Optical Design Compensation from Engineering to Production Manufacturing

C. Theodore Tienvieri, Tim Rich

Corning Tropel Corporation 60 O’Connor Rd Fairport, NY 14450 [email protected], [email protected]

Abstract: This paper will discuss transitioning a precision optical system from engineering to a manufacturing process stream.

OCIS codes: (220.3620) Lens design; (220.3630) Lenses; (220.4610) Optical fabrication

1. Introduction

Many optical systems for precision applications such as optical inspection, micro-lithography, DVD mastering, and projection printing require significant optical engineering involvement to support the manufacturing team in fabricating these systems. Performance demands placed upon lenses used in these industries often dictate diffraction limited wavefront quality, minimal image distortion, and resolution of very small features. Achieving the necessary “as-built” performance requirements for the lens assembly can mean optical designer involvement to select and compensate manufactured parts, prior to release to the component assembly team. This level of detailed engineering involvement is suitable for proto-type quantities but can constrain the manufacturing stream when the system transitions to sizeable production quantities. Support in the manufacture of volume assemblies can require a dedicated team of optical design engineers to manage the day to day project needs of lens selection and compensation in order to keep pace with the program’s delivery rate. A second option to manage the engineering duties of precision optical systems is to develop a manufacturing stream which enables transferring and transitioning designer project support to the assembly and fabrication teams.

2. Manufacturing Philosophy and Key Components

In producing many state of the art optical systems, the manufacturing strategy hinges around a philosophy whereby each fabricated objective is first modeled and simulated in optical design software prior to committing to assembling the components (figure 1). A group of lens elements will first be custom selected from the population of manufactured parts to minimize aberration build up. The component’s measured fabrication properties (radius, thickness, index,…) will be modeled in design code and further performance gains achieved by optimizing with pre- determined air spaces.

SELECTION of MANUFACTURED SYSTEM EVALUATE RELEASE to COMPONENTS COMPENSATION PERFORMANCE MANUFACTURING

Fig. 1 Manufacturing Philosophy

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Downloaded From: http://spiedigitallibrary.org/ on 05/28/2013 Terms of Use: http://spiedl.org/terms Mechanical parts will be adjusted accordingly to achieve desired lens spacings. This manufacturing concept allows for looser optical fabrication tolerances as opposed to building a static objective. Fine tuning and computer simulation of each optical assembly has often been the task of the optical designer. This methodology is fine for small quantity production, but how might it be applied to producing optical systems with sizeable volume?

A manufacturing strategy has been developed to create a Volume Manufacturing Compensation Platform (VMCP) for quantity production of high performance optical systems. A suitable software platform and suite of compensation tools has been implemented to integrate optical design support duties to a volume manufacturing stream (VMS). The key components of the platform (figure 2) consist of an integrated computer network accessible to design and manufacturing, electronic fabrication records stored in a Lens Manufacturing Database (LMD)[1], optical design analysis/compensation software, and lens assembly report specific to each manufactured lens unit. This infrastructure lends itself to automating the design compensation process, which allows for incorporation into a production VMS.

Lens Manufacturing Database (LMD)

Optical Design Code OPTICAL DESIGN Build Solution Compensation

Assembly Mechanical MANUFACTURING Report

Fig. 2. Volume Manufacturing Compensation Platform

3. Project Requirements for VMCP

There are basic requirements the project must fulfill to be integrated into the VMCP. The volume must be large enough to justify spending time and effort to develop the underlying software code to manage the data collection, design optimization, solution tracking, and reporting. In many optical projects if more than one to two dozen lenses are to be manufactured, the investment effort will be re-couped.

The design compensation strategy must be robust, well understood, and characterized. This means the system compensation algorithm does not need to be fine tuned or adjusted on a set by set basis to yield an acceptable solution. The tolerance budgets need to be carefully assigned to different manufacturing parameters such as optics, mechanics, assembly, and test. This aids in establishing acceptance threshold criteria to judge if a lens solution can be released to assembly for building.

4. VMCP and Operation

The VMCP is developed to be compatible with a variety of different lens systems, complexities, compensation paths, and manufacturing requirements. Each lens system has its own unique built in performance metrics and compensation processes which need to be adhered to. These parameters are decided jointly between the lens design

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Downloaded From: http://spiedigitallibrary.org/ on 05/28/2013 Terms of Use: http://spiedl.org/terms and manufacturing teams. Necessary process information is committed to work procedures and flow diagrams. An optical designer generally oversees the project’s development and integration into the VMCP. The design quality metrics computed in the software consist of parameters utilized to judge adherence to design tolerances, specification, and any merits which may be quantified in the test laboratory. For example, theoretical performance merits evaluated could include wavefront RMS and spherical aberration, which could then be verified by interferometry in the test lab.

