The Structure Research and Design for Beam Steering and Adjustment in Golay3 Sparse-Aperture Imaging System

Round 1

Reviewer 1 Report

Although fairly technical in its nature, this work consist of an interesting report on the design of an innovative Golay3 sparse-aperture system for practical engineering applications. The reported methodologies are undoubtedly novel and represent an improvement with respect to the state of the art. The adopted procedures are sound and clearly described. Undoubtedly experimental data reporting on the performance of such an experimental system in relevant practical applications would have greatly improved the impact and significance of the work, but it is assume that this goes beyond the scope of the work. The English form is satisfactory and suitable for publication.

I only have minor comments on the following points:
- the numerical calculation methods are not clearly introduced: the manuscript would really benefit from a more systematic description of adopted numerical methods, possibly in a dedicated (sub)section;
- the Conclusions section would benefit from more insightful perspectives on key aspects in the applicability of this system to address substantial (and currently sub-optimally addressed) practical applications; the authors are encouraged to provide this level of insight, possibly in a quantitatively detailed approach, rather than with generic mentions to application fields.

Furthermore, several figures require editing:
- the 3D models in figs. 6a and 7a would benefit from a readable scale bar; the interpretation of the color bar in fig. 7a is not very clear: in which physical units are the reported numerical values?
- figs. 8, 10, 11, 13, 14 require scale bars, to to the best of the reviewer's understanding;
- figs. 15 requires a scale bar, to to the best of the reviewer's understanding; furthermore, the color scale is basically unreadable;
- the captions of figs. 9, 12 and 15 are too synthetic: the authors should provide some more details to guide the viewer in their visual interpretation;
- Fig. 16b seems to need a scale bar, to the best of the reviewer's understanding;
- figs. 17a-b seem simply wrong, as they are identical to figs. 16a-b, and the caption does not seem to match.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This is a review of the manuscript entitled “The Structure Research and Design for Beam Steering and Adjustment in Golay3 Sparse-aperture Imaging System” by J. Qian, X. Wu, H. Liu, X. Hua, Y. Tao and R. Zhang submitted to the journal of Applied Sciences. In the manuscript the authors analyze a Golay3 imaging system in terms of piston displacement and mirror tilt error. Rudimentary mechanical resonance analysis of the fast scanning mirror structure is also performed. The experimental device is tested using a point source. The description of the device is not sufficiently complete to evaluate the quality of the numerical analysis. Furthermore, the experimental characterization of a point source is not really sufficient measurement to vindicate the experimental analysis. The manuscript needs more than just major revisions. Consequently, I recommend that it be rejected.

 

I have the following major recommendations to strengthen the manuscript:

1. It seems as though the Golay-3 system in this manuscript was not an existing system, but designed and built in conjunction with the analysis. If this is so, the paper should include a complete description of experimental system. This should include things like aperture size, mirror parameters, etc. as well as intended performance specifications, and any other relevant parameters. It would also be informative if the intended application was defined, as the design could be compared to alternative competing designs in the same space.
2. Details should be included about how the simulations were performed. If simulation software was used it should be stated, as well as the enough information for the reviewers to completely verify the accuracy of the simulations independently.
3. The vibration analysis should also check that harmonics of the piezo electric device will not excite any mechanical modes of the FSM structure as well.
4. Regarding experimental verification of the analysis, you should include more than just a point source measurement. You should include images of the calibration test pattern before/after calibration (and possibly some intermediate stages).
5. None of the images have scale bars. This is a grave omission.
6. Figs. 16(b) and 17(b) look identical.
7. The legends of Fig. 15 are too small to be legible.
8. There should be some estimation or measurement of how long it takes the calibration does drift. How often will recalibration be necessary?

 

I have the following minor recommendations to strengthen the manuscript:

1. The authors should define the FSM acronym prior to using it in the caption of Figure 1.
2. You don’t ever explicitly define the “common phase error.” You might point out explicitly that the exponential in Eq. (3) is the “common phase error.”

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The article presents a strategy to solve the alignment issue of sparse-aperture optical telescope. Indeed, these kind of system are composed by several (3 in this case) separated telescopes, and their signals must be combined taking care of both amplitude and phase alignment. The authors propose a compact design of a beam steering system, conducting both simulations and experimental verifications.

My comments section by section, follow:

Section 1

The introduction is well done; however, it is not clear to me what is the originality in the idea presented in the article. Is it the first time a steering system has been used for sparse aperture telescopes? Please explain more clearly the novelty of the article.

Section 2

The math is correct but some of the equations are not clearly explained. Please add the description of all the letters and operators.

At line 90 the PSF is defined. However, I would suggest the alternative definition which links the PFS and the pupil.

Section 3

This section explains the strategy adopted for the phase correction. However, some improvements should be considered, especially in the English. Moreover, I would avoid a deep description of the rough alignment through screws control (lines 138-145) since it is not so relevant; same comment is valid for lines 152-161. A brief description would be better.

Section 4

Here there are the main problems.

Figure 15 is not clear. How do the authors obtain the images? Where are located the sub-apertures? Are these interferometric measures? Moreover, the colorbars are not readable at all.

The second concern is about figures 16 and 17. They are the same figure. On top of this, the most important figures, that would have present the final results, is not shown.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

My concerns were adequately addressed. I recommend the manuscript for publication.

As a minor note, the caption of Fig. 7 states that it has a p = 0 but there is none in the image. This should be simple to fix.