Advanced precise and accurate nanomeasurement techniques play an important role to improve the function and quality of surface characterization. There are two basic approaches, the hard measuring techniques and the soft computing measuring techniques. The advanced soft measuring techniques include coordinate measuring machines, roundness testing facilities, surface roughness, interferometric methods, confocal optical microscopy, scanning probe microscopy, and computed tomography at the level of nanometer scale. On the other hand, a new technical committee in ISO is established to address characterization issues posed by the areal surface texture and measurement methods. This paper reviews the major advanced soft metrology techniques obtained by optical, tactile, and other means using instruments, classification schemes of them, and their applications in the engineering surfaces. Furthermore, future trends under development in this area are presented and discussed to display proposed solutions for the important issues that need to be addressed scientifically.
Surface metrology became very important in many branches of science and industry. Study of dimensional and surface nanometrology is becoming more commonplace in many applications and research environments as well as data treatments dealing with standardized rules. Therefore, surface characterization using advanced accurate and precise nanomeasuring techniques are important tools especially in the production engineering, tribology, biotechnology, and criminology. Because of this diversification, there are more advanced metrology techniques using stylus, optical, and nonoptical methods used for analyzing the surface characteristics, where each technique has its own specific applications [
The ISO technical committee TC-213 in the field of dimensional and geometrical product specifications and verification formed a working group WG-16 to address standardization of areal (3D) surface texture and measurement methods, and to review existing standards on traditional profiling (2D) methods including characteristics of instruments. In 2007, the project of this working group was to develop standards for three basic methods of areal surface texture measurements [
In this paper, novel techniques used such as coordinate measuring machine (CMM), roundness testers, roughness measurement instrument, white light interferometer (WLI), confocal optical microscopy, digital holography, scanning probe microscopy (SPM), and computed tomography (CT) methods are investigated. One of the major challenges when moving to smaller measurements is selecting the suitable metrology technique for the desired measurement. Standardization processes will be probably increased in terms of methods of measurements and data treatments for specific applications due to the externalization and diversification of products. These different advanced techniques have currently advantages meeting the samples specifications and required properties. Therefore, it is important to be aware of how techniques can affect the measured parameters according to specific accurate and precise strategy of measurement. The new applications of dimensional and surface nanometrology in materials science, automotive industry, tissue engineering, and banknote paper will be considered. Moreover, future directions under development will be presented and discussed scientifically in order to introduce proposed solutions for the issues that need to be addressed in the area of interest.
The 3D surface metrology techniques have been rapidly developed in the last decade due to the advanced computational software technology. Mechanical contact stylus, optical, and nonoptical measurement techniques achieved significant progress in many different applications.
The tactile stylus measurement techniques as a coordinate metrology and roundness facilities are powerful tools in modern engineering industries [
Advances in software during the 1980s allowed CMMs to have error corrections and provided geometric computations [
New generation of advanced coordinate metrology provides ultraprecision CMM with large measurement volume (
New Isara 400 CMM. Figure is taken from [
Concept of new CMM
Measurement using the Triskelion probe
Tactile probes, such as the presented Triskelion ultra precision touch probe, as well as other possible (optical) probe systems, can be used to perform scanning at discrete points of object. The presented Isara machine provides a technology that can be adapted and optimized for specific user requirements. However in the future, there is other new trend to produce a new CMM machine with multiple sensors (tactile and optical) in a cooperation research. It will be used in many applications with relative high level of accuracy [
The future trends in advanced CMM have been discussed. A novel type compact five-coordinate measuring machine with laser and CCD compound probe has been designed and built up as presented in [
The overall mechanical structure of five-coordinate measuring machine and probes. Figure is taken from [
