Fiber deflection probe for small hole metrology

This paper presents the development of a new probing method for coordinate measuring machines (CMM) to inspect the diameter and form of small holes. The technique, referred to as fiber deflection probing (FDP), can be used for holes of approximately 100 μm nominal diameter. The expanded uncertainty obtained using this method is 0.07 μm (k = 2) on diameter. The probing system consists of a transversely illuminated fiber (with a ball mounted on the end) whose shadows are imaged using a camera. We can infer the deflection of the probe from the motion of the image seen by the camera, and we infer the position of the measured surface by adding the fiber deflection along x- and y-directions to the machine scale readings. The advantage of this technique is the large aspect ratio attainable (5 mm deep for a 100 μm diameter hole). Also, by utilizing the fiber as a cylindrical lens, we obtain sharp crisp images of the fiber position, thus enabling high resolution for measured probe deflection. Another potential advantage of the probe is that it exerts an exceptionally low force (ranging from a few micronewtons down to hundreds of nanonewtons). Furthermore, the probe is relatively robust, capable of surviving more than 1 mm over-travel, and the probe should be inexpensive to replace if it is broken. In this paper, we describe the measurement principle and provide an analysis of the imaging process. Subsequently, we discuss data obtained from characterization and validation experiments. Finally, we demonstrate the utility of this technique for small hole metrology by measuring the internal geometry of a 129 μm diameter fiber ferrule and conclude with an uncertainty budget.     

Producing gear teeth with high form accuracy and fine surface finish using water-lubricated chemical reactions

A new method was investigated for high-accuracy fine finishing of gear teeth surfaces using a water-lubricated tribo-chemical technique. A pair of shaved gears with rather low surface roughness was rotated in water lubricant for 30 min so that the gear tooth surface contacting the mating tooth was ‘worn’ to a mirror surface and ideal tooth profile, due to the mechano-chemical mild erosion of the contact area. The wear rate was 2.0 μm per 20,000 meshings, corresponding to a wear of one atomic radius thickness per meshing. Oxidation of the steel surface by water molecules is proposed as the dominant wear process. Operation noise from the gear pair rotation was drastically reduced to lower than about 10–15 dB compared to conventionally machined gear surfaces (30 dB in average), as a result of the wear of the tooth surface to form a best-fit profile. The noise increased with further processing of the gear pair. Thus, there is an appropriate number of rotations for suitable surface wear treatment. This new and simple procedure for surface treatment assures saving in energy, and does not require expensive honing techniques or high-accuracy grinding tools.The wear mechanisms used in this process are discussed along with the application of the technique to other processes for precision finishing.     

A non-intrusive probe for bubble profile and velocity measurement in horizontal slug flows

A new technique was developed for measuring the profile and mean velocity of elongated bubbles in horizontal air–water slug flows. It is based on the capacitance between two thin electrodes mounted on the external surface of a dielectric pipe, and has advantages in relation to the traditional parallel wire technique, since it is not intrusive, the presence of impurities in the liquid phase has no influence on the probe response, and it is applicable to very low electrical conductivity liquids, such as oils and deionized water. Tests were performed in an experimental facility with a 5 m long, 34 mm internal diameter Plexiglas pipeline. The elongated bubble mean velocity was determined by using a cross correlation technique applied to the signals coming from two identical capacitance probes, mounted 50 mm distant from each other. The results were compared with an empirical correlation from the literature. Discordance was observed only for flows near the flow pattern transition regions in the flow pattern map.     

Simultaneous interferometric measurement of the absolute thickness and surface shape of a transparent plate using wavelength tuning Fourier analysis and phase shifting

The absolute optical thickness and surface shape of optical devices are considered as the fundamental characteristics when designing optical equipment. The thickness and surface shape should be measured simultaneously to reduce cost. In this research, the absolute optical thickness and surface shape of a 6–mm-thick fused silica transparent plate of diameter 100 mm was measured simultaneously by a three-surface Fizeau interferometer. A measurement method combining the wavelength tuning Fourier and phase shifting technique was proposed. The absolute optical thickness that corresponds to the group refractive index was determined by wavelength tuning Fourier analysis. At the beginning and end of the wavelength tuning, the fractional phases of the interference fringes were measured by the phase shifting technique and optical thickness deviations with respect to the ordinary refractive index and surface shape were determined. These two kinds of optical thicknesses were synthesized using the Sellmeier equation for the refractive index of fused silica glass, and the least square fitting method was used to determine the final absolute optical thickness distribution. The experimental results indicate that the all the measurement uncertainties for the absolute optical thickness and surface shape were approximately 3 nm and 35 nm, respectively.     

