Off-axis Mirror
The Off-axis Mirror is a mirror with an off-axis rectangular or elliptical aperture. The front surface of the object is an off-axis conic surface equivalent to the Off-Axis Conic Freeform sequential surface. The rear surface is conic with the same offset as the front surface.
The Off-axis offset parameter defines the distance Y0. This is the distance from the vertex of the parent shape, with axes y and z, to the vertex of the off-axis object, with axes y' and z'. The distance Y0is measured along the y axis.
The aperture shape is selected with the Shape parameter and is defined in the tangent plane to the front surface at the vertex of the off-axis part.
Freeform terms are added to the shape of the front surface in the same way as for the Off-Axis Conic Freeform surface. See Off-Axis Conic Freeform for more information on freeform terms and their calculation.
The Off-Axis Conic Freeform sequential surface is converted to the Off-axis Mirror object using the Convert to NSC Group tool if the following conditions are met:
- The Off-Axis Conic Freeform sequential surface must have the Material as MIRROR with a thickness specified.
- The aperture must be circular, elliptical, rectangular, or a user-defined aperture (UDA).
- Standard sequential surfaces will also be converted to an Off-axis Mirror object under the same conditions. Note that if the aperture is off-axis, this may cause a change in the substrate edges during the conversion. (Substrate edges will be parallel to the Z axis of the parent surface in sequential mode, but parallel to the modified Z axis (Z’) at the center of the off-axis aperture in nonsequential mode).
The following parameters are used to define the Off-axis Mirror object:
| Parameter # | Description | Face Name | Face # |
| 1 | X half width of the object. | NA | NA |
| 2 | Y half width of the object. | NA | NA |
| 3 | Center thickness of the object. | Side | 0 |
| 4-5 | Unused. | NA | NA |
| 6 | Shape of the aperture: 1 for elliptical, 2 for rectangular. | NA | NA |
| 7 | Radius of curvature of the front face. | Front | 1 |
| 8 | Conic constant of the front face. | Front | 1 |
| 9 | Radius of curvature of the back face. | Back | 2 |
| 10 | Off-axis offset, Y0. | NA | NA |
| 11 | Maximum polynomial term, must be a value of 0-238. | NA | NA |
| 12 | Normalization radius for the polynomial terms. | NA | NA |
| 13-249 | Polynomial terms. | NA | NA |
The reference coordinate is the center of the front surface. Face Numbers: Side faces Face 0, Front face Face 1, Back face Face 2
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