Multi-Color Channel Gamma Correction in Fringe Projection Profilometry
, Yunpeng Zhang 1,†, Lingbao Kong 2, Xing Peng 3, Zhenjun Luo 1, Jie Shi 1 and Liping Tian 1Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this paper, a model of joint gamma correction for different color channels is proposed. Compared with the traditional gamma correction methods, the gamma correction method proposed in this paper is more accurate and has a larger effective working range after correction. Overall, the methodology of this work is described in detail. However, there are also some problems that need to be addressed.
1. In the introduction, the author analyzes the traditional gamma correction methods. However, the description of the multiple color channel is missing. What are the advantages and problems of multiple color channels?
2. Figure 1 presents the schematic diagram of grating projection employing multiple color channels, but Figure 1 does not show the principle well, and it is recommended that the author describe the complete workflow and highlight its characteristics.
3. In this paper, only the difference of the response curve between the proposed gamma correction method and traditional gamma correction method is compared. It is suggested to compare the difference of phase distribution between the two methods.
4. Lack of quantitative experiments. The authors need to supplement the standard parts for evaluating the improving effects.
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Reviewer 2 Report
Comments and Suggestions for AuthorsThis manuscript presents a proposed joint gamma correction model for different color channels, and the experimental results prove the effectiveness of the method. However, there are still some areas in the manuscript that can be improved as follows:
1. In Figures 6 and 9, the title of the figure should be on the same page as the corresponding image, and the overall aesthetics is poor, so it is recommended to modify it.
2. The authors mention in the manuscript that “the method can improve the accuracy of phase acquisition and measurement results," but the captured streak images and measured 3D surfaces are not shown in the manuscript, so the description is less convincing only from the text, and it is recommended to add this part of the experimental results.
3. In terms of presenting the experimental results, excellent results were obtained for the different color channels after correction. However, the effect of the correction is only shown in the analysis of the curves, could the authors consider comparing the traditional gamma correction method with the 3D surface corrected by the proposed gamma correction method to analyze the effectiveness of the proposed method, or the difference between monochrome and multicolor 3D surfaces? Additional experimental results in this regard are suggested.
4. The shaft captions in Figure 2 are not the same size as the shaft captions in the other figures.
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Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript "Multi-color channel gamma correction in fringe projection profilometry" proposes a model of joint gamma correction for different color channels. It first addresses gamma issues for each channel individually, and then supplements the correction by addressing color crosstalk between channels, ultimately improving the accuracy of phase acquisition in multi-color channel structured light measurement. However, there are some problems, which must be solved before it is considered for publication.
1. The author should provide a brief introduction to the current research on strategies for addressing color crosstalk issues and outline the fundamental principles involved.
2. The gamma correction method described in Section 3.1 of the manuscript demonstrates some effectiveness; however, there is potential for further improvement. For additional insights, the author could refer to Section 5.1 of Zuo's article [1].
3. To enhance the article's persuasiveness, it would be beneficial to briefly present and compare the 3D measurement results before gamma correction, before color crosstalk correction, and after the final correction.
4. The terms “more accurate and has a larger effective working range” mentioned in lines 24-26, are not explicitly demonstrated in the manuscript.
5. Lines 140-142 should be revised to indicate that γp is first obtained through fitting, and its reciprocal is then taken to calculate γo.
6. Lines 172-173 and line 183 provide inconsistent explanations of Ro, Go, and Bo in relation to Eqs. (10) and (12). In lines 172-174, the explanations of Ro, Go, and Bo appear to be reversed in relation to Rp, Gp, and Bp. The manuscript should clarify and correct this discrepancy.
7. The expression in lines 191-192 is inaccurate. If k is ignored, there would be no interference between the different color channels. The manuscript should revise this statement to accurately reflect the correct relationship.
Author Response
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Reviewer 4 Report
Comments and Suggestions for AuthorsIn this paper, the authors proposed a simple gamma correction method to perform joint gamma correction across different color channels. The study introduced an innovative approach and offers a practical solution to this issue. I recommend the paper for consideration of acceptance, though some minor revisions are suggested, as detailed below:
1. The font sizes in the figures should be more consistent. For example, the font size of "INPUT" and "OUTPUT" in Figure 2 should be smaller, and the font size in Figure 3 needs to be adjusted accordingly.
2. Figure 4, which illustrates the system diagram, should show the fully assembled system rather than simply depicting the individual components arranged separately.
3. The authors did not clearly explain why the specific range shown in Figure 5(b) was chosen for calculating the average intensity. I recommend providing a more detailed rationale for this selection.
