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Photopia Accuracy

Results you can trust.

An important issue to consider when using any optical design tool is accuracy. As a designer, you need to trust that your design tool is accurately predicting the distribution of light within your model. Time and money is lost when software tools fail to produce accurate results. We at LTI Optics understand this issue first-hand. We use Photopia on a daily basis to design products for our clients. Based on our experience, and the experience of other Photopia users, we've compiled a few case studies to illustrate how accurately Photopia predicts the distribution of light.

Photopia’s accuracy is well proven over its many years of use. Both LTI Optics and our customers have made comparisons between measured and predicted photometric distributions and as long as the physical luminaire matches the Photopia model in all respects, the results are very accurate. Note however, that Photopia makes no attempt to model changes in lamp lumen output as a result of thermal effects. Therefore designs that employ temperature sensitive lamps may show significant differences between the predicted and the measured total luminaire efficiency (LOR) since Photopia is only predicting the “optical efficiency” not the “thermal efficiency” of the design.

When analyzing a design in Photopia, it is important that the Photopia model match the physical model in all respects, including:

Optical Component Geometry – make sure reflector and lens shapes are accurately manufactured, which they often are not especially for sheet metal parts or cheap plastic lenses.

Optical Surface Properties – make sure the materials/finishes used in Photopia match those used in the physical parts.

Lamp Type and Modeled Orientation – in the case of MH lamps, extra care must be taken because the arc shape and position can shift as the lamp is aimed in different orientations.

Obviously, if the physical model does not match the Photopia model, the accuracy suffers.

These are 3 different LED lenses designed using Photopia. The images show the measured candela distribution as the blue line and the Photopia simulated distribution as the red line.

After the parts were designed and produced, their geometry was laser scanned and that laser scanned model was imported to Photopia so that the actual as-built geometry could be simulated. The as-built parts had enough deviation that this process was necessary to confirm the simulation was working correctly.

While there are some small deviations, they key parts of the beam are predicted very well, even including the small spikes of light near the top of the beam.

roadway lens accuracy

roadway lens accuracy image

narrow beam lens accuracy

accurace of paracube simulation

Description: 2' x 4' Paracube Troffer, White Painted Reflector, 3 T8 Lamps. Photopia model used 87% white paint, 2,000,000 rays with 10 reflections.

Efficiency: Photopia = 65.0% vs. Measured = 63.1%

All measured data supplied by Lighting Sciences, Canada.

paracube candela match 1

paracube candela match 2

paracube candela match 3

roadway reflector CAD model

Description: Roadway luminaire with a hydroformed reflector using a 150W SON-T HPS lamp.

BRDF data for the specific reflector finish was measured at LTI's lab and used in the analysis.

Measured Distribution

roadway reflector measured distribution

Photopia Distribution

roadway reflector Photopia distribution

We trust the accuracy of Photopia everyday doing work for our optical design clients and we know that you will as well.

For more information about pricing, purchases, or trials, please visit our pages for Photopia and Photopia for SOLIDWORKS.

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Copyright 2017 by LTI Optics, LLC, all rights reserved.

SOLIDWORKS® is a registered trademark of Dassault Systémes SOLIDWORKS Corporation.

LTI Optics provides Photopia, the industries leading optical design software and optical analysis software for designing and analyzing illumination optical systems. Photopia optical design software works alone or is an add-in to SOLIDWORKS, allowing full opto-mechanical integration.