Biomedical Engineering Reference
In-Depth Information
Fig. 14
Experimental measuring system Ir.M.A. (
a
), inner ordering of the system (
b
)
method as before. The main difference compared to the first generation is the use
of a camera AVT Prosilica GE-680B with higher resolution (640
240 with double
vertical binning) that preserves image capture speed 200 fps. The second change is
in the method of fixating image projection. The unique system of 3D stimulation
holograms is used. Fig.
13
gives the scheme for the Ir.M.A. system. The observer
is situated in front of the input aperture of the instrument with the head fixated
in a headrest. Thanks to higher camera resolution it is possible to observe both
eyes simultaneously (in contrast to E.M.AN.). Therefore, it is possible to obtain
information about the eyes' cooperation during a fixation point distance change.
The eccentric photorefraction diaphragm and infrared measuring beam source are
fixed on the lens of a high speed camera in the measuring part. Two prismatic lenses
in front of the camera lens remove an insignificant central part of the image (nose
root), shift edges to the centre and thereby allow higher resolution to be maintained
in the region of the pupils. A beam splitter located in front of the measuring part
separates the measuring and stimulating part. The transitivity of the beam-splitter
has to be maximal for the wavelength of the measuring beam and reflexivity has to
be maximal for the wavelength of the fixating images (Fig.
15
).
The patient's sight is fixated by laser reconstructed 3D holograms. Holography
allows a spatial object to be recorded on the surface of a photosensitive medium.
The situation is similar to classic photography. The object beams go through an
optical system and fall on a sensitive layer. Information about the intensity of each
particular beam is recorded in this sensitive layer. However, information about the
beam phase, the holder of spatial information, is lost. It is possible to record both
beam properties (intensity and phase) through the interference of light beams on
the sensitive medium. Fine grain photosensitive emulsion (about 10
m) on a glass