Recrystallization in subsurface zone seen by positron annihilation

The paper presents studies of the defect distribution, detected by the positron annihilation method in the subsurface zone (SZ) of copper samples after dry sliding wear. It takes advantage of a new experimental technique based on scanning of the positron implantation profile. It allowed us to detect the defect profile in copper to the depth of 200 μm in a nondestructive way and study isochronal annealing behavior of this profile. We determined that annealing induces a recrystallization process which runs faster close to the surface than in deeper regions. After sliding, the complete recrystallization of the substructure takes place at temperature c.a. 600 °C. Some changes in the defect structure begin at temperature c.a. 300 °C. The comparison of the temperature depth profile calculated theoretically with experimental results indicates that the role of the temperature rise in the asperity regions during sliding is negligible in the SZ constitution in the case studied.     

数字全息干涉测量的时域和复数空间处理法

描写了一种新颖的在复数域处理数字全息干涉的方法.不同于一般的直接处理相位信息的数字相位相减法,本文提出的方法处理的是可以直接得出相位的复数信号.基于这种概念,本文提出了两种时域相位提取的算法.在这两种算法中,CCD相机感光原件的每一个像素做为一个新的独立的传感器,然后每个像素的复数信号作为时间的函数被测量和处理.这两种算法被应用于有台阶的物体的形貌检测,试验的结果证明,本文提出的算法优越于现在的数字全息通用的算法.     

Microtopographic analysis of turned surfaces by model-based scatterometry

Turned surface profiles can be divided into a periodic and a random component. The periodic component is a function of the tool shape and the feed rate. The random component is caused by machine vibrations. To monitor the turning process, the periodic component is the essential global microtopographic feature which reacts sensitively to tool wear and tool scars. A measuring method evaluating the periodic component of turned surfaces is developed based upon the model-based scatterometry. Using an optimized scattering geometry, the model-based scatterometry leads to an intensified mapping of the microtopographic surface features in the angular distribution of scattered light. The profile parameters measured with the introduced scattering technique agree well with the values obtained by stylus measurements. Hence, in the range of precision engineering (R_a≤1.5 μm) the mean profile of the dominant periodic component can be measured optically without scanning and without resorting to comparator standards.     

Evaluation on 3D micro-ground profile accuracy of micro-pyramid-structured Si surface using an adaptive-orientation WLI measurement

According to the aperture of the objectives, surfaces with steep topographies greater than approximate 25° are difficult or unable to measure with white light interferometry. Hence, an adaptive-orientation measurement is proposed by adjusting the incidence angle from 51° to 21°. In this study, a micro-grinding with #3000 diamond wheel V-tip was employed to fabricate the micro-pyramid-structured Si surface with 142 μm in depth and 38 nm in surface roughness. The objective is to evaluate the micro-profile accuracy of micro-ground Si surface. First, the four micro-ground surfaces of micro-pyramid-structured surface were measured along the adaptive orientation with an incidence angle, respectively; then iterative closest point (ICP) matching was used to reconstruct the whole micro-ground surface with four adaptive-orientation measured point clouds; finally, 3D reconstruction error and characterized profile error were investigated. It is shown that the ICP matching with denoising and finishing is valid to register four adaptive-orientation measured point clouds for reconstructing an integrated micro-ground surface. Moreover, a decrease in incidence angle to measured surfaces leads to a decrease in 3D reconstruction error, an increase in valid top-topographic point number and a decrease in characterized profile error. It is confirmed that the adaptive-orientation measurement with 21° incidence angle may enhance 3D reconstruction accuracy by about 35%, valid top-topographic point number by about 3 times and characterized profile accuracy by about 38% against the traditional measurement, respectively. The micro-ground form error of 5.5 μm and the characterized profile error of 6.0 μm may be achieved, respectively, thus the micro-grinding is valid for the precision micro-fabrication of micro-structured surface.     

