Polarized light microscopes often also referred to as petrographic microscopes, asbestos microscopes, crystal microscopes, forensic microscopes, polymer microscopes, ore microscopes, and more, utilize the contrast-enhancing technique known as polarized light to improve image contrast and quality, especially on samples containing anisotropic or birefringent material. Polarizing microscopes are often called petrographic microscopes since their main application is in studying rocks and minerals under polarized light. The study of optical mineralogy uses petrographic microscopes to produce polarized light for analysis and identification of rock and mineral thin sections on microscope slides. All of our microscopes have the full Bertrand lens system, complete with a polarizer and an analyzer. Cross polarization can be obtained with our polarized light microscopes by turning the polarizer and the analyzer at 90 degrees to each other, which is the extinction angle. Polarized light microscopy positions two polarizing filters, called polarizers, in the light path.
The polarizing filters are very similar to those found on polarizing sunglasses. Ideally, both polarizers will be rotatable. One polarizer is positioned before the sample, and the second called the analyzer is located between the back focal plane of the objective and the eyepieces or camera. At this extinction angle, most light transmission is blocked by the polarized filters. A polarized light microscope set at the extinction angle is able to view thin sections of birefringent specimens and see stunning coloration. Polarized light is used in a variety of applications and for many different types of samples. Polarized light is very popular in geology, mineralogy, and crystallography, but it has also found a home in forensic science, food science, ceramics, metallurgy, polymer science, pharmaceuticals, asbestos identification and more. Polarized light can be found on upright and inverted microscopes and it can be used with transmitted or reflected illumination. Polarized light is needed in order to use Differential Interference Contrast (DIC), and it provides some of the most beautiful, colorful, widely used images in all of science.
Most polarizing microscopes produce only transmitted polarized light. This means they provide light from the bottom and it transmits through the thin section of birefringent specimen on a microscope slide. Some polarizing microscopes also have the capability for incident reflected polarized light using epi illumination through the objective lens. These microscopes are commonly known as ore microscopes since they view thick polished specimens of rocks and minerals. The rock ore is polished and only the top surface is viewed. Since the ore is thick, it is opaque and no light is transmitted through it. The ore microscope applies incident polarized light to the specimens surface which is reflected back into the microscope objective to be viewed in the eyepieces. Applications for polarized light microscopes include rock and mineral identification, medical applications such as in viewing microscopic crystals in urine, biochemistry and biomedical research, studying meteorite thin specimens, identifying asbestos with a dispersion staining objective, geology and geological engineering, and in the petroleum industry.