Accurate and Rapid Auto-Focus Methods Based on Image Quality Assessment for Telescope Observation
<p>(<b>a</b>) Auto-focus diagram of a Cassegrain telescope system; (<b>b</b>) Hardware experiment system.</p> "> Figure 1 Cont.
<p>(<b>a</b>) Auto-focus diagram of a Cassegrain telescope system; (<b>b</b>) Hardware experiment system.</p> "> Figure 2
<p>Auto-focus search process. IEF, image estimation function.</p> "> Figure 3
<p>Different experimental scenes of the electro-optical tracking system (EOTS) auto-focus: (<b>a</b>) Windows of distant buildings, (<b>b</b>) Air conditioner outdoor unit, (<b>c</b>) Billboard, (<b>d</b>) Pipes on the roof, (<b>e</b>) Tower crane at a construction site, (<b>f</b>) Roof decoration of tall buildings, (<b>g</b>) Leaves in the distance, (<b>h</b>) Top railing of a building.</p> "> Figure 4
<p>Comparison of different IEFs, corresponding to the scenarios shown in <a href="#applsci-10-00658-f003" class="html-fig">Figure 3</a>.</p> "> Figure 4 Cont.
<p>Comparison of different IEFs, corresponding to the scenarios shown in <a href="#applsci-10-00658-f003" class="html-fig">Figure 3</a>.</p> "> Figure 5
<p>Dynamic focus window for the scene in <a href="#applsci-10-00658-f003" class="html-fig">Figure 3</a>h.</p> "> Figure 6
<p>Comparison of three auto-focusing window selection methods: WIF (whole-image focus), TCFW (traditional center window), and ES-DAWF (even sampling–dynamic adaptive focusing window selection).</p> ">
Abstract
:Featured Application
Abstract
1. Introduction
2. Auto-Focus Experiment Set
3. Comparison of Image Estimation Functions
4. An Improved Focusing Window Selection Method
5. Conclusions
- (1)
- In many image scenes collected by telescope, the Tenengrad function has high sensitivity (slope) near the peak value, which can better reflect the defocusing process of telescope system imaging. It is thus suitable as the estimation function of a telescope system;
- (2)
- From the experimental results of different focusing window methods, it can be seen that the ES-DAFW method can provide higher sensitivity and more accurate results for the auto-focus process, especially for a sparse image, when compared with the whole-image focusing window and the traditional center focusing window selection methods. At the same time, it has the advantages of simple calculation and can obviously shorten the time required for auto-focusing. These results promise significant applications to auto-focusing in other telescopes with EOTSs.
Author Contributions
Funding
Conflicts of Interest
References
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Scene a | Scene b | Scene c | Scene d | Scene e | Scene f | Scene g | Scene h |
---|---|---|---|---|---|---|---|
0.5373 | 0.8120 | 0.7846 | 0.8407 | 0.8125 | 0.7576 | 0.7773 | 0.9630 |
0.6268 | 0.8524 | 0.8345 | 0.9189 | 0.8889 | 0.8033 | 0.8430 | 0.9673 |
0.9906 | 0.9780 | 0.9328 | 0.9735 | 0.9748 | 0.9048 | 0.9726 | 0.9782 |
1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 |
0.7947 | 0.9658 | 0.8437 | 0.7972 | 0.9530 | 0.8274 | 0.9637 | 0.9871 |
0.6390 | 0.9234 | 0.7534 | 0.7091 | 0.8995 | 0.7147 | 0.8439 | 0.9637 |
0.5564 | 0.8470 | 0.6928 | 0.6522 | 0.8022 | 0.6538 | 0.7638 | 0.9528 |
Scene a | Scene b | Scene c | Scene d | Scene e | Scene f | Scene g | Scene h |
---|---|---|---|---|---|---|---|
0.7430 | 0.9486 | 0.8742 | 0.8537 | 0.8926 | 0.9478 | 0.8835 | 0.9784 |
0.7636 | 0.9522 | 0.8851 | 0.9236 | 0.9234 | 0.9585 | 0.9127 | 0.9922 |
0.9685 | 0.9987 | 0.9295 | 0.9412 | 0.9537 | 0.9635 | 0.9648 | 0.9993 |
1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 |
0.8469 | 0.9657 | 0.9091 | 0.9318 | 0.9618 | 0.9697 | 0.9730 | 0.9458 |
0.7962 | 0.9274 | 0.8611 | 0.8662 | 0.9062 | 0.9256 | 0.9123 | 0.9176 |
