Hello everyone,

EDIT: I was wrong, NPRO’s last parameter is actually the wave number as pointed out by @MichaelH below. Therefore, there’s no need to use a user-defined operand

EDIT: new version available in my last reply below!

I have made a user operand equivalent to INDX for non-sequential systems.

In non-sequential systems, INDX doesn’t work, and one workaround is to use a ZPL operand with the numeric function NPRO using the code 200 (index of refraction of an object). For some time, I used the following code in a ZPLM (I hope the code is self-explanatory but let me know otherwise):

object = PVHX()

OPTRETURN 0, NPRO(1, object, 200, 0)

However, if one has multiple wavelengths defined, it always seem to default to the first one (wave number: 1), and there’s no direct possibility to specify a wavelength in NPRO, whereas this is possible with INDX.

A work around is to use the Multi-Configuration Editor with the operand WAVE and a single wavelength defined in the System Explorer. That way, one can use a CONF operand before ZPLM to specify which configuration needs to be considered. However, this is not always desirable, which is why I made a C# user-operand that calculates the non-sequential refractive index with the wave number as a paramter. The complete code is available on my GitHub, but here is the important part:

// Add your custom code here...

// Object number from which to evaluate material index
int object_number = (int)Hx;

// Wave number at which to evaluate material index
int wave_number = (int)Hy;

// Actual wavelength
double wavelength = TheSystem.SystemData.Wavelengths.GetWavelength(wave_number).Wavelength;

// Wavelength squared
double wavel_squared = wavelength * wavelength;

// Catalog number (following look-up "switch" below, e.g. 1 = Schott)
int catalog_number = (int)Px;

// Catalog look-up
string catalog = "";
switch(catalog_number)
{
    case 1:
        catalog = "Schott";
        break;
    // Add other catalogs here
    // ...
}

// Get Material name
string material = TheSystem.NCE.GetObjectAt(object_number).Material;

// Open >> Librairies..Materials Catalog
IMaterialsCatalog material_cat = TheSystem.Tools.OpenMaterialsCatalog();

// Select catalog and material
material_cat.SelectedCatalog = catalog;
material_cat.SelectedMaterial = material;

// Run Materials Catalog
material_cat.RunAndWaitForCompletion();

// Initialize dummy refractive index value
double refractive_index = -1.0;

// Look-up index formula
switch (material_cat.MaterialFormula)
{
    // Sellmeier 1
    case MaterialFormulas.Sellmeier1:
        // Initialize fit coefficients
        double K1, K2, K3, L1, L2, L3;

        // Get fit coefficients
        K1 = material_cat.GetFitCoefficient(0);
        K2 = material_cat.GetFitCoefficient(2);
        K3 = material_cat.GetFitCoefficient(4);
        L1 = material_cat.GetFitCoefficient(1);
        L2 = material_cat.GetFitCoefficient(3);
        L3 = material_cat.GetFitCoefficient(5);

        // Refractive index calculation
        refractive_index = K1 / (wavel_squared - L1);
        refractive_index += K2 / (wavel_squared - L2);
        refractive_index += K3 / (wavel_squared - L3);
        refractive_index *= wavel_squared;
        refractive_index += 1.0;
        refractive_index = Math.Sqrt(refractive_index);

        break;
    // Add other formulas here
    // ...
}

// Close Materials Catalog
material_cat.Close();

operandResults[0] = refractive_index;

As you can see, I’ve only implemented the Schott catalog, which only uses the Sellmeier 1 formula, but we can add the other catalogs if people are interested.

The operand parameters are Hx: Object number, Hy: Wave number, Px: Catalog number (Schott = 1). And here is an example with N-BK7:

And the comparison with INDX in the same settings (Surface 2 is N-BK7 and F, d, C wavelength preset):

I’m also attaching the compiled operand UDOC06.exe file to my post.

Take care,

PS: there’s no error trapping. Avoid specifying an object number that hasn’t a material defined and use a wave number > 0

David