Measurement and compensation of error motions of a diamond turning machine

This paper describes the measurement and compensation of error motions of a diamond turning machine for nanofabrication of large sinusoidal metrology grids. The diamond turning machine has a T-base design, which consists of a spindle with its rotation axis along the Z-direction and a cross-slide with its movement direction along the X-direction. A fast-tool-servo (FTS) unit is mounted on the X-slide to generate sinusoidal microstructures on a flat workpiece surface mounted on the spindle. The error motions of the X-slide and the spindle, which introduce Z-directional profile errors (out-of-flatness) on the grid surface, are measured and compensated. The out-of-straightness of the X-slide is measured to be approximately 60 nm over a travel of 80 mm by using the reversal method. It is also confirmed that the out-of-straightness of the X-slide has a 10-nm periodic component with a period of 11 mm corresponding to the diameter of the needles used in the roller bearing of the X-slide. The angular motion of the spindle is measured to be approximately 0.3″ by using an autocollimator, which can cause a 73-nm out-of-flatness over a workpiece 100 mm in diameter. The axial motion of the spindle is measured to be approximately 5 nm, which is the smallest error motion. The out-of-flatness of the workpiece is reduced from 0.27 to 0.12 μm through compensating for the error motions by utilizing the FTS unit based on the measurement results of error motions.     

Structure determination at the atomic level from dynamical electron diffraction data under systematic row conditions.

We discuss a method to obtain structural information on crystals at the atomic level in high-resolution transmission electron microscopy from dynamical diffraction data under systematic row conditions. Working at a fixed incident energy and within an N-beam approximation, data is required at a well defined set of N incident beam orientations to determine the scattering matrix, one orientation for each column in the matrix. At each orientation the corresponding column of the scattering-matrix is obtained by Fourier transformation of the exit surface wave function. Thus, in addition to each exit surface image, we must recover the phase of the wave function for that orientation in the image plane. We show that retrieval of the phase using algorithms based on conservation of flux, which assume continuity of the phase, can yield incorrect solutions for the phase. This is because singularities can occur in the phase of the wave field at points where the intensity is zero, which can lead to edge dislocations in the phase. We demonstrate, using a model example, how these edge dislocations arise. We will show that phase retrieval from a through focal series of measurements or using the Gerchberg-Saxton algorithm (starting from measurements of an image and the corresponding diffraction pattern), correctly retrieves the phase and hence the exit surface wave function for all the orientations required to obtain the scattering-matrix. The dynamical (multiple) scattering can then be inverted to uniquely obtain the projected potential.     

Manufacturing process of copper microgrooves utilizing a novel optical fiber-based laser-induced etching technique

A new approach for the fabrication of copper microgrooves with near triangular cross-sectional profile is introduced. For manufacturing the microgrooves, a laser-induced thermochemical etching technique based on an optical fiber as an optical waveguide and machining tool is proposed, which significantly reduced the complexity of a conventional laser etching set up. It is explained that the possible problem of fiber damage during laser etching with the proposed method can be solved by appropriately controlling the gap between the sample surface and fiber tip. The fabrication of copper microgrooves with 100 ∼ 300 μm in depth and 100 ∼ 150 μm in width is accomplished with the proposed technique. The grooves fabricated in the optimal process condition have smooth surfaces and clear edge. The angle of triangular groove is measured to be in the range of 30 ∼ 50 degree and the aspect ratio of grooves is about 1 ∼ 2. The overall etching results such as etch width, depth, and aspect ratio variation are reported in detail with respect to process variables.     

