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A new surface metrology instrument, the ‘Swinging Part Profilometer’ (SPP), has been developed for in-situ measurement of optics undergoing robot-processing in the ground (non-specular) state. In this paper, we present the hardware-design of the SPP, together with software for hardware-control, data-acquisition and surface-reconstruction. First results on a sample part are presented, compared with interferometric metrology, and error-contributions considered. Notably, during each individual scan of a measurement-cycle, the probe remains fixed. This lends itself to automated probe-deployment by the same robot as performs surface-processing, as probe stability is required on only the time-scale for a single scan.

The swing arm profilometer realizes the measurement of the different surface shape by adjusting the axis of the arm bearing and the axis of the workpiece bearing for different spatial positional relationships,so the high precision positional relationship between the axis of the arm bearing and the axis of the workpiece bearing is the premise to obtain accurate result. This paper presents a way using four-based laser trackers to calibrate the axes of the swing arm profilometer,that satisfies the requirement of the high precision and the dynamic calibration. The four-based laser trackers system only uses the precise distances to obtain the coordinates of points. The coordinates of points in the rotate arc of the axes can fit the axes，and the relationship between the axes can be know. The study of the self-calibration of the four-based laser trackers, the arrangement of four-based laser trackers, the design of the calibration method and the processing of measurement data are included in this paper. Finally, the study is validated by the preliminary experiment.

The use of autocollimator-based profilometers of the Nanometer Optical measuring Machine (NOM) design has been reported for the evaluation of X-ray optics for some time. We report a related development in the use of a non-contact NOM profilometer for the in situ measurement of base radius of curvature and conic constant for E-ELT primary mirror segments during fabrication. The instrument is unusual in NOM design in that it is deployable onto a CNC polishing machine in an industrial fabrication environment. Whilst the measurement of radius of curvature of spherical surfaces over a single scan has been reported previously, here we report on the use of this instrument to measure optical surfaces with an aspheric departure of 180 micrometers using a grid of multiple scans and bespoke surface fitting software. The repeatability of the measurement has been found to be approximately 1 mm in a measured radius of curvature of approximately 90 m. The absolute accuracy is limited by the accuracy of the calibration of the autocollimator and the in situ calibration of the instrument during operation.

When using the swing arm profilometer (SAP) to measure the aspheric mirror and the off-axis aspheric mirror, the error of the effective arm length of the SAP has an obvious influence on the measurement result. In order to reduce the influence of the effective arm length and increase the measurement accuracy of the SAP, the laser tracker is adopted to measure the effective arm length. Because the space position relationship of the probe system for the SAP is needed to measured before using the laser tracker, the point source microscope (PSM) is used to measure the space positional relationship. The measurement principle of the PSM and other applications are introduced; the accuracy and repeatability of this technology are analysed; the advantages and disadvantages of this technology are summarized.

When the swing arm profilometer(SAP) measuring the mirror, the effective arm length of SAP which haves an obvious influence on the measurement results of the mirror surface shape needs to be measured accurately. It requires the measurement uncertainty of the effective arm length to reach 10μm in order to meet the measurement requirements, in this paper, we present a kind of technology based on laser tracker to measure the effective arm length of SAP. When the swing arm rotates around the shaft axis of swing arm rotary stage, the probe and two laser tracker balls form three sections of circular arc around the shaft axis of swing arm rotary stage in space. Laser tracker tracks and measures the circular arcs of two laser tracker balls, the center coordinates of the circular plane of circular arc can be calculated by data processing. The linear equation that passes through the two center coordinates is the equation of the shaft axis of rotary stage, the vertical distance from the probe to the shaft axis of rotary stage which can be calculated refer to the equation from the point to the line is the effective arm length. After Matlab simulation, this measurement method can meet the measurement accuracy.

The accuracy of stylus profilometer sensor directly affects the performance of the profilometer. To ensure good status of the profilometer, the accuracy features of the profilometer sensor should be verified regularly. However by now, only standard samples with comprehensive parameters are adopted for verification of the total profilometer, and there is no verification device for stylus profilometer sensor, especially for that with large range and high resolution. In this paper, a special verification device for stylus profilometer sensor is introduced. The device consists of displacement generation unit, displacement measurement unit and data acquisition and feature analysis software unit. A motor and PZT are combined to be a large range and high resolution displacement generator in the displacement generation unit, and a grating interference displacement measurement unit gives standard value of the displacement. When a sensor should be verified, the displacement generation unit generates displacement within the measuring range of the stylus sensor, and the displacement is input to the sensor, the output of the senor is compared with the data measured by the grating interference displacement measurement unit, and the acquisition and feature analysis software unit shows the accuracy features of the stylus sensor. A double frequency laser interferometer is applied to the verification device for experimental testing, its high accuracy, stability, reliability and wide range is verified, which satisfies the large-scale verification requirement of stylus profilometer sensor.

