Design of Wide Angle and Large Aperture Optical System with Inner Focus for Compact System Camera Applications
Round 1
Reviewer 1 Report
Dear authors,
Your work on the ''Design of Very Wide Angle and Large Aperture
Optical System with Inner Focus for Compact System Camera Applications'' is interesting for the optical design community.
Please consider the following remarks to help you improve your paper.
1) In your design approach, you proposed to combine two groups of lenses where one group is part of a design of an ultra wide field-of-view optical system and another group is from a design of large-aperture optical system. Afterwards, the optical system built out of the two different lens groups is optimized to fulfill the required specifications. With only one moving element, the performance of the optimized optical system is not diffraction limited as we see it from the aberration curves given in Figure 9. As the f-number of the optical system is 1.4, the diffraction spot size is about 2 um (for green wavelength), where as the monochromatic aberrations are in the range of 100 um. This is no where close to diffraction limited performance.
That is why more floating/moving lens groups are necessary to achieve a diffraction limited performance if the field-of-view of the optical system is large.
At this stage, it is hard to conclude if the approach is resulting a design which is diffraction limited with only 1 moving element.
It would be interesting to compare the performance of the two patented designs with your optimized system using the aberration curves, MTF and spot diagram analysis methods.
2) Could you include in the paper the spot diagram analysis (including the airy disk size ) of the optimized optical system? It will be then easier to see how worse the system is performing compared to a diffraction limited system
3) Could you also include the MTF as a function of the spatial frequencies (lp/mm ) in the paper?
4)In Figure 11, the MTF graphs are not monotonically decreasing (as ideally expected) as we go to larger image heights. Could you explain why this is so?
Author Response
Revision of “Design of Very Wide Angle and Large Aperture Optical System with Inner Focus for Compact Camera System Applications”
Dear Reviewers:
I would like to thank you for your thorough examination of this manuscript. I have carefully considered all of the comments and strived to address all of the issues raised in this resubmission. In my responses, I first repeat the comments (in black) and provide our detailed responses (in blue). Please note that all of the figure, page, and citation numbers in this document refer to those in the revised manuscript. The updated contents have also been highlighted in yellow in the revised manuscript.
I look forward to hearing from you
Best regards,
Prof. Hojong Choi
Prof. Jae-Myung Ryu
Dear Reviewer1
I really appreciate your efforts and time to review my manuscript, which enabled to improve its quality.
Dear authors,
Your work on the ''Design of Very Wide Angle and Large Aperture Optical System with Inner Focus for Compact System Camera Applications'' is interesting for the optical design community.
Please consider the following remarks to help you improve your paper.
1) In your design approach, you proposed to combine two groups of lenses where one group is part of a design of an ultra wide field-of-view optical system and another group is from a design of large-aperture optical system. Afterwards, the optical system built out of the two different lens groups is optimized to fulfill the required specifications. With only one moving element, the performance of the optimized optical system is not diffraction limited as we see it from the aberration curves given in Figure 9. As the f-number of the optical system is 1.4, the diffraction spot size is about 2 um (for green wavelength), where as the monochromatic aberrations are in the range of 100 um. This is no where close to diffraction limited performance.
That is why more floating/moving lens groups are necessary to achieve a diffraction limited performance if the field-of-view of the optical system is large.
At this stage, it is hard to conclude if the approach is resulting a design which is diffraction limited with only 1 moving element.
It would be interesting to compare the performance of the two patented designs with your optimized system using the aberration curves, MTF and spot diagram analysis methods.
