Intermediate
Eleshop sells a number of popular stereo microscopes like the SM-4TP. A stereomicroscope has two lenses and two eyepieces, one for each eye. Affordable stereomicroscopes (up to € 10000) are built according to the Greenough principle (named after the inventor in the 19th century).
Notable is the angle in which the lenses are positioned in relation to the object being examined (a printed circuit board is shown below). The brain combines the image information of both eyes, thus creating a 3D image. This principle is shown in the drawing below.
As you can see, the angle relative to the object under study is not completely straight. Our brain is smart enough to compensate for this making it possible to see the complete object not only in 3D but also sharply.
As soon as we start looking at it with a camera, it becomes a different story. Microscopes can magnify substantially, which means the depth of field (DOF) is very small. In other words, you can focus on a certain part of the object, but that does not mean that everything of the object can be in focus at the same time.
The drawing above shows how the image of one of the optical paths is split off with a prism to the camera port. Using a CCD adaptor , a C-mount camera is mounted, like this popular HDMI camera with Sony sensor. This camera sees only the image of one of the two lenses and does not see the object under study completely flat. As a result, especially when zooming in significantly, it will not be possible to take a picture where everything is in focus.
Should this still be desirable, one may choose to temporarily place the object under study at the same angle as the lens. The drawing above shows this. This should then only be done for the photograph, because at this angle it is obviously not possible to study the object with both eyes still.
