Papers by Author: Kuang Chao Fan

Abstract: As is well known, the phase-shifting interferometry techniques allow to reach longitudinal resolution to ~ 0.1 nm, but the value of lateral resolution remains at the level of ~ 1 mm. For providing of high lateral resolution of linear measurements in the interference microscope profilometer it was proposed to use a position detection sensor of sharp edge. Principle of sensor’s measurement is based on registration of laser spot intensity scattered by the measurement sample surface under displacement of sample in the lateral direction. The paper shows the prototype scheme of measurement system containing the Linnik interferometer used for surface nanorelief measurement and a position detection module of sharp edge. Measurement process and experimental results are presented. The combining of measurement results performed by the Linnik interferometer and a position detection sensor of sharp edge can allow us to precisely (better then diffraction limit) define the position of sharp edge on the reconstructed surface nanorelief.

Abstract: A compact two-dimensional angle sensor with a measurement resolution that exhibits superior sensitivity has been designed based on the autocollimator principle to enable the precision measurement field to measure the pitch and yaw error motions of a moving object. The signal drift of this sensor affects the measured angle and is mainly caused by the change in environmental temperature. To improve the thermal stability of the sensor, computer simulation has been conducted using the finite element analysis software ANSYS 16. Simulation results show that the angle sensor is considerably stable to adopt mechanisms with a symmetrical structure. Thus, a modified optimal angle sensor is developed, and its thermal stability has been verified via contrast experiments. Compared with the original sensor, the average drift of the optimized angle sensor is reduced from 0.430 arcsec∕°C to 0.120 arcsec∕°C when the variation of the environmental temperature is 5 °C. The optimal angle sensor is ideal for high-precision measuring equipment.

Abstract: In this study, a constant temperature environment chamber with high stability is proposed. In the proposed design, the outer temperature is controlled by the air conditioner, the inner temperature is controlled by the electric current generated to control several thermoelectric cooling units. The separation design of the environment chamber from the cooling system can reduce the vibration caused by the thermoelectric cooling elements. This system adopted the Rake’s System Identification Method to obtain the system model, so that optimum PID parameters can be acquired from the simulation of Matlab Simulink. The results show that the vibration can be effectively reduced and the temperature can be controlled within the range of 20±0.007°C in the steady state.

Abstract: This paper presents fabrication and characterization of a pressure-sensitive polymeric composite on a flexible readout circuit as an artificial skin. Porous nylon was used as the matrix, which provided skin-like mechanical properties. Inside the matrix, polypyrrole was electrochemically deposited and acted as conductive dopant. The fabrication was detailed. The conductivity of the fabricated composite increased when a compressive load was applied. The electro-mechanical characteristics of the composite were measured.

Abstract: This paper utilizes embedded systems to control an intelligent robot implemented with seven sensor networks. The work was carried out in two phases. The first step developed scanning circuits to feedback the sensor signals to the process systems. The second step installed seven motors and a voice circuit on the robot to respond to the sensor signals. From the results, the proposed embedded system was deemed effective.

Abstract: A flexible temperature sensor array and a scanning system are developed in this paper. A 16×16 temperature sensor array in a 25×20 mm2 area is fabricated on a flexible copper-PI substrate using MEMS fabrication technology. Platinum is employed as the temperature sensing material, which is often so called the resistance temperature detector (RTD). Copper patterns on both sides of the flexible substrate serve as the row and column interconnects for scanning circuitry. In each element of the temperature sensor array, the resistance of platinum, which is patterned by lift-off process, can be measured by the scanning system.

Abstract: An innovative high precision optical focus probe has been developed to measure the grating pitches. This probe uses characteristics of FES (focus error signal) of the modified DVD pickup head. Experimental tests showed the linear range of FES of this probe to the gratings was 5μm, the resolution was less than 1nm, the time stability was 5nm in 10 minutes, and positioning repeatability was better than 12nm. This system was applied to measure the grating pitch of 1200 lines per 1mm. The quality of the grating was assessed by the average of sampled pitches and its standard deviation. The inspected results can be an index to improve the process control of the grating fabrication.

Abstract: DVD player is regarded as a mature and low-cost commercial product for multimedia and computer data storage. Fundamentally the pickup head is a key part of the DVD player and it uses focused laser beam to read the data on the DVD disk tracks whose width is approximately 0.74μm. This research focused on the control aspect applied to a DVD pickup head for the development of an auto-focusing laser probe. Practically, the laser pickup head has the S-curve linearity property with the measuring range of about 7μm [3]. To extend the measurement range, the feedback control of VCM in the focusing direction is needed. This study used Genetic Algorithms (GAs) to search for appropriate PID gains for VCM control. In MATLAB simulation, the GAs tuning scheme could produce the optimised gains within less than 0.02 sec. Moreover, the experimental results demonstrated that the VCM auto-focusing measurement range could be extended to 1350μm.

Abstract: For the purpose of micro stage used in micro positioning, a miniature aerostatic air bearing linear slide system was studied. Different arrayed micro-hole plates were fabricated. Using focused laser drilling, the diameter of the hole is limited to 300m. However, with the MEMS process, smaller diameters up to 30m could be achieved. A miniature air bearing linear slide was constructed by imbedding three developed air pads in the slider block, which could slide along a small granite straightedge to form a small sliding stage. The pressure distribution of air pad simulated by the Spectral Element Method was found in good agreement with experimental results. It was also found that the smaller the micro holes the better stability of the floating condition can be obtained. Straightness tests of the developed miniature air bearing sliding stage are carried out to show its feasibility.

Abstract: The development of a three-dimensional surface profilometer using digital fringe projection technology and phase-shifting principle is presented. Accurate and high-speed three-dimensional profile measurement plays a key role in determining the success of process automation and productivity. By integrating a digital micromirror device (DMD) with the developed system, exclusive advantages in projecting flexible and accurate structured-light patterns onto the object surface to be measured can be obtained. Furthermore, the developed system consists of a specially designed micro-projecting optical unit for generating flexibly optimal structured-light to accommodate requirements in terms of measurement range and resolution. Its wide angle image detection design also improves measurement resolution for detecting deformed fringe patterns. This resolves the problem in capturing effective deformed fringe patterns for phase shifting, especially when a coaxial optical layout of a stereomicroscope is employed. Experimental results verified that the maximum error was within a reasonable range of the measured depth. The developed system and the method can provide a useful and effective tool for 3D full field surface measurement ranging from µm up to cm scale.