When people hear optical prisms, probably the first thing that comes to their minds is Newton’s dispersion experiment. Since then, the optical prisms have come a long way. Today, they are fundamental components in various optical systems, playing a crucial role in manipulating light. If you are exploring optics or looking to choose optical prisms that match your requirements, this article serves as the perfect starting point.
Understanding Optical Prisms
Optical prisms are transparent optical elements with flat, polished surfaces typically made from glass, quartz, or plastic. They work on the principles of refraction and total internal reflection to manipulate the incoming light. The entering light gets bent due to the different refractive index of prism material and reflects off the internal surfaces until it exits.
The prisms have to be made with precise geometries to achieve the required effects and output images. The material, surface precision, and coating also affect the performance of the prism. A high quality prism would have a uniform refractive index, polished surfaces and anti-reflection coatings on input and output surfaces.
Let’s have a look at the different types of optical prisms based on their function.
Dispersion Prisms
Dispersion prisms separate the incident light into its components of different wavelengths visible as a spectrum of colors. The dispersion is due to the material’s index of refraction which dictates how much certain wavelengths deviate. The most common dispersion prisms are triangular prisms.
Reflection Prisms
Reflection prisms use reflection of light to rotate, flip, deviate, displace or invert the image. These prisms utilize total internal reflection with minimal loss of light to produce high-quality results when the angle of incident light is oblique enough.
Reflection prisms come in different shapes that decide the number of reflections of light which also controls the orientation of the output image. When the light is reflected an odd number of times, the image gets flipped. On the other hand, an even number of reflections result in an upright image which may also be rotated. Dove prisms, porro prisms, amici prisms, etc. are some of the reflection prisms.
Rotation Prism
Rotation prisms are used to rotate light by 90° or 180° using total internal reflection. These prisms can be used to view images from different angles without manually changing the object orientation.
Displacement prisms
Displacement prisms change the angle of the light in relation to the normal while maintaining the direction of the light. These prisms use refraction instead of total internal reflection.
Applications of Prisms
Some of the major applications of prisms are in imaging and scientific research,
Imaging systems: Prisms are used in imaging systems for better focusing of light, avoiding stray light, rotation of images and reducing the size of the imaging system.
Spectroscopy: Spectroscopic instruments rely on prisms for the primary task of dispersion that allows the analysis of material composition from the reflected light. Spectroscopy is used for chemical analysis as well as astronomical research.
LASER systems: Prisms are vital in laser systems as they help in beam steering without requiring complex mechanical systems. They can also compensate for refraction in other optics in the system to ensure the beam is focussed and aligned.
Optical prisms have become an integral part of optical systems that are crucial for modern society and scientific research. When used accurately, they can make a huge difference in the quality of the results. Equipped with the understanding of prisms, you can make a better decision for your specific requirements.