In a 3D profilometer by the fringe projection, the shadow will be produced inevitably, thus the fringes cannot be detected in the region of the shadow. In addition, a smooth surface or a metal surface produces the specular reflection, and then, no projection fringe can be recorded in the region of oversaturation on CCD. This paper reveals a proposed system for improved these defects and shows some preliminary improved 3D profiles by the proposed dual fringe projection. To obtain the profile of sample hided in the shadow and the oversaturation, this study used the dual-projection system by two projectors. This system adopted two different directions of fringe projection and illuminates them alternately, therefore, the shadow and the oversaturation produced in their corresponding locations. Two raw 3D profiles obtained from taking the dual-projection by the four-step phase-shift. A set of algorithms used to identify the pixels of the shadow and the oversaturation, and create an error-map. According to the error-map to compensate, two 3D profiles merged into an error-reduced 3D profile. We used the solder paste as a testing sample. After comparatively analyzing the 3D images obtained by our measurement system and by a contact stylus profilometer, the result shows that our measurement system can effectively reduce the error caused by shadows and oversaturation. Fringe projection system by using a projector is a non-contact, full field and quickly measuring system. The proposed dual-projection by dual-projectors can effectively reduce the shadow and the oversaturation errors and enhance the scope of application of the 3D contour detection, especially in the detection of precision structure parts with specular reflection.

Many aspheres and free-form optical surfaces are measured using a single line trace profilometer which is limiting because accurate 3D corrections are not possible with the single trace. We show a method to produce an accurate fully 2.5D surface height map when measuring a surface with a profilometer using only 6 traces and without expensive hardware. The 6 traces are taken at varying angular positions of the lens, rotating the part between each trace. The output height map contains low form error only, the first 36 Zernikes. The accuracy of the height map is ±10% of the actual Zernike values and within ±3% of the actual peak to valley number. The calculated Zernike values are affected by errors in the angular positioning, by the centering of the lens, and to a small effect, choices made in the processing algorithm. We have found that the angular positioning of the part should be better than 1, which is achievable with typical hardware. The centering of the lens is essential to achieving accurate measurements. The part must be centered to within 0.5% of the diameter to achieve accurate results. This value is achievable with care, with an indicator, but the part must be edged to a clean diameter.

This paper presents the huge advance in metrology represented by a new free-form profilometer, the Profilometer/Rotondimeter (MPR-700). The MPR-700 is a 3D metrological machine capable to measure quasicylindrical and free-form normal incidence optics maintaining the 2D measuring error below 40 nm at 2σ up to a length of 700 mm. The key to success of MPR is its innovative detection system design that boasts remarkable advantages in the positioning error reduction and to the instantaneous subtraction of the dynamical error. These characteristics make the MPR extremely precise and accurate, insomuch that measurements can be acquired in flight at high speed maintaining the measuring performances. The main advantage of the MPR design is the capability to couple the measuring quality offered by one-dimensional profilometer to the opportunity to the three-dimensional motion of a 3D machines. Here we present the MPR design and the results obtained on single profiles measurements and 3D shape reconstruction for optics of different geometry.

Although low coherence interferometers are commercially available (e.g., white light interferometers), they are generally quite bulky, expensive, and offer limited flexibility. In the paper the new portable profilometer based on low coherence interferometry is presented. In the device the white light diode with controlled spectrum shape is used in order to increase the zero order fringe contrast, what allows for its better and quicker localization. For image analysis the special type of CMOS matrix (called smart pixel camera), synchronized with reference mirror transducer, is applied. Due to hardware realization of the fringe contrast analysis, independently in each pixel, the time of measurement decreases significantly. High speed processing together with compact design allows that profilometer to be used as the portable device for both in and out door measurements. The capabilities of the designed profilometer are well illustrated by a few application examples.

Common profilometers cannot be used to measure the complex surfaces with large range. A cantilever profilometer with large range and high accuracy is presented in this paper. The profilometer is composed of inductive sensors, gratings and angle measurement structure, which are used to measure surface profile, movement displacement and angle of the cantilever beam separately. The angle measured by the invariant light-distance structure based on auto-collimation principle is used to compensate the Abbe error to ensure high measurement accuracy. For counting accurately, a method of resistance chain subdivision is designed to process the grating interference fringe signal. Experiment results show that the Abbe error can be compensate through the invariant light-distance structure based on auto-collimation principle. The designed profilometer can be used to measure complex morphology.

