Text and photography copyright Thomas Webster 2005. All rights reserved.

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.


© Thomas L Webster 2005

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