Author: |
Editor: ZHU Youqiang| Jan 26, 2021
Fourier ptychographic microscopy (FPM) is a recently developed computational imaging technique, which has high-resolution and wide field-of-view (FOV). However, due to the lower light efficiency of the off-axis LEDs, the exposure time of dark-field images has to be extended to improve the signal-to-noise of dark-field images. In addition, effected by the spherical illumination wavefronts of LEDs, the wavevectors of full-FOV are different.
Therefore, the full-FOV has to be divided into sub-fields and reconstructed sequentially, and then stitch them to obtain a full-FOV high-resolution images. It is necessary to develop a new illumination method to provide plane wave illumination with uniform intensity and different angles.
In a study published in Biomedical Optics Express, a research group led by Prof. Mu Quanquan realized a single full-FOV reconstruction FPM, which termed full-FOV Fourier ptychographic microscopy (F3PM). This research group comes from Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences.
This novel illumination method is achieved by the wavefront modulation of telecentric lens, and role of telecentric lens is to collect the wavefronts from LEDs and collimates them into plane waves. The telecentric character and excellent plane wavefront of telecentric lens are the key elements in wavefront modulation.
Telecentric character improves the illumination intensities of off-axis LEDs, and then the signal-to-noise of dark-field images are promoted.
Excellent plane wavefront guarantees the wavevectors are the same for full-FOV and the reconstruction process becomes more flexible, then the reconstruction size can be larger, even the single full-FOV reconstruction can be implemented.
For conventional FPM, the full-FOV images reconstruct process is consists of multiple reconstructions, intensity correction for different sub-fields and image stitching. In order to meet the needs of image stitching and light intensity correction, the overlap rate between adjacent sub-fields should be guaranteed 30% or more. Compared with conventional FPM, the size of single reconstruction of F3PM has been increased from 0.25mm2 to 14.6mm2, and the step of image stitching and its calculation redundancy can be eliminated. Without these cumbersome steps, the reconstruction process for full-FOV high-resolution images is simpler. Based on multi-coding light scheme and wavefront modulation of telecentric lens, the single full-FOV reconstruction enables the dynamic imaging of FPM.
Contact:
Auther: Prof. Mu Quanquan
Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences
Changchun, Jilin 130033, China
E-mail: muquanquan@ciomp.ac.cn
Article links: https://www.osapublishing.org/boe/fulltext.cfm?uri=boe-11-12-7175&id=442666
Fig. 1. (a) 3D schematic of F3PM; (b) Telecentric character and f-θ property of TL (Photo by CIOMP)
Fig. 2. Reconstruction results of F3PM and conventional FPM (Photo by CIOMP)
Fig. 3. The cervical smear cells reconstruction results (Photo by CIOMP)
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