Application of ultrasonic Doppler velocimetry to molten glass by using broadband phase difference method

An ultrasonic velocity profile (UVP) measurement in high temperature molten glass was presented using buffer rod technique. A ceramic buffer rod was used to transmit ultrasound into molten glass. The rod had a taper shape and porous cladding to suppress trailing echo, which is the spurious echo in the buffer rod measurement. The broadband signal processing method was presented to improve noise tolerance in velocity estimation. This method is based on the phase difference method, which is originally proposed as a narrowband method. Measurable distance of the UVP measurement was investigated combining the buffer rod and the broadband signal processing method. Experiment was conducted at the temperature from 1000 °C to 1200 °C. As a preliminary test, motion tracking in molten glass was successfully demonstrated.     

3D characterisation of tool wear whilst diamond turning silicon

Nanometrically smooth infrared silicon optics can be manufactured by the diamond turning process. Due to its relatively low density, silicon is an ideal optical material for weight sensitive infrared (IR) applications. However, rapid diamond tool edge degradation and the effect on the achieved surface have prevented significant exploitation. With the aim of developing a process model to optimise the diamond turning of silicon optics, a series of experimental trials were devised using two ultra-precision diamond turning machines. Single crystal silicon specimens (1 1 1) were repeatedly machined using diamond tools of the same specification until the onset of surface brittle fracture. Two cutting fluids were tested. The cutting forces were monitored and the wear morphology of the tool edge was studied by scanning electron microscopy (SEM).The most significant result showed the performance of one particular tool was consistently superior when compared with other diamond tools of the same specification. This remarkable tool performance resulted in doubling the cutting distance exhibited by the other diamond tools. Another significant result was associated with coolant type. In all cases, tool life was prolonged by as much as 300% by using a specific fluid type.Further testing led to the development of a novel method for assessing the progression of diamond tool wear. In this technique, the diamond tools gradual recession profile is measured by performing a series of plunging cuts. Tool shape changes used in conjunction with flank wear SEM measurements enable the calculation of the volumetric tool wear rate.     

Vibration-resistant interference microscope with assistant focusing for on-machine measurement of surface topography

The interference microscope is a powerful tool for surface topography measurement, but its high sensitivity to vibration hinders its application to on-machine use. To measure surface roughness on a machine for the ultra-precision machining, a vibration-resistant interference microscope (VRIM) with an assistant focusing function is developed. The basic principle of VRIM is an error-compensated phase-shifting interferometry. An iterative algorithm is presented to calculate the surface phase with the phase shift amounts as unknown variables, where the phase shift amounts are calculated and compensated with least-squares method. A narrow bandwidth illumination is employed to alleviate coherence envelop influence, and a simplified intensity model is established to decouple the variables. Assisting the microscope to find fringe quickly, the focusing is realized by introducing an off-axis thin beam to generate two spots, of which their relative position relates to the defocus. The focusing method is directional and determinant, and has a large range up to 0.3 mm. In the vibration disturbances of 0.2 μm and 0.4 μm amplitudes over 0 Hz to 20 Hz frequency region, the roughness accuracy and repeatability of measuring an ultra-precision machined surface are both up to the sub-nanometer level. The developed instrument is applied to a single-point diamond turning machine and achieves a sub-nanometer accuracy and repeatability.     

High-resolution large-strain measurement of plastically deformed specimen by Fourier phase correlation

The Fourier phase correlation method is applied to position circular marks one by one printed on the specimen before and after deformation in order to measure the large plastic strain. This method is extremely sensitive to the differences between the profile of a mark and noise. Therefore, it detects marks easily even under non-uniform illumination without any processing such as flattening illumination, noise exclusion and boundary enhancement in image transformation into binary codes. In addition, a new method of moving reference images (MRI) to position the observed marks in the sub-pixel range is proposed. The MRI technique introduces the theoretical resolution 1/n (n: number of divisions of one pixel). The MRI method enables the positions of the deformed marks to be determined with a resolution of ±0.1 pixel (standard deviation σ_p is 0.042 pixel). Strain of the tensile specimen can be measured within an error of ±0.0015 (standard deviation σ_ε=0.00055).     

