In order to compensate three-dimensional (3D) angle errors of two-dimensional (2D) stage in motion, a 3D angle errors detection and compensation system using a modified DVD pick-up head has been developed in this paper. The modified DVD pick-up head, which consists of a commercial DVD pick-up head without objective lens and voice coil motor, is used as an angle sensor. The mechanism of the angle sensor is based on optical auto-collimation, and each sensor can detect two deflection angles of the stage simultaneously. Utilizing the angle error information obtained by two angle sensors which are set along X and Y moving direction respectively, the controlling system adjusts the nano-positioning stage by controlling the piezoelectric ceramic actuators’ movement to compensate the angle errors of the stage. This system can achieve the measurement and compensation of yaw angle error, pitch angle error and roll angle error of the stage. Experimental results show that the angle detection range of this system is ±110", the resolution is about 0.2", and the repeatability error is about 2″. After compensating, the 3D angle errors of 2D stage can be controlled within 3″. This system has the advantages of compact structure, low cost, etc.
The wavelength of laser interferometer used widely in precision measurement instrument is affected by the refractive index of surrounding air, which depends on the temperature, relative humidity (RH) and air pressure. A low-cost mini chamber based on the natural convection principle with high-precision temperature-controlled and humidity-suppressed is proposed in this paper. The main chamber is built up by acrylic walls supported by aluminum beam column and are tailored according to the required space. A thin layer of vacuum insulation panel (VIP) with an ultralow thermal conductivity coefficient is adhered around the walls so as to prevent heat exchange with room air. A high-precision temperature sensor measuring the temperature near the instrument’s measuring point provides a feedback signal to a proportional-integral-derivative (PID) controller. Several thermoelectric coolers uniformly arranged on the ceiling of the chamber to cool the air inside the chamber directly without any air supply system, yielding a vibration-free cooling system. A programmable power supply is used as the driver for the coolers to generate different cooling capacities. The down-flowing cool air and the up-flowing hot air form a natural convection, and the air temperature in the chamber gradually becomes stable and finally reaches the temperature set by the PID controller. Recycled desiccant contained silica gels that have high affinity for water is used as a drying agent. Experimental results show that in about two hours the system’s steady state error is 0.003°C on average, and the variation range is less than ± 0.02°C when the set temperature is 20°C, the RH is reduced from 66% to about 48%. This innovative mini chamber has the advantages of low-cost, vibration-free, and low energy-consumption. It can be used for any micro/nanomeasurement instrument and its volume can be customer-designed.
A tungsten stylus with a ruby ball tip was screwed into a floating plate, which was supported by four leaf springs. The displacement of the tip caused by the contact force in 3D could be transferred into the tilt or vertical displacement of a plane mirror mounted on the floating plate. A quadrant photo detector (QPD) based two dimensional angle sensor was used to detect the tilt or the vertical displacement of the plane mirror. The structural parameters of the probe are optimized for equal sensitivity and equal stiffness in a displacement range of ±5 μm, and a restricted horizontal size of less than 40 mm. Simulation results indicated that the stiffness was less than 0.6 mN/μm and equal in 3D. Experimental results indicated that the probe could be used to achieve a resolution of 1 nm.
The measurement of miniature components with a micro- or nano-coordinate measuring machine requires a high precision contact scanning probe. The elastic mechanism of low stiffness is a major component of the contact scanning probe. A new elastic mechanism is analyzed by the theory of elasticity and finite element analysis in this paper. It is to realize the probe’s mechanical behavior and stiffness when designing an elastic mechanism for a contact scanning probe. The contact scanning probe is composed of a tungsten stylus with a ruby ball tip, a mechanism of floating plate suspended by four V-shaped leaf springs, and a 3D optical sensor. The leaf spring experiences elastic deformation when a contact force is applied. Uniform stiffness model is analyzed. Simulation and experimental results verify the correctness of the analysis.
The accuracy lives of a measurement system and its components are generally different and it will lead to a waste of resources. In order to make full use of the system’s resources and improve its accuracy life, a novel design method based on uniform accuracy life for measurement systems is proposed in this paper. According to the theory of error decomposition and tracing, Hilbert-Huang transform (HHT) method is employed to decompose the total errors of an error test system for a dial gauge and then the accuracy loss functions for the total system and some error parameters are obtained. Based on the analysis of the transfer function for the accuracy loss between the different parts of the measurement system, a constraint model consisting with the uniform accuracy life principle is set up. Taking the maximum life of the measurement system as the objective function, the uniform design model has been solved by means of the optimization methods. The uniform design method can be used to promote the accuracy life of the measurement system.
