|
|
|
For a couple
of years now I have been shooting video clips of the organisms
I have observed through the microscope. I have modified a Logitech
Zoom web camera to capture video clips in either 640 x 480 pixel
resolution or 320 x 240 pixel resolution. As much as I enjoy making
still images through the microscope, video clips allow me to watch
the behavior of the organisms time and time again. It is the behavior
of the organisms that most interests me.
I have tried
several different methods of attaching the web camera to the microscope.
Originally, I simply glued a 35mm film canister, with the closed
end cut off, to the front of the camera centered over the lens.
I would place a spare eyepiece in the trinocular tube of the microscope,
build up a tape "bushing" around the trinocular tube,
and slip the camera/film canister combination over the eyepiece.
(See image at right.)
This worked
reasonably well for a time but I was constantly having to deal
with unevenly lighted backgrounds of various colors and hot spots
that were created by having the camera lens and eyepiece in close
proximity. Eventually, I removed the lens and cheap IR (infrared)
filter from the web camera and imaged directly onto the CCD sensor
in the camera. This worked better but image resolution wasn't
quite as good. (An article on the original modifications may be
found HERE.)
|
|
 |
|
|
|
I have since
found an easier and better method of attaching the web camera
to the microscope. I still take out the web camera lens and cheap
IR filter and image directly to the CCD sensor, however, I now
project the image onto the CCD sensor with a Nikon 2.5x projection
eyepiece. Projection eyepieces are designed to produce the sharpest
and most aberration-free images at a focal distance of 152 mm
(6") from the film plane/CCD sensor.
To obtain
this focal distance, I mount the web camera on a "standard",
tube-like camera microscope adapter in the trinocular port of
my Nikon microscope. The microscope
|
|
adapter
I obtained is made by Canon but there are any number of brands,
both name-brand and after-market, camera microscope adapters available
from about $9.95US to $39.95US. It does not matter what brand or
camera mount bought. All that is necessary is that the camera microscope
adapter be long enough to obtain an approximate focal distance of
152mm (6") from the shoulder of the projection eyepiece to
the ccd sensor. If the adapter is too short, a short extension tube
may be economically purchased to extend the length of the camera
microscope adapter. Just be sure the extension tube has the same
camera mount as the camera microscope adapter. |
|
|
|
Mounting the
web camera to the camera microscope adapter is quite simple. Purchase
a rear lens cap in the same camera mount as the camera microscope
adapter. Drill a 3/4" hole directly in the center of the
rear lens cap. With the lens removed from the web camera, carefully
center the CCD sensor in the opening drilled in the rear lens
cap. Once the sensor is aligned, glue the web camera to the rear
lens cap. You can use a hot-glue gun or, as I did here, glue the
web camera to the rear lens cap using 5-minute epoxy glue.
|
|
 |
|
|
|
Camera microscope
adapters come in two pieces. A short bottom piece (the aluminum
piece in the photo at right) attaches to the trinocular port of
the microscope and is tightened in place with a thumbscrew. A
projection lens is then inserted into the trinocular port. The
larger main tube will then be placed on top of the smaller bottom
piece.
|
|
 |
|
|
|
Once the larger
main body is placed over the smaller bottom piece, the web camera/rear
lens cap combination is mounted to camera microscope adapter.
The CCD sensor is now placed at the proper 152mm (6") focal
distance. Another advantage of this method of mounting a web camera
to a microscope is that the camera, projection lens, and trinocular
port become a single, sealed unit. This prevents dust from accumulating
on the CCD sensor and the CCD will require less frequent cleaning.
Since I have
removed the IR filter from the web camera I needed to replace
the IR filter somewhere within the light path. I scrounged an
old, defunct 35mm slide projector and removed the thick, green
heat-absorbing filter. I place this filter over the field condenser
at the bottom of the microscope to filter-out unwanted IR. Excessive
IR causes the image to be extremely red (CCD sensors are extremely
sensitive to IR) and also degrades resolution by forming an out-of-focus
IR image alongside the visible light image.
|
|
 |
|
|
|
At right is
a recent example of a video clip I recorded of an amoeba. The
web camera recorded the amoeba as an .avi file. I used Video Factory
by Sonic Foundary to convert the .avi file to a .wmv, Windows
Media Video, file and to perform some minor post-capture image
corrections. This video was recorded through my 1960s era Nikon
microscope using a LOMO 20x, NA 0.40, flat-field achromatic objective
and a Nikon CF 2.5x projection eyepiece.
Projection
eyepieces can be found quite often on eBay and at very reasonable
prices. Leitz, Nikon, Olympus, and Zeiss-Jena make excellent projection
eyepieces. Microscope adapters in various camera mounts may be
found quite frequently on eBay, too.
Enjoy!
©
Thomas L Webster 2005
|
|
 |
| 56k
video downloads click HERE. |
| DSL/Cable/T1
click HERE. |
|
|
