Penta Prisms for Stable 90° Beam Deviation

Did You Know?

Penta Prisms are designed to deviate a beam of light by a constant 90 degrees and due to this property can be used to define the right angles in optical systems. By definition, they are five sided prisms and are unaffected by slight movements. The perpendicular deviation is independent and insensitive of the precise alignment of the prism with respect to the incident beam or image. The two opposite transmitting faces are often coated with an antireflection coating to reduce spurious reflections
Read more in our Blog

Frequently Asked Questions

A penta prism is a five-sided prism that deflects an input beam by a fixed 90° angle regardless of small variations in the angle of incidence. Unlike right-angle or Porro prisms, the deviation is defined by the geometry, not by precise alignment, and image orientation is usually neither inverted nor reversed unless roof surfaces are introduced.

What Are Penta Prisms?

Penta Prisms are five-sided reflective prisms that deviate an input beam by a fixed 90° angle, independent of small angular misalignments of the prism itself. Unlike right-angle prisms, Penta Prisms maintain the 90° deviation without image inversion or reversal, making them useful for precise beam steering in optical systems.

Typical Specifications of Penta Prisms

On FindLight, Penta Prisms are available in common optical materials such as N-BK7, fused silica, and other optical glasses selected for low stress birefringence and defined transmission bands. Key specifications to compare include:

  • Dimensions: Aperture size and length (e.g., 5–25 mm) affecting clear aperture and mechanical integration.
  • Angle tolerance: Deviation accuracy (e.g., ±10–30 arcsec) and face angle tolerances for tight beam pointing control.
  • Surface quality: Scratch-dig (e.g., 20-10, 40-20) important for high-quality imaging and laser transport.
  • Surface flatness: Typically λ/4 to λ/10 at a reference wavelength, impacting wavefront distortion.
  • Coatings: Anti-reflection (AR) coatings on entrance/exit faces and metal or dielectric reflective coatings on internal faces to define transmission range and damage threshold.
  • Material properties: Refractive index, dispersion, transmission range, and thermal behavior relevant for broadband or high-power use.

Use Cases for Penta Prisms

Penta Prisms are used for beam steering in metrology setups, autocollimators, rangefinders, alignment telescopes, imaging systems, and laser pointing assemblies. Their fixed 90° deviation makes them suitable where mechanical tolerances are limited but angular accuracy at the output is critical. In laser systems, Penta Prisms can stabilize beam direction in alignment paths and diagnostic branches.

Buyer Guidance on FindLight

When sourcing Penta Prisms, first define the operating wavelength range and required beam diameter to select appropriate material, aperture, and coatings. Compare angle deviation tolerances and surface flatness for your pointing and wavefront requirements, especially in interferometric or precision imaging applications. For laser transport, verify coating type and damage threshold data for continuous or pulsed operation.

FindLight hosts multiple Penta Prisms from different suppliers, allowing side-by-side comparison of specifications, drawings, and coating options. You can request quotes directly from manufacturers for standard or customized Penta Prisms, adjust quantities, and inquire about tolerances or certifications. No registration is required to send RFQs, helping procurement engineers and R&D teams quickly evaluate alternatives and integrate these prisms into their optical designs.