hi all
is there a way i can do an optimization to find the best apodization for my stop in order to get the best MTF?
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Apodization optimization
Best answer by Jeff.Wilde
Hi Tav,
It’s hard to know why your optimization didn’t update the apodization value without at least seeing the merit function. I put together a very simple model using a paraxial lens with and without a central obscuration (implemented via a user obscuration which was just a circular disk UDA file). Optimization at a single MTF frequency seems to work fine in both cases (using just one MTFA operand, *not* the default contrast optimization approach). The results are attached.
The case without the central obscuration behaves as expected (see, e.g., Goodman, Intro. to Fourier Optics, 4th Ed., Sec. 7.4.5, “Apodization and Its Effects on Frequency Response”). When I included a central obscuration and optimized at a frequency that appears to be most impacted, Gaussian pupil apodization seems to offer less benefit, probably not worth the extra effort, cost, and loss of light. However, some other form of apodization may prove more useful; it’s difficult to say without further investigation. It also depends on what part of the MTF curve you are most interested in improving.
Regards,
Jeff
+2Hi Tav,
I have no clue how it is going to work, but there’s a Multi-Configuration operand APDF, which controls the apodization factor:
This Multi-Configuration operand can be set as a variable and it can be constrained in the Merit Function using the Multi-Configuration (Zoom) Data operands: CONF, MCOL, MCOG, MCOV, ZTHI (described in the Help File, and in this knowledgebase article).
Let us know if it works for you (I’m curious about your results), and take care,
David
+3Hi Tav,
I think the approach David describes should work well for Gaussian apodization of the pupil. However, if you happen to need alternative forms of apodization, another approach would be to use a User Defined apodization surface, which can be placed adjacent to the stop surface (for pupil apodization), or more generally anywhere else in the system that might be of interest:
Several different UDS apodization functions are provided -- see the US_FILT* options.
The various input parameters to these filtering surfaces can then be set as variables for optimization.
Regards,
Jeff
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+2Hi
Out of curiosity, what is the intended goal of optimizing the apodization? Is it to then engineer the corresponding light source to achieve maximum performance?
Thanks for your help and take care,
David
+3I’m with
The optimization will almost certainly produce an apodization that illuminates the center of the pupil with most of the energy, and has least at the edges. That will minimize the aberrations of the system, by driving the ‘effective entrance pupil diameter’ to zero.
Hi
i have an central obscuration wish a spider like aperture, i want to get a better MTF by controlling the Apodization over the aperture, does it make sense? ill be happy to hear your thoughts.
Tav
I have tried what you suggested, but it didnt work out, the value of the apodization factor did not change, any idea what i did worng?
Tav
+3Hi Tav,
the issue is really about what control you have over the illumination entering the system. The native apodizations OS supports are Uniform (for when the object is a long distance away from the pupil) cos-cubed (for when the object is close to the pupil) and Gaussian (for lasers).
Optimizing the apodization only makes sense to me if you can have some control over the source illumination.
_mark
Hi Mark
so I think I wasn't clear, sorry, we have costing abilitity in my company, our goal is to create apodization by coating the aperture. not controlling the light entering the system
+3Hi Tav,
It’s hard to know why your optimization didn’t update the apodization value without at least seeing the merit function. I put together a very simple model using a paraxial lens with and without a central obscuration (implemented via a user obscuration which was just a circular disk UDA file). Optimization at a single MTF frequency seems to work fine in both cases (using just one MTFA operand, *not* the default contrast optimization approach). The results are attached.
The case without the central obscuration behaves as expected (see, e.g., Goodman, Intro. to Fourier Optics, 4th Ed., Sec. 7.4.5, “Apodization and Its Effects on Frequency Response”). When I included a central obscuration and optimized at a frequency that appears to be most impacted, Gaussian pupil apodization seems to offer less benefit, probably not worth the extra effort, cost, and loss of light. However, some other form of apodization may prove more useful; it’s difficult to say without further investigation. It also depends on what part of the MTF curve you are most interested in improving.
Regards,
Jeff
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