Total power and total flux

  • 23 September 2022
  • 5 replies


I’m calculating the energy inside a surface with LEDS with different detectors: volume detector, sphere as detector, volume pipe as detector… but I can’t get the same values across them… I don’t know why if I hace the same system…

From objects as a detector I get total power, but from volume detector total flux (all of them in mW); is this the same?

When I take a value from the matrix in volume detector, what is this? flux, power¿?

This is my file, I calculate the three detectors individually

Thanks in advance,



Best answer by David.Nguyen 26 September 2022, 12:23

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Userlevel 7
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Hi Carmen,


I don’t have OpticStudio at hand, but I noticed none of your detectors have ASORB in their Material column. This means that if the same ray intersects your object multiple time, it’s energy will be added to the detector the same number of times. I don’t know if that’s your issue, but you can try with a Source Ray going through a Sphere setup as a Detector. If you make the Source Ray 1 Watt, and the Sphere hasn’t got any material, the total flux recorded is going to be 2 Watts (assuming the Source Ray intersects the Sphere in two points). If you then change the material of the Sphere to ABSORB, as soon as the ray interesct the Sphere, it contributes to the total flux and gets totally absorb to prevent it to interact with anything else. Thus, the total flux will be 1 Watt, as expected.

Hope that helps. Take care,


Hi David!

Thank you so much for your answer.

Yes, my issue is to know the energy inside the system in different points, for this reason I didn’t want that any of the materials in detectos absorb the energy. I’m novel in non-sequential mode, but I though if the detectors absorb enery modified the values, Is this rigth¿?

I tried with different detectors, I don’t know which one is better for my system. I though that values (if I take in account the surface area in the different detectors (in the picture the table down/rigth in red), should be the same or similar, but it isn’t. In volume detector is half than sphere as a detector… I don’t know why this factor... if it’s because the difference between one is total power and another total flux… anyway, in volume pipe as a detector is same units than sphere and value is different…I don’t know due the shape in this case...

I don’t know if I explain well my doubt, and you could help me. I’will appreciate a lot.

Take care, Carmen

Hi David!

When the sphere as a detector not has material, (as default coat). Is the detector with transmission 100%?

 With this condition the detector counts the ray twice? at the entrance and exit?

Could be this reason which makes that the sphere as a detector has twice value the volume detector?


Thanks, take care


Userlevel 7
Badge +2

Hi Carmen,


Yes, you are correct. When a Detector doesn’t have a material, it will not affect the rays in any ways. The transmission is going to be 100 percent and the ray will count twice. This is what I tried to explain before but since I didn’t have access to my OpticStudio over the weekend, I couldn’t send screenshots.

Let me show you with the example I had in mind.

In this case, the Sphere is a Detector and it doesn’t have a Material. Despite the fact that the Source Ray is 1 Watt, the Sphere Detects 2 Watts. This is because it counts the ray any time it intersect the Sphere, in this case twice.

If you change the Material to ABSORB, this is what happens:

As you can see, because the ray is absorbed, it only intersects the Sphere once, and the total power is 1 Watt, as expected.

I think you are also correct in that the Pipe and Sphere have different volumes. Therefore, they might record different total powers because of that.

The Detector Volume works a little bit differently in the sense that it uses voxels (3D) instead of pixels. Therefore, it depends a little bit on how you set it up. If you use a single voxel, that is not a problem, it will just record the total power, even without the ABSORB material. However, if you have 2 voxels axially, it will record twice the total power. Here is an example with 3 voxels along Z:

As you can see, the total flux is 3 Watts. This problem can be corrected by setting the Material to ABSORB, once again.

Does that make sense? Take care,



Hi David! 

Yes, that make sense and solve my doub!

Thank you so much! It was really helpful 


Take care, Carmen