Mechanical measurement theory and technology is the main process to obtain mechanical physical information, and the booster to promote the progress of industrial production and manufacturing technology. With China's gradual upgrade from capital- and labor-intensive industries to knowledge-intensive industries, strategic emerging and high-tech manufacturing industries, such as integrated circuits, aerospace, high-speed railway transportation, and new energy vehicles, are becoming key areas for the next decade. To achieve high-performance and high-efficiency manufacturing equipment and processes, it is necessary to comprehensively obtain the service status of high-performance equipment in the operation process and the shape and performance parameters in the product manufacturing process in real time. Hence, this study conducts statistics and literature analyses on funded projects of National Natural Science Foundation of China and comprehensively analyzes the representative progress, research hotspots, and development trends in this field from three dimensions: precision, nano, and quantum measurements. Furthermore, it summarizes important theories, core methods, and key technology progress of mechanical measurements for high-performance manufacturing, discusses the key challenges, and clarifies the major scientific problems for the next 5-10 years.

With the ever-increasing demand for sub-10 nm integrated circuit chips in the fields such as consumer electronics, interconnect hardware, and electronic medical equipment, the impact of wafer defects introduced by semiconductor manufacturing equipment on the yield and price of integrated circuits will continue to emerge, which makes the manufacturing process control such as the high-speed identification, localization, and classification of typical defects more challenging. Although conventional wafer defect inspection methods such as bright-field, dark-field, and electron-beam imaging can cover most defect inspection scenarios, they cannot balance inspection accuracy, sensitivity, and speed. Emerging techniques such as nanophotonics, computational imaging, quantitative phase imaging, optical vortex, multi-beam scanning electron microscopy, thermal field imaging, and deep learning have shown great potential in improving defect sensitivity, resolution, and contrast, which opens up new possibilities for wafer defect inspection. Hence, we make a comprehensive review for the progress in wafer defect inspection from three aspects: the assessment of defect detectability, the diverse inspection methods and prototypes, and the advanced post-processing algorithms. It is expected to help both researchers and interdisciplinary workers who are new entrants in the field.

Higher standards for assembly quality and precision have been introduced with the development of next generation aircraft toward massive, heavy duty, and extended life. High precision measurement of geometry and physical damage in assembly is the basis and key to regulating the aircraft assembly process and ensuring the assembly standard, which has an important influence on the service performance of the aircraft. With a focus on the requirements of the new generation of aircraft with the significant rise in structural size and the development of composite bearing structure, this paper discusses the development of large space point location high precision measurement method, large structure shape high precision measurement method, composite structure assembly defect high precision detection technology, and other aspects of theoretical research and technology application at home and abroad, and indicates the future development trend and prospect of relevant technology.

Scanning white light interferometry is one of the most accurate surface topography measurement techniques. It is widely used in various industrial and scientific research fields. Since its invention more than thirty years ago, the progress and breakthroughs of this technique have been continuously made, driven by the demands of advanced manufacturing sectors such as precision optics, semiconductors, automotive and aerospace. This paper summarizes the important progress of scanning white light interferometry in the past two decades from the aspects of its applications, new measurement methods and algorithms, system designs, theoretical modeling, calibration and error compensation, and puts forward the prospect of further development in this field.

Space gravitational-wave detection is currently an international hotspot. The core technology is to measure the multi-degree-of-freedom motions between two test masses with a distance of few million kilometers. The test sensitivity needs to reach the level of ~1 pm/Hz1/2 and ~1 nrad/Hz1/2 within the frequency band of 1 mHz and 1 Hz. At present, laser interferometer is one of the most precise methods to achieve ultra-precision displacement measurement. In this paper, we introduce the ultra-precision multi-degree-of-freedom measurement using laser heterodyne interferometry for space gravitational-wave detection. The optical design, measurement principle, phase demodulation, and relative research progress at home and abroad are introduced. We also analyze the main noises of laser heterodyne interferometry in space gravitational-wave detection, and the current research of these noise sources are also introduced. Finally, the development trend and prospect of laser heterodyne interferometry for ultra-precision multi-degree-of-freedom measurement are forecasted.

