Hologram Surface
This object is an ideal optically fabricated hologram similar to the Hologram 1 and Hologram 2 sequential surfaces. The hologram is a surface, and may be circular or user defined in shape. The surface shape may be plane, sphere, or a conic and/or polynomial asphere. See also Hologram Lens.
The surface shape is defined by the following sag equation:
where c is the curvature of the surface, k is the conic constant, r is the radial coordinate, and the α terms are aspheric coefficients. The surface supports specification of both a minimum and a maximum radial aperture; so annular surfaces may be defined. Note that both even and odd terms are defined; up to 225coefficients may be used. This is the same shape as the Aspheric Surface object.
This object can also be used as a volume hologram by setting the Volume Hologram? parameter to 1. This does not affect the deviation of rays but it is used in the calculation of efficiency. Similarly, the Hologram Thickness parameter of the object does not effect the geometric shape of the object, only the efficiency. For a full description of non-sequential volume hologram objects, see Hologram Lens.
The following parameters are used to define the hologram surface (Par 18-25 are only available when Par 17 = 1):
| Parameter # | Description | Face Name | Face # |
| 1 | Radius of curvature. If this value is zero, then the curvature is assumed to be zero. | All Faces | 0 |
| 2 | Conic constant k. | All Faces | 0 |
| 3 | Maximum radial aperture in lens units. | All Faces | 0 |
| 4 | Minimum radial aperture in lens units. This value may be zero. | All Faces | 0 |
| 5-6 | Unused. | NA | NA |
| 7 | Holo Type: 1 if both sources converging/diverging, 2 if one source is converging and one is diverging. For more information, see Hologram 1 and Hologram 2. | All Faces | 0 |
| 8 | Diffraction Order: Multiple orders may be specified in Object Properties Diffraction tab, see Diffraction from NSC Objects. | All Faces | 0 |
| 9 | Construction Wavelength: The wavelength in micrometers used to fabricate the hologram. | All Faces | 0 |
| 10-15 | The X, Y, and Z coordinates in lens units of the construction points relative to the vertex of the front face of the hologram. | All Faces | 0 |
| 16 | The number aspheric coefficients to use in the aspheric expansion (up to 225 terms). Ray tracing will be faster if this term is no larger than the highest order non-zero coefficient. | All Faces | 0 |
| 17 | Volume Hologram?: 0 for false, 1 for true. | All Faces | 0 |
| 18 | Hologram Thickness: only used for efficiency calculations, not ray-tracing. | All Faces | 0 |
| 19 | Refractive index seen by construction beam 1 outside hologram, n1. | All Faces | 0 |
| 20 | Refractive index seen by construction beam 2 outside hologram, n2. | All Faces | 0 |
| 21 | Average refractive index of the hologram emulsion, n. | All Faces | 0 |
| 22 | Modulation of the refractive index, dn. | All Faces | 0 |
| 23 | Shrinkage: 0 for no shrinkage, else scale of thickness e.g. 0.98 is 2% shrinkage. | All Faces | 0 |
| 24 | Index Shift: change of average refractive index after developing. | All Faces | 0 |
| 25 | Consider Fresnel?: 0 for false, 1 for true. | All Faces | 0 |
| 26-249 | The α aspheric coefficients of the polynomial expansion. | All Faces | 0 |
Face Numbers: All faces Face 0. This object supports User Defined Apertures .
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