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Optical Metrology

Optical Metrology Services

Using AMS optical metrology and interferometry services, your samples will be measured accurately by an expert optical metrologist with over 25 years of experience. We serve both the manufacturers and the end users of the parts we test.

Quality Control For Buyers and End Users

At AMS, we never compromise on quality. Our state of the art optical metrology enables buyers and end users to audit current suppliers and confirm their parts are still meeting your specifications. If we identify a quality issue, AMS can certify perform an on-site assessment of the supplier’s optical metrology equipment and procedures, and deliver expert training to ensure accurate QC for future deliveries. Alternatively, AMS can measure samples from potential suppliers, enabling you to select one that meets both your quality standards and budget requirements.

Reference Certification for Optical Manufacturers

For manufacturers, AMS measurements are a key component in system certification and process development. AMS optical metrology services quantify the effects of process adjustments during the optimization phase and for the first several production runs. Our clients in manufacturing can perform rapid prototyping and fine-tuning using AMS metrology, often reaching their targets after just a few iterations of process adjustment.

Connect with AMS to discuss your application and design a test plan to provide the data you need.

Surface and Wavefront Testing – Large Aperture Interferometry

All measurements produce a map of the deviation of the surface or wavefront from its ideal shape. These maps are used to calculate hundreds of quantities, the most widely used being PV, RMS, PVr, power and irregularity from Surface/Wavefront Form error maps. If your desired specification isn’t already a standard software result, AMS will script its calculation for your tests.

Surface/Wavefront tests are performed on Fizeau interferometers, using 1Kx1K imaging over apertures from 5mm for smaller parts to 12” for larger parts. Contact AMS if you have a sample that is larger than 12”, as we have test setups designed to accommodate larger samples.

  • Surface Flatness
    • Polished and fine ground flat (plano) surfaces
  • Surface Form Error
    • Spheres and Cylinders
      • Radius of Curvature
    • Conics (Parabolas, Hyperbolas, Ellipsoids)
  • Transmitted Wavefront Error (TWE, TWD)
    • Windows, Lenses
    • Optical Assemblies
    • Beamsplitters, Prisms
    • Computer Generated Holograms (CGHs)
    • Diffraction Gratings
    • Corner Cubes
  • Wedge, Beam Deviation
    • Windows, Corner Cubes
  • Reflected Wavefront Error (RWE, RWD)
    • Flat
    • Spherical
    • Cylindrical
    • Conic
  • Thickness Variation
    • Parallel samples
      • Rigid or pliable
  • Homogeneity (PHOM)
    • Windows, Blocks
      • Parallel or wedged
  • Angular Errors
    • Prisms, Corner Cubes
    • Polygon Mirrors

Roughness Testing – Microscopic Interferometry

AMS uses Scanning White Light interferometry (SWLI) to test samples for roughness, waviness, and other small-scale quantities. Map data are used to calculate a wide variety of quantities, the most widely requested being Ra, Rz, and RMS. Both rigid and slightly pliable materials can be tested. With low magnification objectives, form errors of small or unpolished samples that cannot be measured on the large aperture interferometer can be measured here.

  • Surface Roughness and Texture
  • Surface Form
    • Smaller samples
    • Non-specular samples
  • Form/Waviness/Roughness Analysis
  • Surface Angles and Geometry
  • Thickness Variation

Optical Certification Services – Absolute Testing

The standard interferometer measurement is a comparison of the test surface to a reference surface, usually a Transmission Flat (TF) or Transmission Sphere (TS). The resulting map of the test surface includes the errors of this reference surface, often the largest source of error in the measurement of a high quality optic. AMS optical certification and calibration services use absolute testing to provide a map of the reference surface. AMS absolute testing procedures meet the traceability standards of ISO 17025 for flat and spherical surfaces over their full area. When performed at regular intervals, these certifications ensure compliance with the ISO 9001 requirement for reference standard certification.

AMS can certify plano and spherical surfaces over their full area, with maps accurate to 1/300th wave (2nm) or better. A certificate of calibration is provided with every sample. A fully traceable error analysis is available upon request. Pieces frequently requested for certification include:

  • Transmission flats and transmission spheres, which mount on the interferometer and are used as the ‘perfect’ surface to compare to the test surface or wavefront
  • Reference flats and reference spheres, usually used to return a test beam after transmitting through a test part for transmitted wavefront testing
  • Any plano or spherical optic that is used as a calibration check or standard

Knowing the magnitude and shape of the reference standard allows the metrologist to improve the accuracy of the test by removing this error. This provides a wider margin to meet specification and manufacture high performance parts.

Material Homogeneity Testing

Homogeneity is the spatial variation of the refractive index of the glass used to make an optic. If the material homogeneity is not adequate, an optic made with perfect surfaces would fail the final transmitted wavefront test. Use AMS homogeneity testing before cutting the blanks to avoid unexpected outcomes, reducing risk and saving production time.

  • (Plano) Windows and Blocks
    • Parallel and wedged

Reflectance and Transmittance Testing

AMS spectral testing measures how an optic interacts with light over the ultraviolet, visible, and near-infrared range of wavelengths. We can provide transmittance, reflectance, and absorbance curves to ensure your materials and coatings are performing as expected.

AMS uses ZYGO interferometers, including Read More a VeriFireTMMST and DynafizTM for surface form and transmitted / reflected wavefront error, a VeriFireTM with Distance Measuring Interferometry (DMI) for spherical and cylindrical radius of curvature, and a NewViewTM Scanning White Light Interferometer (SWLI) for surface roughness. Measurements are performed in environmentally controlled conditions, and the DynaFizTM is located in a clean room environment specially designed for reference certifications and calibrations.