Yuchi Lin

Design of High-Stability Driver for White LED

The driving technology is a very important factor influencing the output performances of white LED (WLED).This paper proposes a kind of high-stability driver for WLED based on constant-current and constant-luminance. The working characteristics of WLED and the principle of driving WLED are introduced in this paper. The newly designed driver works in a mode of constant current LDO and it is feedback controlled by the output of WLED to obtain highly stable luminance. Finally, a test circuit is set up to validate the proposed scheme and some experiments are carried out. The results show that the driving current maintains nearly constant and the luminance of WLED is of high accuracy. Keywords-white LED; driver; constant-current; constantluminance

A Novel Fiber Bragg Grating Sensor with Temperature Compensation

A novel Fiber Bragg Grating sensor with temperature compensation function was designed which can be used for structure health monitoring in harsh environment. The sensor achieved temperature compensation with a reference Fiber Bragg Grating. From the strain experiment and temperature experiment, it showed that the linear fitting degree of the strain curve and temperature curve were above 99%. And the temperature sensitivities of strain Grating and reference Grating were 11.2pm/ c o and 4.3pm/ c o , respectively. Two kinds of Fiber Bragg Grating rosettes based on the designed sensor were introduced which applied the multiplexing ability of FBG and could be used in practice. Keywords-Fiber Bragg Grating;temperature compensation;

Study on the Spatial Division Multiplexing Technique of Fiber Bragg Grating Sensors

The optical switch spatial division multiplexing sensing system is proposed by using wavelength division multiplexer and unbalanced Mach-Zehnder interferometer. Controlled by an optical switch, fiber Bragg grating sensing system based on spatial division multiplexing was achieved when a broadband source illumines FBG sensor array. With an isosceles triangle cantilever beam to realize linear tuning of Bragg wavelength of fiber grating without chirping by adjusting the deflection of the free end , the system employs an unbalanced Mach-Zehnder interferometer to translate the FBG wavelength signal related the strain into phase signal. The wavelength division multiplexer is adopt to realize the demand of the change of different fiber Bragg grating wavelength. The strain can be recovered by measuring the phase change of the signal with signal processing circuit. With the characteristic of high resolution, wide measuring range, this sensing system has the capability of measuring static strain as well as dynamic strain. Experiment demonstrated that the sensing sensitivity of this system, which was with a resolution of 20n , was 0.29°/ . Keywords-fiber Bragg grating(FBG), stain sensing, interferometric demodulation, spatial division multiplexing , phase measurement

Application of contourlet transform in infrared image denoising

Wavelet threshold denoising is widely used in the denoising of the infrared image for its simplicity and effectiveness in application. However, there has been a growing awareness to the observation that wavelets may not be the best choice for describing infrared images. This observation is due to the fact that wavelets are blind to the smoothness along the edges commonly found in images. A denoising method of infrared image based on Contourlet transform is presented in this paper. In selecting the hard threshold function to process the coefficients in the Contourlet domain, we could thereby obtain the denoised infrared image of superior quality via inverse transforming. The result of the experiment indicates that compared with the traditional algorithms of the wavelet, this method can preserve the detail and the texture of the infrared image more effectively, and has better image effect and the SNR value.

Infrared and visible image fusion algorithm based on Contourlet transform and PCNN

A new image fusion method based on Contourlet transform and an improved pulse coupled neural network (PCNN) is introduced in this paper. The input infrared and visible images are processed with Contourlet decomposition which has multi-scale and multi-directional characteristics. The PCNN algorithm deriving from the neurophysiology is optimized in order to be compatible with the image fusion strategy. Owning to the global coupling and pulse synchronization characteristic of PCNN, this new fusion strategy utilizes the global features of source images and has several advantages in comparison with the traditional methods based on the single pixel or regional features. Multiple criteria and statistical indicators regarding different aspects of image quality are presented for objective and quantitative evaluation of the fused images to understand the performance of image fusion algorithms. Experimental result shows that the new method can improve the quality of image fusion and can achieve an ideal fusing effect. The method would find its application in the aspects of optical imaging, target detection and safety monitoring, etc.

