Ruixia Zhang

Partially light-controlled imaging system based on High Temperature Poly-Silicon Thin Film Transistor-Liquid Crystal Display.

A partially light-controlled imaging system is proposed as a novel device. It is used to improve the imaging quality at the illumination of 1.979 x 10(5)lx by means of mitigating image contrast. It consists of a High Temperature Poly-Silicon Thin Film Transistor-Liquid Crystal Display (HTPS TFT-LCD), which is set between the lens and CCD and is coupled with CCD by the optical fiber taper. The transmittance of pixelated LCD can be controlled by Field-Programmable Gate Array to realize the partially light-controlled and thus dynamic range of the imaging system can be extended. Samples of indoor objects and outdoor license plate are photographed by the prototype imaging system under strong light. The imaging results of this novel system are satisfactory with better restored details, compared with the photos taken by normal CCD camera (WAT-231S2) which uses aperture and shutter to control the overall light intensity.

Modulation transfer function of partial gating detector by liquid crystal auto-controlling light intensity

Based on the electro-optical properties of liquid crystal, we have designed a novel partial gating detector. Liquid crystal can be taken to change its own transmission according to the light intensity outside. Every single pixel of the image is real-time modulated by liquid crystal, thus the strong light is weakened and low light goes through the detector normally .The purpose of partial-gating strong light (>105lx) can be achieved by this detector. The modulation transfer function (MTF) equations of the main optical sub-systems are calculated in this paper, they are liquid crystal panels, linear fiber panel and CCD array detector. According to the relevant size, the MTF value of this system is fitted out. The result is MTF= 0.518 at Nyquist frequency.

Circuit design of partial gating image based on Cyclone II and HTPS

In order to enhance the dynamic range of digital imaging system, we have brought forward processing image by the Cyclone II chip and controlling HTPSs high-density liquid crystal unit. The system in this paper proposed a kind of low cost solution, the luminous intensity entering each pixel of CCD can be adjusted directly accurately. Meanwhile, the attenuation luminance coefficients set by system algorithm and precision parameters can be adjusted artificially on the physical level to satisfy different needs. It is proving that the function of partial gating image is realized by the image processing experiment in which the details of the final image are more obvious and clear than the original. Then the system latitude problem is solved fundamentally. The image of partial gating is obtained through the experiment, and then the anticipated goal has achieved successfully.

Study of the precision of upper atmospheric wind field measurement

The passive optical methods to observe the earthly upper atmospheric wind field by satellite remote sensing is to measure the parameters including atmospheric wind velocities, temperature, pressure and volume emission rates of airglow (aurora). WINDII is the first image interferometer for upper atmospheric wind measurement in 1991 made by Canada and France loaded on NASAs UARS. The precision of wind speed is 10m/s for WINDII and its temperature precision is 10K. The second wind measurement instrument of SWIFT is launched at 2011 based on the same principle as WINDII. SWIFTs wind speed precision is 3m/s, and its temperature precision is 2K. According to the development of the photoelectron technology and CCD, the wind fields detected precision is enhanced continuously. In this paper, the theory of detected precision of wind speed and temperature is analyzed firstly; the factors between the higher precision of wind field and CCD detector parameter are made sure. And then the precision equation is deduced. The wind speed and temperature precision expression includes of optical path difference (OPD), phase, aurora wavelength, visibility, CCDs responsibility, signal-to-noise, view of field (VOF) etc. The precision of 1m/s wind speed and 1K temperature need fixed OPD 24.28cm with O+ 732.0nm aurora. This research can provide the theory for advance upper atmospheric wind field detecting precision.

Study of liquid crystal based on auto-controlling light intensity

A liquid crystal panel module coupled in the image intensifier which has been coupled the magnetic mirror has been proposed. The normal imaging under strong light and the part gating of light intensity control can be achieved by changing the transmittance of these pixel points which is changed by the voltage imposed on pixel points. Influence of the response time and transmittance of the liquid crystal to the entire system have been researched, that liquid crystal can achieve part gating function has been confirmed through experiments. Liquid crystal display module (LCP)s response time is 22ms by using the 650nm, 4mw SZ-04 laser and the transmittance of LCP ranges from 1.28 to 25.60%.It has been proved that the liquid crystal selected in this article fit for the entire LCP. Photography effect graphs achieved by part gating of light intensity have been got.