Features

• Rotate and Invert an Image or Retroreflect Light
• Offered in Four Sizes: 5 mm, 10 mm, 15 mm, and 30 mm
• 15 mm Version Available in SM1-Threaded (1.035"-40) Mount for Easy Rotation

A Dove prism is used to rotate, invert, or retroreflect an image, depending upon the prism's rotation angle and the surface through which the light enters the prism. Thorlabs' Dove Prisms are fabricated from N-BK7 glass for high transmission from the visible to the near-infrared spectral range and available with 5 mm, 10 mm, 15 mm, or 30 mm square cross sections (see the Specs tab for more information on dimensions).

Dove prisms can be thought of as right-angle prisms with the triangular apex removed, which reduces the weight of the prism and stray internal reflections. They introduce astigmatism when used with converging light, so we recommend using them with collimated light. Additionally, these prisms affect the polarization state of light transmitted through them. See the Lab Facts tab for further details.

Image Rotation
Light is usually propagated along the longitudinal axis of a Dove prism. In this geometry, shown above, light reflects once from the bottom face, inverting the image on the other side. Rotation of the prism about the longitudinal axis rotates the image at twice the rate of the prism's rotation (see video above). For example, a 20° rotation of the prism results in a 40° rotated image.

Due to the high incidence angle, the light reflecting from the bottom face undergoes total internal reflection, even if the light's propagation axis and the prism's longitudinal axis are not exactly parallel. Hence, in a dove prism, the magnitude of the internal transmission is limited only by absorption.

Retroreflection
When light is incident on the longest face, the Dove prism acts as a retroreflector or a right-angle prism. The light exits parallel to the input light (independent of the incidence angle) and is inverted by 180°. This geometry is shown to the left. In situations with limited space or where more convenient mounting options are needed, the dove prism can replace a retroreflector or right-angle prism.

Custom Coatings
Upon request, our prisms can be AR coated for the 290 - 370 nm (-UV), 350 - 700 nm (-A), 650 - 1050 nm (-B), or 1050 - 1620 nm (-C) spectral ranges. Please contact Technical Support for more information.

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* Unbeveled Length
** For the PS992M, these dimensions only apply to the prism, not its mount.

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Thorlabs Lab Fact: Dove Prisms Alter Polarization State and Image Orientation

We present laboratory measurements of the polarization and rotation state of a beam transmitted through Thorlabs’ PS992 and PS992M Dove Prisms. We also examine the influence of stress-induced birefringence on the final polarization state. In a polarization-dependent experiment, it’s important to understand how the polarization and orientation of the input beam is altered by a Dove prism. While it is known that Dove prisms introduce changes in the polarization of the transmitted light [1], we also find that localized stress-induced birefringence can significantly alter the polarization state. Finally we compare theoretical predictions of induced polarization change to the measured polarization change for both our unmounted and mounted versions of Dove prism.

For our experiment we used the HL6320G Laser Diode (635 nm) as the light source for our investigation. The laser beam was initially aligned using two crossed Glan-Taylor polarizers (GT10-A). The first polarizer set the polarization axis, and the rotation angle of the second crossed polarizer was recorded. The Dove prism was then placed in between the two polarizers, and the power of the beam was recorded after the second polarizer as a function of prism angle. Additionally, measurements were taken to determine the radii and orientation angle of the polarization ellipse. The polarization shift caused by the PS992 unmounted Dove prism and PS992M mounted Dove prism were measured. The unmounted prism was tested for polarization changes due to birefringence effects as well.

Click for full Lab Facts summary

The figure to the top right summarizes the measured results for image orientation as a function of prism angle. While it is well known that Dove prisms are used to invert images, it is interesting to note that the image rotation angle is twice that of the prism rotation angle. The figure to the bottom left summarizes the results of stress-induced birefringence on polarization state, while the figure to the bottom right summarizes the effects a Dove prism has on the polarization state and compares that to the theoretical values. Data is presented for both the unmounted and mounted Dove prisms with minimal stress. While Dove prisms do rotate the image, the polarization does not rotate with the image. Rather, the polarization is transformed from linear to various degrees of elliptical. For details on the experimental setup employed and the results summarized here, please click here.

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[1] Miles J. Padgett & J. Paul Lesso, "Dove prisms and polarized light," J. Mod. Opt. 46, 175-179 (1999).

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	Illustration	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.
		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°	180o 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.
		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.
			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 nfilm > 1.8 GGG used for nfilm < 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*	No	No		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°	90°	No		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	No	No		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	No	No		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	Illustration	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 90o 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.
		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.

* s-polarized light is not pure and contains some p-polarized reflections.

Beamsplitter Prisms

Prism	Material	Deviation	Invert	Reverse or Rotate	Illustration	Applications
Beamsplitter Cube and Mounted Beamsplitter Cube	N-BK7 - Grade A 400-700 nm 700-1100 nm 1100-1600 nm	50:50 splitting ratio, 0° and 90° s- and p- pol. within 10% of each other	No	No		Double prism configuration and dielectric coating provide 50:50 beamsplitting nearly independent of polarization. Non-polarizing beamsplitter over the specified wavelength range.
Polarizing Beamsplitter Cube and Mounted Polarizing Beamsplitter Cube	SF2 420-680 nm 620-1000 nm 900-1300 nm 1200-1600 nm	p-pol. - 0° s-pol. - 90°	No	No		Double prism configuration and dielectric coating transmit p-pol. light and reflect s-pol. light. For highest polarization use the transmitted beam.