Running design compensations with the VMCP is relatively simple. The optical elements to be assembled are selected from the Lens Manufacturing Database. An implemented LMD facilitates this process by a simple point and click user interface (figure 3). Components are grouped by their project designated set number or available stock elements. Each lens component is compared to manufacturing specifications and the impact to performance computed. This information is utilized to quickly determine the performance change due to a particular component being placed into a lens assembly. The lens set’s specific manufactured data (radius, ct, index,…) can easily be exported to optical design code for optimization and analysis.

E!SdIImfllthI LSy%ISIOS 063Tiger Objective System & Set # St 1093 ..:J Designation

DST I L9 30.1167 30.0000 0.116756.4%0.00 0.00 0.00 0.707 -0.006 -0.0096-0.0225-0.02460.00660.0014 2 FIB 16.4064 16.3500 0.056477.9%0.00 -0.03 -0.05 1.063 -0.017 0.1606 -0.0464-0.01330.0233-0.0102 3 72 9.0600 9.0000 0.060060.0%0.00 -0.02 -0.05 0.969 -0.0110.1379 -0.0156-0.01530.00470.0075 4 194-04 25.009625.00000.0096l9.2T 0.00 -0.01 -0.01 0.301 -0.025 0.0429 -0.0051-0.0069-0.0035-0.0005 5 64-04 30.5616 30.5500 0.031663.6%0.01 CURRENT-0.04 -0.03 1.141 SET-0.097 0.09360.01650.0050-0.0036-0.0064 6 L4-04 22.564922.50000.064966.5%0.00 0.00 0.04 -0.142 0.002 0.0069 -0.0079-0.00740.00660.0026 Export to 719426.506726.50000.00676.9T 0.00 DESIGNATION0.00 0.00 0.072 -0.002 0.0514 -0.0100-0.02160.0074-0.0019 6 15.756015.72000.0360 0.00 0.01 -0.01 0.013 -0.001 -0.01000.0126 -0.01440.00160.0039 36.0% Design Code 9 UI1910 15.0014 15.0000 0.0014 1.4% 0.00 0.00 0.00 0.000 -0.001 0.05790.00330.00450.00ll -0.0015 10 M4-046k5.622955.56500.037937.9%

5] 0.0 -0.1 -0.1 4.144 -0.1560.5520-0.0753 -0.09420.0464-0.0051 Stock – Set ZSF RdiidCT DCdS Controls J!11± 6 STOCK

EI ID CT NCTDI%CT%©1T©I SF6 CMA 650 650 1966 6FL 29 216 225 236 237 2 66 16.345316.3500 -0.0047 -6.3% 0.00 0.00 0.00 -0.066 0.00' 0.0030 -0.04540.0092 -0. 00620.0039 2 610 16.354016.3500 0.0040 5.3% 0.00 0.00 0.00 0.073 -0.001 0.1261 -0.0567 -0.00670.0151-0.0030 V 2 35 16.355316.3500 0.0053 7.1% 0.00 0.00 0.00 0.096 -0.002 -0.0065-0.036' -T.01330.00400.0107— 2 67 16.355616.3500 0.0056 7.7% 0.00 0.00 -0.010.106 -0.002 -0.0067-0.0270 -T.02110.01900.0043 2 36 16.362616.3500 0.0126 17.1%0.00 -0.01 -0.010.233 I -0.004 0.0406 -T.03300.01330.0201I-o.ooss 2 34 16.365616.3500 0.0156 20.6%0.00 -0.01 -0.010.264 -0.005 0.0196 -0.0027 1-0.0299 1-0.00030.0040 2 12 16.369516.3500 0.0195 26.0% STOCK0.00 -0.01 -0.020.355 ELEMENTS-0.006 0.0194 -T.05640.01360.0117-0.0064 2 HI 16.374916.3500 0.0249 33.2%0.00 -0.01 -0.020.453 -0.007 0.0526 -0.0176 -0.01690.0246-0.0076 3 ITS 6.93069.0000 -0.0692 -92.3%0.00 0.03 0.06 -1.140 0.012 0.14560.0110-0.01660.0299-0.0333 3 lIT 6.96469.0000 -0.0352 -46.9%0.00 0.0' 0.03 -0.560 0.006 0.1046 -0.0027 -T.03260.01460.0079 S F:9 6H1Srnhl -57(04-Tc%Tr•1Tr•1T70 -0707 57(0 0147007074-57607-Tr6TSTfllSO

Fig. 3. Project Element Selection Interface in LMD

Additional set unique mechanical and as-built air space data, stored in the assembly mechanical report, can be exported, combined with the element LMD information and compensated with the VMCP. At the end of the lens compensation phase, performance merits are evaluated against the threshold criteria. If acceptable performance is achieved, the manufacturing solution is reported and released to assembly (figure 4).

