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Using the spot diagram

The spot diagram shows where the rays intercept the image plane in graphical format.

To create a spot diagram window:

  1. Select from the menu Analysis > Spots > Spot diagram
  2. Press the Options button to get the options panel.

The options panel for the spot diagram:

spot-options

Options

Source selection (Field, Beam, or Emitter)
With the left-hand popup menu set to Field the right-hand popup lets you select the field for which you wish to calculate. Select All to calculate for all fields. You can also set the left-hand popup to Beam or Emitter to generate spot diagrams for those sources.
Wave
Using the Wave popup menu, select the wave for which you wish to calculate. Select All to calculate for all waves.
Pattern
Using the Pattern popup menu, select the pupil pattern to use. If the Random pattern is selected, a randomize (Roll) button will appear and the toolbar Randomize icon will be enabled.
Number of rays
When plotting Field sources the pupil is sampled using the specified number of rays, for each field and for each wave.
Paraxial trace all rays
Use paraxial propagation instead of full geometric optics propagation.
Suppress vignetted rays
Not yet supported. Contact us if you need it.
Surface
Using the Surface popup menu, select the surface to which the rays should be traced. This lets you look at beam footprints.
Abscissa
Using the Abscissa popup menu, select the quantity for the horizontal axis of the graph (assuming the transpose axes flag is not set). The possible values are described below. Units may be selected using the popup menu to the right.
Ordinate
Using the Ordinate popup menu, select the quantity for the vertical axis of the graph (assuming the transpose axes flag is not set). The possible values are described below. Units may be selected using the popup menu to the right.
Local coordinates (default: checked)
This checkbox determines if the rays coordinates are in the local coordinates of the surface, or in global coordinates.
Subtract centroid
Uses the centroid of the rays (on a per field and per wave basis) instead of the chief ray.
Grid/subtract/fan
The Grid checkbox causes reference coordinates to be generated on a per-field basis. The reference coordinates will be the product of the specified factor and the the field coordinate as specified on the sources window and the specified factor. For example, with the factor set to 0.02, a field point at (0,2) degrees will have its rays offset by (0,0.04) millimeters, assuming the spot diagram is working in millimeters. The Airy disk and reference ellipsoids will also be drawn displaced, for each field. Checking the subtract checkbox will cause the reference coordinates to be subtracted from the ray coordinates. Checking the fan checkbox will add back in the reference coordinate multiplied by the specified scale factor, so that the spots from different fields can be separated on the graph. Setting the fan scale factor to 0.1, for example, displays the spots at 1/10 their original separation.
Draw Airy disk
If checked, the Airy disk is drawn. The Airy disk can only be drawn if abscissa and ordinate are x, y, x/f, or y/f.
Draw reference ellipsoid
Draws an ellipsoid of the specified size at the origin (or at the field grid points, if Offset, fac. is enabled).
Isotropic
If checked, the scale of the axes is chosen to make equal distances in x direction and y direction be the same on the plot.
Transpose axes
Transposes x and y axes. See here.
Scale only expands
If checked, the scale of the axes only expands due to the action of sliders, etc. Useful for scanning through focus using the sliders tool.
Multiplot
Enables the multiplot plot style.

 

Plottable values

xx coordinate
yy coordinate
uxx tangent
uyy tangent
pxx momentum (direction cosine times refractive index)
pyy momentum (direction cosine times refractive index)
x/fx coordinate divided by focal length
y/fy coordinate divided by focal length
thetaxx angle of travel (angle on x-z plane)
thetayy angle of travel (angle on y-z plane)
thetaangle of travel (with respect to z direction)
txangle of travel times px/sqrt(px*px+py*py)
tyangle of travel times py/sqrt(px*px+py*py)