In this paper we provide a vertical scanning white light interfering profilometer based on Linnik type interference microscope. A vertical scanning system with coarse-fine dual-stage actuators is developed, in which the coarse positioning is performed by inclined sliding guides, AC servo motor, ballscrew and the fine positioning is performed by parallel board flexure hinge and piezoelectric ceramic, respectively. The displacement range of the vertical scanning system is 0~2mm and 0.4nm theoretical motion resolution can be achieved. The whole interference microscope of the profilometer is driven by the vertical scanning system, which will eliminate the movement coupling error of vertical direction caused by horizontal movement of 2D precision stage. The interference fringes or the focal plane can be automatically located by moving the vertical scanning system. To eliminate the measurement errors of the profilometer caused by incorrect positioning of the vertical scanning system, its displacement is measured in real-time by a laser interferometer with theoretical resolution of 0.01nm. A single groove specimen with the depth of 1.26μm calibrated by National Institute of Metrology P.R.China, MEMS device and textured steel sheet was measured to illustrate the capabilities of the profilometer.

In this work, theory and experiment describe the performance of a surface profile measurement device based on optical heterodyne interferometry are presented. The object and reference beams propagating through the interferometer are obtained by single-pass through an acousto-optic modulator. The diffraction orders 0 and the Doppler-shifted +1 (object and reference beams, respectively) are manipulated to propagate collinearly towards the interferometer output where a fast photodetector is placed to collect the irradiance. The modulated optical signal is Fourier transformed using a data acquisition card and RF communications software. The peak centered at the acousto-optic frequency in the power spectrum is filtered and averaged. The irregularities on the surface of the reflective sample are proportional to the height of this peak. The profile of a reflective blazed grating has been sketched by translating laterally the sample using a nanopositioning system. Experimental results are compared to the measurement done with a scanning electron microscope. There has been found a good agreement between both methods.

In the present paper we describe the holographic interferometric beating to produce dynamic photorefractive moire-like patterns with two or more variation directions. It has been experimentally obtained by the superposition of two sinusoidal gratings with slightly different pitches for each direction of fringe variation obtained. These dynamic moire-like patterns are induced in the volume of the Bi 12 TiO 20 (BTO) crystal sample used as dynamic holographic medium. The Fourier transform profilometry method is applied using two or more moire fringe patterns with different direction of variations, simultaneously or not, projected onto an object surface.

An axis-symmetrical optical laser triangulation system was developed by the authors to measure the inner geometry of long pipes used in the oil industry. It has a special optical configuration able to acquire shape information of the inner geometry of a section of a pipe from a single image frame. A collimated laser beam is pointed to the tip of a 45° conical mirror. The laser light is reflected in such a way that a radial light sheet is formed and intercepts the inner geometry and forms a bright laser line on a section of the inspected pipe. A camera acquires the image of the laser line through a wide angle lens. An odometer-based triggering system is used to shot the camera to acquire a set of equally spaced images at high speed while the device is moved along the pipe’s axis. Image processing is done in real-time (between images acquisitions) thanks to the use of parallel computing technology. The measured geometry is analyzed to identify corrosion damages. The measured geometry and results are graphically presented using virtual reality techniques and devices as 3D glasses and head-mounted displays. The paper describes the measurement principles, calibration strategies, laboratory evaluation of the developed device, as well as, a practical example of a corroded pipe used in an industrial gas production plant.

Confocal microscope has been a powerful tool for three-dimensional profile analysis. Single mode confocal microscope is limited by scanning speed. This paper presents a 3D profilometer prototype of parallel confocal microscope based on DMD (Digital Micromirror Device). In this system the DMD takes the place of Nipkow Disk which is a classical parallel scanning scheme to realize parallel lateral scanning technique. Operated with certain pattern, the DMD generates a virtual pinholes array which separates the light into multi-beams. The key parameters that affect the measurement (pinhole size and the lateral scanning distance) can be configured conveniently by different patterns sent to DMD chip. To avoid disturbance between two virtual pinholes working at the same time, a scanning strategy is adopted. Depth response curve both axial and abaxial were extract. Measurement experiments have been carried out on silicon structured sample, and axial resolution of 55nm is achieved.

A common-path interferometric profilometer using a Savart plate as a lateral shearer has been successfully tested under harsh environmental conditions to measure the shape of a surface, detecting defects and characterizing surface properties. The whole profile is obtained from a single image and its depth sensitivity is easily scalable, making this technique suitable for many different applications. Although this system has been successfully used for surface inspection and defect detection, some behaviors cannot be explained by the usual simple model for fringe formation, which, amongst other things, considers normal incidence of the incoming rays into the Savart plate. These deviations from the ideal case are more noticeable for high resolutions from short distances. This paper studies the formation of the fringe pattern, which is crucial for understanding the behavior of the system and proper calibration.

