“Budgeting” of Optical Systems

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 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 E. Milby - OPTI521 - Intro to Optomech Eng

4. MTF WRT Defocus Error Source: Smith (1985) 30 November 2009 E. Milby - OPTI521 - Intro to Optomech Eng 4

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

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

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 E. Milby - OPTI521 - Intro to Optomech Eng

8. Assign Tolerances Base Cost

9. Tolerance Budget • Assign a Tolerance • Determine Sensitivity • Determine Performance Degrade • Adjust as Needed

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

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

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

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

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 , 175-180. • Lagger, J. P. (1982). Cost-Effective Design --- A Prudent Approach to the Design of Optics. Photnics Spectra , 65-68. • Magarill, S. (1999). Optomenchanicalsensitvity and tolerancing. SPIE Conference on Optomechanical Design and Engineering, (pp. 220-228). 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 , 106-111. • 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 , 12-17. • 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. 106-111). E. Milby - OPTI521 - Intro to Optomech Eng