Key Engineering Materials Vol. 552

Abstract: The Fast-Tool-Servo (FTS) is widely used for micro-structure manufacturing especially for micro optical lens. The working principle of FTS presented by Qiang Liu et.al is that, a voice coil motor and a piezoelectric（PZT） actuator are used as the driving elements, and two flexure hinges are developed as the guide mechanisms. However, vertical displacement jump happens when the flexure hinges are driven by a voice coil motor or a piezoelectric actuator. In this paper, a new amplified structure is presented, allowing the horizontal motion while reducing the vertical displacement jump. The working principle is that, the piezoelectric actuator is applied to a beam which has two flexure hinges, one is linked to the frame, and the other is linked to a tool holder which is situated through two parallel membranes. When the piezoelectric actuator deforms, the beam will rotate around the frame, while the displacement is amplified at the other end, causing the tool holder’s motion and the membranes are forced to bend, while the vertical motion is restrained by the membranes. As a result, the presented membrane based flexure structure is able to amplify the motion of the piezoelectric actuator. In addition, the vibration frequency of the membrane is easy to be adjusted by the preloaded force. It is important to know when the FTS is working at different frequency. The performance of the presented structure is analyzed by structural dynamics coupled with piezoelectric, and the parameters of the structure are optimized to remain linear relation between the tool holder and the piezoelectric actuator, while the vertical displacement jump is much smaller than the structure presented in reference.

Abstract: Spatial stability is an important property of a laser beam for a laser system. Because four-quadrant detector has more high damage threshold than CCD, it can be applied in a high laser system to monitor the direction of laser beam. In this article, the four-quadrant detector as pointing monitor device is used for a 532nm semiconductor laser, which can obtain the center position of laser spot quickly. In the experiment, the amount of shift and jitter for laser beam is measured at first. Next step is combining rotating stage and lens to measure the alignment error for three angles. The results show that the top amount of shift and jitter is 3.6″ and the average of combined pointing error is around 6″. The data can support the spatial beam pointing stability system which needs feedback system with fast steering mirrors.

Abstract: This paper deigns a new ROC measurement system for radius of curvature of spherical surface measurement base on interferometry. The ROC measurement system is designed compactly and continently to use. The ROC measurement range is up to 2000mm, and DIA of the spherical surface is range from 100mm to 300mm. We analyze the uncertainty sources of the ROC measurement system results and calculate combined standard uncertainty. Giving out the experiment results, the relative uncertainty is less than 6.9ppm (ROC~1500mm). By discussing the method, we can improve and reduce the uncertainty of results of ROC measurement system.

Abstract: Definition evaluation function of the defocused image is key to realize automatic focusing. Sensitivity of the definition evaluation function can directly affect detection accuracy of the test equipments. By analyzing and summarizing the definition evaluation functions which are commonly used currently, we will present a new image definition evaluation function based on wavelet transform in this paper. On the basis of theoretical analysis, we also establish and analyze the mathematical model of evaluation function, and make experiment and simulation with the series of images collected by the video image acquisition system. Compared with the traditional definition evaluation function, the definition evaluation function of defocused image defined by this algorithm is more sensitive to fuzzy degree of image and more consistent with human subjective vision.

Abstract: For tFor t For tFor the imaging advantages of aspheric optical component, it has been widely used in the aviation, aerospace, defense and civilian high-technology. Aspherical surface shape test is a key factor restricted aspheric processing and a complex sophisticated testing techniques. The well known measurement methods are faulty. Each method has advantages and disadvantages; many methods cannot be used for online testing. In this paper，the geometric principle of a swing-arm profilometer as a novel method to measure aspherics is introduced．The deviation between the actual and the ideal of aspherical surface shape is confirmed by the high-precision measurement for the vertical height with a specific path on the aspherical optical surfaces. By adjusting the location of measuring devices to maintain the distance of rotation center to the center of workpiece equal to the length of swing-arm,we can achieve the measurement for the workpiece of different machining tool. The measurement system mainly consists of the lifting and landing system of the high-precision axis,the high-precision level turntable rotary table, the high rigidity measuring arm and the high precision measurement sensors. And the follow-up data processing puts forward a number of error correction models at the same time. The advantages of the measurement method are that the measurement sports is only a simple turning motion .It will be helpful to reduce measurement errors and improve the efficiency of measurement.

