Technical information

ICT in the science department 1628 © CLEAPSS 2005
Table 16.9 A digital microscope vs a separate microscope + camera
Digital microscope Separate microscope + camera
Equipment
A digital microscope is usually supplied as a package; all
items should be mutually compatible.
All equipment needs to be mutually compatible. Items
required include:
microscope
camera / flexcam
adaptor to connect camera and microscope.
In addition, both systems will also require leads and other equipment for displaying (and, if required, manipulating) the
images, as listed in Table 16.4.
Features / notes
The camera is normally integrated into the body of the
microscope and supplied with a compatible lead to
connect the camera and display device. Compatible
software is likely to be provided.
Care must be taken to ensure that all equipment and software
are compatible.
Once the initial setting-up of the microscope has been
mastered, it is easier to connect up and use each time.
More skill might be needed to set up and possibly adapt the
equipment to enable quick and reliable connections to be
made each time.
The equipment can only be used for video microscopy,
though in some models, the camera can be detached
and used independently.
The camera / flexcam and microscope can be used
independently for other applications (though the equipment’s
popularity might make this feature a disadvantage between
competing departments!).
The manufacturer can arrange the optics to optimise the
image quality.
If the camera is mounted over the eyepiece, image quality
might be compromised since light has to pass through more
optical components. However, this might only be significant at
high magnifications.
Considerations in using a separate microscope + camera for video microscopy
There are certain factors additional to those already discussed generally for image
capture and in section 16.6.7 (Microscope cameras). Some of the following points are
also appropriate to digital microscopes.
Microscope
The optics of the microscope to be used with a separate camera should be chosen
for flatness of field of view. Experienced microscope users become adept at moving
a slide to see what they want, allowing automatically for the image inversion. It
may not be so easy if they adjust the specimen while viewing its image on a
monitor screen and it may be preferable to use a demonstration microscope,
looking directly through one eyepiece while the camera is attached to the other.
Tests by CLEAPSS suggest that a microscope with an objective having a numer-
ical aperture (NA) of 0.1 is adequate; detail that requires a higher NA to resolve it
may not be seen with many cameras. (For further information, see Numerical
Aperture under Background information in section 10.5.1.)
It is important to magnify the image optically before it reaches the camera sensor,
so that detail of the specimen falls on as many pixels as possible; magnifying the
image electronically will not improve resolution.
Camera
Immediacy and the ability to utilise opportunities as they arise are major benefits
of video microscopy. The ability to view images in real time is therefore particular-
ly critical. While it is possible to prepare excellent still pictures and movie clips in
advance, plenty of good-quality material is available from other sources, including
free resources on the Internet. Incidentally, some digital microscopes (eg, the
Motic Digiscope) do not allow the image to be viewed while short video clips are
being captured. This can be inconvenient; for example, a water flea might swim
out of the field of view while the video clip is being recorded.
To obtain a good picture, the camera should be focused on infinity and then the
microscope optics should be used to focus the image. This is easiest if the front
lens of the camera can be removed and the camera inserted in place of the micro-