What is a Video Coupler?
Many microscopes have been purchased with a
trinocular port in the viewing head which was designed primarily for
mounting a camera. The current trend is to mount video cameras
for group viewing and for instant digitized images.
Thales Optem's line of Video Couplers can be segregated into Direct or
Standard and further categorized as a single magnification or
zooming. An added variation of the Standard permits the addition
of two viewing devices (e.g. 2 video cameras or a video camera and a
digital camera).
Ideally, one wants to place the camera sensor at the normal focal plane
of the output port of the microscope for maximum resolution.
Occasionally, that image is buried down inside a non-removable tube and
must be relayed to the outside, or the camera sensor is much smaller
than the available image and too much of the image data is wasted. In
this case a minification system is required. Refer to Tech Data
Camera Formats for information on camera format dimensions and
electronic magnifications.
Your first choice is "Direct or Standard?". The Direct series
places the sensor at the normal microscope image plane while the
Standard series relays the image to a secondary plane.
If you can use the Direct Series, it is the most cost effective, stable, and optically pure method of making the connection.
The Standard Series provides the means of overcoming mechanical
restrictions while allowing the superimposition of reticles on the
image. The zoom and multi-port couplers require the relay
technique.
The second choice is "which magnification or coupler to order?"
All camera sensors are smaller than the field of view of the normal
eyepiece, therefore, without optical assistance, a significant
portion of the image data will be lost. The above illustration
shows the change in percentage of an 18mm eye piece field captured on
the sensor as the magnification of the coupler is reduced. Think
of it as the coupler compressing the image seen through the
microscope's eyepieces to fit onto the sensor. As always, one
trades field of view for resolution.
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