Respect for Tissue Representation Using Photoelastic Stress Analysis for Endovascular Surgery Simulation - Microsurgery: Advances, Simulations, and Applications - page 133

that purpose we placed a variable retardation device inside the
polariscope shown in Fig. 4.7. This device is composed of stacked
quarter-wave plates oriented in the same direction, and providing
ive retardation zones of 0 M ex , M ex /4, M ex /2, 3 M ex /4, and M ex nm.

Changing the orientation of the variable retardation device inside
the polariscope and measuring the green light intensity at each
zone enables us to study the effect of R in the measurement of Re.
Green light intensity measurements were done in each zone for the
orientation range 0-180

= 560

° °

in 15 intervals.

Phantom

Variable
Retardation device

Connector

Region of
Intrest

Figure 4.7 Image of light retardation using the polariscope. Quarter-wave

plates stacked in a variable retardation device used for M G
calibration and the blood vessel model.

The measured green light wavelength was M G = 510 nm, the
quarter-wave plates provide a retardation of M ex = 140 nm with
10 nm accuracy. (The method for measuring the emerging beam
wavelength will be presented in the next section.) Therefore equation
(4.22) reduces to

¥
§ ¦

Re

– Q µ

· ¶

2

¨ ª

2

¸ º

I GN

R

sin 0 976 . 0 024 . sin ( 2 ) (4.23)

510

The variation of green light intensity with the direction of the
variable retardation device is shown in Fig. 4.8. Equation (4.23)
forecasts a maximum contribution of 2.4% of the device direction
to the intensity measurements. The maximum contribution of