The LASERSURF is a non-contacting optical probe providing a simple,
inexpensive method of measuring surface profiles, distance, irregularities or
texture of any material at the sub-micron level. Applications are found in
Tribology, semi-conductor physics and electronics, to name only a few.

Operating in conjunction with existing instrument or translation system

or by integrating into original manufacturers instruments and systems.

Surface profile measurement and surface texture analysis

Sub-micron surface analysis and micro structure measurement

Surface measurement of semi-conductors

Profile measurement of soft surfaces

Profile measurement of hard and very hard abrasive surface

Reflectance or gloss measurement

Overview

Surface texture clearly affects performance and life of components sliding
relative to each other, and surface defects are a critical factor in the life of
stressed elements or semiconductors. Cosmetic appearance also plays a
significant role in perceived quality.

A change in surface texture can provide an early warning of a change in the
manufacturing process and similarly, unless the method of manufacture is
controlled, satisfactory function and appearance of a part cannot be assured.

New materials, automated manufacturing techniques, the drive for quality
improvement and higher precision to extend operating life, all lead to an
increasing requirement to quantify surface finish.

The application of surface metrology is essential, to optimise both the
functional performance and cosmetic appearance of manufactured components and as
part of the overall control of the manufacturing process.

THE SYSTEM

A complete LASERSURF system comprises a miniature optical probe interfaced to
a compact separate control unit. The probe can be used in any orientation and
can be supplied with a number of mechanical interfaces to ensure complete
compatibility with existing translation stages or mounts. At the rear of the
probe is a standard metric thread for easy mounting.

The control unit is connected to the optical probe by way of a flexible
electrical cable, providing the appropriate voltages to the probe and processing
the measured signal. The unit has a digital liquid crystal display indicating
values measured. In addition there are controls for setting the appropriate
ranges from 20 to 500 microns and a filter setting that ensures optimum measure
characteristics. This unit also incorporates push button selection for
"standby", as well as "zero". The zero control is used for accurately setting
the probe at the correct working height. To ensure further ease of use a
separate display is provided to indicate deviation from the optimum working
distance so ensuring the probe is always within range.

An analogue surface profile signal is output for direct feed to a
computer AD converter; typically +5V max on each range setting. Alternatively,
the optional interface allows the profile signal to be fed through the existing
stylus system.

OPERATING PRINCIPLE

The LASERSURF optical probe incorporates a miniature laser diode and a
focussing lens coupled to a position controller. Deviations of the focal point
are measured by the controller and after further processing are made to relate
to a signal that is proportional to the distance from the probe to the object.
To ensure adequate light is reflected from the surface, the controller
automatically ad justs the light output from the probe. This signal can also be
used to provide a measurement of "REFLECTIVITY" or "GLOSS". A feature of the
LASERSURF system is that in addition to measuring surface profile, it can also
operate as a "REFLECTOMETER" or "GLOSSMETER", allowing measurements to be made
on surface finishes, paint, colour etc.

OPTICAL PROBES VERSUS "STYLUS PROBES"

The advantages of the optical probe can be seen in most types of sample,
whether they are metal surfaces, soft surfaces, semiconductors or gels. The
optical probe is simple, accurate, does not scratch or damage, there are no
replacement diamonds to purchase and it provides a known and constant footprint
on the sample of 1.5 microns. In addition, step functions cannot cause damage.
Compare there advantages with the stylus type of probe where a stylus is
extremely fragile, it always damages the sample and is practically useless on
soft surfaces. In general stylus probes are acceptable only when the sample can
be discarded or when scratches are alright.

LASERSURF COMPATIBILITY WITH CUSTOMERS EXISTING SYSTEM

LASERSURF measurement systems have been specifically designed to operate with
existing stylus instruments and provide a compatible output. To upgrade an
existing stylus type instrument, simply remove the mechanical probe and replace
it with LASERSURF.

For systems that incorporate "in range" proximity control, interfacing with
LASERSURF is again simple in that the LASERSURF controller detects the position
of the optical probe above the surface and provides both a control signal and an
audible output.

EASY USE

Parameters for traversing the surface to be measured relative to the probe
are set up as usual. A low pass selectable filter control on the front panel is
also provided and set at 25 Hz for example.

The operator then selects a range or sensitivity setting after which the
probe is switched on. The probe is lowered towards the sample until the front
panel optical bar-graph indicates an in-range condition after which an audible
alarm will sound. The instrument is now ready to use.

