Spectral Sensors by Carl Zeiss

Coating Thickness Measurement SystemINTRODUCTION
Designed to meet the needs of industry, theLABCOAT system provides a simple and precise
way to measure transparent coatings and films.
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Transparent coating and film thickness
measurement
Non-contact / Non-destructive
Fast, Accurate and Precise
Easy to use

The system is based on white light interference
effects caused by reflection from the top and bottom
surfaces of the coating. This results in constructive
and destructive interference at various locations inthe spectrum. Analysis of this spectral pattern,along with the material’s refractive index, allows thecalculation of the coating thickness.
An innovative Solid-State Diode Array spectrometeris at the heart of the system. Based on an award
winning design, this unit provides stability, speed
and precision without maintenance.
A flexible fiber-optic probe allows remote hand-heldoperation . The measurement area size can beselected to meet a variety of applications. Industrial
use of protective coatings,dielectric films, etc. is
growing rapidly. Control of thickness is a key togood coating performance. The LABCOAT
system can provide this valuable thickness
information for both R&D and Quality
Control in application areas such as
Automotive, Plastics, Paint, Chemical,
Packaging and Microelectronics.

MCS 551 UV Spectrometer

Dicon Multiplexer
Figure 1: White light interference

Vankel 7000 with Auto Temp

Hellma Ultra-Mini Probes

Figure 2: LABCOAT System

Application Note 12 / 00

Spectral Sensors by Carl Zeiss

THE SYSTEM
Measurement:
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Technique: white light interference
Measuring in transmission or reflection
Measurement area size: 2 mm typ.
Thickness range: 0.3 to 80 micron
Repeatability: 0.5% typ.
Measurement time: < 1 secondFiber probe: distance up to 25 meters possible

Spectrometer: MCS 500 series
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Type: Solid-State Diode Array
Grating: Concave holographic (no moving parts)
Wavelength: (220) 380 to 1000 nm
Resolution: 0.8 nm / diodeIntegration time: 0.01 to 1seconds

Minimum computer requirements:
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Processor: Pentium
Memory: 16 Megabyte RAM
Adapter slot: PCI or PCMCIASystem software:nn

Zeiss LABCOAT software program
Windows 9x, Windows NT

On-line Process:n

Dedicated systems can be customized for on-line
process control.

THE SOFTWAREnnnnnnn“Labcoat” software provides simple yet powerfulevaluation of the spectral interference pattern forhigh performance thickness measurement.
Selectable coating type.
Selectable thickness range.
Single key stroke measurement.
Display of measurement confidence.
Statistical analysis.
Data compatibility.

Carl Zeiss
Spektralsensorik

D-07740 Jena
Phone:++49 (03641)64 2838
Fax:++49 (03641)64 2485
E-Mail:info.spektralsensorik@zeiss.de
Internet:
http:// www.zeiss.de/spectral

Spectral Sensors by Carl Zeiss

Layer thickness measurement of anodized coatings on
aluminium plates and tapes

Lab and on-line measurementsINTRODUCTION
The coating of aluminium with aluminum oxide
or other protective or design coatings must be kept
in controlled quality limits during the coating
technology,in order to guarantee the functionality of thelayers and thus to comply with the customers’
requirements.
The testing of samples from the on going production
process can be performed as random sampling or online measurement.The coating parameters of thecoating plant can therefore be reset very quickly and,as a result, at low cost (quality and material
consumption).However, this measuring procedure is
only suitable for transparent layers, not for diffusely
scattering layers.

Fig.1

THE METHOD
Coated tapes or plates are measured using reflected
light.Interferences (white light) are generated from thereflection signals. The optical layer thickness isreliably evaluated by means of FFT algorithms. (Fig.1)
The geometric layer thickness is determined on thebasis of the mathematical relationship between the
optical and the geometric thickness, and the refractive
index function n=f (wavelength).
Results are provided with utmost reproducibility andabsolute accuracy which is due to the superb opticaland thermal stability of the ZEISS diode array
polychromators.
Thin layers between <500nm and a few nm can bemeasured, calibrated and integrated in automatic
processes by means of special evaluation algorithms.
These methods are generally applicable to all othercoatings which are physically suited for being
measured with our systems.

Application Note 4 / 9 9Fig.2 CORONA in use

Spectral Sensors by Carl Zeiss

THE SYSTEMS
There is the possibility to use fibre coupled (MCS 500) or fibreless systems (CORONA Fig.2).The diode array
spectrometer systems are based on the time-tried ZEISS MCS polychromator technology. The multi-channel
spectrometers provide spectral information with a resolution of 0.8nm/pixel and 3.3nm/pixel, respectively.
An RS422 interface, 4-20mA, and shortly an RS232/alternatively RS485, or a trigger input and output can be used asinterfaces, for example.
PCs are used for controlling the systems. The spectrometers can be cascaded, e.g. so that the visual spectral range
and the NIR spectral range are measured simultaneously. This permits the measurement of different multi layer
systems.

