Posted by Matt Novak, Product Manager, CODE V on February 11, 2021
Today’s optical designers are often tasked with finding ways to correct more aberrations and use fewer surfaces, and do so in more compact geometries that must fit within anything from smaller medical instruments to more wearable Augmented Reality (AR) systems. Setting up compact geometry, with multiple reflecting or refracting surfaces, can be challenging when there are numerous folded surfaces or complex optical path constraints. To help support this type of design work, CODE V offers unique and powerful freeform design and optimization tools.
If you are designing freeform optics, check out the top five tools that will support your design optimization and analysis in CODE V.
1. Q2D Freeform Asphere
Q2D freeform aspheres in CODE V are a great tool for optimization, offering orthogonal polynomials that converge smoothly in many cases. For some designs, you may find that Q-type polynomial aspheres are able to converge more rapidly to a good solution due to their orthogonality, since they are less likely to suffer competition among terms for the balancing of aberrations in the design space. In addition, CODE V offers unique geometric positioning of the used portion of the surface relative to the base conic vertex.
Q2D Freeform Asphere all-reflective, asymmetric design
2. Methods for Modeling Aspheric Departure from a Base Conic Surface
For a subset of freeform aspheric surfaces, CODE V now offers two methods for modeling aspheric departure from a base conic surface. The first, unique method, allows for an off-axis angle parameter – omega — to denote how far off axis the conic surface will be used. The local coordinates for the surface will be located by a shift of the surface through angle omega. CODE V also offers X and Y offset parameters to shift the origin for polynomial departure.
Freeform polynomial departure applied on base conic in CODE V
The new extended Fringe Zernike polynomial surface in CODE V offers the same polynomials designers have been used to for their optical system modeling, but with an extension to higher order radial terms up to R30.
3. Coefficient Table
Starting in CODE V 11.3, designers have access to a unique coefficient table that allows the symmetry condition of the system and the corresponding compliance (or non-compliance) with that symmetry condition to be seen quickly, in a friendly visual format. Having this visibility to the coefficients that meet (or do not) the desired symmetry condition of your system enables the most efficient use of the design optimization variables, and helps to keep awareness and use of only effective variables for the system improvement.
2D coefficient grid with no symmetry condition assumed for the optical system
2D coefficient grid highlighting X-Z symmetry condition for the optical system
4. Visualization of Surface Departure, Sag and Slope Information
CODE V makes it easy to visualize the surface you have designed to get a feel for how steep the aspheric slopes are for manufacturing purposes. By using built in functionality to see the surface departure and sag and slope information, you can see potential problem areas and work on refining the surface shape via further controls in your design optimization.
Q2D freeform asphere surface sag plot
5. User-Defined Surface (UDS) Based on Chebyshev Polynomials
For optical systems requiring optimization over rectilinear pupils, CODE V offers a new user-defined surface (UDS) based on Chebyshev polynomials, which is useful for systems with square or rectangular apertures. This surface representation includes terms up to the 14th order for additional flexibility when optimizing modern, folded, compact designs.
Chebyshev coefficients table
Two mirror reflector with Chebyshev surfaces
Using these new and powerful tools in CODE V to design freeform optical systems saves time. When you combine these tools with CODE V’s optimization strength and speed, you will see increased efficiency in bringing designs from preliminary stages to final acceptance.
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