Pagina 15
10.4 Use of Bertrand lens
Bertrand lens allows observation in Orthoscopy and
Conoscopy.
In the disengaged position (“O”) the lens allows
observation in Orthoscopy, while in the inserted
position (“B”) it is possible to make observations in
Conoscopy.
1.
Rotate the upper knurled ring of the Bertrand
lens
①
to engage the “B” position. (Fig. 20)
2.
Using one objective from 20x to 60x, focus the
conoscopic image using the focus ring
②
.
3.
If the conoscopic image is not perfectly centered
with respect to the optical axis, center the image
using the centering screws
③.
• By turning the stage you will see black fringes
that will appear and disappear depending on
the rotation of the stage. These fringes are the
crystallization axes of that specific crystal. (Fig.
21)
Fig. 20
Fig. 21
①
②
③
