Grid Sag Lens
The Grid Sag Lens is a solid volume object with a Standard surface front face, and a Grid Sag surface rear face. The Standard surface shape is described in "Standard" . The Grid Sag surface shape is described in " Grid Sag " .
Grid Sag Lens objects use the following parameters:
| Parameter # | Description | Face Name | Face # |
| 1 | The x half width in lens units. See the discussion below. | NA | NA |
| 2 | The y half width in lens units. See the discussion below. | NA | NA |
| 3 | The front surface radius of curvature in lens units. | Front | 1 |
| 4 | The front surface conic in lens units. | Front | 1 |
| 5 | The axial lens thickness in lens units. | Side | 0 |
| 6 | Interpolate. Use 0 for bicubic, and 1 for linear. See "Bicubic spline vs. linear interpolation" . | NA | NA |
| 7 | The back surface radius of curvature in lens units. | Back | 2 |
| 8 | The back surface conic constant. | Back | 2 |
| 9-16 | The back surface αi aspheric coefficients. | Back | 2 |
| 17-18 | The X- and Y-decenter values in lens units. This is the decenter of the grid data relative to the aspheric substrate. The decenter values are added to any decenter values defined in the GRD file, described below. | NA | NA |
If the x and y half widths are zero, the lens shape is rectangular and the size is defined by the data in the GRD file. If the x half width is zero, and the absolute value of the y-half width is not zero but is less than the size of the data in the GRD file, then the part is square (if the y half width is greater than zero) or circular (if the y half width is less than zero). If both the x half width and the y half width are not zero, and the absolute values of both half widths are less than the size of the data in the GRD file, then the part is rectangular (if both half widths are positive) or elliptical (if either half width is negative).
The actual point by point sag data is defined by placing the data in a properly formatted file ending in the extension GRD. The file format is defined in "Importing grid data" . The grid data file must be placed in the folder <objects>\Grid Files (see " Folders " ). The file name, without the path, is then placed in the comment column of the NSC Editor.
The reference coordinate is the center of the front face. Face Numbers: Side faces Face 0, front face Face 1, back face Face 2.
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