Tolerancing in Zemax - PowerPoint

Document Sample
Tolerancing in Zemax - PowerPoint Powered By Docstoc
					Tolerancing in Zemax

   OPTI 521 Tutorial
    By Stacie Hvisc
   December 5, 2006
                   Outline
• Motivation
• Zemax tolerancing capabilities
  – Sensitivity Analysis
  – Inverse Sensitivity Analysis
  – Monte Carlo
• Zemax Demo
• Conclusion
                         Motivation
• Once you design a lens, you will want to know how it will
  perform once it is built.
• Tolerancing a lens is a very important skill to have.
   – We can do this by perturbing each element individually and
     reoptimizing the system, which is very slow, but accurate.
       • On homework 4, we perturbed each element at a time to find the
         sensitivities
   – We can find all the sensitivities at once by using Zemax’s
     tolerancing function.
       • This method is very fast, but there is a lot of room for mistakes.
           – On the homework, some people hit the sensitivity analysis button and
             got numbers that were incorrect – up to two orders of magnitude off!
  Zemax tolerancing capabilities
• You can set tolerances in the tolerance data editor for a
  wide variety of parameters
   – There is a default tolerance generator which can automatically
     enter tolerances for: Radius of curvature, fringes, thickness,
     position, x and y tilt, x and y decenter, irregularity, wedge, glass
     index, Abbe number, and more.
   – Other things you can tolerance include: aspheric constants,
     decenters/tilts, solve and parameter tolerances, etc
• You can define what compensators you wish to use,
  such as focus, tilt, or position of any optical element,
  surface, or element group.
   – Remember on the homework, we used the final focus position
• You can select the tolerance criteria
   – For example, on the homework, we used RMS wavefront
 Zemax tolerancing capabilities
• ZEMAX conducts an analysis of the
  tolerances using any or all of these three
  tools:
  – Sensitivity Analysis
  – Inverse Sensitivity Analysis
  – Monte Carlo Analysis
         Sensitivity Analysis
• The sensitivity analysis considers each
  defined tolerance independently.
  Parameters are adjusted to the limits of
  the tolerance range, and then the optimum
  value of each compensator is determined.
  A table is generated listing the contribution
  of each tolerance to the performance loss.
   Inverse Sensitivity Analysis
• The inverse sensitivity analysis iteratively
  computes the tolerance limits on each
  parameter when the maximum or
  incremental degradation in performance is
  defined. Limits may be overall or specific
  to each field or configuration.
                 Monte Carlo
• The Monte Carlo analysis is extremely powerful and
  useful because all tolerances are considered at once.
  Random systems are generated using the defined
  tolerances. Every parameter is randomly perturbed using
  appropriate statistical models, all compensators are
  adjusted, and then entire system is evaluated with all
  defects considered. User defined statistics based upon
  actual fabrication data is supported. ZEMAX can quickly
  simulate the fabrication of a huge number of lenses and
  reports statistics on simulated manufacturing yields.
            Zemax Demo
• How to do Homework 4 in Zemax:

