What Type of Microscope do I Need?

Welcome to our website, TrueVision Microscopes .com. We sell microscopes but we also strive to provide useful information to our customers about microscopes. The intent of this microscopy article is to discuss various types of microscopes. There are many kinds, styles, manufacturers, and models of microscopes. We attempt to sort out the confusion by providing this microscopy primer - beginner’s guide to types of microscopes. It is a general guide and is not based specifically on our product line.

In order to better understand the type of microscope needed for a particular application, we’ve compiled this list of various types and typical applications. Let’s first look at the most basic types of microscopes and segregate them. A monocular microscope has only one eyetube, and is usually found on the cheaper student high power compound light microscopes. A binocular microscope has two eyepieces. This is better as both eyes can view the specimen. It also costs more. All stereoscopic microscopes must have two eyepieces. High power compound microscopes may be have one or two eyepieces. There is also a trinocular microscope. The third eye is really a camera photography port. It is usually on the top of the head and provides a means for attaching cameras or video equipment to the microscope.

High Power Compound Light Microscope: This type of microscope does just what it says. It is for high power magnification. Specimens viewed under it are generally put on microscope glass slides, and a thin cover slip placed over the specimen. Typical specimens may be thin tissue samples, blood cells, bacteria, parasites, stool samples, semen specimens for fertility testing, and other tiny stuff. The compound microscope generally has several objectives on a rotating turret to change magnification. Common microscope objective powers are 4x, 10x, 20x, 25x, 40x, 63x, 80x, and 100x. Final “compounded” magnifications are the multiplication of the objective powers times the eyepiece power. Most viewing is done under a 10x eyepiece. So 100x objective yields a 1000x power magnification with the use of 10x eyepieces. Higher power microscope eyepieces can be used, such as 12.5x, 15x, 16x, and 20x. However, the best optical viewing is going to be done under a 10x eyepiece. A light microscope has a practical limit of about 1200x magnification, even with the best grade lens and optical system. Don’t let others tell you they can give you “thousands of power” magnification. That is empty resolution. Many dealers of live blood cell microscopes like to promote their equipment as being able to give 10,000x or more magnification. It sounds great, but just isn’t true. This is done in video microscopy where the image is taken out to a viewing screen such as a monitor. Imagine watching a science biology show and seeing a red blood cell on the television. If it’s on your home television, then maybe you’re at 5000x or more. Now, imagine going to a drive-in movie theater (try finding that now!) and seeing it on a 14 foot screen. You may be in the millions of power magnification there. So which is better? Well, really neither. They are the same. It’s the same image, just taken to different end screens. A microscope camera or a human eye looking into the eyepiece can only pick up so much resolution from the optical system. The reason is the resolving power of the microscope objective has limits. It can only show so much. Factors for limits of a microscope’s resolving resolution include the wavelength of the light incident on the specimen, the numerical aperature of the microscope objective, and the medium between the glass lens of the microscope objective and the top of the cover slip (air, but in oil immersion lens, it’s immersion fluid). A more detailed analysis of microscopy magnification limitations is not for this article. But now, you know not to believe the wild marketing ploys from some microscope dealers.

Let’s take a look more at versions of the high power compound light microscopes, because this type of microscope can be broken down into several subcategories of optical instruments.

Student Compound Microscope: The lower cost, student microscopes may only have 3 objectives, with 40x being the highest. Common objectives for a home school compound microscope are 4x, 10x, and 40x. They generally have only a basic light condenser, such as a dial aperature with simple holes of various sizes for the light to go through for illumination control. Often, they are not variable intensity. And they often have only a cheap incandescent microscope bulb instead of a halogen bulb. The halogen bulb is more costly and requires a transformer to reduce the voltage to 12V or sometimes 6V. The halogen illumination is very intense and provides excellent lighting for a microscope specimen. A cheap incandescent bulb is a filament type bulb that has the full voltage across it, just like a common household bulb would have. Student microscopes may also be labelled as having higher power magnifications, but usually their 100x objective will be so poor that 1000x magnification is difficult to view.

Clinical Research Compound Microscope: A research laboratory, medical clinic, or veterinary clinic will generally need the 100x oil immersion objective for viewing the smallest of specimens including blood cells, spermatozoa, bacteria, blood parasites, cancer, and diseased tissue.

