Prototype Optics in One Week

request a quote

OPTICS YOU NEED FAST AND RIGHT.

Submit-RFQ

Freeforms

Customers trust Optimax to create high-quality optics and deliver them fast, and our freeforms are no exception. Designing with freeforms requires fewer elements, lighter weight and increased flexibility for your system.

Freeform optical shapes or optical surfaces are gaining popularity with lens designers and optical system integrators. Now, there are optical fabrication processes that include generation, high-speed VIBE polishing, sub-aperture figure correction, surface smoothing and testing of freeform surfaces.

Optimax produces freeform optics from glass, fused silica, crystals and ceramics for UV, Visible and IR applications using proprietary techniques for low scatter surfaces.

About Freeform Lens Manufacturing

Freeforms are optical shapes or optical surfaces that are designed with little to no symmetry. Manufacturing a freeform is similar to that of a highly complex asphere; surface form and local slope change are all factors that influence the complexity of the shape and the manufacturing process used.

To learn more about freeforms we invite you to visit our Resource Library and read our Technical Papers on the topic.

Optimax Tools

Manufacturing Tolerance Chart
Test Plate Library
Preferred Glass List
Aerospace Glass List

Specifying Freeforms

Specifying a freeform begins by defining the surface. An optical fabricator needs a clear description of the desired final optic; equation, cloud of points or a 3D model.

Manufacturing Limits for Freeform Surfaces

Optimax utilizes deterministic CNC machine tools for predictable removal rates and adherence to tight tolerances. To control centration, precision tools maintain the optical axis.

Manufacturing Limits for Freeform Surfaces

Attribute
 Tolerancing Limit*
Diameter (mm) +0, -0.010
Center Thickness (mm) ± 0.050
Irregularity – Interferometry
(HeNe fringes)
0.1**
 Irregularity – Profilometry (μm)  ±1.0
 Wedge Lens – ETD (mm)
 TBD
 Surface Roughness (Å RMS)  10
* Soft Tolerancing Units **Stitching/CGH dependent

Thin Film Coating Manufacturing Limits

Coating Capabilities
Attribute
Minimum
Maximum
Diameter 3mm 500mm
Wavelength 193nm 6000nm
Use Environment Vacuum >95% RH
Durability Moderate abrasion Severe abrasion
Measurement 68°, s, p, average polarization
Laser Damage Threshold 1064nm: >30J/cm2@10ns, >1MW/cm2CW
Layers 1 200
* Soft Tolerancing Units **Stitching/CGH dependent

Above are manufacturing limits and tolerances specific to thin film coating. For more detailed information, please contact sales@optimaxsi.com.

General Comments on Manufacturing Limits

  • This represents a general list of soft limits and is intended for reference only.
  • As requirements move closer to a min or max shown the more challenging the part will be.
  • Certain combinations may not be possible – Choosing Max Sag and Min Diameter on concave surfaces for example.
  • Interferometric testing of aspheres is extremely case specific. The slower the onset of departure, the more likely interferometric testing is possible.
  • During manufacturing the lens is oversized in diameter. Be aware, forms well behaved within clear aperture may turn exotic or undefined just beyond final diameter.

Manufacturing Limits for Aspheric Surfaces

Based on Form Error Tolerance

Form Error > 2μm Lower Resolution Profilometry (2-D)1
Attribute
Minimum
Maximum
Diameter (mm) 3 250
Local Radius (mm) -8 (Concave)
Sag (mm) 0 502
Departure (mm) 0.01 20
Included Angle (°) 0 120
Form Error 0.5 – 2μm Higher Resolution Profilometry (2-D)1
Attribute
Minimum
Maximum
Diameter (mm)3 3 250
Local Radius (mm) -12 (Concave)
Sag (mm) 0 252
Departure (mm) 0.01 20
Included Angle (°) 0 150
Form Error < 0.5μm Interferometry with Stitching (3-D)
Attribute
Minimum
Maximum
Diameter (mm)3 3 250
Local Radius (mm) -13 (Concave)
Sag (mm) 0 252,4
Departure (mm) 0.002 1
Included Angle (°) 0 120+5
1Typical metrology is Zygo MetroPro plots for interferometry
2For concave surfaces the maximum may be smaller, limited by tool clearance first. Short radii have lower maximums
3Larger diameters can be accommodated using multiscan fusion
4Total sag allowed is a function of diameter, determined by fringe resolution of the interferometer
5Very basic forms (paraboloid, ellipsoid) can have higher included angles

General Comments on Manufacturing Limits

  • This represents a general list of soft limits and is intended for reference only.
  • As requirements move closer to a min or max shown fabrication becomes more difficult.
  • Certain combinations are unattainable, e.g. 3mm convex radius with 100mm length.
  • Certain configurations add significant fixturing costs, e.g. crossed axis cylinders, cylinders/spheres.
  • Interferometric testing of cylinders is somewhat case specific. Aperture coverage is often limited by the range of diffractive nulls available.
  • Length is always the dimension along the plano axis and width is the dimension across the power axis.

