Biomedical Engineering Reference
In-Depth Information
Fig. 9.9.
Results of in vitro investigations on a human stomach: Filtered phase
difference distributions of a “healthy” area (
a
) and a region containing an adeno
carcinoma (
b
)
light image of a USAF 1951 test chart positioned in a distance of 5 mm in
front of the sensor is depicted. Figure 9.8b shows the corresponding speckle
image affected by illumination with coherent light (
λ
= 514
.
5 nm). Within the
speckle image a lateral resolution of 8.7
m is obtained. Figure 9.8c,d presents
results from a recorded series of displacement measurements with a white
painted metal plate, which was tilted between two recordings to demonstrate
the fringe resolution and quality. Shown are the correlation fringe pattern
(Fig. 9.8c) and the respective filtered wrapped phase difference distributions
modulo 2
π
(Fig. 9.8d) converted to 256 gray levels. The maximum displace-
ment resolution of the system in this configuration can be estimated from the
noise of the phase difference map to
λ/
7. To demonstrate the performance of
the distal ESPI sensor on biological specimens analogous to the experiments
described in Sect. 9.3.1, investigations on tumorous human stomach gastric
wall (in vitro) have been carried out.
In Fig. 9.9 the filtered wrapped phase difference distribution of a “healthy”
part of the specimen is depicted (imaged area about 1 cm
2
), which has been
stimulated manually with a test needle. The results are concentric fringe pat-
terns around the tip of the needle. In contrast, an area containing an adeno
carcinoma shows a parallel fringe pattern (Fig. 9.9b), indicating that the tissue
elasticity in this region is diminished, which is in agreement with the results
from Sect. 9.3.1.
µ
9.4 Microscopic (Speckle) Interferometry
In microscope ESPI, the motivation is to integrate the interferometric metrol-
ogy into microscope systems to achieve an enhancement of these techniques
by an additional high resolution detection and visualization of movements,
displacements [24, 25], and refractive index changes. Figure 9.10 shows the
