Precision Production: Enabling

deterministic throughput for

precision aspheres with MRF

 

Introduction

asphere production case study pict1


Aspheres are replacing spherical optics in many applications. A method of production manufacturing for precision aspheres is needed in most optical fabrication facilities. Q-flex 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 high-precision aspheres.

 Thorlabs1797Red original

 



Manufacturability of high-precision

aspheres is enabled by MRF

 

asphere production case study pict2

Asphere manufacturability concerns

 - Manufacturability of aspheres is difficult using artisan-based polishing

 - Lead times are not predictable using non-deterministic methods

 

Asphere manufacturability solutions

 - Computer-controlled optics manufacturing replaces skill-intensive manufacturing process

 - MRF provides a solution for deterministic figure correction and throughput for high-precision aspheres

 - Asphere production is cost-effective and affordable

 - Q-flex 100 MRF machine on the shop floor at Thorlabs in Newton, NJ USA

Q-flex 100 MRF machine on the shop floor 
at Thorlabs in Newton, NJ USA

 
 
 
 
 

 


What is a high-precision in asphere?

 asphere production case study pict4a

 

 

 

 

 

 

 Thorlabs defines their high-precision 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

high-precision aspheres

 

asphere production case study pict5


Traditional CNC polishing techniques cannot achieve the required
irregularity in the aspheric lens to the diffraction-limited design

Specifications for Precision Asphere - CNC-Polished

  • Irregularity <750nm RMS
  • Wavefront error: <500nm RMS

Specifications for Diffraction Limited High-Precision 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.

 


 

High-Precision Batch Production

asphere production case study pict6

 

 

 

 

 

 

 

 

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 high-precision asphere every ~15 minutes

 

asphere production case study pict7

 

 


Batch of 10 Aspheres – CNC Polished

  • 10 CNC polished aspheres (AL2550) were taken from inventory to be MRF’d

 

asphere production case study pict8

 

 

 


 

 Batch of 10 Aspheres - After MRF


After 1 MRF iteration all 10 aspheres are now high-precision diffraction limited aspheres (AL2550H).

 

asphere production case study pict9

MRF provides manufacturing confidence and predictable throughput 100% yield after one 15-minute 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!

 

asphere production case study pict10a 

             asphere production case study pict10b

 

 


Conclusions

Qflex overview 00015

Thorlabs1797Red original

 

 

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

 

Q-flex MRF platform supports batch processing

  • Less setup time
  • Improved throughput

 

Q-flex software enables deterministic and efficient throughput for series production of aspheres

  • Accurately quote new jobs
  • Predictable schedules
  • On-time delivery