157/137 Series

OPTICAL THICKNESS GAUGE

OPTICAL THICKNESS GAUGE

p: (585) 924-2620 w: www.bristol-inst.com e: info@bristol-inst.com

Get the reliable accuracy you need for the most demanding non-contact thickness measurement applications. Conveniently measure thickness of up to 31 layers of transparent and semi-transparent materials.

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Precise thickness information is critical in the development and production of a variety of materials. Bristol Instruments offers the 157/137 Series Optical Thickness Gauge that conveniently measures thickness with the reliable accuracy and exceptional repeatability required for the most demanding applications. What’s more, these systems employ a proven technique that uses a non-contact optical probe to enable non-destructive testing. This optical technique also has the ability to measure the thickness of multiple layers simultaneously.

Key Features:

• Measures hard and soft materials without damage or deformation.• Up to 31 layers can be measured simultaneously.• Accuracy as high as ± 0.1 μm.• Long-term measurement repeatability as good as ± 0.02 μm.

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Industry Applications

The Optical Thickness Gauge products from Bristol Instruments will benefi t any engineer who needs to know the exact thickness of their material for development and production applications in industries such as these.

OPTICAL COMPONENTS AND LENS ASSEMBLIESMeasures individual components and multi-element stacks, including air gaps

CONTACT AND INTRAOCULAR LENSESMeasures center thickness, sagittal height and group index

LCD, LED, OLED AND AMOLED DISPLAYSMeasures total and individual layer thickness including LOCA (liquid optically clear adhesive) layers

MEDICAL TUBING AND CATHETERSSimultaneously measures wall thickness, inner and outer diameter, of tubing, as well as wall thickness of body, neck and cone for catheters

SEMICONDUCTORSSilicon/GaAs wafers

GLASS SLIMMINGMeasures thickness before and after the chemical etching and/or polishing process to make glass sheets thinner and lighter

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Thickness Measurement Using Light - The Bristol Advantage

The Optical Thickness Gauge (OTG) products from Bristol Instruments takes advantage of the unique properties of light to accurately measure thickness. To make a measurement, light is directed onto the material under test. Refl ections from every surface and layer interface are collected and then analyzed by an optical interferometer. The optical interferometer is a very precise “optical ruler” that measures the difference in length traveled by each refl ection to determine total thickness and the thickness of each layer.

A single-layer material will return two refl ections, one fromeach air/material interface. The difference in path length between the two refl ections is equal to two times the thickness of the material.

REFLECTIONS FROM A SINGLE-LAYER MATERIAL REFLECTIONS FROM A TWO-LAYER MATERIAL

Sample under test

Light from OTG

Sample under test

Light from OTG

A two-layer material will return three refl ections, one from each air/material interface and one from the internal material interface.

Because this optical technique is so effective, the Optical Thickness Gauge can collect and analyze the refl ections from a material with as many as 31 layers. The thickness of every layer and total thickness are measured simultaneously.

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157 measurement data of a gauge block that is certifi ed by NIST to have a thickness of 1269.9695 μm. The specifi ed accuracy of ± 0.1μm is given by the dashed lines. T

hick

ness

(µm

)

Time (Hours)

Maximum 1270.03 µm

Minimum 1269.91 µm

Average 1269.97 µm

Standard Deviation 0.014 µm

Accurate, Repeatable, and Reliable Thickness Measurement

The Optical Thickness Gauge products from Bristol Instruments offer the highest performance available to ensure the most meaningful test results.

HIGHEST MEASUREMENT ACCURACY

• Accuracy is defi ned as measurement uncertainty, or maximum thickness error.

• A coverage factor of three times the measurement standard deviation is used, resulting in a confi dence level of 99.7%. This means that virtually all of the measurements are expected to fall within the specifi ed accuracy limits.

EXCEPTIONAL LONG-TERM REPEATABILITY

• Repeatability is defi ned as the standard deviation of measurements taken over a 60-minute period without averaging.

• Repeatability also defi nes the ability to detect small changes in thickness when, for example, the system is used for online applications. Thickness changes as small as 0.04 μm (0.0016 mils) can be identifi ed.