The step motors with subdivision function are applied to drive each axis. Among them, the motor for A-axis has contracting brake device which will lock the motor mainshaft and prevent collision of the probe and worktable in case of accidental power off. The high-precision ball screws are applied to drive
The profile form of the roundness is of primary significance and is an important aspect of engineering surface for cylindrical features, especially in the modern investigations and quality control problems. The development of software analysis tools and their validation is also another major challenge facing the industry. Advanced mathematical techniques are incorporated into such software systems to provide further reference algorithms [
In Russia, Bogomolov et al. [
Sample results of developed roundness measurement system in Russia. Figure is taken from [
2D roundness measurement
3D waviness measurement
In UK from 2000 until now, Taylor Hobson entered a new phase of innovative product design using advanced software [
The analysis of structured surfaces, those with repetitive patterns, requires entirely new methods and techniques [
Results obtained from Talyrond-395. Figure is taken from [
On the other hand, new ideas are suggested for new roundness measurement techniques in the future [
Principle of the combined three-point method for roundness measurement system. Figure is taken from [
Another idea of noncontact probe has been proposed to measure the diameter and the roundness of turned objects [
The probe configuration for roundness measurement. Figure is taken from [
The signal from the amplifier circuit converts to the PC with LabView environment and is processed to extract the OOR of the rotating workpiece. The result shows that the extensive roundness tests have been determined to validate the performance of the probe. The measurements made using the laser-based probe are averages of at least 10 repeated measurements. The out-of-round results were compared with the results obtained from Taylor Hobson. The probe performance gives a maximum error of 0.5
A profilometer technique was first constructed by Abbott and Firestone’s in 1933 [
In this case, the slide can be measured by a laser interferometer and its errors can be collected in the microprocessor system and used for the correction of indication. Besides, the measuring instruments often offer simultaneous measurement of roughness and outline with greater range—even above 2 mm with 0.6 nm resolution. The interesting element of this device is a probe—magnetically fixed, which prevents damage of any impact or overload applied to the part. The diamond needle is separated from the body on three-point magnetic holder. Additionally, the probe is equipped with an amplitude modulation transmitter and a receiver, which is used for communication with a central processing unit as presented in detail in [
Two modulations of amplitude in roughness measurement. Figure is taken from [
Measurements based on a stylus profilometer in 3D surface topography are time consuming, which is a significant limitation. A possibility of overcoming this inconvenience is spiral sampling [
Application of spiral sampling. Figure is taken from [
Principle of a VIS Figure is taken from [
Unfortunately, the resolution of VSI is in the nanometer range, not in fractions of nanometers. The advantages of PSI and VSI are combined in the EVSI technique, also called white light interferometry with phase shifting [
Light is at once the most sensitive and the gentle probe of measurement. Light is easy to generate using light-emitting diodes or lasers, and to detect using ultrasensitive photodetectors. Light has become an indispensable nanometrology tool for surface characterization. For these reasons, a number of optical techniques have been developed for line profiling and areal topography. These techniques can provide approaching diffraction of spatial resolution limit. Optical methods have the advantage that they are noncontacting and hence nondestructive tests. Optical methods based on imaging and microscopy also have a higher speed than contacting techniques which rely on mechanical scanning of a contacting probe. However, optical methods are sensitive to a number of surface qualities besides the surface height. These include optical constants, surface slopes, fine surface features that cause diffraction, and deep valleys in which multiple scattering may occur. In addition, scattering from tested surfaces within the optical system produces stray light in the system that can affect the accuracy of an optical profiling method. High sensitive methods, such as phase shifting interferometric (PSI) microscopy have vertical resolution of 0.1 nm [
Interferometers and microscopes are combined in interferometric microscopy. Through this combination, very good resolution and significant vertical range can be obtained. Interferometry as a measurement tool is certainly not new but combining old interferometry techniques with modern electronics, computers, and software has produced extremely powerful measurement tools [
Principle and schematic diagram of a white light interferometer (WLI) system.
