Optical design software for architectural lighting.

Tunable White & Color Mixing Optics

Photopia is the perfect optical design software for your tunable white, circadian lighting or RGBW mixing optical design projects. Photopia includes a large range of accurate white and RGB LED source models based on their physical geometry and measured spectral properties. Photopia also produces all standard photometric reports & plots for indoor, roadway and floodlight applications. Furthermore, Photopia’s true color images, color reports & special colorimetric plots help you both qualitatively & quantitatively evaluate the color uniformity in your beam. This is helpful when using single color white LEDs due to their variable spectrums over emission angle and emission area. It’s even more essential in tunable white applications with 2 or more different CCT LEDs used in the same optic.

This example tunable white reflector optic uses an array of 14 LEDs, half at 2700K and half at 5000K. The LED array is arranged to mix the colors as best as possible, but there are still large gaps between the LEDs of each color. Putting a simple diffuser in front of this LED array would mix the colors well, but that also eliminates your ability to control the beam distribution. Many designs require specific intensity distributions such as a wide batwing, asymmetric wall washer or narrower spots & floods. This example achieves a 40° medium flood beam angle. Producing a controlled beam angle with well mixed colors requires adding beam spreading features to the optic that blend just the right amount, but no more. The types of curved facets shown on this reflector are an effective mechanism for controlled beam spread. These types of features can be quickly generated for reflector and lens optics with the Grasshopper tool provided in one of our tutorials.

The first true color image shows the appearance of the spot produced when the color mixing is not quite enough. If you look closely around the beam perimeter, you will see alternating regions that are more blue and more yellow. As the design gets closer to producing well mixed results, it becomes more difficult to see the subtle changes in the true color image, which in part depends on the quality of your display.

The “Delta u'v' from Average” plot makes it much easier to identify color difference trends in the beam. In this plot, black represents the average beam color and bright green is the largest difference from the average. In the uniform u'v' color space, a color difference of 0.001 is 1 MacAdam Ellipse, which is a just perceptible color difference. Keeping max color differences to 0.004 within the main beam angle is a common goal for single color designs. This is much more difficult to achieve in a tunable white design, which therefore puts a greater emphasis on reducing the chance of perceiving distinct blue/yellow patterns in the beam. The “Delta u'v' from Average” plot for this beam clearly shows the blue/yellow color differences around the perimeter from the 10 alternating color LEDs.

With additional color mixing features, the color uniformity has been significantly improved. The changes around the beam perimeter are no longer seen and there is now only a smoothly changing color from the beam center outward, a much more acceptable trend.

Successfully designing this type of optic so that it works the first time you build it is not possible without accurate color LED models, useful optical design tools & relevant output, all of which is provided by Photopia.

Quantitative Metrics

In addition to visual color quality renderings, Photopia contains complete color data on any illuminance surface and for the entire distribution. This allows you to verify the final mixed CCT, determine compliance with Delta u'v' metrics, and quantify color in specific parts of the beam.

✔ Total luminous and radiant flux

✔ Total CCT, u'v', uv, and xy

✔ Delta u'v' over beam, field and distribution

✔ Color coordinates and uniformity for each illuminace plane

✔ IESX file with color for each angle in distribution

Luminaire Spectral Effects Interacting with Architecture

Photopia can be used to model lighting effects not possible in standard lighting design software such as AGI32, Dialux & Relux. Luminaires in lighting design software are approximated as uniformly emitting rectangular boxes and room surfaces are generally assumed to be diffuse. Any glossy reflections shown in lighting design software renderings are only approximated effects using a single pass ray trace at the end of the image generation process. Such effects don't influence computed lux values. Luminaire photometry doesn't generally include spectral properties and when it's assigned, it's generally constant over the entire distribution. By contrast, Photopia can model any light source geometry & spectral properties along with any type of material scattering & spectral properties.

To the left is a luminaire modeled with randomized holes in the shade with red, green & blue LEDs inside. Since the LEDs are all in unique locations, they project offset patterns through the holes onto the surrounding room surfaces. Their colors are all mixed in the beam center however, which includes their direct light plus light reflected off the white reflector.

Photopia's direct integration into CAD and Parametric Optical Design Tools allow you to quickly create and optimize optical shapes, like the TIR collimator shown to the left. This collimator has an array of warm and cool white CSP LEDs that can be mixed to create a wide range of CCTs.

✔ Revolved reflectors for downlights

✔ Extruded reflectors for linear sources

✔ Extruded prismatic lenses for linear LED lighting

✔ Lofted profiles for smooth roadway lenses

✔ Revolved smooth or prismatic lenses

✔ Equation driven smooth lenses