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Downloaded From: http://spiedigitallibrary.org/ on 05/28/2013 Terms of Use: http://spiedl.org/terms SYSTEM HAS PASSED ALL PERFORMANCE CRITERIA APPROVED FOR RELEASE TO MANUFACTURING LENS NNE: TI*R SET NUMBER: 204 16—May—2 006

DATE SET PARN VALUE LOWER UPPER P/F

16—May—2006 204 RMS POLY 0.0630 0.0200 0.0850 pass 16—May—2006 204 MAG —2. 9168 —2. 9197 —2. 9139 pass 16—May—2006 204 DIST 5.5711 0.0000 10. 0000 pass 16—May—2006 204 DIST C 5.3875 0.0000 10.0000 pass 16—May—2006 204 DOF 52.4630 44.0000 60.0000 pass 16—May—2006 204 CURV 9.3870 4.5000 12. 7000 pass 16—May—2006 204 ASTIG 10.1010 7.0000 15. 0000 pass 16—May—2006 204 MTF MIN 0.7970 0.7400 0.8500 pass 16—May—2006 204 TT 822. 9996 822. 0000 824. 0000 pass 16—May—2006 204 V—V OBJ 624.7564 624.3000 625.3000 pass 16—May—2006 204 V—IMG 738. 0056 737. 5000 738. 5000 pass 16—May—2006 204 TEL OBJ 2.6182 0.0000 5.0000 pass 16—May—2006 204 TEL 1MG 5.6940 0.0000 10. 0000 pass 16—May—2006 204 MERIT 0.1434 0.1245 0.1650 pass

AIR SPACE REPORT 16—May—2 006 TIGER SET 204

SPACE VALUE

2—3 26.3393 1r2—3r1 295.0679 3—4/5 29.2131 Cern 0.0332 4/5—6 0.6479 6—Stop 26.4398 '.7 110 U40

Fig. 4. Objective performance and solution report

Should the design fail to achieve acceptable performance, the solution is not released to manufacturing and the user is recommended to alter the mix of selected elements and re-run the compensation.

The VMCP includes history information. Each time a lens system is run on the platform, performance and compensation data is archived. Historical project data can be reviewed for manufacturing performance trends, adherence to specification, and statistics.

5. Design Transition to Volume Production

The VMCP architecture permits easy transition of lens system support from proto-type to volume production. This platform offers several advantages to the manufacturing community. Manufacturing personnel can take over many of the routine project support design duties that have traditionally been performed by an optical designer. This alleviates dependence by manufacturing upon the engineering staff for day to day project support. The cycle time for design compensation is greatly reduced as the process is automated. Each system within a project is uniformly compensated with the same tools, variables, and methodology. Multiple users can easily be trained to run the VMCP allowing for additional staff versatility within programs. Each individual project maintains it own custom compensation strategy and unique set of performance merits. The threshold criteria dictate to the user if it’s acceptable to build a particular lens set. This eliminates many of the subjective performance decisions that have routinely been made by an optical designer. Any modifications and changes in compensation philosophy would need to be reviewed by an optical designer before implementation into the VMCP.

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6. Summary

A manufacturing compensation and analysis stream has been developed to assist with the manufacturing support duties of production optical systems. This concept can be utilized to transition/transfer optical designer engineering system support activities directly to manufacturing personnel. This can include selection of system parts to be assembled, analysis, and compensation of these parts prior to committing to building. Manufactured lens data and mechanical assembly measurements can be built into design models to predict what level of performance may be achieved by a given assembly. If performance is acceptable, the parts can be released for assembly. This streamline process circumvents engineering involvement in production activities and allows for manufacturing to transition designs from proto-type to volume.

References

1. Tienvieri, C., et al, “Modern lens design using a lens manufacturing database”, SPIE Proceedings, IODC 1998, vol 3482, pp. 508-518.

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