Principle of a WLI. Figure is taken from [
Schematic diagram of setting. Figure is taken from [
White light system is used rather than monochromatic light system because it has a shorter coherence length that will give greater accuracy. Different techniques are used to control the movement of the interferometer and to calculate the surface parameters. The accuracy and precision repeatability of the scanning white light measurement are depending on the control of the scanning mechanism and the calculation of the surface properties from the interference data. Another important factor in WLI system is the interference objective that is used [
A low magnification objective can be used to look at large areas but the resolution is controlled by the resolution of the detector. Higher resolution images need higher magnification objectives but a smaller area has to be measured. The current lateral resolution limit for white light interferometry is about 0.5
Confocal optical microscopy is one of the most widely used advanced techniques in surface metrology. It is called confocal because this type of microscope has two lenses having the same focus point, just as the name might imply. The confocal microscope incorporates the ideas of point-by-point illumination of the specimen and rejection of out-of-focus light. The basic principle of the operation of the confocal microscope is discussed in [
The principles of optical system of the scanning confocal microscope. Figure is taken from [
WLI and confocal microscopy seem good, particularly versatile. PSI is limited to smooth surfaces, whereas the vertical dynamic range of WLI and confocal microscopy extends from the nanometer level (noise) to a large range [
Schematic diagram of a confocal white light sensor for a profilometer.
Schematic diagram. Figure is taken from [
Measuring range principle. Figure is taken from [
Other scanning microscopes are applied to analyze surface of objects. Among these are two families of devices: scanning electron microscopes (SEM) and scanning probe microscopes (SPM). SEMs are used rarely in the investigation of roughness whereas SPMs are becoming more and more popular. SEM is an optical method microscope technique that has been accepted in the nanoscale measurements. It allows to obtain very good vertical resolution. Serious problems appear only in the case of very rough surfaces and the necessity to use a larger vertical range. Microscope application can cause a little difficulty in the interpretation of results of measurement, especially when samples have inclusions or impurities on the surface with different characteristics or can have an influence on the response of instrument.
Dennis Gabor invented holography as a method for recording and reconstructing the amplitude and phase of a wavefield in 1948. Digital holography (DH) technique is established as an important scientific tool for applications in imaging, microscopy, interferometry, and other optical disciplines [
Schematic setup of digital holography technique. Figure is taken from [
The scanning probe microscope (SPM) is a family of mechanical probe microscopes that scans the object in order to measure surface morphology in areal space with a resolution down to the atomic level [
Atomic force microscope is an advanced and important device in the family of SPMs as a nonoptical measuring technique. The principle of AFM operation is based on surface scanning using an elastic cantilever with a sharp tip. The tip presses down to the surface with a small constant force. The tip has height from a small part of a micrometer up to 2
General principle of STM (left) and AFM (right). Figure is taken from [
There are some significant advantages of AFM as an imaging tool in surface metrology when compared with complementary techniques such as electron microscopy. In real time, AFM is currently able to achieve surface characterization of engineering nanomaterials and biomedicine more accurate than electron microscopes. AFM works at three different modes: non-contact mode, dynamic contact mode, and tapping (resonant) mode. AFM measures the accurate forces acting between a fine probe tip and surface of an object sample. The tip is attached to the free end of a cantilever and brought very close to a surface of sample. Attractive or repulsive forces resulting from interactions between the tip and the measured surface will cause a positive or negative bending of the cantilever. The bending is dedicated by means of a laser beam, which is reflected from the backside of the cantilever. Figure
Operation of AFM system control loop. Figure is taken from [
AFM image result in 2D and 3D. Figure is taken from [
One of the new developed concepts in the last years is the computed tomography (CT) metrology using X-rays. computed tomography (CT) metrology is a technology to measure both internal and external geometries simultaneously in a great variety of parts. Therefore, the CT can be used not only as a simple inspection method but also as a measuring principle capable of providing accurate geometrical information. CT is in the process of revolutionizing quality engineering in industry [
Principle operation of CT technique. Figure is taken from [
The CT machine consists of an X-ray source, a translational movable rotary table where the part to be scanned is placed on an X-ray detector, and a processing unit (composed by 6 processors working together) to analyze and display the measurement results, Figure
Components of Metrotom CT. Figure is taken from [
CT technique provides an enormous amount of information and makes components transparent in the true sense inspection of machine spare parts. Several sources of error [
Over the past years, many metrological techniques of dimensions and surface measurements have matured and evolved as presented in Section
Steadman diagram showing the range and resolution of dimensional measurement techniques (mechanical stylus, interferometric optical microscopes, and AFM/SPM). Figure is taken from [
It is obvious that there are conjoint area between the measurement techniques, which span a wide range and resolution. This indicates that there is generally a measurement solution for a wide variety of applications, including most that might be encountered in the engineering industries and applied technologies. The overlap between dimension and surface instrumentation techniques produces important benefits such as the following. It provides competition between different technological techniques. It allows for a broader selection of instruments. It provides means for comparison.