In micro manufacturing (MEMS, polymer hot-embossing, polymer roll-to-roll imprint, etc.) precise micro and nano-sized features are distributed over large areas. In order to inspect for defects or employ statistical process control on micromanufactured parts, metrological instruments must collect data with submicron resolution at a rate fast enough to keep up with the pace of production. Commercial inspection instruments fall short on meeting these challenging demands. In this paper we detail the design, implementation, and results of an optical system build to provide real-time inspection for transparent polymer microfluidic devices. Our current hardware demonstrates 0.5 micron lateral resolution with 1 micron vertical resolution at a rate of 640,000 voxels per second. Furthermore we demonstrate the ability to measure vertical sidewalls. The tilted orientation of our camera system provides access to these typically hidden or eclipsed areas. We conclude the paper with a direct comparison of our instrument's capabilities against a white light interferometer and laser scanning profilometer. The data demonstrates the difference between the instruments' lateral and vertical resolution, data acquisition rate, and vertical sidewall measurement capabilities.

The nature of the surface topography significantly influences its functional performances, such as the lubrication, wear, friction, corrosion, fatigue, et al. Therefore, the need for accurate surface metrology is becoming more and more important. This paper introduces a high-precision 3D profilometer for surface metrology with the characteristic of high resolution, long measure range and low cost. The 3D profilometer consists of several parts: the micro-displacement sensor based on linear phase grating interference, the X-Y 2D platform, the column, the optoelectronic detector and its signal processing circuit, the computer and data processing software. The precise linear motion of the displacement sensor is implemented by parallel springs and its high precise displacement measurement is realized by sine phase diffraction grating. The theoretical vertical resolution of the micro-displacement sensor may achieve 0.12 nm, and the actual measuring range of the displacement sensor is 2mm, which can reach 6mm by replacing the measuring lever. The 2D platform is driven by servo motor and the double diffraction grating metrology system is adopted to measure the position of the platform. The resolution step displacement of the 2D platform is 0.2um.

In this paper the mechanical model of measuring rod of traditional stylus profilometer is established and the analysis results show that the measuring force is changed with rotation angle of the measuring rod. The impact on profile measurement of unsteady measuring force and the necessity of measuring surface of different materials with different constant measuring force are also discussed. The mechanical relations between the measuring rod and the surface are simplified by the structural change of measuring rod and a gravity center adjustment device. A voice coil motor (VCM) is added into the measuring system to control the measuring force. By adjusting the current in the coil of the VCM in real time, the measuring force can be controlled. With the controllable force, different workpieces can be measured by using different constant measuring force and the measurement results of different workpieces are given.

Optical digital-imaging techniques offer a fast, high-resolution, and wide-range metrology capability for measuring semi-transparent and transparent polymer-based devices during manufacture. This work presents novel instrumentation for in-process statistical control and metrology capable of measuring a complete macroscale part (~25 mm) down to its microscale features (~50 μm). The high speed 2.5D profilometer has generated contour plots with 0.4 μm lateral and 1 μm vertical resolution. The instrument has an estimated data rate of 8 million 3D data points per second, approximately 270 times faster than conventional white light interferometry.

In the last years the investigations in the area of optics of Bessel and their associated conical beams are being shifted from the domain of scientific research to the one of practical applications. This is appreciably due to new potentialities of the practical use of these light fields, which are not realizable in the framework of traditional optics of Gaussian beams. The spatio-angular properties of conical light beams are optimal to control the form and quality of surfaces close to cylindrical and conical ones. This is related to the fact that a conical light beam enables one to realize the longitudinally uniform illumination at a certain angle. The grazing-incidence geometry of illumination permits one to significantly reduce the speckle noise in the field reflected and to extract, thereby, information on the macroscopic shape of the surfaces. In this work we develop two optical profilometers intended for non-destructive testing of objects having the form close to the cylindrical one. In particular, a new scheme of vibration-proof laser profilometer based on using the superposition of two conical beams is proposed. A laboratory optical setup of the profilometer is designed. The developed device includes two ring diaphragm as a basic element for crating two conical light beams. One of these beams serves as a reference beam and the second - as an object one. As a result, the independent reference arm has been removed and a single-arm scheme has been realized. The conical beams are spatially separated so that one beam illuminates the cylindrical surface and another beam is freely propagates. Due to a single-arm configuration, this profilometer is noted for a high mechanical stability. The experimental testing of the laboratory setup has confirmed this property of the device. The methods of eliminating the systematic errors and the misalignment aberrations are developed. The conical beam - based profilometer applies to controlling various cylindrical and conical samples including the roller bearings. It is shown that the single-arm profilometer is suitable for testing the roller bearings, because it is vibration-proof and also provides an enough measuring accuracy. Besides, this type of profilometers is not time consuming, which allows the online control of bearings.

The number of devices and methods for non-contact solid surface measurement and mapping is growing. Nevertheless contact devices still have value in measuring roughness, waviness and shape measurement. Modern contact devices measure without any negative influence to the surface and are even used for optical and other sensitive surfaces. Some examples are mentioned in the article below.