CONTINUOUS CALIBRATION

• The specifi ed accuracy is guaranteed by comparing every measurement to a built-in intrinsic, invariant standard of length. This reference is a helium neon (HeNe) laser that emits light with a wavelength that is recognized by the US National Institute of Standards and Technology (NIST).

• The result is reliable accuracy, year after year, without the need for external calibration or any user intervention.

TRACEABLE TO NIST STANDARDS

• For added confi dence, each Optical Thickness Gauge system is rigorously tested with a set of three different NIST-certifi ed gauge blocks to verify its performance. A calibration certifi cate is included with every instrument.

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Straightforward Measurement Process

Operation of the Optical Thickness Gauge is straightforward, making it easy to get reliable measurement data every time.

Optical Thickness Gauge

Sample Under Test

ThicknessResults

Light (SLED)

Optical Probe

lens

lens

lens

lens

air gap

1 2 3 4 5

•

•

•

•• • •

•••

Measurement data from the multi-element lens assembly. The thickness of every component, including the air gap between lenses, is reported simultaneously.

(1) The OTG system includes a superluminescent LED (SLED), interferometer assembly, and digital signal processor (DSP) all housed within a rugged rack mountable chassis.

(2) Light from the SLED is sent to the material under test through an optical probe that is connected to the OTG system by a fl exible fi ber-optic patch cord.

(3) Refl ections from the material under test are collected by the optical probe and returned to the OTG system’s interferometer for analysis.

(4) Thickness data is calculated using the DSP and transferred to a PC using a USB or Ethernet interface.

(5) The Windows-based Opti-Cal software is used to control measurement parameters and report thickness data in a variety of formats.

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Diagram of glass tube

Wall Thickness

•

•

•

•Wall Thickness

Outer Diameter

Inner Diameter

•

•

•

•

Measurement data from a glass tube

The Data Table reports the thickness information of up to 31 different layers. This includes individual layer thickness, total thickness by layer, and measurement standard deviation. Units of millimeter (mm), micrometer (μm), and millionth of an inch (mils) can be chosen. Every measurement can be displayed, or a running average can be calculated automatically.

Convenient Operation with Opti-Cal Software

The primary user interface for the Optical Thickness Gauge products from Bristol Instruments is its Windows-based Opti-Cal software. This software displays the interferometer signal, controls measurement parameters, and reports thickness data.

The Refl ection Peaks Graph displays the signal that results from the refl ected light from all the surfaces of the material under test and all the interfaces within the material under test. The fi gure above shows the results of the measurement of a glass tube. The refl ections from the air/glass interfaces generate the peaks shown in the graph.The differences between the positions of the peaks provide information about the top wall, inner diameter, bottom wall, and outer diameter information about the top wall, inner diameter, bottom wall, and outer diameter.

Top Wall

Air Gap

Bottom Wall

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Measurement Modes with Opti-Cal Software

Automatic Peak Mode automatically selects refl ection peaks using the Threshold and Start Point functions. Threshold sets the minimum intensity level for a peak to be selected and Start Point sets the minimum position for a peak to be selected. Using the relative positions of all identifi ed peaks, the Opti-Cal software calculates and reports the thickness of as many as 31 layers in the Data Table.

Measurement data showing Automatic Peak Mode

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Measurement data showing User Defi ned Mode

Measurement Modes with Opti-Cal Software (continued)

User Defi ned Mode uses an operator-created material design fi le to defi ne the expected peak positions of up to 32 surface refl ections (31 layers). With this information, the Opti-Cal software identifi es the peaks that are closest, within a specifi ed margin, to the expected peak positions. These peak positions are used to calculate and report the thickness of each layer. In addition, deviations from the expected layer thickness, information that is useful for quality control applications, are also reported.

Opti-Cal software shows actual vs. design thickness and the delta

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Designed for Manufacturing Environments

The Optical Thickness Gauge products from Bristol Instruments are ideal for both the research scientist and the manufacturing engineer.