The limitation keys of existing techniques are miscellaneous. Categories of the optical techniques are sometimes slightly artificial, not as in the case of the mechanical contact stylus techniques. Instruments which are the combination of several techniques have been created more frequently recently. It allows to broaden the measurement range significantly while keeping very high resolution. An example of this solution is the interferometric microscope. General treatment of optical methods is very cautious while on the other hand the classic profilometric methods are used confidently. This situation is not incidental and results from many factors, for example, application of the optical methods is sometimes questionable due to the fact that the estimation of the object surface the whole mathematical models based on some assumption are used instead of using the surface itself. Moreover, results obtained from the optical methods depend sometimes on physical properties of the surface. In metals, for example, reflectivity is the significant parameter in contrast to some other materials where it is much lower; sometimes it is so low that a large amount of the incident light penetrates the material [
In the case of the layered surface, multiple reflections on different layers may occur. Diversity of the penetrations influences the optical length path and changes test results. The presence on the surface of elements which randomly disturb the light path, for example, small radius of curvature, microcracking, or microholes, might be another reason for the abnormality. Further, the optical techniques cannot always be compared with stylus detection techniques, which sometimes make comparison of test result impossible. Based on a number of comparative analyses some practical limitations for stylus and optical techniques have been determined [
Data collected from measurements is the starting point for many processes and may be used in different ways [
Many different applications in the dimension and surface characterization using advanced nanometrology techniques, whether 2D and 3D, in both micro- and nanometer scale can been presented. Many works present some new and promising approaches that may play an important role in industry and different other applications using advanced metrology techniques. Thus, the macroengineering applications and surface porosity in the micro- and nanoscales have been presented.
Surface metrology in mechanical engineering must be fast, accurate, robust, automated, and ideally integrated into the production line or product assessment, especially in materials science and automotive industry. With regard to the applications, CMMs offer a complete range of metrology solutions for many inspection tasks in different fields, in automotive industry and tribology. Some applications in CMM have been developed over the last years. The most familiar and earliest commercial application of surface texturing is that of automotive engine cylinder liner as a critical metallic element. Inspection programs of mechanical designated parts in automotive desiel engines the processes of measuring their dimensional and geometrical features has been developed and presented in [
The topography of surfaces is commonly used to analyze surfaces after different operations and/or machining processes. The most familiar and earliest commercial application of surface texturing is that of automotive engine cylinder liner as a critical metallic element. At first, the recommended cylinder surface after honing was very smooth since it showed high wear resistance during running-in. Considerable progress in engine construction causes a great scuffing inclination of the smooth cylinder surface. Only rough surfaces have a higher load-carrying capacity. Running-in wear studies was conducted by the authors of [
Plateau surface roughness using developed WLI technique. Figure is taken from [
The topography of engineering surfaces is commonly used to analyze surfaces before and after operation processes. The applications of texturing include pistons, brake discs, bearings, mechanical face seals, gas seals, hard disk sliders, machine tools guideways, and other elements. One can find recent publications presenting profitable effects of surface texturing on seizure resistance in [
The cylinder liner and piston top compression ring have been both measured both with an atomic force microscope (AFM) and white light interferometer (WLI) [
WLI images of (a) piston ring and (b) cylinder liner. Figure is taken from [
Engine piston ring (unworn section left, worn section right)
Engine cylinder liner (unworn left, worn right)
The piston ring is chromium coated and exhibits little wear apart from some minor scratching and smoothing in the direction of sliding. The cylinder liner is made of much softer cast iron and becomes markedly different after having been worn in the engine. The plateaux have been massively smoothed leaving the deep honing grooves clearly visible. Typical measurements for the four surfaces are given in Figure
AFM images of (a) piston ring and (b) cylinder liner. Figure is taken from [
Engine piston ring (unworn left, worn right)
Engine cylinder liner (unworn left, worn right)
Many other applications using surface metrology are presented. These fields of applications as road surface irregularity, architecture art tools, banknote paper, and biomaterial with tissue engineering using dimensional and surface metrology techniques have been studied and analyzed. Thus, the inspection of concrete structures as a transportation infrastructure investment is a major part of roads management using surface metrology.
