Efficient Depth Measurement for Live Control of Laser Drilling Process with Optical Coherence Tomography

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this paper, optical coherent tomography (OCT) imaging processing is used for the study of live control laser drilling. Optical coherent tomography has the ability to acquire raw interferograms in situ at high rates (>80 kHz), but depth extraction is slow (<0.5 kHz) due to the heavy fast Fourier transform (FFT) involved. To solve this problem, the authors propose an effective depth tracking algorithm to save the FFT. It is proved experimentally that the new depth tracking algorithm can increase the measurement rate to about 3khz with sub-pixel level tracking accuracy. The paper is somewhat innovative. But I have a few questions here that need to be answered by the authors.

1. In the Introduction, the authors mention that "In this case, laser micro drilling offers significant advantages over other machining processes, namely high throughput, small heat affected zone (HAZ), a wide variety of materials that can be machined, contactless machining, and small beam diameters in the micrometer range". Is there a prerequisite for this statement? For example, you mention "small heat affected zone (HAZ)" and as far as I know the thermal effect of long pulsed lasers is very large and not all types of lasers are suitable for micro machining.

2.In the last paragraph of the introduction, “this study implemented an in situ real-time closed-loop control on the hole depth of the laser drilling process by coupling a variant of the biological OCT system into a laser processing head for acquiring real-time interferogram and expediting the inline depth extracting processing via an efficient tracking algorithm and a dedicated FPGA for a fast feedback control”. There are about 57 words total in this one sentence, are you sure the reader will understand what you are trying to say?

3. There are some latest papers, https://doi.org/10.1016/j.optlastec.2023.109164, https://doi.org/10.1016/j.optlastec.2022.108209, https://doi.org/10.1364/OL.383207, https://pubs.acs.org/10.1021/acsami.3c04170, may suitable for the discussion of the paper.

4. In this paper, the author does not inform the reader about the parameters of the laser used for perforation processing, such as the laser type, as well as the laser parameters, such as the pulse energy, repetition rate, and pulse width, etc.

5. In the process of real-time tracking and measurement of hole depth, if there is a lateral melt blocking the ablation hole, or because of the melt sputtering blocking the detection light, will it affect the tracking of the hole depth, how to avoid this problem in the tracking algorithm, and how do the authors consider it.

6. The language in the paper needs to be polished, as many parts are difficult for the reader to understand and need to be improved.

Comments on the Quality of English Language

Minor editing of English language required.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript is well documented. It needs minor corrections.

-The abstract needs to be modified to present some results.

-Literature gap should be well directed; add some recent papers "doi.org/10.1007/s00170-023-12525-4" could be helpful.

-Scope of the study and addressing the research need to be presented.

-Is there any other algorithm that can be helpful for future studies?

-Please provide the sensitivity analysis for the path track.

-Can this study also have the scope of using an inline thermal camera or pyrometer for the system.

 

 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The author needed to make some changes to the comment2 response. First of all, the author used a CMOS array of 2048, but in reply why AScan contains 1000 pixels. Secondly, the detection depth of the system should also consider the influence of the focal depth of the focusing lens, which is the result of the comprehensive effect of the two, and the author needs to supplement it in the paper. The author's answers to other questions are acceptable to us.

Comments on the Quality of English Language

English can be improved

Author Response

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Author Response File: Author Response.pdf