FLEXIBLE INTEGRATIONAll calculations that are needed to determine material thickness are done using an on-board DSP. Therefore, the measurement data can be reported in a variety of ways using either USB or Ethernet interfacing.

• Measurement data can be transferred to a PC and displayed using the Opti-Cal software program.

• The Ethernet interface can be used to connect to a local area network. Multi-user interfacing allows up to eight network-connected clients direct access to real-time measurement data.

• The Optical Thickness Gauge can be integrated into an application for automatic data reporting thereby eliminating the need for a dedicated PC. This can be done using LabVIEW, .NET, or custom programming.

OPTICAL SWITCH CAPABILITYThe Optical Thickness Gauge is available with a built-in optical switch to make it more cost-effective for manufacturing applications. The optical switch enables the use of up to eight optical probes the convenient testing of a material at multiple locations.

REMOTE OPERATIONThe Optical Thickness Gauge can be located remotely from the optical probe by a distance that is limited only by the length of the fi ber-optic patch cord used to connect the two. A fi ber-optic patch cord with a length of 30.5 m (100 feet) has been tested by Bristol Instruments. This capability benefi ts a variety of applications, but especially those in clean room and/or controlled environments.

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Optical Thickness Gauge Options

The Optical Thickness Gauge products from Bristol Instruments provide the most accurate, repeatable, and reliable thickness measurements available. Two versions are offered. The model 157 provides the highest performance for the most demanding applications. For measurement requirements that are less exacting, the model 137 is a lower priced alternative.

Two confi gurations are available for each of these systems. The standard version is used for most applications, and the LS version can accommodate thicker materials.

Model 157

FOR THE MOST DEMANDING APPLICATIONS

• Highest Accuracy of ± 0.1 μm• Exceptional repeatability of ± 20 nm• Measures thickness down to 12 μm• Optional LS measurement range up to 40 mm

Model 137

A LOWER PRICED ALTERNATIVE

• Accuracy of ± 1.0 μm• Repeatability of ± 50 nm• Measures thickness down to 35 μm• Optional LS measurement range up to 40 mm

COMMON FEATURES OF ALL MODELS• Measures hard and soft materials without damage or deformation• Visible tracer beam to pinpoint measurement location• Up to 31 layers measured simultaneously• Continuous calibration with built-in intrinsic standard of length• Measurement confi dence level of ≥ 99.7%• Traceable to NIST standards• Measurement rate as high as 20 Hz• Straightforward operation with PC using USB or Ethernet• Windows-based Opti-Cal software provided to control measurement parameters and to report measurement data• Automatic data reporting using LabVIEW, .NET, or custom programming eliminates the need for a dedicated PC

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Optical Probe Options

The optical probe used with the Optical Thickness Gauge directs light to, and collects refl ections from, the material under test. Bristol Instruments offers a variety of optical probes for different thickness measurement applications.

QAP QUICK ALIGN CAMERA PROBEFor R&D, quality control, and pre-production applications

Proper alignment of the optical probe is critical, but may be challenging for some applications. Therefore, Bristol Instruments provides an optical probe that includes a built-in visual aid that greatly simplifi es the alignment process.

The Quick Align Camera Probe uses an integrated camera to locate the optical signal refl ected from the material under test. The system’s Opti-Cal software displays the camera image to show the relative positions of the refl ected signal and the target. With this visual feedback, it is easy to make the appropriate adjustments to perfectly align the optical probe. In addition, the Quick Align Camera Probe has a wide acceptance angle that makes the alignment process much more forgiving.

LP “PENCIL” OPTICAL PROBEFor applications with space limitations

This optical probe has a smaller diameter (< 0.75”) for use in tight spaces. It also allows multiple probes to be placed very close to each other. Alignment is achieved and optimized using the signal displayed on the Refl ection Peaks Graph of the Opti-Cal software.

P OPTICAL PROBESFor integration into custom fi xtures used in production applications

These optical probes have the same performance as the Quick Align Camera Probes, but without the integrated camera. Alignment is achieved and optimized using the signal displayed on the Refl ection Peaks Graph of the Opti-Cal software.

(A) The refl ection signal (white dot) is not on target. The probe is misaligned.

