Note that almost all modern microsopes use the Siedentopf design, rather than pure lateral translation to affect the interpupillary distance.
Two basic types of head exist - ones that invert the image, and ones that don't. The ones that don't are particularly handy when trying to work on the specimen, with a micromanipulator, for example.
The Diaphot TMD has a permanently attached head, but that is OK since it is quite capable out of the box. The head itself has a four position turret, just below the eyepieces, allowing normal viewing, magnified viewing for focusing, blocking the eyepieces for time-lapse photography, and a focusable Bertrand lens for Köhler illumination aligment as well as phase contrast annulus and Hoffman modulation alignment. It comes stock with a binocular head and two camera ports, so it is essence a quadnocular system. Visible in the photo is the front camera port, with an F-Mount for an SLR body to directly attach.
The Eclipse series has a removable binocular or trinocular head. They of course have the appropriate 200 mm focal length tube lens for the CFI60 infinity corrected optics. Here, the binocular version has set-screws to keep the eyepieces from rotating, if desired. It features 30 mm sleeve diameters, rather than the 23.2 mm otherwise used. Oddly, the trinocular version I have doesn't allow use of the 30 mm eyepieces. This particular trinocular head doesn't have provision for simultaneous use of the eyepieces and camera, which is typically a 20% eyepiece and 80% camera split - it is all or nothing 100/0 to the camera. It should be noted that while the Labophot/Optiphot heads can actually fit on an Eclipse, the parfocal nature (each objective is nearly at the same focus) is lost.
The Model S trinocular head (at least the one I have) is equipped with a built in polarizer that can be rotated into place. It also has eyepieces that have pure lateral translation for the interpupillary distance.
The Labophot / Optiphot series has several choices, especially once you get into the trinocular, as well as teaching heads that allow multiple binocular attachments. Even with the binocular heads shown below, there are two varieties.
Next, we have one with a nice inverting telescope inside with an eyepiece for direct viewing, or I suspect a camera could be attached on top with the appropriate adapter.
Here we have a Type "T" without a slider. There is a partially silvered mirror which is over half of the aperture, as seen below.
And finally, there are "ergonomic" heads, both binocular and trinocular, which allow the microscopist to tilt over a large range for optimum comfort.
for navigation!