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Using the intensity fan

The intensity fan plots the sagittal and tangential intensity profile on a specified surface due to a point source placed at a field point. The calculation is purely geometrical and does not take into account energy losses in the lens due to reflections, scattering, or absorption. The intensity fan is most useful to analyze the intensity distribution on surfaces other than the image surface.

If the object is at infinity, the intensity in the plane of the system surface is assumed to be uniform and equal to 1 watt per square millimeter. If the object is at finite distance, the intensity is assumed to be emitted isotropically from a point source at a radiant intensity of 1 kilowatt per steradian. The graph is plotted in watts per square millimeter.

To create the intensity fan window:

  1. Select from the menu Analysis > Fans > Intensity

Exporting data from intensity fan

The underlying data may be exported using the Export toolbar icon, or by "Save data as..." on the contextual menu (obtained by control clicking on the image).

Options panel

Field
Using the Field popup menu, select the field for which you wish to calculate. Select All to calculate for all fields.
Wave
Using the Wave popup menu, select the wave for which you wish to calculate. Select All to calculate for all waves.
Number of rays
The ray fan curves are generated by tracing rays in each of the sagittal and tangential planes, forming crossed lines across the pupil. Each line is sampled using the specified number of rays, for each field and for each wave.
Color by
Specify how the curves are to be colored. Options are to use the color of the corresponding field or wave, or to use the same color for all curves.
Source type
Presently only isotropic point sources are modelled.
Detector type
Use this popup to indicate the angular response of the detector. Set to isotropic if the detector has no preferred direction. Set to cosine if the detector response is proportional to the cosine of the angle between the ray propagation direction and the surface normal.
Detector surface
Use this popup to select the surface on which the intensity is measured.
Length units
Use this popup to select the display units for the abscissa of the plot.
Local
If checked, the position coordinate is the reference frame of the surface. If not checked, the position coordinate is in global coordinates.
Scale only expands
If checked, the scale of the axes only expands due to the action of sliders, etc.
Axis tight on data
If checked, the limits of the axes are chosen so that the data exactly fills the graph. If not checked the limits of the axes are chosen to give "nice" values at the extremes of the axes.
Show legend
If checked, the names of the curves are presented in a list to the right of the plot.
Multiplot
If checked, each field point gets its own graph.
Transpose axes
If checked, abscissa and ordinate are interchanged on the graph.
Plot sum
If checked, sum of curves is also plotted. Unlike the individual curves, the sum has a monotonically increasing abscissa.
Plot sagittal curve
If checked, the sagittal curve is plotted.
Plot tangential curve
If checked, the tangential curve is plotted.
Use field weight
If checked, the power of each field is scaled by the field weight.