Laser feedback interference (also known as self-mixing interference) is substantially different from traditional laser interference. The former occurs in the laser (light source), and the laser medium gain plays an important role in the interference effect (fringe form). The latter occurs only in the optical path outside the laser. In this paper, from the perspective of application and comparing with the traditional laser interferometry, the key technologies are discussed of feedback interferometer of microchip-laser common-path frequency-modulation, including the "relaxation oscillation" which has special significance for the feedback of solid-state microchip lasers, the formation of high light sensitivity (completely non-contact), the improvement of measurement accuracy, measurement speed, frequency stabilization technology, etc. The results of the team's research on the application of microchip laser common-path frequency-modulation feedback interferometers will also be presented, including feedback confocal microscopy, surface measurement, vibration (and sound) measurement, in-plane displacement measurement, thermal expansion coefficient measurement, refractive index measurement, etc.

In this study, the technological status and development trend of time grating displacement sensors are outlined considering from three aspects. Additionally, the sensors' four performance features and recent developments in four technological application areas are described. Subsequently, the evolution process for three generations of time grating sensors is summarized, and three cardinal classes and four categories of the current field-type time grating sensors are introduced, in addition to discussing their relationship with traditional displacement sensors. Moreover, the possible mechanism for next-generation time grating sensors is logically deducted and analyzed. Finally, three characteristics of the extension of the time-space coordinate transformation theory are explored.

Free space time-frequency reference transfer is the key technology in the application such as global timing and synchronization, high-speed broadband communication, satellite formation flight, and space physical parameter monitoring. The development of optical clock technology puts forward higher requirements for the transfer accuracy of optical time-frequency reference. This paper introduces recent research progress on free space optical time-frequency reference transfer technology, especially the phase and space noise compensation methods based on optical frequency comb carried out by different research institutions, to satisfy the high precision time-frequency transfer under atmospheric turbulence. Finally, the applications using free space optical time-frequency transfer technology are summarized and prospected.

Position and orientation are the basic geometric parameters that represent the spatial orientation and position of the target, such as the flight attitude of an aircraft, the docking position while assembling large products, and the body position of athletes in sports. Therefore, accurate and rapid measurement of position and orientation is an essential task in aerospace, national defense, military, industrial production, sports, and many other fields. To this end, various techniques have been applied to position and orientation measurements, such as inertial guidance, satellite, radar, star-sensitive device, and visual measurement. Hence, this paper summarizes the position and orientation visual measurement methods and their applications, including the basic principles and typical methods, multi-source data fusion measurement method, and the main application areas.

Ultra-precision measurement is the precondition for optics manufacturing. Null test is still the fundamental principle for high-precision measurement of optical surfaces. Computer generated holograms are indispensible for null test of complex surfaces including freeforms. Problems oriented to manufacturing are discussed with emphasis including the principle of CGH null test and its ghost disturbance orders of diffraction, projection distortion correction, uncertainty, and absolute test. The limit of CGH null test is also presented along with possible solutions. For challenges in measuring the dynamically evolving local big errors generated during the manufacturing process, subaperture stitching test and adaptive null test methods are discussed. The progress of in-situ interferometry for machining is then briefly introduced. Finally a prospect of optical surface measurement is presented with focus on ultra-high precision measurement and traceability, macro-micro multiscale measurement of hybrid optics, independently controllable instruments for optical surface metrology, and in-situ integration.

Instruments are the main means of obtaining information and the support of the information industry. Obtaining various information quickly and accurately is a major development trend of measuring instruments, and it is also an inevitable requirement of the rapid development of the information age. Laser multi-degree-of-freedom simultaneous measurement has significant advantages such as high measurement efficiency and simultaneous measurement of multi-degree-of-freedom error parameters. It overcomes the shortcomings of traditional laser single-parameter measurement, such as limited information acquisition and low measurement efficiency, and has become an important research direction in the field of CNC machine tool error measurements. In this paper, according to the order of the integration of the laser single degree of freedom measurement method to the multi-degree-of-freedom simultaneous measurement system, the current laser multi-degree-of-freedom simultaneous measurement method and system are comprehensively introduced, the advantages and disadvantages are analyzed, and the future development trend of the laser multi-degree-of-freedom is discussed.