Three-dimensional measurement of microstructures requires a 3-D microprobe with small probing ball as well as appropriate nanopositioning and nanomeasuring machines. An electric arc melting method is presented in this paper, which could fabricate the monolithic micro-spherical tip on the tungsten wire. Based on the principles of electrode discharging energy absorption and the surface tension phenomenon, a micro sphere is formed at the needle-shape tip of the tungsten wire. The model of dynamic arc discharging is established to analyze the process of sphere forming. Experiment results reveal that a spherical tip about 60 μm in diameter having less than 1 μm roundness error could be achieved on a 100 μm diameter tungsten wire with the selection of proper process parameters, such as the discharging voltage, discharging time and discharging gap. Quality of the probe is mainly determined by the electro-discharge conditions which affect the solidification force and thermal conductivity. The monolithic microprobe can be used in the micro coordinate measurement machines (Micro-CMMs) to allow the measurement of micro grooves possible.
High precision contact scanning probes for measuring miniature components on micro- and nano-coordinate measuring
machines require elastic mechanisms. In order to realize the probe’s mechanical behavior and stiffness when designing
an elastic mechanism for a contact scanning probe, the elastic mechanism is analyzed by the theory of elasticity and
finite element analysis in this paper. The contact scanning probe is composed of a fiber stylus with a ball tip, a
mechanism of floating plate suspended by four leaf springs, and two optical sensors. The leaf springs experience elastic
deformation when a contact force is applied. Uniform stiffness model is analyzed. Simulation and experimental results
verify the correctness of the analysis.
A new high-precision contact probe with a large scanning range is proposed and validated, which is able to measure miniature components on a micro/nano-coordinate measuring machine (CMM). This scanning probe is composed of a fiber stylus with a ball tip, a mechanism with a wire-suspended floating plate, a two-dimensional (2-D) angle sensor, and a miniature Michelson linear interferometer. The stylus is attached to the floating plate. The wires experience elastic deformation when a contact force is applied, and then the mirrors mounted on the plate are displaced; the displacements can be detected by corresponding sensors. According to industrial demands, such as scanning range, resolution, equal stiffness, contact force, and probe size, several constrained conditions are established, and the optimal structure parameters of the probe are selected. Each component of the probe is designed, fabricated, and assembled in this research. Simulation and experimental results show that the probe can achieve uniform stiffness, ±20-μm scanning range, and 1-nm resolution in x, y, and z directions. The contact force is about 40 μN when the tip ball is displaced 20 μm. It can be used as a contact and scanning probe on a micro/nano-CMM.
A new high precision analogue contact probe with long measurement range that is able to measure miniature components
on a micro/nano-coordinate measuring machine (CMM) is proposed. This analogue probe is composed of a fiber stylus
with a ball tip, a mechanism with a wire-suspended floating plate, a two-dimensional angle sensor and a miniature
Michelson linear interferometer. The stylus is attached to the floating plate. The wires experience elastic deformation
when a contact force is applied and then the mirrors mounted on the plate will be displaced, which displacements can be
detected by two corresponding sensors. Each component of the probe is designed, fabricated and assembled in this
research. Base on the design requirements and stiffness analysis of the probe, several constrained conditions are
established, and optimal structure parameters of the probe are worked out. Simulation and experimental results show that
the probe can achieve uniform stiffness, ±20μm measurement range and 1nm resolution in X, Y and Z directions. The
contact force is less than 50μN when the ball tip is displaced by 20μm. It can be used as a contact and scanning probe on
Based on micro-optical devices, a non-scanning 3D profile detecting system is proposed. A 2D point light source array produced by the Micro-optical device is used to form parallel confocal system. It realizes whole-field in-step detecting of measuring plane. In the detecting system, Digital Light Processing (DLP) technology is used, and a Digital Micromirror Device (DMD) substitutes conventional micro-optical elements (like micro-lens array). Therefore, it realizes portable and programmable 2D point light source imaging. All the measuring parameters that influence the measurement can easily be adapted by software to satisfy different requests of measurement. The construction and working principle of the no-scanning 3D detecting system is studied. The method of 3D profile reconstruction is introduced. Experiment result is obtained, which indicates that DLP technology is applicable in confocal detecting.