We have a mobile lens design file designed by zemax.
The type of Fields in this design file is currently "angle", and if I attempt to replace it with "real image height", the following warning message appears:
"Cannot find rays to yield requested image height"
How can I change the field type to real image height while resolving these warning messages?
Best answer by David.Nguyen
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+2
Hi Kivahan,
Since I was involved with your previous question. I can try to help you here as well.
Normally, you’d convert the Field Type instead of just changing it. But we established you don’t have this option in 16.5. If you simply change the Field Type, the field value doesn’t change automatically (this is what the Convert To feature does). Imagine you have a 20 degree field with an angle definition. When you change the field type to Real Image Height. OpticStudio simply interprets the number 20 as now being lens units (most likely millimeters), and this might be too large for your optical system (as indicated by the warning).
All you need to do is reduce the field values in the Field Data Editor. The amount by which you should reduce it depends on the system. Before changing the field type, you could use the real chief ray landing coordinate (also shown in my answer to your previous question) as the new field value, and then change the field type to real image height.
Let me know if that makes sense.
Take care,
David
Thank you for letting me know that the 16.5 version does not automatically change the Fields Type. I decided to buy the latest version of Optic Studio.
I don't have this year's investment budget of my research organization, so I think I can purchase it by the end of this year.
Anyway, when I changed it to 'Real Image Height', I recorded the IMA value provided by Spot Diagram in advance and entered it into the Y value of Real Image Height, so I could see a successful Layout 2D.
May I ask you one more question here?
I want to enter the Y value of the last field larger than the IMA value, but there is a "Cannot File Rays to field requested image height" error.
I have already set the Semi-Diameter value of Surface of all lenses to Fixed.
Is there anything else I should consider?
I remember this being possible on Double Gausss 28.zmx.
+2
Hi Kivahan,
No problem, just one clarification. I’m still not sure whether the field conversion is available in 16.5. You need to check with someone from Zemax for that to be sure.
I’m glad you were able to change the field type successfully. If you fix the semi-diameter of your surfaces, it might hide the underlying problem. In general, I’d recommend to fix the semi-diameter of your surfaces at the final stage of the design only. In the case of the Double Gauss example, with a Real Image Height of 30, this is what I get:
If I push the field to 40, this is what happens:
As you can see, the field is so far off that the lens surfaces have crossed each other, leading to a negative thickness. And then, the further you increase the field, the more this becomes a problem. I’m not exactly sure what might happen in your case, but the image location simply cannot be calculated anymore, leading to this error message. Try floating the semi-diameter of your surfaces (remove the fixed semi-diameter) and increase the field little by litte while checking the layout for this kind of behaviour. If this happens, you may need to consider re-optimizing the system to account for the new off-axis field.
I hope this makes sense.
Take care,
David
Thank you for your answer. By fixing the Semi-Diameter on the double Gaussian 28 lens, setting the Fields Type to Real Image Height, and changing the Y value of the magic field to 50, I could extract the RI graph that I expected. The Relative Illuminatin graph draws a sharp downward curve at about half the height of the Film diagonal (50).
I wanted to proceed with the above work in the mobile lens that we designed internally.
To do that, I had to fix the Semi-Diameter, and then I wanted to extend the last Fields to half the size of the Film Diagnostic, but… In this process, unlike Double Gauss 28, opticalstudio issued a "Cannot find races to field requested image height" error.
I wonder why I couldn't see that message on Double Gauss 28. And the resulting RI graph was the same as I expected. I don't know the difference between the two lenses.
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