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.

To improve the accuracy of micro-coordinate measuring machines (CMMs) to nanometer scale, numerous hardware improvements have been studied and carried out in recent years, albeit with high costs and application limitations. Error compensation technology through software has also been applied because of its high precision, high efficiency, and low cost. A global volumetric error compensation model on the basis of the Abbe and Bryan principles for micro-CMMs is proposed in this study. The volumetric errors of the general CMMs were also analyzed, and the transmission relationship between the volumetric and geometric errors was established in the proposed model. The parameters in the model including 21 geometric errors and Abbe/Bryan offsets were measured and used to compensate for the volumetric errors. A zero-class gauge block was tested using a micro-CMM based on ISO 10360-2. With the volumetric error compensation, the standard deviations of the length measurements in the different diagonal directions were reduced by more than 65%. Thus, the effectiveness of the proposed method was established. This study provides a general modeling method and compensation techniques of volumetric errors for people involved in accuracy improvement for CMMs and machine tools.

Roundness is a kind of form error in geometrical measurement in laboratory and industry and contributes significantly to the uncertainty of the measurement instruments using precision spheres, especially microspheres. A new radius and roundness measurement method for microspheres is proposed in this paper. Using this method, not only can separate different run-out errors from the measuring results, but also can obtain the true radii in different directions of the tested microsphere, which are necessary for the roundness evaluation according to ISO 1101. A new roundness measurement system has also been developed, which is mainly composed of two miniaturized Michelson interferometer (MI) systems, two elastic mechanisms, and a precision rotating stage. Repeated measurements have been performed using a ruby microsphere manufactured by Renishaw Corporation as the reference, which has a claimed diameter and roundness of 700 μm and 130 nm respectively. Experimental results show that the average radius of the tested microsphere is 349.99 μm with a maximum error of 65 nm and an expanded uncertainty of 94.0 nm (k=2). The proposed method and system can be used in the precision contact measurements of parts with micro circular characteristics such as microspheres and micro cylinders.

Laser beam drift greatly influences the accuracy of a four degrees of freedom (4-DOF) measurement system during the detection of machine tool errors, especially for long-distance measurement. A novel method was proposed using bellows to serve as a laser beam shield and air pumps to stabilize the refractive index of air. The inner diameter of the bellows and the control mode of the pumps were optimized through theoretical analysis and simulation. An experimental setup was established to verify the feasibility of the method under the temperature interference condition. The results indicated that the position stability of the laser beam spot can be improved by more than 79% under the action of pumping and inflating. The proposed scheme provides a cost-effective method to reduce the laser beam drift, which can be applied to improve the detection accuracy of a 4-DOF measurement system.

The structural deformations caused by environmental changes in temperature, vibration, and other factors are harmful to the stability of high precision measurement equipment. The stability and optimal design method of a 2D optoelectronic angle sensor have been investigated in this study. The drift caused by structural deformations of the angle sensor has been studied and a drift error model has been achieved. Key components sensitive to thermal and vibrational effects were identified by error sensitivity analysis and simulation. The mounts of key components were analyzed using finite element analysis software and optimized based on the concept of symmetric structures. Stability experiments for the original and optimized angle sensors have been carried out for contrast. As a result, the stability of the optimized angle sensor has been improved by more than 63%. It is verified that the modeling and optimal design method is effective and low-cost, which can also be applied to improve the stability of other sensors with much more complex principles and structures.

The components with micro deep holes have massive presence in different major equipment or systems. Coordinate measuring machine (CMM) remains the main equipment to measure these components because non-contact methods cannot be applied to micro deep holes. However, moving probe tips into micro holes accurately is extremely difficult for CMM through existing methods. Therefore, this study puts forward a self-calibration and high-precision vision method and system. The algorithm for automatic determination of the probe tip movement scheme is proposed, several suitable image processing methods are selected, and the vision system is designed and tested on CMM. Experimental results show that a probe tip with a diameter of $60 \boldsymbol {\mu }\text{m}$ can be moved into micro holes below $100 \boldsymbol {\mu }\text{m}$ with a success rate of 100%. This method and system can be used to provide an effective means for highly precise and fast measurement of micro holes.