A compact fringe projection profilometer is recently developed for profiling small objects. A handphone-size microprojector with LED illumination is assembled into our system to minimize the size optical 3D sensor. In our compact 3D shape measurement system, the approaches of phase shifting, temporal phase unwrapping and modified least-squares calibration are utilized to achieve high precision and an easy procedure. The portable system allows for easy and convenient 3D profile measurement to meet the requirements under diverse application conditions, such as profiling small turbine blades in aerospace workshop. Experimental results testify to the robust and reliable performance of this LED micro-projector based FPP system.

Focus detection method is one of the primary non-contact measurement methods of surface topography. However, the measuring range of traditional focus detection method is limited because the volume motor is adopted in the focus servo system. The traditional method has inevitable non-linear error and other measurement error caused by the volume motor. This paper presents a new non-contact profilometer based on an improved Foucault focus detection method. The non-contact profilometer is a closed loop control system, which changes the traditional moving volume motor scanning system into the moving platform scanning system. Without adopting volume motor, the non-contact profilometer has large measuring range, high resolution and more measurement parameters. When the surface of workpiece is measured, the undulation of microcosmic surface topography leads to the focusing error signal continuously. According to the focusing error signal, the computer controls the piezoelectric actuator and the Z direction motor to drive the platform to move vertically, which ensures that the focus is always on the surface of workpiece and the focusing error signal is zero. The diffraction grating displacement sensor measures the vertical displacement of the workpiece, then the displacement signals is processed by the characterization software as the results of the measurement. The non-contact profilometer can measure roughness, waviness, shape error of different curved surfaces precisely.

The next generation of ground-based extremely large telescopes of 30 m to 100 m aperture calls for the manufacture of several hundred sub-aperture segments of 1 m to 2 m diameter. Each annulus of the overall aperture is formed from separate elements of the appropriate off-axis conic section (usually a paraboloid). Manufacture of these segments requires a systematic approach to in- and post-process metrology for all stages of manufacture, including the grinding stage, despite the fact that the resulting ground surface is generally not amenable to optically reflective measurement techniques. To address the need for measurements on such 1 m to 2 m telescope segments, a swing arm profilometer has been constructed as part of a collaborative project between University College London (UCL) and the UK National Physical Laboratory (NPL). The current swing-arm profilometer is intended as a proof-of-concept device and has the capability to measure concave and convex surfaces of up to 1 m in diameter with a minimum radius of curvature of 1.75 m for concave and 1.25 m for convex surfaces. Results will be traceable to national length standards. Principles of the swing-arm instrument will be described together with the mechanics of the arm design, its bearing and adjustment arrangements and surface probe options. We assess the performance requirements of 20 nm RMS form measurement accuracy in the context of the tolerances of the selected profilometer components, the error budget, and preliminary system measurements. Initial results are presented with a Solartron linear encoder. We also plan to mount optical sensors on the end of the arm as an alternative to traditional contact probes. Initially these will include an Arden AWS-50 wavefront curvature sensor and a Fisba μ-phase interferometer. The method of attachment of the Arden AWS-50 is outlined. The swing arm profilometer is to be located at a specialised facility, the OPtiC Technium, Denbigh, North Wales, where it will form part of a tool-kit of metrology and polishing devices for researching the production of large aspheric surfaces.

The profilometer for on-line and non-contact measurement of the fine optical surfaces is described in this paper, which works on the principle of the differential interferometry with coaxial interference arms. The optical part of that is isolated and easy to install on the machine tools or the measuring machineries ea. This profilometer has excellent resistance to disturbance, especially to mechanical vibration, when the amplitude of vibration is about 300nm. So it still can be used to measure the micro-profile with sub-nanometer resolution. The vertical resolution of the profilometer is better than 0.05 nm rms. and need not add any condition or pretreatment

This paper presents a controlled-force laser interference surface measuring system, which can achieve high-precision surface profile measurements in a large range. The key technology of the system is the controlled-force laser interference displacement sensor based on Michelson interference principle. The system operates in micro-force by the voice coil motor (VCM) which alters the measuring contact force in real time and reduces the scratches caused by the stylus tip on the surfaces of the tested samples. The position of the stylus can also be changed, which avoids the damage of the system when the stylus scans across high steps or deep grooves. The optical and mechanical principles of the displacement sensor, the realization method of controllable measuring force and photoelectric signal processing are discussed in this paper. Additionally, this paper introduces the two-dimensional stage used for high precision scanner, and presents primitive experimental results.

We have developed an Ultrahigh-Accurate 3-D Profilometer (UA3P), which, using a new, in-house-developed atomic force probe, has an accuracy of 10 nm. It is capable of measuring corners as small as 2 micro meter in radius and can cover an area up to 400 x 400 x 90 (mm), providing a powerful boost to nano-level processing. A commercial product was introduced in 1994. Examples of the key components made possible by this technology include aspherical lenses (used for a Blu-ray Disc device, a next-generation DVD, digital cameras, cellular phones, optical communications), free form lenses (used for frennel lens common to CD and DVD, laser printer lens, multi focus glass lens, cubic phase plate to extend depth of focus), gigabit semiconductor wafers, hard discs, air conditioner scroll vanes, DVC cylinders. The premiere ultra high-precision three-dimensional profilometer delivers superb performance using a variety of micro-measurements for a wide range of applications.

