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2D rotary stages are applied in many manufacture equipment. Besides inherent geometric errors in each axis, the position and orientation errors between the two axes are also important position independent geometric errors. Considering the existing methods for testing position and orientation are complex, a simple method is proposed. A laser diode is assembled on the end of the 2D rotary stage's transit axis, and a position sensitive device is used to test trajectories of laser spots when the transit axis rotates. Then, the standing axis rotates 180 degrees and the laser diode is assembled on the transit axis's another end. The same experiment is repeated, and the position and orientation errors of the two axes are separated by comparing the center positions of the two trajectories. The test errors of the position and the orientation error were less than 4μm and 1 arcsec according to calibration.

Low-frequency vibration is one of the harmful factors that affect the accuracy of micro-/nano-measuring machines because its amplitude is significantly small and it is very difficult to avoid. In this paper, a low-cost and high-precision vibration generator was developed to calibrate an optical accelerometer, which is self-designed to detect low-frequency vibration. A piezoelectric actuator is used as vibration exciter, a leaf spring made of beryllium copper is used as an elastic component, and a high-resolution, low-thermal-drift eddy current sensor is applied to investigate the vibrator's performance. Experimental results demonstrate that the vibration generator can achieve steady output displacement with frequency range from 0.6 Hz to 50 Hz, an analytical displacement resolution of 3.1 nm and an acceleration range from 3.72 mm s−2 to 1935.41 mm s−2 with a relative standard deviation less than 1.79%. The effectiveness of the high-precision and low-cost vibration generator was verified by calibrating our optical accelerometer.

This paper presents two micro/nano level displacement sensors, which consist of a mini LDGI (linear diffraction grating interferometer) and a focus probe. These two sensors are integrated into the spindle system of a micro/nano-CMM. This micro/nano spindle system is fixed on a rectangular granite bridge to achieve the z-axis function. The motion of the spindle is driven by an ultrasonic motor on a precision cross-roller slide. Its displacement is fed back by the LDGI. A DVD pick-up head is modified with its S-curve principle as the non-contact focus probe. Mounting the probe onto the spindle head, it is possible to achieve a large displacement and nanoresolution measuring spindle system with a feedback nanomotion control scheme. After accuracy calibration and error compensation, the spindle motion to 10 mm can perform 10 nm positioning accuracy and 30 nm measurement accuracy. Experiments on some ultraprecision profiles have shown the capability of this spindle system.

This study develops a low-cost, highly sensitive two-dimensional optical accelerometer based on a commercially available DVD optical pick-up head. Vibrations of the structure of interest cause a change in the angle of the seismic mass within the accelerometer. The relative movement between the seismic mass and the base produces a change in the distribution of a focused light spot on the surface of a four-quadrant photodetector. The resulting change in the output of the voltage signals by the photodetector is then used to calculate the corresponding acceleration of the base. The experimental results indicate that the resonant frequencies of the accelerometer in the X- and Y-axis directions are 92.75 Hz and 92.87 Hz, respectively. Furthermore, the useful frequency range of the accelerometer is found to be approximately 20% of its resonant frequency. The sensitivities of the accelerometer in the X- and Y-axis directions are 22.9 V/g and 21.3 V/g, respectively. Finally, the noise equivalent acceleration (NEA) of the accelerometer is found to be less than 30 µg Hz−1/2 over the frequency range 0.5–50 Hz.

A high-precision and low-cost micro-CMM (coordinate measuring machine) is under development. The expected measuring range is 25 × 25 × 10 mm3 and the resolution is 1 nm. In order to enhance the structural accuracy, some new ideas are integrated into the design, such as the arch-shape bridge for better stiffness and thermal accuracy, and the co-planar stage for less Abbe error. The linear diffraction grating interferometer and subdivision technique is proposed for position sensing to nanometre resolution. The focusing probe on the laser interferometer feedback spindle is structured in the Z-axis to guarantee the nanometre stability. In this report, the detailed design principles of the developed micro-CMM are described. The performance evaluation of each module of the prototype micro-CMM is presented. The positioning resolution of each axis to 1 nm can be achieved by combining the coarse and fine motion control on a piezo-ceramic linear motor. The Z-axis measurement can be controlled to within 15 nm repeatability. Parts of the positioning repeatability of the co-planar stage have been achieved to 30 nm. Some problems due to current techniques will be addressed.

