Tolerances. WikiOptics. WikiOptics

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1 Tolerances 2014

2 Optical system design Robert E. Fischer/ Biljana Tadic-Galeb 2

3 Candidate Tolerances for a reasonable performance lens(p.322) Parameter Tolerance Parameter Tolerance Radius Testplate measurement accuracy Tilt 0.05-mm TIR Power fit to testplate Surface irregularity Three fringes Decenter ±0.05mm One fringe Refractive index ±0.001 Thickness ±0.05mm Abbe number ±0.8% Air space ±0.05mm Glass inhomogeneity ± Wedge/centration mm TIR 3

4 Relative cost of manufacturing as a function of the level of tolerance(p.335) Diameter tolerance in millimeters Center thickness tolerance in mm Stain charac. Of the glass # of lenses Per block 100 Eccen. Toler. In light dev. Figure tolerance in λ Dia. to. thick. Ratio(fig.3-1) Beauty defects (MIL-C-13830A) Raw glass cost In 100lb lots Coating specifications ±0.10 ±0.05 ±0.025 ± > ±0.20 ±0.10 ±0.05 ±0.025 ± min 3min 2min 1min 30sec 15sec /2 2 1/4 1 1/ $3.00 $5.00 $8.00 $15.00 $25.00 $50.00 $ unctd Mg.Fl. 3-4 layer >4 layers

5 1999 Relative Manufacturing Costs Using Deterministic CNC Processing(p.381) Variable Diameter (mm) Thickness (mm) Stain Cosmetics (Scr-Dig) Test (fringes) Wedge (arc min) Doublets (arc min) Aspect ratio Delivery time (weeks) More difficult ±0.10 ±0.05 ±0.025 ± > $100 $100 $102 $105 $125 ±0.20 ±0.10 ±0.05 ±0.025 ±> $100 $103 $115 $140 $200 < $100 $103 $110 $140 $ $100 $100 $120 $150 $ /2 1-1/4 1/2-1/8 $100 $105 $125 $175 $ /2 ¼ $100 $105 $110 $125 $ <1/2 $100 $105 $110 $150 $200 <10:1 15:1 20:1 30:1 50:1 $100 $120 $175 $250 $ $100 $110 $130 $170 $200 5

6 Typical Manufacturing Tolerances(p.382) OPTIMAX Commercial Quality Precision Quality Manufacturing Limits Glass quality(n d ) ±0.001 ± Melt controlled Diameter(mm) +0.00/ / / Center thickness(mm) ±0.150 ±0.050 ±0.010 Sag(mm) ±0.050 ±0.025 ±0.010 Radius(%) ±0.2 ±0.1 ±0.025 Power-irregularity(fringe) Aspheric profile(μm) ±25 ±1 ±0.5 Wedge lens(tir,mm) Prism angles(tia,arc min) ±3 ±0.5 ±0.1 Bevels(maximum face width at 45,mm) No bevel SCR DIG AR coating(average R) MgF2R<1.5% BBAR,R<0.5% Custom, design 6

7 Field Guide to Optomechanical design and analysis Katie Schwertz James H. Burge 7

8 Tolerance guide for lenses(p.114) Parameter Baseline Precision High precision Lens diameter ±100μm ±25μm ±6μm Center thickness ±200μm ±50μm ±10μm Radius of curvature(%) Radius of curvature(sag) 0.50% 0.10% 0.05% 20μm 2μm 0.5μm Wedge 5arcmin 1arcmin 15arcsec Surface irregularity λ λ/4 λ/20 Surface finish 5nm rms 2nm rms 0.5 nm rms Scratch/dig 80/50 60/40 20/10 Clear aperture 80% 90% >90% 8

9 Tolerance guide for glass properties(p.114) Parameter Baseline Precision High precision Refractive index from nominal Refractive index measurement Refractive index homogeneity Dispersion from nominal ±5x10-4 (Grade3) ±3x10-4 (Grade2) ±2x10-4 (Grade1) ±1x10-4 ±5x10-6 ±2x10-6 ±2x10-5 (H1) ±0.8% (Grade4) ±5x10-6 (H2) ±0.5% (Grade3) ±5x10-6 (H4) ±0.2% (Grade1) Stress birefringence 20nm/cm 10nm/cm 4nm/cm Bubbles/inclusions> 50μm (area of bubbles per 100cm 3 ) Striae-based on shadow graph test 0.5mm 2 0.1mm mm 2 (Class B0) Fine Small, in One direction None detectable 9

10 Tolerance Guide for injection-molded Plastics(p.115) Parameter Low cost Commercial Precision Focal length(%) ±3-5 ±2-3 ±0.5-1 Radius of curvature(%) ±3-5 ±2-3 ± Power(fringes) Irregularity (fringes/10mm) Scratch/dig 80/50 60/40 40/20 Centration ±3 ±2 ±1 Center thickness ±0.1 ±0.05 ±0.01 Radial displacement(mm) Lens to lens repeatability Diameter thickness ratio 2:1 3:1 5:1 Bubbles and inclusions - 1x0.16 1x0.10 Surface imperfections - 2x0.10 2x0.06 Surface roughness (mm rms)

11 Tolerance guide for Machined parts(p.115) Machining level Metric English Coarse dimensions (not important) Typical machining (low difficulty) Precision machining (readily available) High precision (needs special tooling) ±1mm ±0.040 ±0.25mm ±0.010 ±0.025mm ±0.001 <±0.002mm <±

12 Lens design fundamentals Rudolf Kingslake R. Barry Johnson 12

13 Optics manufacturing tolerances for glass(p.7) Attribute Commercial Quality Precision quality Manufacturing limits Glass Quality(n d,v d ) ±0.001, ±0.8% ±0.0005, ±0.5% Melt controlled Diameter(mm) +0.00/ / / Center Thickness(mm) ±0.150 ±0.050 ±0.025 Sag(mm) ±0.050 ±0.025 ±0.010 Clear Aperture 80% 90% 100% Radius ±0.2% or 5 fr ±0.1% or 3 fr ±0.0025mm or 1 fr Irregularity-Interferometer(fringes) Irregularity-Profilometer(microns) ±10 ±1 ±0.1 Wedge Lens(ETD, mm) Wedge Prism(TIA,arc min) ±5 ±1 ±0.1 Bevels(face width@45,mm) <1.0 <0.5 No Bevel Scratch-Dig(MIL-PRF-13830B) Surface Roughness(Å rms) AR Coating(R ave ) MgF 2 R<1.5% BBAR,R<0.5% Custom Design 13

14 Optics Manufacturing Tolerances for Plastics(p.8) Attribute Radius of Curvature ±0.5% EFL ±1.0% Center Thickness Diameter Wedge(TIR) in Element S1 to s2 displacement(across the mold parting line) Surface Figure Error Surface Irregularity Tolerances(rotationally symmetrical elements less than 75mm in diameter) ±0.020mm ±0.020mm <0.010mm <0.020mm Scratch-Dig Specification Surface Roughness Specification (RMS) <50Å Diameter to Thickness Ratio <4:1 Center thickness to Edge Thickness Ratio <3:1 Part to Part Repeatability(one cavity) <0.50% 2 fringes per inch(2 fringes =1λ) 1 fringes per inch(2 fringes =1λ) 14