Traditional interferometric profilemeter suffers from phase ambiguity problem and sensitivity to environmental disturbance, thus preventing their applications for on-line surface inspections. We propose a new method to obtain the object surface's two-dimensional profile in a single shot using a dispersive interferometer. An air-spaced Fabry-Perot etalon was applied in order to decompose the light from the broadband source into discrete monochromatic constituents with equal wavelength interval. A blazed grating is implemented to effectively separate the interferograms of difference wavelength. As a result, the interference patterns of different wavelengths distributed separately on the CCD camera. By analyzing these patterns one can get the configuration of the original surface. A one-dimensional profiling experiment is carried out to test a surface with steps and the mean error of the result is below 0.2μm.

This study employed white-light interferometry to measure the three-dimensional (3D) profiles, roughness, and dimensions of brightness-enhanced films (BEFs) that exhibited roof-shaped profiles with large-bevel inclines that could not be successfully measured by conventional optical inspection. A scanning white-light interferometer (SWLI) was used to obtain image information from both the symmetrical sides of inclines in the BEFs. A feasible structure with an angle-tuning mechanism was also introduced to enable the scanning white-light interferometer to rotate the angle of vision according to the bevel angle of the incline in the BEF. Further, the profiles of the BEFs could be reconstructed successfully through a series of image processing techniques. Now, the allowable bevel angle of the inclines in the BEF is not greater than 45°. The experimental results confirmed that this approach can successfully measure the 3D profiles of large-bevel inclines of microstructures as well as the roughness and dimensions of BEFs.

One of the more challenging applications of optical metrology is real-time dimensional control and surface inspection in industrial applications, where strong requirements of cost, setup and applicability in adverse environments, greatly limit the number of applicable technologies. This paper shows an optic profilometer developed specifically for this purpose. This device, based on Conoscopic holography, is able to obtain a distance profile of a target in a single-axis scan; works from long distances and still keeps good resolution with a very easy and reliable setup. The first part of the paper introduces the working principles of Conoscopic holography and shows the sensor set-up. Necessary algorithms for obtaining the distance information are presented and the whole process is illustrated with real captures of test objects. The second part focuses on a real example of this technology applied in an on-line inspection system in steel continuous casting funded by the European Committee for Steel and Carbon, and which is currently working in Aceralia LDA steelmaking factory in Asturias (Spain). The system is placed in the process line and performs on-line detection of surface defects over hot steel slabs from a distance of 1200 mm. 100% of the production can be inspected without interfering with the process and without adding any delay.

A NIST traceable phase1 shift standard has been designed, fabricated, and tested on three phase shift measurement tools using different wavelengths. By using the fundamentals of NIST traceable step height, quartz index, and the understanding of the illumination optics of the Lasertec phase metrology tool, a phase standard has been created which can be used to calibrate Lasertec phase metrology tools. The pattern that is used is compatible with the recommended best practices for calibrating and measuring step heights and phase on the Lasertec tools. The mask is made with multiple depths. The three mask depths allow for the mask to be calibrated to three NIST traceable depth heights. This was done using the FEI SNP XT depth metrology tool. Since the mask format is mask based (6x250 Cr on quartz), it can be easily used on mask manufacturing metrology systems. The depths are targeted at the 180-degree phase shift for 157nm, 193nm, and 248nm lithography. The mask can be used to set targets and check the linearity of the phase metrology tools. The patterns are compatible with AFM and Profilometer depth metrology tools as well as multiple Lasertec spot sizes and shearing distances. The quartz depths are fabricated using a wet quartz etch process. The wet etch minimizes the quartz roughness and removes that error source from the metrology. The pattern is also arrayed so that multiple sites can be used to confirm the metrology and the prime measurement site could be changed if there was a suspicion of pattern damage or contamination.

Fiber connectors are key passive components widely used in today's optical communications. In this paper, a Carre-algorithm-based phase-shifting profilometer is used to measure the endface of a fiber connector. With the aid of the reconstructed three-dimensional topographical information of the surface, we can obtain some of its physical parameters.

We propose an optical method to evaluate deterioration mechanisms affecting cultural heritage materials. The method is based on a phase element, which forms interference fringes on the object. The surface topography is obtained by a phase shifting technique.

