Hi Gianluca,

Assuming you want to optimize the last thickness value before the image plane such that the RMS spot size is minimized. You could use the Optimize..Quick Focus feature with the Spot Size Radial criterion (this is the RMS spot radius).

You can decide to use the Centroid (as shown in the screenshot) or the chief ray landing position to compute the RMS spot radius. For this particular feature, you don’t even need to set the last thickness as a variable.

Alternatively, under Optimize..Optimization Wizard. You can generate a default Merit Function with an Image Quality: Spot and Type: RMS. That would optimize your variable to minimize the RMS spot size in your image. As shown in my screenshot below.

I also strongly suggest browsing the getting started articles here (OpticStudio is the third column).

Hope this helps.

Take care,

David

Dear David,

Many thanks for your reply. The single spot size is optimized in this way, but if there are more than one fields, it try to optimize the spot size across the entire field.  so for example, the RMS at 0° is getting worst, like in the attached images. There is a way to give priority to the field point I want to optimize that is not delete the fields point before to run the optimization ??

Before optimization with quick focus

 
After Optimization with quick focus
 

Dear Gianluca,

If you open the Field Data Editor, by double-clicking on Setup..System Exporer..Fields. You get your list of fields with a column named Weight. The default should be a value of 1.00 for all your field. You can increase the weight of the field you are interested in to 10.00 for example.

When you then use the Quick Focus, OpticStudio will take into consideration the higher weight on your field of interested.

Example with all weights at 1.00

Same example with weight of 10.00 for the Field 1

Let me know if it works for you.

David

Many thanks David. It was very helpful.