# Special Issue on Manufacturing Metrology
###### Abstract  
The application of the proposed method to a large-scale system is a new tool for the development of a large-scale system. The proposed method is a novel tool for the development of a large-scale system. The proposed method is a novel tool for the development of a large-scale system.  
achieve nanometer-scale accuracy [8]. The motion error of the stage was separated by a differential measurement configuration for a confocal sensor and a film interferometry module. The same group further designed an internal scanning mechanism for a confocal sensor [9]. By synchronizing the local scan, enabled by the internal actuator in the confocal sensor, and the global scans, enabled by external positioners, the developed system was able to perform noncontact line scans and area scans. Thus, this system was able to measure both surface roughness and surface uniformity. A non-scanning 3D imaging system with a single-pixel detector was reported to achieve 3D imaging of a target via compressed sensing to overcome the shortcomings of existing laser 3D imaging technology [10]. In order to solve the problems in the accuracy and adaptability of existing methods for blade twist measurement, a high-precision and form-free metrological method of blade twist based on the parameter evaluation of twist angular position and twist angle was proposed [11]. A rapid optical gear measurement system was developed for measuring the irregular tooth contours of large ring parts: the tooth root, tooth height, and tooth thickness of the workpiece [12]. The measured diameter was approximately 200 mm, and the radial inspection accuracy was within \(\pm\)20 \(\upmu\)m. Compared with the conventional stylus contacting method, which takes a long time, this image processing method can be performed in one minute. An off-axis differential method for improvement of a femtosecond laser differential chromatic confocal probe was set up to obtain the normalized chromatic confocal output with a better signal-to-noise ratio. It achieved a \(Z\)-directional measurement range of approximately 46 \(\upmu\)m as well as a measurement resolution of 20 nm [13]. For the purpose of in situ measurement, a design framework for optimizing spectral-domain low-coherence interferometric sensors was proposed for profilometry measurements to optimize system performance [14]. Another in situ measurement system dealing with the on-machine precision form truing of resin-bonded spherical diamond wheels was also proposed [15]. A novel nanotechnology presented a method for measuring the high-precision cutting edge radius of single point diamond tools using an atomic force microscope (AFM) and a reverse cutting edge artifact based on the edge reversal method [16]. For precision measurement of miniature internal structures with high aspect ratios, a spherical scattering electrical field probe (SSEP) was proposed based on charge signal detection. The developed SSEP has great potential to be the ideal solution for precision measurement of miniature internal structures with high aspect ratios [17]. For the evaluation of roundness of small cylinders, the linear-scan surface form stylus profilometer was employed. The technique used to compensate for the influences of measuring angular misalignments was also proposed, and the measurement uncertainty was analyzed [18].  
Finally, in this category, the quality of wafer fabrication was studied in two papers. The first one was on the development of a dynamic pad monitoring system (DPMS) for measuring the surface topography of wafer polishing pads using a chromatic confocal sensor. It is applicable to monitoring the pad dressing process and CMP parameter evaluation to produce IC devices [19]. The second one used deep learning methods to develop a set of algorithms to detect wafer die particle defects from the captured images [20]. Both are practical in industrial applications.