Diffraction Grating (non-sequential geometry objects)
The diffraction grating is a Standard Lens with a diffraction grating on one face. For a rectangular diffraction grating, see "Lenslet Array 1" .
Parameters 1-9 are the same as for the "Standard Lens" object:
| Parameter # | Description | Face Name | Face # |
| 1 | The radius of curvature of the front face. Use zero for infinity (flat). | Front | 1 |
| 2 | The conic constant of the front face. | Front | 1 |
| 3 | The clear semi-diameter or semi-diameter to the clear aperture of the front face. Use a negative value to yield the hyperhemispheric sag point. | Front | 1 |
| 4 | The radial aperture to the edge of the front side of the lens. | Front | 1 |
| 5 | The center-to-center thickness of the lens. | Side | 0 |
| 6 | The radius of curvature of the rear face. Use zero for infinity (flat). | Back | 2 |
| 7 | The conic constant of the rear face. | Back | 2 |
| 8 | The clear semi-diameter or semi-diameter to the clear aperture of the rear face. Use a negative value to yield the hyperhemispheric sag point. | Back | 2 |
| 9 | The radial aperture to the edge of the rear side of the lens. | Back | 2 |
The Diffraction Grating is defined by the following parameters:
| Parameter # | Description | Face Name | Face # |
| 10 | The grating line frequency in lines/micrometer on the front face. See parameter 12 below. | Front | 1 |
| 11 | The diffraction order for the front face. | Front | 1 |
| 12 | The grating formula. If zero, the grating is a constant spacing linear grating with a grating frequency defined by parameter 10. If the formula is "1", the grating frequency in lines/micrometer is defined by | Front | 1 |
| 13-16 | Coefficients on the grating frequency formula. These are only available when Formula = 1. | Front | 1 |
If the grating formula is "1", the grating frequency in lines/micrometer is defined by
where t0 is defined by parameter 10 and the other coefficients are defined by parameters 13-16.
The grating is assumed to consist of lines parallel to the local x axis. The grating frequency is the lines per micrometer along the y direction; projected down on to the surface.
This object does not diffract rays correctly if the front diffractive surface is made hyperhemispheric. For important information on diffractive objects, see " Diffraction from NSC objects " .
Face Numbers: Front face Face 1, back face Face 2, all other faces Face 0.
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