Analysis and Optical System Design of the Lenslet-Array Integral Field Spectrometer

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The space detection in lunar orbit puts forward high requirements for the fast identification, efficient tracking and low light detection ability of spectral cameras. The traditional spectral cameras are limited by slit and push-broom imaging, with low luminous flux and long detection period, which are difficult to meet the application requirements. This manuscript puts forward a lenslets array integral field spectrometer without slit and scanning structure, which has the ability to measure the snapshot spectrum of rapidly changing targets. This work analysis the influence of the telecentricity and the primary aberration of the pre-imaging system, and the initial structural calculation programs to obtain the optimal optical system parameters for micro-pupil distribution is developed. The optical design off-axis telescope and spectroscopic system are completed. This work relatively complete, and still needs some improvements. The following suggestions are for the authors’ reference.

1) Fig.5 to Fig.8 illustrate the influence of the pre-imaging system primary aberration on the micro-pupil distribution, but no corresponding quantitative relationship with the final imaging spectral results is established. It is suggested that the snapshot spectral detection principle of the integral field spectrometer be described in detail in Fig.1, and the error transfer relationship between the optical aberration and the spectrogram could be established. The aberration tolerance has more theoretical significance for optical design and processing. 

2) Fig.12 shows the final optical layout of the spectroscopic system, the Fig.14 shows the final optical layout of the field integrated spectral system. But what puzzles me is that the spectroscopic system in Fig.14 is obviously different from that in Fig.12, and there is a big difference. Are the spectroscopic systems in the two pictures the same? Is it caused by the optimization after the whole system is matched? I hope the authors can give reasonable explanations. Besides, I don't see any explanation about Fig.14.

3) The Fig.9 shows the ray tracing result with a single field of view of the off-axis system, therefore it will be more convincing whether it can give a ray tracing result with a full field of view.

Comments on the Quality of English Language

There are some spelling mistakes in the manuscript. I hope authors will check the spelling of the whole text further, such as, in line 99, “initiaIstructure” should be spelled as “initial structure”, in line 185, “StructuraIparameters” should be spelled as “Structural parameters”, in Table1, “Obiect surface” should be spelled as “Object surface”.

Author Response

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Reviewer 2 Report

Comments and Suggestions for Authors

The authors describe a snapshot imaging spectrometer utilizing a lenslet array for rapid image acquisition.  Much attention is given to the pre-design to determine the correct optical requirements of the fore optics design as well as the lenslet element design.  The concept of using a lenslet array to disect the image in a spectrometer is not new but the authors provide detailed information that may be of interest to others interested in constructing a similar device.  The paper needs some editing and the following comments must be addressed.

Line 67:  I think you mean “post imaging system” referring to Figure 1.  There are some disagreements between the labels in the figure and your text.  You use the term front imaging system and then label it as pre-imaging system.   Please be consistent.

Lines 138:  how much SA is represented by the simulation in Fig. 6?  Same questions for examples for coma and distortion.  Also, you do not mention the NA or F/# of the lenslets which determines their sensitivity to aberrations.

What is the proposed sag of each lenslet?  You will have to make a master of the array probably through lithography and the amount of etch you can achieve is limited based on material choice so this may be a parameter you must pay attention to depending on your vendor or material choice.

You should reference the pioneering work in IFS mentioned in “Lenslet array tunable snapshot imaging spectrometer (LATIS) for hyperspectral fluorescence microscopy” in Biomedical Optics Express , https://doi.org/10.1364/BOE.8.001950 by G. Courtes (references 27-29 in the paper).

What is the relationship of the NA of each lenslet to the performance of the system, e.g. resolution?

Table 2 is never referred to in the text.

Line 200:  the grating and prism compensate the smile because they have dispersion of opposite signs, i.e., dn/dlambda, of the diffractive and refractive elements ,  the same reason a hybrid lens color corrects.

Figure 12 is not referred to in the text.  It’s a complicated optical design that should be discussed or at least mentioned beyond its description as telecentric.

Figure 14 is not mentioned in the text.

Table 3:  if the units in the table are in microns this must be mentioned in the caption.  Same is true for the units of keystone in Table 4

Line 220:  where was pixel size ever mentioned in the text?  No focal plane array was included in the design details.

Line 235:  Is the smile +/- 1 um or +/- 1 nm?

Comments on the Quality of English Language

The quality of the English language is good and sufficient to convey the meaning of the paper.

Author Response

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Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript analyzes the influence of anterior imaging system's telecentricity on the system, based on geometrical optics theory of micro-pupil. The paper also proposes the requirements for telecentricity of anterior imaging system and develops initial structural calculation programs to obtain the optimal optical system parameters for micro-pupil distribution.

However, the following needs further clarification:

Flow chart - please correct the inputs (p instead of P; ?_n insted of Wn...), also - the question "Logical or not" can not be answered with Yes or No (e.g. Logical? this question can be answered as Yes or No)

eq. 6. 2f of what? it is not explained

table 1. please use the form for writting numbers in the last two columns as e.g.1.2304×10-⁶

In the text is not mentioned the Figure 12 (explaining its purpose), same for fig 14

I suggest that pictures 5 to 8 be combined into one and marked with A to D, because then it would be easier to compare the results

Conclusion- firs sentance is confusing and it is unclear what was analyzed in the end

Also ins confusing that 5 different Foundings are used for this study

Sincerely

Author Response

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Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The new version of the manuscript supplements the content of aberration analysis of optical system according to the opinions, gives the aberration tolerance, provides theoretical guidance for system design, and gives the relevant explanation of optical layout. At present, the manuscript work is more scientific and complete.

Comments on the Quality of English Language

The new English version of the manuscript has corrected the spelling mistakes of words, and it is suggested to further check the grammar to ensure that readers can understand the contents of the manuscript without ambiguity.