4. The equation on page 11 should be properly labeled as “Eq. (17)”.
5. In Figures 9(a) and (b), it is evident that as the intensity of the red or green channels changes, the intensity of the other channels varies in a fairly linear fashion. However, in Figure 9(c), the intensity of the blue channel does not appear to affect the intensity of the other color channels. Could the authors provide a more detailed explanation for this? Is it because blue light does not influence the red and green channels? A clearer explanation would be appreciated.
6. In Figure 10, the authors used numerical values obtained from a specific row of the image to visually represent the correction results. However, it would be beneficial to include a comparison of the correction results before and after the gamma correction, or a quantitative analysis to show the reduction in error post-correction.
7. To improve the quality of the paper, I suggest that the introduction include a more thorough discussion of FPP.
Author Response
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Reviewer 5 Report
Comments and Suggestions for AuthorsAuthors present a method for gamma correction of projectors, which in essence is a colorimetric/photmetric/radiometric calibration of a projector. As currently presented, the work is not suitable for publication.
Major flaws:
1) Experimental evaluation is almost non-existant, and conclusions are not backed by experimental results.
Authros describe a procedure for colorimetric calibration of projector to achieve linear input-to-output intesity mapping. Presented experimental results include intensity mapping curves which are linear, but those are insufficient to claim "higher accuracy and a wider working range" (ln.155, 208-209) or a conclusion which states that the accuracy of phase acquisition is enhanced (ln.353). To claim increased phase accuracy you have to compute the (wrapped) phase, unwrap it, and compare it to the ground truth, both for a non-calibrated and for a calibrated projector. This was not done.
2) Novelty of the work is low
Three seminal works which are not cited are "Photometric Self-Calibration of a Projector-Camera System" (https://doi.org/10.1109/CVPR.2007.383468), which describes even more general form of calibration, "Range imaging with adaptive color structured light" (https://doi.org/https://doi.org/10.1109/34.682177), which describes used linear mixing model, and "Color mixing property of a projector-camera system" (https://doi.org/10.1145/1394622.1394641), which describes a better calibration procedure. Overall, in my opinion novelty w.r.t. the existing state of the art is non-existant.
Next, some parts of Section 3 describe untested solutions which cannot work in practice. Cosider the discussion on color mixing, ln.315-329, where it is claimed that by determining the mixing coefficients one can remove the phase error. This discussion completely disregards the albedo/color of the object which is observed, and as in general applications the object which is observe is unknown, one would have to perform additional measurements to determine the mixing coefficients for the particular object which is observed. In practice it is much more efficient to add several more phase shifts which eliminates the small channel cross-talk problem.
Comments on the Quality of English LanguageContent is mostly understandable, however article should be proofread by a native english speaker as sentces such as e.g. "In response to the above situation, the sinusoidal stripes input after passing through the projector no longer have sinusoidal." (ln.52) are incomprehensible.
Author Response
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Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have addressed my concerns.
Author Response
Comments 1: The authors have addressed my concerns.
Response 1: We appreciate the Reviewer's positive evaluation and constructive comments in the previous review, which helped us improve the manuscript significantly.
Reviewer 2 Report
Comments and Suggestions for Authors作者根据审稿人的意见对稿件进行了适当的修改，论文可以被接受
Author Response
Comments 1: 作者根据审稿人的意见对稿件进行了适当的修改，论文可以被接受
Response 1: We appreciate the Reviewer's positive evaluation and constructive comments in the previous review, which helped us improve the manuscript significantly.
Reviewer 3 Report
Comments and Suggestions for AuthorsSome of the issues have been addressed, but there are still some concerns after revision:
1. The font size in Fig. 2 is too small. I recommend that the authors adjust it and optimize the overall layout.
2. The response curve after gamma correction in Fig. 7 should be a straight line. Why is there still a curve after gamma correction using the proposed method. I suggest that the authors consult Section 5.1 of the cited article [1] to improve the gamma correction effect.
[1]. Chao Zuo, Qian Chen, Guohua Gu, Shijie Feng, and Fangxiaoyu Feng, "High-speed three-dimensional profilometry for multiple objects with complex shapes," Opt. Express 20, 19493-19510 (2012).
3. To ensure rigor, the variables in the comparative experiments should be controlled, and the objects being tested should maintain the same angle. However, the angles of the objects in Figs. 12(a), (b), and (c) differ noticeably. A similar issue is observed in Fig. 13.
4. In Fig. 5, the camera position has changed compared to the original version. As a result, the pattern captured in Fig. 6 should be adjusted accordingly.
Author Response
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Round 3
Reviewer 3 Report
Comments and Suggestions for AuthorsThe author's revisions are satisfactory, and it is recommended that the journal accept the paper.
