Design for Ultrafast Raster Photography with a Large Amount of Spatio-Temporal Information
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear Authors,
I studied your paper and found, that it requires a revision.
1. You discussed some equations, but do not show any results of the operation of the discussed ultrafast raster photographic camera. I believe, that in a good paper these results should be provided. Please show the images of any dynamic event, where the proposed equations ensures the better resolution in comparison with the case, where they are not taken into account. This is a main problem in a current manuscript.
2. The implementation of the frequency-spatial mapping is not discussed properly in the text of the manuscript. You wrote, that this is a "4f optical system and a diffraction grating placed in the Fourier plane". I recommend to include the optical scheme, to show unambiguously, how the light propagates in this system.
3. The related question to comment #2, "how the time direction is defined?" also should be clarified. Please discuss it in the text, and make necessary corrections on the figure 2.
4. The discussion of the related works in the introduction is not sufficient, and can be further improved. Please consider the papers below as references to support specific phrases or further enhance the discussion:
- "...high-speed framing cameras" [https://doi.org/10.1364/OE.23.033396] (exposure time 300 ns with pulses ~20 ps source);
- "...imaging based on pump-probe technology" [https://dx.doi.org/10.1063/1.4981899], [https://doi.org/10.1364/OL.43.003481], [https://doi.org/10.3390/jimaging8030074];
-"... space division [19-21]" [https://doi.org/10.1364/OE.472770];
- ".. angle division [22-24]" [https://doi.org/10.1364/JOSAA.480910], [https://doi.org/10.1364/OL.448106];
- "..wavelength division [25-29]" [https://doi.org/10.1038/s41377-022-00759-y];
-"..spatial frequency division [30,31]" [https://doi.org/10.1364/OL.44.004885];
- spatial multiplexing encoding [https://doi.org/10.1364/OL.42.002082] (in addition to "space [19-21], angle [22-24], wavelength [25-29], spatial frequency [30,31], or polarization [32] division"). Please note, that you also can use only one word "division" there, as shown in this example.
5. Please discuss, will proposed technique discriminate spectral information and can in be used to study the objects with spectral features?
6. Refs [7] and [17] are duplicated. Please correct and check the the reference list for the other problems.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors present their work to optimize an Ultrafast Raster Imaging (URI) system to measure spatiotemporal ultrashort laser pulse information, based on Nyquist sampling theorem and frequency-time mapping method, on a single shot. Compared to the existing URI systems, an optimized URI system designed based on the maximum amount of information exhibits the improvement of nearly 1 order of magnitude in the amount of spatiotemporal information, and more than twofold in spatial resolution. Overall, this paper is well written and technically sound. I have a few minor points the authors should address, before its acceptance.
1. On Page 1, when reviewing ultrafast imaging techniques, the authors should recognize the below relevant work. Here I give the group and example papers:
• CNRS, France
Jolly, Spencer W., Olivier Gobert, and Fabien Quéré. "Spatio-temporal characterization of ultrashort laser beams: a tutorial." Journal of Optics 22.10 (2020): 103501.
• Georgia Tech, USA
Xu, Yingming, Youjian Yi, Ping Zhu, Xingcheng Pan, Qiang Zhang, Liangze Pan, Fucai Ding et al. "Simple single-shot complete spatiotemporal intensity and phase measurement of an arbitrary ultrashort pulse using coherent modulation imaging." Optics Letters 47, no. 21 (2022): 5664-5667.
• Shandong Normal University, China
Huang, Hong-Yi, et al. "Single-shot ultrafast sequential holographic imaging with high temporal resolution and a large field of view." Optics Letters 44.19 (2019): 4885-4888.
• Kyoto Institute of Technology, Japan
Inoue, Tomoyoshi, et al. "Spatiotemporal observations of light propagation in multiple polarization states." Optics Letters 44.8 (2019): 2069-2072.
2. On Page 2, “In our previous work, the UIR system [32] has gotten 12-frame images”, “UIR” is a typo, and it should be “URI”.
3. On Page 2 and Page 4, “The modified temporal qualify factor g^(2/3) can be determined by the ratio of the frame interval time τf to the effective exposure time τ”. “In order to avoid information blurring caused by overlapping between the adjacent frames, the optimization condition is set to g^(2/3)=1.” “Here, to ensure the optimal temporal degree of freedom (DOF) and avoid information blurring caused by overlapping between the adjacent frames, the modification factor g ^(2/3) is set to 1.”
Could the authors explain on this? Setting g^(2/3)=1, or equivalently, g= 1, the frame interval time τf will be equal to the effective exposure time τ. What if g >1, when the frame interval time τf is larger than the effective exposure time τ, will the information be larger?
4. On Page 4, “the size of sampling point can be adjusted by the entrance pupil of the objective”, should be “The”.
5. Could the authors elaborate on the choice of the time window T? What can be practically limiting or affecting its operation range, other than the time period of ultrafast events?
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsIn this paper the authors reported the design of an ultrafast raster photography. The authors have already published several papers on this topic. What is new here is that the authors presented a formula which can be used to optimise the design of the ultrafast imaging system with a large amount of spatio-temporal information. The authors claim the new design “exhibits an improvement of nearly 1 order of magnitude in the amount of spatio-temporal information, and more than twofold in spatial resolution”, as compared with their previous work (presumably [33]-- https://doi.org/10.1364/OE.434042).
There is no experimental validation presented in this manuscript. For this reason and also for the completeness and rigour of the reported work, I would strongly suggest the authors to include experimental validation in this paper. I noted that the group has already had several publications on this topic including experimental work (for example, https://doi.org/10.1364/OE.434042) thus it should not be too difficult to add some preliminary experimental results validating the resultant improvement of the formulation/calculation work reported here. Alternatively the authors could use the published results by them or others (e.g., to carry out the calculation using the parameters therein) to support the conclusion.
In addition, the authors mentioned that “reducing the size of sampling point of raster image is the key to improving the spatial resolution and frame rate.” The authors may wish to discussion its experimental implications.
Minor typos:
Lines 187-188: In addition, we can get a higher spatial resolution will be obtained by a shorter central wavelength of the probe laser pulse.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsIt is worth adding to the annotation that the system was developed when registering active illumination with femtosecond illumination
At the very beginning of the article, it is necessary to clarify what is meant by the large amount of information, it differs from the standard concept of the amount of information (in fact, the number of zeros and ones), the article refers to the amount of information per unit of time (i.e., an estimate of the speed of registration of reading and transmission of information).
The direction of the vector K is not clear in the figure 2. It follows from the figure that the value L is indicated along the vector k.
In addition, it follows from the figure that the value L is equal to the side AE (see file) of the triangle ABC (if this is the case, then it is unclear how the formula (2) turned out) .
It is not clear from the text of the article and Figure 2 what the multicolored squares mean - either they are bitmaps of the same point of the object in different time intervals (lines 103 - 104) or the decomposition into a spectrum (in wavelengths) of one point of the image (lines 170-171).
From the text of the article, it is not clear why the authors chose only three sizes (line 123)
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe serious experimental results still omitted. Without ther the impact of the paper is weak. But paper can be published, since the authors agrued that it is important and meaningful to establish the theoretical foundation for the URI system with a large amount of information, as a guidance for future experimental research.
Reviewer 3 Report
Comments and Suggestions for AuthorsIt would be better to have experimental validation but I understand that the authors are having technical issues to carry out experiments in the desired timescale. I therefore have no objection to its publication in its present form.
