Calendar
"Effective Use of LightTools" Webinar
May 22, 2013
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LightTools Training
June 3-7, 2013
Amsterdam,
The Netherlands
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SPIE Optics + Photonics
August 25-29, 2013
Booth 1116
San Diego, CA
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Introduction to Illumination Design Using LightTools
October 7-10, 2013
Pasadena, California
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COM Macro Programming in LightTools
October 11, 2013
Pasadena, California
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For a complete list of LightTools events worldwide: visit our website
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In this issue:
Tip: Balancing Distribution and Power with LightTools Optimization
In many lighting applications there are illumination patterns that are desirable, sometimes even mandated. For example, backlight designers typically strive to achieve uniform spatial luminance over the backlight surface. With automotive exterior lighting there are required intensity specifications that must be met before a vehicle can legally operate on public roads. Achieving the desired light distribution must be balanced with maintaining the appropriate level of power or flux throughput from the light sources to the target.
When designing illumination systems in LightTools, you can optimize for both the beam pattern as well as the power across the distribution. You can define a single merit function that considers both the pattern and the power at the same time, or you can define separate merit functions that consider the pattern and the power independently.
Use a single merit function
When you add a mesh merit function to control the pattern, you can set the variance to be normalized (i.e., you define the relative distribution in each bin), fixed to a specified value, scaled based on total power, or scaled based on a desired peak value. When you choose to explicitly define the target value using Do not change target values, Scale targets based on total power, or Scale targets based on desired peak value, then a single merit function is used to balance the pattern and power. When these options are used, the values in the target mesh are not normalized values, but correspond to actual values found in the data mesh.
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Use separate merit functions to control the pattern and the power independently
If you choose Normalize mesh values by target flux, then the mesh merit function controls only the pattern. Target values are normalized and control only the relative values in the data mesh. To control the power as well, you would need to add an additional merit function item, like the total incident power or flux on the receiver.
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Why might you want to use a single merit function vs. two merit functions?
When using a single merit function, you only have to maintain a single component, which is convenient when you know the mesh, total power, or peak value targets you need to reach on a receiver. When the target values aren’t clear, however, you need to take care to set the target scaling to reasonable levels. A potential drawback in some cases is that the individual contributions of the pattern and power to the total merit function are buried in a single merit function value, so it isn’t clear when one component is driving the optimization.
When you use two merit functions, you can manually adjust the contribution of the pattern merit function value and the power merit function value to the total merit function value independently. If the optimization isn’t converging to your liking using a single merit function, separate merit functions give you control over the weighting of the two merit functions, which could help you get to an optimal solution for your particular system.
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For your design, there is nothing wrong with trying both methods and seeing which one leads to the best result!
LightTools Support for Windows XP To Be Discontinued in 2014
LightTools 8.1, currently scheduled for release in late 2013, is the last version that will support Windows XP. Beginning in 2014, LightTools releases will not support Windows XP. If you have any questions, please contact ora_support@synopsys.com.
Watch Our New LightTools Video on YouTube
We are pleased to announce that our video featuring LightTools street lighting design and analysis is now on the Synopsys YouTube channel. Check it out and share it with your colleagues who might be interested in learning more about LightTools. To view the video, click on the image below.
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