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Accurate lightpipe model

Question asked by Graeme Edwards on Jun 6, 2011
Latest reply on Jul 5, 2016 by Jake Sharpstone

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Hi all

I was wondering how other people analyze the effectiveness of lightpipe designs?

I have designed a one piece instrument front out of clear polycarbonate, which has lightpipes moulded into it to transfer SMT LED light to the front to illuminate symbols on a front adhered decal. We made a prototype machined out of polycarbonate which showed problems of light transfer into adjacent symbols, so I've changed the design based on some 2d "raytrace" sketches using equations to calculate refraction and internal reflection, and want to virttually test the result before I commit to new prototypes.

I tried to test it by placing point lights into LED models, and doing a final render, The problem is that Photo view doesn't seem to be very accurate about internal reflections and I get a general glow rahter than any sort of accurate representation.

Is photo view the right tool?

if not what would others suggest?

if it is , what am I doing wrong?

here's a view of the result.

There is one lit LED for each group of indicators, ie of the left three, only one should be lit, and of the right four, only one etc As you can see there is just a general glow illuminating every thing around.

Any suggestions?

Thanks

Graeme

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Harold Brunt Jun 7, 2011 8:09 AM

Hello Graeme,

A good place to start is to do a quick search on the forum for "lightpipe" or "LED simulation". You might notice the "More Like This" tab next to your post which has a few of the threads I would reference (Re: Application for Lightpipe design and Re: Realistic LED simulation").

I do not use PV360 although it looks like a useful tool. Rendering software and simulation softwares share a lot of the same basic methods for calculating light output but there are significant differences which is what you are seeing in your model / prototype. Rendering software is intended to show how you would like the product to look; simulation software will show what you are going to get like it or not! There are several softwares available and you can find the marketing blurbs in the SW partners listing. I use OptisWorks Add-In for SW for the type of work you are doing. There is also ASAP Breault which is the only other software besides Optis that works within the SW environment. Lightools requires that the model be exported via a bridge between the lighting simulation software and the SW environments.

For a project like yours I would construct a physically correct model of the system right down to the last detail of the source including material properties, etc. Some physical elements can be suppressed during the development until you get close to the results you want in order to speed up the process but ultimately the more detail without introducing error the better. The simulation results can be used to optimize the system and once complete can be used to update the rendering.

Harold

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Graeme Edwards @ Harold Brunt on Jun 9, 2011 2:50 AM

Thanks Harold

That makes interesting reading.

The Optis software looks like it would be useful, but I don't know if the company would spring for it. Times are tough.

It's a shame companies like this don't display prices on their website. Do you have any idea how much they charge for the plugin?

I have modelled the part accuratly, including applying appropriate textures on the different surfaces and correcting the refraction index to be what I've found for PC material. I also modelled the SMT LED as accuratly as I could. Mind you I don't know how accuratly PV360 calculates refraction and reflection or how to accuratly model the light output from the LED which will obviously change things. The PV light editor just shows brightness in w/srm^2, a point light radius in mm, and a shadow quality dimensionless number.

Graeme

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irmeli rehbein @ Graeme Edwards on Jun 9, 2011 5:17 AM

if you don't need the analysis side of how many lumes are emitted at the end of your lightpipe etc you can use http://www.maxwellrender.com

it's the most accurate render engine out there ( as long as you stick to the correct refractive index and other material properties) and the rendered images give you a very good idea how good your light pipe works.

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Harold Brunt @ irmeli rehbein on Jun 9, 2011 7:20 AM

Not to be dismissive but rendering software is rendering software no matter how powerful. A very nice image though (no sarcasm intended - it's hard to tell on a forum sometimes!). The benefit of using simulation software is that there is limited opportunity to manipulate the outcome. There's always the risk of GIGO as with any analysis program but that's where training and experience come to play. All of the simulation add-ins are relatively expensive. We have been adding packages as we can afford them or as we absolutely need them over the years since they can be purchased in modules. I don't think it would be fair, accurate or appropriate for me to post prices for specific packages since they can range from $5K to $25K but getting quotes is free and you can get a free 30 day trial. You would also be best served by running the latest SW release since the add-ins are typically based on the newest software.

Another option is to outsource your light study. You can make the corrections for yourself to save a little money then have someone else run the simulations. If you need to make more than a couple of changes to your prototype, if the project schedule is being compromised or if you are taking a risk on hard tooling it wouldn't take long to justify the cost of the light study. If you release new products frequently then wouldn't take much more effort to justify purchasing the software for yourself. We are able to perform basic FEA but when the application is critical we have experts to contact. We don't need to do that level of FEA very often so we haven't invested in the software. At some point we might need to but not yet. Same considerations can be made for light studies.

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Jake Sharpstone Jul 11, 2016 8:01 AM

Hi Graeme,

You can now directly trace light rays in Solidworks using TracePro Software (RayViz), you can assess the ray path in lightpipes directly in Solidworks, or you attribute the surface and material properties in Solidworks, such as PMMA or polcarb then do the analysis of the light pipe in TracePro.

You can also optimise light pipe design automatically using the TracePro software.

There are many webinars and tutorials here:

http://www.lambdares.com/applications/light-pipe-design

Yoo can also contact Lambda direct for advice on light pipe design and optimisation.

