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The required exposure times are given below:
Film
Fixed light
Stroboscope
Photo
developed to
100 Hz
Flash
Stortz
1/4
1f1
( +)
800 ASA
Wolf
1 /60
1f15
f 5,4
Olympus
1f15
1/4
++
Stortz
1/a
1f2
+
1600ASA
Wolf
1 /120
1 /30
f6,3
Olympus
1 /30
1/s
+
T00362GBO
Table 4.2. Exposure times. The
+
designation for photoflash {1/60 s
setting) indicates useful results, and f 5,4 and f6,3 indicate
that a smaller aperture than the maximum must be used
As can be seen from Table 4.2 above the Wolf device provides the highest light through-
put and it may be used either with less sensitive films or with a telelens which enlarges
the picture.
This
is not recommended for the two other devices. However, both manufac-
turers market devices with much better light throughput.
If the 50 mm focal length lens of the camera is replaced by a 35 mm focal length lens, the
exposure time may be reduced by a factor of two or the film sensitivity may be similarly
reduced. This does, however, result in a reduction of the film picture size by a factor of
1/2,
and further photographic enlargement may be required.
Note: The above exposure tables should only be used as a very rough guide.
4.6.
VIDEO CAMERA
By connecting a video camera to the eyepiece of a rigid endoscope, fibrescope or
operation microscope, demonstrations to an audience and permanent recordings can be
made.
Video techniques have already been very useful for the inspection of hidden enclosures
by means of fixed light. However, the demonstration of stroboscopic motion in colour
through endoscopes and fibrescopes has been lacking due to problems caused by too
little light.
This problem has been solved by the very powerful stroboscopic light supplied by the
Type 4914, and the Olympus OTV-E medical TV system. These developments have made
it possible to obtain clear colour recordings of stroboscopic motion even through the
very thin (3, 7 mm) Olympus ENF type P fibrescope.
4.7.
USE OF THE TYPE 4914 WITH OTHER ELECTRONIC INSTRUMENTS
The Type 4914 is intended to stand on its own with various optical instruments to pro-
vide a very useful diagnostic system. However, if other instruments need to be synchro-
nized to the motion of the vocal cords e.g. a muscle simulator or another stroboscope
its TRIGGER OUTPUT signal may be used to trigger these devices. The output signal is
a 14
µs,
1 O V positive pulse which is floating with respect to the Type 4914 since it is
transformer coupled for safety reasons. (The Type 4914 cannot trigger another Type
4914 without additional circuitry).
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