Design of an Off-Axis Parabola Mirror

The off-axis parabola mirror (OAP Mirror) is widely used in advanced optical systems that meet increasingly stringent performance requirements. The design and specifications of OAP Mirrors are key elements that significantly affect manufacturing costs and the overall performance of these systems. To standardize the design and specification process of OAP Mirrors, Avantier plans to release a series of technical resources to enhance understanding and streamline the process.

Geometry of OAP Mirror

The diagram below shows the basic geometry of the off-axis parabola Mirror.

Design of OAP 1

The parent curve is defined by the conic equation:


  • RoC: parent radius of curvature at the parent vertex
  • k: conic constant, =-1 for parabolic mirror
  • r: distance to the parent axis
  • Off-Axis Angle: angle between parent axis and segment 
  • Z: sag in parent z axis

For OAP Mirror, k=-1, the equation is reduced to:

Desgin of OAP 2

Typically, the beam’s aperture, which can be either circular or square, is oriented along the Z axis. The actual size of the aperture on the optics’ surface may appear elliptical or rectangular, depending on the off-axis angle. 

For optics with large off-axis angles or apertures, opting for a non-wedge design becomes a more cost-effective solution. In this design, a tilt angle can be specified relative to the parent Z axis. 

Off-axis parabolic mirrors (OAP Mirrors) can be manufactured from various materials, including metals (using single-point diamond turning), glass, and specialized ceramics like SiC. The choice of material significantly influences the overall cost and precision. Avantier’s application engineers are on hand to assist you in selecting the most suitable material and surface quality for your specific application. 

Avantier offers a range of coating options tailored to your chosen material, including metallic coatings such as protected aluminum or dielectric coatings designed to withstand high laser damage thresholds. 

Designing optics with built-in alignment features to streamline final integration is an essential strategy. Avantier’s application engineers will guide you in defining manufacturing and metrology-friendly alignment features.

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