OPERATING RANGES

The overall working distance is 1 mm. On the highest range, non-linearity is
typically +/- 4% providing a degree of accuracy that is excellent for many
applications. Should a higher degree of accuracy be required, simply limit the
measurement range to 20 or 100 microns. On these ranges the LASERSURF will
provide an overall non-linearity of +/- 2%, which is considerably better than
many surface profile instruments.

SUMMARY

The LASERSURF non-contacting optical probe provides a simple, inexpensive
method of measuring surface profiles, distance, irregularities or texture of any
material at the sub-micron level. The instrument will not damage, deform or
scratch the sample to be measured and will provide unique additional information
regarding surface texture, gloss or optical reflectivity. The LASERSURF will
operate to specification on most existing "stylus" instruments either from new
or as an upgrade to instruments already in use. The LASERSURF can be
incorporated into practically any type of surface measurement system either for
measuring linear surface irregularities, 3D profiles or topographs.

3D PROFILE MEASUREMENT

In order to display the micro 3D contour of a surface in pseudo 3D, it is
simply necessary to traverse an object about 2 axes.

APPLICATIONS

Evaluation of surface finish, displacement and form in

Precision metal finishing

Soft high quality surfaces

Thin or fragile films, sheets and tapes

Optical products: mirrors, flexible and rigid lenses

Electronics: semi-conductors, surface mount technology

Paper, Rubber, and Plastics manufacture

Pharmaceuticals: tablets, capsules

Geological testing: rock porosity

Paint finish and other surface coatings

Medical engineering

ADVANTAGES OF OPTICAL PROBES

THE FOLLOWING LISTS JUST A FEW...

Excellent sensitivity

Measure spot size of 1.5 microns

Surface is never degraded

Mechanically robust

Can be used with practically any surface

Excellent for semiconductors and optical surfaces

High intrinsic accuracy

TYPICAL MATERIALS FOR SURFACE ANALYSIS

SEMICONDUCTORS

Discrete device inspection, Fine form, Step functions, Dimensioning, Film
surfaces, Etching.

ELECTRONICS

PC Board production control, Device layout, Coating thickness, Edge form.

PREPARED SURFACES

Paint thickness, Reflectivity, Gloss, Texture, Colour, Sheen, Inclusions,
Contamination, Start and stop positions.

OPTICAL

Lens and mirror contour, Substrates, Film step functions, Crater form, Grid
structure, Drop outs, Wafer inspection, Laser trim sections, Micro-topography,
Diamond turned parts.

METALLURGY

Q.A. surface preparation, Wear form, Grind quality, Surface finish,
Straightness, Roundness, Curvature, Etch characteristics, Deformation, Depth of
surface scratches. Ball bearing grading.

SOFT MATERIALS

Surface micro and macro structure, Texture, Shape, Q.A. in paper manufacture,
Quality control in pharmaceutical preparations, Fibres, Surface tension studies.

OTHER

Level control, Position control, Point of deviation.

TECHNICAL SPECIFICATIONS - PROBE

Spot size.................................... 1.5 microns
Minimum surface
reflectivity..... 2.0%
Maximum traverse speed........... 0.5mm/sec

Height resolution....................... 0.01 microns
Working
distance....................... 1.0 mm
Dimensions of probe..................
L100 x H34 x W36mm

CONTROLLER

Range.......................................... +/- 500, 100, 20 microns

Accuracy..................................... +/- 2% for 100 microns

.................................................... +/- 4% for 500 microns

Output voltage............................. +/- 5 volts FSD ~options
available)
Reflectivity output....................... 5 volts, 0-100%

Display........................................ 3 1/2 plus sign

Operating temperature range........ 0 to 40 °C
Operating humidity
range............. 20% to 90% RH non-condensing
Input
voltage................................ 220/240 volts 1 10/120 volts, AC 50/60
Hz
Dimensions.................................. W205 x H88 x D265mm

LaserSurf
Audley Scientific Ltd.
29 Audley Way
Ascot

Berkshire
SL5 8EE
UK

Tel: (+44) - (0)1344 883352

Tel: (+44) - (0)20 75947236 (at Imperial College London, Mech. Eng. Dept. -
Tribology Group. Ask for Dr Richard Wayte.)