Connecting Cameras to Microscopes
The connection of camera to the microscope is very important to facilitate its functions and the processing to have accurate images as seen in the microscopic field. The detector element in electronic cameras is generally a rectangle or a square, regardless of the shape of the individual pixel sensors. If the camera has identical numbers of rows and columns of pixels, such as a 1000 x 1000 pixel camera, then the shape of the detector will be square. If there are more sensors in the horizontal direction than in the vertical, such as in a 1315 x 1035 pixel camera, then the detector will be rectangular. Remember that the field of view in the microscope is a circle. To properly match the camera, the circular image must be projected onto the camera detector in such a way that the entire surface of the detector sees image. Generally, the optical arrangement is chosen so the camera does not see all the way to the very edge of the microscope field of view, since most microscopes have marginal performance at the extreme edges of the field of view.
Assuming that the detector is rectangular and that it covers the field of view of the microscope image from side to side reasonably well, then there will be a larger area at the top and bottom of the field of view that is not covered by the camera.
This is exactly like the situation with film cameras, so there are no unusual requirements for aligning the electronic camera field of view with the microscope. What is different is that the size of the detector in the electronic camera is quite different in size as compared to film in a film camera. As an example, a 35 mm camera actually takes a picture that is 24 mm high by 35 mm wide. In contrast, the detector in most electronic cameras is either one half inch to three quarters of an inch in size. This means the physical arrangement of the electronic camera detector must be in a different location as compared to the film, or a different lens must be used in the camera adapter. It is critical that a correct mount be used for the electronic camera, otherwise the image may not fill the detector, or the detector may see only a tiny area in the center of the image. A good test of any electronic camera attached to a microscope is to select an object that can be seen in a specimen through the microscope, and then move it around in the field of view, and see when it disappears from the view of the electronic camera.
The great majority of electronic cameras attach to microscopes with a so called C mount. This is a threaded coupler that screws into the electronic camera. In general these devices are provided by the manufacturer of the microscope, and include any lenses necessary to adapt the camera to the microscope. Since there are differing sizes of detectors in electronic cameras, it is critical that the appropriate adapter be specified. Even though a C mount will screw into any C mount camera, a particular C mount adapter may not be optimal for a given camera. Microscope suppliers can provide additional information on this, or a third party supplier of optical mounts such as Diagnostic Instruments can provide appropriate mounts for essentially any camera-microscope combination. While on the subject of mounts, it should be mentioned that other mounts are found on some cameras. As the number of pixels in the detector goes up, the size of the detector device increases. Since this larger device may require a wider cone of light to see the full field of view, a larger diameter mount may be required.
