![]() As a consequence, the two approaches will not yield the exact same values. First, the ray patterns in the Spot Diagram are different from those available in the Merit Function Wizard. Now with regard to the rms values reported in the Spot Diagram Text output, there are a few key differences compared to the Merit Function approach. The choice between these two options is available in the Merit Function Wizard: In our case, for the x spot size, the values are simply the x-coordinates of the ray intercepts with the image plane (i.e., the transverse ray aberration values taken along the x-direction), measured either with respect to: (1) the central chief ray, in which case the x values are synonymous with the TRAX terms, or (2) the spot centroid, in which case the x intercept values are given by the TRCX terms. Then, add the same set of extra operands to compute the Y rms spot The rms value of any discrete set of numbers is, Next, for the Y rms spot size, go back to the MF wizard and repeat using X-Weight = 0 and Y-Weight = 1, but be sure to insert this default set of TRAY operands *after* the existing X terms. However, if we want both X and Y spot sizes then the extra operands above can be added. Note: If all we wanted was the X rms spot size, we don’t even need the extra operands, the default merit function will itself evaluate to the correct value. Here’s a simple example using a ParaxialXY lens.įirst, use the MF wizard to generate the spot size with X-Weight = 1 and Y-Weight = 0, then find the rms X spot size by computing the RSS of the TRAX operands and dividing by the square root of the number of TRAX terms: The X & Y rms spot sizes can be fairly easily computed in the merit function by using the wizard to generate the X and Y spot operands (TRAX and TRAY aberration operands) using the weight parameters as described above by David, in combination with a few extra operands to form the spot sizes. The semidiameter of the lens should be fixed so that the lens diameter does not change when the beam is changed.Ī standard spot diagram can display the spot, which will be a line. To shift or tilt the beam on the lens, a Coordinate Break can be placed before the lens and used to shift and/or tilt everything after the break, which is equivalent to tilting the beam. The lens will of course focus in one plane only and when focused on the image plane produce a spot in the form of a line.įor optimization, the Optimization Wizard can be used to construct a merit function targeting an RMS spot size of zero, with either X Weight or Y Weight set to a weight of 1 depending on the orientation of the lens, and with the other at a weight of 0. The beam width can be defined by setting the aperture to Entrance Pupil Diameter.Ī cylindrical lens can be made using a Biconic or Toroidal surface followed by a standard surface. To collimate the beam, the object is at infinity. Since you want to model a collimated beam, you likely want a single field in angle space with an angle of 0 degrees.
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