Answer: Unlike ordinary inspection optics, camera optics do not need to increase resolution performance up to the diffraction limit. As you mentioned, the optical system of F / 1.4 has a spot size of 2um, but the pixel size of the digital sensor of the camera body in which this system is used is about 3.5 ~ 4um. (ref. https://cweb.canon.jp/eos/lineup/5ds/feature-highquality.html) In addition, MTF frequencies for optical systems of leading camera companies use 10lp / mm and 30lp / mm. Considering this, there is no optical design with diffraction limit except telephoto lens. In addition, the MTF performance of the optical system according to this paper is similar or slightly higher than that of similar products, so the resolution performance of the optical system is not a problem. Refer to the following link for MTF performance of similar products.
https://imaging.nikon.com/lineup/lens/f-mount/singlefocal/wide/af-s_24mmf_14g/index.htm
https://cweb.canon.jp/ef/lineup/wide/ef24-f14lii/spec.html
2) Could you include in the paper the spot diagram analysis (including the airy disk size) of the optimized optical system? It will be then easier to see how worse the system is performing compared to a diffraction limited system
Answer: As explained in question (1), the camera optical system is rarely designed to the diffraction limit. The highest pixel in a 36x24mm (called full frame) digital sensor is the Sony α7R IV, which is about 61 million pixels. Therefore, the pixel size of this product is 3.76um. This value is larger than the airy disc by the diffraction limit. Again, the camera optics do not need to be designed to the diffraction limit.
3) Could you also include the MTF as a function of the spatial frequencies (lp/mm ) in the paper?
Answer: The MTF graph for each frequency has been added to the text. For reference, the maximum frequency of the MTF is determined by the pixel size of the sensor, which is called the Nyquist frequency. In the case of 61 million pixels, the Nyquist frequency is about 132 lp / mm, so the maximum frequency of the added frequency-specific MTF graph is 135 lp / mm.
4) In Figure 11, the MTF graphs are not monotonically decreasing (as ideally expected) as we go to larger image heights. Could you explain why this is so?
Answer: Since the camera optics do not have to achieve a diffraction limit, the residual aberration is quite large. The MTF decreases because the aberration increases as the image height increases. As shown in the astigmatic field curve in Figure 9, the aberration increases. The characteristics of MTF are also characteristic of camera optical system products.
I really appreciate your useful suggestions, time, and efforts to review my manuscript, which enabled to improve its quality.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The author report on the design procedure of a very wide angle and large aperture optical system. They find that the inner focus system of this system can be applied for compact system cameras by moving a single lens. The method that design new lens module by modifying the old lens modules in patents is often seen in imaging optical design, however, that lacks the explanation of the necessary reasons for modifying the two lens modules in this article. Moreover, many similar designs had been widely developed in many compact camera systems. Hence, I have not find obvious innovative points or breakthroughs in this article. In addition, the study in this article just performs subsequent design by the commercial optical software, but doesn’t provide the discussions of the exact experimental results to verify the design results. Hence, based on the policy that provides the experimental results as detail as possible in Applied Sciences, I do not recommend this to be published, and suggest that the paper needs to be further revised. There are also some problems and suggestions listed in below:
The curvatures, thickness and refractive index of the final design should be listed in a Table, which can be as a good starting point for other researchers to further improve. In the 205th line, why the 18th surface was selected as the aspherical surface to correct aberration? Is there any theory to support this choice? Many writing mistakes, grammatical errors and uncertain words appear in this article and should be checked and revised, such as parameters in the formulas and the content of the article, the number of the formula, etc. In table 1 and table 5, why use the word “radiation” in the titles? Is there any parameter related to radiation in the tables? The full name of the English abbreviations should be provided while the English abbreviation is first used in this article, such as HFOV, and APS-C, etc. The complete design procedure and concept of the AF lens and ED lens should be provided. Why choose the AF lens of the lens module in figure 8 to autofocus the clear image? Why don't choose other lens in figure 8? In figure 8, showing whole AF lens should be better than showing half AF lens. In the abstract, authors mention the applications of the lens system with LEDs in this article, however, the introduction that how to apply LEDs in this AF system is not very clear. Hence, if LEDs are not used in this study, the description related to LED applications should be deleted so as to avoid the confusion of readers.
