We demonstrate the ability of our imaging system through several phantom/chicken and in vivo
experiments. In these experiments, the 532nm laser beam illuminated the sample surface over an
area of 1 × 1 mm2
which is below the American National Standards Institute safety limit of 20
. The four actuators driven by 0~4V differential ramp voltages were used for
scanning an area of up to 9 × 9 mm2
given a distance of 9 mm between MEMS
mirror and image surface and an optical scan angle of ± 31° for the MEMS
mirror .The scanning frequencies used were 100 and 2 mHz along X and Y directions to collect
signals at 50 x 50 points. Due to the 10 Hz repetition rate of the laser, the scanning time is
currently limited to 250s for the experiments performed.
In the phantom experiments, we placed the probe 6mm away from the phantom surface with
ultrasound gel applied between the probe and the phantom. With a 90° directivity
along the axial direction, the probe can cover an area of 24mm in diameter. As shown in
, the pencil lead was embedded 1.2mm below the surface of a 50mm-diameter cylindrical
solid phantom, consisting of Intralipid as the scatterer and India ink as the absorber. The
(absorption coefficient) and
(reduced scattering coefficient). Agar powder (2%) was used to solidify the
presents a typical A-line signal collected (blue line), along with its amplitude after the
Hilbert transform (red line), while shows the
2D image of the object. Using the criteria defined by the full-width-at-half maximum (FWHM) of
multiple A-line signals, the size of the recovered object is estimated to be 0.72mm compared to
the actual object size of 0.70mm. The signal-to-noise ratio (SNR) of the image signals was found
to be 32dB which decreases with increased depth of the target. In this experiment, we placed the
pencil lead at different depths and found that the imaging depth can be up to 2.5mm. We also
found that the axial resolution is less than 0.5mm and that the lateral resolution is less than
(a) Photograph of a phantom containing a single object. (b) A typical raw signal (blue) and
signal after the Hilbert transform (red). (c) The recovered 2D image.
and gives the photograph and recovered image
of another phantom where multiple targets were embedded at different positions/depths. From the
image shown in
, we see that the
targets are all detected.
Photograph of a phantom containing multiple objects (a) and the recovered 2D image (b).
The results given in
show the three dimensional imaging ability of our system. In this experiment, a pencil
lead with a diameter of 0.7mm was embedded in one piece of chicken  at a depth of 1.5mm from the surface. The recovered 3D images are
presented in – (at coronal, sagittal- and cross-section views) and in (3D rendering of the recovered image). Again, the
object is accurately imaged in terms of its size, shape and location.
(a) Photograph of the chicken with an embedded object. (b)-(d): coronal, sagittal and
cross-section views of the recovered 3D image. (e): the 3D rendering of the recovered