What is a prism?

Prism, a transparent object surrounded by two intersecting planes that are not parallel to each other, is used to split or disperse light beams.

Prism is a polyhedron made of transparent materials (such as glass and crystal). It is widely used in optical instruments. Prisms can be divided into several types according to their properties and uses, such as right-angle prism, equilateral prism, Dowell prism, pentagonal prism, roof prism, dispersive prism and beam splitting prism.

Prisms can be used to bend light at a specific angle. Prism can not only deflect light, but also adjust the direction of the image. The design of the prism will be used to determine its interaction with light. When the light is incident on the prism, it will be reflected on a single surface or multiple surfaces and then emitted, or refracted when passing through the substrate.

1. Polarizing beam-splitting prism can polarize two perpendicular unpolarized light beams. Among them, P polarized light passes completely, while S polarized light reflects at an angle of 45 degrees, and the exit direction is 90 degrees with P light. Polarization beam splitting prism is formed by gluing a pair of high-precision right-angle prisms, and the hypotenuse of one prism is coated with polarization beam splitting dielectric film.

2. Right-angle prism is usually used to turn the light path or deflect the image formed by the optical system by 90. According to the orientation of the prism, the imaging can be consistent from left to right, upside down and different from left to right. Right-angle prism can also be used for image synthesis, beam offset and other applications.

3. The prism is a transparent body with a triangular cross section. It is an optical instrument with a triangular cross section made of transparent material, and belongs to a dispersive prism. When polychromatic light passes through the prism, it can disperse polychromatic light.

4. Equilateral dispersion prism disperses a beam of light into different colors, which is used in spectral analysis experiments and instruments. When a beam of light is obliquely incident on the first surface, because the refractive index of glass is related to the wavelength, different colors of light are refracted at different angles, so a spectrum appears on the other surface.

5. Doyle prism is an image rotator. After the light passes through this prism, the image is inverted 180. In addition, when the prism rotates around its optical axis, the rotation angle of the image is twice that of the prism. Generally speaking, Dowell prism uses the principle of critical angle to realize total internal reflection, so its field of view is limited. At the same time, it is also important to keep the reflecting surface clean and use parallel light.

6. Pentagonal prism is one of the steering devices with fixed angle (90) of light beam. It has two purposes: first, no matter what the incident angle on the first surface is, the outgoing light will turn the incident light to a certain angle (90); Secondly, unlike right-angle prism, the image it forms has neither rotation nor specular reflection. Pentagonal prism is often used in camera viewfinder, image observation system or measuring instrument.

7. Two mutually perpendicular reflecting surfaces are called the roof surface, and the prism with the roof surface is called the roof prism. Roof prism is small, which can make the objective lens and eyepiece in a straight line, so it is often used in extremely compact binoculars. Without changing the optical axis direction and imaging direction of the main cross section, a reflection is added to make the total reflection times of the system change from odd to even, thus achieving the requirement of similarity between objects and images.

8. Paul prism, also known as Proprism, is a refractive prism used in optical instruments to modify the orientation of images. The light enters from the largest rectangular surface in the prism, undergoes total reflection on the inclined plane twice, and then exits through the original incident surface.