• 1st step: open the HW4.zmx file
  downloaded from the course website
             Zemax demo
 In the Zemax window, go to “Editors” drop
  down menu and choose “Tolerance data”
  and the Tolerance Data Editor will open.
            Zemax demo
 On the Tolerance Data Editor window, go
  to the “Tools” drop down menu and select
  “Default Tolerances…”
            Zemax demo
• …and the following Default Tolerances
  window will open.
             Zemax demo
 Adjust the perturbations to match what I
  used on the homework and click “OK”.
            Zemax demo
• …and the following table appears
                     Zemax demo
• This table is the Tolerance Data Editor
  mentioned earlier.
  – Here you adjust each of the tolerances.
  – Columns:
     • 1) Operand number
     • 2) 4 letter mnemonic for the tolerance
          – see next slide for a list
     •   3) Surface number for tolerance
     •   4 and 5) Skip for now
     •   6) Nominal value (helps me identify surfaces)
     •   7 and 8) Minimum and Maximum perturbations
     •   9) Comments
Tolerance mnemonics in Zemax
• Tolerance
  operands tell
  ZEMAX
  which
  parameters
  in the system
  to change.
• ZEMAX uses
  4 letter
  mnemonics
  for the basic
  tolerances:
               Zemax demo
• After using the generate default tolerances
  window, you need to check to make sure all the
  numbers are correct.
  – For example, the lens spacing between lens 1 and
    lens 2, I had a perturbation of 0.2mm on the
    homework, but all thicknesses were set to be 0.1mm
    perturbations.
  – Zemax adds an additional compensator for
    thicknesses (in column 4). If you don’t want this,
    delete it – possible room for mistakes here!
            Zemax demo
 Next go to the “Tools” drop down window
  and choose “Tolerancing” and then
  “Tolerancing…”
                      Zemax demo
• Then the following
  Tolerancing window opens
  up.
   – Choose your mode:
     (Sensitivity, Inverse
     Sensitivity, Inverse
     Increment, Skip
     Sensitivity). We want
     Sensitivity right now, which
     is the default already
     chosen.
   – Choose the Criteria: (RMS
     Spot Radius, RMS
     Wavefront, Merit Function,
     Boresight Error, MTF and
     more). We need to select
     RMS Wavefront.
                 Zemax demo
– Tolerancing window
  cont.
   • Choose the
     Compensator: (Paraxial
     focus, Optimize All,
     None). We want the
     paraxial focus to be the
     compensator, which is
     already the default.
   • Check “Force Ray
     Aiming On” (makes
     more accurate, but
     slower)
   • You can also check
     “Show Compensators”
     (for example to see
     how much focus
     changes for example).
                                                Zemax - results
•   Here are the results:
•   Analysis of Tolerances
•   File : C:\Documents and Settings\shvisc\Desktop\HW4.zmx
•
•
    Title: Focusing doublet
    Date : TUE DEC 5 2006
                                                                                        Numbers needed to calculate the sensitivities:
•   Units are Millimeters.
•   Paraxial Focus compensation only.
•   WARNING: Boundary constraints on compensators will be ignored.                            Perturbations                          Change in merit function
•   Criteria        : RMS Wavefront Error in waves
•   Mode              : Sensitivities
•   Sampling            : 20
•   Nominal Criteria : 0.00065152
•   Test Wavelength : 0.6328
•   Fields: Y Symmetric Angle in degrees
•   #      X-Field      Y-Field     Weight VDX VDY VCX VCY
•   1 0.000E+000 0.000E+000 1.000E+000 0.000 0.000 0.000 0.000
•   Sensitivity Analysis:
•                                        |----------------- Minimum ----------------| |----------------- Maximum ----------------|
•   Type                   Value           Criteria         Change                         Value Criteria           Change
•   TRAD 2             -0.100000000 0.001543200 0.000891675 0.100000000 0.001773699 0.001122174
•   TRAD 3             -0.100000000 0.000721251 6.9726E-005 0.100000000 0.000642781 -8.7431E-006
•   TRAD 4             -0.100000000 0.002301125 0.001649600 0.100000000 0.002559580 0.001908056
•   TRAD 5             -0.100000000 0.000888400 0.000236876 0.100000000 0.000731590 8.0066E-005
•   TTHI 2 0          -0.100000000 0.001036787 0.000385263 0.100000000 0.000845486 0.000193961
•   TTHI 3 0          -0.200000000 0.004974029 0.004322505 0.200000000 0.004698490 0.004046966
•   TTHI 4 0          -0.100000000 0.000693073 4.1548E-005 0.100000000 0.000828411 0.000176886
•   TEDX 2 3            -0.100000000 0.009626142 0.008974618 0.100000000 0.009626142 0.008974618
•   TETX 2 3           -0.100000000 0.005722684 0.005071160 0.100000000 0.005722684 0.005071160
•   TEDX 4 5            -0.100000000 0.009681031 0.009029507 0.100000000 0.009681031 0.009029507
•   TETX 4 5           -0.100000000 0.011549130 0.010897605 0.100000000 0.011549130 0.010897605
•   TIRX 2           -0.100000000 0.017751740 0.017100215 0.100000000 0.017751740 0.017100215
•   TIRX 3           -0.100000000 0.031032656 0.030381132 0.100000000 0.031032656 0.030381132
•   TIRX 4           -0.100000000 0.063785240 0.063133716 0.100000000 0.063785240 0.063133716
•   TIRX 5           -0.100000000 0.034639912 0.033988387 0.100000000 0.034639912 0.033988387
•   TIND 2           -0.000500000 0.000890818 0.000239294 0.000500000 0.000735714 8.4190E-005
•   TIND 4           -0.000500000 0.000814628 0.000163103 0.000500000 0.000998033 0.000346509
                        Zemax - results cont.
•   Worst offenders:
•   Type                     Value     Criteria Change
•   TIRX 4            -0.100000000 0.063785240 0.063133716
•
•
    TIRX 4
    TIRX 5
                        0.100000000 0.063785240 0.063133716
                      -0.100000000 0.034639912 0.033988387
                                                                         Worst Offenders
•   TIRX 5              0.100000000 0.034639912 0.033988387
•   TIRX 3            -0.100000000 0.031032656 0.030381132
•   TIRX 3              0.100000000 0.031032656 0.030381132
•   TIRX 2            -0.100000000 0.017751740 0.017100215
•   TIRX 2              0.100000000 0.017751740 0.017100215
•   TETX 4 5             -0.100000000 0.011549130 0.010897605
•   TETX 4 5              0.100000000 0.011549130 0.010897605
•   Estimated Performance Changes based upon Root-Sum-Square method:
•   Nominal RMS Wavefront : 0.000651524
•   Estimated change              : 0.081762126
•   Estimated RMS Wavefront : 0.082413650
•   Compensator Statistics:
•   Change in back focus:
•   Minimum              :      -0.327629
•   Maximum                :     0.327965
•   Mean              :        0.000030
•   Standard Deviation :            0.105018
•   Monte Carlo Analysis:
•
•
    Number of trials: 20
    Initial Statistics: Normal Distribution                            Monte Carlo
•    Trial      Criteria         Change
•        1 0.045548742 0.044897218
•        2 0.013286277 0.012634752
•        3 0.036228419 0.035576894
•        4 0.009442727 0.008791203
•        5 0.014894832 0.014243307
•        6 0.020252474 0.019600949
•        7 0.047652045 0.047000521
•        8 0.013279680 0.012628156
•        9 0.009529791 0.008878266
•       10 0.088488208 0.087836684
•       11 0.019946472 0.019294947
•       12 0.014766018 0.014114493
•       13 0.008394405 0.007742881
•       14 0.069265579 0.068614055
•       15 0.005727527 0.005076003
•       16 0.026195678 0.025544154
•       17 0.009141888 0.008490364
           Zemax - results
 From these numbers, we can calculate the
  sensitivities by dividing the change in the
  criteria (RMS wavefront) by the
  perturbation.