A B

(B) The refl ection signal is on target. The system is ready to measure.

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Optical Probe Compatibility

The QAP Series, P Series, and LP Series Optical Probesare all compatible with the 157 and 137 Optical Thickness Gauge systems. Two versions of the QAP and P Optical Probes are offered for use with the standard and the LS confi gurationsof the optical thickness gauge. The difference between theseoptical probe designs is the available working distance betweenthe probe tip and the material under test. The smaller workingdistance allows for more compact fi xture design, and the largerworking distance can accommodate thicker materials.

OPTICAL PROBESP R O B E M O D E L QAP-025/50 P-025/50 QAP-011/75 P-011/75 LP-025/75

WO R K I N G D I STA N C E 44.2 mm 41.8 mm 69.4 mm 69.4 mm 69.5 mm

OTG SYST E M CO M PAT I B I L I T Y 157, 137 157, 137 157, 157LS, 137, 137LS 157, 157LS, 137, 137LS 157, 157LS, 137, 137LS

I N T E G RAT E D CA M E RA Yes No Yes No No

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SPECIFICATIONS 157/137 SeriesMODEL 157 157LS 137 137LS

THICKNESS MEASUREMENT

Method Non-contact optical interferometry

Maximum Physical Thickness(Layer of air with index of refraction of 1.0)

12 mm 40 mm 12 mm 40 mm

Maximum Physical Thickness(Material with index of refraction of 1.5)

8 mm 26 mm 8 mm 26 mm

Minimum Physical Thickness 1

(Material with index of refraction of 1.5)16 μm 20 μm

35 μm12 μm (± 1.0 μm accuracy) 12 μm (± 1.0 μm accuracy)

Accuracy 2 ± 0.1 μm ± 1.0 μm

Repeatability 3, 4 ± 0.02 μm ± 0.05 μm

Traceability Verifi ed with NIST certifi ed gauge blocks

Units mm, μm, mils

MEASUREMENT RATE 20 Hz 7 Hz 20 Hz 7 Hz

INSTRUMENT INTERFACE USB and Ethernet with Windows-based display programEthernet can be used for network connection allowing instrument access to up to 8 clients

Library of commands for LabVIEW, .NET, and custom programming

COMPUTER REQUIREMENTS 5 PC running Windows 7, 8, or 10, 1 GB available RAM, USB 2.0 (or later) port, monitor, pointing device

OPTICAL SWITCH 6

Capacity Integrated 1 x 8 fi ber switch

Switch Time 7 1 ms

ENVIRONMENTAL 8

Warm-Up Time None

Temperature 15°C to +30°C (-10°C to +70°C storage)

Pressure 500 – 900 mm Hg

Humidity ≤ 90% R.H. at + 40°C (no condensation)

DIMENSIONS AND WEIGHT

Dimensions (H x W x D) 3.5" x 17.0" x 15.0" (89 mm x 432 mm x 381 mm)

Weight 17 lbs ( 7.65 kg)

POWER REQUIREMENTS 90 - 264 VAC, 47 - 63 Hz, 80 VA max

WARRANTY 3 years (parts and labor)

(1) Models 157 and 157LS are capable of measuring down to 12 μm, but with lower accuracy. (2) Defi ned as measurement uncertainty, or maximum thickness error, with a confi dence level of ≥ 99.7%.(3) Standard deviation for a 60 minute measurement period.(4) Dependent on the refl ectivity of the material under test at the probe wavelength of 1.3 μm. Specifi cation is given at 4% refl ectivity.

When refl ectivity is lower, repeatability is reduced to a worst case of about ± 0.15 μm. (5) Required for initial optical probe alignment and use with the Windows-based display program. Not required for measurement.(6) Integrated fi ber optic switch included with models 157-8, 157LS-8 137-8, and 137LS-8.(7) Switch time has no effect on system's measurement rate.(8) Characteristic performance, but non-warranted.

Bristol Instruments reserves the right to change the specifi cations as may be required to permit improvements in the design of its products. Specifi cations are subject to change without notice.

REV 05-20