On the basis of the principles of structured light projection, phase shifting and triangulation, a new digital stereomicroscope system for micro-3D measurement is presented in this paper. Because the image fibre has many advantages such as direction changing and long distance transmitting without extra optics, this system also adopts it to project the structured light instead of the fixed optical systems. Thus, the measurement head is very small; the measurement distance and orientation could be changed expediently. Experiments showed that this is a useful system to measure the 3D profile of meso- and micro-scaled parts.

The present study considers an autofocusing laser probe system used for the measurement of the surface profile and roughness of an object. The system is based upon a modified pickup head of a commercially available DVD player which uses a voice coil motor (VCM) to drive an objective lens during the autofocusing process. It is known that hysteresis of the VCM during the autofocusing process reduces the precision of the measurement results. Consequently, the present investigation adopts a hysteresis model to develop a compensation method which can improve the accuracy of the optical pickup head within the measurement system.

Al ow-cost and high-precision straightness measurement system using a DVD pick-up head has been developed in this research. By removing its objective lens the pick-up head of a commercial DVD player possesses excellent properties of stable laser power, collimated laser beam, circular Gaussian distribution and sensitive photodetectors. A moving knife-edge piece is placed between the pick-up head and a plane mirror. According to the knife-edge principle, the non-shaded part of the laser beam will be reflected back and focused onto the four-quadrant photodetector of the pick-up head. The four-quadrant signals are added to measure the returned laser power. Theoretical analysis based on the circular Gaussian distribution theory and regression method can attain the straightness error of the knife-edge while it moves along the beam direction. This low-cost system can apply to the straightness measurement of precision coordinate measuring machines and NC machine tools. Experimental results showed the achieved accuracy is better than ±0.2 µ mw ithin the measuring range of 200 µm.

In this study, a variable-resolution optical measurement system (VROPMS) based on triangulation measurement technology is proposed. The VROPMS optical scanning probe is composed of dual CCD cameras fitted with zoom lenses and a line laser diode projector. A flexible and novel calibration procedure for VROPMS is developed to acquire the system parameters quickly and accurately. The central position of the reflected laser image is calculated using Gaussian function least-squares fitting of the beam intensity. Subpixel resolution can thus be acquired. Experimental calibration results show that the higher the lens magnification, the finer the derived system resolution. The best accuracy at the zoomed focus position is about 0.02 mm. This system can flexibly zoom in or out to measure a 3D object profile in sections according to the approximate surface profile. Varied mesh images taken from different zoom positions by VROPMS can be patched using the image matching technique to reconstruct the entire profile. A human sculpture with a complex surface profile is measured using VROPMS as a practical illustration of the effectiveness of the system.

In this research, a low-cost and precision autofocus laser probe system was developed. Modified from the pickup head of a commercially available DVD as a basis, it can detect the focus error signal (FES) of the object with a built-in four-quadrant photodiode. The FES will feed back to the developed controller, through which the objective lens can be adjusted in position automatically to remain in focus, driven by a voice coil motor (VCM). The driving current (converted from servo-FES) of the VCM and the objective lens displacement are one to one linearly related within several hundred micrometres. Because of this relationship, the surface profile and the surface roughness of the tested object can be realized. Calibrated results showed that the designed probe has 200 µm linearity range, 0.2 µm accuracy, 0.1 µm resolution and standard deviation of 0.2 µm on average. Some examples are given to show the applicability of this probe system.

A prototype of a stylus probe with an interferometric transducer for surface profiling and roughness measurement was recently developed for surface texture, form error, radius, inclination and dimension measurement. A reflective cylindrical holographic diffraction grating fabricated into cylindrical shape, referred to as the `length master', acts as the moving part governing the path length of light. The surface profile information was transformed into electrical signals using a laser diode grating interferometer to measure the rotational motion of the measuring lever. To precisely define the performance capability of the system, error analysis was performed in order to assess the potential measuring error due to imperfections in manufacturing and assembly of the system's mechanical components. The uncertainty relating to the construction of the device, geometrical features, operating environment and optical characteristics is also presented.

