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Profilometer is a measuring instrument used to measure a surface's profile, in order to quantify its roughness.

While the historical notion of a profilometer was a device similar to a phonograph that measures a surface as the surface is moved relative to the contact profilometer's stylus, this notion is changing with the emergence of numerous non-contact profilometery techniques.
Contents1 Types
1.1 Contact profilometers
1.2 Non-contact profilometers
2 Road pavement profilometery
3 References
4 External links

Original 1940s Taylor-Hobson Talysurf surface profile measuring machine

Optical methods[1][2]

Vertical Scanning Interferometry/White-light interferometer
Phase Shifting Interferometry
Differential interferencecontrast microscopy (Nomarski Microscopy)
Focus detection methods
Intensity Detection
Focus variation
Differential Detection
Critical Angle Method
Astigmatic Method
Focault Method
Confocal microscopy
Pattern projection Methods
Fringe projection
Fourier Profilometry

Contact andpseudo-contact methods[1][2]

Stylus profilometer (mechanical profilometer)[3]
Atomic Force Microscopy
Scanning Tunneling Microscopy

Contact profilometers

A diamond stylus is moved vertically in contact with a sample and then moved laterally across the sample for a specified distance and specified contact force. A profilometer can measure small surface variations in vertical stylusdisplacement as a function of position. A typical profilometer can measure small vertical features ranging in height from 10 nanometres to 1 millimetre. The height position of the diamond stylus generates an analog signal which is converted into a digital signal stored, analyzed and displayed. The radius of diamond stylus ranges from 20 nanometres to 50 μm, and the horizontal resolution is controlledby the scan speed and data signal sampling rate. The stylus tracking force can range from less than 1 to 50 milligrams.

Advantages of contact profilometers:

Acceptance: Most of the world's surface finish standards are written for contact profilometers. To follow the prescribed methodology, this type of Profilometer is often required.
Surface Independence: Contacting the surface isoften an advantage in dirty environments where non-contact methods can end up measuring surface contaminants instead of the surface itself. However, because the stylus is in contact with the surface, this method is not sensitive to surface reflectance or color.
Resolution: The stylus tip radius can be as small as 20 nanometres, significantly better than white-light optical profiling. Verticalresolution is typically sub-nanometer as well.
Direct Technique: No modeling required.

Non-contact profilometers

An optical profilometer is a non-contact method for providing much of the same information as a stylus based profilometer. There are many different techniques which are currently being employed, such as laser triangulation (triangulation sensor), confocal microscopy (used forprofiling of very small objects), low coherence interferometry and digital holography.

Advantages of optical profilometers

Speed: For small steps and requirements to do 3D scanning, because the non-contact profilometer does not touch the surface the scan speeds are dictated by the light reflected from the surface and the speed of the acquisition electronics. For doing large steps, a 3Dscan on an optical profiler can be much slower than a 2D scan on a stylus profiler.
Reliability: optical profilometers do not touch the surface and therefore cannot be damaged by surface wear or careless operators. Many non-contact Profilometers are solid-state which tends to reduce the required maintenance significantly.
Spot size: The spot size, or lateral resolution, of optical...