Biomedical Engineering Reference
In-Depth Information
A
- 6.00 cm
Image of eyepiece
Eyepiece
Objective
(entrance pupil)
-16.67 D
+10.00 D
- 6.67 D
- 15.00 cm
B
- 6.00 cm
Objective
Eyepiece
-16.67 D
-25.00 D
Image of objective
(exit pupil)
- 2.4 cm
- 41.67 D
Figure A-1.
A.
When a Galilean telescope is viewed while facing the objective lens,
the observer will see both the objective lens and a virtual image of the eyepiece.
Since the objective subtends a smaller angle at the observer's eye, it is the entrance
pupil. The three light rays remind us that light is traveling from left to right.
B.
When
the same Galilean telescope is viewed while facing the eyepiece, the observer sees
the eyepiece and a virtual image of the objective that's within the telescope tube. The
image of the objective subtends a smaller angle at the observer's eye, making it the
exit pupil.
Since the diameter of the eyepiece is 1.5 cm, the size of its image is
(2.50)(1.5 cm)
3.75 cm
When the telescope is viewed facing the objective lens, does the image of the
eyepiece or the objective itself subtend the smallest angle? Let's pick an arbitrary
viewing distance of 1.00 m. At this distance, the angle subtended by the objective
can be calculated as follows:
=
