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

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

3. INTRODUCTION Definition.
- A profilometer is a device used to measure the roughness of a surface.
- Gives difference between the high and low point of a surface in nanometres.
Types of Profilometers.
Non - Contact Profilometers
Contact Profilometers

4. Non - Contact Profilometer
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…

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

6. Contact Profilometer Height from 10 nanometres to 1 millimetre
Radius of diamond stylus from 20 nm to 25 μm
Horizontal resolution is controlled by the scan speed and data signal sampling rate.
Contd ...

7. Contact Profilometer Advantages & Disadvantages
Acceptance & Easy to Use
Surface Independence
Resolution : The stylus tip radius can be as small as 20 nanometres
Direct Technique : No modelling required.
Not suitable for very soft (or even liquid) and easily damageable surface
Very hard and damage surface can damage the stylus
Only 2D

8. Non - Contact Profilometer
Uses beams of light to read a surface
They shoot a beam out and measure the time it takes to return.
no wear since none of its parts touch anything
Contd …

9. Non - Contact Profilometer
Advantages of optical profilometers
Good Resolution: Vertical resolution is usually in the nm level
High Speed
Reliability : cannot be damaged by surface wear or careless operators
Spot size or lateral resolution ranges from a few micrometres down to sub micrometre.
Contd …

10. Non - Contact Profilometer
Limitations:
Limited by very high slopes, where the light is reflected away from the objective, unless the slope has enough texture to provide the light.
Surface Modelling is required to convert the digital code to human usable data.

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

12. Working Principle of Profilometer (Non - Contact Optical Profilometer)
A light beam is split, reflecting from reference (known/flat) & test material.
Constructive and destructive interference occurs
Forms the light and dark bands known as interference fringes.
The optical path differences are due to height variances in the test surface.
Contd …

13. Working Principle of Profilometer (Non - Contact Optical Profilometer)
Constructive interference areas as lighter and the destructive interference areas as darker.
Light to dark fringes above represents one-half a wavelength of difference between the reference path and the test path.
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. Modes of Operation (Non - Contact Optical Profilometer)
Phase Shifting Interferometry (PSI) Mode
Vertical Scanning Interferometry (VSI) Mode
Contd …

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

17. System Performances
Range: Highest vertical distance the profiler can measure.
Resolution: Smallest distance the profiler can accurately measure.
Lateral Resolution
Vertical Resolution
Accuracy: How closely a measured value matches the true value & can be obtained by frequent calibration.

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

19. Surface Parameters 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 …

20. Surface Parameters Amplitude Parameters: Contd … Term Definition Use
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. Profilometers @ IISc 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

23. Profilometers @ IISc Nanoscience Profilometer
Film thickness measurement from 5 microns down to 300 nm or less
4 million pixel camera for high resolution
Auto-range and auto-fringe-find for ease of use of Single mode of operation over all scan ranges.

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

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

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

27. Measurement Examples
3D image

28. References Research Papers : Surface Finish Metrology Tutorial
T.V.Vorburger, J.Raja.
Surface Finish Metrology Tutorial
June 1990
WYKO Surface Profilers Technical Reference manual
September 1999, Version 2.2.1
Webpage
Profilometer, Wikipedia

29. THANK YOU