedback to ensure that material removal occurs within a localized target volume, reducing the possibility of undesirable damage to tissues below the incision. Materials and Methods: Ex vivo cortical and cancellous bone was ablated using pulsed lasers with center wavelengths of 1,064 and 1,070 nm, while being imaged in real-time using inline coherent imaging (ICI) at rates of up to 300 kHz and axial resolution of $6 mm. With realtime feedback, laser exposure was terminated before perforating into natural inclusions of the cancellous bone and verified by brightfield microscopy of the crater crosssections accessed via side-polishing.Results: ICI provides direct information about incision penetration even in the presence of intense backscatter from the pulsed laser and plasma emissions. In this study, ICI is able to anticipate structures 176 AE 8 mm below the ablation front with signal intensity 9 AE 2 dB above the noise floor. As a result, the operator is able to terminate exposure of the laser sparing a 50 mm thick layer of bone between the bottom of the incision to a natural inclusion in the cancellous bone. Versatility of the ICI system was demonstrated over a wide range of light-tissue interactions from thermal regime to direct solid-plasma transition. Conclusions: ICI can be used as non-contact real-time feedback to monitor the depth of an incision created by laser ablation, especially in heterogeneous tissue where ablation rate is less predictable. Furthermore, ICI can image below the ablation front making it possible to stop laser exposure to limit unintentional damage to subsurface structures such as blood vessels or nervous tissue.

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Section: Discussionmentioning

confidence: 99%

Real‐time guidance of thermal and ultrashort pulsed laser ablation in hard tissue using inline coherent imaging

et al. 2012

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“…In this work, the choice of broadband SLD and spectrometer design enables an axial resolution of 20 µm and a single sided field of view of 4 mm. Raw data from the spectrometer are processed by: background spectrum subtraction, Gaussian spectral shaping, linear interpolation, and fast Fourier transform (FFT) . For a specific location of the sample, two final outputs are available: (1) the sample reflectivity profile (known as an axial‐line or “A‐line”), which shows backscattered intensity as a function of depth, including backscattering from sidewalls, ablation front and subsurface features and (2) sample surface tracking, through which the depth of the ablation front is extracted from the sample reflectivity profile.…”

Section: Methodsmentioning

confidence: 99%

Automated 3D bone ablation with 1,070 nm ytterbium‐doped fiber laser enabled by inline coherent imaging

2015

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“…Figure 1 shows two widely reported schemes of dual-wavelength beam combination that has been used for ablation process monitoring and control using OCT. Figure 1(a) shows the most prevalent beam combination method, which uses a dichroic element to guide both free-space beam paths into a single set of objective optics. [13][14][15] Figure 1(b) shows a method that maintains a single fiber output path for both beams by combining the ablation source (in this case, a fiber laser) directly into the sample arm of the OCT system, reducing the amount of bulk optic elements at or near the output. 12 Both methods can be easily used to design an optical payload for robot-guided ablation, as shown in Fig.…”

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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Coaxial real-time metrology and gas assisted laser micromachining: process development, stochastic behavior, and feedback control

Cited by 12 publications

References 10 publications

Real‐time guidance of thermal and ultrashort pulsed laser ablation in hard tissue using inline coherent imaging

Real‐time guidance of thermal and ultrashort pulsed laser ablation in hard tissue using inline coherent imaging

Automated 3D bone ablation with 1,070 nm ytterbium‐doped fiber laser enabled by inline coherent imaging

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

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