Manufacturing Limits for Cylindrical Surfaces Based on Manufacturing Method

Rod or Arbor
Attribute
Minimum
Maximum
Length (mm) 3 5001
Width (mm) Radius dependent 2 < 2x Radius
Cylinder Radius (mm) – Convex Only 2 150
X-Y
Attribute Minimum Maximum
Length (mm) 3 300
Width (mm) 2 300
Cylinder Radius (mm) 10
Concave sag to flat (mm) 0.1002 =Radius
1This is at minimum radius and width. The part-specific minimum will grow in proportion to radius.
2Flat surfaces lead to scratching problems and polisher contact issues. For both practical and economic reasons consider plano here.

General Comments on Manufacturing Limits

    • This represents a general list of soft limits and is intended for reference only.
    • As requirements move closer to a min or max shown, the more challenging the part will be.

Manufacturing Limits for
Prism Surfaces

Attribute
Minimum
Maximum
Diameter (mm) 3 300
Thickness 1 150
Aspect Ratio1 1 502
1Diameter divided by thickness
2This represents highest values obtained. When at maximum other minimums (irregularity) may not be possible. Will be smaller with less well behaved materials.

General Comments on Manufacturing Limits

  • This represents a general list of soft limits and is intended for reference only.
  • As requirements move closer to a min or max shown, the more challenging the part will be.
  • During manufacturing, the lens is over-sized in diameter.

Manufacturing Limits for Spherical Surfaces

Based on Form Error Tolerance

Attribute
Minimum
Maximum
Diameter (mm) 3 400
Radius (mm) ±1 2
Aspect Ratio (Diameter/Center Thickness) <1:1 30:1
Included Angle (°) 0 2103
1Limited by machine envelope
2Metrology dependent. Avoid 3-10 meter radii when possible, choosing to stay plano instead. It will be less expensive too.
3This represents highest values possible. Actual value possible depends on finished and metrology options available plus tolerance range available for a given part.

Here are manufacturing limits and tolerances specific to optical aspheres, prisms, cylinders and spheres. For more detailed information on any attribute, please contact sales@optimaxsi.com.

Common Types of Freeforms

To see more Common Freeforms use the navigate arrows

Testing Freeforms

Optimax inspects 100% of all optics. Test data is provided with prototype orders.

Our metrology must match the sophistication of our manufacturing technology. Optimax offers state-of-the-art metrology, including surface profilers and interferometers to verify that parts meet the form error specification. Testing options are form specific, lenses with mild departure from a best-fit sphere have the highest potential for fractional wave precision.

Fast Delivery

Optimax manufactures a wide variety of optical components. When on-time delivery is crucial, Optimax offers an expedited delivery option with a money back guarantee.

Continued Innovation

Optimax’s R&D department is continuously looking for ways to improve our fabrication process and produce higher quality optics. Our current research projects are designed to meet future market needs.

For more information please see Optimax Innovation or contact sales@optimaxsi.com.

Technical Resources

Absolute freeform surface measurement using interferometry

We will present a case study of a characteristic freeform production optic that required an absolute positioning measurement procedure utilizing a custom dual computer generated hologram (CGH) interferogram set-up

Design and Manufacturing Considerations for Freeform Optical Surfaces

Freeform optical systems are becoming increasingly common due to new design and manufacturing methods. We present an example compact freeform optical system and describe considerations for transfer of the prescription of freeform surfaces for fabrication

The Manufacturing of a Multi-surface Monolithic Telescope with Freeform Surfaces

Monolithic multi-surface telescopes combined with freeform optical surfaces provide improvements in optical performance in a smaller footprint as compared to systems with spherical surfaces, while providing superior mechanical stability to traditional telescope assemblies. Three different monolithic telescope concepts, in different configurations and optical performance were produced as proof of concepts

Scaling-up freeform manufacturing: challenges and solutions

With optical technology and design advances, larger freeform optics are increasingly sought after by consumers for an expanding number of applications. This paper will present some of the challenges and solutions of extending freeform polishing capabilities from approximately 150 mm diameter parts to a component of over 500 mm in diameter

Larger format freeform fabrication and metrology

This paper will address challenges that have been encountered in the manufacturing, testing, and handling of freeforms as their size expands up to and beyond 500 mm, and provide future work that will address each challenge

Challenges in size scale up of freeform polishing processes

This paper will discuss challenges faced as a result of scaling up our freeform polishing process from parts with approximately 150 mm diameters, to polishing components with diameters over 600 mm

Pushing Freeform Optical Manufacturing: Fabricating Optimax’s Largest Freeform Component

Several challenges associated with part size and shape complexity were solved during the manufacture of the largest extreme freeform shape Optimax has fabricated to date

Measurement of mid-spatial frequency errors on freeform optics using deflectometry

Freeform optics have emerged as a new tool for optical designers and integrators. Manufacturing innovations are gradually increasing availability of precision freeform optics.

