Dove prism
The Dove prism, rarely Harting - Dove prism called, is an optical prism, which is counted to the inverting reflection prisms. Because the light is refracted at both the entrance and at the exit surface, it can be used for image reversal only monochromatic light. Its use is also limited to parallel beam, as would occur due to the refraction at the oblique side faces astigmatism.
The prism was named after Heinrich Wilhelm Dove.
- 3.1 double Dove prism
- 3.2 Dove prism with roof prism surfaces
Design and operation
A Dove prism, a prism with the base of a trapezium with the side faces inclined at 45 °; Often it is also described as an isosceles, right-angle prism, wherein the cut is in the optically inactive area. The length of the prism is usually four to five times (in the case of glass as a prism material ) so as the diameter of the light beam to be transmitted.
Arrives along the longitudinal axis of the prism extending, collimated beam of light on one of the inclined surfaces of incidence it is first broken into the prism, and led to the longest side of the prism. Here, the light beam undergoes a total reflection and is refracted again at the inclined exit surface. Input and exit beam are aligned with one another, but learns an image through the unique prism reflection in a reflection about a line transverse to the beam direction.
Properties and application
Rotation about the longitudinal axis
A Dove prism is rotated about its longitudinal axis, a transferred image by twice the angle rotated. Upon rotation of the prism about 180 °, for example, the image rotates by 360 °, and the rotational speed of the image about the optical axis is twice as large as the rotational speed of the prism. This property can be used to rotate a beam by an angle randomly chosen. This results in the use of Dove prisms as " beam rotator ", which find application in areas such as interferometry, astronomy and pattern recognition application. A special area of application is multi-channel fiber optic rotary joints for coupling of optical waveguides from stationary to rotating parts, such as in industrial robots. While the Dove prism is rotated by a specific gear at half the speed as the moving part of the fiber, and thus realizes the permanent image of the collimated light beams from the input to the output fibers.
Polarization
Lesso and Padgett ( 1999) and Moreno et al. (2003, 2004 ) have established that changes the polarization state of a light beam when passing through a Dove prism. These properties of Dove prisms are of particular interest because it can affect the signal measurement of scientific instruments.
Variants
Double Dove prism
If two Dove prisms joined at their longest side (after the silvering by a metal coating ), there arises the so-called double - dove prism. It behaves essentially like a simple Dove prism, however, the beam center located at the center of the entire prism. Thereby, the light beam is split in the prism into two sub-beams of different running and the prism can be halved ( as compared to the simple Dove prism ) at twice the level in the length. By splitting into two beams, the double Dove prism must be made very carefully to prevent example, a drifting apart of the two image halves.
Dove prism with roof prism surfaces
In this prism, the large reflective surface is replaced by two roof prism surfaces. Is substantially equal to an Amici prism, wherein the light beam but the input and the output surface passes vertically. In the reflection on the roof prism surfaces, the image in the center is cleaved, and the fields are each twice reflected separately before they recombine. The double reflection causes an image is not reversed. In the Dove prism with roof prism surfaces undergoes an image rotation of 180 ° around the optical axis.