High-precision non-contact thickness measurements

Novacam metrology systems deliver fast and reliable non-contact thickness measurements of transparent and semi-transparent materials.

  • Precision better than 1 µm
  • Thickness measurements of thin films, single-layer films, or multi-layer films
  • Films and film stacks: from 10 µm to several mm thick.  Thickness measurements are acquired simultaneously for substrates and for entire film stack.
  • High-speed scanning: acquisition of 2,100 to 100,000 points (profiles) per second
  • Data acquired for automated reporting or visualization: depth profiles, 2D cross-sections (B-scans)  and 3D volumetric images (C-scans)

Materials measured may be reflective or nonreflective, smooth or rough, stationary or moving. Index of refraction (IR) can also be calculated if needed. Surface or sub-surface roughness, shape or topography may be acquired at the same time as thickness. See more on what we can measure.

Profile thickness of photoresist film coating

2D cross-section of an unevenly applied thick film of photoresist coating on a 6” diameter semiconductor wafer

Intra-ocular lens on mold - 2D cross-section

Intra-ocular lens: 2D cross-section extracted from acquired 3D image

Advantages of measuring with fiber-based probes

Novacam metrology systems combine low-coherence interferometry (LCI) technology with fiber-based modular design, meaning that:

  • Measurements are done with fiber-based non-contact optical probes
  • The data acquired is sent over an optical fiber, up to a km long, to the signal-processing detector box (interferometer).

Advantages of Novacam’s design include:

  • Configuration versatility for both benchtop and in-process inspection
  • Support for automation
  • Ability to acquire long profiles 
  • Ability to measure roughness inside small-diameter tubes, bores, etc.  See inspection in hard-to-reach spaces.
  • Ability to measure thickness even in extreme temperatures or in radiation.  See inspection in hostile environments.

See a more complete list of advantages of our fiber-based LCI systems.

Novacam fiber-based optical probes come in many designs and models – standard, small-diameter, rotational, or galvo-scanner – to satisfy the majority of high-precision inspection applications.

Multi-layer thickness measurement of high-grade tubing

High-grade polymer tubing must be closely monitored during extrusion so that dimensions continuously adhere to tight specifications.

To monitor the quality of extruded medical catheter tubing (diameter < 1.5 mm), a non-contact optical probe was installed at the extruder exit (see diagram). With this set-up, cross-section dimensions are acquired continuously and an efficient production control loop is established:

  • The probe acquires the thickness of the advancing thin tubing as a long profile – at up to 100,000 points (A-scans) per second
  • Each A-scan delivers optical thickness of the upper wall, the enclosed air space, and the lower wall
  • Application software transforms optical data into physical dimensions of the tubing.  The table below the diagram shows the tubing dimensions as well as the index of refraction (IR) calculated from a single A-scan
  • Cross-section dimensional data is streamed to process-control software which adjusts extruder parameters in real time.

Real-time continuous inspection cuts down on extruder down-time, reduces material waste, and lowers overall production costs.

Single-probe setup for continuous measurement of catheter tubing

Tube dimensions and IRValue
thickness of upper wall0.131 mm
thickness of lower wall0.162 mm
inner diameter0.852 mm
outer diameter1.145 mm
calculated index of refractionIR = 1.512

Probe multiplexing for additional ROI

Several fiber-based probes can be multiplexed to a single detector (low-coherence interferometer) for simultaneous thickness measurements on different aspects of a production line.

For example, the tube inspection setup above can be extended by adding a second probe at the extruder exit (diagram on the right). In this way, the operator is able to monitor tube dimensions along two axes continuously, achieving even greater quality control with minimal extra investment.

Multiplexing two probes to one interferometer has also been used in the example below.

Two-probe setup for continuous profiling of catheter tubing

Continuous measurement of optical fiber and its coatings

Novacam’s system has been used in the production of optical fibers for several years.

In this particular setup (photos on the right), two scanning optical probes (multiplexed to a single interferometer) are positioned at right angles to each other and to the continuously moving optical fiber. The fiber has two layers of semi-transparent coating whose thickness must remain uniform.

The video below shows the user’s display of real time measurements, which are forwarded to the application software and logged, as per user requirements.  As part of production quality control, the cross-section data (shown as red for fiber, blue and green for the two coating layers) is programmatically compared to user-specified criteria.

thickness measuring

2-probe setup for continuous monitoring of optical fiber with 2 coating layers

Close-up of probes scanning the fiber

Thickness measurement applications across industries

Novacam’s metrology systems acquire thicknesses in a range of domains:

  • Opthalmology: inspection of regular or intraocular contact lenses
  • Semi-conductors: coating on MEMS devices, semiconductors, hybrid circuits, fuel and solar cells
  • Aviation and automotive: protective films
  • Optical: etching and deposition thickness on waveguides
  • Electronics: thick film photoresist coating on electronic wafers
  • Bio-medical: coatings which protect devices from corrosion or patients from complications
  • Others: conformal coating, protective tool coating, vacuum coating

Related links

 Contact us or request free sample analysis to see if low-coherence interferometers are suitable for your application