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 uncoated with 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, or 30 mm square cross sections (see the Specs tab for more information on dimensions). Our 15 mm version is available uncoated or with one of two AR coatings deposited on the two angled faces. We also offer Dove prisms mounted in SM-threaded housings. For information on our full selection of prisms, please see the Prism Guide tab.
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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.
Shown at the top of the page is a Dove prism mounted in a retroreflection geometry, as described under Retroreflection below. In this photo, the Dove prism is secured to a KM200B Kinematic Platform Mount by a PM4 Clamping Arm. For applications sensitive to the polarization of the transmitted light, care should be taken when clamping these prisms. Stress-induced birefringence further alters the polarization of light incident on the prism. See the Lab Facts tab for more information.
Dove Prism Video
This animation shows how the image rotates as the prism is rotated.
Image Rotation
Light is usually propagated along the longitudinal axis of a Dove prism. In this geometry, shown in the diagrams on the bottom left and middle, 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 to the right). For example, a 20° rotation of the prism results in a 40° rotated image. The AR-coated Dove prisms are designed specifically for the image rotation and inversion application.
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 below and to the right. 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 245 - 400 nm (-UV), 350 - 700 nm (-A), 650 - nm (-B), or - (-C) spectral ranges. Please contact Technical Sales for more information.
Light propagated along the longitudinal axis is inverted by 180°.
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Rotation of the prism over some angle results in a rotation of the image over twice that angle.
Light incident on the longest face of the prism is retroreflected and inverted by 180°.
A Dove Prism is an optical prism that can be used to rotate, retroflect, or invert an image. It is shaped like a triangular right-angle prism with the top cut off, or truncated.
These prisms work best with collimated light. The length of these prisms (approximately four times the height) means they will introduce substantial astigmatism when they are used with converging light.
If light enters through a sloped face and is propagated along the longitudinal axis of the prism it reflects once from the bottom face and emerges from the other short side, resulting in an inverted image. There is one interesting and unique feature of dove prisms: If you rotate the prism around the longitudinal axis the image will rotate at twice the speed. Rotate the prism 30 degrees, and your image will rotate by 60.
This special property of dove prisms means they can rotate a beam of light by an arbitrary angle. While images passing through the prism are flipped, they are not laterally transposed or deviated because only one reflection takes place.
Even if the propagation axis and the prisms longitudinal axis are not perfectly parallel, the high incidence angle means that the light reflecting from the bottom face undergoes total internal reflection. For situations where the hypotenuse cant be kept clean enough for TIR, we can provide metal or hydroelectric coatings.
Factory Standard
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