Biomedical Engineering Reference
In-Depth Information
blue at slight stress) and enables simultaneous stress magnitude and
direction analysis. However, high-precision wave plates and quarter-
wave plates are necessary to obtain more accuracy in measurements
of stress magnitude and direction [1].
Polarizer
1/4L Plate
Arterial Model
J
Extra wave plate
1/4L Plate
Polarizer
a)
b)
Figure 4.17
Circular polariscope for simultaneous measurement of
stress magnitude and direction (left). High contrast between
background and surgical instruments (right). See also Color
Insert.
For this polariscope coniguration, the phase shift introduced by
the extra wave-plate wavelength is
QM
M
4
ex
'
2
(4.33)
and the effect of wave-plate into the light beam is deined by
'
'
'
¨
¸
2
2
2
cos
i
sin
cos
2
K
i
sin
sin
2
K
©
©
©
©
¹
¹
¹
¹
2
2
2
J
(4.34)
(,
'
K
)
'
'
'
2
2
2
2
2
i
sin
sin
2
K
cos
i
sin
cos
2
K
ª
2
2
º
where
K
is the inclination angle of the extra wave-plate. The
polariscope equation is then deined as follows:
EJ
J
J
J
J
J
E
(4.35)
out
P
(/)( ,
Q
2
R
'
K
)( ,
R
'
Q
/)(,
4
R
BR
)( ,
R
'
Q
/)()
4
P
0
in
2
1
1
Then the emerging beam intensity is given by
'
B
B
'
¥
§
¦
µ
·
¶
¥
§
¦
µ
¥
§
¦
µ
«
¬
-
»
¼
½
2
22
2
2
2
4
4
2
2
2
I
4
cc
sin
cos
·
¶
sin
·
¶
cc c
2
c
cos
1
2
1
2
1
2
2
2
2
2
(4.36)
«
¬
-
'
sin
R
'
»
¼
½
¥
§
¦
µµ
·
¶
¥
§
¦
µ
·
¶
2
2
2
c
2
2
2
cc
sin
B
(
c
c
)sin
2
R
c
sin
2
R
2
12
1
2
1
2
2
Figure 4.18 shows a color map calculated from above equation
considering
. The heterogeneous
dispersion of RGB ratio (color) over the map is maximized by the
Φ
2
=
1060 nm and
K
= 22.5°
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