Dept. of Mechanical Engineering, IISc

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. -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 …

21. Surface Parameters • Amplitude Parameters:

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 scanranges.

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 BlockReflection Intensity • 3D Image

26. Measurement Examples • Pit on a thin iron plate2D image • Plate thickness 0.7mm • (Depth 0.14494mm)

27. Measurement Examples • 3D image

28. References • Research Papers : • 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 http://en.wikipedia.org/wiki/Profilometer

29. THANK YOU