Surface topography measurement is one of the key technologies for industrial production and scientific research, and the pursuit of high accuracy and high efficiency has always been the direction of the field. With its unique broad spectrum, narrow linewidth, and stable frequency characteristics, optical frequency combs show superior metrology potential and have been developed for a variety of topography measurement techniques. First, the definition of optical frequency combs is introduced; the current research status and characteristics of optical frequency combs in topography measurement are categorized and reviewed according to different technical lines; finally, the outlook of optical frequency comb-based topography measurement techniques is presented.

With the rapid development of the advanced manufacturing industry, the chromatic confocal displacement measurement technology has attracted great attention due to its advantages of high precision, strong adaptability, and high efficiency. It has been widely used in many industries. This paper firstly introduces the application progress of chromatic confocal technology, analyzes some researches in surface topography and workpiece thickness measurement, and explains the performance characteristics of chromatic confocal technology in displacement measurement in many aspects. Secondly, this paper details the key components of chromatic confocal technology, including broad-band light source, dispersive objective, conjugate pinhole, and spectral detection and processing, and demonstrates various innovative ideas in the chromatic confocal technology. These specific implementation technical solutions are broadly compared and analyzed, including the technical characteristics, advantages and disadvantages. Finally, this paper summarizes and prospects the existing technical problems of chromatic confocal displacement measurement technology, in order to provide references for the performance improvement and application expansion of the chromatic confocal technology.

In-situ testing technology for mechanical properties of materials can be used to characterize and analyze the microstructure evolution and damage failure mechanism during the service of materials in the process of mechanical properties testing, and to study the inner law among material composition, process, microstructure, mechanical properties, and service behaviors. The research of key technologies of material forming and processing to promote the design and manufacture of advanced materials is of great significance to serve national defense and national economic construction. In this article, we first review and summarize the development of material mechanical property testing techniques, and then outline the in-situ testing techniques of material mechanical properties by scanning electron microscope, transmission electron microscope, and diffraction imaging. We focus on the in-situ mechanical loading and temperature field construction techniques. Finally, prospects for future trends in the field of in-situ testing for mechanical properties of materials are presented.

Laser interference displacement measurement technology has become a fundamental one for the current and next-generation high-end equipment and ultra-precision metrology due to its large range, high resolution, noncontact, and traceability. Based on a brief introduction of various existing sub-nanometer laser interferometers, in this study, we review the research results of sub-nanometer- and picometer-level laser interference displacement measurement technology from the aspects of precision, accuracy, and speed. First, starting from the principle of laser interferometer, the main errors and technical difficulties that limit the improvement of resolution and speed of displacement measurements are analyzed. Second, the major technological breakthroughs made in recent years in laser high-precision frequency stabilization, high-precision interferometric mirrors, high-speed/high-resolution phase subdivision technology, and environmental compensation and control are highlighted. Finally, the development trends of the next-generation ultra-precision laser interference displacement measurement technology is summarized and prospected.

The operating bandwidth and transmission loss of optical fiber are wide and low. Micro-electro mechanical system (MEMS) manufacturing process can achieve miniaturization, mass production, and high consistency. By combining the above two advantages, MEMS optical acoustic sensors exhibit excellent acoustic detection performance with high sensitivity, wide frequency band, large dynamic range, and high signal-to-noise ratio, which has attracted widespread attention and in-depth research by researchers. According to the different structures of acoustic sensing units, MEMS optical acoustic sensors are divided into micro-structured fiber grating types, fiber interferometer types, and micro-resonator types. The sound detection principle of different MEMS optical acoustic sensors are introduced, respectively. Then their research status in the field of different sound detections and the most mature application fields of them are discussed. Finally, the future development trend of MEMS optical acoustic sensors, which can be combined with silicon-based optoelectronic integration technology to realize system on-chip integration, is prospected.