This paper describes the experimental setup, test procedure and data-processing of the new profilometer based on an optical fiber displacement sensor. For performing test procedure this sensor is mounted on a high precision linear stage. The optical fiber probe consists of a bundle of optical fibers in a a star configuration. The linear displacement system is mounted on hydrostatic bearings, the guideways are made from zerodur with a planeity better than 0,25 micrometers . The stage is moved by a friction drive over a distance of 220 mm and controlled by an optical encoder with a resolution of 4 nm. The surface profile of a piece from standard polished stainless steel measured by our profilometer is presented.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper describes an high precision in-process optical surface profilometer system. The measurement principle of the profilometer is based on phase comparison of optical heterodyne signals. Disturbance from environment vibration and mechanical instability of the interferometer was effectively eliminated by using optical and electronic common-mode rejection techniques. Measuring light can be automatically focused on the surface by a moving-coil lens during the sample scanning process. The size of the profilometer is small since a laser diode is used instead of a big He-Ne laser. This profilometer is suitable for use on machine. The height sensitivity is of the order of 1 nm and lateral resolution is 0.8 micrometers .© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A high resolution non-contact optical sensor for surface roughness has been developed. The principle of the sensor is based on the dynamic focusing in combination with astigmatic method, a popular focus-error detection approach. The measuring principle of the method and the optical system arrangement are described in detail firstly. Then, a mathematical model of the system based on Fresnel diffraction theory is derived. According to the model, a plot of the focus error signal (FES) versus the misfocusing is easily got. The effect of various system parameters on the FES is discussed, and this is very useful for system optimization. Besides, results of numerical calculation, namely optical field distributions on the quadrant photodetector surface at different misfocusing, are presented.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

White-light Vertical Scanning Interferometry (VSI) is a well-established technique for retrieving the three-dimensional shape of small objects. It has the advantage of non-contact measurement with absolute depth resolution at nanometer level repeatability. The technique has proven to be very effective in measurements of microstructures such as MEMS devices, surface texture, roughness, etc. However, it can only measure areas as big as the field of view of the instrument, usually not more than 15 mm, or a stitching algorithm must be applied. This slows down the measurements and often can be a source of errors. In this paper we present a modification of the technique permitting measurements at higher speeds while retaining the overall accuracy and repeatability of VSI. In the presented method the object is scanned laterally in front of an instrument with a tilted coherence plane such that the data is acquired continuously eliminating the need for stitching for elongated objects. One of the advantages of the proposed system is possibility of faster scanning speed with the use of a high speed CCD arrays. In the paper we present the principle of the method along with an experimental confirmation.

In this paper microscopic interferometry is used for 2D and 3D profiling of micromechanical devices deformation and, is extended to allow vibration spectra measurements on a few microns wide microdevices. This is obtained by adding an apertured photomultiplier with suitable signal processing and subnanometric piezoelectric excitation. Resonant frequencies are detected both from vibrations-induced fringes contrast variations and by using a homemade wide bandwidth (10 MHz) double lock-in amplifier. This allows vibration measurements up to several MHz with a spatial resolution down to 1.25 micrometer and a detection limit of vibrations amplitudes in the 0.2 - 1 nm range. Furthermore the system allows a direct visualization of the whole vibration modes and can be applied for automated bulge testing of membranes. System operation for 3D profilometry, vibrometry and bulge testing is demonstrated on Cr cantilever microbeams and microbridges fabricated by surface micromachining and on membranes. Capabilities of the system for large vibration amplitudes measurements and its extension for on-wafer resonant frequencies measurements by using optical excitation are discussed.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We present an instrument that uses a novel technique to render topographical maps of microscopic reflecting surfaces in which depth resolution can be an order of magnitude or more better than the lateral resolution of the confocal microscope. In a confocal scanning reflected-light microscope, the illumination light coming out of the objective is a cone of light with its axis parallel to the optical axis and focused into a diffraction-limited spot. If the specimen is smooth within the size of the spot, then the laws of reflection apply. When the reflecting surface is perpendicular to the optical axis, the reflected light is a cone that coincides with the illumination light. If the reflecting surface is not perpendicular to the optical axis, the axis of the reflected cone of light is at an angle with respect to the optical axis equal to twice the tilt angle of the surface and oriented in the direction of the surface tilt. Because of this tilt, a portion of the back focal plane (BFP) of the objective does not receive any of the reflected light, while in the diametrically opposite side, the aperture stop blocks part of the reflected light. For a given illumination profile, the distribution of light on the BFP is determined by the tilt and orientation angles of the reflecting surface and thus can be used to recover these angles for each pixel in the specimen. These angles are then used to render a topographical map of the reflecting surface.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this work, the authors present a prototype of an adaptive whole-field profilometer based on grating projection. Adaptiveness is achieved by performing the projection of the gratings by an LCD projector. The main features of the hardware and software components of the system are detailed. Profile evaluation, system calibration and certification are also covered. The performances of the instrument, as it emerges from the experimental tests carried out on the prototype version of the system, are discussed.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper describes a heterodyne common path differential phase interferometer which is resistant to the thermally and microphonically induced measurement errors of non-common path systems. The system utilizes a single probe beam which is focused onto the sample and then imaged onto the detector plane. Differentiation in any direction can be performed by altering the positions of the detectors. A theoretical derivation of the system transfer function is presented, the results from which show excellent agreement with experimental measurements. Initial theoretical results of the recovery of a sample profile from its differential profile are presented. Finally, a simplified and more stable differential system is introduced.

