Parabolic mirrors have the ability to focus collimated light without introducing spherical aberration. An Off-Axis Parabolic (OAP) mirror is simply a side section of a parent parabolic mirror. Collimated light that is incident to an OAP mirror is focused to a point. However, unlike a centered parabolic mirror, an OAP mirror has an advantage in that it allows more interactive space around the focal point without disrupting the beam.
Depending on which section of a parabolic shape an OAP mirror is replicating, the angle between the focal point and the central ray axis can be large or small. Below figure represents this phenomenon by modeling a 15° and 45° off axis mirror respectively. It is important to keep the incident beam parallel to the optical axis, any angular displacement will produce comatic aberration.
Honour Optics offers off-axis parabolic mirrors with Protected Gold, Bare Gold, Protected Aluminum, UV Enhanced Aluminum, and Protected Silver coatings.
Honour Optics also offers high-performance glass substrate off-axis parabolic mirrors with superior surface accuracy for increased focusing ability. Typical applications include use in Czerny-Turner and Littrow spectrometer configurations and in general collimator and beam expander setups. These mirrors work extremely well in the UV to the visible light spectrum.