Analysis of the Possibility to Compensate for Selected Tool Setting Errors in the Lens Grinding Process

Fabrication and characterization of lithium metasilicate/disilicate glass ceramics and yttria tetragonal zirconia polycrystals for dental restorations

To determine both the size of a satellite antenna and the thermal deformation of its surface shape, a novel high-accuracy close-range photogrammetric technique is used in this study. The method is also applied to assess the performance of the antenna in orbit. The measurement principle and solution method of close-range photogrammetry were thoroughly investigated, and a detailed measurement test scheme was developed. A thermal deformation measurement of the surface shape of a satellite antenna was then carried out. The results show that the measurement error using close-range photogrammetry was smaller than 0.04 mm, which meets the accuracy requirement. Thanks to the high accuracy, it was discovered that both the surface shape and the rib precision of the satellite antenna deteriorate with decreasing temperature. The accuracy of the surface shape and ribs was lowest when the temperature node was -60 °C. The maximum root mean square errors (RMSEs) reached 0.878 mm and 0.761 mm, respectively. This indicates that the surface shape deformation error of the antenna caused by high and low temperatures is relatively high. However, the requirement for the technical design index (RMSE ≤ 1 mm for the surface shape accuracy of the antenna) is still met. Furthermore, for temperature differences of 40 °C and 80 °C, the measured RMSEs for the surface shape deformation were 0.216 mm and 0.411 mm, respectively. Overall, the technical design indicators (RMSE ≤ 0.3 mm and RMSE ≤ 0.5 mm, respectively) for the surface shape deformation of the antennas are met.

Controlling robotic interventions on small devices creates important challenges on the sensing stage as resolution limitations of noncontact sensors are rapidly reached. The integration of haptic sensors to refine information provided by vision sensors appears as a very promising approach in the development of autonomous robotic systems because it reproduces the multiplicity of sensing sources used by humans. This paper discusses an intelligent multimodal sensor system developed to enhance the haptic control of robotic manipulations of small three-dimensional (3-D) objects. The proposed system combines a 16 /spl times/16 array of force sensing resistor (FSR) elements to refine 3-D shape measurements in selected areas previously monitored with a laser range finder. Using the integrated technologies, the sensor system is able to recognize small-size objects that cannot be accurately differentiated through range measurements and provides an estimate of the objects orientation. Characteristics of the system are demonstrated in the context of a robotic intervention that requires fine objects to be localized and identified for their shape and orientation.

The demand for high-precision hard components and their molds/dies have increased in various industries such as in the optical, automotive, and communication industries, as well as in life and medical sciences. Some difficult-to-machine materials can be reliably machined using deterministic precision cutting processes. On the other hand, hard and brittle materials such as ceramics, carbides, hardened steel of molds, glassy materials, or semiconductor materials have to be machined using precision abrasive technologies with super abrasives of diamond or cBN. However, the machining of high-precision components and their molds/dies by abrasive processes, is much more difficult because of their complex and non-deterministic nature and textured surface. Furthermore, high-energy processes such as laser technology can assist abrasive technologies for ensuring higher precision and efficiency. In this sense, precision grinding and polishing process are primarily used to generate high-quality and functional components usually made of difficult-to-machine materials. The surface quality achievable by precision grinding and polishing processes becomes more important for reducing machining time and costs. This special issue features five research articles – five papers – related to the most recent advances in precision abrasive technology of difficult-to-machine materials. Their subjects cover various abrasive machining processes of grinding, polishing, abrasive flow machining, tooling technology, and laser technologies. We deeply appreciate the careful work of all authors and thank the reviewers for their incisive efforts. We also hope this special issue will trigger further research on abrasive technologies.

The mechanical strength of various silicon wafers with a thickness of 100 µm has been studied, depending on the methods of their preparation and the modes of their subsequent grinding or polishing, including chemical-mechanical (HMP). The plates were loaded using the ring-to-ring method, the magnitude of stresses and deflection under the small ring was determined by the finite element method. For all the samples studied, the profiles and roughness parameters of the plates were obtained by stylus profilometry and atomic force microscopy (AFM) when scanning the surface along the baseline and over the area. A direct correlation was found between the strength of the plates and the characteristic parameters of their surface profile (the average values of the magnitude and period of fluctuations in the height of the irregularities).

