Zhang Qingchuan

Uncooled Optically Readable Bimaterial Micro-Cantilever Infrared Imaging Device

We develop an uncooled infrared imaging device that contains a SiN–Au bimaterial micro-cantilever arrays detector and an optical read-out section. The detector converts the incident infrared radiation to the cantilever inclination angles, and the optical read-out section converts these angles directly to a visible image through an optical filtering operation to the spectra of the cantilever arrays with a knife-edge filter. The present results with the 140×98 cantilever arrays and the 8-bit A/D quantizer suggest that the objects at the temperature of 250°C at the distance as far as 1 m can be detected and the noise-equivalent temperature difference (NETD) of the device is about 10 K. The further improvement of NETD is expected to approach about 14 mK with the optimized cantilever design and 12-bit quantizer.

Analysis of Optical Readout Sensitivity for Uncooled Infrared Detector

An optical readout uncooled infrared detector, employing a substrate-free focal plane array with pitch size 60 ?m, is established. The reflector deformation induced by the stress mismatching of the bi-layer structure is discussed and, in turn, a universal solution to determine both the optical readout sensitivity and the optimal filter position is found. By applying this solution, the optical readout sensitivity for the ideal plane reflector could theoretically increase by 80% as compared with the conventional operation, and the sensitivity loss caused by the reflector deformation can also be reduced to a reasonable level.

Electron Beam Lithographic Pixelated Micropolarizer Array for Real-Time Phase Measurement

Pixelated micropolarizer arrays (PMAs) have recently been used as key components to achieve real-time phase measurement. PMA fabrication by electron beam lithography and inductively coupled plasma-reactive ion etching is proposed in this work. A 320 × 240 aluminum PMA with 7.4 μm pitch is successfully fabricated by the proposed technique. The period of the grating is 140 nm, and the polarization directions of each of the 2 × 2 units are 0°, 45°, 90°, and 135°. The scanning electron microscopy and optical microscopy results show that the PMA has a good surface characteristic and polarization performances. When the PMA is applied to phase-shifting interferometry, four fringe patterns of different polarization directions are obtained from only one single frame image, and then the object wave phase is calculated in real time.

Deformation measurements of three types of Portevin–Le Chatelier bands

In this paper a technique based on high-speed digital photography and the digital speckle correlation (DSC) method is used for the quantitative measurement of the displacement and strain fields of various Portevin-Le Chatelier (PLC) bands (types A, B, and C). The experimental results clearly show the nucleation process of a type-B band and the propagation of a type-A band. The results also reveal that there exists an elastic shrinkage deformation outside a PLC band during a large avalanche-like deformation inside the PLC band.

Accelerating Generalized Polygon Beams and Their Propagation

Accelerating beams with intensity cusps and exotic topological properties are drawing increasing attention as they have extensive uses in many intriguing fields. We investigate the structural features of accelerating polygon beams, show their generalized mathematical form theoretically, and discuss the even-numbered polygon beams. Furthermore, we also carry out the experiment and observe the intensity evolution during their propagation.

A substrate-free optical readout focal plane array with a heat sink structure

A substrate-free optical readout focal plane array (FPA) operating in 8–12 μm with a heat sink structure (HSS) was fabricated and its performance was tested. The temperature distribution of the FPA with an HSS investigated by using a commercial FLIR IR camera shows excellent uniformity. The thermal cross-talk effect existing in traditional substrate-free FPAs was eliminated effectively. The heat sink is fabricated successfully by electroplating copper, which provides high thermal capacity and high thermal conductivity, on the frame of substrate-free FPA. The FPA was tested in the optical-readout system, the results show that the response and NETD are 13.6 grey/K (F / # = 0.8) and 588 mK, respectively.

Conformational Transition of Poly (Acrylic Acid) Detected by Microcantilever Sensing

Poly (acrylic acid) (PAA) chains are grafted on one side of a microcantilever by the self-assembled method and the deflections of the microcantilever are detected as a function of medium pH from 3 to 11. It is found that when the pH varies, the microcantilever deflects because of the changing surface stress. By analysing the electrostatic repulsive effect, the surface stress change is related to the conformation transition of PAA from a collapse state to a swelling state. This method offers the interaction information among the polymer chains during the conformational transition and affords an alternative way to study conformational change of polymers.

Effect of solute concentration on the serrated flow in solution-treated Al-4%Cu alloys

In order to compare with annealed Al–4%Cu alloys, the influence of solute concentration on the serrated flow is investigated by solution treatment. In this paper, some dynamic parameters, such as critical time and the ultimate tensile strength are obtained. Moreover, the change of the strain rate range for serrated flow in Al–4%Cu alloys prepared by annealing and quenching heat treatments is reported too. The difference between them is attributed to the increasing solute concentration in the bulk of the solution treated materials.

Real-time dynamic phase measurement based on pixelated micropolarizer array

Real-time phase-shifting interferometry based on pixelated micropolarizer array (PMA) has recently been used to achieve real-time phase measurement, and the requirement of vibration resistance is greatly reduced. In this paper, a 320×240 Aluminum PMA with 7.4 μm pitch is successfully fabricated by the electron beam lithography (EBL). The period of the grating is 140nm, and the polarization directions of each 2×2 units are 0°, 45°, 90°, and 135°. The PMA is integrated to the CCD sensor to achieve real-time phase measurement. Four fringe patterns of different polarization directions are obtained from only one single frame image by linear interpolation method, and then the object wave phase is calculated in real-time. Moreover, dynamic phase caused by temperature change is obtained in real-time, which verify the feasibility of this method in real-time dynamic phase measurement.

Research of Infrared Imaging at Atmospheric Pressure Using a Substrate-Free Focal Plane Array

An equivalent circuit model to the substrate-free focal plane array (FPA) is established. Using this fast and effective model, the performance of infrared (IR) imaging at atmospheric pressure is investigated and it is found that the substrate-free FPA has the ability of IR imaging at atmospheric pressure, whereas it has a slightly degraded noise equivalent temperature difference (NETD) as compared with IR imaging under a high vacuum. This feature is also identified experimentally by a substrate-free FPA with pixel size of 50 × 50 μm2. The NETDs are measured to be 160 mK at 10−2 Pa pressure and 1.08 K at atmospheric pressure.