Aiming at the requirement of two-dimensional sub-micron precision synchronous measurement for ultra-precision motion stage, a reflective two-dimensional grating measurement system is proposed and established. The synchronous measurement method of plane displacement of reflective two-dimensional grating is investigated, and an error transfer model of reflective two-dimensional grating measurement system is established. Through Vold-Kalman filtering algorithm, the high-order harmonic error and amplitude/phase error in the grating signal are corrected and filtered in real time. An arc-tangent subdivision algorithm and period measurement method are used to measure the frequency of the orthogonal pulse of the grating to realize the high-resolution measurement and real-time speed measurement. A reflective two-dimensional grating measurement system with sub-micron measurement accuracy is constructed, in the measurement range of 500 mm×500 mm, the positioning accuracy of the x-direction and y-direction is ±0.3 μm and the resolution is 0.005 μm.

At present, for six-degrees-of-freedom measurement of industrial targets, the visual measurement technology has difficulty in taking account of the measurement efficiency, accuracy, and range. Therefore, this paper proposes a six-degree-of-freedom measurement method based on swinging multi-camera tracking to achieve high efficiency, high accuracy, and large range pose measurement by combining multiple images in different angles of same position to form redundant constraints for large-size coordinate calculation. First, a camera rotation-swing motion model is proposed to realize fast estimation of the camera pose, and use it as a priori information to perform image matching and space resection to obtain accurate camera pose, to perform space forward intersection. Then, a pose estimation method based on image point adjustment is proposed, which directly uses the image point information of the object's moving as the observation value to get its optimal pose estimation. Experimental results show that the measurement efficiency is increased by 4 times, the maximum error of single-point accuracy is no more than 0.2 mm, and the maximum error of pose accuracy is no more than 0.043°, which proves that the proposed method can effectively measure the six-degree-of-freedom posture and balance the measurement efficiency, accuracy, and range.

Ultrasonic nondestructive testing is of great significance to ensure the working of equipment in aerospace, petrochemical, railway, and other fields. Transverse wave ultrasonic testing is an important method for the detection of internal defects in solids due to its advantages of weak attenuation of vibration mode, low sound speed, and high spatial resolution. However, due to the vibration characteristics of piezoelectric wafers, conventional ultrasonic transducers cannot directly transmit and receive transverse waves and need to refract the transverse waves with the help of oblique incidence, and due to the particularity of oblique incidence, it is necessary to consider the refraction effect and slope detection simultaneously, which increases the burden of ultrasonic imaging reconstruction calculation. Therefore, a wavenumber-domain fast reconstruction technique using ultrasonic scanning for transverse waves is proposed. The method is built based on classical synthetic aperture focusing technology (SAFT) by integrating the coordinate transformation in wavenumber domain and transverse wave wavefield extrapolation for the application of oblique incidence transverse wave imaging. The simulation and experimental results show that the proposed method can build excellent detection results when detecting transverse holes, cracks, and hemispherical flat-bottom holes with refraction angles from 20° to 60°. Compared with the time-domain synthetic aperture focusing technique, the computational efficiency of this method is improved by at least 100 times without losing the reconstruction accuracy.

In the visual-inertial positioning system, the calibration of the sensor pose relationship plays a crucial role in realizing accurate spatial positioning. Existing calibration methods lack integration for multi-sensor systems, and the calibration accuracy is limited. In this paper, a high-precision integrated calibration method for the position and attitude of the visual-inertial system is proposed. A precision three-axis turntable is used to provide the angle reference. The extrinsic parameters between the inertial measurement unit (IMU) and turntable are solved based on the invariance of the gravity vector and the consistency of centripetal acceleration values. The control field is constructed by the turntable to provide spatial angle constraints for camera calibration, and the intrinsic and extrinsic parameters of non-overlapping cameras are jointly optimized. Simulation and experimental results show that this method has high calibration accuracy and stability. In the combined positioning test of the multi-camera IMU system, compared with the classical calibration method Kalibr, using the calibration results of this method, the angle deviation of the system motion trajectory fitting axis is decreased by 40.32% and the distance deviation is decreased by 18.93%, which can meet the calibration requirements of high-precision visual-inertial positioning systems.