Research on CCD visual sensor-based embedded level measuring system for oil tankers

A new level measuring system for oil tankers based on machine vision is designed for realizing close-cabin operating and remote monitoring. The system adopts ARM9 S3C2240 microchip as the central processing unit. With a high-precision macro-focusing CCD sensor and an image capturing module, the system can acquire the level ruler images and process them with a series of algorithms. Pre-processing procedures to the captured ruler images, including binarizing and denoising methods, are implemented to improve the image quality. A grey level projecting program is used to extract the rectangular area containing digit characters and segment the digits into individual parts. Following judgment strategies are executed to separate the exact digit of the characters. Each character is scanned with vertical and horizontal lines at various positions. Pixel change point numbers are counted to distinguish different digit characters to proceed the recognition procedure. The scale in the viewing field can be accurately localized, so that the automatic recognition result is obtained. The experimental results for different oil levels indicate that the measuring accuracy of this system can achieve ±0.1 mm and the automatic reading time is less than 0.5 s, which shows the characteristics of high-precision and high-speed.

Research on Real-Time Vision Detection Method for Sanitary Labels

Taking diaper which is a representative production of sanitary supplies as an example, a real-time detection method for diaper label based on machine vision is developed. To identify the location of diaper surface label position rapidly, a visual inspection system platform applies to production line is built. Images are captured with high-resolution colorful CCD industrial camera and NC template matching method is adopted as the surface label detection algorithm. Meanwhile, the comparative experiments results among NC, ABS method and Moment Matching method are presented. Experimental results show that this label detection system can realize accurate identification on the condition of different light, whose recognition rate can reach up to 97% and detection algorithm is of preferable instantaneity and stability.

Comparative Analysis of Image Measurement Accuracy in High Temperature Based on Visible and Infrared Vision

Image measurement is a common and non-contact dimensional measurement method. However, because of light deflection, visible light imaging is influenced largely, which makes the measurement accuracy reduce greatly. Various factors of visual measurement in high temperature are analyzed with the application of Planck theory. Thereafter, by means of the light dispersion theory, image measurement errors of visible and infrared images in high temperature which caused by light deviation are comparatively analyzed. Imaging errors of visible and infrared images are proposed quantitatively with experiments. Experimental results indicate that, based on the same imaging resolution, the relative error value of visible light image is 3.846 times larger than infrared image in 900°C high temperature. Therefore, the infrared image measurement has higher accuracy than the visible light image measurement in high temperature circumstances.

An FPGA-based heterogeneous image fusion system design method

Taking the advantages of FPGAs low cost and compact structure, an FPGA-based heterogeneous image fusion platform is established in this study. Alteras Cyclone IV series FPGA is adopted as the core processor of the platform, and the visible light CCD camera and infrared thermal imager are used as the image-capturing device in order to obtain dualchannel heterogeneous video images. Tailor-made image fusion algorithms such as gray-scale weighted averaging, maximum selection and minimum selection methods are analyzed and compared. VHDL language and the synchronous design method are utilized to perform a reliable RTL-level description. Alteras Quartus II 9.0 software is applied to simulate and implement the algorithm modules. The contrast experiments of various fusion algorithms show that, preferably image quality of the heterogeneous image fusion can be obtained on top of the proposed system. The applied range of the different fusion algorithms is also discussed.

Coarse North-Finding Based on Tracking Inversion Points Method without Torque

Based on the principle of tracking inversion points method for north-finding, the tracking inversion points method without torque is presented with a tracking and controlling system. According to the gyroscope’s cursor signal captured in real time, the theodolite can be turned round by the electric turntable to follow the swing of the main axis of gyroscope. After simple calculating, the coarse north can be obtained. The influence of changed torque of hang spring is reduced and the measurement precision is improved. It has been proved through experiments that the coarse north can be obtained in a large range by the tracking inversion points method without torque. The experiment shows that the measurement precision is superior to 30′ and it costs no more than 7minutes to obtain the coarse north-finding.