Solder joint shape measurement is one of the most challenging technique which is essential for automation of PCB inspection. It is difficult because the surface reflection is specular. Among several kinds of specular shape measurement techniques, deflectometry is suitable to measure the 3D profile of a specular free-form surface because of its high accuracy and short inspection time. In that a pattern displayed on a screen is reflected to be imaged on a image sensor. The surface shape is reconstructed from the distortion of the pattern. The major limitation of deflectometry is its limited measurable slope angle caused by the physical size of the screen. In this paper, we propose a multi-screen deflectometer to increase the measurable slope angle for solder joint measurement. And proper calibration method and shape reconstruction algorithm are developed. This idea is verified by experimental results, in which phase information is successfully extracted from the area which are not normally measurable due to its high curvature surface.

Multi-wavelength digital holography is a very powerful approach for surface shape measurements. It has the advantage of being contact-less, non-intrusive, and yields full-field surface shape data without any requirement for scanning. When dealing with off-axis digital holography and spatial multiplexing of two-wavelength digital holograms, the method becomes real-time, in the sense that the surface shape can be measured at each time instant at which the holograms are recorded. Thus, phase shifting and sequential recording are suppressed. However, due to the roughness of the inspected surface, speckle decorrelation occurs and noise is included in the final data. The noise amount in the data must be investigated in order to define the best processing approach for holograms. This paper proposes the analysis of the standard deviation of noise in surface-shape data from two-wavelength spatially-multiplexed digital holograms. The influence of noise on the measurements of the surface shape is described by an analytical approach. Relationships to quantify the minimum measurable surface height is given by taking into account the experimental parameters of the set-up. These parameters are related to the spatial bandwidths, modulation of holograms, saturation ratio, number of electrons in pixels, readout noise, quantization noise, photon noise, and speckle decorrelation due to roughness. The theoretical modeling is discussed and analysis when considering practical situation for industrial surface shape measurements.

There are several ways in which light may be projected onto a surface so that the shape of the surface can be determined. There appears to be a basic problem with many methods which have been developed because of a lack of reference to the underlying properties of the signals produced. We examine the properties of light which is structured in the form of stripes, also referred to as fringes, and is projected onto a surface to be contoured. Due to interaction between the surface and the structure of the incident light, an observer will see curves in the light structure, these curves clearly displaying the shape of the surface to be imagined even though it is viewed in only two dimensions. A typical observed fringe pattern, is shown. It is also shown that the light structure is phase modulated, and the properties of the resulting signal are investigated. For theoretical compactness the signal is considered to be one dimensional, equivalent to taking a vertical section through the image. This approach is perfectly valid if the image is processed as columns one pixel wide, and the general conclusions may be extended into two dimensions for more complex arrangements of images and processing.

We describe a novel device that can be used as a 2.5D “scanner” for acquiring surface texture and shape. The device consists of a slab of clear elastomer covered with a reflective skin. When an object presses on the skin, the skin distorts to take on the shape of the object's surface. When viewed from behind (through the elastomer slab), the skin appears as a relief replica of the surface. A camera records an image of this relief, using illumination from red, green, and blue light sources at three different positions. A photometric stereo algorithm that is tailored to the device is then used to reconstruct the surface. There is no problem dealing with transparent or specular materials because the skin supplies its own BRDF. Complete information is recorded in a single frame; therefore we can record video of the changing deformation of the skin, and then generate an animation of the changing surface. Our sensor has no moving parts (other than the elastomer slab), uses inexpensive materials, and can be made into a portable device that can be used “in the field” to record surface shape and texture.

