Precision Production: Enabling
deterministic throughput for
precision aspheres with MRF
Introduction
Aspheres are replacing spherical optics in many applications. A method of production manufacturing for precision aspheres is needed in most optical fabrication facilities. Qflex MRF platforms enables deterministic and efficient throughput for series production of aspheres. Thorlabs in Newton, New Jersey, USA has provided data from a batch of aspheres to demonstrate how MRF can be efficiently used in a production environment to manufacture highprecision aspheres.
Manufacturability of highprecision
aspheres is enabled by MRF
Asphere manufacturability concerns
 Manufacturability of aspheres is difficult using artisanbased polishing
 Lead times are not predictable using nondeterministic methods
Asphere manufacturability solutions
 Computercontrolled optics manufacturing replaces skillintensive manufacturing process
 MRF provides a solution for deterministic figure correction and throughput for highprecision aspheres
 Asphere production is costeffective and affordable
 Qflex 100 MRF machine on the shop floor at Thorlabs in Newton, NJ USA
Qflex 100 MRF machine on the shop floor
at Thorlabs in Newton, NJ USA
What is a highprecision in asphere?
Thorlabs defines their highprecision line of aspheres as being diffraction limited at discrete wavelengths
 A Strehl ratio >0.8 is generally accepted as diffraction limited
 What is the Strehl ratio?
 Ratio of the peak intensity of the measured PSF divided by the maximum intensity of the perfect diffraction limited PSF
 S= (I(x=0))/(P(x=0))
K. Strehl Zeitschrift für Instrumentenkunde 22, p. 213, 1901.
MRF enables diffraction limited
highprecision aspheres
Traditional CNC polishing techniques cannot achieve the required
irregularity in the aspheric lens to the diffractionlimited design
Specifications for Precision Asphere  CNCPolished
 Irregularity <750nm RMS
 Wavefront error: <500nm RMS
Specifications for Diffraction Limited HighPrecision Asphere – MRF Polished
 Irregularity: <55nm RMS
 Slope: <200µrad PV
 Wavefront error: Diffraction limited
 Slope & Irregularity specifications are chosen to produce a diffraction limited wavefront error
Thorlabs can now offer two product lines.
HighPrecision Batch Production
Actual batch production process flow at Thorlabs
 Spot Taking ~15 minutes
 Job Setup ~15 minutes (including queuing 1st part)
 Average run time ~12 minutes (center, probe, run)
 Metrology & Queue time ~5 minutes (process metrology, solve, complete )
All runs queued while parts were polishing
 ~2.5 hours needed to MRF a batch of 10 optics
 Resulting throughput
 A highprecision asphere every ~15 minutes
Batch of 10 Aspheres – CNC Polished
 10 CNC polished aspheres (AL2550) were taken from inventory to be MRF’d
Batch of 10 Aspheres  After MRF
After 1 MRF iteration all 10 aspheres are now highprecision diffraction limited aspheres (AL2550H).
MRF provides manufacturing confidence and predictable throughput 100% yield after one 15minute iteration on each surface.
RMS irregularity improvement using MRF
 Irregularity specification: < 55 nm RMSBefore MRF average irregularity:
 100 nm RMS
 After MRF average irregularity: 15 nm RMS
 An average of ~7x RMS improvement is seen on this batch after 1 MRF iteration!
Conclusions
MRF enables deterministic throughput

100% yield on batch of 10 aspheres after 1 MRF iteration

2.5 hours of total machine setup and polishing time was required
 In this case, ~15 minutes can be budgeted for each asphere
 Throughput can be estimated for a batch of optics with any shape or size
MRF empowers deterministic figure correction
Qflex MRF platform supports batch processing
 Less setup time
 Improved throughput
Qflex software enables deterministic and efficient throughput for series production of aspheres
 Accurately quote new jobs
 Predictable schedules
 Ontime delivery