Author Response
Revision of “Design of Very Wide Angle and Large Aperture Optical System with Inner Focus for Compact Camera System Applications”
Dear Reviewers:
I would like to thank you for your thorough examination of this manuscript. I have carefully considered all of the comments and strived to address all of the issues raised in this resubmission. In my responses, I first repeat the comments (in black) and provide our detailed responses (in blue). Please note that all of the figure, page, and citation numbers in this document refer to those in the revised manuscript. The updated contents have also been highlighted in yellow in the revised manuscript.
I look forward to hearing from you
Best regards,
Prof. Hojong Choi
Prof. Jae-Myung Ryu
Dear Reviewer2
I really appreciate your efforts and time to review my manuscript, which enabled to improve its quality.
The author report on the design procedure of a very wide angle and large aperture optical system. They find that the inner focus system of this system can be applied for compact system cameras by moving a single lens. The method that design new lens module by modifying the old lens modules in patents is often seen in imaging optical design, however, that lacks the explanation of the necessary reasons for modifying the two lens modules in this article. Moreover, many similar designs had been widely developed in many compact camera systems. Hence, I have not find obvious innovative points or breakthroughs in this article. In addition, the study in this article just performs subsequent design by the commercial optical software, but doesn’t provide the discussions of the exact experimental results to verify the design results. Hence, based on the policy that provides the experimental results as detail as possible in Applied Sciences, I do not recommend this to be published, and suggest that the paper needs to be further revised. There are also some problems and suggestions listed in below:
Answer: The optical system in our paper are already presented in patents and the patent numbers are mentioned in our paper. And the optical system proposed in our paper has not been released by commercial camera companies. The theory mentioned in this paper may not be new, but nothing has been published in the field of wide-angle interchangeable lenses.
The curvatures, thickness and refractive index of the final design should be listed in a Table, which can be as a good starting point for other researchers to further improve. In the 205th line, why the 18th surface was selected as the aspherical surface to correct aberration? Is there any theory to support this choice?
Answer: The aberration is corrected by the aspherical surface, and the effect thereof is as shown in Equations (9) to (12). This theory is mentioned in the following book.
L. Malacara and Z. Malacara, “Hanbook od Optical Design” 2nd. Ed. Marcel Dekker, Inc. New York, 1994. Chap. 5
Many writing mistakes, grammatical errors and uncertain words appear in this article and should be checked and revised, such as parameters in the formulas and the content of the article, the number of the formula, etc.
Answer: This paper has already been corrected in English. Let's look carefully as we answer other questions.
In table 1 and table 5, why use the word “radiation” in the titles? Is there any parameter related to radiation in the tables?
Answer: Your comment is right. Therefore, we changed the titles of Tables 1 and 4 to 1st orders.
The full name of the English abbreviations should be provided while the English abbreviation is first used in this article, such as HFOV, and APS-C, etc. The complete design procedure and concept of the AF lens and ED lens should be provided.
Answer: This is also a good comment. HFOV is a half field of view, and APS-C stands for Advanced photo system type-C.
Why choose the AF lens of the lens module in figure 8 to autofocus the clear image? Why don't choose other lens in figure 8? In figure 8, showing whole AF lens should be better than showing half AF lens.
Answer: We think your opinion is very good. We think Figure 8 represents the moving lens more clearly. We don't think this is very important in the paper. Instead we will reflect the other important thing.
In the abstract, authors mention the applications of the lens system with LEDs in this article, however, the introduction that how to apply LEDs in this AF system is not very clear. Hence, if LEDs are not used in this study, the description related to LED applications should be deleted so as to avoid the confusion of readers.
Answer: We have studied ultrasound diagnostic imaging using this optical system and LEDs. However, as you point out, we did not use LEDs, so we removed all of them.
Reviewer 3 Report
Dear Authors,
Please, find my comments attached. I believe that the paper can be accepted after a revision.
Author Response
Dear reviewer, please find the author reply in the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The content of the article had been obviously revised and optimized after the first revision. The reasons for the author's reply are also generally reasonable. Hence, I recommend that the article could be accepted to publish in Applied Sciences.