Two types of phase-shifting algorithms were developed for simultaneous measurement of the surface and thickness variation of an optical flat. During wavelength tuning, phase-shift nonlinearity can cause a spatially nonuniform error and spatially uniform DC drift error. A 19-sample algorithm was developed that eliminates the effect of the spatially uniform error by expanding the 17-sample algorithm with characteristic polynomial theory. The 19-sample algorithm was then altered to measure the surface shape of the optical flat by rotation of the characteristic diagram. The surface shape and thickness variation were measured with these two algorithms and a wavelength-tuning Fizeau interferometer.

In the use of the three‐dimensional data obtained from a stereo system, laser range finder, and other equipment, merge processing is important. This paper proposes a new merge method for range images, based on the volume‐based technique. In the proposed method, in contrast to the conventional method, the voxels are adaptively segmented according to the curvature of the surface shape to be reconstructed. This helps to represent the geometrical shape efficiently, effectively utilizing the computation resources. In the framework of the proposed merge process, additional features such as color and the laser reflectivity can be added to the three‐dimensional geometrical information, which helps to maintain sharp edges in the texture and to perform rendering and the texture mapping effectively. By examining the consensus for both the geometrical shape and the color in the whole framework, the merge is made robust to noise. In this paper, the system is described first, and then the results of application to several kinds of actual data are presented. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(11): 50–60, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20353

Characterization of deformation and surface shape is an important parameter in quality testing of micro-objects in view of the functionality, reliability, and integrity of the components. Single-wavelength TV holography is widely used for deformation analysis. However, the single-wavelength TV holographic configuration suffers from overcrowding of fringes for large deformation that sets a limitation due to speckle decorrelation for quantitative fringe analysis. Furthermore, shape cannot be determined when using single wavelength. In this paper, we describe a multiple-wavelength microscopic TV holographic configuration that uses sequentially recorded phase-shifted frames at three different wavelengths before and after deformation of the specimen for evaluation of relatively large deformation fields at the effective wavelengths. Use of multiple wavelengths for deformation and shape evaluation is discussed. The design of the system along with the experimental results on small-scale rough specimens under static load is presented.

From surface activation to microfluidic heat pipes: An innovative in-situ wafer level heterogenous bonding method

Multiple hydrodynamic states were observed during cocurrent down‐flow of air and water under trickling flow conditions in a packed bed of rectangular cross section. Although the multiplicity was exhibited by both pressure gradient and liquid holdup, the pressure gradient showed the largest variations at identical conditions. The multiplicity is interpreted as being due to the liquid flowing in two different modes, namely, film flow and rivulet flow.The characteristics of pulsing flow in a packed bed of rectangular cross section were found to be appreciably different from those reported in the literature for flow in small‐diameter cylindrical columns. The most significant observation in the packed bed of rectangular cross section was that the pulses did not always span the column cross section, unlike the case in small‐diameter columns. The lower pressure drop and pulse velocity in the packed bed of rectangular cross section are believed to result from the bypassing of gas around the edge of the pulses. The location of the pulses was found to depend on the quality of gas and liquid distribution at the top of the column, and the shape of the top surface of the packing. A distributor configuration in which the gas was injected directly into the bed was found to be the most desirable, and is recommended in industrial practice.

Based on the statistical regularity of certain error types, an interlanguage grammar could be devised and applied to develop an intelligent computer tool, capable not only of identifying the typical errors in L2 student writing, but also of making adequate corrections. The purpose of the corrections is to make the student aware of the language used and then to sharpen the focus on form. The students, left mostly to their own resources when writing academic assignments in English, which is not their first language, are frequently unsure of the grammaticality of their own sentences. Having an opportunity to have each sentence checked by an expert in both English and their particular interlanguage would not only contribute significantly to the readability of their assignments, but would also facilitate language learning. In a situation where language tutors are available only in the classroom, it becomes clear that any artificially intelligent tool which serves this purpose would be of tremendous benefit. Following the introductory thoughts on L2 learnability, this paper describes the research and development work preceding the piloting of precisely such a tool. It then reflects on various aspects of its initial implementation.