Automatic Focusing of Off-Axis Digital Holographic Microscopy by Combining the Discrete Cosine Transform Sparse Dictionary with the Edge Preservation Index
Automatic focusing is a crucial research issue for achieving high-quality reconstructed images in digital holographic microscopy. This paper proposes an automatic focusing method that combines the discrete cosine transform (DCT) sparse dictionary with edge preservation index (EPI) criteria for off-a...
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| Format: | Article |
| Language: | English |
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MDPI AG
2025-05-01
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| Series: | Optics |
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| Online Access: | https://www.mdpi.com/2673-3269/6/2/17 |
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| author | Zhaoliang Liu Peizhen Qiu Yupei Zhang |
| author_facet | Zhaoliang Liu Peizhen Qiu Yupei Zhang |
| author_sort | Zhaoliang Liu |
| collection | DOAJ |
| description | Automatic focusing is a crucial research issue for achieving high-quality reconstructed images in digital holographic microscopy. This paper proposes an automatic focusing method that combines the discrete cosine transform (DCT) sparse dictionary with edge preservation index (EPI) criteria for off-axis digital holographic microscopy. Specifically, within a predefined search range, Fresnel transform is utilized to reconstruct the off-axis digital hologram, yielding reconstruction images at various reconstruction distances. Synchronously, the DCT sparse dictionary is employed to reduce speckle noise, and the EPI is calculated between the denoised image and original image. The value of EPI is used as an indicator for assessing the focal position. A single-peak focusing curve is obtained within the search range 10 mm, with a step size of 0.1 mm. Once the optimal focus position is determined, a focused and noise-reduced reconstructed image can be simultaneously achieved. |
| format | Article |
| id | doaj-art-9c5f9929710846a59efab09e6208ab5f |
| institution | DOAJ |
| issn | 2673-3269 |
| language | English |
| publishDate | 2025-05-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Optics |
| spelling | doaj-art-9c5f9929710846a59efab09e6208ab5f2025-08-20T03:16:35ZengMDPI AGOptics2673-32692025-05-01621710.3390/opt6020017Automatic Focusing of Off-Axis Digital Holographic Microscopy by Combining the Discrete Cosine Transform Sparse Dictionary with the Edge Preservation IndexZhaoliang Liu0Peizhen Qiu1Yupei Zhang2Department of Applied Physics, Huzhou University, Huzhou 313000, ChinaDepartment of Applied Physics, Huzhou University, Huzhou 313000, ChinaZhejiang Provincial Key Laboratory of Energy and Environmental Protection on Measurement and Detection, Zhejiang Institute of Quality Sciences, Hangzhou 310000, ChinaAutomatic focusing is a crucial research issue for achieving high-quality reconstructed images in digital holographic microscopy. This paper proposes an automatic focusing method that combines the discrete cosine transform (DCT) sparse dictionary with edge preservation index (EPI) criteria for off-axis digital holographic microscopy. Specifically, within a predefined search range, Fresnel transform is utilized to reconstruct the off-axis digital hologram, yielding reconstruction images at various reconstruction distances. Synchronously, the DCT sparse dictionary is employed to reduce speckle noise, and the EPI is calculated between the denoised image and original image. The value of EPI is used as an indicator for assessing the focal position. A single-peak focusing curve is obtained within the search range 10 mm, with a step size of 0.1 mm. Once the optimal focus position is determined, a focused and noise-reduced reconstructed image can be simultaneously achieved.https://www.mdpi.com/2673-3269/6/2/17digital holographic microscopyautomatic focusingdiscrete cosine transform sparse dictionaryedge preservation index |
| spellingShingle | Zhaoliang Liu Peizhen Qiu Yupei Zhang Automatic Focusing of Off-Axis Digital Holographic Microscopy by Combining the Discrete Cosine Transform Sparse Dictionary with the Edge Preservation Index Optics digital holographic microscopy automatic focusing discrete cosine transform sparse dictionary edge preservation index |
| title | Automatic Focusing of Off-Axis Digital Holographic Microscopy by Combining the Discrete Cosine Transform Sparse Dictionary with the Edge Preservation Index |
| title_full | Automatic Focusing of Off-Axis Digital Holographic Microscopy by Combining the Discrete Cosine Transform Sparse Dictionary with the Edge Preservation Index |
| title_fullStr | Automatic Focusing of Off-Axis Digital Holographic Microscopy by Combining the Discrete Cosine Transform Sparse Dictionary with the Edge Preservation Index |
| title_full_unstemmed | Automatic Focusing of Off-Axis Digital Holographic Microscopy by Combining the Discrete Cosine Transform Sparse Dictionary with the Edge Preservation Index |
| title_short | Automatic Focusing of Off-Axis Digital Holographic Microscopy by Combining the Discrete Cosine Transform Sparse Dictionary with the Edge Preservation Index |
| title_sort | automatic focusing of off axis digital holographic microscopy by combining the discrete cosine transform sparse dictionary with the edge preservation index |
| topic | digital holographic microscopy automatic focusing discrete cosine transform sparse dictionary edge preservation index |
| url | https://www.mdpi.com/2673-3269/6/2/17 |
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