Optical prism : a complete guide

Most of us remember the famous rock band Pink Floyd’s “Dark side of the moon” album  cover showing a light beam been diffracted in a “rainbow” through a triangular prism. That is a very good summary of how light beam travel through a prism, below you’ll find a complete guide to look further in optical prisms.

What is a optical prism ?

Definition

An optical prism is a bloc of optical material cut in geometrical shape for the specific purpose of modifying the incident light beam by affecting it’s direction, rotational angle or diffraction.

In optical systems they are used to turn a signal or separate the signal according to it’s wavelengths.

Specifications

Many different optical materials can be used to manufacture a prism, depending of the type of prisms and the wavelength range they will be used in. We are providing optical prisms with :

  • Optical glass : B270, H-K9L / NBK7, F2, N-SF11
  • Fused silica
  • IR material : CaF2, BaF2, MgF2, Silicon, Ge
  • Sapphire
  • Many other references

Below table shows the typical specifications / tolerances for optical prism manufacturing :

Specification Detail Age
Dimensional range 0,3mm to 300mm 50
Dimensional tolerances +/- 0,1mm (normal) or +/-0,05mm 94
Surface flatness up to Lambda /10 80
Surface quality S&D 40/20 80
Angle tolerance up to +/- 1 arcmin 80

Prisms can be coated, AR to reduce signal reflection on the surface or Reflective coatings to enhance the signal reflection at specific wavelengths.

Different types of optical prisms

Type of prism Description Usage Image
Right angle prism Prism with a right angle triangular cut shape with both sides opposite to the hypotenuse of equal dimension. They are used to deviate a light path to 90° or 180° by TIR (Total Internal Reflection) Optical prism wtih AR
Penta prism Prism with a pentagone cut shape, with specific angles. Penta prisms are used to redirect a signal by 90° without inverting nor reversing the image. prism-with-coating
Retroreflector Round base prism with three face pyramidal sphae. Return the light 180° even without alignment of the incident light and the retroreflector. Used in topograply and other applications. optical retro reflector prism
Dove prism Parallalelepiped which correspond at a truncated right angle prism. Rotate the image with no deviation of the beam. The rotation angle is equal to twice the prism rotation compare to the incident beam. optical prism
Roof prism Roof shaped prism. Used to deviate the signal at 90° while inverting it. Optical prism manufacturing | Optical component
Equilateral prism Prism made of high diffractive Abbe number glass in a shape of an equilateral triangle. Used to disperse the light with different angles for each wavelength. (think of the Pink Floyd album cover).
Pellin Broca prism Quadrilateral prism with angles of 90°, 75°, 135° and 60°. Deviate the light by 90°, used in spectroscopy and for harmonic separations. optical CAF2 prism
Wedge prism Prism made of a plan surface and and other tilt surface. Used to deviate light signal (mostly for laser beams) optical wedge prism
Micro prism Prism with dimensions between 0,3 and 3mm of side. Used in optical fiber sysems and endoscopy. reflective coating of 3mm glass cube
Glued prism Assembly of custom prism made by gluing / cementing, can include air space in between parts. Custom made to fit customer applications. custom glued prism

Prism manufacturing

The process of manufacturing a prism will usually follow below steps:

  1. Raw material bloc cutting.

    glass prism cut into shape

    Cutting glass prism into shape.

  2. Fine grinding and polishing of the optical surfaces.

    prisms glued together to be polished

    Cluster of prisms glued together to prepare polishing

  3. Final cutting to shape
  4. Cleaning in ultrasound bath.

    post production optical prism cleaning

    Underwater ultrasound cleaning of optical prisms.

  5. Eventual surface treatment application.

    coating device for prism optical surface treatment

    Optical coating device.

The prisms can be further assembled either cemented with other optical elements or assembled in opto-mechanical parts.

custom glued prism

Two prisms cemented together with air gap in between and black varnished sides.

Where to buy optical prism ?

If you are looking for prisms to be used in optical application, you should look for precision optics suppliers, with experience in the optical material you are looking for.

Please note that as you can notice above in the description of the manufacturing process, optical prisms can be manufactured in parallel, for almost each step, therefore order quantities are a key point in manufacturing cost valuation.

Prepare all the below information :

  • Material
  • Technical drawing
  • Coating request
  • Expecting quantities

And then send your request to your favorite precision optics supplier. By click on the below you can contact SINOPTIX directly for your request.

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