Difference Between Polarizer and Analyzer

Main Difference – Polarizer vs Analyzer

Polarizers and analyzers are parts of optical instruments that use plane polarized light. There are many types of polarizers and analyzers that can be chosen according to our needs. A polarizer can filter light waves in order to generate polarization of light. In other words, a polarizer can generate plane polarized light from light waves coming from a normal light source. The analyzer acts as a second polarizer. Polarizers and analyzers are used in polarized light microscopy. Although both polarizers and analyzers are used as light filters, there are differences in their applications. The main difference between polarizer and analyzer is that polarizer produces plane polarized light whereas analyzer can be used to check whether the light has been polarized or not.

Key Areas Covered

1. What is Polarizer
      – Definition, Mechanism, Different Types
2. What is Analyzer
      – Definition, Mechanism, Different Types
3. What is the Difference Between Polarizer and Analyzer
      – Comparison of Key Differences

Key Terms: Analyzer, Plane Polarized Light, Polarization, Polarizer

What is Polarizer

A polarizer is a device that is used to polarize light waves. Polarizers are optical filters where light transmission depends strongly on the direction of polarization. Light with linear polarization is usually produced by these devices. The light waves from different directions (other than the selected direction) are absorbed or sent to a different direction in order to remove the interference.

Figure 1: A Wire Grid Polarizer

However, polarizers cannot convert light waves coming from any direction into the desired direction. Polarizers can only remove the unwanted light waves. There are several types of polarizers such as circular polarizers, crystalline polarizers, and linear polarizers.

For low-power applications, sheet polarizers are used. These sheets are made out of polymer materials which have been stretched into one direction. There, light waves of unwanted directions are strongly absorbed by polymers. Much higher optical powers can be handled by polarizing beam splitters. Here, other than absorbing, the light waves of unwanted directions are sent to other directions rather than the desired direction. Wire grid polarizers are another type of polarizers. These are made by fabricating very narrow metal strips on a glass substrate.

What is Analyzer

The analyzer is a device used to determine whether the light is plane polarized or not. It acts as a second polarizer. In microscopy, the analyzer is placed in the optical pathway between the specimen and the observation tubes. It is made up of a polarizing plate. The height of the polarizing plate (height from the specimen) can be adjusted.

Figure 2: Analyzer in Microscopy

Analyzer can be removed at will. When only the polarizer is used, a normal image can be observed. But when the analyzer is used along with the polarizer, an extinction of light occurs. If we are going to observe a birefringent (doubly refracting material) specimen, it will produce two individual light waves that have perpendicular polarizations. Then these light waves are passed through the analyzer. Here, these light waves are recombined causing a false color to appear. This is called interference color.

In addition, analyzer can be used to determine whether the light has been polarized or not by the polarizer. If the emergent light coming out of the analyzer is not changed when the analyzer is rotated, then the light is non-polarized. But if the emergent light is varied (from zero to maximum) when the analyzer is rotated, then the light is polarized.

Difference Between Polarizer and Analyzer

Definition

Polarizer: Polarizer is any device that can convert white light into plane-polarize light.

Analyzer: Analyzer is a device used to determine whether the light is plane polarized or not.

Polarization

Polarizer: Polarizer can make a light beam a plane polarized beam of light. 

Analyzer: Analyzer can also act as a polarization device but its main application is to detect whether the light has been polarized.

Placement in Polarizing Microscope

Polarizer: Polarizer is placed beneath the specimen.

Analyzer: Analyzer is placed above the specimen.

Movement

Polarizer: Polarizer can be rotated 360^o.

Analyzer: Analyzer can be moved in or out of the path of light.

Uses

Polarizer: Polarizer is used to polarize the light coming from a light source.

Analyzer: Analyzer can be used to determine whether the light is polarized or to determine whether the specimen is birefringent.

Conclusion

Polarized light microscopes are very useful in experiments such as identification of grout crystals, identification of asbestos fibers, predicting the history of rock formation, etc. A polarizer and an analyzer are two essential components for a polarized light microscope. Although both polarizer and analyzer act as light polarizing devices, there are differences between them. The main difference between polarizer and analyzer is that polarizer produces plane polarized light whereas analyzer is used to check whether the light has been polarized or not.

References:

1. “Polarized Light Microscopy.” Nikon’s MicroscopyU, Available here. Accessed 2 Oct. 2017.
2. Analyser. Optical Mine, Available here. Accessed 2 Oct. 2017.
3. Paschotta, Dr. Rüdiger. “Polarizers.” Encyclopedia of Laser Physics and Technology – polarizers, absorptive, polarizing beam splitters, birefringence, calcite, Glan-Taylor prism, Wollaston prism, thin-Film polarizers, 20 Feb. 2017, Available here. Accessed 2 Oct. 2017.

Image Courtesy:

1. “Wire-grid-polarizer” (CC BY-SA 3.0) via Commons Wikimedia
2. “275984” (Public Domain) via Pixabay