What is a Trinocular Microscope?

Mary Elizabeth
Mary Elizabeth

A microscope produces an accurately enlarged image to allow the examiner to see things in a larger scale. It may or may not be capable of enough enlargement for the examiner to view cells. There are different ways of categorizing microscopes: by their purpose, by their construction, and by how one observes the specimens. In terms of viewing options, a microscope can be monocular, binocular, or trinocular, i.e., having one, two, or three eyepieces.

Scientist with beakers
Scientist with beakers

A trinocular microscope may be an optical, acoustic, or an electron microscope. In other words, it may be a microscope in which the specimen is illuminated by visible light, by sound, or by a particle beam of electrons. In addition, the third eyepiece may have been added to a binocular compound microscope or a stereo microscope. A binocular compound microscope uses one lens array for the objective but has a pair of eyepieces, with the light from the image formed by the objective split by a prism. A stereo microscope has two eyepieces, but also two objectives as well, so that the examiner’s view appears three-dimensional. In either case, the user taking advantage of the third lens on one of these two types of trinocular microscope will be provided with a monocular view.

A trinocular microscope may have one of several purposes. One purpose is to allow a second viewer access to a specimen at the same time as the person who is mainly using the microscope. This means that an instructor can, for example, look at what a student is seeing to answer a question or to check the accuracy of the student’s observations. In addition, the instructor can invite a student to share his or her view of an interesting specimen or when modeling how to adjust the focus, for example. This extends the instructional possibilities from the situation in which one person must not be viewing in order for the other person to have a view.

Another purpose of a trinocular microscope is to allow the use of technology to either preserve the images seen through the microscope by recording them or projecting them. In the first case, a digital camera or video camera could be connected to the third eyepiece, which may actually be designed as a port with this specific purpose. If it is not, there are adapters for some microscopes that can adapt a trinocular eyepiece meant for human viewing to a camera. Projecting an image has several advantages including allowing prolonged study without having to stay bent over the microscope itself, sharing images with others who are present in the room, or even sharing the image through a videochat or other means.

Mary Elizabeth
Mary Elizabeth

Mary Elizabeth is passionate about reading, writing, and research, and has a penchant for correcting misinformation on the Internet. In addition to contributing articles to wiseGEEK about art, literature, and music, Mary Elizabeth is a teacher, composer, and author. She has a B.A. from the University of Chicago’s writing program and an M.A. from the University of Vermont, and she has written books, study guides, and teacher materials on language and literature, as well as music composition content for Sibelius Software.

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My mom was a lab tech in a doctor's office, and I remember looking through the binocular microscope in the lab. She used to let me look at things like blood samples and so forth. I even learned how to do a white blood count from a slide! Those were the days when you had to do a lot of that stuff manually, and didn't send it off to a lab, or put it in a machine.

I saw a trinocular microscope in a medical supply catalog she had and thought it was really cool looking. I didn't wonder then what it was used for, but I do remember thinking it looked rather alien.


Our microscopes in high school were pretty good, but they weren't trinocular, that's for sure! They were better than average monocular, and I remember the teacher lamenting about how the fashion for wearing gobs of mascara would muck up the lenses, and how we had to be meticulous about keeping them clean. I didn't (and don't) wear mascara, so I didn't worry about it. I just worked up my findings.

The whole trinocular concept is a good one, though, especially from a technological standpoint. I always wondered how they took video or film of a microscope sample, and now I know!

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