Review Reports

Round 1

Reviewer 1 Report

Thanks for the revisions. I am fine to accept it.

Author Response

Thanks for the reviewing efforts. Revision on the language has been made.

Reviewer 2 Report

In this paper, the authors propose a straightness error compensation system based on thin-film interferometry. The paper is well written and has great academic merit. It builds on a previous publication in which a surface topography measurement system was proposed. The authors disclose this fact in the manuscript, and they have made an effort to describe further results here with additional arguments for its justification. Most of my previous critiques were successfully addressed. I recommend the paper be accepted.

 

Minor remarks:

- Check the grammar and consistency of the new sentences with respect to the existing text.

Author Response

Thanks for the reviewing efforts. Revision on the language has been made, especially for the newly added portion.

Reviewer 3 Report

This revised version well considered the reviewer's concern and I would like to recommend this as accepted in Photonics.

Author Response

Thanks for the reviewing efforts. Revision on the language has been made.

Reviewer 4 Report

Authors addressed most flaws found in previous version of the paper. Although it does not present any relevant advance to the state of the art in the field, it is an implementation that may be useful. Therefore I consider that the paper may be accepted for publication in present form.

Author Response

Thanks for the comments. Revision on the language has been made.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

1, I am not able to figure out Eq. (2). Please elaborate it.

2, Please explain where and how your fringe image is formed.

3, The parameters in Eqs. (12-14) should be defined/explained, although you cited a book.

4, In Eq. (15) and (16), instead of L/T, I think it should be L/T*2*pi.

5, you may turn over the optical flat by 180 degree and measure it again, and check the results. I saw a big deviation at 10mm and not sure what is the cause.

6, I feel the title should be changed to a xxx system "for optical flat", as this system can only be used for optical flat.

Reviewer 2 Report

General remarks:

In this paper, the authors propose a straightness measurement system based on thin-film interferometry. The paper is well written and succinctly described. It builds on a previous publication in which a surface topography measurement system was proposed. The authors disclose this fact in the manuscript. However, they described the principle and most calibration results in the prior publication. In this manuscript, simulation results were included, although further simulation details would be of interest to readers given that the principle has already been published.

1. My main criticism is that given that this paper is expanding on a positioning system described in a previous publication, the current paper should strive to discuss the design and implementation decisions for ensuring reproducibility. 

2. You discuss that the systematic error caused by the two optical elements' imperfection may reach up to 0.11 um. How does this figure compare to the reported measurement deviation between the film interferometer and the confocal sensor of 0.1 um?

Minor remarks:

- Most plots would reveal better the experimental nature of the data if they were plotted as scatter points instead of continuous lines (unless for simulation results).
- Table 3. Report standard deviation of c and how it influences the measurement error with respect to the other errors.

Reviewer 3 Report

This manuscript describes a technique to measure straightness using the interference generated the gap between the prism and an optical flat. It is very similar to Fabry-Perot interferometer, and I don't think it is 'film interference module.'

Unfortunately, I cannot recommend this mansucript as accepted in this journal because of the following reasons.

(1) In Fig. 1, the mathematical modeling was not corrrect becuase the optical flat can be tilted. That's why more rigorous modeling should be considered even though precise stage is used in the experiment and this tilt can be ignored.

(2) The tilt effect was described in the manuscript and it wasignored in the experiment because of using a precise stage. However, the interference fringe variations caused by the distance and the tilt are theoretically coupled, and they cannot be separated in this method without any additional techniques. In this manuscript, the distance was albe to be measured because the tilt was very small but this is not enough for the completeness of the technique.

(3) The typical way to measure straightness is using a laser interferometer. I cannot find out the advantage of the proposed system compared to this.

(4) English experssion should be carefully reviewed because lots of errors appeared in this manuscript.

 

Reviewer 4 Report

Authors report on an important subject in different fields of metrology and most frequently when mechanical scanning is involved.  The careful control and characterization of the straightness of linear positionning systems is required in a large number of situations both at science and technology research and at the industry. For many year the problem was sucessfully addressed in different ways including by interferometry in different approaches including the one the authors employed in their work: "film interference". The literature mentionned in the paper is rather limited at all levels: methods and systems for straightness measurement; interferometry; wedge air interferometry; or even image processing and fring processing and phase detection. A quick bibliographic search will easily allow authors to conclude that their approach is not new. Inspite the method/system assembled can be effective in the application it was assembled for, this basic, yet sound, work  brings no contribuition to the improvement of the current knowledge of this subject and therefore it should not be accepted for publication in a scientific journal with the quality standards of Photonics