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Jake Sharpstone Jul 11, 2016 8:01 AM

The Photorealistic rendering capability is also an essential way to analysis accurately what the human eye sees of a light pipe, you can see an example here:

http://www.lambdares.com/images/modules/documents/Lambda%20-%20Photorealistic%20Rendering%20in%20TracePro%20Data%20Sheet…

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6 Replies

Harold Brunt Jun 7, 2011 8:09 AM
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Correct Answer
Hello Graeme,

A good place to start is to do a quick search on the forum for "lightpipe" or "LED simulation". You might notice the "More Like This" tab next to your post which has a few of the threads I would reference (Re: Application for Lightpipe design and Re: Realistic LED simulation").

I do not use PV360 although it looks like a useful tool. Rendering software and simulation softwares share a lot of the same basic methods for calculating light output but there are significant differences which is what you are seeing in your model / prototype. Rendering software is intended to show how you would like the product to look; simulation software will show what you are going to get like it or not! There are several softwares available and you can find the marketing blurbs in the SW partners listing. I use OptisWorks Add-In for SW for the type of work you are doing. There is also ASAP Breault which is the only other software besides Optis that works within the SW environment. Lightools requires that the model be exported via a bridge between the lighting simulation software and the SW environments.

For a project like yours I would construct a physically correct model of the system right down to the last detail of the source including material properties, etc. Some physical elements can be suppressed during the development until you get close to the results you want in order to speed up the process but ultimately the more detail without introducing error the better. The simulation results can be used to optimize the system and once complete can be used to update the rendering.

Harold
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- Graeme Edwards @ Harold Brunt on Jun 9, 2011 2:50 AM
  Mark Correct
  Correct Answer
  Thanks Harold
  That makes interesting reading.
  The Optis software looks like it would be useful, but I don't know if the company would spring for it. Times are tough.
  It's a shame companies like this don't display prices on their website. Do you have any idea how much they charge for the plugin?
  
  I have modelled the part accuratly, including applying appropriate textures on the different surfaces and correcting the refraction index to be what I've found for PC material. I also modelled the SMT LED as accuratly as I could. Mind you I don't know how accuratly PV360 calculates refraction and reflection or how to accuratly model the light output from the LED which will obviously change things. The PV light editor just shows brightness in w/srm^2, a point light radius in mm, and a shadow quality dimensionless number.
  Graeme
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  - irmeli rehbein @ Graeme Edwards on Jun 9, 2011 5:17 AM
    Mark Correct
    Correct Answer
    if you don't need the analysis side of how many lumes are emitted at the end of your lightpipe etc you can use http://www.maxwellrender.com
    
    it's the most accurate render engine out there ( as long as you stick to the correct refractive index and other material properties) and the rendered images give you a very good idea how good your light pipe works.
    Like • Show 0 Likes0
    Actions
    - Harold Brunt @ irmeli rehbein on Jun 9, 2011 7:20 AM
      Mark Correct
      Correct Answer
      Not to be dismissive but rendering software is rendering software no matter how powerful. A very nice image though (no sarcasm intended - it's hard to tell on a forum sometimes!). The benefit of using simulation software is that there is limited opportunity to manipulate the outcome. There's always the risk of GIGO as with any analysis program but that's where training and experience come to play. All of the simulation add-ins are relatively expensive. We have been adding packages as we can afford them or as we absolutely need them over the years since they can be purchased in modules. I don't think it would be fair, accurate or appropriate for me to post prices for specific packages since they can range from $5K to $25K but getting quotes is free and you can get a free 30 day trial. You would also be best served by running the latest SW release since the add-ins are typically based on the newest software.
      
      Another option is to outsource your light study. You can make the corrections for yourself to save a little money then have someone else run the simulations. If you need to make more than a couple of changes to your prototype, if the project schedule is being compromised or if you are taking a risk on hard tooling it wouldn't take long to justify the cost of the light study. If you release new products frequently then wouldn't take much more effort to justify purchasing the software for yourself. We are able to perform basic FEA but when the application is critical we have experts to contact. We don't need to do that level of FEA very often so we haven't invested in the software. At some point we might need to but not yet. Same considerations can be made for light studies.
      Like • Show 2 Likes2
      Actions
Jake Sharpstone Jul 11, 2016 8:01 AM
Mark Correct
Correct Answer
Hi Graeme,
You can now directly trace light rays in Solidworks using TracePro Software (RayViz), you can assess the ray path in lightpipes directly in Solidworks, or you attribute the surface and material properties in Solidworks, such as PMMA or polcarb then do the analysis of the light pipe in TracePro.

You can also optimise light pipe design automatically using the TracePro software.

There are many webinars and tutorials here:

http://www.lambdares.com/applications/light-pipe-design

Yoo can also contact Lambda direct for advice on light pipe design and optimisation.
Like • Show 0 Likes0
Actions
Jake Sharpstone Jul 11, 2016 8:01 AM
Mark Correct
Correct Answer
The Photorealistic rendering capability is also an essential way to analysis accurately what the human eye sees of a light pipe, you can see an example here:

http://www.lambdares.com/images/modules/documents/Lambda%20-%20Photorealistic%20Rendering%20in%20TracePro%20Data%20Sheet…
Like • Show 0 Likes0
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