Biomedical Engineering Reference
In-Depth Information
Fig. 4.18
Tomographic optofluidic imaging of
C. elegans
is illustrated. Different depth slices
through the worm from z
D
6 to
C
6m reveal distinct details. A conventional microscope
.10
/ image is also provided for the same worm
optical sectioning of micro-objects to reveal distinct details at different depths of
the objects. To prevent distortion in the final tomograms, the objects should ideally
flow rigidly through the chamber during the entire acquisition since uncontrolled
movements such as out-of-plane rotations may not always be digitally corrected.
4.8
Discussion and Conclusions
Lensfree on-chip holography is a rapidly emerging computational microscopy
modality that offers high-throughput imaging of biochips in compact, cost-effective,
and field-deployable architectures, as well as offering straightforward integration
with microfluidic platforms. Since objects are placed directly on the sensor and
away from the illumination source, holograms of micro-objects, for example, cells,
are recorded with unit magnification; as a result of which, the entire active area
of the sensor serves as the imaging FOV. This FOV is typically 24 mm
2
and
could further increase with next generation sensor chips that employ a larger
active area and smaller pixels. As we discussed earlier, the immediate drawback
of our unit magnification imaging scheme is that it limits the achievable spatial
resolution to
1:5m (for a typical pixel size of, e.g., 2:2m). To mitigate this
limitation, pixel super-resolution is shown to offer a unique solution by significantly
increasing the lateral resolution to <1m without compromising the large FOV of
our computational microscopes. As a further improvement to on-chip microscopy,
lensfree optical tomography has also been developed to significantly improve axial
resolution to <3m and achieve high-throughput 3D imaging of micro-objects
within biochips. As cost-effective LEDs are utilized without the need for sensitive
alignment, achieving multiangle illumination with multiple LEDs does not add a
