Specifications

Material: N-BK7, Grade A Fine Annealed
Angular Tolorence: ±3 arcmin
Surface Quality: 40-20 Scratch-Dig
Surface Flatness: λ/10

Applications

Binoculars
Spotting Scopes
Prism Diagonals in an Optical System
Optical Tooling

Thorlabs' Roof Prism, is made from N-BK7, a RoHS complient version of BK7, and can be used when a right angle deflection of an image or laser beam is required. In passing through the prism, the image is both deflected right-to-left and top-to-bottom. The hypotenuse of the prism utilizes total internal reflection (TIR) to reflect the image through the prism.

For custom sizes or optional anti-reflection coatings, please email us or contact Tech Support.

Please refer to the Selection Guide tab above for assistance in selecting the appropriate prism for your application.

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Dimensions

Item #	PS951
A	18 mm
B	23 mm
Clear Aperture	15 mm

Selection Guide for Prisms

Thorlabs offers a wide variety of prisms, which can be used to reflect, invert, rotate, disperse, steer, and collimate light. Prisms are available in N-BK7, UV Fused Silica, F2, N-SF11, α-BBO, N-KZFS8, Ge, and CaF₂. For prisms and substrates not listed below, please contact tech support.

Beam Steering Prisms

Prism	Material	Deviation	Invert	Reverse or Rotate	Applications
Right Angle Prisms	N-BK7, UV Fused Silica, Germanium, or Calcium Fluoride	90°	90°	No	90° reflector, independent of entrance beam angle. Used in optical systems such as telescopes and periscopes.
Right Angle Prisms	N-BK7, UV Fused Silica, Germanium, or Calcium Fluoride	180°	180°	No	180° reflector, independent of entrance beam angle. Acts as a non-reversing mirror and can be used in binocular configurations.
Retroreflectors and Mounted Retroreflectors	N-BK7	180°	180°	No	180° reflector, independent of entrance beam angle. Beam alignment and beam delivery. Substitute for mirror in applications where orientation is difficult to control.
Penta Prisms and Mounted Penta Prisms	N-BK7	90°	No	No	90° reflector, without inversion or reversal of the beam profile. Can be used for alignment and optical tooling.
Roof Prisms	N-BK7	90°	90°	180^o Rotation	90° reflector, inverted and rotated (deflected left to right and top to bottom). Can be used for alignment and optical tooling.
Dove Prisms and Mounted Dove Prisms	N-BK7	No	180°	2x Prism Rotation	Dove prisms may invert, reverse, or rotate an image based on which face the light is incident on. Prism in a beam rotator orientation.
Dove Prisms and Mounted Dove Prisms	N-BK7	180°	180°	No	Prism acts as a non-reversing mirror. Same properties as a retro-reflector or right angle (180° orientation) prism in an optical setup.
Wedge Prisms	N-BK7	Models Available from 2° to 10°	No	No	Beam steering applications. By rotating one wedged prism, light can be steered to trace the circle defined by 2 times the specified deviation angle.
Wedge Prisms	N-BK7	Models Available from 2° to 10°	No	No	Variable beam steering applications. When both wedges are rotated, the beam can be moved anywhere within the circle defined by 4 times the specified deviation angle.
Coupling Prisms	Rutile (TiO₂) or GGG	Variable*	No	No	High index of refraction substrate used to couple light into films. Rutile used for n_film > 1.8 GGG used for n_film < 1.8

* Depends on angle of incidence and index of refraction

Dispersive Prisms

Prism

Material

Deviation

Invert

Reverse or Rotate

Illustration

Applications

Equilateral Prisms

F2, N-SF11, Germanium, or Calcium Flouride

Variable*

Dispersion prisms are a substitute for diffraction gratings.

Use to separate white light into visible spectrum.

Pellin Broca Prisms

N-BK7, UV Fused Silica, or CaF₂

90°

Ideal for wavelength separation of a beam of light, output at 90°.

Used to separate harmonics of a laser or compensate for group velocity dispersion.

Dispersion Compensating Prism Pairs

Fused Silica, CaF₂, SF10, or N-SF14

Variable Vertical Offset

Compensate for pulse broadening effects in ultrafast laser systems.

Can be used as an optical filter, for wavelength tuning, or dispersion compensation.

* Depends on angle of incidence and index of refraction

Beam Manipulating Prisms

Prism

Material

Deviation

Invert

Reverse or Rotate

Illustration

Applications

Anamorphic Prism Pairs

N-KZFS8 or N-SF11

Variable Vertical Offset

Variable magnification along one axis.

Collimating elliptical beams (e.g., laser diodes)

Converts an elliptical beam into a circular beam by magnifying or contracting the input beam in one axis.

Polarization Altering Prisms

Prism	Material	Deviation	Invert	Reverse or Rotate	Applications
Glan-Taylor, Glan-Laser, and α-BBO Glan-Laser Polarizers	Glan-Taylor: Calcite Glan-Laser: α-BBO or Calcite	p-pol. - 0° s-pol. - 112°*	No	No	Double prism configuration and birefringent calcite produce extremely pure linearly polarized light. Total Internal Reflection of s-pol. at the gap between the prism while p-pol. is transmitted.
Rutile Polarizers	Rutile (TiO₂)	s-pol. - 0° p-pol. absorbed by housing	No	No	Double prism configuration and birefringent rutile (TiO₂) produce extremely pure linearly polarized light. Total Internal Reflection of p-pol. at the gap between the prisms while s-pol. is transmitted.
Double Glan-Taylor Polarizers	Calcite	p-pol. - 0° s-pol. absorbed by housing	No	No	Triple prism configuration and birefringent calcite produce maximum polarized field over a large half angle. Total Internal Reflection of s-pol. at the gap between the prism while p-pol. is transmitted.
Glan Thompson Polarizers	Calcite	p-pol. - 0° s-pol. absorbed by housing	No	No	Double prism configuration and birefringent calcite produce a polarizer with the widest field of view while maintaining a high extinction ratio. Total Internal Reflection of s-pol. at the gap between the prism while p-pol. is transmitted.
Wollaston Prisms Wollaston Polarizers	Calcite	Symmetric p-pol. and s-pol. deviation angle	No	No	Double prism configuration and birefringent calcite produce the widest deviation angle of beam displacing polarizers. s-pol. and p-pol. deviate symmetrically from the prism. Wollaston prisms are used in spectrometers and polarization analyzers.
Beam Displacing Prisms	Calcite	2.7 or 4.0 mm Beam Displacement	No	No	Single prism configuration and birefringent calcite separate an input beam into two orthogonally polarized output beams. s-pol. and p-pol. are displaced by 2.7 or 4.0 mm. Beam displacing prisms can be used as polarizing beamsplitters where 90^o separation is not possible.
Fresnel Rhomb Retarders	N-BK7	Linear to circularly polarization Vertical Offset	No	No	λ/4 Fresnel Rhomb Retarder turns a linear input into circularly polarized output. Uniform λ/4 retardance over a wider wavelength range compared to birefringent wave plates.
Fresnel Rhomb Retarders	N-BK7	Rotates linearly polarized light 90°	No	No	λ/2 Fresnel Rhomb Retarder rotates linearly polarized light 90°. Uniform λ/2 retardance over a wider wavelength range compared to birefringent wave plates.