How does a Porro prism differ from a roof prism or simple right-angle prism?

Unlike a simple right-angle prism that provides a single 90° deviation, a Porro prism pair provides image erection (both vertical and horizontal) with minimal optical components and no roof edge. Compared to roof prisms, Porro prisms generally offer higher transmission and lower stray light for a given aperture because they avoid the tight roof angle tolerances and complex phase-correction coatings required in roof designs.

What are the main types or configurations of Porro prisms used in photonic instruments?

Common configurations include Porro Type I (orthogonal offset between input and output beams) and Porro Type II (co-linear input/output with lateral displacement), as well as cemented or air-spaced pairs. Variants may include tapered Porro prisms for beam expansion, precision Porro assemblies for interferometers, and customized geometries optimized for specific entrance pupil sizes and mechanical envelopes.

Which key specifications should I evaluate when selecting a Porro prism for my application?

Critical parameters include material (e.g., N-BK7, fused silica, CaF₂) for transmission range and thermal behavior, clear aperture, and dimensional tolerances (typically ±0.1 mm or better for precision assemblies). You should also review angular tolerances on the reflecting faces, surface quality (e.g., 20-10 scratch-dig), flatness (e.g., λ/4 @ 632.8 nm), and any required AR or reflective coatings on entrance/exit faces to match your wavelength band and damage threshold.

How do I compare different Porro prism products in terms of optical performance?

Compare specified beam deviation accuracy, image rotation accuracy, and wedge/tilt tolerances, which directly affect boresight stability and alignment error in your system. Additionally, evaluate transmission over your wavelength band (including coating performance), polarization effects from TIR, and any stated wavefront distortion to ensure the prism does not limit system MTF or interferometric contrast.

What typical lead times, customization options, and cost drivers exist for Porro prisms?

Standard catalog Porro prisms in common glasses and sizes often have lead times of 1–4 weeks, while custom materials, tight tolerances, or complex coatings can extend lead times to 6–12 weeks. Cost is driven mainly by material type, prism size, surface and angular tolerances, coating complexity (multi-band AR, high-laser-damage coatings), and any assembly requirements such as precision cementing or environmental sealing.

How can I find and compare Porro prism products on FindLight and request quotes without creating an account?

On FindLight, navigate to Optics → Prisms → Porro Prisms to filter products by material, wavelength range, coating type, clear aperture, and dimensional specifications. You can open multiple listings to compare datasheets side by side, then use the “Request Quote” or contact form on each product page to send technical requirements and RFQs directly to suppliers without registering or logging in.

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Porro Prims for Precision Beam Folding

Porro Prism

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Sold by: Union Optic Ships from: China

Specifications
Material:	BK7, UVFS
Dimension (Height):	12.7 mm
Dimension (Width):	12.7 mm
Dimension (Length):	12.7 mm

Did You Know?

The history of Porro Prisms dates back to 1854 when Ignazio Porro invented it. It is a type of reflection prism consisting of two prisms in an optical instrument to invert and reverse the orientation of an image by 180 degrees. Porro prisms are used in many optical viewing instruments, such as periscopes, binoculars, and monoculars. They are most often used in pairs, forming a double Porro prism. Double Porro prism systems are used in small optical telescopes to re-orient an inverted image. In many binoculars they both erect the image and provide a longer folded distance between the objective lenses and the eyepieces. The major difference between a roof prism and a Porro prism is that for the roof prism the roof edge is coplanar with the entrance and exit beam, while for a Porro prism the roof edge is orthogonal to the plane formed by the beams.

Related Resources

Frequently Asked Questions

A Porro prism is a right-angle prism assembly that inverts and reverts an image while deviating the beam path by 90° or 180°, depending on the configuration. It uses two internal total internal reflection (TIR) surfaces to rotate the image by 180° without additional mirrors, which is why it is widely used for erecting images in binoculars and other viewing systems.

Porro Prims for Optical Path Folding

Porro Prims are right-angle reflecting prisms used to fold optical paths, invert images, and provide lateral beam offset without changing beam diameter. On FindLight, Porro Prims are listed for procurement engineers and R&D teams who need compact, rigid solutions for multi-pass layouts and space-constrained optical systems.

Typical Specifications of Porro Prims

When evaluating Porro Prims, buyers usually focus on substrate, geometry, surface quality, and coatings. Common materials include UV-grade fused silica, N-BK7, or other optical glasses selected for transmission bands such as 350–2000 nm or 400–700 nm. Key dimensional parameters are leg lengths, prism height, and tolerance on angles (often ≤3 arcmin for precision units).

Surface quality for Porro Prims is frequently specified as 20-10 to 60-40 scratch-dig, with flatness on reflecting faces around λ/4 to λ/10 at 632.8 nm, depending on alignment sensitivity. Anti-reflection (AR) and high-reflection (HR) coatings are configured for specific laser lines (e.g., 532 nm, 1064 nm) or broadband regions. Damage thresholds, typically in J/cm² or kW/cm², are important for high-power laser applications.

Use Cases for Porro Prims

Porro Prims are deployed in:

Laser resonators and multi-pass amplifiers for path folding and compact cavity design.
Imaging systems requiring image inversion or displacement with high angular stability.
Rangefinders, binoculars, and telescopic assemblies needing robust, alignment-stable beam routing.
Metrology setups where Porro Prims provide controlled retroreflection and offset.

Buyer Guidance on FindLight

On FindLight, you can compare Porro Prims by substrate, spectral range, surface quality, dimensional tolerances, and coating design. Check datasheets for clear aperture, beam deviation error, and coating damage threshold to ensure compatibility with your laser wavelength, polarization, and power level.

For custom Porro Prims—such as non-standard leg ratios, special glasses, or unique AR/HR stacks—use the request-quote or contact options to reach suppliers directly. No registration is required to submit technical requirements, attach drawings, or ask for pricing and lead time tailored to your project.