So that’s a good review of compound light microscopes. Let’s now review the next type of microscope:

Low Power Stereoscopic Microscope: This type of microscope has a much lower magnification. It also uses two independent light paths to the microscope objective. This provides a stereoscopic effect that allows for 3D viewing and depth perception. A compound microscope splits the image with a beam splitter to the two eyepieces in a binocular microscope. But a stereo microscope has two objectives picking up the image, and going all the way to the eyepiece. Typical magnifications are from 7x to 45x, and up to 90x with the use of 20x eyepiece sets.

Let’s further break down the type of low power stereo microscope.

Stereo Zoom Microscope: This is a type of low power microscope that has zoom optics. Zooms often go from 7 to 35x and sometimes up to 45x. In some high zoom ratio stereo microscopes, the magnification may go to 65x with the standard 10x eyepiece set. In any case, the zoom provides exceptional ease of viewing the specimens since all it takes is simply turning the zoom knob to see more or less magnification. It’s a continuous zoom, not in fixed increments of magnification. The zoom optics does cost more.

Fixed Magnification Stereo Microscope: This type of low power microscope has a fixed magnification range. Typically, there is a turret under the head that switches from a pair of 1x objectives to a pair of 3x objectives. That would give 10x and 30x magnification with 10x eyepieces in place. It may also be 2x/4x, giving 20x/40x magnification. Remember that simply changing the eyepiece set to 20x eyepieces will double the magnification of the microscope.

The stereo type of microscope can also include portable field microscopes for nature study or even fire investigation work. These are low power stereoscopic microscopes, often with battery illumination.

Another type of stereo microscope is the boom mounted microscope. But really, this is just the typical stereoscopic microscope head placed on a boom stand instead of an upright lighted base. The boom gives more flexibility in working area and the ability to swing the microscope over a specimen, then out of the way.

Now, it’s time to review the more specialty microscopes. There are many kinds and types of these microscopes. Their applications vary significantly and so do their designs.

Tissue Culture Microscope: Also known as a cell culture microscope, this type of microscope is inverted, meaning the objectives face upward. It is used for looking at the bottom of a Petri dish or flask and viewing living cell cultures inside. The objectives are below the stage and face upward to view the bottom of the Petri dish. These are often used in microbiology labs.

Fluorescence Microscope: This type of microscope can be either inverted or upright. In either case, it provides a dichroic filter cube containing both an excitation fluorescence filter and an emission fluorescence filter. It also contains a mercury lamp source for high intensity illumination, usually at 100W. The principle of this type of microscope is that the mercury light source creates light that is passed through the excitation filter. The excitation filter is a narrow bandpass filter allowing only a small range of light wavelengths to pass. The light is then incident on the specimen. The specimen, in turn, is fluorescent, so it fluoresces because of this light. The fluorescing light is picked up by the fluorescent objective and passed through the emission filter in the cube. This is another filter that allows only a certain desired wavelength of light to pass. The light that passes then goes to the microscope eyepieces for the microscopist to view the end result which is the fluorescing of the biological specimen. This type of microscope is very expensive and is used in microbiology, molecular biology, and medical research. For example, living cells in a tissue specimen will have a different way of fluorescing than dead cells. So cancer cells and normal cells can be compared.

Forensic Science Comparison Microscope: This type of microscope is used by crime labs for comparison of bullet casings, firing pins, ballastics, hair samples, paint flakes, and fibers. It consists of two microscopes mounted together with a special comparing bridge. The microscope can be either a high power compound or a low power stereoscopic microscope.

Polarizing Microscope: This type of microscope is also called a geological microscope or petrographic microscope. It has polarizing light that is polarized twice. It has an initial polarizer that creates plan polarization of the light entering the microscope. It then has an analyzer, which is another polarized filter, that is located in the head of the microscope. The analyzer can be rotated so that the planes of polarization can be crossed, a condition called cross polarization, or cross nicols. This creates allows special optical characteristics of birefringent rock and mineral (petrographic) specimens to be viewed so identification can be made. These types of microscopes have a Bertrand lens and usually three compensator plates (mica, gypsum, and quartz). The normal polarizing microscope does transmitted light polarization. If the microscope also has reflected light polarization, then it is called an Ore microscope. The ore microscope has an upper reflected light source so the light can be polarized, then brought incident to the specimen, such as a thick polished rock sample. Only think rock and mineral samples can be viewed under a transmitted polarized light microscope as the specimen must be thin enough to allow light to pass.

Surgical Microscope: This type of microscope has a stereoscopic microscope head, sometimes with zoom optics and sometimes without. It usually is mounted to a mobile floor stand with articulating arm. It can be used for ophthalmic eye surgery,