Transport-of-intensity Fourier ptychographic diffraction tomography: defying the matched illumination condition

Abstract

Optical diffraction tomography (ODT) is a promising label-free three-dimensional (3D) microscopic method capable of measuring the 3D refractive index (RI) distribution of optically transparent samples (e.g., unlabeled biological cells). In recent years, non-interferometric ODT techniques have received increasing attention for their system simplicity, speckle-free imaging quality, and compatibility with existing microscopes. However, ODT methods for implementing non-interferometric measurements in high numerical aperture (NA) microscopy systems are often plagued by low-frequency missing problems—a consequence of violating the matched illumination condition. Here, we present transport-of-intensity Fourier ptychographic diffraction tomography (TI-FPDT) to address this challenging issue by combining ptychographic angular diversity with additional “transport of intensity” measurements. TI-FPDT exploits the defocused phase contrast to circumvent the stringent requirement on the illumination NA imposed by the matched illumination condition. It effectively overcomes the reconstruction quality deterioration and RI underestimation problems in conventional FPDT, as demonstrated by high-resolution tomographic imaging of various unlabeled transparent samples (including microspheres, USAF targets, HeLa cells, and C2C12 cells). Due to its simplicity and effectiveness, TI-FPDT is anticipated to open new possibilities for label-free 3D microscopy in various biomedical applications.

High‐Speed Multi‐Modal Extended Depth‐of‐Field Microscopy with an Electrically Tunable Lens

“…[17][18][19][20] On the other hand, essential benefits provided by partially coherent light microscopy such as improved spatial resolution, optical sectioning, and speckle-noise suppression are exploited for optical diffraction tomography (ODT) microscopy. [21][22][23][24][25][26][27][28] However, both phase and absorption information of the complex refractive index of the specimen contribute to the measured intensity, [29] making it challenging to decouple the two contents with a single linear deconvolution filter. To solve this problem, it usually requires two or more datasets of the same object with different illumination functions, [29][30][31] while these methods result in measurement complexity and computation cost.…”

Deep Learning‐Enabled Pixel‐Super‐Resolved Quantitative Phase Microscopy from Single‐Shot Aliased Intensity Measurement

“…Furthermore, the use of fluorescent dyes and proteins as bio-markers inevitably limits certain non-fluorescent applications where biological samples cannot be easily tagged with fluorescent markers. [7,8] In recent years, the technique of computational microscopy, including interferometric [9][10][11] and non-interferometric [12][13][14] manners for both quantitative phase imaging (QPI) [15][16][17][18][19] and 3D refractive index (3D RI), [20,21] has been proved to be an invaluable tool regarding its distinctive capability to quantify the phase delay of unlabeled biological specimens in a non-destructive way. As two representative QPI approaches, transport of intensity equation (TIE) [22] and Fourier ptychographic microscopy (FPM) [23] have gained wide attention in the application of biomedicine.…”

Volumetric refractive index measurement and quantitative density analysis of mouse brain tissue with sub-micrometer spatial resolution

“…However, the use of a coherent light source such as laser inevitably involve speckle noise due to a long coherent length of laser and makes the system vulnerable to environmental vibration or perturbation, which prevents from translating into clinical laboratory. More recently, 3D QPI techniques based on low coherent light sources have been developed (22)(23)(24)(25). The use of an incoherent light source significantly reduced the coherent speckle noise while maintain the benefits of QPI.…”