Abstract: Twice-image method based on the Newton's formula, is used to measure the focal plane of the microlens array. The focal plane of the microlens array is measured by using the transmitted optical path, magnification, and high definition of the CCD camera of a metallographic microscope. Both the experimental setup and procedures are described in detail in the paper. Experimental results are also discussed thoroughly as well. It is a simple, convenient and economical method for checking the focal plane of a microlens array efficiently.

Abstract: A new measuring method of track irregularity for high-speed railway is proposed by using dual-frequency laser interference technique. The linear deviation between the phase-locked gauging head and the center line of the railway route can be calculated by comparing the phase difference variation of the laser beat signal in the test ray path and the reference ray path when the portable track inspection car is moving forward along the track. While we use laser ranging technique to measure gauge, after processing data, the static irregularity of track will be acquired by changing straightness deviation of phase-locked gauging head into straightness deviation of left-right two tracks. The method is different from the existing techniques for detecting high-speed railway irregularity, such as the inertial reference method, the measuring method of chord and the method of laser alignment; it utilized the accuracy of the time to accomplish the high-precision measurement of the space and achieved innovation in theory.

Abstract: With the development of science and technology, the application to modern warfare of weapon systems identified with modules of laser ranging, infrared imaging and low-light viewing are more and more frequently nowadays. Their combat accuracy depends much on the parallelism of gun line and laser axis. In consequence, it is of great significance to detect and correct the non-parallelism for improving the aim and combat accuracy. The axis parallelism detection exists in not only the production and assembly, but also the adjustment in the combat clearance or field environment. It is the basic to ensure these multi-axis systems work efficiently, and is an essential link of system installation, use and maintenance. There are laboratory method and field detection method to detect the non-parallelism of gun line and laser axis. Now the laboratory method is more mature. At the same time, as it is difficult to avoid vibrations, temperature differences and harsh environment in the field detection, the axis parallelism detection in field environment is an important research direction. One of commonly used methodsaxis parallelism detection needs complex operation, specific environment, and using target, and could not realize the axis parallelism on-line detection in the fighting or running environment. To solve problems above, a multi-optic axis detecting system using a novel image processing way without target is presented in this paper. By using the method of digital image processing, it can test the non-parallelism of gun line and laser axis accurately, as the standard and correction parameter of the weapon systems axis parallelism. The system has advantages in small size, portable type, high precision, and no target. It is suitable for field detection. This paper introduces the operating principle of the system of axis parallelism detection based on digital Image without target, and focuses on the principle, realization method and experimental results of the parallelism detection of gun axis and the system of axis parallelism detection based on digital image without target. Corresponding author: Xia Wang, Associate Professor, Research interests in terms of photoelectric detection, infrared imaging system etc., TEL: 13811670583; Email: angelniuniu@bit.edu.cn

Abstract: For EMBCCD (Electron Multiplying Back Illuminated CCD) which is low light level imaging device, temperature has an important effect on the imaging performance. When EMBCCD enhances signal, it also amplifies the noise of the dark current. The most effective means of cooling chip is to reduce the noise of the dark current. When the EMBCCD is in the stable environment in low temperature, the signal to noise ratio can be improved. For this problem, the article describes the PID (Proportion Integration Differentiation) control algorithm. The unit step response curve for the controlled object is obtained by absolute refrigeration. As the system unit step response curve meets the requirements of the S-shaped curve, the Ziegler-Nichols method is used and the parameter is obtained from the S-shaped curve. The deviation between the actual temperature and set temperature values according to the proportional, integral and differential linear combination to form the control volume, incremental PID control algorithm. Put the parameters into the algorithm to control the refrigeration temperature. After that, the initial control curve is gotten. By repeated testing, we can get more appropriate parameters, and the temperature can be controlled at the target temperature. And the temperature curve is in the flat, almost with no fluctuation. The corresponding PID parameters and processing strategies are gotten from the debugging process. At last, calculate PID parameters and processing strategies, and implement the PID algorithm, as well as the numerical quantification of the specific applications the basic method are obtained. The experimental results show that the algorithm can make the temperature at 10.5°Cwith error0.5°C.

Abstract: Based on the deflection effect resulted from deformation, a new experiment device for measuring the jet impact force of laser cavity is developed. The device has been used in experiment and the typical signal of jet impact force was obtained. The variational characteristic of the force with time was given. The result shows that during the experiment the target material sustains three forces. In order of time, the first force is the laser ablation force, and the other two forces are jet impact forces. The first jet impact force is greater than the ablation force and the second jet impact force is smaller than the first jet impact force.