Transcript Profilometer - Department of Mechanical Engineering

Dept. of Mechanical Engineering, IISc
ME-255 : PRINCIPLES OF TRIBOLOGY
Surface Properties - Measurement Techniques
Profilometer
Presented by
Balasenthil D
Sr.No. 08993
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
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
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…
Non - Contact Profilometer
• Pattern Projection Methods
 Fringe Projection
 Fourier Profilometry
 Moire
Contact & Pseudo – Contact Profilometer
• Stylus Profilometer
• Atomic Force Microscopy
• Scanning Tunneling Microscopy
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 ...
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
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 …
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 …
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.
Working Principle of Profilometer
(Non - Contact Optical Profilometer)
Contd …
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
interference fringes.
dark
bands
known
as
• The optical path differences are due to height
variances in the test surface.
Contd …
Working Principle of Profilometer
(Non - Contact Optical Profilometer)
• Constructive interference areas as lighter and the
destructive interference areas as darker.
Interference Image
• Light to dark fringes above represents one-half a
wavelength of difference between the reference path
and the test path.
Contd …
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.
Modes of Operation
(Non - Contact Optical Profilometer)
• Phase Shifting Interferometry (PSI) Mode
• Vertical Scanning Interferometry (VSI) Mode
Contd …
Modes of Operation
(Non - Contact Optical Profilometer)
System Performances
• Range: Highest vertical distance the profiler can
measure.
• Resolution: Smallest
accurately measure.
distance
the
profiler
can
 Lateral Resolution
 Vertical Resolution
• Accuracy: How closely a measured value matches the
true value & can be obtained by frequent calibration.
Surface Parameters
• Surface Topography: 3D representation of geometric
surface irregularities.
Contd …
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 …
Surface Parameters
• Amplitude 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
Max profile peak &
max profile valley
depth
Ra - info of friction &
wear
Rv - retaining of
lubricant
Max height of
surface
Gives overall
roughness of the
surface
Rp & Rv
Rt
Contd …
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.
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
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.
Measurement Examples
• Some of the profiles obtained are shown below:
600 GRIT SIZE:
UPD (in 2D):
UPD (in 3D)
Measurement Examples
• Surface of steel Block
• 3D Image
Reflection Intensity
Measurement Examples
• Pit on a thin iron plate
• Plate thickness 0.7mm
• (Depth 0.14494mm)
2D image
Measurement Examples
• 3D image
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
THANK YOU