Top Five Common Freeforms

The top five common freeforms have gained popularity with lens designers and optical system interrogators. 

Integrating Optical, Mechanical and Test Software

Optical systems must perform under environmental conditions including thermal and mechanical loading. To predict the performance in the field, an integrated analysis combining optical and mechanical software is required to understand optical performance. 

Advances in Freeform Optics Fabrication for Conformal Window and Dome Applications

Freeform optical shapes or optical surfaces that are designed with non-symmetric features are gaining popularity. This enabling technology allows for conformal sensor windows and domes that provide enhanced aerodynamic properties

Conformal window manufacturing process development and demonstrations for polycrystalline materials

Conformal windows pose new and unique challenges to manufacturing due to the shape, measurement of, and requested hard polycrystalline materials. Optimax has developed a process for manufacturing conformal windows out of fused silica, glass, zinc-sulfide multispectral, and spinel. 

Metrology for the Manufacturing of Freeform Optics

Freeform optical surfaces are gaining popularity with lens designers and optical system integrators as a method to solve complex optical system design problems. Fortunately, advances in optical manufacturing have opened the possibility for designers to manufacture these complex surfaces

Freeform Optical manufacturing and testing processes for IR Conformal Window and Domes

Freeform optical shapes that are designed with non-symmetric features allow for conformal sensor windows and domes that provide enhanced aerodynamic properties as well as environmental and ballistic protection

Manufacturing and Metrology for IR Conformal Windows and Domes

Freeform and conformal optics have the potential to dramatically improve optical systems by enabling systems with fewer
optical components, reduced aberrations, and improved aerodynamic performance

Fabricating freeform multispectral-ZnS corrector lenses

For more than 100 years, optical imaging systems were limited to rotationally symmetric lens elements, due to limitations in processing optics. However, the present application of CNC machines has made the fabrication of non-rotationally symmetric lenses, such as freeform surfaces, economical

Incorporating VIBE into precision optics manufacturing process

The VIBE™ process is a full-aperture, conformal polishing process that has the potential to be introduced in areas of today’s modern optics manufacturing process

Evolving rocket optics applications drive manufacturing advances

Improvements to sensing hardware and image processing for airborne optical systems have inspired designers to propose new optics and windows to be: more precise, conformal/freeform and multi-functional. 

Tolerancing an Optical Freeform Surface

Freeform optical shapes or optical surfaces that are designed with non-symmetric features are gaining popularity with lens
designers and optical system integrators. Tolerances on a freeform optical design influence the optical fabrication process

The need for Fiducials on Freeform Optical Surfaces

Freeform surfaces typically have little to no symmetry, making the alignment of the surfaces difficult. Fiducials are required to achieve higher accuracy measurements of freeform optical surfaces

Importance of Fiducials on Freeform Optics

Freeform optical surfaces, which have little to no symmetry, are gaining popularity with lens designers and optical system integrators. Using fiducials properly leads to higher accuracy measurements and allows more control of the surface throughout the manufacturing process

Manufacturing of a large, extreme freeform, conformal window with robotic polishing

Our robotic polishing platforms are able to polish large, difficult-to-make optical surfaces with minimal surface error. 

Metrology of Freeform Optics

Proper metrology is required to monitor and verify the freeform fabrication processes to improve capability and precision

Freeform Monolithic Multi-Surface Telescope Manufacturing

The freeform monolithic multi-surface telescope design has all its off-axis optical surfaces manufactured from a single optical blank, resulting in truly monolithic telescope design, providing improvements in stability and payload. 

Fabrication of Freeforms

Optimax has developed a robust freeform optical fabrication CNC process that includes generation, high speed VIBE polishing, sub-aperture figure correction, surface smoothing and testing of freeform surfaces

Producing Smooth Surfaces on Polycrystalline ZnS Aspheres and Freeforms

The addition of VIBE smoothing as the final optical fabrication process yields highly smooth surfaces on polycrystalline aspheres, improving optical performance. 

Deterministic Form Correction of Extreme Freeform Optical Surfaces

Optimax has developed a variety of new deterministic freeform manufacturing processes by combining traditional optical fabrication techniques with cutting edge technological innovations

Optimax Freeform Capabilities
“Freeform Optics: Notes from the Revolution

Check out this months OPN article featuring experts in the area, including Optimax’s Jessica DeGroote Nelson

Freedom of Freeforms

Customers trust Optimax to create high-quality optics and deliver them fast, and our freeforms are no exception. Freeform optical shapes or optical surfaces are gaining popularity with lens designers and optical system integrators.

Presentation on Freeform optical manufacturing & testing processes

Kate Medicus, Ph.D., Metrologist speaks on Freeform optical manufacturing and testing processes for IR conformal window and domes. This talk will include an overview of current freeform manufacturing and testing processes for producing freeform surfaces

Optimax Freeforms

Optimax Freeforms

Optimax Capabilities

Optimax Capabilities

X