1. “Budgeting” of Optical Systems
A Tutorial on Optomechanical Tolerancing and a Synopsis of the Economics Involved
Ezra Milby
OPTI 521 – Optomechanical Engineering
Fall 2009 – Prof. J.H. Burge

2. Overview Defining a System Performance Characteristic
Defining the Variable Parameters of the System
Creating a Tolerance Budget
Analyze Production Costs
Iterate the Design Process for Optimization
22 September 2018
E. Milby - OPTI521 - Intro to Optomech Eng

3. Performance Characteristics
Image Quality
Physical Parameter
MTF
Resolution
Energy Distribution
Spot Size
Wavefront Error
Beam Divergence
Geometrical Aberrations
PSF
Bore sight Shift
Effective Focal Length
Back Focal Length
Distortion
Image Plane Displacement
Test
22 September 2018
E. Milby - OPTI521 - Intro to Optomech Eng

4. MTF WRT Defocus Error 22 September 2018
Source: Smith (1985)
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E. Milby - OPTI521 - Intro to Optomech Eng 4

5. Primary Parameters Sag (A) Spacer Thickness (B) Contact Diameter (C)
A variable parameter that is independent of adjustments in other parameters.
Sag (A)
Spacer Thickness (B)
Contact Diameter (C)
Surface Radii (R)
Airspace
Source: Magarill (1999)
22 September 2018
E. Milby - OPTI521 - Intro to Optomech Eng

6. Primary Parameters Center Thickness Surface Sag Index of Refraction
Contact Diameter
Axial Seat Position
Clearance
Wedge
Seat Tilt
Contact Diameter Eccentricity
Surface to Surface Displacement
Base Diameter Eccentricity
Second Barrel Clearance
22 September 2018
E. Milby - OPTI521 - Intro to Optomech Eng
Source: Magarill (1999)

7. Common Variable Parameters
Optics
Assembly
Index of Refraction
Radius
Irregularity
Thickness
Sag
Diameter
Wedge
Surface Roughness
Airspace
Decenter – Axially
Decenter – Laterally
Tilt
Lens Roll
22 September 2018
E. Milby - OPTI521 - Intro to Optomech Eng

8. Assign Tolerances
Base Cost

9. Tolerance Budget Assign a Tolerance Determine Sensitivity
Error Type
Units
Tolerance
Tolerance Value
Sensitivity
WF Error Φ (λ)
L1 Tilt
deg
+/- 0.10
0.1
0.132
0.011
L1 Decenter mm
+/- 0.09
0.09
0.187
0.019
Airspace
1.1
0.016
0.003
L2 Tilt
0.192
0.018
L2 Decenter
0.186
RSS
0.036
Assign a Tolerance
Determine Sensitivity
Determine Performance Degrade
Adjust as Needed

10. Cost Assign a cost sensitivity in tolerance budget C = P·T + B
Adjust tolerances to minimize cost in the same way
Source: Willey (1984)
22 September 2018
E. Milby - OPTI521 - Intro to Optomech Eng

11. Glass Costs
Source: Willey (1992)
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E. Milby - OPTI521 - Intro to Optomech Eng

12. The Cost of Computing Engineering Salary Cost Savings Mass Production
Source: Willey (1983)
Mass Production
High Cost Materials
22 September 2018
E. Milby - OPTI521 - Intro to Optomech Eng

13. The Iterative Tolerancing Process
22 September 2018
Source: Ginsberg (1981)
E. Milby - OPTI521 - Intro to Optomech Eng

14. Sources
Burge, J. (2009). System LOS, RSS combination - Class Notes OPTI521.
Ginsberg, R. H. (March/April 1981). Outline of tolerancing (from performance specification to toleranced drawings). Optical Enginerering ,
Lagger, J. P. (1982). Cost-Effective Design --- A Prudent Approach to the Design of Optics. Photnics Spectra ,
Magarill, S. (1999). Optomenchanical sensitvity and tolerancing. SPIE Conference on Optomechanical Design and Engineering, (pp ). Denver, Colorado.
Smith, W. J. (1985). Fundamentals of Establishing an Optical Tolerance Budget. Proc. of SPIE Vol. 0531, Geometriucal Optics, ed. Fischer, Price, Smith .
Willey, R. (1983). Economics in optical design, analysis, and production. Optical System Design, Analysis, and Production, SPIE Vol. 399 ,
Willey, R. (1992). Maximizing production yeild and performance in optical instruments through effective design and tolerancing. Critical Review Vol. CR43, Optomechanical Design .
Willey, R. (1983). Minimized cost through optimization tolerance distibution in optical assemblies. Proc. of SPIE Vol. 0389, Optical Systems Engineering III ,
Willey, R. R. (1984). The Impact of Tight Tolerance and Other Factors on the Cost of Optical Components. Proc. of SPIE Vol. 0518, Optical Systems Engineering IV, ed. P.R> Yoder Jr. , (pp ).
22 September 2018
E. Milby - OPTI521 - Intro to Optomech Eng