
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:
- 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.