In surface metrology, macrostructural application using SEM micrographs has been presented by the author of this work et al. in [
Figure
SEM images for nanocomposites. Figure is taken from [
CNTs/PVC
CNTs/PMMA
CNTs/PS
Surface roughness of an architecture artist tool has been studied using laser scanning microscope (LSM) technique [
Various results obtained by using LSM. Figure is taken from [
Surface topography analysis is often used in the paper and banknote industry. Because of the delicacy of the investigated surface, stylus measurements are replaced by other techniques mainly based on light scattering, although acoustic sensors [
2D surface of rough paper. Figure is taken from [
3D topography image of a banknote [
The next application is the analysis of the surface of shot fired from the gun, which is used for gun identification [
Research applications of surface topography in medicine and bioengineering can be without hesitation admitted as being a real triumph of the end of the last millennium and the beginning of the new one. A review of applications from bioengineering has been described in [
Photograph and SEM images of implanted cylindrical pin biomaterial. Figure is taken from [
In new study, the advanced CT reconstruction technique for measuring an instantaneous 3D distribution of chemiluminescence of a turbulent premixed flame has been accomplished for a turbulent propane-air rich premixed flame. These displays help us to recognize the detail and total shape of objective flame. It can be clearly seen that the CT technique is able to clearly distinguish between the dental bone extracted from the two different sockets [
Micro-CT 3D render image of bioscaffold regenerated bone sample. Figure is taken from [
Xenograft (left)
Bioscaffold (right)
Uncertainty in measurement results of any metrological technique is considered as an important guide to the quality of the measurement procedure. One of the problems in evaluation of dimensional and surface measurements is that different factors affecting the total uncertainty cannot be separated. One can generally distinguish two types of uncertainty. The first one determines the systematic errors, which can be corrected theoretically. The second one determines the random errors. Recent research works involving the uncertainty resulting from measurement operations and their estimation in both contact and non-contact measurement methods have been carried out [
In CMM, Marsh et al. [
The uncertainty in the multisensorial measurement system consists of an optical light-section system and a shading system has been studied [
In spite of the information given by the previous studies of AFM tip-sample interactions, some problems are still unresolved in evaluating the uncertainty. An algorithm for the evaluation of the error and uncertainty contribution has been tested and developed with experimental results obtained from four step heights [
In this paper, a review of advanced measuring techniques in the dimensional and surface metrology and their applications from micro- to nanoscale has been presented in detail. Recent progress and future trends under development in this area have been presented and discussed. The following are the major observations from the literature. The advanced nanomeasuring techniques are very important in the surface metrology for understanding the properties of the objects quality, design purposes, diagnostics, and high throughput screening. Both contact and non-contact metrology techniques are available methods for objects characterization. It is clear that the mechanical stylus instrument is viewed as the fundamental method of measurements and the mechanical surface analyses. However now, probe-scanning techniques are capable of characterizing the case of geometric surfaces in 3D. Optical nanomeasuring techniques have been reviewed recently because of their important role. For accurate topographic measurements with optical methods, there are a number of issues to be considered as slope limitations, smoothing, focus condition, stray light, surface detection algorithms, shadowing, and multiple scattering. Some important issues need urgent attention: acquisition of detected data in an economical and efficient way, filtering of noisy data, and extracting the statistical feature of the data. The hybrid opto-tactile probing system and nanoultraprecision techniques need more research to reach high accuracy in the feature. Multiintegrated microscope as a combination between atomic force microscope and 3D optical profilometer needs advanced research to reach combine advantages in the future. The overlapping between dimensional measuring techniques needs new investigation in the context of presented advanced technology. With tremendous progress, development of ISO standards becomes an essential requirement within the recent time. This may require the support and establishment of new technical committees.
If these issues are addressed, the engineering industrial application will become easy and fruitful task.