CODE V Enewsletter

March 2015

Quick Tip: Optimizing for a Blurred Spot Size: A User-Defined Error Function Example

In many imaging applications, it is desirable to target the image spot size to be as small as possible. However, in the case when an image sensor is used at the image plane, it is the pixel size that determines the minimum effective image spot size. Or for systems operating near diffraction limits, the airy pattern defines the smallest possible spot size. Any geometrical size less than these image patch dimensions won’t improve image quality in the actual system.

Allowable Spot Size

The default error function for CODE V’s Automatic Design will optimize to achieve a minimum RMS Spot Size, which works well for most scenarios. For systems where geometrical spot size is approaching a geometrical limit like pixel size or diffraction limit, allowing some blur or aberration could provide additional freedom for the optimizer to satisfy other constraints. You can define this type of error function during your optimization by using a customized user-defined error function.

An example of such a user-defined error function can be found on the Customer Support Portal. The user-defined error function utilizes a user-defined macro function named @SPOR. The @SPOR macro function will trace a chief ray and a second ray at requested pupil coordinates. You’ll also pass it a radius value that defines the acceptable blur around the chief ray. If the second ray is inside the definedblur circle, the macro function will return zero. If the second ray is outside the blur circle, it’ll return the distance from the circle.

Image Plane

The user-defined error function uses a grid of rays over the pupil and adds the result of @SPOR for each ray. Thus, when all rays are inside the acceptable patch size, the error-function value is zero.

This user-defined error function, function definition and an example are now available on the Customer Support Portal.

OSA Freeform Optics Conference

OSA is sponsoring a Freeform Optics conference on June 7-11, 2015, which is co-chaired by one of our engineers, Dr. Kevin Rolland-Thompson, Group Director, Research and Development, Optics. Invited speakers from both industry and academia are scheduled to speak on the latest developments on optical design, optical system simulation, surface representation, and more. A presentation will be made by Dr. Bill Cassarly of Synopsys entitled "Assessing freeform illumination surface tolerances."

The conference will be held at the Renaissance Arlington Capital View Hotel in Arlington, Virginia. For more details, please visit the OSA website. Online registration for this conference is now open.

Retirement of John Isenberg

John Isenberg

John Isenberg, a longtime CODE V Technical Support Engineer, has announced his retirement, effective at the beginning of April. John joined Optical Research Associates, now a part of Synopsys, in 1978 as a member of the Optical Engineering staff. For the past 23 years, John has worked in Technical Support, where he has shared his CODE V expertise and insights with customers through technical support correspondence and training sessions. We wish John the very best in his retirement!