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Technical Data
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OptiSurf® Broshure

High Precision Non-Contact Measurement of Air Gaps and Center Thicknesses of Lenses and Optical Systems


High-precision measurement of center thicknesses and air gaps

OptiSurf® is ideal for the non-contact measurement of the center thicknesses of single lenses and plano optics as well as for the measurement of air gaps in optical systems. The low-coherence interferometer measures all surface distances in an optical system in just one scanning operation and with an accuracy of up to 0.15 µm. Its innovative alignment, adjustable sample tray and intuitive software ensure the exact positioning and measurement of lenses and optical systems in the easiest way possible. This makes OptiSurf® particularly suitable for use in production.

Product Overview


The standard for center thickness measurement


OptiSurf® is the standard for measuring center thickness and air gaps.

  • Measurement accuracy of up to 1 µm

  • Measurement head with automatic focusing

  • Integrated visual laser beam for preliminary alignment of the sample

OptiSurf® UP

For the highest demands


The OptiSurf® UP meets the highest requirements with its ultra-precise center thickness and air gap measurements.

  • Measurement accuracy of 0.15 µm

  • Measurement head with automatic focusing

  • With temperature and air pressure sensors

  • Integrated visual laser beam for preliminary alignment of the sample

OptiSurf® IR

Measurement of all IR materials

OptiSurf® IR

The unique measurement system OptiSurf® IR allows the measurement of center thicknesses and air distances of IR lenses.

  • Measurement accuracy of 5 µm

  • Measurement head with automatic focusing

  • Optional combination with OptiCentic® IR for full alignment control of IR lens systems

  • Integrated visual laser beam for preliminary alignment of the sample

OptiSurf® OEM

Individual fitted

OptiSurf® OEM

The OptiSurf® OEM can be integrated into external systems for customer-specific linking of center thickness and air gap measurements with further measurement parameters.

  • Single sensor with delay line for integration in non-TRIOPTICS measurement systems

  • Measurement head with automatic focusing

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OptiSurf® UltraPrecision


OptiSurf® Professional

Fast, comprehensive and user-friendly

OptiSurf® Professional software allows the quick and comprehensive measurement and analysis of center thicknesses and air gaps in optical systems. Both the signal curve as well as color markings in the lens system scheme permit conclusions to be drawn quickly with regard to the plausibility and completeness of the measurement. Performing multiple measurements with a statistical evaluation allows a highly reliable evaluation to be carried out.

  • Supports the intuitive handling, alignment and measurement process

  • Automated surface identification for quick and precise measurements

  • Automated evaluation and identification of deviations by means of a pass/fail analysis

  • Product-specific quality control through the statistical analysis of measurement results

  • Easy input of sample data directly via Zemax, OptiCentric® or via a design editor

Technical Data

ParameterOptiSurf®OptiSurf® Ultra PrecisionOptiSurf® IR 2)
Measurement accuracy1 µm 1)0.15 µm 1)Micrometer range 3)
Repeatability0.5 µm<0.075 µmMicrometer range 3)
Wavelength of the light source1.3 µm 1.3 µm 2.2 µm
Scanning rangeUp to 800 mm optical distance, larger on requestUp to 800 mm optical distance, larger on requestUp to 400 mm optical distance, larger on request3)
Sensors for temperature and air pressureOptionIncludedOption
Computer interfaceUSBUSBUSB
Camera-based alignment toolOptionYesNo
Laser class111
Dimensions (h x w x d)965 mm … 1,240 mm x 370 mm x 560 mm965 mm … 1,240 mm x 370 mm x 560 mm965 mm … 1,240 mm x 370 mm x 560 mm
Weight50 kg50 kg50 kg
TypeTable top deviceTable top deviceTable top device

1) According to 2σ criterion for measuring 100 mm air gap between optical flats
2) Available in combination with OptiCentric only
3) Depends on sample

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Upgrades & Accessories

For fast and validated testing, TRIOPTICS offers the following accessories

Optical alignment tool for the quick and easy alignment of the sample and the measurement head integrated in the instrument base

Certified 0.5“ reference sample, traceable to international standards

Knowledge Base

Low-coherence interferometers

Measurement of lens air gaps, center thicknesses of lenses, objectives and all other transparent materials

Low-coherence interferometers are used in optics to measure the center thickness and air gaps of lenses against each other, in other words the positions of optical surfaces along the optical axis can be determined. As such, low-coherence interferometry is an ideal complement to centration measurement (link to centration measurement), in which the positions of the centers of curvature are determined in the x/y direction. By combining both methods, it is possible to determine the absolute position of each surface in a mounted objective lens. TRIOPTICS products for this application: OptiCentric® 3D, OptiCentric® 3D Dual.

At the same time, centration measurement is also a prerequisite for the highly accurate measurement of center thickness and air gaps, since they can be used to determine

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Center thickness testing in production:
OptiSurf® LMT

Combined centration and center
thickness measurement: OptiCentric® 3D

Measuring principle of low-coherence interferometers

The design of a low-coherence interferometer, as implemented by TRIOPTICS in the OptiSurf®system is described in Fig. 1. The light from a low-coherence light source is divided by a beam splitter into an object beam and a reference beam.

The object beam illuminates the lens system along its optical axis. A fraction of the incoming light beam is reflected back at each surface of the sample. This light is superimposed on a photo detector with the light from the reference arm. The light in the reference arm is varied by means of a delay section in the time span.

The length of the reference arm is varied by means of a movable mirror, and measured using an laser interferometer. When the resulting intensity of the back-reflected reference beam and object beam are analyzed as a function of the change in length/delay of the reference arm (Fig. right) then interference patterns are always observed when the optical path lengths coincide in the two interferometer arms. Thus, the position of each surface of the sample can be determined mathematically.

OptiSurf® Knowledge Base

Operating principle of a low-coherent interferometer