High accuracy three-dimensional (3D) imaging of precision components is vital for industrial manufacturing and inspection. To address the low efficiency and low accuracy of the existing line laser measurement system, a line laser three-dimensional measurement system using telecentric imaging is proposed herein, and the calibration method of the system is analyzed. First, target images of different positions and the same position under laser irradiation are obtained, and the relationship between the internal parameter matrix coefficient and external parameter pose of the camera is calibrated via telecentric orthogonal imaging. Subsequently, the geometric relationship between the line laser projection and calibration target planes is established, the laser line direction vectors under different target planes are solved, and the equation of the light plane is obtained via the least-squares method. The Levenberg-Marquard nonlinear optimization algorithm is used to accurately calculate the optimal solution of calibration parameters under the maximum likelihood criterion. Additionally, a test system and a calibration program are developed. Experimental results show that under a 60 mm × 48 mm field of view, the designed system can achieve a measurement accuracy of 18 μm; furthermore, it can rapidly and accurately reconstruct the three-dimensional geometric model.

Owing to the development of smart cities, intelligent transportation, and the Skynet project, increased attention is being paid to the decoupling technology used in the transmission and reflection of the overlapping images of car windows, which is essential for checkpoint registration, driver monitoring, fugitive trailing, and military counter-terrorism. In this study, a light transmission and reflection model based on polarization imaging technology is established and a decoupling method for transmitting and reflecting light from car windows is proposed to overcome the drawbacks of traditional imaging technology such as the reliance on intensity information and susceptibility to disturbance. The results conducted under the simulated indoor and realistic outdoor scenes show that the image information entropies of the de-reflected images of a saloon car and passenger car model are 14.3% and 9.8% higher than those of the original intensity images, respectively. Moreover, the image information entropy of the de-reflected image of a real vehicle is 2.7% lower than that of the original intensity image because the reflection contains a large quantity of environmental information. Additionally, the region contrast of these de-reflected images is improved by 40.1%, 117.5%, and 237.8%, respectively, compared with those of the original intensity images. Therefore, the relationship between the decoupling quality of the overlapping image and geometric factors of the model is studied, and a conclusion aimed at providing a reference for the installment height of the camera and position of the vehicle stop line is provided.

Optical three-dimensional (3D) topography measurement technology has been widely used in different fields because of its non-destructive, rapid, high precision, and other advantages. Rapid and accurate measurements of the 3D morphology of specular/diffuse composite surfaces in industrial production have been an unsolved problem. In this study, a method for specular/diffuse composite surface measurements based on fringe projection and dual-screen transmission display is proposed, and the nonlinear response of the system is compensated. First, the normal and transparent screens display green stripes, which are partially reflected by the mirror. In addition, the projector projects a blue sinusoidal stripe pattern to the diffuse part. Second, the camera captures the deformed fringe patterns of different colors. Subsequently, the system parameters are obtained via 3D calibration, and the 3D morphology of the object is recovered based on the relationship between phase and depth. Finally, the nonlinear response error of the system is corrected and compensated to improve the accuracy of 3D measurements. The experimental results show that the proposed method can achieve high-precision measurements of the 3D topography for discontinuous composite surface objects.

A synthetic-wave absolute-distance interferometry system is proposed to achieve high-accuracy absolute-distance measurements. In this system, the light source is a quadrature-demodulated Pound-Drever-Hall frequency-stabilized two-cavity dual-frequency Nd∶YAG laser (TCDFL) with a significant frequency difference. A Mach-Zehnder interferometry structure is employed, and a synthetic-wave absolute-distance heterodyne interferometric system is designed; hence, two heterodyne interference signals with the same frequency can be obtained. The phase-difference of both heterodyne interference signals is measured to determine the fractional order of the synthetic-wave interference fringes. In addition, the integer order of the synthetic-wave interference fringes can be uniquely determined by preliminarily estimating the measured distance. Thus, absolute-distance measurements can be achieved. An experimental system of synthetic-wavelength calibration and absolute-distance interferometric measurement is established using the diode-pumped orthogonally and linearly polarized TCDFL with a frequency-difference of 24 GHz at 1064 nm. The experimental results show that the synthetic-wavelength in the air is 12.4614 mm with a standard deviation of 0.13 μm. A repeated measurement average of 899.3851 mm is obtained at a measured absolute-distance of 900 mm. Correspondingly, the standard deviation and measurement uncertainty are estimated to be 1.36 μm and 4.08 μm, respectively. This experimental study lays a solid foundation for future research and development of high-precision absolute-distance interferometers.