                 xi  xi    2
                                         0
                                           2

               
           xi            xi
             Zemax - results
• Paste the results
  into Excel and
  calculate the
  sensitivities
  – (A possible place
    for error: mixing up
    degrees and mm
    for the tilt terms.)
                     Zemax - results
• So, how did we do?
• Not too good, but not too bad either,
  nothing is more than an order of
  magnitude off.
    – Possible differences due to using a
      slightly different RMS wavefront error
      as the criteria:
        • I used on the homework: “RMS (to
          centroid) from integration of the rays”
        • Zemax used RWCE: “RMS (to
          centroid) from integration of the fixed
          coefficients”
        • The one with the -734% difference is
          due to the insensitivity of that
          perturbation
        • Zemax also calculates the change in
          criteria differently (doesn’t do a root
          sum square) – see next slide
  Zemax - results
   0  1   2   ...
      2         2        2
             Conclusions
• Zemax is very powerful and has many
  tolerancing design capabilities.
• You must understand how Zemax does
  the sensitivity analysis before you can
  blindly use it.
                        References
•   http://zemax.com/appnotes/tolerancing_example/index.html
•   http://www.optima-research.com/Software/Optical/Zemax/tolerancing.htm
•   Zemax Users Manual

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:173
posted:5/23/2012
language:Latin
pages:29