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N.A of focussing optical system

  • 30 December 2022
  • 2 replies
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Hi all,

I’m trying to find the numerical aperature of my focussing optical system. I use two method to find the N.A 

(1) I use the priscription data to check the value of image space N.A   (N.A- 0.13)

(2) I use RAID merit function to check the N.A of my system  (N.A- 0.11)

Both these method shows different result. Which N.A value should I consider as correct one?

Any help will be much appreciated.

Thanks

 

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Best answer by Chandan.Maurya 30 December 2022, 18:27

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Hi @sanjeev kumar.singh,

I think NA shown in the prescription data has to be considered. There is a mismatch in NA for two different approch is because of abberation present in your system. If the aberrations will be controlled to a great extent NA aperture calculated from RAID angle value will approach the NA show in prescription data (provided focal length for both the aberrated and unaberrated system has to be exactly same).

 


​​Fig: Aberrated System

 

 

 

 

                                                            Fig: Unaberrated System compared to previous one.

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Most imaging systems have aberrations, so therefore I suggest you use the Working F/# (WFNO) to find the most relevant numerical aperture: NA = 1/(2*WFNO).  The value for WFNO is also available in the prescription report.  In your case, this yields NA = 0.1105.  As @Chandan.Maurya notes, the “Image Space NA” applies to the paraxial case (which, by definition, means aberrations are ignored). 

From the help documentation:

 

Regards,

Jeff

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