Lesson 5 – Modern Subaperture Polishing Technologies

What You Will Learn

Identify common subaperture polishing technologies.
Compare the advantages of different polishing methods.
Recognize where each technology is commonly used.
Understand why no single process works for every application.
Describe the role of UltraForm Finishing in modern optics manufacturing.

Why Multiple Technologies Exist

There is no single polishing process that works best for every optical component. Different materials, surface shapes, production volumes, and accuracy requirements often require different polishing technologies. Some processes are designed for rapid material removal, while others focus on producing extremely smooth surface finishes or correcting small figure errors. Selecting the right technology depends on the requirements of the optical component being manufactured. Understanding the strengths of each process helps technicians choose the most effective polishing method.

Common Subaperture Polishing Processes

Several deterministic polishing technologies are widely used throughout the optics industry.

Computer Controlled Small Tool Polishing (CCSTP) uses rotating polishing tools to remove material through carefully controlled dwell times. It is commonly used for precision lenses and mirrors.

Magnetorheological Finishing (MRF) uses a magnetic field to stiffen a polishing fluid during machining. This process provides excellent control and is often used for final figure correction.

Ion Beam Figuring (IBF) removes material without physical contact by directing a focused ion beam onto the optical surface. It is typically used for extremely high-precision corrections after conventional polishing has been completed.

UltraForm Finishing (UFF) combines precision CNC motion with compliant polishing tools, advanced metrology, and flexible programming. It is especially effective for aspheres, freeform optics, and complex optical geometries.

Choosing the Right Process

The selection of a polishing technology depends on several factors. Large figure corrections often require faster polishing methods, while final finishing may require slower processes capable of producing nanometer-level accuracy. Surface geometry also affects process selection. Simple spherical optics may be manufactured using conventional polishing techniques, while steep aspheres or freeform surfaces typically require deterministic polishing. Production volume, equipment cost, cycle time, and available metrology also influence the final decision.

Why UltraForm Finishing Is Important

UltraForm Finishing was developed to provide manufacturers with a flexible polishing system capable of handling many different optical geometries on a single machine. By combining precision CNC motion with advanced metrology and software, UFF allows operators to produce spherical, aspheric, and freeform optics while maintaining excellent process control. Because machine parameters are programmable, the same equipment can often support multiple product lines with minimal hardware changes. This flexibility has made UFF an increasingly popular technology in research laboratories and production facilities.

Interactive Technology Comparison

The Technology Comparison widget allows you to compare CCSTP, MRF, IBF, and UFF side by side. You can review their advantages, limitations, removal rates, typical applications, and achievable surface quality. Exploring these differences will help you understand why manufacturers often combine several polishing technologies during the production of a single optical component.
Interactive Technology Comparison

Interactive Technology Comparison

Compare CCSTP, MRF, IBF, and UFF side by side to see where each polishing technology performs best.

Choose Technologies to Compare

Selected Technologies4

Highest Removal RateCCSTP

Best Fine CorrectionIBF

Broadest Geometry RangeUFF

Comparison Area	CCSTPComputer-Controlled Small Tool Polishing	MRFMagnetorheological Finishing	IBFIon Beam Figuring	UFFUltraForm Finishing
Advantages	Flexible tooling, relatively high removal, and strong broad corrective polishing.	Highly repeatable removal function, deterministic control, and excellent finish.	No mechanical contact, extremely precise correction, and minimal tool stress.	Adapts to complex aspheres and freeforms with controlled local removal.
Limitations	Tool wear, edge effects, and process stability must be managed.	Specialized fluid and equipment; some geometries and materials are challenging.	Slow removal, high equipment cost, and vacuum processing.	Requires accurate calibration, advanced motion control, and stable setup.
Relative Removal Rate	High	Medium	Low	Medium–High
Typical Applications	Bulk correction, aspheres, large optics, and pre-finishing.	Precision aspheres, high-value optics, final correction, and finish improvement.	Final nanometer-scale figuring, delicate optics, and post-polish correction.	Complex aspheres, freeforms, local corrections, and difficult regions.
Achievable Surface Quality	Good	Excellent	Excellent figure control	Very Good
Complex Geometry Capability	Good	Very Good	Good with line of sight	Excellent

Why Manufacturers Combine Technologies

No single process is best at every stage. A faster technology may perform the initial correction, followed by a slower and more precise process for final figure and surface quality.

Example Combined Process

CCSTP Bulk Correction→UFF or MRF Refinement→IBF Final Figuring

All four technologies are selected. Compare their strengths to see how they can support different stages of one manufacturing process.

Each polishing technology has unique strengths, but this course focuses on UltraForm Finishing because it combines many deterministic polishing concepts into one flexible manufacturing system. In the next lesson, you’ll examine the UltraForm Finishing machine in detail and learn about its major components, motion system, polishing tools, and software.