Compressive Holographic Microscopic Tomography
The content linked on this page refer to the journal paper,
"Video-rate compressive holographic microscopic tomography," Opt. Express 19, 7289-7298 (2011).
Main contributions are to adapt compressive holography to microscopy and to demonstrate its effectiveness in dynamic 3D imaging. \
We note that the theoretical framework developed in this project can be generalized to other microscopic geometries with small modifications which may utilize more complicated incident fields.
We consider a microscopic system composed of a point source for illuminating the objects and the FPA that measures the Gabor hologram.
In the experiment, a He-Ne laser with 632.8nm wavelength is used as a light source.
A microscope objective with 0.65NA manufactured by LOMO is used to generate a spherical wave for illuminating the sample.
The microscope objective is chosen to have a larger NA (0.65) than the microscope system NA (0.27) to ensure uniform illumination intensity on the FPA.
A Lumenera CMOS sensor records the hologram. The sensor has 1280*1024 resolution, 5.2 micron pixel pitch, 10 bit digitization, and the maximum frame rate 15fps. Figure 2(a) shows a photograph of the microscope instrumentation. The relative positions of the microscope objective and the sample are adjusted by two 3-axis stages. Figure 2(b) shows a photograph of the container in which two live water cyclopses of roughly the same size are floating in water.
The depth of the container is 2 or 3mm. The distance from the FPA to the microscope objective for illumination is 10 mm.
Figure compares the backpropagation reconstructions with compressive holographic reconstructions obtained with a single 2D measurement of the two live water cyclopses.
Figures (a) and (b) show transverse slices of the backpropagation reconstructions at z = 3.31mm and 1.87mm, respectively.
Figures (c) and (d) show transverse slices at the same axial positions as those in Figs. (a) and (b).
It is clear that the compressive holography reconstructions show significantly better localization (or sectioning) capability.
Also, the compressive holography reconstructions suffer less from the undesired background noise resulting in better image contrast.
For example, the tails and antennae of both water cyclopses are remarkably sharper and more discernible in Fig. (c) and (d) compared to those in Fig. (a) and (b).
Figure compares the magnified tails, marked by rectangles in the previous figure.
The detailed comparison shows clear difference between the two reconstructions and their changes in the axial direction.
The reconstruction was performed on a digital computer with Intel Core2 Quad CPU Q9300 at 2.5 GHz and 8 GB of RAM. The codes were written in Matlab 7.7.