SWaP Reduction with the reTORT Ray Tracer from ExH
SWaP Reduction is the reduction of size, weight and power for a device. In many applications, we also seek greater power output. In optical lens design, we often replace the concept of power with greater clarity. Alternatively, we think in terms of reduced aberrations.
At E x H, Inc., we routinely perform use this concept in our Customer design programs. We’ve done this for DARPA, and for the Navy, Air Force and Army. Those have been both optical and RF.
We also completed a revolutionary prelim design for innovative satellite mobile ground station startup Isotropic Systems. That used these same principles of SWaP reduction. In that case, the device was designed for the K, Ka and Ku bands.
Size and Weight Reduction of the Double Gauss
Here we’ll show how to lower the size and weight of a Double Gauss lens. This lens is very similar to a standard photographic 35mm lens. We’ll do the SWaP by replacing two doublets with gradient index lenses. Gradient index lenses are also referred to as GRIN lenses.
Our main principle is based on the dispersive GRIN lens. A dispersive lens is one that varies in behaviour at different wavelengths. These lenses perform color correction very well. Therefore, a GRIN singlet can act similar to an achromatic doublet, or triplet for that matter.
The E x H reTORT ray tracer is one of the few lens design packages that can offer robust support for realistic dispersive GRIN models. This is especially easy with reTORT with our proprietary material engine providing binary mixtures of two realistic dispersive materials.
In the following image, you’ll see that there are two doublets. These are the 2nd and 3rd lenses. Actually, there are six lenses in this system as each doublet is two lenses bonded together.
Optimizing the new Optic Lens Design
In the image below, we’ve removed the two doublet and replaced them with GRINs. These gradient index lenses consist of a binary mixture of Polycarbonate and PMMA plastics.
We’ve found this combination of plastics to work well in correcting color aberrations. For the most technical of you, here’s the basic info on these plastics:
Results of the New Lens Design
We allowed the index of refraction to vary both radially and axially. After optimization, we converged to a high performing design.
The index of refraction profiles of each of the two gradient index lenses is shown below. These are in the same order as the above figures. You can see that the reTORT Ray Tracer from E x H keeps the index of refraction within realistic bounds.
The spot size ranged between 10 microns for the on-axis field angle and 30 microns for the off-axis 20 degree angle. This off-axis angle is often referred to as the half field of view or HFOV.
The design also leaves enough room for a mechanical iris in the center of the lens system. This is very desirable for DLSR camera lens designs.
Benefits of the new Optical Lens Design
Our original objective, a reduction in size and weight, is the primary objective. By definition, the GRIN lens has more dispersive power per unit weight. Therefore, a lighter lens can be used for identical or even better color correction.
Here you can see the final size and weight of the original and the redesigned lens. You can also see that the volume and weight reduction achieved is 40 and 50% respectively.
The above image shows that the benefits of using GRIN lenses is very clear. And the reTORT Ray Tracer makes this design objective easy to implement.
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About E x H, Inc.
Our mission is to provide you with advanced simulation tools. These tools allow you to design optical and RF systems that are smaller, lighter, faster and have greater clarity than ever before.
We license some of our solvers from Penn State University. PSU’s world reknowned Computational Electromagnetics and Antennas Research Laboratory. have developed these solvers.
Many of our scientists and engineers have been educated at CEARL.
We have also participated on multiple programs funded by DARPA as well as other sectors of the Department of Defense.
On the business side, we have been backed by Gran Sasso Ventures, the same venture capitalists that funded collaboration software firm Compoze Software, now a part of Oracle [ORCL:NYSE], and multitouch technology inventor FingerWorks, the driver of touch screen technology and now a part of Apple [AAPL:NASDAQ].
E x H is at the forefront of transformation optics.
