Microscope C-Mounts and Image Sensors

A microscope c-mount adapter is used to connect a microscope camera to the microscope trinocular port. A c-mount adapter has a standard 1" (or 25mm) diameter male thread. This thread matches with the female thread on the camera. C-mount adapters are microscope specific in that the lenses are made to match up with your specific microscope. For example, you would not want to use an Olympus C-Mount adapter on a Meiji microscope. This would most likely result in an image that is not parfocalled, or is not in focus at the same time that your eyepieces are in focus. C-Mount adapters have lenses in them in order to match up with the similar magnification you are seeing through the eyepieces. If you were to use a c-mount adapter with no lenses built into it you would see more magnification than what the eyepieces are currently seeing. This is due to the inherent magnification with image sensors and microscopes. Although this setup can work, most people generally prefer an image that looks similar to their field of view through the microscope.


Matching Chip Size with C-Mount Adapters

To compensate for too much magnification at the camera, or to most closely match the field of view in the microscope, you will need a c-mount adapter with a reduction lens built into it. The chart on the right lists the suggested adapter to use when using 10x eyepieces in your microscope, based on the chip size in the camera.

Camera Chip
Suggested
C-Mount
1/4"
0.265x or 0.3x
When using 20x eyepiece you will generally move up one step in magnification. If you had a 1/2" chip with 10x eyepiece the corresponding c-mount would be 0.45x or 0.5x. With 20x eyepieces you would want to use the 0.7x c-mount adapter.
1/3"
0.3x
1/2"
0.45x, 0.5x or .6x
If you were to use a camera with a 1/2" chip in it with a 0.7x c-mount adapter the camera would still work, you would just have a smaller field of view and more magnification at the camera than you would see through the eyepieces.
1/1.8"
0.45x, 0.5x or .6x
2/3"
0.7x

Image Sensors

Image Sensor Size Images

Cameras have image sensors that are fairly small. The most common image sensor sizes are shown at left. The smaller the sensor, the more inherent magnification. The larger the camera sensor, the better the resolution will be with less magnification.

Image resolution is key in most microscopy imaging applications and therefore 1/2" and 2/3" chip cameras usually offer a good balance between magnification, resolution and the size of the actual image the camera is viewing.