A static and dynamic 3-D surface profilometer with nano-scale measurement resolution was successfully developed using stroboscopic illumination and white-light vertical scanning techniques. Microscopic interferometry is a powerful technique for static and dynamic characterization of micro electromechanical systems (MEMS). As MEMS devices move rapidly towards commercialization, the issue of accurate dynamic characterization has emerged as a major challenge in design and fabrication. In view of this need, an interferometric microscopy based on white-light stroboscopic interferometry using vertical scanning principle was developed to achieve static and dynamic full-field profilometry and characterization of MEMS devices. A micro cantilever beam used in AFM was characterized using the developed instrument to analyze its full-field resonant vibratory behavior. The first five mode resonant vibration can be fully characterized and 3-5 nm of vertical measurement accuracy as well as tens micrometers of vertical measurement range can be achieved. The experimental results were consistent with the theoretical simulation outcomes from ANSYS. Using white-light stroboscopic illumination and white-light vertical scanning techniques, our approach has demonstrated that static and dynamic 3-D nano-scale surface profilometry of MEMS devices with tens-micrometer measurement range and a dynamic bandwidth up to 1MHz resonance frequency can be achieved.
A miniature sensor based on extrinsic Fabry-Perot interferometry is proposed. In this setup, two optical fibers are integrated into a miniature sensing head to produce a pair of quadrature signals for solving direction ambiguity problem. It can also achieve nanometer resolution and at least 10kHz dynamic range after electronic subdivision. Comparing with capacitive senor, it has advantages including electromagnetic interference immunity and long distance measurement capability. In this paper, related theoretical descriptions are introduced and the comparisons with capacitive sensor are conducted. An experiment for detecting the characteristics of hard disk drive with this novel sensor is depicted. Furthermore, a new method of measuring liquid refractive index is described. All the experiment results show that this novel sensor is excellent in displacement and vibration measurement and many other applications.
The precision displacement control in high-resolution instrument is influenced by non-linearity effects of PZT actuators. The capacitive sensor within PZT actuator is often used as a displacement sensor for feedback control, but the calibration and traceability of capacitive sensor are hardly to be accomplished. The optic fiber sensor is a useful high-resolution displacement sensor to perform the measurement in space-limited instrument, and it’s also capable of a non-contact function. In this paper, the structure of an optic fiber sensor was introduced, and the hysteresis characteristic of PZT actuator was evaluated. In addition, the performance of the capacitive sensor within PZT actuator for close-loop control was compared with those of the optic fiber sensor, and the differences ratio between both was less than 0.12 %. Following the scanned images by interference microscope, the images have some distortions before applying the compensated curve function for non-linearity. Thus, the optic fiber sensor could be provided a calibration service for displacement measurement of interference microscope.
For dimensional researches and applications, the end standard measurements are the popular subjects in high precision standard systems or instruments. In general, the gauge blocks are the representative of the end standards. The universal measurement machines (UMM) are usually utilized for the dimensional length of gauge blocks. However, for measuring the dimensional lengths of test gauge blocks (TGBs), they should be compared with the same lengths of the master gauge blocks (MGBs). Thus, there are different lengths of the MGBs needed to be prepared and the measuring procedures are usually very time consuming. In order to lower the cost of procurement and maintenance of MGBs, a continuous end standard measurement system (CESMS) was built for many different test ranges of TGBs. The features of the CESMS included at least one gauge block, the LVDT probes for positioning, the real lengths of the TGBs measured from the display value of the laser interferometer, and total procedures controlled by automation software. All of these parts were integrated onto a large platform and its moving carriage could travel up to 1.2-meter in distance. Within these ranges, the CESMS could measure different dimensional lengths of the TGBs and many pieces at the same time. The CESMS utilized the laser interferometer to acquire the accurate display values between two ends when the LVDT probe was touched and triggered the automation software to record. Owing to the recommended radiation of laser head, the CESMS could be traced to the meter, SI unit. Furthermore, the experiment results showed that the comparison results of certificated gauge block at 800 mm suited for calibration certificate by PTB.
A fiber optic interferometer for a novel application is proposed in this paper. This new configuration and decoding scheme is in particular suitable for an AFM-tip tailoring system. A theoretical analysis method for simulating the relation of displacement and interfering intensity from the fiber optic sensor is thoroughly discussed. Experimental data for evaluating interfering efficiency agree well with simulation results. Higher resolution becomes achievable with the help of the two-channel interferometer decoding scheme. Moreover, the properties of the piezoelectric actuator used in this system are characterized by the optical sensor. This compact sensor exhibits satisfactory performance for the nanometer-resolution requirement of the developing AFM tip tailoring system.