The analysis of Hela cells are very dependent on the segmentation of cell images, but the difficulty of cell image segmentation comes from two aspects: cell itself and imaging technology. we present a method for automatic segmentation of Hela cell imaging in digital holography(DH) in this paper. By using a DH imaging system and a cell segmentation algorithm based on adaptive threshold segmentation and watershed algorithm, cells that adhere to each other or have irregular shapes in the image can be segmented.
The measurement and visualization of transient three-dimensional (3-D) physical parameters (density and temperature) distribution of complex flow fields are critical technologies for the characteristics studies of flow fields in modern energy engineering. Among the optical computed tomography (OCT) methods, Moiré tomography has the advantages of simple optical path structure, strong anti-interference ability and wide measurement range, which is especially suitable for complex flow field measurement in noisy environments. Acquiring the transient phase information from the moiré projection is of great importance for the dynamic 3-D parameters reconstruction of complex flow fields. In this paper, the dynamic phase retrieve methods including Fourier and spatial phase-shifting in moiré tomographic are studied, respectively. In the Fourier method, an adaptive first-order spectrum extraction algorithm for Fourier transform moiré fringe and a phase calculation method are proposed. Through this, the projection phase can be obtained directly by multiplying the inverse Fourier transform of the positive first-order spectrum of deformed fringe with the inverse Fourier transform of the negative first-order spectrum of reference fringe. In spatial phase-shifting method, a spatial phase-shifting- interferometry-based moiré volume computed tomography (MVCT) method was proposed to extract the radial shearing phase distribution of grid moiré fringe. The measured results for the first-order partial derivative of the phase projection of a propane flame both by Fourier and spatial phase-shifting methods in the experimental moiré computed tomography systems are presented. The research will be valuable for monitoring the combustion state in energy engineering.
Researching the combustion process is important core contents in aviation, aerospace and energy engineering. And it has an important significance for the combustion researches to measure the physics parameters by combustion diagnosis and to acquire the 3D transient combustion distribution. Optical computerized tomography (OCT) applied in combustion diagnosis plays an important role in flow field diagnosis for its advantages of non-contact, real time, and 3D full-field measurements. The essence of CT is reconstructing the test field with projections from different directions. And the projections are independent to each other. Therefore, a multi-direction projections calibration should be performed before CT reconstruction, which can remap different projections to a unified coordinate to reduce the system errors from the installations and optical elements. Aiming at this problem, in this project, a multi-direction calibration method based on affine projection is proposed. By studying the affine projection theory, the calibration model was build based on single directional moiré tomographic system. Furthermore, the corresponding algorithm based on the calibration model is proposed. Finally, a multi-directional moiré tomographic system is built and combining with the calibration results for remapping the multi-directional projections, the 3D temperature distribution of the propane combustion flame was reconstructed.
Moiré tomography has been considered as an effective tool in studying flow fields because of its advantages such as non-contact measurement, strong anti-disturbing capability, and wide measurement range. The spatial phase-shifting method, which can simultaneously obtain several phase-shifted interferograms, can be applied in the flow field measurements by the moiré tomography when the flow field varies rapidly. In this paper, we present a new spatial phase-shifting shearing interferometry. The optical structure of the interferometry, which only consists of a crossed grating and a linear grating, is very simple. With it six phase-shifted interferograms can be acquired simultaneously. Based on the scalar diffraction theory, the explicit forms of intensity distribution of the interferograms containing the phase information can be derived and a corresponding four-step phase-shifting algorithm is proposed to extract the first-order partial derivative of phase projection from the interferograms. Finally, the spatial phase shifting optical system is used to retrieve the first-order partial derivative of propane flame phase projection produced by plane incident wave. This work is crucial to accuracy reconstruction the physical parameter of the varied flow fields in moiré tomography.
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