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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes/issues, but are citable by Digital Object Identifier (DOI).
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Measurement Methods and Techniques
Abstract:
Ultra-precise rotary axes are extensively utilized in advanced equipment, and their motion errors can significantly impact the accuracy of these devices. Traditional measurement techniques for rotary axes errors typically involve high-precision standard devices as references, but these can inadvertently reduce measurement accuracy due to inherent shape errors. Furthermore, error separation techniques are both cumbersome and time-consuming. Optical-based measurement methods, though useful, often fail to achieve high accuracy, especially in measuring axial motion errors. This paper addresses the impact of rotary axes motion errors in ultra-high precision aspheric measuring instruments and reviews two existing measurement methods. It introduces a novel measurement approach based on a composite laser target capable of assessing five degrees of freedom in motion errors, including axial, radial, and angular errors. This method employs a composite laser target equipped with a laser point light source and a collimated laser beam, affixed to the rotary axes as a reference datum. The method's efficacy is demonstrated in accurately determining the axes' position and orientation by measuring the target's position and angle. The differential confocal microscopy technique is applied to ascertain the axial position of the laser point source, thereby determining the axes' axial error, while a traditional microscope optical path measures the radial position for radial error. Collimation measurement optical path is used to evaluate the laser collimation beam's angle for angular error assessment. The method exhibits resolutions of 4 nm for axial, 2 nm for radial, and 0.2 μrad for angular errors. Moreover, the feasibility of this method in measuring rotary axes motion errors is validated through tests on an air spindle. Overall, this approach replaces traditional standard devices with an optical reference device, eliminating the need for additional error separation processes and facilitating real-time monitoring of rotary axes motion errors in ultra-high-precision measuring equipment.
Abstract:
With the rapid growth of the semiconductor industry, the demand for high-precision, small-scale three-dimensional nanomanufacturing techniques has increased, necessitating the development of corresponding nanogeometry reference materials. In response, China has independently developed a series of nano-step height reference materials comparable to international standards, achieving traceability to the meter definition through laser wavelength. This initiative has significantly contributed to supporting technological research across various domains, breaking foreign monopolies, enhancing China's nano-geometry value transfer system, and fostering the nano industry's growth. This paper reviews and compares domestic and international research on nano-step height reference materials, summarizing the fabrication methods and metrology techniques. It aims to provide references and insights for future research on nano-step height reference materials and other micro- and nano-geometry reference materials.
Abstract:
Intelligent manufacturing, characterized by capabilities such as self-awareness, self-learning, decision-making, and adaptability, is being progressively integrated into various manufacturing processes including design, production, management, and services. Merging new information and communication technologies with advanced manufacturing methods, it establishes a new production paradigm. Given its definition and the requirements of large-scale equipment manufacturing, intelligent manufacturing is distinguished by four key characteristics: dynamic perception, real-time analysis, autonomous decision-making, and precise execution. Scholars globally have dissected its five-layer architecture encompassing enterprise alliance, enterprise management, production management, control execution, and intelligent equipment layers. Within these, the intelligent equipment layer, which includes processing, assembly, and measurement and testing equipment, is directly linked to metrological assurance. Ensuring real-time online accuracy and reliability of measurement data from intelligent equipment is essential for effective intelligent manufacturing. This paper systematically analyzes the metrological needs of intelligent manufacturing and delves into the elements of processing equipment, assembly equipment, testing equipment, and modeling algorithms, with the objective of constructing a key common metrological technology system.
Abstract:
Ultra-precision displacement measurement technology, utilizing grating interferometers, is pivotal in the field of advanced manufacturing. Employing gratings with higher line densities is a proven method to enhance the accuracy and resolution of these interferometers. Advances in electron beam lithography for grating fabrication have enabled the use of high line density gratings (exceeding 3000 lines/mm) as measurement standards, significantly optimizing interferometer performance. This research employs a high line density electron beam direct-write grating with 3333 lines/mm in a single-path Littrow configuration. The interferometer, characterized by a base signal period of 300 nm, showcases its accuracy and stability in displacement measurement. The comparative setup between this single-path Littrow grating interferometer and a laser interferometer opens new avenues for grating pitch calibration. This study marks a valuable exploration in precision displacement measurement using electron beam direct-write high line density gratings.
