Low-frequency vibration is a harmful factor that affects the accuracy of micro/nano-measuring machines. Low-frequency vibration cannot be completely eliminated by passive control methods, such as the use of air-floating platforms. Therefore, low-frequency vibrations must be measured before being actively suppressed. In this study, the design of a low-cost high-sensitivity optical accelerometer is proposed. This optical accelerometer mainly comprises three components: a seismic mass, a leaf spring, and a sensing component based on a four-quadrant photodetector (QPD). When a vibration is detected, the seismic mass moves up and down due to the effect of inertia, and the leaf spring exhibits a corresponding elastic deformation, which is amplified by using an optical lever and measured by the QPD. Then, the acceleration can be calculated. The resonant frequencies and elastic coefficients of various seismic structures are simulated to attain the optimal detection of low-frequency, low-amplitude vibration. The accelerometer is calibrated using a homemade vibration calibration system, and the calibration experimental results demonstrate that the sensitivity of the optical accelerometer is 1.74 V (m·s⁻²)⁻¹, the measurement range of the accelerometer is 0.003–7.29 m·s⁻², and the operating frequencies range of 0.4–12 Hz. The standard deviation from ten measurements is under 7.9 × 10⁻⁴ m·s⁻². The efficacy of the optical accelerometer in measuring low-frequency, low-amplitude dynamic responses is verified.

Optical accelerometers are high-precision inertial sensors that use optical measurement technology to achieve high-precision and electromagnetic interference-resistant acceleration measurements. With the intensive research and development of optical accelerometers in recent years, their applications in inertial navigation, structural health monitoring, precision vibration isolation systems, wind turbine fault monitoring, earthquake monitoring, and other low-frequency vibration detection have flourished. Optical accelerometers have various schemes; however, their characteristics vary considerably due to different optical modulation schemes. This study aims to address the lack of systematic evaluation of currently available low-frequency optical accelerometers. Optical accelerometers can be classified into four categories in accordance with their optical modulation schemes: optical path-, optical intensity-, optical phase-, and optical wave-length-modulated accelerometers. The typical performance, advantages and disadvantages, and possible application scenarios of various optical accelerometers are summarized. This study also presents the current status and trends of low-frequency optical accelerometers in consideration of the growing demand for high-precision, low-frequency acceleration measurements.

Unknown micro-contact forces may affect operation accuracy in micro-operation technology and high-precision contact measurement. Existing micro force sensors are unable to meet the demand for high resolution, large range, and low cost. Therefore, a more economical solution for high-precision force measurement is needed. A high-precision optical force sensor (OPFS) with a simple sensing principle is proposed in this study. The OPFS is mainly composed of a laser diode, a force-sensitive structure, and a four-quadrant photodetector (QPD). When force is applied to the measuring platform, the force-sensitive structure produces the corresponding elastic deformation, which is sensed by the QPD. The multi-range and customized resolution of the OPFS can be achieved by adjusting the stiffness of the force-sensitive structure. The design and optimization of the OPFS are completed via theoretical modeling and simulation analysis. The performance of the OPFS is examined experimentally. The OPFS is found to have a sensitivity of 0.27 mV/ $\mu \text{N}$ , a measuring range of 0–2.71 mN, and a resolution of $32\mu \text{N}$ . The measurement uncertainty of the OPFS due to nonlinearity, resolution, repeatability, and drift is $82\mu \text{N}$ . The effectiveness of the OPFS in the measurement of micro-forces is verified. Finally, the OPFS is used to measure the contact force of a micro/nano contact probe. The results show that OPFS can be used for force calibration in micro/nano contact measurement instruments.

The characterization of a high-precision component with its dimensions has become a key problem in ensuring the performance of system parts. A touch trigger probe plays an important role in experimentally measuring these properties. In this study, a new high-resolution touch trigger probe based on a modified optical lever method is proposed. Only one optical sensor is adopted. The sensing principle of the developed probe in 3D is investigated through the probe’s sensitivity models. An optimizing design of the elastic suspension is demonstrated. Experiments on probe performance are conducted by measuring a step height and a gauge block. Experimental results indicate that the probe achieves a resolution of up to 1 nm in 3D and a measurement standard deviation of 18.3 nm. The probe has a permissible range of ± $20~\mu \text{m}$ in the ${x}/{y}$ -axis and $20~\mu \text{m}$ in ${z}$ -axis. The drift of the probe is 5.2 nm within 30 min. The comprehensive uncertainty of the probing system is 18.45 nm. The developed probe can be used in micro/nano coordinate measuring machines.

The dynamic characteristics of a probing system directly affect the accuracy of dynamic measuring results and should be investigated comprehensively. Many methods can be used to identify the dynamic model of a probe. However, the uncertainty evaluation for the identified probe model remains a problem. A method based on signal transmission chain analysis is proposed in this paper to evaluate the uncertainties for dynamic identification of a micro contact probe. Taking a homemade micro contact probe as an example, the adaptive recursive least squares method is adopted to identify the probe model parameters according to the step input signals and the corresponding output signals of the probe. The signal transmission chain analysis method is utilized to analyse the source of uncertainties and their transmission relationships. The Monte Carlo method is employed to evaluate and combine the uncertainties of the obtained model parameters. Evaluation results are verified by experiments. The results of uncertainty evaluation can guide the compensation and improvement of the dynamic characteristics of the probing system. The proposed method can also be used to evaluate the uncertainties of dynamic identification for other sensors.

Two-dimensional (2D) accelerometer is a commonly used sensor for detecting horizontal vibrations. However, their low frequency response characteristics are limited by high cross-axis sensitivity and low resolution. To address this challenge, this study proposes a new 2D optical accelerometer based on a symmetric 2D vibration pickup unit and a high-sensitivity 2D angle sensor modified from a DVD pickup head. The parameters of the symmetrical 2D pickup unit were determined through modeling and simulation, and the performance of the accelerometer was tested experimentally. Experimental data show that the accelerometer has good low frequency response characteristics in the range from 1 to 10 Hz, sensitivity is better than 2.5 V/(m/s ² ), cross-axis sensitivity is less than 0.075 V/(m/s ² ), and the resolution is better than 0.4 mm/s ² . Moreover, the sources of uncertainty of the accelerometer were analyzed in detail and the synthetic uncertainty of the accelerometer was analyzed based on experiments. Compared with conventional techniques in this area, the proposed 2D optical accelerometer has featured the advantages, such as high accuracy and low cross-axis sensitivity, and can be widely used for low-frequency vibration monitoring in engineering applications.