There are 3 important brands: Olympus, Leica and Zeiss… Leica and Zeiss, have very nice optics, but are also more expensive.
For emulsion observation it is quite important to equip the microscope with polarizers
to observe liquid crystalline phases, and a hot stage can be useful too.
Differential interference contrast filter (DIC) is also a good option to
increase the contrast of your images
If you need to take images, there are many cameras, and
price vary a lot.
Image processing software can be useful if you want to
determine the droplet size distribution.