Measuring Instruments and Systems
Abstract:
The National Institute of Metrology of China has developed a new primary standard for positional angles, catering to the needs of angle measurement in machine tool rotation positioning, aviation and aerospace attitude control, and spatial orientation in surveying instruments. This standard, aligned with the national verification scheme for plane angle measuring instruments, incorporates advanced technologies such as ultra-precise rotational positioning, self-calibrating scanning interferometry, and continuous full-circle compensation. It enables integrated measurement of both whole and subdivided angles, offering diverse functionalities like static and scanning measurements. This standard spans a measurement range of 0° to 360°, with a sampling step finer than 0.01″, and achieves a measurement uncertainty of U=0.03″ (k=2). It provides a continuous full-circle traceability platform for angle measuring instruments.
Abstract:
The measurement accuracy of nano line widths, a critical nano geometric characteristic parameter, is of paramount importance in fields such as advanced manufacturing. As the scale of nanotechnology continues to shrink, achieving sub-nanometer measurement accuracy presents new challenges. The 26th General Conference on Weights and Measures (CGPM) in 2018 proposed using the silicon {220} lattice spacing as a secondary realization of the meter, providing a novel approach for atomic-level nano line width measurements. In this study, a 22 nm intrinsic silicon lattice line width standard was developed using multi-layer film deposition technology. Employing high-resolution transmission electron microscopy (HRTEM), the silicon lattice constant within the standard was used as a scale for direct nano line width measurement. The measurement uncertainty achieved is better than 1 nm.
Research Progress
Abstract:
As the semiconductor industry, ultra-precision machining, and biomedical fields delve into the nanoscale, the demand for advanced measurement technologies has heightened. Optical methods, with their non-contact, non-destructive, and rapid properties, have been widely employed, yet the resolution of traditional optical microscopes is bounded by the diffraction limit. Scanning Near-Field Optical Microscopy (SNOM), operating on the principles of non-radiative field detection and imaging, overcomes this limit to facilitate nanoscale optical imaging with ultra-high resolution. This review introduces the imaging principles of near-field optical microscopy and analyzes its advantages and disadvantages across various operational modes. It then delves into two crucial aspects of SNOM's ongoing development: enhancing resolution and signal-to-noise ratio (SNR). In terms of improving resolution, approaches like adding nano-antennas to the tips of aperture-type SNOM probes have been explored to break through the probe aperture's resolution constraint. Techniques such as coating optical fibers with metal films or embedding metal nanowires to convert light into surface plasmon forms for high-resolution measurements are discussed. Additionally, the use of a minimal gap mode between the probe and sample to compress the light spot, thereby exceeding the resolution limitations of scattering-type SNOMs, is examined. The review also addresses strategies to augment the light field intensity at the probe tip and improve SNR. These include fabricating various nanostructures at the probe tip to excite surface plasmons, thereby mitigating background noise caused by direct far-field light, and enhancing the SNR. Innovations in fiber-optic probes, such as the inclusion of ring gratings to improve surface plasmon conversion efficiency, are explored to increase the focused light field's intensity and signal strength. The utilization of special structures like platforms to induce surface plasmon reflective resonance enhancement, thus increasing the focused light field's intensity, is also discussed. The article concludes by summarizing the state of near-field optical microscopy and projecting its future development trajectory.
Abstract:
The 633 nm iodine-stabilized Helium-Neon (He-Ne) laser, utilizing saturable absorption technology, is pivotal in length metrology. Its wavelength within the visible spectrum, combined with a simple and compact structure, and excellent wavelength reproducibility, makes it an extensively used length standard in metrology laboratories. Advancing research on the 633 nm iodine-stabilized He-Ne laser is essential for maintaining China's prominence in length metrology and for supporting the nation's digitalization efforts in metrology. This review discusses the fundamental principles, current research advancements, and the digitization process of the 633 nm He-Ne iodine-stabilized laser. The paper also provides insights into future development trends in this field.