Dove Prism
Definition and meaning of Dove Prism in chemistry.
A Dove prism is a truncated right-angle triangular prism that inverts an image by total internal reflection off its long (hypotenuse) face, producing a top-to-bottom flip of the light passing straight through it.
In more detail
Light enters one angled end face, reflects once off the long bottom face (by total internal reflection, so no reflective coating is needed), and exits the opposite angled end face traveling in the same direction it entered. Rotating the prism about its long axis rotates the transmitted image at twice the prism's rotation rate, which makes it useful for continuously adjustable image or beam rotation. Because the optical path length through the glass differs across the beam's width, Dove prisms only work correctly with collimated (parallel-ray) light; converging or diverging beams pick up aberrations and astigmatism.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Mechanism | Single total internal reflection (uncoated) |
| Light requirement | Collimated (parallel) beam only |
| Image behavior | Rotates image at 2x the prism's mechanical rotation |
In a laboratory rotational-shear interferometer used to test the collimation and wavefront quality of a laser beam, a Dove prism is placed in the collimated beam path and rotated; the resulting fringe pattern rotates at twice the prism's angle, revealing wavefront asymmetries.
Frequently asked questions
Why must light entering a Dove prism be collimated?
The glass path length varies across the prism's cross-section, so non-parallel (converging or diverging) rays traverse different thicknesses of glass and pick up aberrations and astigmatism; collimated light avoids this because all rays travel the same effective path.
How does a Dove prism differ from a plane mirror for flipping an image?
Both invert the image top-to-bottom, but rotating a Dove prism about its optical axis rotates the transmitted image continuously at twice the mechanical rotation angle, a behavior a single flat mirror cannot reproduce.