In this paper an optical profilometer based on the principle of heterodyne interferometry has been developed. A new optical path design with a two-parallel-path is presented. This instrument will be insensitive to the vibration the air turbulence and no high precision reference surface is needed. The measurement results show that the vertical resolution is better than mm and the lateral resolution is less than 1 I. L m. Based on this design we also analyze its potential errors such as the error caused by the distance between two parallel optical paths that caused by the phase detection system and those casued by the optical design and others. The stability and the repeatability of the instrument are also evaluated.

Single point diamond turning technology has allowed the manufacture of highly aspheric optics that were unimaginable just a few years ago. Testing these optics is typically either expensive (i.e., null lens systems), destructive (contacting stylus profilers), or slow (existing optical profilers). We describe a noncontacting surface profilometer with 5 micrometers lateral spatial resolution and sub-angstrom height resolution. The instrument is configured as a polarizing interferometer that operates at near zero path difference and uses a visible laser diode as a light source. The instrument incorporates an autofocussing mechanism that allows high resolution profilometry over a vertical range of +/- 1 mm. The system bandwidth of 200 kHz allows for very fast profiling (87 cm/sec) without loss of resolution. The sensor head is very compact (6 X 6 X 10 cm) and all the processing electronics are contained on a single PC-compatible card. The instrument's autofocussing feature, high speed capability and compact size make it ideally suited for inprocess and final acceptance testing of steep aspheric optics. We present data that demonstrates our ability to accurately measure the macroscopic and microscopic features of single point diamond turned aspheric optics typically used in high resolution x-ray lithography systems.

In this paper the method for the electro—optical information processing in the heterodyne profilometer wehave made is described. It is based on optical heterodyne interferometry and phase detection technique. Heightvariations is less than mm and lateral resolution is less than 2 pm. More than ten parameters about surface roughness could be calculated and real profile of measured surface could be obtained. 1. INTRODUCTIONSurface roughness is an important factor due to it influences on production of precision instruments. Themeasurement of surface profile is increasingly important aspect in modern production. How to measure it,specially for extremely smooth surfaces, is very important. During recent years, several methods for measuringsurface profile, specially for extremely surfaces have been presented. One of them is optical heterodyneinterometry . The following article describes an heterodyne interferometry system and electro— optical informa- tion processing which is based on phase detection technique. By this way, the phase difference (ACT))

A method of calibrating profilometer transmission characteristics with a heterodyne interferometer is described. This method has the advantages of high precision, setting no strict demands on the environment and being efficient. The work range of the calibrating system is from 0.15 micrometers to 40 micrometers for Ra. The uncertainty of the calibrating is +/- 1%, and the frequency is between 1 Hz and 180 Hz.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An electroless nickel plated over aluminum mirror was tested for BRDF and surface profiles at two stages: First, after a standard polish for optical figure, and second, after a `super finishing process' which is designed to minimize optical scatter. BRDF measurements corresponding to spatial frequency range between .0016 micrometers -1 to 1 micrometers -1 were obtained using 0.633 micrometers , 1.06 micrometers , 3.39 micrometers and 10.6 micrometers lasers. The conversion formula used to derive PSD2D from BRDF data is based on the Rayleigh-Rice vector theory. Measurements of the same spots by an optical profilometer (WYKO TOPO-2D) with several objectives were used to cover similar spatial frequency limits. The surface finish statistics, extracted from the profile data, was processed to produce PSD1D. Then, composite PSD1d were fitted to an analytic function for PSD1D using the K- correlation model approach. The derived PSD2D from profile data was readily determined from the A,B,C coefficients associated with the K-correlation model. The derived PSD2D from BRDF and profile measurements were compared to quantify the difference in surface finish statistics between the standard polished mirror and the same mirror after `super finishing.' Good correlation is found for the standard polished surface. This corroborates the `topographic scatter' behavior for the clean, standard polished nickel surface which promise useful interpolation of BRDF values to wavelengths at which direct BRDF data is unavailable. Correlation for the `super finished' surface is worse, probably due to unplanned surface contamination between tests.

We present a novel non-contact holographic optical profilometer, which is light weight, compact and relatively simpler. Computer simulation results reveal that surface measurements with sub-micron resolution are possible both in the horizontal and vertical directions.

An optical heterodyne system for the measurement of profile and roughness has been developed. Several improved techniques are employed. The optical system was designed with entire common path. The effect of sample vibration and the thermal drift could be eliminated. A modified objective was used to perform respectively the measurement beam and the reference beam. The detected signals were processed with phase comparison technique to give a high accuracy. The optical system can be developed to an accessory of the Zeeman laser interferometers.