CONFOCAL MICROSCOPE CM-1
USER INSTRUCTIONS
Scientific Instruments
Dr. J.R. Sandercock
Fabrik am Weiher
8909 Zwillikon-Switzerland
Phone: +41 44 776 33 66
Fax:
+41 44 776 33 65
E-Mail:
[email protected]
Internet:
www.jrs-si.ch
CH-8909, Zwillikon-Switzerland
Scientific Instruments
Properties of Confocal Microscope
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Resolution better than 1 micron. Numerical aperture 0.42
Working distance at maximum resolution 20mm.
Reach 80mm, maximum height of focal plane 93mm.
Switchable magnification from x15 to x3.75 without loss of focus.
Ideal for use with diamond anvil cell.
Smallest standard pinhole corresponds to about 4 microns on the sample.
Smaller pinholes available on request.
Accepts a low gain objective as alternative, which makes the microscope ideal
for surface and bulk backscattering Brillouin measurements.
For all gains the microscope is optimally coupled to the entrance aperture of
the interferometer.
The laser beam can be focussed independently of the sample
The output of the microscope can be coupled out to an alternative spectrometer
if desired by sliding a prism.
Provision for a filter or polariser / analyser (diameter 25mm).
Provision to redirect the laser beam directly into the interferometer for
alignment purposes.
The laser beam is coupled into the microscope using a polarising beam splitter. Without
additional polarising components therefore only depolarised scattered light will be
observed (spin-wave scattering for example). A quarter wave plate and a polariser can
be switched into the beam path (see figure 5). Using only the quarter wave plate,
scattering from isotropic media can be observed without loss of signal due to the beam
splitter. With both quarter wave and polariser, polarised scattering from general media
can be observed, but with an efficiency of only 25% due to the losses in the beam
splitter.
The laser beam is introduced into the microscope at a height of 100mm. The beam
reflected from the microscope should follow the path back to the laser. In order to
prevent interference in the laser the beam is deviated by 1 or 2 degrees. A special mask
is provided for this purpose.
Whenever the microscope is used it is important
to check that the beam is correctly aligned.
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CH-8909, Zwillikon-Switzerland
Scientific Instruments
Two user adjustments are provided:
1
The laser beam can be focussed independently of the microscope focus by means
of the knurled screw shown in figure 1.
Fig. 1
Focus
2
If the focussed spot is not exactly in the centre of the pinhole, even though the
external beam is correctly aligned, it can be corrected by adjusting the two screws
shown in figure 2.
Note that the screws give orthogonal adjustments but at 45° to the horizontal.
Fig. 2
Do not be tempted to make any other adjustments to the mirrors in the microscope!
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CH-8909, Zwillikon-Switzerland
Scientific Instruments
Fig. 3
A
B
Screw A is the normal focus adjustment for the microscope.
To obtain the reference beam for alignment of the interferometer, turn screw B fully anticlockwise until the screw is just released. To remove the reference beam turn the screw
fully clockwise until it is just tight.
Fig. 4
Polarisation controls C and D
C
D
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CH-8909, Zwillikon-Switzerland
Scientific Instruments
Fig. 5
F
E
Pull knob E fully outwards in order to steer the beam to another spectrometer. This
beam is parallel with a diameter of about 8mm. Since this beam exits before the
pinhole, this is no longer confocal.
Pull knob F out for full magnification (x15). Push in for low magnification (x3.75).
Description of the optics
In order to match the output optimally to the interferometer the output beam must fill an
aperture of f/18. This is achieved by the 150mm focal length lens with a beam diameter
of about 8mm. The objective has a focal length of 10mm (approx. f/1.2) and this gives
the basic magnification of x15. The laser beam in the current design does not fill the full
aperture of the system. It enters the microscope through a pair of 10mm focal length
lenses which can be adjusted to compensate for any divergence in the laser beam.
Since the laser beam is not limited by any aperture it remains Gaussian and the
focussed spot is therefore also Gaussian with a diameter of about 4 microns.
Figure 7 shows the beam expander in place. This reduces the used beam diameter
from the objective to just 2mm (f/4.8) and so reduces the magnification to x3.75. The
microscope remains optimally coupled to the interferometer.
The microscope can be used with any objective that is corrected for infinity and has a
beam diameter of about 8mm
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CH-8909, Zwillikon-Switzerland
Scientific Instruments
Fig. 6
Mirror 3
Mirror 2
/4
Polariser
Polarising
Beam Splitter
ø8mm Beam Diameter
LED
Pinhole
P
Mirror 1
Beam Splitter
P
Objective
f=10mm
f/1.2
Sample Focus
Beam Focus
Sample
Fig. 7
Beam Expander
Mirror 3
Mirror 2
/4
Polariser
Polarising
Beam Splitter
ø2mm Beam Diameter
LED
f=150mm
f/18
P
Mirror 1
Beam Splitter
P
Objective
f=10mm
f/4.8
Sample Focus
Beam Focus
Sample
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Pinhole