A high-precision optical probe based on the principle of focusing-range detection is developed in this research. The probe adopted for use was directly taken from the pick-up head of a CD player. Because its principle is similar to that of the autofocusing probe, the characteristics of each component of the head were investigated and its conversion into a focusing probe was attempted. The S-curve within the focusing range can be analysed, revealing the linear relationship between the normalized focus-error signal (FES) and the measured distance. The system accuracy of the probe was found. Within the measurement range of 10 µm the linearity error was about 1%, the standard deviation was about 34 nm and the frequency response was about 8 kHz. Some practical applications were carried out, namely profile measurements of a step height, a CD surface and a silicon-wafer grating. All results were highly consistent with the nominal values.

In the field of micro/nano technology, microspheres are often used as the tip-ball of a measuring stylus, such as in micro/nano coordinate measuring machines (CMMs). Conventional tactile probes adopt ruby or steel balls with diameters in the range of several millimeters to 0.3 mm. For a micro-CMM, the required probing ball is as small as possible in order to be inserted into a small groove for side wall measurement. The exact diameter of the tip-ball has to be calibrated for radius compensation and its roundness error has to be qualified. A roundness measuring system for microspheres is developed in this study. Two small Michelson interferometers are designed for direct measurement of microsphere diameter from both sides, being a two-point method. By rotating the measured sphere and reading the displacement shifts of the two interferometers, the run-out of the sphere can be eliminated. The resolution of the developed system can reach 1 nm and the accuracy can reach 10 nm. Two microspheres are tested with good repeatability. This system can also be used for macrosphere measurement.

Levels are fundamental metrological tools for machine leveling and angle measurements. Current levels are all based on the pendulum principle and bubble vial principle. The former is precise but complicated, while the latter is not precise enough. This paper presents a novel, simple and precise optoelectronic level. It is based on the principle of light refraction in the transparent and viscous fluid. The fluid surface is always in leveling condition regardless whether the ground is level or not. Measuring the refraction angle with precise dual-axis autocollimator can directly reflect the inclined angle of the level. A leakage prevention design is also proposed to allow the level to be placed in any pose. Calibrated by an angular interferometer, the error of the dual-axis optoelectronic level is better than ?0.7 arcsec in the measuring range of ?100 arcsec, and better than ?0.4 arcsec for the range of ?30 arcsec, for both axes. Without the need of a pendulum mechanism, this is a simpler design for precision level.

The accuracy of machine tools is mainly determined by angular errors during linear motion according to the well-known Abbe principle. Precision angle measurement is important to precision machines. This paper presents the theory and experiments of a new dual-axis optoelectronic level with low cost and high precision. The system adopts a commercial DVD pickup head as the angle sensor in association with the double-layer pendulum mechanism for two-axis swings, respectively. In data processing with a microprocessor, the measured angles of both axes can be displayed on an LCD or exported to an external PC. Calibrated by a triple-beam laser angular interferometer, the error of the dual-axis optoelectronic level is better than ±0.7 arcsec in the measuring range of ±30 arcsec, and the settling time is within 0.5 s. Experiments show the applicability to the inspection of precision machines.

A new high precision contact scanning probe able to measure miniature components on a micro/nano-coordinate measuring machine (CMM) is proposed. This contact probe is composed of a fiber stylus with a ball tip, a floating plate and focus sensors. The stylus is attached to a floating plate, which is connected to the probe housing via four elastic wires. When the probe tip is touched and then deflected by the workpiece, the wires experience elastic deformations and the four mirrors mounted on the plate will be displaced. These displacements can be detected by four corresponding laser focus probes. To calibrate this touch trigger probe, a double-trigger method is developed for a high-speed approach and a low-speed touch. Experimental results show that the probe has a symmetric contact property in the horizontal XY plane. The contact force is found to be about 109 μN. The standard deviation of the unidirectional touch is less than 10 nm and the pre-travel distance is around 10 nm with a standard deviation of less than 3 nm.

In this paper, an economical and highly sensitive optical accelerometer using a commercial optical pickup head is proposed. In the proposed design, the moving part of a voice coil motor (VCM) built in the DVD pickup head is used as the seismic mass which combines with the optical system of the DVD pickup to form an accelerometer. This system not only reduces the design complexity and the manufacturing process but also obtains good measurement effect. Experimental results have shown that the accelerometer at low frequency has a sensitivity of 24.362 V/g.