THE SOFTWARE
A possible software option is our ASPECTPLUS Windows standard software (supported by Windows 3.11/ 95/ 98 andWindows NT) in conjunction with the software module Layer Thickness.
For special, customized applications we recommend a solution under LabVIEW.
DLLs for C++ and LabVIEW drivers allow the user to program his own software interfaces, or to
integrate our measuring systems in overall procedures

THE BENEFITS
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Fast high-precision measurement
Excellent reproducibility of layer thickness data
Time-tried measuring systems and techniques
High reliability and low maintenance requirements, as no moving parts are useEasy software operation
Detailed spectral information provided at high speed
Flexible installation due to fibre-coupled or fibreless technology
and a wide range of accessories
Measurement of several measuring points by combination with opticalmultiplexer or traversing unit
Fibreless systems directly driven over traversing unit

SPECIFICATION
Wavelength range
Wavelength resolution
Wavelength reproducibility
PC interface
Distance between PC andsystem
Optical fibres
Housing

Carl Zeiss
Spectral Sensors

200 – 1020 nm (900 – 1700 nm optional, or cascaded)
0.8nm/Diode (2.4 nm Raleigh) / 3.3nm/diode (10nm Raleigh)<0,05 nm
RS 422; RS 232 res. RS 485 for CORONA
up to 80 m with standard cable
up to 2.5 km with light guide transmission
quartz, 600 µm core, SMA connections
19" housing or 19" rack mount
19" protective housing
Corona (fibreless) in cast housing

D-07740 Jena
Telefon:(03641)64 2838
Telefax:(03641)64 2485
E-Mail:info.spektralsensorik@zeiss.de
Internet:
http:// www.zeiss.deApplications Information
MCS 500
Thickness measurement
Headlight coating

Process description
On most automobile models,the protective
window of headlights is made of plastic.Toprotect the surface against scratches andyellowing by UV light,it is coated externally inthe production process with a protective coating.
The coating is applied by spraying. Subsequently
it is dried and cured by IR and UV irradiation.To
keep the reject rate low,it is important to checkthe thickness of the coating in the production
process.If the coating is too thick,there is therisk of peeling and cracking. If the coating is too.thin, it will not provide sufficient protection.The
entire process can be fully automated.

The coating thickness measuring system
automatically detects the arrival of a sample on
the conveyor belt.
The system measures the coating thickness andtransfers the results to a process computer forevaluation.It is possible to select rejects andrecord the trend of the batch.In general,there
are two decisive reasons for the in-line use of themeasuring system:a) Optimisation and inspection of coating
parameters,such as spraying density,curing
time and UV illuminanceb) Quality certification to ISO 9000 standards forautomobile subsuppliers

System description
Coating thickness measurement is based on theprinciple of white light interference.
A halogen lamp (CLH 500) illuminates the sample
through optical fibres and subsequently arranged
optical elements.The light reflections from top
and bottom side of the protective coatinginterfere with each other.
The interference spectrum is detected by a fast
diode array spectrometer (MCS 551 VIS) andevaluated.

The spectra are transmitted to the PC through a
serial interface (RS 422). The PC calculates thecoating thickness (FFT).Additionally,status data istransmitted informing of plausibility and current
system parameters.
An open-end terminal program (LabView)
provides easy integration of the system in existingprocesses.
Spezifikation

Specifications
Spectral range
Measuring range
Measuringaccuracy
Measuring time/data point
Size of measuring spot

600 ... 1,000 nm
2 ... 100 µm
20 nm< 300 msapprox. 3 mmmeasuring headdiffusing plates

Software
Manual measurement programThis program module serves for manual
thickness measurement using the handheld measuring head (reflection). Integration time and averaging are selectable. Theprogram measures dark current, reference
and sample individually. The interference
curve is displayed. As result ofmeasurement, the thickness appears alongwith information whether the result is in or
outside the tolerance range.

Flat plate measurement
This program module measures one
thickness per diffusing screen (reflectionmeasurement). The measurement isreleased through a switching contact on
the measuring head. Thickness,inrange status and measurement standby
state are displayed and output through aport.

Diffusing screen measurement
Two transmission measuring heads measure
the flat plates at three points (triggered bylight barriers). The thickness and the yellow
index of the sample are determined. Inrange or outof-range status is displayed and output via
a port both for individual samples as well as
for the batch.

Carl Zeiss
OEM - Spektralsensorik
D-07740 Jena
Phone +49 36 41/ 64 28 38
Fax+49 36 41/ 64 24 85
e-mail: mack@zeiss.de