Profilometer (1)

How to measure surface roughness

1. Dept. of Mechanical Engineering, IISc
ME-255 : PRINCIPLES OF TRIBOLOGY
Surface Properties -Measurement Techniques
Profilometer
Presented by
Balasenthil D
Sr.No. 08993

2. CONTENTS
•Introduction
•Types of Profilometer
Contact
Non -Contact
•Working Principle
Optical Principle Basics
Modes of Operation
•System Performances
Range , Resolution & Accuracy
•Surface Parameters
Surface Topography & Amplitude Parameters
•Profilometers @ IISc
•Measurement Examples

3. INTRODUCTION
•Definition.
-Aprofilometerisadeviceusedtomeasurethe
roughnessofasurface.
-Givesdifferencebetweenthehighandlowpointof
asurfaceinnanometres.
•TypesofProfilometers.
Non-ContactProfilometers
ContactProfilometers

4. •Optical Methods
Vertical Scanning Interferometry
Phase -Shifting Interferometry
Differential Interference Contrast Microscopy
•Focus Detection Methods
Intensity Detection
Focus Variation
Differential Detection
Critical Angle
Astigmatic Method
Focault Method
Confocal Microscopy
Contd…
Non -Contact Profilometer

5. •Pattern Projection Methods
Fringe Projection
Fourier Profilometry
Moire
Non -Contact Profilometer
Contact & Pseudo –Contact Profilometer
•Stylus Profilometer
•Atomic Force Microscopy
•Scanning Tunneling Microscopy

6. Contact Profilometer
•Heightfrom10nanometresto1millimetre
•Radiusofdiamondstylusfrom20nmto25μm
•Horizontalresolutioniscontrolledbythescanspeed
anddatasignalsamplingrate.
Contd...

7. Contact Profilometer
•Advantages & Disadvantages
Acceptance&EasytoUse
SurfaceIndependence
Resolution:Thestylustipradiuscanbeassmall
as20nanometres
DirectTechnique:Nomodellingrequired.
Notsuitableforverysoft(orevenliquid)and
easilydamageablesurface
Veryhardanddamagesurfacecandamagethe
stylus
Only2D

8. Non -Contact Profilometer
•Usesbeamsoflighttoreadasurface
•Theyshootabeamoutandmeasurethetimeittakesto
return.
•nowearsincenoneofitspartstouchanything
Contd …

9. •Advantages of optical profilometers
GoodResolution:Verticalresolutionisusuallyinthe
nmlevel
HighSpeed
Reliability:cannotbedamagedbysurfacewearor
carelessoperators
Spotsizeorlateralresolutionrangesfromafew
micrometresdowntosubmicrometre.
Contd …
Non -Contact Profilometer

10. Non -Contact Profilometer
•Limitations:
Limitedbyveryhighslopes,wherethelightis
reflectedawayfromtheobjective,unlesstheslope
hasenoughtexturetoprovidethelight.
SurfaceModellingisrequiredtoconvertthedigital
codetohumanusabledata.

11. Working Principle of Profilometer
(Non -Contact Optical Profilometer)
Contd …

12. •Alightbeamissplit,reflectingfromreference
(known/flat)&testmaterial.
•Constructiveanddestructiveinterferenceoccurs
•Formsthelightanddarkbandsknownas
interferencefringes.
•Theopticalpathdifferencesareduetoheight
variancesinthetestsurface.
Contd…
Working Principle of Profilometer
(Non -Contact Optical Profilometer)

13. Working Principle of Profilometer
(Non -Contact Optical Profilometer)
•Constructiveinterferenceareasaslighterandthe
destructiveinterferenceareasasdarker.
•Lighttodarkfringesaboverepresentsone-halfa
wavelengthofdifferencebetweenthereferencepath
andthetestpath.
Contd …
Interference Image

14. Working Principle of Profilometer
(Non -Contact Optical Profilometer)
•From the above Interference Image:
Lower portion is out of focus means less
interference.
Greatest contrast means best focus.

15. •Phase Shifting Interferometry (PSI) Mode
•Vertical Scanning Interferometry (VSI) Mode
Contd …
Modes of Operation
(Non -Contact Optical Profilometer)

16. Modes of Operation
(Non -Contact Optical Profilometer)

17. •Range:Highestverticaldistancetheprofilercan
measure.
•Resolution:Smallestdistancetheprofilercan
accuratelymeasure.
LateralResolution
VerticalResolution
•Accuracy:Howcloselyameasuredvaluematchesthe
truevalue&canbeobtainedbyfrequentcalibration.
System Performances

18. •Surface Topography: 3D representation of geometric
surface irregularities.
Contd …
Surface Parameters

19. •Roughness: Closely spaced irregularities
•Waviness: More widely spaced irregularities
•Error of Form: Long period & non cyclic deviations
•Flaws: Discrete & infrequent irregularities
•Roughness & Waviness comprise the Surface
Texture
Contd …
Surface Parameters

20. •Amplitude Parameters:
Contd …
Surface Parameters
Term Definition Use
Ra The roughness
average (mean
height)
Gives roughness of
the machine surface
Rq RMS roughness Describes the finish
of optical surface
Rp & Rv Max profile peak &
max profile valley
depth
Ra -info of friction &
wear
Rv -retaining of
lubricant
Rt Max height of
surface
Gives overall
roughness of the
surface

21. Surface Parameters
•Amplitude Parameters:
Term Definition Use
Rz Average max
height of the
profile
Evaluating
surface texture on
limited access
surfaces
Rsk Skewness-
measure of
asymmetry of the
profile about the
mean line.
Gives load
carrying capacity,
porosity &
characteristic of
non-conventional
machining
processes.

22. •Optical surface profilometer
Make –Veeco NT1100
Type –Non Contact type
Principle of Operation
•VSI g interferometry (VSI)
•Phase-shifting interferometry (PSI).
Range
•VSI –2mm
•PSI –160nm
Resolution
•Vertical Resolution : PSI –3Å & VSI –3nm
Lateral Resolution --Function of magnification objective and
the detector array size you choose
Profilometers @ IISc

23. •Nanoscience Profilometer
Filmthicknessmeasurementfrom5microns
downto300nmorless
4millionpixelcameraforhighresolution
Auto-rangeandauto-fringe-findforeaseofuseof
Singlemodeofoperationoverallscanranges.
Profilometers @ IISc

24. Measurement Examples
•Some of the profiles obtained are shown below:
600 GRIT SIZE:
UPD (in 2D): UPD (in 3D)

25. •Surface of steel Block Reflection Intensity
•3D Image
Measurement Examples

26. •Pit on a thin iron plate 2D image
•Plate thickness 0.7mm
•(Depth 0.14494mm)
Measurement Examples

27. •3D image
Measurement Examples

28. •Research Papers:
T.V.Vorburger, J.Raja.
Surface Finish Metrology Tutorial
June 1990
WYKO Surface Profilers TechnicalReference manual
September 1999, Version 2.2.1
•Webpage
Profilometer, Wikipedia
http://en.wikipedia.org/wiki/Profilometer
References

29. THANK YOU