Frequently Asked Questions


The OptiGauge is a non-contact, non-destructive, all fiber, thickness measurement interferometer. Protected by over 20 patents and copyrights the system is designed to:

  • Upgrade existing measurement processes
  • Improve productivity
  • Speed up R&D innovation
  • Decrease scrap and associated costs
  • Improve quality
  • Decrease operator measurement variability
  • Meet compliance standards

Lumetrics provides superior service and support for standard and custom solutions.

Refractive Index, or more specifically the Group Refractive Index (GRI), is a measure of the optical density of the material. The denser the material optically (higher GRI), the slower is the speed of the light propagating inside that material. The OptiGauge measures the optical thickness, which is equal to the product of the physical thickness times the GRI. The physical thickness is then obtained through a simple table look up. Most plastic and glass materials have a GRI of approximately 1.4 to 1.6. The OptiGauge software uses a default GRI of 1.5.

Lumetrics can also be used to determine material GRI, using a special fixture called Refractive Index Calculation System (RICS). This simple hardware and software package is inexpensive and easy to use.

The OptiGauge, controller, monitor, and switch all take standard 120VAC – 240VAC. This is controlled automatically through the power input module

Yes: Although the OptiGauge MLS and EMS are sold with a controller, customers are allowed to purchase an OptiGauge II system without the controller if their existing computer meets certain minimum standards. In the OptiGauge II, the customer is provided with the OCC software to load on their computer.

Yes: Customers can load antivirus software on their controller as long as that software does not interfere with OCC functionality. Please consult with Lumetrics software engineering before performing this task.

The light emitted from the OptiGauge is super-luminescent LED light centered at 1310 nm. It is classified as Class I laser source, which pose no danger to human eye. Nevertheless, it is a good safety practice to never stare at the light source (probe output window) directly.

  • Clear and translucent materials
  • Some opaque materials
  • Glass and plastic materials are ideal
  • Dry or wet
  • Profile of opaque and translucent materials

Contact us by phone or email to discuss your material and whether Lumetrics’ systems can measure it.

  • Tubing- Wall Thickness, ID, OD, Concentricity, Ovality
  • Contact Lenses- Center Thickness, SAG
  • IOL’s- optic zone thickness, haptic thickness
  • Films- overall thickness and individual layer thickness

No: As long as some light can penetrate the material, then a measurement can be made. We’ve measured glue on plywood, oil on a drum, food packaging, silicon wafers, and numerous medical devices, coatings, and glass.

Not sure if we can measure it? Give us a call and find out.

No: The OptiGauge does not need to know how many layers there are to measure. It looks for an index of refraction change between layers and displays those as peaks on the screen. The software then measures the distances between these peaks to determine thickness measurements. Custom software is easily written using our OCC Software Tool Kit to provide operator friendly user interfaces.

This is a question that depends on the situation, but adjacent layers typically need a refractive index difference of 0.01. Variables such as the specific materials, environmental conditions, extrusion variables and much more can have an impact on this value. Please contact Lumetrics to discuss your specific situation.

Yes: The OptiGauge can measure a surface profile through the use of an internal reference surface. A surface profile can be done at the same time the OptiGauge is measuring the thickness of a sample.

Yes: The OptiGauge can measure wet materials. The OptiGauge can measure both wet and dry materials. Additionally, the OptiGauge can measure solid objects, such as lenses, in a solution.

The OptiGauge displays real-time information both in graphical and numerical forms. An easy to interpret waveform provides user feedback for signal strength. This information can also be saved to an Excel-readable format, streamed out an RS-232 or Ethernet port.

  • The OptiGauge II measures from 12 microns to 16 mm based on material Refractive Index
  • The OptiGauge LT measures from 12 microns to 5 mm based on material Refractive Index
  • The OptiGauge MLS measures from 12 microns to 16 mm based on material Refractive Index
  • The OptiGauge EMS measures from 12 microns to 50 mm based on material Refractive Index

Maybe: The thinnest individual layer the OptiGauge can measure is 12 microns (at an index of refraction of 1.5). The OptiGauge can measure a difference in thickness smaller than 12 microns. For example if the OptiGauge measured a part at 200 microns thick and you applied a 5 micron coating to the part, the OptiGauge could measure 205 microns and then calculate the coating thickness.

Talk to Lumetrics if you have a questions on measurement capabilities.

1 – 20: OptiGauge software is setup to measure up to 20 layers. Need more than that? Let us know and we can adapt the software to suit your needs.

The OptiGauge has an accuracy of 0.1 microns.

The OptiGauge is calibrated using a NIST traceable standard. See paper on NIST traceability.

As part of its basic design the OptiGauge is being continuously calibrated with a 1550 nm laser that is temperature and current regulated. Additionally, Lumetrics provides a verification standard that can be used at any time to verify that the OptiGauge is still measuring within its correct parameters.

The standard OptiGauge makes 50 measurements per second. A standard system can be made to run at up to 200 measurements per second but the rate of measurement impacts the thickness of the material that can be measured. For example, a 200 measurement system can only measure a material with 5mm optical thickness (approximately 3.3 mm thick.)


Lumetrics has 4 standard probes but can custom design other probes with our in-house optical expertise. Our four standard probes have standoff distances that range from approximately 20mm to 90mm. The spot size and depth of focus are functions of the optical designs. Please contact Lumetrics for specifications for Lumetrics’ standard probes and custom probe designs. Please see probe specifications – http://www.lumetrics.com/capabilities-products/accessories/

Yes: The OptiGauge can be connected to up to eight probes through the use of an optional optical switch.

Switch time from one probe to the next is approximately 100 milliseconds. This includes the signal settling time.