ne ws world
Designed to Measure
Made for High Powers
; 30K-W sensor measures up to 30KW
; Fast response – 7 sec
; High power density – 10kW/cm²
; Large aperture – Φ72mm
Measuring Higher Power
Than Ever Before
Zhang Heng of China's Han dynasty invented the first
seismoscope in AD 132. This is the base for the seismograph,
which has been serving mankind ever since
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a)
b)
Along with the pinhole size, the axial response curve depends
on the numerical aperture (NA) of the objective. Long axial
measurements were accomplished using an objective with a
low NA of 0.045. Photomultiplier tubes (PMTs) were used to
capture the fluorescent signals.
First, the axial response was measured by looking at widely
spaced 6 µm fluorescent beads, scanning in x and y while
adding an additional 300-µm-deep axial scan with a piezoelectric stage (used only for characterization). A fifth-order polynomial was fitted to the data to form a calibration curve. The
result was a 180 µm axial measurement range.
After additional calibration measurements, various images were
taken to demonstrate the 3D imaging capabilities of DDCFM. A
prepared sample with fluorescent beads at two different heights
150 µm apart and spread laterally over a wide 2D area was
imaged; the mean measured height difference was 150.6 µm.
To see how well the instrument could handle 3D structures,
the researchers imaged a knitted nylon fabric stained with fluorescein. Image versions were taken spanning a 4000 × 4000
µm field of view with the 0.045 NA objective. The results clearly
showed details of the fabric structure. Comparisons with scans
taken with a conventional 3D scanning confocal fluorescence
microscope showed comparable results (see figure).
The one disadvantage of
the DDCFM technique is
that, if there is more than
one fluorescent point along
an axial line (for example, if
the sample is partly transparent), then the results may not
be accurate; in this case, the
researchers expect that the
closest fluorescent point will
likely be the one measured.
The researchers believe that
DDCFM can be miniaturized to create a compact
endoscopic 3D fluorescence
imaging probe using fiberoptics for preclinical and clinical
research.
“Since we think the best
part of the presented technique is the capability of fast
3D imaging, we will first try
to get a movie that shows
dynamics of fluorescent particles,” says Dong-Ryoung Lee
of KAIST. —John Wallace
REFERENCE
1. D.-R. Lee et al., Opt. Exp., 21, 15,
17839 (July 29, 2013).
An image of nylon fabric taken
with a conventional confocal
fluorescence microscope with a
0.16 NA objective (a) is compared
to an image taken with DDCFM
(b; a 1600 × 1600 µm portion
of the 4000 × 4000 µm scan).
Heights are color-coded from
blue to red. (Courtesy of KAIST)
