A Dove prism is a specialized reflective optical prism used primarily for image rotation. Its distinctive truncated, wedge-like shape allows it to rotate an image through a precise angle simply by rotating the prism itself around its longitudinal axis. This unique property, combined with its compact form, makes it invaluable in applications where space-saving and dynamic image control are critical.

The Dove prism is essentially a truncated right-angle prism. It operates based on total internal reflection (TIR). Light enters one of the long, flat faces, travels through the prism, reflects once off the sloped base, and exits through the opposite long face. This single reflection causes the image to invert.

• Image Rotation: When the prism is physically rotated by an angle θ around its longitudinal axis, the image it transmits rotates by 2θ. This relationship allows for precise optical control.

• Requirement for Collimated Light: It is crucial to note that the Dove prism only functions correctly with collimated light (light rays that are parallel). Using it with converging or diverging beams introduces significant optical aberrations.

• Materials: Typically manufactured from high-quality optical glass (e.g., N-BK7) or fused silica, chosen for their homogeneity and transmission properties across the desired wavelength range (visible, UV, or IR).

• Precision Requirements: The two long faces must be polished to a high degree of flatness (e.g., λ/10) to prevent wavefront distortion. The critical 45° angles must be held to tight tolerances to ensure accurate image rotation without deviation.

• Coatings: While it relies on TIR, anti-reflection coatings are almost always applied to the entrance and exit faces to minimize Fresnel reflections and maximize throughput.

• Compact Beam Folding: Its elongated shape allows it to fold an optical path into a very small, linear space, making it ideal for compact laser systems.

• Image Derotation: Its primary application is to correct or compensate for image rotation in rotating systems. This is essential in:

  • Interferometry: Stabilizing fringe patterns.

  • Astronomy: Compensating for field rotation in telescopes.

  • Laser Scanning Systems: Controlling beam orientation.

• Component in Complex Systems: Often used as a building block in image erection systems, K-mirror assemblies (a more complex derotator), and optical encoders.

• Chromatic Aberration: As with most prisms, it can disperse light slightly, though this is minimal due to the single reflection.

• Polarization Sensitivity: TIR can affect the state of polarized light, which must be considered in sensitive applications.