The current gold standard for tissue histopathology is based on the examination of stained tissue slices by pathologists. To save time and minimize human efforts, computerized methods in nuclei segmentation and classification have been advanced and popularized for histopathology applications. Digital histopathology has been increasingly applied to cancer diagnosis and prognosis. We proposed a label-free digital histopathology method based on refractive index maps measured from a large field of view optical diffraction tomography system. We measured breast cancer tissue slices and digitally processed the data for cancer grading.
We propose and demonstrate a digital micro-mirror device (DMD) based laser-illumination Fourier ptychographic microscopy (FPM) method for high-speed and high-resolution label-free imaging applications. Using this method, we can simultaneously retrieve phase and intensity images of samples, such as stained and unstained cancer tissue slices and cells. The system illumination is provided by a 532 nm laser, while two DMDs are utilized for achieving active illumination angle scanning and dynamic filtering. Our current system has achieved real-time imaging at 42 fps with around 1 𝜇𝑚 resolution.
Quantitative phase microscopy (QPM) has been applied to a wide range of applications, especially in biomedical imaging. The label-free nature of QPM measurement enables sample characterization without complicated and invasive chemical staining procedures on samples. Higher imaging resolution is always preferred for imaging microscopic structures. Synthetic aperture method can be used to enhance the resolution in QPM, namely forming a synthetic aperture phase microscope (SAPM). In SAPM, multiple images, captured under different sample illumination angles, are synthesized to enlarge the object spectrum to reconstruct a high-resolution phase image. However, multiple acquisitions decrease the imaging speed in SAPM. To solve this problem, we propose a single-shot synthetic aperture phase microscope method through reference beam modulation, enabled by digital micro-mirror devices (DMDs). The proposed system provides a resolution enhancement of around 1.4 folds without sacrificing the camera frame rate and field of view.
High speed, high resolution, and large field of view (FOV) are desired for many imaging applications. However, the increase of spatial resolution normally accompanies with a decrease in FOV. Aperture synthesis is often used to improve the spatial resolution, while the requirement of multiple recordings has decreased the temporal resolution. We propose a digital mirror-device (DMD) based synthetic aperture phase microscopy (SAPM) technique to achieve high space bandwidth product (SBP) measurements of sample surface height profiles and quantitative phase maps. Enhanced lateral resolution can be achieved by synthesizing different parts of the sample spatial spectrum, corresponding to different illumination angles, which is experimental demonstrated using resolution targets. The high-speed patterning capability of DMDs and their patterning flexibilities have allowed us to design holograms to generate multiple illumination angles simultaneously to significantly improve the image acquisition speed and reduce data redundancy. With a high-resolution camera and a motorized sample stage, we can extend the sample scanning area to several inches. We envision that the development of this high throughput synthetic aperture phase microscope will enable many potential cutting-edge applications in biomedical imaging and material metrology.
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