Three-point-support method based on position determination of supports and wafers to eliminate gravity-induced deflection of wafers

The flatness measurement of large and thin wafers is affected greatly by gravity. Inverting method is often used to cancel the effect. However, it is required that the positions of the supports and wafers are perfectly symmetric about the inversion axis. In this study a three-point-support method based on position determination of supports and wafers was proposed. The supporting balls and the wafer were placed in arbitrary positions and their positions were obtained by measurement and fed into the FEM model which was developed to calculate the gravity-induced deflection (GID). The methods to acquire the positions of the supports and the wafer were proposed. The position measurement accuracy of the supports was improved greatly by circle fitting to the profile of the supporting ball. Wafer edge point was obtained accurately as the intersection point between the wafer surface line and the edge profile. The method to measure the wafer thickness using only one displacement sensor on the same equipment was presented. The simulation results were verified by experimental results. The centering device for the wafer and the positioning accuracy requirements of the supports are not needed any more. The effect of the positions of the supports and the wafer was reduced to be less than 1 μm for a 300 mm diameter and 397 μm thickness wafer with GID over 140 μm. This method could also be used for accurate flatness measurement of other large and thin panels.     

Measurement of highly reflective surface shape using wavelength tuning Fizeau interferometer and polynomial window function

In this study, a 5N − 4 phase shifting algorithm comprising a polynomial window function and a discrete Fourier transform is developed to measure interferometrically the surface shape of a silicon wafer, with suppression of the coupling errors between the higher harmonics and the phase shift error. A new polynomial window function is derived on the basis of the characteristic polynomial theory by locating five multiple roots on the characteristic diagram. The characteristics of the 5N − 4 algorithm are estimated with respect to the Fourier representation in the frequency domain. The phase error of the measurements performed using the 5N − 4 algorithm is discussed and compared with those of measurements obtained using other conventional phase shifting algorithms. Finally, the surface shape of a 4-in. silicon wafer is measured using the 5N − 4 algorithm and a wavelength tuning Fizeau interferometer. The accuracy of the measurement is discussed by comparing the amplitudes of the crosstalk noise calculated by other algorithms. The uncertainty of the entire measurement was 34 nm, better than that of any other conventional phase shifting algorithms.     

Pilot tone aided measurements to extend the bandwidth of radio frequency applications

A technique to extend the effective measurement bandwidth of a non-coherent vector receiver is presented. This bandwidth extension technique relies on the use of a pilot signal (known a priori), which is added on the signal of interest and is measured in a single receiver. Compared to other bandwidth extension techniques referred as stitching techniques, the proposed approach avoids error propagation in the measurement bandwidth and simultaneously enables the measurement of signals that do not contain energy in certain spectral bands.The pilot signal is created in digital stages, which tackles to large extent the requirement of the a priori knowledge of this signal. Further, the pilot signal is designed to minimize estimation errors of the proposed technique, providing enhanced performance. It is analytically shown that the error incurred by the proposed method is always lower than the error from the measurement noise.Measurement results show the method functionality with an error in the range of −50 dB of the signal measured. Finally, the usefulness of the proposed technique is illustrated by measuring the input and output of an amplifier with dynamic range in excess of 80 dB over 290 MHz using an 18 MHz bandwidth receiver. This measurement could not have been performed by existing stitching techniques.     

Quantitative measurement of the hardness profile on carbo-nitriding steel by the hole drilling method

The thrust measured during a drilling test is related to the hardness of the material being tested. When the test is performed on a superficially heat-treated specimen, the results do not correspond exactly to the hardness profile obtained by the standard Vickers micro hardness technique.Because of the extreme hardness of the surface tested and the small diameter required to minimise material damage, a drill is more suitable than a milling cutter. The thrust measured during testing thus integrates heterogeneous resistance along the cutting edge of the drill. Consequently, correspondence between the hardness profile and the measured signal is shown to be non-linear. By discretising the thickness drilled, we have developed an algorithm which yields the hardness of each elemental thickness. Results for carbo-nitriding steel are very close to those obtained by the Vickers technique and the accuracy is also very similar for both methods.     

Quantitative phase-amplitude microscopy. III. The effects of noise

We explore the effect of noise on images obtained using quantitative phase‐amplitude microscopy – a new microscopy technique based on the determination of phase from the intensity evolution of propagating radiation. We compare the predictions with experimental results and also propose an approach that allows good‐quality quantitative phase retrieval to be obtained even for very noisy data.