0.7406 | 0.8486 | 0.8428 | 0.7475 | 0.8275 | 0.8925 | 0.8403 | 0.8992 |
Scene a | Scene b | Scene c | Scene d | Scene e | Scene f | Scene g | Scene h |
---|---|---|---|---|---|---|---|
0.8253 | 0.9182 | 0.8879 | 0.8534 | 0.8842 | 0.8842 | 0.8994 | 0.9681 |
0.8525 | 0.9342 | 0.9038 | 0.8842 | 0.9234 | 0.9055 | 0.9146 | 0.9842 |
0.9715 | 0.9832 | 0.9437 | 0.9714 | 0.9389 | 0.9593 | 0.9762 | 0.9973 |
1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 |
0.9194 | 0.9741 | 0.9194 | 0.9342 | 0.9734 | 0.9294 | 0l9537 | 0.9748 |
0.8621 | 0.9325 | 0.8856 | 0.8792 | 0.863 | 0.8913 | 0.8774 | 0.9695 |
0.8423 | 0.8832 | 0.8723 | 0.8344 | 0.7841 | 0.8725 | 0.8122 | 0.9599 |
Scene a | Scene b | Scene c | Scene d | Scene e | Scene f | Scene g | Scene h |
---|---|---|---|---|---|---|---|
0.6642 | 0.9658 | 0.8443 | 0.7425 | 0.8892 | 0.8442 | 0.7559 | 0.9536 |
0.7354 | 0.9904 | 0.8651 | 0.7935 | 0.9117 | 0.8639 | 0.8248 | 0.9810 |
0.8543 | 1.0000 | 0.9318 | 0.9051 | 0.9610 | 0.9317 | 0.9146 | 0.9983 |
1.0000 | 0.9835 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 | 1.0000 |
0.8523 | 0.9734 | 0.9073 | 0.8754 | 0.9626 | 0.9252 | 0.9236 | 0.9881 |
0.7332 | 0.9256 | 0.8426 | 0.7640 | 0.9173 | 0.8631 | 0.8648 | 0.9689 |
0.6942 | 0.9052 | 0.7932 | 0.7223 | 0.8246 | 0.7980 | 0.7226 | 0.9677 |
Scene a | Scene b | Scene c | Scene d | Scene e | Scene f | Scene g | Scene h |
---|---|---|---|---|---|---|---|
0.9722 | 0.9810 | 0.9174 | 0.9485 | 0.9557 | 0.9347 | 0.9527 | 0.9510 |
0.9881 | 0.9583 | 0.9246 | 0.9477 | 0.9485 | 0.9638 | 0.9736 | 0.9659 |
0.9901 | 0.9831 | 0.9050 | 0.9531 | 0.9602 | 0.9750 | 09801 | 0.9483 |
1.0000 | 0.9677 | 1.0000 | 0.9335 | 0.9647 | 1.0000 | 1.0000 | 0.9631 |
0.9598 | 0.9432 | 0.9378 | 0.9546 | 1.0000 | 0.9345 | 0.9734 | 0.9577 |
0.9626 | 0.9259 | 0.8893 | 0.9539 | 0.9520 | 0.9130 | 0.9526 | 0.9731 |
0.9762 | 0.9376 | 0.8734 | 0.9665 | 0.9663 | 0.8773 | 0.9257 | 0.9677 |
Tenengrad | Brenner | Variance | Laplace | Entropy | |
---|---|---|---|---|---|
Scene a | 0.371 | 0.156 | 0.131 | 0.250 | 0.027 |
Scene b | 0.212 | 0.204 | 0.183 | 0.136 | 0.050 |
Scene c | 0.273 | 0.104 | 0.111 | 0.156 | 0.049 |
Scene d | 0.326 | 0.211 | 0.161 | 0.244 | 0.035 |
Scene e | 0.289 | 0.215 | 0.214 | 0.240 | 0.080 |
Scene f | 0.333 | 0.112 | 0.139 | 0.241 | 0.085 |
Scene g | 0.321 | 0.186 | 0.183 | 0.293 | 0.063 |
Scene h | 0.083 | 0.092 | 0.058 | 0.061 | 0.032 |
WIF | TCFW | ES-DAFW | |
---|---|---|---|
Scene a | 0.183 | 0.13 | 0.316 |
Scene b | 0.071 | 0.075 | 0.161 |
Scene c | 0.103 | 0.054 | 0.129 |
Scene d | 0.093 | 0.05 | 0.174 |
Scene e | 0.053 | 0.055 | 0.146 |
Scene f | 0.120 | 0.035 | 0.155 |
Scene g | 0.071 | 0.075 | 0.101 |
Scene h | 0.018 | 0.012 | 0.047 |
WIF(s) | TCFW(s) | ES-DAFW(s) | |
---|---|---|---|
Scene a | 8.36 | 6.37 | 3.27 |
Scene b | 7.94 | 6.58 | 3.54 |
Scene c | 8.12 | 6.14 | 4.79 |
Scene d | 6.37 | 5.24 | 3.71 |
Scene e | 9.28 | 7.64 | 4.39 |
Scene f | 7.83 | 7.14 | 4.03 |
Scene g | 9.28 | 6.39 | 5.17 |
Scene h | 12.41 | 10.75 | 6.32 |
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Yang, C.; Chen, M.; Zhou, F.; Li, W.; Peng, Z. Accurate and Rapid Auto-Focus Methods Based on Image Quality Assessment for Telescope Observation. Appl. Sci. 2020, 10, 658. https://doi.org/10.3390/app10020658
Yang C, Chen M, Zhou F, Li W, Peng Z. Accurate and Rapid Auto-Focus Methods Based on Image Quality Assessment for Telescope Observation. Applied Sciences. 2020; 10(2):658. https://doi.org/10.3390/app10020658
Chicago/Turabian StyleYang, Chunping, Minhao Chen, Fangfang Zhou, Wei Li, and Zhenming Peng. 2020. "Accurate and Rapid Auto-Focus Methods Based on Image Quality Assessment for Telescope Observation" Applied Sciences 10, no. 2: 658. https://doi.org/10.3390/app10020658