Modify a Webcam for Videomicrography

Part II: Webcam Modifications
Text and photography copyright Thomas Webster 2003. All rights reserved.
Please keep in mind that the modifications I am about to suggest will void the manufacturer's warranty. I will not be held responsible for any damages that may occur, real or imagined, to your webcam and the implementation of the following modifications and procedures are done so at your own risk!! You will be solely responsible for any damages done to your own webcam!!
Modified webcam installed on trinocular port.

Webcam Modifications...The first order of business is to remove the lens. Why? The CCD array is tiny, 1/3". This, in itself, guarantees a high power at the plane of the CCD array. Introducing an eyepiece as a relay lens serves only to increase the magnification of the image. The view through the visual eyepieces of the microscope then becomes considerably less magnified than the view captured on the CCD array. Also, you will experience the same issues that people connecting digital cameras to microscopes experience. If the entrance pupil of the webcam's lens is larger than the exit pupil of the microscope's eyepiece, then the images will be partial circles in a square format. I don't particularly care for the looks of these images. Directly projecting the microscope's image from the objective lens onto the CCD array avoids over-magnification of the image and results in a completely filled, rectangular image frame. With my webcam, the field of view through the CCD array appears to be somewhat equivalent to a visual field of view when using 15x eyepieces in the binocular viewing head.

Removing the lens from the Logitech Quick Cam® Zoom™ is very easy. A single screw holds together the two halves of the camera body. Remove the screw and gently pry apart the two halves of the camera body. There is a rubber-like focusing ring that grips the lens assembly. Gently pry this from the camera body and slide it off the front lens assembly. Turn the front lens assembly counterclockwise until it separates from the rear half of the lens assembly. Behind the front lens assembly lies the infrared filter at the bottom of the rear lens assembly. For reasons I will discuss later, this assembly needs to be removed also. Carefully remove the electronics board from the camera body. On the backside of the board are two, small Phillips-head screws. Remove these screws to remove the rear lens assembly and expose the CCD array. Caution!! Do not touch the protective cover over the CCD array!! Avoid getting dust or any other material on the protective cover!!

On the electronics board you will also see a fairly large, green LED. This LED must be covered with black tape so that green light does not fall on the CCD array. Carefully cut a small piece of black electrician's tape and completely cover the green LED. Now, fit the electronics board back into the proper slots in the camera body and snap the two camera body halves back together. This is a good time to eliminate the mounting base that came with the camera, too. The mounting base just adds unnecessary weight and bulk to the camera. The hole it leaves in the camera body can be covered with tape to prevent dust from getting into the camera body. Replace the screw that holds the camera body halves together and we'll be ready to make an "adapter" to fit the microscope.

In an ideal and elegant world one could have a machinist make custom bushings and mounts to attach the camera to a microscope's trinocular port or to the second eyepiece on a binocular viewing head. Let's get real and practical, however! A simple, but adequate, adapter can be made witha black Kodak plastic film canister, a hot-glue gun, and a roll of masking tape! Cheap and effective, but definitely not elegant! LOL The black (only the black!) plastic film canisters in which Kodak packages a roll of 35 mm film has a flanged end that fits perfectly over the opening in the webcam where the lens used to sit. I cut the film canister just a little more than half length and used a hot-glue gun to glue the canister to the webcam. Don't be dumb, like I was the first time I did this, and glue over the seam between the two camera body halves!! LOL It makes it quite difficult to reopen the camera body in the future if you run the hot-glue over the seam! LOL After gluing the film canister to the camera body, simply wrap 1" wide masking tape around the microscope's trinocular port or around the second eyepiece tube on a binocular viewing head to the proper diameter to make a snug slip-fit of the film canister over the tape. Voile´, instant camera adapter!

Raw webcam image with internal infrared filter intact.

Okay. Why did I have you remove the webcam's built-in infrared filter? It was one of the criteria I used to choose a webcam. In my earlier attempts to use the webcam on the microscope my video clips had a bright hot spot that showed up in every video clip (see the image below). On top of that, the backgrounds were very unevenly colored. No amount of "fiddling" with the setup would remove that hot spot or even up the backgrounds. The example to the right is from one of the more extreme video clips. Whenever I perform any observations or photomicrography I religiously set the microscope's illumination to Kohler illumination. No changes made to the condenser position or changes in bulb focus would even out the background colors and eliminate the hot spot. The problem was its worst at lower magnifications but it still appeared at higher magnifications, too. This just about drove me nuts!



Raw webcam image with the internal infrared filter removed.

So, how did I finally resolve this issue? I had taken the webcam apart one day to clean out a large chunk of dust that was appearing in all of my video clips. I just happened to notice that the filter was tilted slightly in the lens assembly and that the filter was very, very reflective. The CCD array also had a very reflective dust cover over it. Perhaps this was causing some strong reflections of the exit pupil of the objective lenses? I decided to try the webcam without the filter. You can see below how much better are the results. I did, however, have to place infrared filters somewhere in the light path. CCD arrays are very sensitive to infrared. I scavenged a dichroic infrared filter from an old enlarger head and mounted it in the illumination path in the base of the microscope. I scavenged a second infrared filter from a broken slide projector and placed this heavy filter over the centering condenser. As you can see, the results are vastly improved. (Continue to Part III...)

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