Roof Prisms, With the Roof Angle Held in Arcseconds
Kingsview Optical makes custom roof prisms, including Amici and roof penta prisms, for sights, telescopes, viewfinders and imaging systems. The 90° roof is the face that makes or breaks a roof prism, and we hold it to better than 10 arcseconds, then coat and measure every prism at our site in Rye.
- Made in Rye, East Sussex
- Roof angle better than 10″
- Coated in-house
- ISO 9001:2015
What a Roof Prism Does
In short: a roof prism replaces one flat reflecting face with two faces at exactly 90° to each other, like the ridge of a roof. The extra reflection flips the image in the other axis, so a roof prism can turn a beam and keep the image the right way round in one part.
The most common type is the Amici roof prism: a right angle prism with a roof on its hypotenuse. It turns the view through 90°, as a right angle prism does, but delivers an upright, correct-handed image instead of a mirror image. That is why it is used in telescope diagonals, sights and image-erecting systems.
A roof penta prism adds a roof to a penta prism, combining a constant 90° deviation with a correct image. It is the prism in many camera viewfinders.
The roof angle must be very close to 90°. If it isn't, the two halves of the beam leave at slightly different angles and the image doubles. We hold the roof angle to better than 10 arcseconds, keep the roof edge sharp, and add a small protective chamfer where your design allows.
Where Our Roof Prisms Are Used
Roof Prism Specification
These are our standard tolerances. If your design needs tighter, tell us which parameter. We'll tell you plainly whether we can hold it, and what it adds to cost.
| Size range | 0.8mm micro prisms to over 100mm |
|---|---|
| Dimension tolerance | ±0.1mm |
| Angle tolerance | ±3 arcmin standard, tighter on request |
| Roof angle (90°) | Better than 10 arcsec |
| Roof edge | Sharp, or with a small protective chamfer to your drawing |
| Flatness | λ/4 @ 633nm |
| Surface quality (scratch-dig) | 60/40 standard, 40/20 on request |
| Materials | Schott, Ohara and CDGM optical glass; fused silica |
| Coatings | Broadband AR (standard 425 to 650nm, wider on request), wide-angle AR, V-coat, MgF2, custom designs; metal or dielectric mirrors where faces need them |
| Finishing | Blackened edges, protective chamfers, steps, bevels, drilled holes |
Not sure what to specify? The roof angle is the critical tolerance on any roof prism. The other angles can usually stay at our standard ±3 arcmin, which keeps cost down.
Made to Fit Your System
Roof Prism Questions
What does the roof on a roof prism do?
Why does the roof angle need to be so accurate?
What is an Amici roof prism?
Can you make roof penta prisms?
Do roof prisms need a protective chamfer on the roof edge?
What do you need to quote a roof prism?
Other Prisms We Manufacture
Or see our full optical prism manufacturing capability, and our optical design service if you need help choosing or designing a prism.
Getting a Quote for Roof Prisms
Send us your prism drawing. An engineer from the team that would make your prisms, not a sales team, will review it. They'll tell you plainly what's achievable and what will drive cost.
What to send
- Drawing (PDF or ISO 10110) with dimensions and angles
- Glass type, or the wavelength range if you're not sure
- Roof angle tolerance, plus other angle and surface tolerances
- Coating for each face and wavelength range
- Quantities: prototypes and expected production volumes
What happens next
- An engineer reviews itWithin one working day, flagging anything that will drive cost or lead time.
- We quote the prismFor the prototype, and for production at your volumes.
- We make, measure and deliverAll in Rye, with inspection data if you need it.
Need a Custom Roof Prism?
Send your drawing, or describe what the prism needs to do. We'll tell you plainly how we'd make it, what it will cost and how long it will take.
Made in Rye, East Sussex. NDA-friendly. Defence and security work welcome. ISO 9001:2015.